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  • 1
    Electronic Resource
    Electronic Resource
    Flow Injection Determination of Nitrate in Vegetables Using a Tubular Potentiometric Detector (1995)
    s.l. : American Chemical Society
    Journal of agricultural and food chemistry 43 (1995), S. 704-707 
    Details
    ISSN: 1520-5118
    Source: ACS Legacy Archives
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jf00051a027
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  • 2
    Electronic Resource
    Electronic Resource
    Benzoate ion-selective electrode with improved selectivity and reproducibility for benzoate determination in medicinal syrups (1996)
    Springer
    Microchimica acta 124 (1996), S. 35-41 
    Details
    ISSN: 1436-5073
    Keywords: benzoate electrode ; direct potentiometry ; medicinal syrups ; ISE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract This paper describes the construction and evaluation of a benzoate anion selective electrode with enhanced working characteristics, namely reproducibility and selectivity, to be used in medicinal syrups analysis by direct potentiometry. The electrode, without an internal reference solution, was prepared with a PVC membrane, based onbis(triphenylphosphoranylidene) ammonium benzoate as ion-exchanger, dissolved in 2-nitrophenyl octyl ether as mediator solvent and 4-t-octylphenol as additive. The characteristics of the electrodes were evaluated in sodium benzoate solutions with adjusted ionic strength and showed a linear response in the range 10−2−2 × 10−4 mol dm−3 with a slope of 54.7 ± 0.5 mV/decade and a reproducibility of ±0.2 mV/day for solutions with pH 6.3. The potentiometric selectivity coefficients were determined for some possible interfering species and showed that the electrodes prepared with the additive had good selectivity, especially over iodide and nitrate, when compared with those without any additive. The electrodes were used for benzoate determinations in several medicinal syrups by direct potentiometry. The results gave recovery values in the range 98.3–104.6%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01244954
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  • 3
    Electronic Resource
    Electronic Resource
    Ion chromatographic determination of iodide in urine and serum using a tubular ion-selective electrode based on a homogeneous crystalline membrane (1997)
    Springer
    Microchimica acta 127 (1997), S. 55-60 
    Details
    ISSN: 1436-5073
    Keywords: iodide ; ion chromatography ; tubular potentiometric detector ; urine ; serum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The use of a laboratory-made iodide ion-selective electrode with tubular configuration and based on a crystalline membrane (AgI/Ag2S) as the detector for ion chromatographic determination of iodide in urine and serum is described. A CIS reversed-phase column was coated withN-cetylpyridinium chloride to prepare a low-exchange-capacity analytical column and with hexadecyltrimethylammonium bromide to prepare a concentrator pre-column. A 2.0 ml min−1 flow rate of deionized water and 0.1 mol 1−1 KNO3 solution was used for the pre-concentration and for the chromatographic separation, respectively. For optimum performance of the detector a background level of iodide was added into the column effluent. A linear relationship (r = 0.9997) between tubular electrode potential (as peak height) and iodide concentration in the range 5–400 μg 1−1 and a detection limit of 1.47 μg 1−1 were obtained. The method shows good reproducibility for both peak height (2.2% RSD) and retention time (1.3% RSD). Recoveries on its application to the samples were 93.0–100.9% for urine and 91.4–106.0% for serum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01243164
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  • 4
    Electronic Resource
    Electronic Resource
    Colorimetric determination of iron in infant fortified formulas by sequential injection analysis (1997)
    Springer
    Fresenius' journal of analytical chemistry 357 (1997), S. 1153-1156 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract  A procedure is described for the colorimetric determination of iron in infant fortified formulas based on sequential injection analysis (SIA). Iron(III) complexation with thiocyanate is used as colour developing reaction. The system enables the determination of iron in the samples (after digestion by dry ashing and treatment with 0.2 mol/L nitric acid in the range of 0.50–20.0 mg/L, consuming 140 μL of the sample and 8 mg thiocyanate per determination. The reactor geometry and the adjustment of the ionic content of the calibration solutions is important for the accuracy of the results. A regression line according to the equation [Fe(III) (mg/L)]SIA=−0.3(±0.4)+1.03(±0.04) [Fe(III) (mg/L)]FAAS was obtained after comparative analysis of a set of 12 samples. The measurement rate was 34 s, thus allowing to analyze 100 samples per hour with a relative standard deviation lower than 2%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160050322
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  • 5
    Electronic Resource
    Electronic Resource
    Flow injection system with gas diffusion for the sequential determination of total nitrogen and phosphorus in vegetables (1997)
    Springer
    Fresenius' journal of analytical chemistry 358 (1997), S. 657-662 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract  A flow injection system was developed for the sequential determination of total nitrogen and phosphorus in digests of vegetables using potentiometric and spectrophotometric detection systems, respectively. A tubular ammonium selective electrode with a sensor system composed of nonactin/monactin in tris(2-ethylhexyl) phosphate was used. The selectivity limitations of this electrode were overcome by the inclusion of a gas-diffusion unit in the system that separated ammonium from the rest of the sample matrix and allowed the determination of total nitrogen and phosphorus by the partition of the sample plug between two streams. The results obtained with the developed FIA system were in good agreement with those of the reference methods. Sampling rates from 40 to 60 samples per hour and relative standard deviations below 3.5% were achieved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160050486
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  • 6
