A new scheme for trace determination of chromium using electrothermal atomization-laser induced fluorescence spectrometry

Abstract

The determination of chromium (Cr) in water, gastrointestinal perfusates and serum samples by laser induced fluorescence in an electrothermal atomizer (ETA-LIF) has been investigated. Laser radiation used to excite Cr at 236.471 nm is generated by frequency doubling the output of a tunable dye laser. Fluorescence emissions are observed at 302.2 nm or 357.9 nm. Due to the low transition probability of the Cr excitation transition, excitation is performed using laser pulse energies of approximately 100 µJ per pulse. Atomization is performed in a commercial graphite furnace using pyrolytically coated graphite tubes without L'vov platforms. The optimized temperatures for ashing and atomization have been found to be 1300 °C and 2500 °C, respectively. The limit of detection for Cr in water by the ETA-LIF technique is 80 fg, which corresponds to 4 pg mL−1 in 20 µL sample volumes. The analytical approach has been utilized for the determination of Cr in biological fluids. Prior to analysis, gastrointestinal perfusate solutions and serum samples were diluted 1 + 1and 1 + 49, respectively, using 18 MΩ deionized water. The analysis of these samples has been evaluated using two different matrix modifiers [25 µg per 10 µL Mg(NO3)2 and 2% TritonX-100] and without a matrix modifier.