Semi-permanent lutetium modifier for the determination of beryllium in urine by electrothermal atomic absorption spectrometry

The determination of beryllium using electrothermal atomic absorption spect rometry with deuterium background correction in the presence of various iso morphous metals and Mg(NO3)(2) was studied. While, Eu, Ir and Sm had no eff ect on the transient signals, the addition of Lu and Mg(NO3)(2) improved th e sensitivity of the beryllium signal with respect to that obtained in the absence of modifier. Although, Mg(NO3)(2) has improved the signal with resp ect to its sensitivity, it also increased the tail and the background (BG) signals, specially when urine samples are under study. Whereas, when Lu was used the analytical signal is virtually free of BG interference indicating that the urine matrix interference was almost eliminated. Besides, the add ition of 6 mu g of Lu ensured that the signals were effectively constant fo r five firings following the furnace program, which included: three drying, and the pyrolysis, atomization, cleaning and cooling steps. The effect of some components, likely to interfere in the accurate determination of beryl lium (such as: Al, Ca, Cl, Co, Cr, Fe, Mg and Mn) were investigated. At the physiological levels, most of these elements had no effect, except in the case of chloride when Mg(NO3)(2) was used as modifier. In this case, the to lerance limit was of 3000 mg Cl- l(-1). The characteristic masses were 1.19 , 0.45 and 0.48 pg, when integrated absorbance was measured for beryllium w ithout the addition of any modifier and in the presence of Lu and Mg(NO3)(2 ), respectively. The limits of detection (3 sigma) were 85, 19 and 58 fg, r espectively. The accuracy and precision with the use of Lu and Mg(NO3)(2) w as tested for the direct determination of beryllium in urine samples. Quant ification was performed with aqueous standards. The results obtained for th e determination of beryllium in reference materials (Trace Elements in Urin e), together with good recovery of spiked analyte, using either Lu or Mg(NO 3)(2) modification demonstrate the applicability of the procedure to the an alysis of real samples. However, Lu provided the most accurate results. Als o, the addition of Lu enhanced the precision of the measurements to levels of 1.8% relative standard deviation instead of 5.6 and 3.3% for the case of beryllium alone and with the addition of Mg(NO3)(2). (C) 1999 Elsevier Sci ence B.V. All rights reserved.