ELECTROCHEMICAL DETECTION OF TRACE HYDROGEN-SULFIDE IN GASEOUS SAMPLES BY POROUS SILVER ELECTRODES SUPPORTED ON ION-EXCHANGE MEMBRANES (SOLID POLYMER ELECTROLYTES)
G. Schiavon et al., ELECTROCHEMICAL DETECTION OF TRACE HYDROGEN-SULFIDE IN GASEOUS SAMPLES BY POROUS SILVER ELECTRODES SUPPORTED ON ION-EXCHANGE MEMBRANES (SOLID POLYMER ELECTROLYTES), Analytical chemistry, 67(2), 1995, pp. 318-323
A highly sensitive and fast-responding electroanalytical sensor for th
e determination of hydrogen sulfide in gaseous atmospheres is describe
d which eliminates oxygen interferences. It consists of a porous silve
r working electrode (facing the sample) supported on one face of an io
n-exchange membrane, which serves as a solid polymer electrolyte. The
other side of the membrane faces an internal electrolyte solution cont
aining the counter and reference electrodes. The performance of this s
ensor has been tested for the electroanalysis of H2S by amperometric m
onitoring, cathodic stripping measurements, and now injection analysis
. In all cases, the device displays a high current sensitivity and a l
ow background noise, so that quite low detection limits (45 ppb v/v, 0
.07 ppb v/v, and 3.7 x 10(-13) mol in amperometric, cathodic stripping
, and flow injection measurements, respectively) are estimated for a s
ignal-to-noise ratio of 3. The responses are found to be characterized
by both a good reproducibility and a linear dependence on the concent
ration of H2S over fairly wide ranges, as well as by a short response
time (ca. 0.5 s to attain a 95% response). This fast response time ari
ses from the lack of a gas-permeable membrane and direct gas contact t
o the triple interphase among the gaseous analyte, the porous working
electrode, and the solid polymer electrolyte. The absence of any effec
t due to the most important potential interfering species and the poss
ibility of adopting such a device for the direct detection of H2S in a
mbient air and for industrial hygiene measurements are discussed.