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Influence of ascorbic acid on the matrix interferences observed during the carbon furnace atomic-absorption spectrophotometric determination of lead in some drinking waters.

Nine samples of drinking water taken from a range of locations in England and Scotland have been analysed for lead by using carbon furnace atomic-absorption spectrophotometry. Spiking experiments have been carried out in order to determine the severity of the matrix interference. The suppression of the lead signals ranged from 22 to 84%. No relationship was found to exist between the hardness of a water sample and its suppression effect.Further spiking experiments carried out in the presence of 1%m/V of ascorbic acid showed that the suppression effect of eight of the water samples was reduced to a level of less than 5%. The remaining water sample gave a suppression of 18%. This water was not the hardest examined, nor did it give the highest suppression in the previous experiment.The natural lead contents of the nine waters were determined both by carbon furnace atomic-absorption spectrophotometry in the presence of ascorbic acid and by a method that involves solvent extraction-flame atomic absorption. Statistical analysis, using a t-test, indicated that there was no significant difference (at the 95% confidence level) in the results obtained by using the two techniques.