Highly accurate determination of Zn and Cu in human hair by ultrasound-assisted alkali dissolution combined with laser-induced breakdown spectroscopy

Abstract Hair is an ideal biomarker for monitoring human health and environmental risks through the determination of trace elements in the hair. However, accurately quantifying trace elements in hair using laser-induced breakdown spectroscopy (LIBS) is a big challenge. A simple and low-cost method, ultrasound-assisted alkali dissolution (UAAD), was proposed for quantifying trace elements in human hair. In this work, three different solvents (deionized water, nitric acid mixture, and sodium hydroxide) were used to dissolve the hair assisted by ultrasound; and then the hair solution was dripped onto filter paper. The effect of alkali dissolution on enhancing the spectral intensity of zinc (Zn) and copper (Cu) was then analyzed. Using ultrasound-assisted alkali dissolution combined with laser-induced breakdown spectroscopy (UAAD-LIBS), the limits of detection (LoDs) for determining Zn and Cu elements can reach to 0.3517 μg/g and 0.0146 μg/g, respectively. Based on this simple method with low LoDs, the quantitative analysis results of LIBS for three actual samples were compared with inductively coupled plasma optical emission spectrometry (ICP-OES). The relative errors of Zn and Cu between UAAD-LIBS and ICP-OES were less than 7.6% and 4.9%. These results show that using UAAD as a sample pretreatment process is an effective method of LIBS analysis.