    Electronic Resource
    Electronic Resource
    Monosegmented flow-analysis of slow enzymatic reactions: Determination of triglycerides in serum (1998)
    Springer
    Fresenius' journal of analytical chemistry 360 (1998), S. 100-103 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract  A monosegmented flow system (MCFA) is proposed to achieve slow enzymatic spectrophotometric determinations, here applied to the determination of triglycerides in blood serum. The sample (4.5 μL), enzymatic reagent (150 μL) and an air plug (100 μL) are simultaneously inserted into a carrier stream buffered to pH 7.9 (Tris ⋅ HCl). In order to avoid the cumbersome step of air removal, a relocating detector was used. This system handles about 60 samples/h, yielding precise results (r.s.d. usually〈2.5%). Sensitivity is 56 mAU ⋅ L/mmol up to 6 mmol/L triglycerides. Accuracy was assessed by running 50 samples already analysed by a conventional procedure yielding the equation CMCFA(mmol/L)=1.00(±0.04) CRef(mmol/L)−0.03(±0.08); r=0.990.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160050650
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  • 7
    Electronic Resource
    Electronic Resource
    Determination of citric acid in soft drinks using flow injection with potentiometric detection (1999)
    Springer
    Fresenius' journal of analytical chemistry 364 (1999), S. 266-269 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A flow injection analysis (FIA) system with potentiometric detection has been developed for the determination of citric acid in commercial fruit juices using a copper-selective tubular electrode. It consists of the complexation of citrate ion with copper (II) ion, monitoring the free copper (II) concentration. Linear relationships between the potential and log concentrations of citric acid in the range of 1 × 10–3 mol/L – 1 × 10–2 mol/L were attained with samples injected in the system without prior treatment. Repeatability was determined by assessing the relative standard deviation for ten replicate injections of different juice samples which varied from 1.2% to 3.0%. The results provided by the automated system were compared with those of an enzymatic conventional method used for the analysis of citric acid in food and a relative deviation of less than 4.0% was found. Recovery trials resulted in values from 97.0% to 101.0%. The system allows a sampling frequency of 60 samples/h.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160051335
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  • 8
    Electronic Resource
    Electronic Resource
    Determination of total nitrogen in food by flow injection analysis (FIA) with a potentiometric differential detection system (1999)
    Springer
    Fresenius' journal of analytical chemistry 364 (1999), S. 353-357 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A flow injection set-up based on potentiometric detection and gas diffusion device for the determination of total nitrogen in food is described. The detection system consisted of two ammonium-sensitive electrodes placed sequentially and each alternately operating as reference electrode. Tubular electrodes without an inner reference solution were prepared with a PVC membrane composed of nonactin in Tris (2-ethylhexyl) phosphate and potassium tetrakis (4-chlorophenyl) borate to reduce the membrane resistance. The food sample digests were inserted into the system, and the ammonium present was converted into ammonia gas. The gas diffused through a gas-permeable membrane to a buffer acceptor stream with a pH that ensured transformation to the ammonium cation, which was potentiometrically detected. Good agreement between FIA results and those provided by the reference procedure was obtained, with relative deviation errors below 5%. Using the proposed system, low reagent consumption is possible, a sampling rate of about 30 samples/h was achieved, as well as a good reproducibility for consecutive injections of the same sample (variation coefficient 〈 2%).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160051348
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  • 9
    Electronic Resource
    Electronic Resource
    Construction and evaluation of tubular potentiometric detectors sensitive to chloride, bromide, and iodide and based on homogeneous crystalline membranes (1993)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 347 (1993), S. 314-319 
    Details
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The construction of tubular potentiometric detectors is described, without an inner reference solution, sensitive to chloride, bromide, and iodide. They are based on homogeneous crystalline membranes obtained by high-pressure pressing of AgX/Ag2S powdered mixtures (X = Cl, Br and I). The respective operating characteristics are evaluated by comparison with conventionally-shaped electrodes with the same sensor. In general, the detectors showed similar operating characteristics as those of the corresponding conventional electrodes, namely the concentration range, in which they presented a Nernstian response, an excellent reproducibility, and an extremely rapid response rate which in some cases enabled the FIA manifolds to attain sampling rates of 360 samples/h.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00323813
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  • 10
    Electronic Resource
    Electronic Resource
    Square wave adsorptive stripping voltammetry of nickel and cobalt at wall-jet electrodes in continuous flow (1996)
    Weinheim : Wiley-Blackwell
    Electroanalysis 8 (1996), S. 1169-1173 
    Details
    ISSN: 1040-0397
    Keywords: Adsorptive stripping voltammetry ; Wall-jet electrode ; Square wave voltammetry ; Nickel ; Cobalt ; Trace metals ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Square wave adsorptive stripping voltammetry (SWAdSV) of nickel and cobalt at wall-jet electrodes in a continuous flow system has been evaluated. Characteristics and advantages relative to differential pulse adsorptive stripping voltammetry (DPAdSV) in continuous flow systems are explored. Under optimized experimental conditions, sensitivity is approximately a factor of ten higher than DPAdSV, and one-nanomolar detection limits are achieved. Solution deoxygenation is unnecessary and sample throughput is increased.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140081219
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