COMPARATIVE-STUDY ON THE USE OF IR, W AND ZR-COATED GRAPHITE TUBES FOR THE DETERMINATION OF CHROMIUM IN SLURRIES OF HUMAN SCALP HAIR BY ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY

The use of Ir, W and Zr-coated graphite tubes, as permanent chemical m odifiers, was studied for the determination of chromium in human scalp hair by ETAAS using the slurry sampling technique. The use of Mg(NO3) (2) and Pd, as aqueous chemical modifiers, was also investigated and c ompared to the use of the permanent chemical modifiers. Scalp hair sam ples were pulverized using a Zr vibrational ball mill, (mean particle diameter of 0.8 mu m) and suspended in ultrapure water. The lowest lim it of detection, 44.5 mu g kg(-1),was achieved for the use of W-coated graphite tubes. The repeatability of the overall procedures (slurry p reparation and ETAAS determination) were 15.7, 14.5 and 16.7% for W-an d Zr-coated graphite tubes and Mg(NO3)(2), respectively. The methods w ere applied to several reference materials, CRM 397 (human hair), DOLT -1 (dogfish liver) and DORM-1 (dogfish muscle), and the results obtain ed were in agreement to the certified values. Finally, the methods wer e applied to several human scalp hair samples from healthy adults.