Evaluation of an internal standard-free laser ablation-ICP-OES method for elemental analysis in solid food samples

Although the laser ablation-inductively coupled plasma-optical emission spectrometry (LA-ICP-OES) is a promising method for the elemental screening of solid food materials, the main challenge associated with this technique is the lack of commercial solid standard reference materials to serve as the external standard for quantitative calibration. In this study, a reliable internal standard-free LA-ICP-OES method for direct sampling and analysis of solid food materials was developed. The method relies on the carbon internally-standardized relative sensitivity factor (CIS-RSF) was developed, eliminating the need for calibration curves or matrix-matched external standards once the CIS-RSF has been determined. After careful evaluation of the effect of the instrumental operating parameters on the long-term stability of CIS-RSFs, this method was used to analyze a variety of microelements, including sulfur (S), phosphorus (P), zinc (Zn), iron (Fe), manganese (Mg), magnesium (Mn), copper (Cu), calcium (Ca), strontium (Sr), barium (Ba), sodium (Na), and potassium (K), with the limit of quantitation (LOQ) ranging from 0.06 (Sr) to 400 mu g g-1 (S). The accuracy and reproducibility of this proposed method were evaluated through the analysis of three food NIST reference materials and six typical food samples. The results indicated that the relative error of most target elements was less than 20% and the reproducibility (SD, n = 3) more than 10%. This developed LA-ICP-OES screening method has great potential for the high-throughput multielement determination of various solid food materials.