ISSN:
1436-5073
Keywords:
ammonia
;
sensor
;
colorimetric
;
plastic
;
optical
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract The preparation and characterization of three different plastic thin-film colorimetric sensors for gaseous ammonia is described. In the film sensors, the neutral form of a pH-sensitive dye (Bromophenol Blue, Bromocresol Green or Chlorophenol Red) was encapsulated in a plastic medium, either poly(vinyl butyral) or ethylcellulose plasticized with tributyl phosphate. Each of these film optodes gave a reproducible and reversible response towards gaseous ammonia. The sensitivity of the film sensors towards ammonia was found to be strongly dependent upon the pK a of the encapsulated dye. Thus, the film with Chlorophenol Red (pK a = 6.25), proved to be very insensitive (operating range: 0.29% 〈 %NH3 〈 100%), whereas the film with Bromophenol Blue (pK a = 4.1), was much more sensitive (operating range: 0.0003% 〈 %NH3 〈 0.11%). The sensitivity of a plastic film sensor decreased markedly with increasing operating temperature and the 90% response (15–38 s) and recovery (820-127 s) times were slow and activation-controlled.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01248252
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