Determination of lead and cadmium in ceramicware leach solutions by graphite furnace atomic absorption spectroscopy: Method development and interlaboratory trial

Abstract

This method was developed to improve sensitivity and eliminate time consuming, evaporative pre-concentration in AOAC Method 973.82 and American Society for Testing and Materials method C738 for testing foodware. The method was developed using leach solutions obtained by leaching 9 differently decorated ceramic vessels with 4% acetic acid for 24 h at room temperature. Lead and cadmium concentrations in leach solutions were 0.005-17 600 and 0.0004-0.500 μg/mL, respectively. Concentrations were determined using peak area, phosphate chemical modifier (8.3 μg PO4-3), and a standard curve for quantitation. Optimized pre-atomization and atomization temperatures were 1300 and 1800°C, respectively, for Pb and 1100 and 1700°C, respectively, for Cd. Characteristic masses (mo) were 10 and 0.4 pg for Pb and Cd, respectively. Precision of repeated analyses of calibration solutions was <3% relative standard deviation. Precision of duplicate leach solution analyses on different days was 0-9% relative difference. Recovery from fortified leach solutions was 96-106%. Results obtained by this method agreed 92-110% with those of confirmatory analyses. Results of certified reference material solutions agreed 94-100% with certificate values. Pb and Cd limits of quantitation (LOQ) were 0.005 and 0.0005 μg/mL, respectively. Results from 3 trial laboratories for 4 leach solutions containing Pb and Cd concentrations of 0.017-1.47 and <0.0005-0.0864 μg/mL, respectively, agreed 89-102% with results of the author. Two attributes of this method were noteworthy: (1) Background absorbance due to organic matter was entirely absent from atomization profiles, making the use of short pre-atomization hold times (2 s) possible. (2) Instrument precision was excellent and only one determination per solution was needed. Acceptance criteria for quality control measurements and a practical procedure for estimating the method LOQ during routine regulatory analyses are described.