A sensitive method for extraction and determination of endocrine-disrupting compounds from wastewater using 10-ethyl-acridone-2-sulfonyl chloride as pre-column labeling reagent by high-performance liquid chromatography with fluorescence detection

Abstract

A sensitive pre-column derivatization method using 10-ethyl-acridone-2-sulfonyl chloride (EASC) as pre-column labeling reagent followed by high-performance liquid chromatography (HPLC) with fluorescence detection has been developed for the determination of eight endocrine-disrupting compounds: 4-octylphenol, 4-nonylphenol, bisphenol A, diethylstilbestrol, estrone, 17α-ethynylestradiol, 17β-estradiol and estriol in wastewater samples. Solid phase extraction (SPE) with ODS C18 cartridges was used for the extraction and purification. Derivatizing parameters including pH value, temperature and concentration of EASC, as well as types of SPE cartridges and eluents were investigated in detail. Under optimal conditions, the quantification limits for the desired compounds ranging from 1.0 to 2.0 ng L^− 1 were obtained. The recoveries were higher than 80.4% with a noticeable improvement for 4-octylphenol and 4-nonylphenol, whose recoveries were usually lower than 50% during the SPE process. The proposed method was successfully applied to the determination of the target compounds in wastewater samples with a much higher sensitivity than traditional HPLC method.

Introduction

Nowadays, more and more chemicals have been confirmed to possess endocrine-disrupting properties. They have been known to interfere with endocrine systems by mimicking, blocking and triggering actions of hormones and thereby influence the health and reproductive system of humans and wildlife [1], [2], [3]. Compounds identified as endocrine-disrupting compounds (EDCs) are members of different groups of chemicals, including drugs, pesticides, industrial by-products, alkylphenols, synthetic steroids, and so on. Belonging to the endocrine-disrupting phenolic family, estrogenic compounds, including xenoestrogens and endogenous estrogens, have gained increasing environmental and social concerns in recent years [4], [5], [6], [7], [8], [9], [10]. Among these estrogenic compounds, some are derived from excreta of humans and livestock (e.g. 17β-estradiol, estriol and estrone); some are synthetic estrogens added in feedstuffs for animals to promote their growth (e.g. diethylstilbestrol) or for contraceptive purpose (e.g. 17α-ethynylestradiol), and some are widely used industrial material (e.g. 4-nonylphenol, 4-octylphenol and bisphenol A). Because of the incomplete removal of these EDCs from wastewater treatment plants, they have a very high incidence to be found in environmental samples [11], [12], [13], [14], especially for 4-nonylphenol, 4-octylphenol and bisphenol A, which were reported to be found all over the world [15], [16], [17], [18], [19].

The potential effects of EDCs on human health have been highlighted in recent years [20], [21], [22]. EDCs can lead to serious side effects on human health at very low concentrations and these side effects are often potent and long-lasting. They are now suspected of disrupting reproduction for humans and wildlife, increasing the incidences of cancers, and some were reported to have transgenerational effects [23], [24]. These compounds usually exist simultaneously in our living environment with a self-aggravating tendency from year to year. Therefore, it is necessary to develop a rapid, simple and sensitive method for the simultaneous determination of these compounds in the environment.

With the development of analytical technologies, various approaches have been developed for the determination of EDCs, such as liquid chromatography (LC) [25], [26], [27], liquid chromatography–mass spectrometry (LC–MS) [28], [29] and gas chromatography–mass spectrometry (GC–MS) [30], [31], [32]. Because of the absence of a chromophore or fluorophore group in their chemical structure (see Fig. 1), these compounds commonly exhibit low ultraviolet absorption and poor fluorescence property. Therefore, the sensitivity for the direct determination of these compounds by LC methods is usually limited, while the sensitivity of LC–MS methods is also restricted as estrogenic compounds exhibit low ionization efficiency in MS ion chamber. Furthermore, the methods of GC–MS and LC–MS are expensive and not accessible in ordinary laboratories.

In this work, a pre-column derivatization method for the simultaneous determination of eight EDCs using EASC as labeling reagent was developed. In order to obtain lower detection limits and assure better recoveries for all the target compounds, the pretreatment conditions for the extraction and purification of eight EDCs from wastewater samples using various types of the SPE cartridges were optimized. At the same time, the derivatization conditions were modified to enhance sensitivity. Based on the development of the previously proposed method in our laboratory [33], a simple and sensitive LC method was built for the simultaneous determination of eight EDCs in water samples. The established method was successfully applied to the analysis of EDCs in wastewater samples.