Screening of Toxic Inorganic Arsenic Species in Garlic (Allium sativum L.)

Abstract

It has been evidenced that arsenic in garlic is present in the most toxic inorganic species As(III) and As(V). A non-chromatographic speciation method has been developed for the screening of inorganic toxic species of As in garlic samples by hydride generation atomic fluorescence spectrometry. The determination of As(III) and As(V) was based on the different efficiencies of hydride generation with NaBH₄ with and without a previous reduction with ascorbic acid and KI using a system of two proportional equations corresponding to these two different measurement conditions. The extraction efficiency of total arsenic and the stability of As(III) and As(V) in different extraction media (sulphuric acid, perchloric acid, and methanol/water) were evaluated. Based on the extraction yield and the stability of extracted species, 1.0 mol L⁻¹ H₂SO₄ was selected as the best extracting solution for speciation analysis. The methodology developed allows us a limit of detection of 0.8 and 0.6 ng g⁻¹ for As(III) and As(V), respectively. The relative standard deviation values were 4% for As(III) and 7% for As(V). This method was applied to determine As(III), As(V), and total As in different Spanish garlic samples. The arsenic (III) content varied from 17.1 to 22.1 ng g⁻¹ and As(V) from 54.7 to 67.6 ng g⁻¹. The accuracy of the method was confirmed by the analysis of a certified reference material of tomato leaves treated in the same way as the garlic samples.