PRESERVATION OF SOLID MERCURIC DITHIZONATE SAMPLES WITH POLYVINYL-CHLORIDE FOR DETERMINATION OF MERCURY(II) IN ENVIRONMENTAL WATERS BY PHOTOCHROMISM-INDUCED PHOTOACOUSTIC SPECTROMETRY

A novel sample preparation technique has been developed to preserve so lid mercuric dithizonate [Hg(HDz)2] in a matrix of polyvinyl chloride (PVC) for analysis by photochromism-induced photoacoustic spectrometry (PCPAS). This technique, which begins with the extraction of Hg2+ fro m water with dithizone, allows for the determination of Hg2+ in enviro nmental samples. Inclusion of Hg(HDz)2 within the polymer matrix enhan ces the PCPAS signal amplitude over that from the bare Hg(HDz)2 film b y almost sixfold. The standard calibration graph of PCPAS signal ampli tude as a function of Hg2+ concentration is linear in the concentratio n range of 5-100 mug/ml. A lower detection limit can be achieved by us ing a laser of higher power tuned to a wavelength closer to the maximu m absorptivity of the excited Hg(HDz)2 complex. A study, conducted to monitor the change in PCPAS signal amplitude obtained for the same sam ple over an extended storage period of 19 days, demonstrates that the PVC protects the integrity of the solid Hg(HDz)2 sample. Hence, it is potentially feasible to collect environmental samples from a remote ar ea for analysis at a later date.