COUPLED IN-SITU ELECTRODEPOSITION-ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY - A NEW APPROACH IN QUANTITATIVE MATRIX FREE ANALYSIS

A new approach for in situ matrix elimination in electrothermal atomic absorption spectroscopy (ETAAS) is described. In an initial electrodeposition step (possible by use of a Pt/Ir delivery tube on the autosampler) the furnace is coated with about 0.25 mu g Pd. Quantitative deposition of metallic analytes onto this renewable substrate is achieved from 25-40 mu l samples by electrolysis for 60 s at 3.5-5.0 V (35-45 mA). Reprogramming of the autosampler to remove spent electrolyte after the electrolyses and to provide a rinse cycle facilitates removal of >99.5% of a 0.5 M NaCl matrix prior to atomization. It is proposed that the analyte is bound onto the metallic modifier, rather than encapsulated within it. Binding of the analyte with Pd significantly increases the appearance temperature for Cd and Pb. The ashing loss for these analytes deposited onto Pd from a Cl- matrix is observed above 900 degrees C and 1300 degrees C, respectively. This stabilization facilitates separation of the residual NaCl matrix before atomization. It has been established for Cd that sensitivity of the determination remains constant for matrices as diverse as 1% HNO3, 0.5 M NaCl and sea water.