Determination of Boron in Blood, Urine and Bone by Electrothermal Atomic Absorption Spectrometry Using Zirconium and Citric Acid as Modifiers

摘要

A comparative study of various potential chemical modifiers (Au, Ba, Be, Ca,Cr, Ir, La, Lu, Mg, Ni, Pd,Pt,Rh, Ru, Sr, V, W, and Zr) and different 'coating' treatment (Zr, W, and W + Rh) of the pyrolytic graphite platform of a longitudinally heated graphite tube atomizer for thermalstabilization and determination of boron was undertaken. The use of Au, Ba, Be, Cr, Ir, Pt, Rh, Sr and V as modifiers, and W + Rh coating produced erratic, and noisy signals, while the addition of La, Ni and Pd as modifiers, and the W coating had positive effects, biu with too high background absorption signals, rendering their use unsuitable for boron determination even in aqueous solutions. The atomic absorption signal for boron was increased and stabilized when the platform was coated with Zr, and by the addition of Ca, Mg, Lu, W or Zr as modifiers. Only the addition of 10 #mu#g of Zr as a modifier onto Zr-treated platforms allowed the use of a higher pyrolysis temperature without analyte losses. The memory effect was minimized by incorporating a cleaning step with 10 #mu#l of 50 g l~(-1) NH_4F HF after every three boron measurements. The addition of 10 #mu#l of 15 g l~(-1) citric acid together with Zr onto Zr-treated platforms significantly improved the characteristic mass to m_0 = 282 pg, which is adequate for biological samples such as urine and bone, although the sensitivity was still inadequate for the detemrination of boron in blood of subjects without supplementary diet. Under optimized conditions, the detection limit (3#sigma#) was 60 #mu#g l~(-1). The amount of boron found in whole blood, urine and femur head samples from patients with osteoporosis was in agreement with values previously reported in the literature.