Optimization of antibiotic analysis in water by solid-phase extraction and high performance liquid chromatography–mass spectrometry/mass spectrometry

This paper describes the development of an optimized method based on solid-phase extraction (SPE) followed by liquid chromatography–electrospray ionization tandem mass spectrometry (LC–MS/MS) for the simultaneous analysis of ten antibiotic compounds including tetracyclines, sulfonamides, macrolides and quinolones. LC–MS/MS sensitivity has been optimized by alterations to both LC and MS operations. Of the two high resolution columns tested, Waters Symmetry C₁₈ endcapped and Agilent Zorbax Bonus-RP, the latter was found to show better performance in producing sharp peaks and clear separation for most of the target compounds. Optimization of the MS fragmentation collision and cone energy enhanced the peak areas of the target analytes. The recovery of the target compounds from water samples was most efficient on Waters Oasis HLB SPE cartridge, while methanol was shown to be the most suitable solvent for desorbing the compounds from SPE. In addition, acidification of samples prior to SPE was shown to enhance the recovery of the compounds. To ensure a satisfactory recovery, the flow rate through SPE should be maintained at ≤10 mL min⁻¹. The method was successfully applied to the analysis of antibiotics from environmental water samples, with concentrations being <LOD in tap water, between <LOD to 28 ng L⁻¹ in river water and between <LOD to 230 ng L⁻¹ in sewage effluent.     

Automated on-line column-switching HPLC-MS/MS method for measuring environmental phenols and parabens in serum

We developed a method using on-line solid phase extraction (SPE) coupled to high performance liquid chromatography–isotope dilution tandem mass spectrometry (HPLC–MS/MS) to measure the serum concentrations of seven environmental phenols and five parabens: bisphenol A; ortho-phenylphenol; 2,4-dichlorophenol; 2,5-dichlorophenol; 2,4,5-trichlorophenol; benzophenone-3; triclosan; and methyl-, ethyl-, propyl-, butyl-, and benzyl-parabens. The phenols and parabens present in serum were retained and concentrated on a C18 reversed-phase size-exclusion SPE column, back-eluted from the SPE column while the eluate was diluted through a mixing Tee (analyte peak focusing), separated using a pair of monolithic HPLC columns, and detected by isotope dilution-MS/MS. Sample preparation did not require protein precipitation, only dilution of the serum with 0.1 M formic acid. This method, which combines an on-line SPE with analyte peak focusing feature and the selective atmospheric pressure photoionization MS detection, resulted in limits of detection ranging from 0.1 to 0.5 ng/mL for most of the analytes. The high throughput and adequate sensitivity with yet a relative low serum volume used (100 μL) confirm that analytically it is possible to measure simultaneously these phenols and parabens with the precision and accuracy at sub-parts-per-billion levels required for biomonitoring. However, important additional factors, including validated sample collecting, handling, and storing protocols, as well as toxicokinetic data, are required if these measures are used for exposure assessment.     

Efficiency of a miniaturized silica monolithic cartridge in reducing matrix ions as demonstrated in the simultaneous extraction of morphine and codeine from urine samples for quantification with liquid chromatography-tandem mass spectrometry (LC-MS/MS)

