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  • Column liquid chromatography  (114)
  • hypertension
  • Springer  (153)
  • Annual Reviews
  • Blackwell Publishing Ltd
  • 2005-2009
  • 1990-1994  (99)
  • 1980-1984  (54)
  • 1955-1959
  • 2009
  • 1991  (99)
  • 1984  (54)
Collection
Keywords
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Years
  • 2005-2009
  • 1990-1994  (99)
  • 1980-1984  (54)
  • 1955-1959
Year
  • 1
    ISSN: 1432-1041
    Keywords: Atenolol ; hypertension ; ß-adrenoceptor blockade ; blood pressure ; heart rate ; ambulatory ; circadian rhythm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
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  • 2
    ISSN: 1432-1041
    Keywords: Insulin secretion ; Nifedipine ; non insulin-dependent-diabetes mellitus- ; hyperglycaemia ; plasma insulin ; hypertension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The effect of 7-days of nifedipine treatment on insulin secretion has been analyzed in hypertensive patients with non-insulin-dependent mellitus (NIDDM). Pancreatic β-cell function was assessed as insulin release following stimulation with arginine after potentiation by hyperglycaemia. Two groups of 5 patients with NIDDM (fasting blood glucose 139.2 mg·dl−1), on the same controlled diet, were compared; one was treated with nifedipine 30 mg per d and the other was the control. The mean blood pressure in the nifedipine group decreased (110 vs 102 mm Hg). Fasting blood glucose and basal plasma insulin were not affected by nifedipine. The acute insulin response (AIR) to 5 g arginine after potentiation by hyperglycaemia (clamped at 240 and 350 mg/dl for 30 min) was significantly (P〈0.05) decreased, as well as the potentiation slope (line relating AIR and plasma glucose level) in those patients, and were unchanged in the control group. Thus, nifedipine may impair insulin secretion at high glucose levels in patients with NiDDM.
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  • 3
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    European journal of clinical pharmacology 40 (1991), S. 131-134 
    ISSN: 1432-1041
    Keywords: trimazosin ; hypertension ; alpha1-adrenoceptor blocker ; essential ; exercise ; extracellular fluid volume ; haemodynamics ; plasma volume ; side effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The long-term haemodynamic effect of sustained-release trimazosin (mean daily dose 418 mg) at rest and during exercise has been examined in 14 male patients (age 30–61 y) with previously untreated mild or moderate essential hypertension. Cardiac output (dye dilution), heart rate and intra-arterial blood pressure were measured supine and sitting at rest, and during bicycle exercise. After 11 months of trimazosin treatment the mean casual blood pressure was reduced from 165/106 mm Hg to 147/92 mm Hg. The intra-arterial systolic and diastolic pressure was reduced by 3–7% at rest and during 50, 100 and 150 W exercise. Total peripheral resistance was reduced by 8–14% and cardiac output was slightly higher (2–8%) in all situations. Stroke volume and heart rate remained unchanged, as did body fluid volumes (isotope dilution) and body weight. Side effects were minor and transient. Thus, the haemodynamic responses to trimazosin are similar to but weaker than those of other alpha1-adrenoceptor blockers. The efficacy of the sustained-release formulation of trimazosin was low and daily doses above 600 mg are likely to be needed by many patients.
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  • 4
    ISSN: 1432-1041
    Keywords: Fibrinolysis ; hypertension ; atenolol ; doxazosin ; tissue plasminogen activator ; plasminogen activator inhibitor ; cholesterol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Disturbances in the fibrinolytic system have been associated with cardiovascular disease and its risk factors. In the present study the effects of an alpha1-adrenoceptor inhibitor (doxazosin) and a selective beta-adrenoceptor blocker (atenolol) on the fibrinolytic system have been evaluated. Eighty four subjects with previously untreated mild to moderate hypertension and elevated serum cholesterol were randomized to receive atenolol or doxazosin in a double-blind study over 6 months. Tissue plasminogen activator(tPA) and plasminogen activator inhibitor (PAI-1) were measured in citrated plasma samples before and after venous occlusion before and at the end of the study period. tPA activity after venous occlusion and tPA capacity were significantly increased after doxazosin as compared to pretreatment values. The fibrinolytic variables did not change in the atenolol group. Thus, doxazosin but not atenolol, improved the activity of the fibrinolytic system in patients with hypertension and an elevated serum cholesterol level. This effect of doxazosin warrants consideration when selecting a first-line antihypertensive drug.
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  • 5
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    European journal of clinical pharmacology 26 (1984), S. 309-313 
    ISSN: 1432-1041
    Keywords: clonidine ; hypertension ; therapeutic window ; steady state concentration ; pharmacokinetics ; cardiovascular effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Clonidine was given orally as monotherapy in increasing daily doses from 3.1 to 25.7 µg/kg to patients with essential hypertension (n=6). When a steady state concentration in plasma was reached at each dose level, the blood pressure (BP) and heart rate were measured during a dosage interval. Effect time — plasma concentration data were submitted to nonlinear regression analysis, which showed that the observed BP effects could be dissociated into depressor and pressor components. A window for the antihypertensive effect was established. At a plasma clonidine concentration of 0.65±0.07 ng/ml 50% of the maximal depressor effect was found, and it was only separated by a factor of 2 from the half maximal pure pressor concentration in plasma. No relationship between the change in heart rate and the plasma clonidine was observed. The findings strengthen the importance of close monitoring of clonidine therapy.
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  • 6
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    European journal of clinical pharmacology 26 (1984), S. 331-334 
    ISSN: 1432-1041
    Keywords: metoprolol ; oxprenolol ; hypertension ; beta-blockers ; HDL-cholesterol ; intrinsic sympathomimetic activity ; cardioselectivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The aim of the present study was to evaluate whether a reduction in HDL-cholesterol is peculiar to non cardioselective beta blockers or whether it is also produced by cardioselective beta1-blockers. 16 patients with primary arterial hypertension on a balanced isocaloric diet were given oxprenolol 120 to 240 mg/day or metoprolol 100 to 200 mg/day in a random cross-over study. No significant change was observed after either treatment in fasting blood glucose, serum total cholesterol and triglycerides. HDL-cholesterol concentration was significantly decreased on metoprolol, from 41 to 36 mg/dl (p〈0.05), while oxprenolol did not affect it at all. The difference might depend on intrinsic sympathomimetic activity which is possessed by oxprenolol and which metoprolol lacks.
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  • 7
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    European journal of clinical pharmacology 26 (1984), S. 549-553 
    ISSN: 1432-1041
    Keywords: pafenolol ; hypertension ; antihypertensive therapy ; beta1-blocking agent ; exercise tests ; plasma levels
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Pafenolol, a new selective adrenergic beta1-blocking agent, has been tested for the first time in 6 hypertensive patients. After single oral doses of pafenolol 25 to 100 mg, there was a marked reduction in heart rate and systolic blood pressure during exercise tests. These effects were dose dependent. A significant positive correlation was found between the reduction in heart rate during exercise and the plasma level of pafenolol 5 hours after drug intake (correlation coefficient r=0.94). Side effects were mild and seemed to be dose dependent. It is concluded that this new beta1-blocking agent was effective in reducing blood pressure and was well tolerated.
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  • 8
    ISSN: 1432-1041
    Keywords: etozolin ; ozolinone ; furosemide ; hypertension ; renin ; catecholamines ; chronic renal failure ; steady state kinetics ; plasma levels
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The effect on urinary electrolyte excretion, renin release and plasma norepinephrine of single oral doses of 400 mg etozolin (E) and of 40 mg furosemide (F) were studied in hypertensive patients with normal (n=6) and impaired kidney function (n=6). E caused a marked saluresis up to 24 hours, showing its long duration of action. F, however, displayed a brief, brisk peak diuresis, followed by a rebound from the 4th to the 24th hours. The brisk peak diuresis induced by F was associated with pronounced release of renin, almost twice that induced by E. In chronic renal failure the renin release in relation to the magnitude of the diuresis was increased, i.e. the sensitivity of these patients to changes in water homeostasis was increased. E and F stimulated the sympathetic system to roughly the same extent. Patients with essential hypertension had higher plasma levels of norepinephrine than hypertensive patients with chronic renal failure. In addition, hypertensive patients with normal renal function (n=4) and varying degrees of renal impairment (n=11) were also given 400 mg daily for 2 weeks. Effects on blood pressure and electrolyte homeostasis were monitored, as well as the plasma kinetics of metabolite I, ozolinone. At the end of the 2 week treatment E had significantly lowered systolic (−12 mm Hg) and diastolic (−9 mm Hg) blood pressure, and had produced a significant loss of body weight, without altering plasma electrolytes or blood chemistry. There was no accumulation of the effective metabolite ozolinone under conditions of severe impairment of kidney function. It is concluded that E can effectively control high blood pressure in patients with normal and impaired kidney function. Its effective metabolite ozolinone did not accumulate in chronic renal failure.
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  • 9
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    European journal of clinical pharmacology 27 (1984), S. 397-405 
    ISSN: 1432-1041
    Keywords: indapamide ; hypertension ; cardiovascular reflexes ; diuretic effect ; blood pressure variability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Nine elderly and 11 young hypertensives underwent continuous ambulatory monitoring of blood pressure (BP), assessment of cardiovascular reflexes and M-mode echocardiography as hospital in-patients prior to treatment with once-daily indapamide (2.5 mg). They were followed as out-patients for 4 months during which time casual BP was measured at monthly intervals. The patients were then readmitted to hospital and studied using the same protocol under similar standardised conditions. The results showed that indapamide reduced casual and ambulatory BP in both young and elderly although the most marked effect was seen on systolic BP. Assessment of cardiovascular reflexes indicates that at least part of the hypotensive action of indapamide is due to a diuretic effect. Treatment with indapamide has comparable results on both young and elderly.
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  • 10
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    European journal of clinical pharmacology 26 (1984), S. 315-323 
    ISSN: 1432-1041
    Keywords: captopril ; hypertension ; glomerular filtration ; para-aminohippuric acid ; renal function ; severe drug reaction ; nephrotic syndrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The effect of captopril up to 450 mg/day on blood pressure and renal function were investigated during sustained treatment of 10 patients whose severe hypertension had not responded to previous therapy. All the patients were kept on diuretics and most of them on β-blockers, too. A control determination of glomerular filtration rate (GFR) and para-aminohippuric acid clearance (CPAH) was performed during the prior treatment. The effect of the addition (or substitution) of captopril were assessed after an average of 25 days (short-term) and 26 weeks (long-term). Short-term treatment produced a 15.5% decrease in mean blood pressure and interindividually variable effects on renal function. On average GFR was somewhat lower and CPAH slightly higher than the control values (not significant). This pattern is quite similar to the effects of most other antihypertensive drugs. On long-term therapy GFR rose by a mean of 9% (NS) and CPAH by 17% (p〈0.02). However, in a patient who developed a captopril-induced nephrotic syndrome, GFR dropped to 56% and CPAH to 50% of the control values. In another patient a transient rise in serum creatinine accompanied a severe drug reaction.
