STUDIES OF CRITICAL FACTORS IN THE DETERMINATION OF ARSENIC IN STANDARD REFERENCE MATERIALS OF MARINE ORIGIN BY ETAAS-NMKL INTERLABORATORY STUDY

A study to determine factors which are known to influence the electrot hermal atomic absorption (ETAAS) determination of As has been performe d. The study has been carried out using five sample solutions of marin e Standard Reference Materials distributed to four participating labor atories. Uncoated and pyrolytically coated graphite tubes with L'vov p latform and Ni and Pd/Mg as chemical modifiers have been tested. No di fferences in results have been obtained between AAS instruments equipp ed with Zeeman correction or deuterium are background correction. Smal l differences in concentration levels of arsenic as well as in charact eristic mass were found when chemical modifiers were compared. Pd/Mg w ill be recommended in order to avoid a contamination of the graphite f urnace with nickel. The characteristic mass was improved by using pyro lytically coated graphite tubes with the L'vov platform compared with uncoated graphite tubes with the L'vov platform. In the interlaborator y study, the standard addition procedure will be recommended.