Presence of matrix ions could negatively affect the sensitivity and selectivity of liquid chromatography‐tandem mass spectrometer (LC‐MS/MS). In this study, the efficiency of a miniaturized silica monolithic cartridge in reducing matrix ions was demonstrated in the simultaneous extraction of morphine and codeine from urine samples for quantification with LC‐MS. The miniaturized silica monolith with hydroxyl groups present on the largely exposed surface area function as a weak cation exchanger for solid phase extraction (SPE). The miniaturized silica cartridge in 1 cm diameter and 0.5 cm length was housed in a 2‐ml syringe fixed over a SPE vacuum manifold for extraction. The cleaning effectiveness of the cartridge was confirmed by osmometer, atomic absorption spectrometer, LC‐MS and GC‐TOFMS. The drugs were efficiently extracted from urine samples with recoveries ranging from 86% to 114%. The extracted analytes, after concentration and reconstitution, were quantified using LC‐MS/MS. The limits of detection for morphine and codeine were 2 ng/ml and 1 ng/mL, respectively. The relative standard deviations of measurements ranged from 3% to 12%. The monolithic sorbent offered good linearity with correlation coefficients > 0.99, over a concentration range of 50–500 ng/ml. The silica monolithic cartridge was found to be more robust than the particle‐based packed sorbent and also the commercial cartridge with regards to its recyclability and repeated usage with minimal loss in efficiency. Our study demonstrated the efficiency of the miniaturized silica monolith for removal of matrix ions and extraction of drugs of abuse in urinary screening. Copyright © 2011 John Wiley & Sons, Ltd.     

High performance liquid chromatography–tandem mass spectrometry for the analysis of 10 pesticides in water: A comparison between membrane-assisted solvent extraction and solid phase extraction

This work describes the application of two sample preparation methods: membrane-assisted solvent extraction (MASE) and solid phase extraction (SPE) in combination with high performance liquid chromatography–tandem mass spectrometry (HPLC–MS–MS) for the determination of 10 pesticides in surface and ground water. Optimal extraction conditions for MASE were 60 min extraction time at 30 °C with a solvent volume of 100 μL toluene. 5 μL of the toluene extract were directly injected in the HPLC–MS–MS system. Concerning SPE, two materials were tested and C18 was superior to Oasis HLB. Complete desorption was ensured by desorbing the SPE (C18) cartridge with 3 mL of an acetonitrile/methanol mixture (1:1). After evaporation, the extract was injected in the analytical system. Analyte breakthrough was not found for the investigated compounds. For both methods, high extraction yields were achieved, in detail 71% (metalaxyl) till 105% (linuron) for MASE and 52% (ethiofencarb) till 77% (prometryne) for SPE (C18). Detection limits were in the low ng/L range for both methods and precision, expressed as the relative standard deviation (RSD) of the peak areas was below 13%. Five real water samples were analyzed applying both extraction methods. The results were in good agreement and standard addition proved that no matrix effects (such as ion suppression) occurred. In this comparison SPE has the potential of larger sensitivity whereas faster analysis and slightly better recoveries were achieved with MASE. MASE shows potential to be a promising alternative to the conventional off-line SPE concerning low to medium polar compounds.     

Investigation of acidic pharmaceuticals in river water and sediment by microwave-assisted extraction and gas chromatography–mass spectrometry

Investigations were performed along the Danube river at Budapest (Hungary) by collecting water and sediment samples simultaneously for 1 year in order to clarify the possible hazard of selected acidic pharmaceuticals (ibuprofen, naproxen, ketoprofen, and diclofenac) on the water supply used for the production of drinking water by bank filtration. In the case of water samples, the sample preparation procedure included solid phase extraction (SPE), meanwhile, in the case of sediment samples, microwave-assisted extraction (MAE) followed by dispersive matrix extraction (DME) for pre-cleaning as well as SPE for enrichment. The quantification was carried out using gas chromatography–mass spectrometry (GC–MS). The calculated recoveries were 97–99% (± 7%) for the water and 95–103% (± 12%) for the sediment samples. In the river water, ketoprofen concentration was always below the limit of quantification (LOQ) level; ibuprofen, naproxen and diclofenac could be quantified in the range of 8–50, 2–30, 7–90 ng/L. In sediments, only naproxen and diclofenac were found in the range of 2–20 and 5–38 ng/g, respectively. According to the obtained results, the concentration ratios of the two phases linearly depended on the total organic carbon content (TOC) of the sediments at each sampling date. The linear regressions were 0.925 and 0.946 for naproxen and diclofenac, respectively.     