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  • 11
    ISSN: 1432-1041
    Keywords: Captopril ; Diabetes ; nephropathy ; hypertension ; glucose tolerance ; plasma lipids ; blood pressure ; long-term treatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The effects of the angiotensin converting enzyme inhibitor captopril on blood pressure, proteinuria, creatinine clearance and metabolic control in diabetic nephropathy have been evaluated. Captopril 144 mg per day was given to 8 longstanding, insulin-dependent, diabetic females with nephropathy. The blood pressure was significantly reduced (systolic 45.4, diastolic pressure 30.6 and mean arterial pressure 33.8 mm Hg after 24 weeks of treatment). Plasma renin activity rose significantly from a basal value of 1.60 to 6.71 ng·ml−1·h−1, and so did serum potassium (from 4.57 to 4.83 mEq·l−1). Serum aldosterone fell from 161 to 70.9 pgm·ml−1 and from 27.3 to 15.3 μg·24 h−1 in plasma and urine, respectively, after 6 months on captopril therapy. Urinary protein excretion was decreased by about 48% and creatinine clearance remained unchanged throughout the study. Plasma triglycerides and cholesterol also remained unchanged, and glycosylated haemoglobin was significantly reduced from 13.8 to 10.2% after captopril. The results suggest that captopril is a useful drug to treat hypertension in patients suffering from diabetic nephropathy, as the decline in kidney function can be reduced without impairing glucose tolerance or the lipid profile.
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  • 12
    ISSN: 1432-1041
    Keywords: beta-blocking drugs ; insulin sensitivity ; pancreatic beta-cell function ; hypertension ; propranolol ; atenolol ; insulin secretion ; plasma GIP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The effects of two beta-blocking drugs on endogenous insulin secretion and insulin sensitivity were investigated in a double blind cross-over study in 13 hypertensive patients. The patients were randomly allocated to each of three 2-week treatment periods with propranolol 80 mg b.i.d., atenolol 50 mg b.i.d. and placebo b.i.d. Endogenous insulin secretion was assessed by measuring serum insulin and C-peptide before and 6 min after iv administration of glucagon; insulin sensitivity was determined by measuring insulin binding to erythrocytes, and as the glucose disappearance rate (KITT) after i.v. insulin. Fasting concentrations of serum free fatty acids (S-FFA) and plasma gastric inhibitory polypeptide (P-GIP) were also recorded during the three study periods. Both propranolol and atenolol reduced blood pressure, heart rate and S-FFA concentrations compared to placebo, and all patients showed measurable plasma concentrations of propranolol and atenolol. The results can be considered representative, therefore, of clinical beta-blockade. The two drugs did not significantly influence the fasting blood glucose level. There was an increase in fasting and glucagon-stimulated serum C-peptide concentration during propranolol therapy compared with placebo (p=0.037 and p=0.030, respectively), although this was not reflected by a significant change in serum insulin. Propranolol and atenolol did not significantly influence insulin binding to erythrocytes, but they clearly reduced the glucose disappearance rate KITT was compared to placebo (p=0.0036 and p=0.0003, respectively). The findings support the view that beta-blocking drugs can influence glucose metabolism by mechanisms other than inhibition of endogenous insulin secretion.
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  • 13
    ISSN: 1432-1041
    Keywords: acetylator phenotype ; hydralazine response ; hypertension ; blood pressure control ; lupus syndrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The role of acetylator phenotype in determining the response to hydralazine when it was added to diuretic and β-blocker at doses not exceeding 200 mg daily was examined in 57 hypertensive patients. 81% of rapid acetylators needed 200 mg hydralazine daily compared to 38% of slow acetylators (p〈0.01). Despite higher doses of hydralazine the blood pressure was controlled in only 27% of rapid acetylators compared to 65% of slow acetylators (p〈0.02). The relation of acetylator phenotype to blood pressure response was statistically independent of initial blood pressure, age, sex, body weight and serum creatinine (p〈0.005). Current recommendations on hydralazine dosage are unsatisfactory for the 40% of hypertensive patients who are rapid acetylators. We suggest measurement of the acetylator phenotype in patients who respond incompletely to 200 mg hydralazine daily. About 70% of these patients will be rapid acetylators in whom the dose of hydralazine can be increased safely.
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  • 14
    ISSN: 1432-1041
    Keywords: Tobanum® ; beta-blocker ; chloranolol ; hypertension ; angina pectoris ; arrhythmia ; detection methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The incidence of side-effects on administration of chloranolol (Tobanum®), a beta-adrenergic receptor blocking drug, to 2066 patients with hypertension, angina pectoris or arrhythmias was measured by three different methods. In 600 patients in an efficacy trial (Group 1) both spontaneously reported complaints and objective signs were tabulated. A side effect — directed method, utilising a questionnaire containing a list of possible side-effects was also used, with the questionnaire being completed by the physician. 35 questions referred to anticipated and other side-effects. The trial was performed in two groups: in 537 patients a placebo was also given (Group 2), and in another set of 929 patients (Group 3) the questionnaire inquiry was performed uncontrolled, without placebo. All three groups were comparable in their distribution of sexes, ages and diagnoses, the mean daily dose of chloranolol its use alone or in combination, and in a similar duration of treatment. 55% of all patients received chloranolol therapy for a period of more than 3 months. The ratio of in- and outpatients was 1:5. The side-effect incidence was independent of the age and sex of the patients and of the dose of chloranolol. The incidence was also unaffected whether chloranolol was used alone or in combination. The number of side-effects differed markedly between the three groups, their ratio was 1:10:24 in Groups 1, 2 and 3. Two-thirds of the side-effects subsided spontaneously within 1 month of their onset. The duration of the side-effects varied according to their character: cardiorespiratory side-effects were of the shortest duration and those affecting the central nervous system were the most enduring. The appreciable differences in incidence could be attributed to the methods of collection of the data. It has been stated that placebo controlled trials using a detailed questionnaire are the most suitable for estimating the incidence of side-effects; recording side-effects spontaneously reported by patients are insufficiently sensitive, and uncontrolled trials using a questionnaire have been shown to be too sensitive. The revealed incidence of side effects leading to interruption of treatment is less affected by the method chosen. In 100 patients (4.8%) therapy had to be suspended because of the side-effects of chloranolol (Group 1: 1%, Group 2: 6.20%, Group 3: 6.6%). Comparison of the incidence of cessation of therapy due to side-effects did not show an appreciable difference between the various beta-adrenergic receptor blocking agents, including chloranolol.
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  • 15
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    European journal of clinical pharmacology 26 (1984), S. 1-6 
    ISSN: 1432-1041
    Keywords: hypertension ; beta-blockers ; propranolol ; metoprolol ; labetalol ; exercise ; heart rate ; blood pressure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In a double blind, within patient investigation of twenty-four patients (nineteen males and five females) with a mean age of 46.3 years (SD 10.9 years) with mild to moderate essential hypertension a comparison between equipotent beta-blocking doses of propranolol, metoprolol and labetalol was carried out. Blood pressure and pulse rate were measured in lying, sitting and standing positions and before, during and after isometric and dynamic exercise. Peak expiratory flow was recorded before and during dynamic exercise. All the active treatments were better than placebo in reducing blood pressure and heart rate. Comparing the effects of treatment, labetalol lowered sitting diastolic pressure significantly more than propranolol and standing diastolic pressure than both propranolol and metoprolol. Metoprolol and propranolol were more effective in reducing heart rate. Propranolol significantly reduced peak flow rate compared to labetalol. During the exercise, both isometric and dynamic, the heart rate and the blood pressure, both systolic and diastolic, of the treated patients were lower than those on placebo. There was little difference between the drugs in the influence on blood pressure, but metoprolol and propranolol were significantly more effective than labetalol in lowering the heart rate.
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  • 16
    ISSN: 1432-1041
    Keywords: alpha-methyldopa ; propranolol ; hypertension ; side effects ; blood pressure control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A multicentre study of 6–10 weeks duration was performed in 60 ambulant hypertensive patients aged over 60 years to compare the efficacy of methyldopa and propranolol with particular reference to the occurrence of cold extremities and sleep disturbances. Blood pressure was effectively controlled by both drugs being reduced from a mean of 180/108 mmHg to 161/93 with methyldopa and 180/108 to 162/94 with propranolol. More patients treated with methyldopa (74%) achieved the target diastolic blood pressure of 95 mmHg or below compared with those treated with propranolol (58%). Side effects were more frequent in the propranolol group necessitating the withdrawal of four patients from the study. Only one patient on methyldopa was withdrawn. The incidence of cold extremities was significantly greater with propranolol. The occurrence of sleep disturbances was similar in both groups. In this group of elderly patients methyldopa was better tolerated than propranolol.
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  • 17
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    European journal of clinical pharmacology 26 (1984), S. 543-547 
    ISSN: 1432-1041
    Keywords: indapamide ; hypertension ; glomerular filtration ; arginine vasopressin ; free water clearance ; blood pressure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Renal plasma flow (RPF), glomerular filtration rate (GFR), arginine vasopressin in plasma (AVP), free water clearance ( $${\text{C}}_{{\text{H}}_{\text{2}} {\text{O}}}$$ ) and blood pressure (BP) were determined in 11 patients with essential hypertension at the end of 3 consecutive periods of observation each of 6 of weeks duration; indapamide 2.5 mg daily was given in period 2 and placebo in periods 1 and 3. RPF and GFR were reduced by 9% and BP by 9%/14% supine and 14%/12% standing during indapamide treatment. Changes in renal haemodynamics were not correlated with those in BP. AVP was not significantly altered by indapamide and was not correlated with BP. Indapamide reduced $${\text{C}}_{{\text{H}}_{\text{2}} {\text{O}}}$$ possibly due to the reduction in GFR. It is concluded that indapamide evidently induces redistribution of the cardiac output, with enhanced muscle blood flow and reduced renal perfussion, and that AVP does not seem to be involved in blood pressure regulation in mild to moderate essential hypertension under basal conditions.
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  • 18
    ISSN: 1432-1041
    Keywords: beta-blockers ; hypertension ; ISA ; CS ; cold extremities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Patients with essential hypertension were interviewed prior to entering therapeutic studies in general practice. Patients' age, sex and details of antihypertensive therapy (if any) were noted, as were their spontaneously reported symptoms. Complaints of cold extremities were highest in those taking a beta-blocker (4.1%). Those untreated or taking other therapies complained less often. Those patients taking a beta-blocker with ISA complained less often (3.1%) of cold extremities than those taking a beta-blocker without ISA (5.2%).
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  • 19
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    European journal of clinical pharmacology 27 (1984), S. 13-17 
    ISSN: 1432-1041
    Keywords: nifedipine ; hypertension ; blood pressure decrease ; drug combination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The medication of patients receiving hydralazine, captopril and minoxidil was replaced by a new galenical form, long-acting nifedipine. An additional decrease in blood pressure was observed in most of the patients. Renal function was maintained in all of them. Adverse reactions may be reduced by the use of long-acting nifedipine, which would permit a reduction in the dosage of captopril and minoxidil.
