Determination of cadmium in urine specimens by graphite furnace atomic absorption spectrometry using a fast atomization program

A simple, fast, and reliable method was developed for the determination of cadmium in urine specimens by graphite furnace atomic absorption spectrometry (GFAAS). The method involved dilution (1:1) of the specimens with a 4.0% HNO₃, direct injection of a 10 μl aliquot of the corresponding solution into a hot transversely-heated graphite atomizer (110 °C), and application of a fast atomization program (42 s) in which the conventional dry-pyrolysis sequence was substituted by a high-temperature (300 °C) drying step. The effect of the injection temperature (A), injection rate (B), pyrolysis’ ramp (C) and hold (D) times over the analyte’s integrated absorbance, peak-shape and repeatability of the measurements was evaluated by means of a 2^4-1 fractional factorial design. All those individual variables, as well as their first-order interactions (AB-, AC- and AD-type interactions) were found to exert a statistically significant effect (P<0.05). The lack of a chemical modifier other than the nitric acid itself benefited the overall methodology by allowing low-temperature atomization (1200 °C), enhanced atomic and background signals separation, and reduced blank values. A detection limit (3s, n=20) of 0.06 μg l⁻¹ Cd, corresponding to 0.12 μg l⁻¹ Cd in the urine specimen, and a characteristic mass of 1.78 pg/0.0044 s were obtained under the optimized conditions. The standard calibration technique (SCT) was used for quantitation. The successful determination of cadmium in Seronorm™ Trace Elements Urine Batch No. 115 (Nycomed Pharma AS) and in four urine specimens from volunteer donors (recoveries: 91.3-103.4%) attested to the robustness of the proposed method.