Synthesis of a molecularly imprinted polymer and its application for microextraction by packed sorbent for the determination of fluoroquinolone related compounds in water

Molecularly imprinted polymer (MIP) has been synthesized by precipitation polymerization using ciprofloxacin (CIP) as template for the analysis of fluoroquinolone antibiotics (FQs). This MIP material was packed as sorbent in a device for microextraction by packed sorbent (MEPS) combined with liquid chromatography–tandem mass spectrometry (LC–MS/MS) for the analysis of selected FQs drugs including CIP, norfloxacin (NOR) and ofloxacin (OFLO) in municipal wastewater samples. In comparison to the new MIP-MEPS procedure, the target compounds were also determined by solid-phase extraction (MISPE) using the new molecular imprinted polymer material to validate the new MIP-MEPS method. The ability of the MIP for molecular recognition of CIP, NOR and OFLO was proved in presence of structurally different environmental relevant substances such as quinolones (Qs), flumequine (FLU), di(methyl)phthalate (DMP), technical 4-nonylphenol (NP), caffeine, Galaxolide^®, Tonalid^®, di(butyl)phthalate (DBP), Triclosan, bisphenol-A (BPA), carbamazepine, di(ethylhexyl)phthalate (DEHP), estradiol and octocrylene. The analysis of wastewater samples revealed the high selectivity of the synthesized polymer which was able to recognize and retain the target analytes by both extraction methods, the offline SPE with MIP material and the semi-automated MEPS packed with MIP material.     

A systematic investigation to optimize simultaneous extraction and liquid chromatography tandem mass spectrometry analysis of estrogens and their conjugated metabolites in milk

In this study, the simultaneous extraction of estrone (E1), 17β-estradiol (E2), estriol (E3), ethinylestradiol (EE2), and their glucuronated and sulfated metabolites in milk was optimized using solid-phase extraction (SPE). The aim of this research was to analyze estrogens and their conjugated metabolites by liquid chromatography with tandem mass spectrometry (LC–MS/MS) in a single run, without the need to perform enzymatic cleavage and derivatization. Two SPE cartridges in tandem were used, consisting of sorbents based on the hydrophilic–lipophilic balance and amine-functionalized packing materials. To monitor analyte loss at every step of the SPE procedure ¹⁴C-labeled E2 was spiked into the milk sample and the radioactivity was monitored at all stages of the SPE. In addition, non-radiolabeled standards of estrogens and metabolites were used to optimize solvent systems for the SPE and LC–MS/MS. The optimized method described in this paper can achieve recoveries ranging from 72% to 117% for the free estrogens (E1, E2, E3, and EE2), and 62% to 112% for seven conjugated metabolites. The three doubly conjugated, highly polar metabolites included in this study gave lower recoveries (≤43%) due to poor retention in SPE. Finally, commercial milk samples were analyzed for the presence of estrogens and their conjugated metabolites. Estrone (concentration range: 23–67 ng/L) was found to be the major free estrogen present in all milk samples. Estradiol was consistently observed in milk, but the concentrations were below the limit of detection (LOD of 10 ng/L), and no estriol and ethinylestradiol were detected. Several conjugated estrogen metabolites were identified, 17β-estradiol-3-glucuronide (71–289 ng/L), estrone-3-sulfate (60–240 ng/L), 17β-estradiol-3,17β-sulfate (<LOD to 30 ng/L), and estrone-3-glucuronide (<LOQ of 25 ng/L). This method proved efficient in the simultaneous analysis of estrogens and their metabolites in milk.     

