High-sensitivity determination of trace lead and cadmium in cosmetics using laser-induced breakdown spectroscopy with ultrasound-assisted extraction

Cleaner cosmetic production is crucial to our health. The detection of heavy metals in cosmetics is a hotspot in the past several years. Apart from the conventional analytical methods, laser-induced breakdown spectroscopy (LIBS) was recently applied as a rapid technique for trace heavy elements determination. However, the sensitivity obtained from the reported works do not, or marginally reach, the heavy metals standards in cosmetics required by regulatory bodies. Therefore, the sensitivity of LIBS still needs improvement to meet the standards. For this purpose, we developed an ultrasound-assisted extraction sample pretreatment method (UAE) for LIBS to detect the trace heavy metals lead (Pb) and cadmium (Cd) in low-quality cosmetics. A standard addition method was employed for elemental quantification by adding known amounts of analytes into the extracted solutions. Then, the calibration curves of Pb and Cd were established with good linearity. The limit of detections (LOD), ranging from 0.028 mg/kg (Pb) to 0.016 mg/kg (Cd), demonstrated the high-sensitivity of our work. Moreover, compared with the results by inductively coupled plasma mass spectrometry (ICP-MS), the LIBS indicated promising accuracy as the relative errors (RE) of Pb and Cd were 3.5% and 4.8%, respectively. The results indicated that the LIBS with UAE method is a sensitive and accurate technique for trace heavy metals determination in cosmetics.