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  • 20
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    European journal of clinical pharmacology 27 (1984), S. 23-27 
    ISSN: 1432-1041
    Keywords: hypertension ; alpha2-adrenoceptors ; blood pressure ; clonidine ; guanfacine ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The time courses of the changes in plasma growth hormone and noradrenaline concentrations in response to 15 min infusions of clonidine 0.2 mgs and guanfacine 2 mgs, were studied in six normal volunteers, in a double-blind, randomised, crossover study. Plasma noradrenaline fell within 15 min of the commencement of drug administration, by 36±14% after clonidine (p〈0.05) and by 32±11% (p〈0.05) after guanfacine. Plasma growth hormone was not significantly elevated until the 30th minute to 12.0±4.7 lU/ml (p〈0.05) after clonidine and 14.7±11.5 lU/ml (p〈0.05) after guanfacine, having been undetectable prior to both drugs. The reduction in plasma noradrenaline by these α2-adrenergic agonists, prior to activation of central adrenoceptors as detected by changes in plasma growth hormone, is evidence for a peripheral component in their sympatholytic effect.
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  • 21
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    European journal of clinical pharmacology 27 (1984), S. 147-152 
    ISSN: 1432-1041
    Keywords: moxonidine ; clonidine ; hypertension ; double-blind crossover ; side-effects ; withdrawal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The antihypertensive effect of moxonidine·HCl·H2O (MOX) was compared with that of clonidine·HCl (CLON) in a randomized double-blind crossover study in 20 hypertensive outpatients (BP range 154–178/96–108 mmHg). After 2 weeks without antihypertensive medication, either MOX 0.2 mg daily or CLON 0.2 mg daily was given and the dose was titrated until the diastolic blood pressure fell below 90 mmHg. The first treatment period was continued for 2 weeks and, after crossover without a wash-out period, it was followed by the second treatment for a further 2 weeks. Within the first 4 days of administration 0.2–0.4 mg of either agent caused a significant decrease in BP (p〈0.001) from a mean of 166/100 mmHg to 149/86 mmHg after CLON (approx. −10/−14%), and 163/99 mmHg to 146/84 mmHg after MOX (approx. −10/−15%). No significant difference in the fall in BP or pulse rate was detected between the two drugs. In the mean daily dose of 0.3 mg both drugs showed the same antihypertensive activity, but on CLON a higher incidence of side effects (p=0.003) was noted, and after discontinuation of therapy a more rapid rise in BP (systolic BP p〈0.01, diastolic BP p〈0.02) was found. 17 patients on CLON complained of side effects, especially tiredness and dry mouth, whilst only 6 patients on MOX were affected (p=0.003).
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  • 22
    ISSN: 1432-1041
    Keywords: guanfacine ; hydrallazine ; hypertension ; sympathetic nervous activity ; plasma renin activity ; cardiac and systemic haemodynamics ; blood pressure ; limb blood flow ; limb vascular resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The effect of guanfacine and hydrallazine on cardiovascular haemodynamics and on sympathetic nervous activity has been studied in 16 patients with essential hypertension. Two groups of patients were investigated: in Group A guanfacine brought the blood pressure back to normal (diastolic blood pressure ⩽90 mmHg), and in Group B diastolic blood pressure was 〉 90 mmHg and required the addition of hydrallazine. Guanfacine significantly decreased heart rate, plasma renin activity and urinary excretion of noradrenaline, without altering cardiac contractility. In Group B, guanfacine 2 to 6 mg/day produced a significant decrease in blood pressure from 178.7/112.4 to 164.4/102.9 mmHg and in heart rate from 77.1 to 62.7 beats/min after 4 weeks of treatment. Guanfacine did not significantly alter preejection period, cardiac output or total peripheral resistance. Hydrallazine 50 to 300 mg/day caused a further reduction in blood pressure from 164.4/102.9 to 150.7/90.2 mmHg and an increase in heart rate from 62.7 to 72.1 beats/min. Limb blood flow was increased from 4.55 to 5.93 ml/100 g/min and limb vascular resistance was decreased from 39.55 to 23.6 mmHg 100 g·min/ml. Hydrallazine also caused a slight increase in plasma renin activity and urinary excretion of noradrenaline. It is concluded that guanfacine is a useful agent to block a hydrallazine-induced increase in sympathetic nervous activity.
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  • 23
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    European journal of clinical pharmacology 27 (1984), S. 407-414 
    ISSN: 1432-1041
    Keywords: piretanide ; hypertension ; triamterene ; double blind comparison ; potassium ; magnesium ; side-effects ; serum electrolytes ; serum parameters
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In a randomized, double blind, parallel group study in out patients with mild to moderate essential hypertension the effects of piretanide on serum electrolytes and on blood pressure were compared with those of triamterene alone and the combination piretanide + triamterene. 136 patients entered the study; 18 patients did not fulfill the inclusion criteria (RRdiast was below 95 mmHg or above 120 mmHg) at the end of the placebo period, 6 dropped out due to side effects, and 1 due to lack of efficacy. Data from 1 patient were not evaluated because the patient did not come regularly for checkups. The results for 110 patients were analyzed. Piretanide 6 mg b.d. and piretanide 6 mg + triamterene 50 mg b.d. produced a significant reduction both in supine and erect blood pressure, which was evident at 2 weeks and which increased over the ensuing 12 week trial period. A mean maximal fall of 16.5% was noted in the piretanide group and 15% in the piretanide + triamterene group. Triamterene alone (50 mg b.d.) also reduced diastolic and systolic blood pressures but the reduction was significantly less (diastolic blood pressure) than in both the piretanide groups, and it showed a more rapid return to pretreatment level during a placebo washout phase at the end of the study. A reduction in standing diastolic blood pressure below 95 mmHg was attained in 84% of patients in the piretanide group, 82% in the piretanide + triamterene group and in only 58% of the triamterene group. There were no significant changes within groups nor differences between the three groups in serum potassium or magnesium. 7 patients were withdrawn from the study because of side-effects due to too marked a clinical action (polyuria, orthostatic disorders and hypotension), one from the piretanide group, and the others in the piretanide + triamterene group. One patient in the triamterene group left the study prematurely due to the lack of effect.
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  • 24
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    European journal of clinical pharmacology 27 (1984), S. 529-534 
    ISSN: 1432-1041
    Keywords: beta-adrenoceptor blocking agents ; hypertension ; adverse reactions ; atenolol ; bopindolol ; pindolol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The efficacy of once-daily bopindolol, a nonselectiveβ-adrenoceptor blocking agent with partial agonist activity, and of pindolol and atenolol in the treatment of essential hypertension has been compared. 369 patients were investigated in a double-blind parallel-group study. The treatment period was 10 weeks. Blood pressure normalisation (diastolic BP equal to or less than 90 mmHg) was to be achieved by a stepwise increase in the dose of the test drugs, and, if required, by addition of a diuretic. Normalisation of blood pressure was achieved in 71 to 76% of the subjects, with no significant differences between bopindolol, pindolol, and atenolol. Special attention was given to evaluation of side effects by using two methods for registration of all adverse events during the study. A low incidence of drug-induced side effects was observed, with no significant difference between bopindolol, pindolol, and atenolol. There was no evidence of unsuspected adverse reactions due to bopindolol.
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  • 25
    ISSN: 1432-1041
    Keywords: Cadralazine ; hypertension ; prazosin ; metoprolol ; combined therapy ; adverse effects
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A randomized multicentre between-patient study comparison has been made of the efficacy and tolerability of cadralazine and prazosin, both administered for 6 weeks to hypertensive patients with a supine diastolic blood pressure (DBP) ≥ 95 mm Hg whilst on a beta-adrenoceptor-blocker. The doses of the beta-adrenoceptor-blocker (metoprolol SR 200 mg once daily) and cadralazine (10 mg once daily) were held constant during the study, while prazosin was individually titrated from 0.5 mg to a maximum of 2 mg tds. 108 patients (50 m and 58 f; mean age 54 y) were enrolled in 12 centres. Twelve patients withdrew due to adverse effects or poor efficacy (5 patients on prazosin and 7 on cadralazine). Both treatments induced a similar significant reduction in systolic blood pressure (SBP) and DBP, allowing normalization of BP in 58% of subjects on cadralazine and 55% on prazosin. Heart Rate (hR) increased significantly from 67 to 72 beats · min−1 in those on cadralazine and from 65 to 69 beats · min−1 on prazosin. Body weight was unchanged. Adverse effects were mild and typical of vasodilators, such as headache, flushing and dizziness. Physician evaluation of drug efficacy was not different between drugs, and cadralazine was rated better in terms of tolerability. Thus, in this multicentre study, cadralazine in the fixed dose of 10 mg once daily, as a second-step antihypertensive treatment in patients not satisfactorily controlled by a beta-adrenoceptor-blocker, was as effective and showed a similar side effect profile to prazosin given three times daily.
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  • 26
    ISSN: 1432-1041
    Keywords: hypertension ; hydrochlorothiazide ; atenolol ; side effects ; therapeutic efficacy
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary After screening a local population in the northern part of The Netherlands for hypertension, 119 patients with a diastolic pressure (DP) between 95 and 120 mmHg were randomised and treated either with 50 mg hydrochlorothiazide (n=59) or 100 mg atenolol (n=60). After 1 month of treatment 6 patients in the hydrochlorothiazide group and 24 patients in the atenolol group had reached a DP⩽90 mmHg (p〈0.001). 43 of the 50 non-responders to hydrochlorothiazide were switched to atenolol and 30 of the 35 non-responders to atenolol were changed to hydrochlorothiazide. One month after the switch 19 patients in the atenolol group and 2 patients in the hydrochlorothiazide group had reached a DP⩽90 mmHg (p〈0.001). After 6 months of treatment 32 of the 43 atenolol responders and 7 of the 8 hydrochlorothiazide responders were still receiving the same medication, as their DP was still⩽90 mmHg. Non-responders to either medication were given the combination (n=46). 21 patients now became normotensive as did a further 10 after increasing the dose of atenolol to 200 mg. Thus, in all 70 patients had a blood pressure ⩽90 mmHg after treatment for 4 months. Both drugs induced a significant reduction in the total of number of complaints after 1 month of treatment. They did not differ from each other. The reduction was seen both in responders and non-responders and persisted during treatment for 6 months. It is concluded that in terms of short-term efficacy the cardioselective, hydrophilic beta adrenoceptor-blocking drug atenolol is preferable to hydrochlorothiazide in the treatment of uncomplicated hypertension.
