Development of a matrix-matched standard for the elemental analysis of human hair by LA-ICP-MS

Abstract

Human hair as a biological matrix presents a detailed distribution profile of organic and inorganic components in the body. In comparison to blood and urine, hair introduces great advantages as it provides a temporal record with growth and longer detection window of analytes. Elemental analysis by LA-ICP-MS has been studied using different strategies for standards, however there is not a reference material that reproduces the physical and chemical properties of hair. This work demonstrates the development of a matrix-matched calibration standard using a keratin film doped with metals of interest for LA-ICP-MS analysis. The material was synthesized from extracted human hair keratin using the “Shindai method”, purified, spiked, and cross-linked to obtain a thin homogenous film. A series of calibration standards were prepared for trace concentrations of Ba, Pb, Mo, As, Zn, Mg, and Cu. Linear calibration models were built with limits of detection as low as 0.43 μg g⁻¹ for Pb. The material was characterized by its thickness, homogeneity, and matrix-matching compared to human hair. The calibration materials were cross evaluated with spiked single human hairs for verification. These results provide a new set of standards for LA-ICP-MS to be used in internal medicine, forensic toxicology, and biological anthropology.