Combined use of liquid chromatography triple quadrupole mass spectrometry and liquid chromatography quadrupole time-of-flight mass spectrometry in systematic screening of pesticides and other contaminants in water samples

As a suitable way for routine screening of pesticides and control of other organic contaminants in water, the combination of liquid chromatography triple quadrupole tandem mass spectrometry (LC–QqQ-MS/MS) and liquid chromatography–hybrid quadrupole time-of-flight mass spectrometry (LC–QTOF-MS) has been applied to the analysis of 63 surface and waste water samples after conventional solid-phase extraction (SPE). The extracts were screened for 43 pesticides or degradation products by LC–QqQ-MS/MS achieving limits of detection (LOD) ranged from 0.04 to 2 ng L⁻¹. Of the 43 selected pesticides, 33 were detected in water samples. The ESI–QTOF MS instrument was run using two simultaneous acquisition functions with low and high collision energy (MS^E approach) and acquiring the full mass spectra. A home-made database containing more than 1100 organic pollutants was used for substance identification. Around 250 of these compounds were available at the laboratory as reference standards. Five pesticides and 3 of their degradation products, different to those selected in the QqQ method, were detected by QqTOF-MS. Thirteen pharmaceuticals and two drugs of abuse were also identified in the samples. In practice, the sample preparation proved to be suitable for both techniques and for a wide variety of substances with different polarity. Mutual confirmation and evidence of co-occurrence of several other organic contaminants were the main advantages of the combination of both techniques.     

Development and application of a new on-line SPE system combined with LC-MS/MS detection for high throughput direct analysis of pharmaceutical compounds in plasma

A technique using a fully automated on-line solid phase extraction (SPE) system (Symbiosis, Spark Holland) combined with liquid chromatography (LC)-mass spectrometry (MS/MS) has been investigated for fast bioanalytical method development, method validation and sample analysis using both conventional C18 and monolithic columns. Online SPE LC-MS/MS methods were developed in the automated mode for the quantification of model compounds (propranolol and diclofenac) directly in rat plasma. Accuracy and precision using online SPE LC-MS/MS with conventional C18 and monolithic columns were in the range of 88-111% and 0.5-14%, respectively. Total analysis cycle time of 4 min per sample was demonstrated using the C18 column. Monolithic column allowed for 2 min total cycle time without compromising the quality and validation criteria of the method. Direct plasma sample injection without on-line SPE resulted in poor accuracy and precision in the range of 41-108% and 3-81%. Furthermore, the increase in back pressure resulted in column damage after the injection of only 60 samples.     

Microwave‐assisted extraction and high‐throughput monolithic‐polymer‐based micro‐solid‐phase extraction of organophosphorus,triazole, and organochlorine residues in apple

A high‐throughput micro‐solid‐phase extraction device based on a 96‐well plate was constructed and applied to the determination of pesticide residues in various apple samples. Butyl methacrylate and ethylene glycol dimethacrylate were copolymerized as a monolithic polymer and placed in the cylindrically shaped stainless‐steel meshes of 96‐micro‐solid‐phase extraction device and used as an extracting unit. Before the micro‐solid‐phase extraction, microwave‐assisted extraction was employed to facilitate the transfer of the pesticide residues from the apple matrix to liquid media. Then, 1 mL of the aquatic samples was transferred into the 96‐well plate and the 96‐micro‐solid‐phase extraction device was applied for the extraction of the selected pesticides. Influential parameters, such as sorbent‐to‐sorbent reproducibility, microwave‐assisted extraction time, ionic strength and micro‐solid‐phase extraction time, were optimized. The limits of quantitation were below 120 μg/kg, which are lower than the maximum residue limits. The developed method was successfully implemented for the extraction and determination of the selected pesticides from 20 different apple samples gathered from local markets. Phosalone was identified and quantified at the concentration level of 147 (±16.4) μg/kg in one of the samples.     