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  • 27
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    European journal of clinical pharmacology 26 (1984), S. 603-608 
    ISSN: 1432-1041
    Keywords: pinacidil ; hypertension ; pinacidil pyridine-N-oxide ; urinary excretion ; protein binding ; pharmacokinetics ; healthy volunteers
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Preliminary investigation in 3 healthy volunteers suggested that intravenous pinacidil in a dose of 0.2 mg/kg had a potent but well-tolerated hypotensive action in the supine position. Facial flushing, uncomfortable chest sensation and distressing postural hypotension occurred at serum concentrations above 300 ng/ml. Pinacidil, 0.2 mg/kg, was given intravenously over 4 min to 15 healthy volunteers in the supine position. Maximum fall in mean arterial pressure (MAP) was 15.7±6.0 mmHg. Maximum rise in heart rate was 23.8±6.6 beats/min. Pinacidil serum distribution half-life ( $${\text{T}}_{{\raise0.7ex\hbox{${\text{1}}$} \!\mathord{\left/ {\vphantom {{\text{1}} {{\text{2}}\alpha }}}\right.\kern-\nulldelimiterspace}\!\lower0.7ex\hbox{${{\text{2}}\alpha }$}}}$$ ) was 13.4±8.5 min and elimination half-life ( $${\text{T}}_{{\raise0.7ex\hbox{${\text{1}}$} \!\mathord{\left/ {\vphantom {{\text{1}} {{\text{2}}\beta }}}\right.\kern-\nulldelimiterspace}\!\lower0.7ex\hbox{${{\text{2}}\beta }$}}}$$ ) was 2.13±0.49 h. The apparent volume of distribution (Vdβ) was 90.3±13.21 and total body clearance was 31.1±9.61/h. Pinacidil was approximately 40% bound to plasma protein over the concentration range 40–400 ng/ml. Urinary excretion of unchanged pinacidil accounted for 5.7 ± 1.3% of the administered dose over 24 hours and urinary excretion of the major metabolite, pinacidil pyridine-N-oxide, was 31.6±9.2% of the administered dose. It was concluded that intravenous pinacidil is a potent vasodilator hypotensive compound, with a duration of action between 1.5 and 2 h.
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  • 28
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    European journal of clinical pharmacology 26 (1984), S. 661-661 
    ISSN: 1432-1041
    Keywords: endralazine ; hypertension ; elimination half-liefe ; compartment model
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    Topics: Chemistry and Pharmacology , Medicine
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  • 29
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    European journal of clinical pharmacology 27 (1984), S. 13-17 
    ISSN: 1432-1041
    Keywords: nifedipine ; hypertension ; blood pressure decrease ; drug combination
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The medication of patients receiving hydralazine, captopril and minoxidil was replaced by a new galenical form, long-acting nifedipine. An additional decrease in blood pressure was observed in most of the patients. Renal function was maintained in all of them. Adverse reactions may be reduced by the use of long-acting nifedipine, which would permit a reduction in the dosage of captopril and minoxidil.
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  • 30
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    European journal of clinical pharmacology 27 (1984), S. 23-27 
    ISSN: 1432-1041
    Keywords: hypertension ; alpha2-adrenoceptors ; blood pressure ; clonidine ; guanfacine ; healthy volunteers
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The time courses of the changes in plasma growth hormone and noradrenaline concentrations in response to 15 min infusions of clonidine 0.2 mgs and guanfacine 2 mgs, were studied in six normal volunteers, in a double-blind, randomised, crossover study. Plasma noradrenaline fell within 15 min of the commencement of drug administration, by 36±14% after clonidine (p〈0.05) and by 32±11% (p〈0.05) after guanfacine. Plasma growth hormone was not significantly elevated until the 30th minute to 12.0±4.7 lU/ml (p〈0.05) after clonidine and 14.7±11.5 lU/ml (p〈0.05) after guanfacine, having been undetectable prior to both drugs. The reduction in plasma noradrenaline by these α2-adrenergic agonists, prior to activation of central adrenoceptors as detected by changes in plasma growth hormone, is evidence for a peripheral component in their sympatholytic effect.
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  • 31
    ISSN: 1432-1041
    Keywords: beta-blockers ; hypertension ; ISA ; CS ; cold extremities
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Patients with essential hypertension were interviewed prior to entering therapeutic studies in general practice. Patients’ age, sex and details of antihypertensive therapy (if any) were noted, as were their spontaneously reported symptoms. Complaints of cold extremities were highest in those taking a beta-blocker (4.1%). Those untreated or taking other therapies complained less often. Those patients taking a beta-blocker with ISA complained less often (3.1%) of cold extremities than those taking a beta-blocker without ISA (5.2%).
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  • 32
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    European journal of clinical pharmacology 27 (1984), S. 287-289 
    ISSN: 1432-1041
    Keywords: pinacidil ; hypertension ; vasodilator ; patients ; side-effects
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A new vasodilator drug, pinacidil, N″-cyano-N-4-pyridyl-N′-1, 2,2-trimethylpropylguanidine, was studied in an open trial in 15 patients with moderate to severe hypertension. Four patients received pinacidil monotherapy, and in 11 patients it was used with a diuretic or a beta-blocker. In all but one patient normotension was achieved with a mean daily pinacidil dose of 46.7 mg b.i.d. (range 20–100 mg). Side effects were few and were action-related. There was no evidence of early toxicity. Pinacidil is a promising new antihypertensive vasodilator, which deserves further clinical evaluation.
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  • 33
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    European journal of clinical pharmacology 40 (1991), S. 67-70 
    ISSN: 1432-1041
    Keywords: Dilevalol ; oxprenolol ; hypertension ; emotional stress ; haemodynamic changes
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The effect of a single dose of 200 mg dilevalol, β-adrenoceptor blocker with additional vasodilating properties, and 200 mg oxprenolol on haemodynamic changes induced by emotional stress have been compared in 12 male young Caucasian patients with newly diagnosed labile hypertension. No difference was noted in the stress-induced increase of total peripheral resistance (TPR) following administration of the two substances (11% versus 6%). However, dilevalol revealed a vasodilating action by decreasing TPR at rest (from 1004 to 951 dyn·s·cm−5) and diastolic blood pressure (BP) (from 87 to 75 mm Hg) whereas TPR at rest remained unchanged after the intake of oxprenolol.
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  • 34
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    European journal of clinical pharmacology 40 (1991), S. 453-460 
    ISSN: 1432-1041
    Keywords: Diltiazem ; metoprolol ; quality of life ; hypertension ; multicentre study ; adverse effects
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    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary General well-being, adverse effects and antihypertensive efficacy have been investigated in a double blind, parallel-group, dose-response multicentre study of diltiazem and metoprolol monotherapy for hypertension. 128 patients with primary hypertension were included from 10 participating centres. The patients were randomized to receive oral diltiazem 120–240–360 mg/day or metoprolol 50–100–200 mg/day. Each dose was given for a 4-week period as a forced titration regime. In all 119 patients, 59 and 60, respectively, on diltiazem and metoprolol completed the study protocol. There were dose-dependent reductions in supine and standing blood pressures (BP) after both diltiazem and metoprolol therapy. In the diltiazem group, supine BP was reduced by 10 (11)/10 (6) mm Hg (SBP/DBP) at the highest dose level, and the corresponding values for the metoprolol group were 7 (16)/8 (9) mm Hg (SBP/DBP). Target pressures (DBP ≤ 90 mm Hg and/or a reduction in DBP of ≥ 10%) were reached in 63% and 48% of the patients, respectively. The incidence and severity of dose-dependent adverse effects, as evaluated by spontaneous reports or open and direct questioning, did not differ between treatments. Subjective well-being, evaluated by a self-administered questionnaire, the MSE-profile, did not differ significantly between diltiazem and metoprolol therapy. However, after an initial slight deterioration, contentment and vitality tended to improve with increasing doses of diltiazem, while a dose-related deterioration in these variables was observed on metoprolol therapy. At the highest dose levels, contentment and vitality tended to be better in the diltiazem than the metoprolol group. Thus, diltiazem and metoprolol in daily doses of 120–360 mg and 50–200 mg, respectively, produce comparable and parallel reductions in supine and standing BP. However, while subjective well-being tended to improve with increasing doses of diltiazem, there was a negative trend for metoprolol. It is concluded that diltiazem, given as monotherapy to hypertensive patients, does not impair subjective well-being.
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  • 35
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    Molecular and cellular biochemistry 104 (1991), S. 45-50 
    ISSN: 1573-4919
    Keywords: hypertension ; Dahl rats ; angiotensin converting enzyme ; cardiac hypertrophy ; angiotensin II
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    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Angiotensin II has previously been reported to have in vivo and in vitro cardiac hypertrophic effects. We used the salt-sensitive Dahl rat genetic strain to separate mechanical (pressure overload) vs. hormonal (renin-angiotensin system) input in cardiac hypertrophy. Blood pressure was significantly increased and left ventricular hypertrophy, as indexed by LV/BW ratios, was present at 7 and 15 days in rats receiving 4% and 8% NaCl compared to the 1% controls. There was no effect of the angiotensin converting enzyme inhibitor, enalapril maleate, on lowering the blood pressure in 8% NaCl-treated animals, however, there was a significant reduction in LV/BW ratio in 8% NaCl-treated animals that received this drug. Left ventricular angiotensinogen mRNA activity was significantly reduced in rats receiving 4% and 8% NaCl. In this model of hypertension the cardiac hypertrophy which develops is largely dependent on mechanical forces though there remains a significant contribution to this process from either circulating or localized angiotensin II production. Regulation of angiotensinogen gene expression in the hypertrophied left ventricle suggests that volume and electrolyte control of angiotensinogen gene expression in the heart and/or hereditary factors are predominant in the control of regulation of this gene in the left ventricle of Dahl rats.
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  • 36
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Aromatic acid isomers ; Low capacity ion-exchange resin ; Microbore packed columns
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    Topics: Chemistry and Pharmacology
    Notes: Summary A low-capacity, anion-exchange, porous-polymer resin was used as the packing material in a microbore column. Using a phosphate buffer containing various organic modifiers, retention behavior of substituted benzoic acid isomers with amino, chloro, methyl, nitro and carboxylic groups was investigated. The effect of ethanol, acetonitrile and sodium dodecylsulfate used as organic modifiers on the retention behavior at various eluent pH values was studies and optimum separations of the positional isomers reported.
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  • 37
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    Chromatographia 18 (1984), S. 668-672 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Mixed eluents ; Preferential sorption of eluents ; Pressure effects
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    Topics: Chemistry and Pharmacology
    Notes: Summary Pronounced base line perturbations were repeatably observed in LC both in alternating recycling and in backflushing experiments when binary eluents and refractometric detectors were used. The perturbations which we call eigenzones appeared immediately after operating the recycling or the backflushing valve, and their size and shape depended on the nature of both the column filling and the mixed mobile phase as well as on the pressure drop across the column. Experimental results presented confirm that the primary causes of the eigenzones were the pressure changes in the columns which influenced the sorption equilibrium of mixed eluent components within the column packing. Some practical consequences of this effect are briefly discussed.
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  • 38
    ISSN: 1612-1112
    Keywords: Polycyclic aromatic hydrocarbons ; Column liquid chromatography ; Polyphenyl bonded phases ; Retention and carbon content
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    Topics: Chemistry and Pharmacology
    Notes: Summary The relationship between the retention of PAHs having various molecular sizes and the carbon contents (%) of bonded stationary phases with various types of ligands were investigated. The examined stationary phases were phenyl, diphenyl, triphenyl and benzyl-bonded silicas. The data indicated that sometimes it is not true that the retention of any solute relates linearly to the carbon content of the stationary phase. As the result, it is suggested that the pore size distribution of the silica support, the bulkiness of the ligand bonded to the silica and the molecular size of solute should also be considered before any precise statement can be made.
