Signal suppression is a common problem in quantitative LC-ESI-MSn analysis in environment samples, especially in highly loaded wastewater samples with highly complex matrix. Optimization of sample preparation and improvement of chromatographic separation are prerequisite to improve reproducibility and selectivity. Matrix components may be reduced if not eliminated by a series of sample preparation steps. However, extensive sample preparation can be time-consuming and risk the significant loss of some trace analytes. The best way to further compensate matrix effects is the use of internal standard for each analyte. However, in a multi-component analysis, finding appropriate internal standards for every analyte is often difficult. In this present study, a more practical alternative option was sought. Matrix effects were assessed using a post-extraction addition method. By comparison of three different calibration approaches, it was found that matrix-matched calibration combined with one internal standard provides a satisfactory method for compensating for any residual matrix effects on all the analytes. Validating experiments on different STP influent samples analysing for a range of phytoestrogens showed that this calibration method provided satisfactory results with concentration ratio 96.1% – 105.7% compared to those by standard addition. It is an easy practical calibration approach to compensate matrix effects in the multi-component LC-ESI-MSn quantitative analysis.
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