Monolithic packed 96‐tips set for high‐throughput sample preparation: determination of cyclophosphamide and busulfan in whole blood samples by monolithic packed 96‐tips and LC‐MS

A monolithic methacrylate packed 96‐tips device was used for the extraction of the busulfan and cyclophosphamide in whole blood samples. Using a packed 96‐tips set, a 96‐well plate could be handled in about 2 min. The key aspect of the monolithic phase is that monolithic material can offer both good extraction capacity and low‐back‐pressure properties. The validation of the methodology showed that the accuracy values of quality‐control samples were between 99 and 113% for busulfan, and between 103 and 110% for cyclophosphamide. The inter‐day precision ranged from 7.0 to 12% for busulfan and from 13 to 16% for cyclophosphamide. The standard calibration curves were obtained within the concentration range 5–2000 nm for busulfan and from 10 to 5000 nm for cyclophosphamide in blood samples. The coefficients of determination were ≥0.99. Copyright © 2012 John Wiley & Sons, Ltd.     

The development of a gas chromatographic–mass spectrometric analytical procedure for the determination of lipids,proteins and resins in the same paint micro-sample avoiding interferences from inorganic media

This paper presents a GC–MS analytical procedure for determining proteinaceous materials, glycerolipids, natural waxes and terpenoid resins in the same paint micro-sample. The procedure is also reliable when high amounts of interfering inorganic pigments, dryers and charges are present. The characterisation of proteinaceous binders in a paint sample can be subject to analytical interferences by inorganic materials. Such materials may form complexes with functional groups of proteins, thus preventing their efficient derivatisation, which is necessary prior to GC analysis. For this reason an analytical procedure has been developed based on two extractions and a clean-up step, in order to obtain two fractions: a lipid-resinous fraction and a proteinaceous fraction. The lipid-resinous fraction is subjected to salification/saponification assisted by microwaves, followed by acidification, extraction, derivatisation and GC–MS analysis. The proteinaceous fraction is analysed by GC–MS after hydrolysis and derivatisation of the freed amino acids. The desalting step is applied before the hydrolysis, and is based on the use of the monolithic sorbent tip technology with a C4 stationary phase. Reference paint replicas of egg, casein and animal glue were prepared with and without several metals containing pigments, and used to develop and validate the analytical procedure. The procedure proved to be efficient in desalting the proteinaceous materials both from cations and anions. Although non quantitative, it is reliable in the analysis of samples whose content of extractable proteins is <1 μg, thus showing it to be suitable for the characterisation of paint samples. An example of how the analytical procedure was used to characterise a sample from a 15th century panel painting is also discussed.     

Study on the matrix effect in the determination of selected pharmaceutical residues in seawater by solid-phase extraction and ultra-high-performance liquid chromatography–electrospray ionization low-energy collision-induced dissociation tandem mass spectrometry

Matrix effect is a major problem when trace level pharmaceuticals in seawater were analyzed using solid-phase extraction (SPE) combined with high-performance liquid chromatography–electrospray ionization tandem mass spectrometry (HPLC–ESI–MS–MS). Therefore, efforts should be devoted to diminish matrix effect as much as possible. The present study investigates the matrix effect during the analysis of selected pharmaceutical residues (naproxen, ibuprofen, diclofenac and gemfibrozil) in seawater samples with ultra-high-performance liquid chromatography (UHPLC)–ESI low-energy collision-induced dissociation (CID) MS–MS. Solutions to reduce matrix effect were studied through optimization of SPE procedure and the employment of isotope-labeled analogues. Results showed that 30 mL of deionized water can efficiently diminish matrix effect and satisfactory absolute mean recoveries ranging from 73.5% to 120.5% were obtained in the optimized SPE condition. Isotope-labeled analogues employed as surrogates were found to be efficient to further compensate for matrix effect, with the relative mean recoveries ranging from 85.5% to 110.5%. The optimized method has been successfully applied for the analysis of target pharmaceutical residues in different seawater samples.     

