Determination of heavy metals in shellfish by flame atomic absorption spectrometry and inductively coupled plasma atomic emission spectrometry

Abstract

Shellfish samples (clams, oysters and mussels) were analysed for Pb, Cd, Cu, Cr, Zn and Ni by flame atomic absorption spectrometry (FAAS) and inductively coupled plasma atomic emission spectrometry (ICP-AES) following wet-ash digestion. Split samples were taken for both FAAS and ICP-AES analysis. Vanadium was used as the internal standard for ICP-AES whereas 1.25% NaCl was added to the FAAS standards to correct for the high salt background associated with shellfish.

The methods were compared for statistical significance using regression analysis, the F-test and Student's t-test. Precision and accuracy were determined by replicate analyses, recovery of added heavy metals and National Bureau of Standards (NBS) reference materials. Results obtained from regression analysis for the coefficient of determination or “goodness of fit” were all above the acceptable 0.80 level. The t-test showed that the methods were statistically similar for all metals tested at the 95% confidence level. Average percentage recoveries ranged from 80.2 to 100.7%. Heavy metals were added at approximate expected levels normally found in the shellfish.

Accuracy, based on heavy metal levels determined by FAAS and ICP-AES versus certified values for NBS reference materials, varied with the individual reference materials tested. The over-all data obtained indicated that FAAS and ICP-AES showed good agreement for the determination of the heavy metals tested, ICP-AES providing a drastic reduction in analysis time following initial sample work-up.