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  • 39
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    Chromatographia 18 (1984), S. 175-182 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Fourier transform IR ; Polar compounds ; Coal products
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    Topics: Chemistry and Pharmacology
    Notes: Summary Fourier-transform infrared spectrometry (FTIR) was utilized as a detection system for high-performance liquid chromatography of polar compounds on a normal bonded-phase system. In addition to FTIR, UV (254 nm) and refractive index detection were employed in the separation of model compounds containing oxygen and nitrogen atoms in their molecules (phenols, alcohols, neutral and weakly basic nitrogen compounds). A polar amino-cyano (PAC) bonded-phase column was employed with a binary mobile phase (98:2 CDCl3:CH3CN). The separations and the information gained from each detector is discussed, including interactions between sample material and mobile phase. A polar fraction of a coal-derived product is also chromatographed under identical conditions. The results based on FTIR detection and chromatographic retention behavior suggest the exclusive presence of hindered and unhindered phenols.
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  • 40
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    Chromatographia 18 (1984), S. 211-215 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Alkylbenzenes ; PAHs ; Retention prediction ; Microcomputer
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    Topics: Chemistry and Pharmacology
    Notes: Summary The microcomputer-assisted retention prediction system in C18 reversed-phase HPLC is described. The system is based on the use of the hydrophobic parameter and the correlation factor of alkylbenzenes and polycyclic aromatic hydrocarbons (PAHs) which are highly correlated to their retention in reversed-phase HPLC. The system is evaluated by comparing the retention data between measured and predicted values. One of the typical examples applied for PAH analysis in the extracts of diesel particulate matter shows the high potential of the system investigated.
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  • 41
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    Chromatographia 18 (1984), S. 216-220 
    ISSN: 1612-1112
    Keywords: Cation exchangers ; Column liquid chromatography ; Exchange capacity, determination ; Organic peroxidation
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    Topics: Chemistry and Pharmacology
    Notes: Summary Two oxidation procedures for the synthesis of silicabased aliphatic sulfonic acid cation-exchangers for HPLC are described. Several reaction conditions for oxidizing a terminal-bonded thiol with organic peroxides are provided along with their yields, capacities, reproducibility, and chromatographic behavior. Also, three methods for determining exchange capacity are discussed, and their relationship to the capacity factors of charged solutes is compared. The maximum capacity determined by the titration of the bonded silica was 0.34 meq/gram. The general problems of synthesizing cation-exchangers, measuring their efficiencies and exchange capacities, and evaluating their overall performances are outlined.
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  • 42
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    Chromatographia 18 (1984), S. 369-373 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion exchange ; dynamic ; Metal ions ; Equilibria effects
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    Topics: Chemistry and Pharmacology
    Notes: Summary Equilibria occurring during the dynamic ion exchange separation of metal ions were examined, and their effect on the chromatography of the metal ions was evaluated. Bonded reversed-phase silica, pure organic reversed phase, and silica columns were used to differentiate between the role of silica and the reverse phase. The results show that system peaks had the most important influence on the applicability of dynamic exchangers to quantitative metal ion determinations. The response of system peaks to sample composition (pH, ionic strength, matrix effects) was complicated and could not be predicted easily. Equilibria effects that can cause analytical errors were identified and recommendations for elimination of such errors are given.
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  • 43
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Amines ; Phenols ; Fourier transform I.R.
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    Topics: Chemistry and Pharmacology
    Notes: Summary Several chromatographic parameters have been examined as to their effect on detectability for microbore high-performance liquid chromatography coupled with Fourier-transform infrared spectrometry. Detection limits for several compound classes are presented as amount injected. Improvements in detectability for this technique are discussed.
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  • 44
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Polystyrene packings ; Pre-column derivatization ; Thiamine compounds ; UV and fluorescence detection
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    Topics: Chemistry and Pharmacology
    Notes: Summary The chromatography of thiochrome and related phosphate esters was studied on two different polystyrene packing materials. The adsorbents were compared with respect to capacity factors, plate heights and resolution factors measured with different mixtures of phosphate buffer (pH 8.5) and methanol. In contrast with derivatized silica, these phases were found to be stable using an alkaline mobile phase and sample. Fast separations were possible with good peak symmetry at all organic modifier concentrations.
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  • 45
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    Chromatographia 18 (1984), S. 445-448 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Amino-bonded stationary phase ; Ion-exchange ; Fermentation solution ; Biomass
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    Topics: Chemistry and Pharmacology
    Notes: Summary In this work the analytical separation of biomass hydrolysis and fermentation products is described. Aminobonded phase and ion exchange materials (HPX 87H, HPX 42A, μ Spherogel Carbohydrate) were used as HPLC stationary phases for the determination of monomeric and oligomeric carbohydrates, carbohydrate degradation and fermentation products. The HPX 42A and the amino-bonded phase columns are especially suitable for the analysis of the gluco oligomers. The HPX 87H column separates the monomeric sugars and their degradation and fermentation products (e.g. furfurals and ethanol) very well. Using the μ Spherogel Carbohydrate column the lower gluco-oligomers as well as the monomeric sugars and their degradation and fermentation products, can be determined within 35 minutes.
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  • 46
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral bonded phase ; Racemate resolution
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    Topics: Chemistry and Pharmacology
    Notes: Summary A chiral stationary phase with an immobilized, optically active diamine was prepared for the separation of enantiomers. The synthesis of the phase was carried out by bonding (−)trans-1,2-cyclohexanediamine to microparticulate silica gel through the coupling agent 3-glycidoxypropylsilane. The resolution of the racemic compounds catechin, 2,2′-dihydroxy-1,1′binaphthyl and trans-1,2-cyclohexandiol, is reported.
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  • 47
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    Chromatographia 18 (1984), S. 495-498 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; PAHs ; Molecular shape recognition
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    Topics: Chemistry and Pharmacology
    Notes: Summary The molecular-shape recognition of polycyclic aromatic hydrocarbons has been studied on various stationary phases in reversed-phase high-performance liquid chromatography. The examined stationary phases were phenyl-, diphenyl-, triphenyl- and benzyl-bonded silicas. The results of regression analysis inidcated that triphenylsilica is the best packing material to recognize the difference in the molecular-shape of structural isomers. This fact was confirmed by the separation of 4-ring isomers.
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  • 48
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Retention data ; Substituted benzene derivatives ; Correlations
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    Topics: Chemistry and Pharmacology
    Notes: Summary The capacity factors of substituted benzene derivatives on bonded phases of various chain lengths in the reversed-phase mode have been measured and correlation of retention data between four stationary phases has been investigated by linear regression analysis. As a result, a difference in the retention mechanism between phases of shorter chain length and octadecylsilica was observed. In addition, it is also apparent that the multicombination treatment between retention data and descriptors such as π, HA, HD and σ promises the possibility of predicting the retention of substituted benzene derivatives on various reversed-phase stationary phases.
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  • 49
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Polyamines ; Dansyl derivatives ; Peak compression
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    Topics: Chemistry and Pharmacology
    Notes: Summary Analytical conditions for the high-speed, reversed-phase, liquid chromatographic of a diamine (putrescine) and polyamines (spermine and spermidine) were determined. Various elution modes were employed using the same mobile phase constituents: 20mM sodium heptane sulfonate and 20mM acetic acid as solvent A and, pure acetonitrile as solvent B. Samples were derivatized with dansyl chloride before injection. Under isocratic conditions, the separation of the three polyamines was achieved in 7 min. The use of a linear elution gradient led to the same analytical time but with a better resolution of the putrescine peak from non-polyamine frontal peaks. For these measurements, the sample size was 5μl. This volume was increased to 20μl and the use of a steep gradient combined with the peak-compression technique allowed a fast analysis in 2–3 minutes, which may be compared with a 30 min run time necessary when a conventional column is used.
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  • 50
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Normal phase separations ; Cyanopropyldimethyl silica ; Chloro-added polycyclic aromatic hydrocarbons ; Environmental samples
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    Topics: Chemistry and Pharmacology
    Notes: Summary Retention characteristics in normal phase HPLC of highly biologically active chloro-added polycyclic aromatic hydrocarbons (PAHs) were studied. Silica, cyanopropyldimethylsilyl- and aminopropylsilyl- modified stationary phases were investigated. Retention properties of chloroadded PAHs on these phases were shown to be strongly influenced by the number of chloro-additions. This is due to the strong polarity of the methylene carbon at the chloro-addition site. Active silica had a strongly degrading effect on the unstable chloro-added PAHs during separation. Aminopropylsilica did not exhibit sufficient selectivity towards chloro-added PAHs when compared to chlorosubstituted PAHs. Cyanopropyldimethylsilica was shown to be applicable to a group separation of chloro-added and chloro-substituted PAHs. A fast clean-up procedure for chloro-added PAHs in complex samplesis outlined. It involves an initial elimination of more polar substances on a short open column with strongly deactivated silica and a subsequent separation on a cyanopropyldimethylsilyl HPLC column in normal phase mode.
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  • 51
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    Chromatographia 32 (1991), S. 345-349 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Column packings ; Pore size distribution ; Diffusion and adsorption ; Band broadening
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    Topics: Chemistry and Pharmacology
    Notes: Summary The complex intraparticle structure typical of chromatographic column packings has been analyzed by use of an equivalent network model which emphasizes pore size distribution and connectivity. Special attention is given as to the way in which diffusion and adsorption interact and display modified peak spreading characteristics according to the morphology of the pore space. This study reveals a very significant increase in the column band broadening over that expected from physical adsorption which can arise from particular distributions of pore sizes. This has implications for designing packings which take advantage of the separating power due to adsorption but do not compromise the resolution of the chromatographic system.
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  • 52
    ISSN: 1573-8221
    Keywords: hypertension ; β-adrenoreceptors ; lymphocytes ; man
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    Topics: Biology , Medicine
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  • 53
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Size exclusion chromatography ; Styrene-methacrylate polymers ; IR and UV spectroscopy ; Lubricating oils additives
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    Topics: Chemistry and Pharmacology
    Notes: Summary Characterization of a poly(styrene-alkyl methacrylate) viscosity index improver according to its chemical composition distribution and molecular weight distribution was carried out by liquid adsorption chromatography, size exclusion chromatography and infrared and ultraviolet spectrophotometry. The industrial polymer was fractionated by liquid chromatography using silica gel as adsorbent and a mixture of 1,2-dichloroethane and methanol as mobile phase. Each fraction was analyzed by size exclusion chromatography and infrared and ultraviolet spectroscopy. The number average molecular weight ranged from 10000 to 36000 and the weight average molecular weight from 19000 to 264000. The styrene content of the various fractions analysed was between 29.5% and 72.2%.
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  • 54
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Laidlomycin, 26-deoxylaidlomycin
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    Topics: Chemistry and Pharmacology
    Notes: Summary High performance liquid chromatography on an octadecyl silica column has been used to determine laidlomycin: 26-deoxylaidlomycin ratios and to determine the concentration of both compounds by standard addition in samples prepared from fermentation broths ofStreptoverticillium olivoreticuli. A refractive index detector was preferred to an ultraviolet detector owing to the presence of UV-absorbing impurities which could not be completely separated from the substances of interest. Linear relationships were obtained from the calibration data. The coefficient of variation for the estimation of ratio and concentration of the compounds determined was better then 5%. The estimated limit of detection for both substances was about 50μg·ml−1.