疏水整体柱在线固相萃取与高效液相色谱-串联质谱联用测定牛肝中5种阿维菌素类药物残留

建立了牛肝中5种阿维菌素类药物残留的疏水整体柱在线固相萃取结合高效液相色谱-串联质谱测定的方法。以疏水的聚(甲基丙烯酸丁酯-乙二醇二甲基丙烯酸酯)整体柱(10 mm×2.1 mm)作为固相萃取介质,考察了上样流动相和洗脱流速对阿维菌素类药物的萃取效果,优化了梯度洗脱流动相的种类及质谱条件。方法在1~100 μg/L范围内线性关系良好(r>0.995),定量限为5 μg/kg。在5、10、50、100 μg/kg添加水平的回收率为77.4%~98.4%,日内和日间相对标准偏差分别为4.46%~8.03%和4.79%~8.68%,并且该柱反复使用400次后未发现萃取效率降低。结果表明,该整体柱对牛肝中5种阿维菌素类药物能够有效萃取,并且可以重复使用。该方法简单,自动化程度高,可应用于常规阿维菌素类药物残留分析。     

A simple hollow fiber renewal liquid membrane extraction method for analysis of sulfonamides in honey samples with determination by liquid chromatography–tandem mass spectrometry

A sensitive and precise analysis using hollow fiber renewal liquid membrane (HFRLM) extraction followed by high performance liquid chromatography–tandem mass spectrometry (LC–MS/MS) is described for determination of five sulfonamides in honey samples. In this procedure, the organic solvent introduced directly into the sample matrix extracts the sulfonamides and carries them over the polypropylene porous membrane. An organic solvent is immobilized inside the polypropylene porous membrane, leading to a homogeneous phase. The stripping phase at higher pH in the lumen of the membrane promotes the ionization of the target compounds releasing them to this phase. The most important parameters affecting the extraction efficiency were optimized by multivariable designs (pH and sample mass, pH and buffer for stripping phase, extraction temperature and time, type and volume of extractor solvent and use of salt to saturate the sample). Detection limits in the range of 5.1–27.4 μg kg⁻¹ and linearity coefficient of correlation higher than 0.987 were obtained for the target analytes. The results obtained for the proposed method show that HFRLM–LC–MS/MS can be used for determination of the five sulfonamides studied in honey samples with excellent precision, accuracy, practicality and short analysis time.     

Determination of organic priority pollutants and emerging compounds in wastewater and snow samples using multiresidue protocols on the basis of microextraction by packed sorbents coupled to large volume injection gas chromatography–mass spectrometry analysis

This paper describes the development and validation of a new procedure for the simultaneous determination of 41 multi-class priority and emerging organic pollutants in water samples using microextraction by packed sorbent (MEPS) followed by large volume injection–gas chromatography–mass spectrometry (LVI–GC–MS). Apart from method parameter optimization the influence of humic acids as matrix components on the extraction efficiency of MEPS procedure was also evaluated. The list of target compounds includes polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), phthalate esters (PEs), nonylphenols (NPs), bisphenol A (BPA) and selected steroid hormones. The performance of the new at-line microextraction-LVI–GC–MS protocol was compared to standard solid-phase extraction (SPE) and LVI–GC–MS analysis. LODs for 100 mL samples (SPE) ranged from 0.2 to 736 ng L⁻¹ were obtained. LODs for 800 μL of sample (MEPS) were between 0.2 and 266 ng L⁻¹. In the case of MEPS methodology even a sample volume of only 800 μL allowed to detect the target compounds. These results demonstrate the high sensitivity of both procedures which permitted to obtain good recoveries (>75%) for all cases. The precision of the methods, calculated as relative standard deviation (RSD) was below 21% for all compounds and both methodologies. Finally, the developed methods were applied to the determination of target analytes in various samples, including snow and wastewater.     

