Multi-isotope calibration strategy for trace elements determination in whole blood by inductively-coupled plasma mass spectrometry

Abstract

This study proposes the multi-isotopic calibration strategy (MICal) for determining Cd, Cr, Hg, Mo, Ni, Pb, Se, Sn, and Zn in whole blood samples by inductively coupled plasma mass spectrometry. Isotopes were monitored in only two solutions: A: (5 % (v/v) sample + 95 % (v/v) standard) and B (5 % (v/v) sample + 95 % (v/v) blank). Different standard concentrations were tested within MICal to improve linearity (R² > 0.95), enhancing model robustness. Calibration curves were built by plotting signals from solutions A and B on the x and y axes, respectively. Analyte concentrations were determined from the slope and standard concentrations in solution A. Slopes near 0.5 were achieved, and ANOVA and Tukey’s test assessed significant differences. MICal has the unique advantage of identifying spectral interferences by observing outlier values in the calibration curve, which were detected for Cr, Ni, and Se. MICal exhibited superior performance compared to external calibration (EC) and standard addition (SA) for Cr, Hg, Mo, Sn, and Zn, achieving improved sensitivity and accuracy. Additionally, MICal uniquely enables the identification of spectral interferences by detecting outliers in the calibration curve, as observed for Cr, Ni, and Se. The method demonstrated low limits of quantification (LOQ) and agreement values within an acceptable range, comparable to the SA strategy, which is typically used for complex matrices. MICal is a robust and efficient calibration approach for whole blood analysis, offering advantages such as reduced analysis time, lower cost, simplicity, and interference detection.