A low-cost tungsten filament atomizer for measuring lead in blood by atomic absorption spectrometry

Abstract

A low-cost electrothermal atomic absorption spectrometry (AAS) system based on a tungsten filament atomizer is proposed for the measurement of blood lead. Preliminary experiments have been carried out using a tungsten filament enclosed in a glass cell, purged with argon and 10% H 2, and mounted on the optical bench of a commercial atomic absorption spectrometer with continuum background correction. The tungsten filament is ballistically heated with a 12 V d.c. power supply. A number of parameters, including filament position, gas flow, drying, pyrolysis and atomization steps, are optimized specifically for blood lead. Peak absorbance is the measurement mode used because of the very fast signals observed. The atomizer is calibrated with aqueous lead standards, and the calibration verified by analyzing blood lead reference materials from NIST, CDC and NYS, that cover the clinical range for blood lead (5–54 μg dl −1). Results below 40 μg dl −1 are within ±2 μg of the certified value, and within ±10% of the certified value above 40 μg dl −1, indicative of good accuracy especially at the lower blood lead levels. Blood is prepared by diluting 1 + 9 with modifier. Ten microliters of diluted blood is deposited on the filament using a micropipet. Forty-two human blood specimens covering the range 3–31 μg dl −1 are analyzed in parallel with a well established graphite furnace AAS method. There is good agreement between the two AAS methods, and the differences between individual paired blood lead results are less than ±4 μg. The sensitivity or characteristic ( m o) of the tungsten filament atomizer is 26 pg, and the method detection limit (3 SD) is about 2 μg dl −1.