Inter-laboratory trials for analysis of perfluorooctanesulfonate and perfluorooctanoate in water samples: Performance and recommendations

The ISO 25101 (International Organization for Standardization, Geneva) describes a new international standard method for the determination of perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) in unfiltered samples of drinking and surface waters. The method is based on the extraction of target analytes by solid phase extraction, solvent elution, and determination by high performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS). For the determination of the performance of this method, more than 20 laboratories from 9 different countries participated in an inter-laboratory trial in 2006. In addition, inter-laboratory trials were conducted in 2008 and 2009 for the analysis of perfluoroalkylsubstances (PFASs), including PFOS and PFOA, in water samples by following the protocols of Japanese Industrial Standard (JIS). Overall, the repeatability coefficients of variation (i.e., within-laboratory precision) for PFOS and PFOA in all water samples were between 3 and 11%, showing a adequate precision of the ISO and JIS methods. The reproducibility coefficients of variation (i.e., between-laboratory precision) were found to vary within a range of 7–31% for surface water and 20–40% for wastewater. The recoveries of PFOS and PFOA, as a measure of accuracy, varied from 84 to 100% for surface water and from 84 to 100% for wastewater among the samples with acceptable criteria for internal standards recovery. The determined concentrations of PFASs in samples compared well with the “true” values. The results of the inter-laboratory trial confirmed that the analytical methods are robust and reliable and can be used as a standard method for the analysis of target compounds in water samples.     

采用自动前处理LC/MS进行血浆中药物的快速分析

药物研究的发展对高通量的样品处理分析提出了越来越高的要求,减少样品制备时间和分析时间是解决问题的关键。我们新近发展了一种具有在线稀释旁路和新的样品预处理柱的Shim-Pack MAYI-ODS自动柱切换HPLC和LC／MS系统,该系统无需样品前处理,可直接进样进行血浆、血清中的药物分析。本文利用自动样品前处理LC／MS系统,用ODS整体柱实现了血浆中药物的快速分析。包括样品预处理,整个分析仅需1．2min完成。     

Determination of fecal sterols by gas chromatography–mass spectrometry with solid-phase extraction and injection-port derivatization

Injection-port derivatization combined with solid-phase extraction (SPE) was developed and applied for the first time to determine five types of fecal sterols (coprostanol, cholestanol, epicholestanol, epicoprostanol and cholesterol) with gas chromatography–mass spectrometry (GC–MS). In this method, silylation of fecal sterols was performed with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) at GC injection-port. The factors influential to this technique such as injection-port temperature, purge-off time, derivatization reagent (BSTFA) volume, and the type of organic solvent were investigated. In addition, the conditions of SPE (including the type of SPE cartridge, the type of elution organic solvent) were also studied. After SPE followed by injection-port silylation by GC–MS, good linearity of analytes was achieved in the range of 0.02–10 ng/mL with coefficients of determination, R² > 0.995. Good reproducibility was obtained with relative standard deviation less than 19.6%. The limits of detection ranged from 1.3 ng/mL to 15 ng/mL (S/N = 3) in environmental water samples. Compared with traditional off-line silylation of fecal sterols performed with water bath (60 °C, 30 min), this injection-port silylation method is much simpler and convenient. The developed method has been successfully applied for the analysis of fecal sterols from real environmental water samples.     

Total concentration analysis of polycylic aromatic hydrocarbons in aqueous samples with high suspended particulate matter content

The European water framework directive (WFD) requires priority pollutants to be measured in the whole water sample and not only in the dissolved phase. However, it does not give clear definitions on how to achieve this. To overcome this limitation, a new methodology of sample preparation procedure for the analysis of polycyclic aromatic hydrocarbons on the basis of extraction disks is introduced here. The automatable procedure includes a “one-step” extraction of the analytes both dissolved in the liquid phase of the sample and sorbed to suspended particulate matter. The latter is extracted concurrently with the solid-phase extraction (SPE) material within the elution step of the procedure. Separation, identification, and quantification of the analytes is performed by GC–MS. Results from surface water samples spiked with certified sediment up to 1000 mg/l are presented in this work and compared with results derived from liquid–liquid extraction (LLE). Most measured values are within or at least near certified uncertainty limits of the sediment. The SPE disk method shows much higher recoveries and better precision (relative standard deviations between 2% and 11%) than the standard LLE method. For all substances under investigation, the limits of quantification achieved range between 0.001 and 0.005 μg/l.