Unified analysis method for total and inorganic As determination in foodstuffs by hydride generation high-resolution continuum source quartz tube atomic absorption spectrometry

Abstract

A unified analytical method applicable to common foodstuff matrices was developed and characterized for total and inorganic arsenic determination by hydride generation high-resolution continuum source quartz tube atomic absorption spectrometry, which was established based on different sample preparation procedures. This new method was found to be interference-free and cost-effective in terms of reagents consumption for sample preparation and derivatization to arsine for the inorganic arsenic fraction. Microwave-assisted digestion in HNO₃–H₂O₂ for total arsenic and extraction in 0.28 mol L⁻¹ HNO₃ by mechanical stirring in a water bath or ultrasound-assisted extraction in 0.01 mol L⁻¹ HCl without separation of inorganic As, all coupled with arsine generation in 0.01 mol L⁻¹ HCl medium with 0.6% NaBH₄ in 0.01% NaOH in the presence of 0.2% L-cysteine was found to be suitable for all matrices. The results were statistically compared by applying Tukey's and Dunnett's multiple comparison methods (p > 0.05). The use of external calibration with As(III) standards and standard addition method for quantification showed the lack of non-spectral interferences from the multimineral matrices, resulting in a reliable method for total/inorganic As determination in various foodstuffs. The limits of detection for total/inorganic As using peak height measurement were 0.0044 ± 0.0005/0.0022 ± 0.0003 mg kg⁻¹ (n = 25 days). The overall recovery for total/inorganic As in the certified reference materials was in the range of 98% ± 22%, and 99% ± 24% (k = 2). The extraction of inorganic As in 0.01 mol L⁻¹ HCl and 0.28 mol L⁻¹ HNO₃ provided the recovery of 106% ± 25% and 100% ± 25% (k = 2), which was better than in 10 mol L⁻¹ HCl. The precision of measurements in real samples of fish muscle, meat and organs, rice and rice-based baby foods with contents of 0.052–5.29 mg kg⁻¹ total As and 0.005–0.063 mg kg⁻¹ inorganic As was 9.8–18.8% and 8.7–32.0%, respectively, which was calculated based on the combined uncertainty.