Simultaneous determination of Fe and Zn in dried blood spot by HR-CS GF AAS using solid sampling

Abstract

Dried Blood Spot (DBS) was evaluated as a solid sampling (SS) strategy for the simultaneous determination of Fe and Zn in blood samples by Solid Sampling High-Resolution Continuum Source Graphite Furnace Atomic Absorption Spectrometry (SS HR-CS GF AAS). The alternative lines of Fe and Zn at 307.572 and 307.589 nm, respectively, were evaluated. A good correlation between the area of DBS (in mm2) and volume of blood (in µL) was observed up to 200 µL of blood. A 3.4 mm diameter paper disk, equivalent 3.86 ± 0.13 µL, was punched from the DBS and employed for blood analysis. Random sampling through the area of the paper circle produced by 50 μL blood samples showed no chromatographic effects. The upside of the solid sampling 'boat type' graphite platform was coated with a W-based film. This coating allowed around 350 firings. The use of 3 µL of 15% v/v H2O2 solution as chemical modifier improved both the thermal stability and peak profile of Zn for aqueous medium (standard solution deposited onto Whatman paper), possibly because of the weakening of Zn-paper interactions or even by the formation of thermally more stable Zn oxides. Solid standards used for calibration in the 0.1–3.0 µg Fe and 5.0–50.0 ng Zn ranges were prepared with Whatman 903® paper discs impregnated with standard solutions of the analytes. Results for Fe and Zn determined by the proposed SS HR-CS GF AAS method were in agreement at a 95% confidence level (paired t-test) with those obtained by the comparative method (except for one sample) based on microwave-assisted acid digestion of blood and High-Resolution Continuum Source Flame Atomic Absorption Spectrometry (HR-CS F AAS). The limits of quantification were 10.2 mg/L (0.04 µg) for Fe and 1.2 mg/L (4.6 ng) for Zn. The relative standard deviation was < 10% (n = 12) for a sample containing 516 mg/L Fe and 8.7 mg/L Zn, and the sample throughput was equivalent to ca. 90 s per measurement.