A multiresidue analytical method using solid-phase extraction and high-pressure liquid chromatography tandem mass spectrometry to measure pharmaceuticals of different therapeutic classes in urban wastewaters
Introduction
Modern society makes available a wide range of pharmacologically active substances that are used in significant amounts to treat or prevent diseases. These substances are commonly excreted as the parent compound and/or metabolites in urine and faeces and discharged into domestic wastewaters continuously. The likelihood of a drug entering the environment depends mostly on the amount sold, and on its metabolic and physical–chemical properties. Several pharmaceuticals, widely used for human and veterinary medicine, are excreted unchanged or as active metabolites in high percentages. Antibacterial drugs such as fluoroquinolones (about 4 tonnes/year are sold in Switzerland and 14 tonnes/year in Italy) [1], [2] are excreted mostly unchanged [1]. Diuretics like furosemide and hydrochlorothiazide (6.40 and 14.66 tonnes/year usage in Italy in 2001) are excreted 90–95% unchanged, and the β-blocker atenolol (22.07 tonnes/year in Italy in 2001) is excreted 90% unchanged [2]. Several other pharmaceuticals from different therapeutic classes such as bezafibrate (lipid regulating), ranitidine (ulcer healing) and lincomycin (antibacterial) are excreted as the parent compound for about 50% [2], [3]. Therefore, hundreds of tonnes of pharmacologically active substances enter sewage treatment plants (STPs) each year, where they can escape degradation, and can eventually contribute to widespread environmental pollution.
Recent analytical studies [3], [4], [5], [6], [7] show that some pharmaceuticals are poorly removed in STPs and are consequently detectable in surface waters (rivers, lakes and seas) in the ng/L up to the μg/L range [2], [8], [9], [10]. STPs might therefore be important point sources of contamination, but for the majority of pharmaceuticals little information is available on their behaviour and ultimate fate in STPs and in the receiving surface water.
A multiresidue analytical method is a prerequisite to provide reliable figures on the fate of pharmaceuticals in STPs and surface water and to assess drug removal, partition and fate in the environment. Several analytical methods have been set up in Europe and USA for the detection of specific therapeutic categories [11], [12], [13], [14], [15], [16]. Other methods are aimed at a wide range of compounds possibly present [17], [18], [19], [20], [21], [22]. In Italy a multiresidue analytical method is already available [2] for the simultaneous determination of a limited number of pharmaceuticals.
This paper describes an improved analytical method to measure an extended list of 30 drugs, belonging to several therapeutic classes, at low concentrations in surface waters (about 1 ng/L). Pharmaceuticals were divided in two groups, extracted by different solid-phase extraction (SPE) methods, and analysed by reversed-phase liquid chromatography tandem mass spectrometry. The method was specifically designed to measure with accuracy a list of priority drugs, predicted to cause most of the pollution from pharmaceuticals in Italy. Pharmaceuticals for human use were selected according to their predicted environmental loads in Italy and the top pharmaceuticals by annual tonnage were included in the list. A group of historical drugs with long environmental persistence were also included, together with a group of molecules with high activity and potential toxicity, like estrogens and anti-cancer drugs. Some drugs widely used in animals [2] are also included, to assess the contribution of veterinary medicines. The analytical method was then applied to measure pharmaceuticals in effluents of STPs of several major Italian towns, in the framework of a national project funded by MIUR (Ministry of University and Research).
Section snippets
Chemicals and materials
Table 1 shows the list of drugs selected for analysis, with their therapeutic category. It includes several antibacterial drugs, belonging to the penicillins, quinolones, macrolides, lincosamides and sulfamides class, some diuretics, cardiovascular, gastrointestinal and central nervous system drugs, an anti-inflammatory, a bronchodilator, a lipid regulator drug, some estrogens and two anticancer drugs. Two metabolites, clofibric acid, a metabolite of clofibrate, and demethyl diazepam, a
Solid-phase extraction
Among the extraction materials tested were two polymeric sorbents (Lichrolut EN and Oasis HLB), a mixed polymeric and cation exchange sorbent (Oasis MCX) and an apolar sorbent (C18). Various pH conditions were tested. On the basis of these preliminary investigations, we extracted the pharmaceuticals using two different SPE methods, with an Oasis MCX at pH 1.5–2.0 or with a Lichrolut EN at pH 7.0. The Oasis MCX is a mixed reversed phase-cation exchange cartridge, in which the strong cation
Conclusions
Pharmaceuticals have a variety of different structures and physical–chemical properties, requiring complex methods for their simultaneous analysis. In this study, we divided pharmaceuticals into two groups, extracted from aqueous samples with two different SPE methods, and analysed by HPLC–MS–MS in positive and negative ionisation mode. This method was subsequently used to measure pharmaceuticals in effluent of STPs of some Italian towns. Nineteen pharmaceuticals were detected in concentrations
Acknowledgment
The support of the Ministry of University and Research is gratefully acknowledged.
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