AUTOMATIC-DETERMINATION OF MERCURY IN SAMPLES OF ENVIRONMENTAL INTEREST

An automatic flow injection (FI) system for the determination of mercu ry was developed using a commercial Gold vapour atomic absorption spec trophotometer (CVAAS). Control and data acquisition in the FI system w as done with an IBM-PC 286 XI compatible microcomputer and a home-made interface, using software written in QuickBasic 4.5. Mercury content was determined by: sampling using a combination of four electromechani cal three-way poly(tetrafluoroethylene) valves; separation of the diss olved reduced mercury in a gas/liquid separation cell using nitrogen a s carrier, followed by amalgamation of the stripped metal on a gold wi re column; after stripping the metal, cleaning the separation cell usi ng vacuum, which was controlled by a three-way electromechanical valve ; heating the gold wire column automatically to release the amalgamate d mercury using an external nichrome wire coil; storing the output sig nals automatically to calculate the final mercury concentration, using commercially available software. The optimized system presents a dete ction limit of 5.3 ng l(-1) of mercury (30 pg absolute) using 5.7 ml ( three injections of 1900 mu l of the sample) with an analytical freque ncy of six samples per hour and reproducibility of 5%. The procedure w as used to determine mercury in fish, hair and natural water samples.