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  • 55
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Molecular structure parameters ; Prediction of retention ; Phosphoroamidothiotes
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    Topics: Chemistry and Pharmacology
    Notes: Summary Multi-variable regression analysis between lnkw, c (in retention equation lnk′=lnkw+cCb) and molecular structure parameters, including hydrophobicity, electric effect, field effect and position-specific effect constant, was carried out with O-ethyl, O-aryl and N-isopropyl phosphoroamidothioates as test solutes. With these quantitative relationships, the retention behaviour of these solutes for different mobile phase compositions was predicted. The results showed that there are only 26.7% of total, experimentally measured, capacity factors with relative deviations larger than 5% and only 2.2% with deviations larger than 10%, which means that it is possible to apply the method reported to predict retention values for qualitative purposes for different mobile phase compositions.
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  • 56
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Histamine in wine ; Pre-column derivatization ; Solid phase extraction
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    Topics: Chemistry and Pharmacology
    Notes: Summary A method for determining histamine in wine by precolumn derivatization with PITC (phenylisothiocyanate) with reversed-phase HPLC and UV detection is reported. Histamine can be determined together with the 24 amino acids within 40 min, or separately in a shorter time (less than 4 min) if a prior solid phase extraction clean-up is used.
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  • 57
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Cyclodextrin inclusion complexes ; Structure-retention relationships ; Polycyclic aromatics
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    Topics: Chemistry and Pharmacology
    Notes: Summary The retention behaviour of a group of polycyclic aromatic hydrocarbons having nearly equal ionization potentials but different molecular polarizability values was investigated by reversed-phase HPLC and gas chromatography, using β-cyclodextrin as a selective inclusion reagent. In HPLC, the cyclodextrin was applied as an additive to the ethanolwater binary mobile phase, while in gas chromatography β-cyclodextrin served as the stationary phase coated on an inert support. The relationships between the capacity factors, molecular polarizabilities and the shape parameter of solute molecules is discussed.
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  • 58
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    Chromatographia 31 (1991), S. 67-70 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Cortico-steroids ; Drug adulterants
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    Topics: Chemistry and Pharmacology
    Notes: Summary A sensitive and specific method for quantitation of the steroids betamethasone, prednisolone and cortisone acetate commonly used as adulterants in locally produced herb extracts and in certain homeopathic drugs is described. Reverse-phase liquid chromatography with UV detection has been used.
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  • 59
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    Chromatographia 31 (1991), S. 80-84 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion chromatography ; Poly(vinyl alcohol) gel ; Inorganic anions ; UV detection for IC
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    Topics: Chemistry and Pharmacology
    Notes: Summary Poly(vinyl alcohol) (PVA) gel shows ionic retention properties for common inorganic anions when an acidic eluent is used. The ionic property of the PVA gel is due to the proton-acceptable nitrogen atoms of the cross-linking agent and the carboxylic residues being comprised in the gel matrix. The extent of the net charge on the gel surface depends on the pH of the eluent. At a pH ranging from 2.3 to 5.3, the PVA gel behaves as a weak anion exchanger with very low ion-exchange capacity. At these conditions four UV-absorbing inorganic anions (bromate, bromide, nitrate, and nitrite) are separated by eluting with aqueous sulfuric acid. Alkyl groups introduced on the gel surface hinder the ionized solute molecules from accessing to the positively charged functional groups on the gel surface. A neutral solute (HNO2) is retained with non-ionic interactions.
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  • 60
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Injection conditions ; Chlorophylls and carotenoids ; Extraction solvents ; Phytoplankton pigments
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    Topics: Chemistry and Pharmacology
    Notes: Summary The RP-HPLC analysis of chlorophylls, their degradation products (chloropigments) and carotenoids is very sensitive to the nature of the injection solvent. The effect of sample-solvent interaction can result in the production of distorted, or even false, peaks that could be erroneously interpreted as “pigment like” or as poor chromatographic resolution. The previously suggested theoretical explantion, based on differences in solvent characteristics as expressed by the Polarity Index (P′) or even by the more precise solvent strength parameter for reversed-phase systems (S) we use, was unsatisfactory. The problem seems more complex, with other parameters such as injection volume and solute concentration or solvent selectivity also playing a role. As a practical consequence, however, suggesions are made for optimum injection conditions. Also, the presence of ion-pairing reagents in the injection solvent is demonstrated to be unnecessary.
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  • 61
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    Chromatographia 31 (1991), S. 129-132 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; End-capping ; Chiral stationary phase ; Enantioselectivity
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    Topics: Chemistry and Pharmacology
    Notes: Summary The effect of end-capping chiral stationary phases (CSP's) derived fromN-(2-naphthyl)alanine undecyl ester has been examined using either trimethylchlorosilane (TMCS), hexamethyldisilazane (HMDS), or bis(trimethylsilyl) trifluoroacetamide (BSTFA) as end-capping reagents. The separation factor (α) and capacity factor (k′) of the enantiomers ofN-(3,5-dinitrobenzoyl)leucine octadecyl amide andN-(3,5-dinitrobenzoyl)alanine butyl ester were evaluated on three columns all packed with material from the same batch of stationary phase. These columns were essentially identical before, but not after end-capping with the above reagents. TMCS and HMDS were found to be superior to BSTFA, which appears to cause a significant loss of bonded phase from the silica surface. It seems that residual silanols affect the retention either by interacting with the analyte or by interacting with strands of stationary phase. End-capping usually increases enantioselectivity, sometimes by decreasing k′ for the first enantiomer and increasing k′ for the second enantiomer. The enhancement in enantioselectivity is greatest in relatively nonpolar mobile phases and occurs to a greater extent for phases having incomplete surface coverages.
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  • 62
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Liquid crystal bonded phase ; Polycyclic aromatics ; Carvone and pulegone
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    Topics: Chemistry and Pharmacology
    Notes: Summary A chromatographic and thermodynamic study of the compound [4-(allyloxy)benzoyl]-4-methoxyphenyl (ABMP) as a model of a chemically bonded liquid crystal stationary phase for HPLC was undertaken. A number of polycyclic aromatic hydrocarbons (PAHs) and two small solutes, carvone and pulegone, were studied under varying solvent and temperature conditions. Plots of log k′ vs. % organic in the mobile phase were not completely linear in all cases. The van't Hoff plots revealed at least one phase transition. The enthalpies of solute transfer from the mobile phase to the ABMP phase were determined for several PAHs. All tests indicate that ABMP possess liquid crystal properties when bonded to particulate silica.
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  • 63
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    Chromatographia 31 (1991), S. 193-205 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Column liquid chromatography ; Silanol adsorption centres ; Strongly interacting adsorption sites ; Suppression of adsorption activity
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    Topics: Chemistry and Pharmacology
    Notes: Summary In this second part of the review heterogeneity of the silica surface is described and evidence is presented for the existence of a low population of strong adsorption sites. Methods of detection and determination of these strongly interacting sites are discussed. The last part of the review is devoted to the suppression of unwanted adsorption activity. Methods of blockage and special methods for the preparation of HPLC packings are described.
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  • 64
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    Chromatographia 31 (1991), S. 277-280 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Simplex optimization ; Narasin in fermentation broth ; Vanillin
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    Topics: Chemistry and Pharmacology
    Notes: Summary A rapid HPLC assay with post-column derivatization has been developed for the determination of narasin in fermentation broth. The reaction of narasin with substituted benzaldehydes was investigated under first order conditions and the rate constants were determined for a variety of substituted benzaldehydes. Vanillin reacted most rapidly to produce a red color. The reaction conditions were optimized to acheive a maximum response with a minimum analysis time.
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  • 65
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ovomucoid stationary phase ; Chiral separations ; Mobile phase effects ; Protein conformation
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    Topics: Chemistry and Pharmacology
    Notes: Summary The effects of alcoholic modifiers and pH on the chromatographic properties of an immobilized ovomucoid chiral stationary phase have been investigated using acidic, basic and neutral solutes. A series of primary, secondary and tertiary alcohols and pH's ranging from 3.5 to 6.0 were used in this study. The results indicate that both the shape and the hydrophobicity of the alcoholic modifier affect retention (k') and enantioselectivity (α). In general, an increase in the hydrophobicity of the modifier results in a decrease in k's and α's. However, this is not the case whent-butanol is the modifier, suggesting that the size of the alkyl moiety attached to the carbinol carbon also contributes to the chromatographic results. The pH studies indicated that Coulombic interactions play a role in the retention of the acidic and basic solutes. The results also suggest that in addition to ethanol and 1-propanol,t-butanol should be considered during optimization and that maximum efficiencies may be obtained at pH 5.0.
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  • 66
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Adsorption isotherms ; Immobilized serum albumen ; Chiral stationary phase ; Leucine, N-benzoyl derivative
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    Topics: Chemistry and Pharmacology
    Notes: Summary The saturation capacity of columns packed with bovine serum albumin immobilized on silica has been determined for the N-benzoyl derivative of leucine at different compositions of a 1-propanol/water mobile phase. In all cases it has been found that the equilibrium adsorption data are well accounted for by a biLangmuir isotherm. The experimental data are consistent with the assumption that the column saturation capacity of the chiral selective sites as well as the saturation capacity of the non-selective sites are independent of the 1-propanol concentration in the range 0–10%.
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  • 67
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Bonded phase synthesis ; Alkyl and aryldimethyl phases ; CP/MAS NMR spectroscopy
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    Topics: Chemistry and Pharmacology
    Notes: Summary A comparison of newly synthesized, reversed-phase bonded stationary phases is presented. The materials studied include monomeric n-octyl, n-octadecyl, aryl and n-octyldihydrogeno bonded-phases. Differences in reactivity of the silane functional groups are demonstrated and the high coverage obtained with the hydrogeno-bonded phases is shown. The structures of the bonded phases have been determined by29Si and13C CP/MAS NMR spectroscopy.
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  • 68
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    Chromatographia 31 (1991), S. 347-350 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chemically modified silicas ; Surface states ; n-alkylbenzenes
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    Topics: Chemistry and Pharmacology
    Notes: Summary The thermodynamic behaviour of n-alkylbenzenes on chemically modified silicas in reversed-phase liquid chromatography has been examined in acetonitrile-water and methanol-water systems. Plots of the thermodynamic parameters obtained against the organic solvent compositions indicate an interesting trend which implies that the surface states of the chemically modified silicas under the two eluent systems are different.
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  • 69
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    Chromatographia 31 (1991), S. 362-366 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Particle size distribution ; Stationary phase stress ; Silica gel
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    Topics: Chemistry and Pharmacology
    Notes: Summary A particle size distribution analysis has been completed on three different HPLC column packing materials including silica gel (Si60) and two bonded phases (RP8 and RP18). The stationary phases were subjected to 18 hours stress with 1 N or 3 N KOH and found to have quantitatively different distribution patterns initially, at 13 hours and finally at 18 hours although the average particle diameters for the Si60 and RP8 were the same or higher at 18 hours as initially. Thirteen hoursstress with sodium octanesulfonate, tetrabutylammonium phosphate and ammonium acetate at exaggerated conditions also resulted in distributional changes with the Si60 and RP8 decreasing in average particle diameter when exposed to ammonium acetate and tetrabutylammonium stressing respectively.
