Development of an electrothermal atomization laser excited atomic fluorescence spectrometry procedure for direct measurements of arsenic in diluted serum

A procedure for the direct determination of arsenic in diluted serum by ele ctrothermal atomization laser-excited atomic fluorescence spectrometry (ETA -LEAFS) is reported. Laser radiation needed to excite As at 193.696 and 197 .197 nm is generated as the second anti-Stokes stimulated Raman scattering output of a frequency-doubled dye laser operating near 230.5 and 235.5 nm, respectively. Two different LEAFS schemes have been utilized and provide li mits of detection of 200-300 fg for As in aqueous standards. When measureme nts of serum samples diluted 1:10 with deionized water are performed, a sta ble background signal is observed that can be accounted for by taking measu rements with the laser tuned off-wavelength. No As is detected in any of th e bovine or human serum samples analyzed. Measurements of 100 pg/mL standar d additions of As to a diluted bovine serum sample utilizing either inorgan ic or organic As species demonstrate a linear relationship of the fluoresce nce signal to As spike concentration, but exhibit a sensitivity of approxim ately half that observed in pure aqueous standards. The limit of detection for As in 1:10 diluted serum samples is 65 pg/mL or 650 fg absolute mass, w hich corresponds to 0.65 ng/mL As in undiluted serum. To our knowledge, the ETA-LEAFS procedure is currently the only one capable of directly measurin g As in diluted serum at these levels.