Determination of major and trace elements in human scalp hair by pressurized-liquid extraction with acetic acid and inductively coupled plasma–optical-emission spectrometry

摘要

An analytical method has been developed for determination of major (Ca, K, Mg, and Na) and trace elements (As, Cd, Co, Li, Ni, and Sr) in human scalp hair. The proposed method includes a novel, simple, rapid, highly efficient, and automated metal-leaching procedure, by pressurized-liquid extraction (PLE), combined with a rapid simultaneous detection system—inductively coupled plasma–optical-emission spectrometry (ICP–OES). PLE is one of the most promising recently introduced sample-preparation techniques, with the advantages of reducing solvent consumption and enabling automated sample handling. The operating conditions for PLE, including concentration of the extraction solvent, extraction temperature, static time, number of extraction steps, pressure, mean particle size, diatomaceous earth (DE) mass/sample mass ratio, and flush volume were studied using an experimental design (Plackett–Burman design, PBD). The optimum conditions were use of 0.75 mol L−1 acetic acid as extracting solution and powdered hair samples thoroughly mixed with DE, as a dispersing agent, at a DE mass/sample mass ratio of 4. Extraction was performed at room temperature and an extraction pressure of 140 atm for 5 min in one extraction step. The flush volume was fixed at 60%. The PLE-assisted multi-element leaching proposed is complete after 7 min (5 min static time plus 1 min purge time plus 1 min end relief time). Under the optimised conditions the figures of merit, for example limits of detection and quantification, repeatability of the over-all procedure, and accuracy, were evaluated. Analysis of GBW-07601 (human hair) certified reference material revealed accuracy was good for the target elements. The optimised method was finally applied to several human scalp-hair samples.