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  • 70
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Biogenic amines ; Wine ; Food-related biogenic amines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Methods for the separation of food-related biogenic amines (histamine, tyramine, 2-phenylethylamine and tryptamine) have been developed based on ion-interaction reversed-phase liquid chromatography. Two different interaction reagents have been comparatively used, namely octylamine ortho-phosphate (at wave-lengths of 230, 254 and 280 nm) and octylamine salicylate (at a wavelength of 254 nm). The different elution sequence orders shown by the investigated amines for the two reagents are discussed and compared. The detection limits obtained were 20 ppb for tryptamine (λ =280 nm), 500 ppb for 2-phenylethylamine (λ=254 nm), 400 ppb for tyramine (λ=230 or 280 nm) and 900 ppb for histamine (λ=230 nm). The method was applied to the analysis of a five years old Italian red wine, in which 2-phenylethylamine (at a concentration of 72±3 ppm) and tryptamine (at a concentration of 4.0±0.3 ppm) were found to be present.
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  • 71
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    Chromatographia 31 (1991), S. 387-392 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Retention model ; Self-association of water
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    Topics: Chemistry and Pharmacology
    Notes: Summary An attempt has been made to gain a semi-quantitative insight into the self-association of water molecules through hydrogen bonds. This was only possible with the use of a new solute retention model for the chromatographic systems by considering intermolecular interactions between the constituents of binary mobile phases. Four different sizes of the average associative aqueous multimer were assumed. By comparing measured and calculated retention values, the existence of associated aqueous multimers consisting of 100 aqueous monomer units is postulated as an average multimer structure.
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  • 72
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    Chromatographia 31 (1991), S. 401-410 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion-pair reversed-phase separations ; Nucleotides ; Extraction from cells and tissue ; Retention mechanism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary HPLC methods for the separation of nucleotides, nucleosides and nucleobases by ion-pair reversed-phase are reviewed. The advantages of these are discussed versus anion-exchange and reversed phase separations. Extraction procedures for nucleotide determinations from cells and tissues are pointed out in detail. Extracts from red blood cells, Ehrlich ascites tumour cells, hepatocytes, intestine are used for determination of nucleotide concentrations by the methods described.
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  • 73
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion exchange chromatography ; Quantitative amino acid analysis ; OPA/FMOC precolumn derivatization ; Cheese
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An improved HPLC method for the quantitative determination of the amino acids from hydrolysed cheese proteins and peptides is described. Some important improvements to the existing method are suggested. The addition of piperidine-4-carboxylic acid (PICA) as a hydrolysis-resistant internal standard enabled the quantification of secondary amino acids. The following analytical parameters have been determined: repeatability, detection limit and linearity in the measuring range. A statistical comparison with the classical ion chromatographic method gave an excellent correlation for all determined amino acids. Both methods are free of artifacts and systematic errors. Compared with ion chromatography, HPLC shows the following advantages: faster equilibration of the column, shorter retention times, more stable baseline, narrower peaks and more sensitive fluorescence detection. A drawback is the slightly lower repeatability for some amino acids.
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  • 74
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral separations ; Amino acids ; Fluorogenic derivatization ; N-(Chloroformyl)-carbazole
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    Topics: Chemistry and Pharmacology
    Notes: Summary A new reagent for fluorescence labelling of amino acids, N-(chloroformyl)-carbazole, has been used in order to achieve high sensitivity of detection as well as good optical resolution. The derivatization reaction is fast and conveniently carried out at room temperature by shaking a buffered aqueous solution of the amino acids with an acetone solution of the reagent. The individual derivatized amino acids are first separated and collected via chromatography on a standard octadecyl-silica column. Each amino acid derivative is then analyzed for enantiomer composition by re-injection on a BSA-silica (Resolvosil®) column using fluorescence detection. For some amino acids (alanine, threonine, phenylalanine, tryptophan) enantiomeric separation factors exceeding α=3 have been obtained. The phosphonic acid analogue of alanine (1-aminoethylphosphonic acid) was also found to be well resolved into its enantiomers.
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  • 75
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    Chromatographia 31 (1991), S. 465-468 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Catechins ; Grape seeds ; Proanthocyanidins ; UV-visible spectroscopy/diode array detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Reversed-phase, high-performance liquid chromatography coupled to photodiode array detection has been used to analyse catechins and proanthocyanidins extracted from grape seeds. Results show that the ethyl acetate fraction obtained by passing extracts of samples adjusted to pH 7.0 through preconditioned C18 SEP-PAK cartridges contains several catechins and proanthocyanidins. Seven peaks have been assigned to standard catechins and proanthocyanidins on the basis of their retention times and UV spectra. Other peaks which appear in the chromatogram show spectral behaviour similar to that of standard catechins and proanthocyanidins.
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  • 76
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    Chromatographia 31 (1991), S. 478-480 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Orosomucoid ; Complex glycans ; α1 glycoprotein ; Glycopeptides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The glycoforms contained within each glycosylation site of orosomucoid can be separated by reverse-phase HPLC without removal of the associated peptide or chemical derivatization. The chromatographic properties of the glycopeptides are dominated by the peptide portion but modified by the hydrophilicity of the glycan in a regular manner depending on its size. Assignments for known structures are readily made, permitting quantitative assessment of changes in glycoform concentration at individual glycosylation sites.
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  • 77
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Immunoaffinity precolomn ; Oestrogens ; Bioanalysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An automated liquid chromatographic system is described using immunoaffinity precolumns for sample pretreatment. The system consists of a column-switching unit allowing preconcentration from a large volume of sample (e.g. 15 ml of urine) onto an immunoaffinity precolumn (containing polyclonal antibodies immobilized on Sepharose). After sorption, the analytes are desorbed by a mixture of two cross-reacting solutes, followed by reconcentration on a C-18-bonded silica precolumn, and then separation on a C-18-bonded silica analytical column. Using oestrogen steroids as model compounds and UV absorbance detection, the minimum detectable concentration is ca. 200 ng/l with a repeatability of 6–8%. The total analysis time is 45 min which allows the unattended analysis of 30 samples per day. The features of the sample pretreatment method, especially of the immunoselective desorption, are evaluated and the general applicability of the system is discussed.
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  • 78
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Selenonium and arsonium cations ; AAS detection ; Chromatographic optimization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Optimal mobile phase compositions were determined for the separation of selenonium ions [trimethylselenonium, (2-hydroxyethyl)dimethylselenonium and (2-acetoxyethyl)dimethylselenonium] and, separately, for arsonium ions (tetramethylarsonium, arsenobetaine, and arsenocholine) by HPLC with detection by atomic absorption spectrometry (AAS). Surface response methodologies were used to predict the variations in detector response (peak area), capacity factors, and selectivities as a function of the mobile phase composition. For selenonium analytes, a mixture of triethylammonium and trimethylsulfonium ions in the methanol-1% acetic acid mobile phase provided a compromise between resolving power and chromatographic efficiency. By contrast, optimum chromatography of the arsonium analytes was obtained by replacing onium additives in the mobile phase by picrylsulfonic acid. For both selenonium and arsonium analytes, the dominant interaction with the stationary phase was with residual silanols and improvements to the chromatographic performance of these analytes resulted in appreciable decreases in their limits of detection.
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  • 79
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Flame ionization detection ; Poly(styrene-co-methyl acrylate) ; Poly(methyl acrylate-co-n-butyl acrylate) ; Chemical composition distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This investigation is focused on the development of HPLC with subsequent flame ionization detection as a tool to determine the chemical composition distribution of non-or poorly UV absorbing copolymers. Experiments were carried out with poly(styrene-co-methyl acrylate) and poly(methyl acrylate-co-n-butyl acrylate) copolymers. HPLC combined with FID provided useful qualitative information. Quantitative information could be obtained after calibration.
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  • 80
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Non-porous cation exchanger ; Hemoglobin A1C ; pH gradient elution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary High-performance ion exchange chromatography on a nonporous cation exchanger was examined for the separation of glycated hemoglobin. A standard sample of human hemoglobin was separated with salt or pH gradient elution. Glycated hemoglobin A1C was well separated from other hemoglobin variants in less than 10 minutes. pH gradient elution gave better resolution than salt gradient elution.
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  • 81
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Restricted access packings ; Packings with surface barriers ; Sample clean-up of biologically active analytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Various types of, so-called, restricted access packings have been developed for sample clean-up and analysis of biologically active solutes by means of HPLC. The unique feature of these packings is that they prevent the access of matrix components such as protein whilst selectively retaining the drug components and their metabolites. This results from the fact that the particles of the packings possess a surface barrier for large solutes at the external or internal surface area and exhibit a controlled gradient in the chemical surface composition. They are grouped, according to their particle structures, into internal-surface reversed phases (ISRP), shielded hydrophobic phases (SHP), semi-permeable surfaces (SPS), dual zone phases (DZP) and mixed functional phases (MFP). The structural characteristics and the chromatographic properties of these packings are reviewwed, especially with regard to their use in the assaying of drugs.
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  • 82
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Air analysis ; Dansylhydrazones of carbonyl compounds ; Chemiluminescence ; Fluorescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Sensitive and selective detection of dansylhydrazones of atmospheric carbonyl compounds (aldehydes and ketones) can be achieved using high performance liquid chromatography (HPLC) with fluorescence or chemiluminescence detection. The carbonyl compounds are derivatized by drawing air through small glass cartridges packed with porous glass particles impregnated with dansylhydrazine. After sampling, the contents of the cartridges are analyzed on-line by using a small plug of water (200 μL) to transfer and focus the hydrazone derivatives at the head of a HPLC column. Greatly increased sensitivity over traditional methods derives from 1) analysis of the entire contents of the sampling cartridge, and 2) detection by fluoresence or peroxyoxalate chemilum-inescence. Results are compared for photo-initiated and H2O2-initiated peroxyoxalate chemiluminescence. This novel and practical system enables the detection of sub-ppbv concentrations of formaldehyde, acetaldehyde, acetone and higher carbonyls in air using relatively short sampling times.
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  • 83
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Alkyl bonded phases ; Non-specific selectivity ; Hydro-organic mobile phases ; Retention of alkanoate esters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A thermodynamic equation is derived for the non-specific selectivity of alkyl bonded phases as a function of the mobile phase composition using a displacement mechanism to model the sorption of solvents into the bonded phase. The equation is used to calculate the thermodynamic parameters which characterize the incremental behavior of a hydrophobic group in ethyl alkanoate and methyl perfluoroalkanoate ester solutes chromatographed with water-methanol and water-acetonitrile mobile phases on both octyl and octadecyl bonded phases.
