N. Lebris et D. Birot, AUTOMATED PH-ISFET MEASUREMENTS UNDER HYDROSTATIC-PRESSURE FOR MARINEMONITORING APPLICATION, Analytica chimica acta, 356(2-3), 1997, pp. 205-215
Association of microsensors and flow measurement techniques could prov
ide many advantages for the in-situ monitoring of marine environment.
First, adaptability of such sensors to autonomous measurement and unde
r pressure conditions has to be considered. This paper presents a labo
ratory study devoted to seawater pH flow measurement using ISFETs. The
measurement principle had to circumvent drift problems associated wit
h these sensors. This was performed by measuring potential steps produ
ced by a fast alternation of the sample and a standard buffer over the
sensor.:ln addition, interference of seawater ionic matrix on ISFET r
esponse was circumvented by the use of saline buffers. The precision o
f the method is better than 0.01 pH and could be further increased. It
s optimal accuracy will be limited to 0.01 pH, clue to uncertainties o
n the pH of saline buffers. The ability of ISFETs to operate under pre
ssure, up to 30 bars, over 43 h was demonstrated, without significant
decrease in sensitivity. The method could also be suitable for long-te
rm unmanned measurements. These first results incline to further exami
nation of the potentialities of this technique for pH monitoring at de
pth. (C) 1997 Elsevier Science B.V.