Using calibration approaches to compensate for remaining matrix effects in quantitative liquid chromatography/electrospray ionization multistage mass spectrometric analysis of phytoestrogens in aqueous environmental samples

Abstract

Signal suppression is a common problem in quantitative liquid chromatography/electrospray ionization multistage mass spectrometric (LC/ESI-MS(n)) 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 are reduced if not eliminated by optimization of sample preparation steps. However, extensive sample preparation may be time-consuming and risk the significant loss of some trace analytes. The best way to further compensate matrix effects is the use of an 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 the 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 sewage treatment plant (STP) influent samples analyzing 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.

Comparative study of the LC–MS/MS and UPLC–MS/MS for the multi-residue analysis of quinolones, penicillins and cephalosporins in cow milk, and validation according to the regulation 2002/657/EC

“…Some researchers have focused on optimising sample preparation to reduce matrix effect, while others have assessed the level of matrix effect and compensated for the alteration in signal by using an internal standard (IS), often a stable isotope-labelled analogue of the drug [29][30][31][32] or, if it is lacking, a structural analogue. However, in a multi-component analysis, finding an appropriate IS for every analyte might be difficult or impossible.…”

Simultaneous determination of triazines and their main transformation products in surface and urban wastewater by ultra-high-pressure liquid chromatography–tandem mass spectrometry

“…This undesirable matrix effects can be considered as one of the main LC-MS/MS drawbacks, mainly when an electrospray ionization source (ESI) is used [32]. To ensure an accurate quantification of analytes, different approaches are applicable in order to compensate for the matrix effects [33][34][35][36][37][38][39]. A simple method is the dilution of sample [35].…”

“…However, this is limited by the limits of detection required for the target compounds. The use of matrix-matched standards for calibration [36], is not much useful in environmental samples, as their composition vary in a broad range, and obtaining a blank of similar composition to sample is not easy. The standard additions method can provide accurate results [37], but in practice, it needs both a time-consuming sample preparation and evaluation of the obtained results and therefore is not much suitable for fast routine analysis.…”

Natural and synthetic estrogens in wastewater treatment plant effluent and the coastal ocean

“…Rather, matrix-matched calibration curves were used (Kang, Hick et al 2007;, and instrumental response was normalized to the appropriate SIS (E1-3S-d4 for all conjugates; E1-d4 for all free and halogenated forms).…”

“…Since it was not practical to obtain or produce a wastewater matrix that was free of estrogens, we calculated matrix effects based on the ratio of the response factors (calibration curve slope) for estrogens spiked into wastewater matrix extracts and neat solvent (Kang, Hick et al 2007). The matrix effects observed in this study (see Table 1) are consistent with ion suppression reported in other studies of estrogens in wastewater matrices (Kang, Hick et al 2007;Backe and Field 2012).…”