Assessment of direct analysis in real time accurate mass spectrometry for the determination of triclosan in complex matrices

M Cobo-Golpe,M Ramil,R Cela,I Rodríguez,J García-Martín

doi:10.1007/s00216-021-03591-2

Abstract

In this work, the applicability of direct analysis in real time coupled to accurate mass spectrometry (DART-MS) to the quantitative determination of triclosan (TCS) in samples with increasing complexity, from personal care products to extracts from sewage, is investigated. In the first term, DART-MS spectra of TCS as free phenol and as derivatized species are characterized; thereafter, the effects of several instrumental variables in the detectability of TCS (i.e., temperature, solvent, and compound holder) are discussed. Under final selected conditions, TCS was determined from its [M-H]− ions, without need of derivatization, attaining an instrumental limit of quantification of 5 ng mL−1, with a linear response range up to 1000 ng mL−1. Complex matrices, such as solid-phase extracts obtained from environmental water samples, moderately inhibited the ionization efficiency of TCS, with signal attenuation percentages in the range of 6 to 57%, depending on the sample type and on the concentration factor provided by the SPE procedure. The accuracy of results obtained by DART-MS was evaluated using liquid chromatography (LC) with MS detection; in both cases, a time-of-flight (TOF) MS instrument was employed for the selective determination of the [M−H]− ions of TCS (m/z values 286.9439 and 288.9410) using a mass window of 20 ppm. DART-MS did not only provide enough sensitivity to detect the presence of TCS in environmental samples (raw and treated wastewater as well as freeze-dried sludge), but also measured concentrations matched those determined by LC-ESI-TOF-MS, with only slightly higher standard deviations. During analysis of personal care products, containing much higher concentrations of TCS in a less complex matrix, both techniques were equivalent in terms of accuracy and precision.Graphical abstract

Highlights

Ambient ionization techniques, such as direct analysis in real time (DART) [1, 2], have been introduced recently coupled to mass spectrometry for rapid analysis of different kinds of samples
It is worth noticing that the completeness of derivatization reactions was assessed with the EI-MS spectra of TCS as silylated or acetylated species; see Supplementary information, Fig. S1 and S2
To the silylated forms, acetyl derivatives remain stable in the DART source leading to adducts with NH4+ ions, as it has been previously reported for bisphenol species [33]

Summary

Introduction

Ambient ionization techniques, such as direct analysis in real time (DART) [1, 2], have been introduced recently coupled to mass spectrometry for rapid analysis of different kinds of samples These techniques provide quantitative and qualitative information of different sample components, avoiding the chromatographic separation step and, sometimes, sample preparation. Triclosan (TCS) is a synthetic antimicrobial agent which inhibits the activity of bacteria, viruses, and fungi [7]. It is widely used in various personal care products such as soaps, cosmetics, mouthwashes, and toothpaste [7, 8] and in household items like toys, textiles, furniture, and kitchenware [9]. TCS has been found to be bioaccumulative in plants and earthworms [18,19,20], and correlated with the development of bacterial resistance [21, 22]

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