Feasibility of ion-exchange solid phase extraction inductively coupled plasma mass spectrometry for discrimination between inorganic As(III) and As(V) in phosphate-rich in vitro bioaccessible fractions of Ayurvedic formulations

Highlights: • Determination of potentially toxic elements in several Ayurvedic formulations • Health risks due to As levels in bioaccessible fractions of Ayurvedic products • Twenty-five times larger estimated As intake than BMDL₀₅ from mineral formulations • Arsenic discrimination in phosphate-rich bioaccessible fraction by ion-exchange SPE • Estimation of As(III)/As(V) conversion in formulations with large As concentration -- Abstract: Determination of potentially toxic elements in the μg/kg–mg/kg concentration range in some Ayurvedic formulations was performed after microwave-assisted acid digestion and inductively coupled plasma mass spectrometry. Arsenic and Hg concentration in the mineral formulations reached about 10% and 0.6% by weight, respectively. Arsenic bioaccessibility was not influenced by pepsin and pancreatin containing model suspensions of pH = 1.2 and 6.8 (with 0.05 M K₂HPO₄), respectively. The bioaccessible As fraction of the mineral formulations was about 10–20%, even if the estimated As intake from these products exceeded the 3.0 μg/BW kg/day benchmark dose limit with an increased incidence of 0.5% for lung cancer (BMDL₀₅) caused by inorganic As by about 25 times. Ion-exchange solid phase extraction procedure was applied to discriminate between iAs species in either the initial bioaccessible fractions obtained by incubation in simulated duodenal juice or by spiking them with 75 and 150 μg/L arsenate ions [iAsV]. The complex sample/extractant matrix caused a 60–70% recovery for iAs(V) and a breakthrough of about 20%. Suppression of phosphate ions in the extractant improved iAs(V) recovery by about 10%. Arsenic breakthrough was not observable at the 75 μg/L iAs(V) spike level. Similar results were obtained on a homeopathic product confirming the interference of phosphate on As speciation in bioaccessible fractions of complementary and alternative medicines (CAMs). Conversion rate of iAs(III)/iAs(V) in Ayurvedic products with large As content could be estimated. This approach is more informative than extrapolation of results by X-ray based techniques on solid state of CAMs.