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  • 84
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    Chromatographia 32 (1991), S. 23-26 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Enzyme assay ; Alanine amino transferase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An improved method of alanine-amino transferase determination is proposed. The reaction is carried out with alanine and 2-oxoglutarate as substrates and analysis is by HPLC on a reversed-phase chromatographic system using a C18 column and tetrabutylammonium phosphate in phosphate buffer (pH 7.0)-acetonitrile as mobile phase. The enzyme activity was determined by directly following the formation of pyruvic acid without employing any secondary reaction, which is necessary in the spectrophotometric method. The detection limit of pyruvic acid is 10 pmole μl−1 and the standard deviation for the enzymatic activity of standard solutions is 5.4%. Furthermore under the chromatographic conditions selected it is possible to detect the presence of some intermediate species.
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  • 85
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Furfural ; Hydroxymethylfurfural ; Apple juice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A rapid and sensitive method for determining 2-furaldehyde (FUR) and 5-hydroxymethyl-2-furaldehyde (HMF) in apple juices and juice concentrates has been developed. The method for FUR and HMF involves the solid-liquid extraction of the juice by using a C-18 cartridge prior to reversed-phase separation with detection at 280 nm. The mobile phase was acetonitrile-water (8/92, v/v) at a flow rate of 1.0 ml/min. Recoveries from apple juices and juice concentrates spiked at different levels ranged from 94.1 to 104.0 (FUR) and 94.5 to 100.5 (HMF). The quantification limit for both, FUR and HMF, was 5 ppb.
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  • 86
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    Chromatographia 32 (1991), S. 61-64 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Sample-induced pH gradients ; Separation of proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The technique of an internal pH gradient induced by the sample is applied to the separation of proteins by liquid chromatography. Compatibility of the method with microcolumns is demonstrated and examples of separations on different types of sorbents are given.
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  • 87
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Counter-current extraction ; Chiral resolution ; Ofloxacin enantiomers ; Aqueous two-phase system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The partial resolution of some drug enantiomers by counter-current extraction in an aqueous two-phase system using bovine serum albumin (BSA) or ovomucoid (OVM) as chiral discriminator is described. The phase system was prepared with dextran 40, polyethylene glycol and a protein. Ofloxacin (OFLX) enantiomer was well recognized by the BSA system, whereas the enantiomers of carvedilol (β-blocker) and DG-5128 (a new oral hypoglycaemic drug) were hardly recognized by the OVM system. The distribution coefficients of (S)-, (R)- and rac-OFLX varied with pH. Good enantioselectivity for OFLX was obtained at relatively high pH (≥ pH 9). The crude optically enriched OFLX enantiomers were extracted from the aqueous fractions and finally purified by thin-layer chromatography.
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  • 88
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Protein separations ; Peptide separations ; Octadecylalumina
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A recently-developed octadecyl-bonded alumina (ODA) stationary phase was evaluated for the separation of peptides and proteins by reversed phase high performance liquid chromatography. Using standard water-acetonitrile mobile phase gradients containing 0.1 % trifluoroacetic acid, the average peak capacity obtained for the separation of a mixture of ribonuclease a, cytochrome c, lysozyme and carbonic anhydrase on an ODA column are similar to that obtained on a widely used octadecylsilane (ODS) column. However, overall chromatographic resolution of the components of this mixture on ODA is inferior to that obtained on ODS. Cytochrome c peak areas were found to be ∼50% smaller on the ODA column than on ODS. On the other hand, both peak capacities and resolutions of octapeptide mixtures were found to be generally superior on the ODA column, and peak areas for a representative octapeptide were found to be virtually identical for both ODA and ODS columns. The differences in the results obtained on the ODA and ODS columns for these separations are attributed to the smaller pore size and unique fused-microplatelet shape of the ODA particles. Comparisons of the separations of the tryptic digest of cytochrome c on the ODS and ODA columns demonstrate that the ODA phase is potentially as useful as ODS for peptide mapping applications.
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  • 89
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Enantiomeric separation ; Chiral stationary phase ; Cellulose triacetate ; Flavanones ; Plant extracts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Flavanones ofArachis hypogaea, Hemizonia increscens, Eriodictyon glutinosum andThymus vulgaris extracts have been stereospecifically analysed by gradient elution on a column of cellulose triacetate supported on silica gel diol. The stereochemistry of naringenin, eriodictyol and homoeriodictyol was in favour of the 2S-configurated flavanones.
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  • 90
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Amino bonded phases ; Hydrogen chloride treatment ; Retention anomalies ; Normal-phase separations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The influence of hydrogen chloride on the retention properties of aminopropyl bonded phases is studied using a series of simple aromatics, phenols and acids. The result of the HCL treatment is to mediate the hydrogen bonding interaction between the solute's polar functional groups and the bound amino groups.
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  • 91
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    Chromatographia 32 (1991), S. 73-78 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion-pair separations ; Dianionic species ; Dionium reagent
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Dionium cations, polymethylenebis(tributylphosphonium)s (BuCnBPs), were used as ion-pair reagents for ion-pair chromatography of dianionic species, such as maleate, fumarate, phthalates, and naphthalenedisulfonates. The longer the length of methylene chain connecting the two phosphonium cationic ceterns within BuCnBP, the larger was the retention of these dianionic species. The dionium reagents had a higher retention ability compared to conventional monoonium reagents, and enabled a higher resolution among the dianionic species of structural isomers. The extraction behavior of the dianionic species in a loctanol/water system was also investigated. The retention behavior by the use of BuCnBP was discussed in comparison with the extraction behavior.
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  • 92
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral separation ; Chiral crown ethers ; Phenylglycine enantiomers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Previous work has demonstrated the possibility of crcating chiral stationary phases by coating a suitable support material via the mobile phase. The result is a wide variety of chiral phase systems which can be used in liquid chromatogrphy to separate enantiomers by a liquid-solid adsorption mechanism. The present paper demonstrates the potential of this technique for chiral crown ethers incorporating an α-D-mannopyranoside unit using the separation of phenyglycine enantiomers as an example.
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  • 93
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    Chromatographia 32 (1991), S. 85-86 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Antiepileptic drugs ; Optimised separation ; Serum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A fast and easy, iscratic high-performance liquid chromatographic method for the simultaneous determination of primidone, phenobarbital, phenytoin, carbamazepine and thiobutabarbital from serum samples has been developed. The optimal eluent composition is 36% acetonitrile, 24% methanol and 40% phosphate buffer. Using a programmable wavelength detector very low (sub-therapeutic) levels of the drugs can be measured.
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  • 94
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion-pair separation ; Salt concentration ; Charge number of solute ; Gouy-Chapman theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Thermodynamic and numerical treatments have been combined with Gouy-Chapman theory were to show that the effect of the salt concentration on the capacity factor in reversed-phase ion-pair liquid chromatography (RP-IPC) can be expressed as lnk′=A+blnCs. The parameter B is related to the charge number of the solute, and the parameter A is determined by both electrostatic and nonelectrostatic interaction, and can the linearly correlated with logarithm of the capacity factor in RP-HPLC for the solute with one negative charge. It also been observed that the electrostatic interaction is reduced with increasing salt concentration in RP-IPC, and this effect is more remarkable for solutes with more than the one negative charge of sulphonic acids.
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  • 95
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Size-exclusion ; Peptides ; Casein hydrolysate ; FAB-MS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A casein hydrolysate was eluted on a TSK G-2000 SW sizeexclusion high-performance liquid chromatography (SE-HPLC) column using a mobile phase which gives a correlation coefficient of 0.98 for the separation of 20 pure and synthetic peptides and proteins of molecular weight (M. W.) varying from 243.28 (Ala-Pro-Gly) to 43 000 (Ovalbumine) daltons. Further isolation and purification of peptides present in each of the 8 different fractions collected from the SE-HPLC were done by reversed-phase HPLC (RP-HPLC). Peptide experimental M. W. determined from the calibration curve obtained for synthetic or purified peptides was compared to their precise M.W. obtained by fast atom bombardment-mass spectrometry analysis (FAB-MS). The results do not show a separation of this complex hydrolysate by SE-HPLC according to the hydrodynamic volume of its constituents.
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  • 96
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Streaming current ; Specific pore volume and surface area ; Specific weight ; Bed porosity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The applicability and precision of the method allowing the determination of several characteristics of the sorbent and its bed from two simple chromatographic retention measurements were tested with porous metal oxides and some other solids. The typical time of one retention experiment is 1–3 minutes. The method was verified with chromatographic solid phases containing both mesopores and macropores. The agreement between the retention volume of the streaming current response, caused by the change in the concentration of the polar component of the binary hydrocarbon-based mobile phase, and the total volume of the liquid in the column is decisive for the applicability of the method. If the influence of the error in the determination of the sorbent's weight in the column and of the column tube's volume are neglected, the external and the total bed porosities and the specific weight of the sorbent can be determined with the relative error of the retention volume measurement. The error of the determination of the specific pore volume and internal bed porosity will be twice as much. The specific surface area can be determined approximately for sorbents with average and large surface areas.
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  • 97
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    Chromatographia 32 (1991), S. 523-526 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Debrisoquine ; Urine ; Phenotype
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An isocratic HPLC method is described. It allows the simultaneous determination of debrisoquine and 4-hydroxydebrisoquine in urine. Sample preparation involves a rapid and simple (one step) liquid-liquid extraction without derivatization. Separation, followed by UV-detection, is carried out on a nitrile column in reversephase mode with a binary, aqueous mobile phase. This rapid assay uses a new internal standard (guabenxane) and allows the determination of urinary concentrations with good precision and appropriate sensitivity.
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  • 98
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ruthenium mixed complexes ; Sulfoxides ; N-Heterocyclic bases ; Hydrophobic properties of aromatic ligand
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The elution behaviour of a series of dichlorobis-(dimethylsulfoxide)bis(N-heterocyclic)ruthenium(II) complexes has been investigated using reversed-phase HPLC. Similar trends as those displayed by the free N-heterocyclic bases have been observed for the complexes, essentially reflecting the hydrophobic properties of the aromatic ligands.
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  • 99
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    Chromatographia 32 (1991), S. 527-537 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Supercritical fluid chromatography ; Supercritical fludi extraction (SFE) ; Explosives ; Cholesterol ; Polymer additives
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Extraction with supercritical CO2 is a versatile method for sample clean-up and trace enrichment. The off-line coupling of SFE and HPLC is used to determine various explosives in debris as well as pesticides in soil. In food analysis the metod could be applied to determine cholesterol in noodles quantitatively. Correlations between the retention in RP chromatography and required extraction conditions could the established. The higher the organic modifier concentration in the eluent has to be, the smoother the extraction conditions required. With the non-volatile solutes studied, extraction temperature had no influence on extraction yield and speed. On-line coupling of SFE and capillary SFC is a very convenient and sensitive method for the determination of polymer additives. The coupling device described can also be used for “solventless” injection in capillary SFC.
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  • 100
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    Chromatographia 32 (1991), S. 555-558 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Organic acids ; Grape musts ; Direct injection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A simple method for reverse-phase HPLC analysis of organic acids present in must has been developed. It is carried out in isocratic conditions, with a weak dilute acid as eluent and U.V. detection. The aim is to minimize sample preparation merely to filtration: direct injection is proposed as an approach toin vivo conditions.
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