Mercury detection in air using a coated piezoelectric sensor

Three different methods to produce standardized vapors of mercury were tested and compared for posterior determination of metal, using a piezoelectric sensor (QCM). The generation techniques employed were: saturation, syringe dilution and permeation tube. Gold-coated piezoelectric crystals, without any substrate, were initially tested as sensor, based on the selective affinity of gold by mercury. Later, using a permeation tube as source of metal, some substances were investigated as possible substrates capable of interaction with mercury vapor. The best material found was a mixture (1 : 1 v/v) of palladium-II chloride solution (saturated in acetone) and tetrahydroxyethylethylenediamine (THEED) 50% v/v in acetone. The analytical curve is linear in the concentration range from 2.0 to 7.0 ppm of Hg. Good linearities (r = 0.9952 and 0.9979) and sensitivities (102 and 149 Hz/ppm) were found for exposure times of 20 and 40 s, respectively. it was shown that the technique has potential application as a small, rugged, sensible and portable mercury vapor sensor. (C)2000 Elsevier Science B.V. All rights reserved.