Determination of lithium at ultratrace levels in biological fluids by flame atomic emission spectrometry. Use of first-derivative spectrometry.

The use of zero-order and first-derivative flame emission spectrometry has been investigated for the determination of basal concentrations of lithium in serum and urine at the microgram dm-3 level. No significant matrix effect was observed; however, it was necessary to make use of background correction techniques. Two or three wavelength measurements and first-derivative spectrometry were used for this purpose; both methods gave similar results. Detection limits for serum of approximately 0.09 micrograms dm-3 were found by both zero-order and first-derivative emission measurements, while normal lithium levels were found to be 29.3 and 1.17 micrograms dm-3 for urine and serum, respectively.