A novel dendritic surfactant for enhanced microcystin-LR detection by double amplification in a quartz crystal microbalance biosensor

Enhanced sensitivity for the hepatotoxin microcystin-LR (MC-LR) was achieved in a quartz crystal microbalance (QCM) system via double amplification. For primary amplification, an innovative interface on the QCM was obtained as a matrix by the vesicle layer formed by our synthetic dendritic surfactant, bis (amidoethyl-carbamoylethyl) octadecylamine (C18N3). The vesicle matrix was then functionalised by an optimised concentration of monoclonal antibodies against MC-LR (anti-MC-LR) to detect the analyte. The results showed that a detection limit of 100 ng/mL was achieved by primary amplification. To achieve higher sensitivity, secondary amplification was implemented with anti-MC-LR gold nanoparticle (AuNPs) conjugates as probes, which lowered the detection limit for MC-LR to 1 ng/mL (the maximum concentration recommended by the World Health Organization [WHO] in drinking water for humans). The QCM immunosensor reported here has advantages such as high sensitivity, portability, simplicity, and cost-effectiveness for MC-LR detection. It would be uniquely superior compared with current MC-LR detection techniques for on-the-spot water detection. Furthermore, the methodology described here is also potentially significant in many fields for the routine monitoring of environmental and food safety.     

超高效液相色谱–串联质谱法测定饮用水中微囊藻毒素

建立饮用水中微囊藻毒素(MC–RR,MC–LR)的超高效液相色谱–串联质谱检测方法。样品经PVDF针式过滤头过滤后直接进样,采用喷雾正离子源(ESI~+)和多重反应监测模式(MRM)测定。MC–RR的质量浓度在0.02~10.00μg/L范围内与色谱峰面积呈良好的线性,线性相关系数r~2=0.998 9,检出限为0.096μg/L,测定结果的相对标准偏差为6.6%~9.1%(n=7),加标回收率为99.0%~103.0%。MC–LR的质量浓度在0.1~20μg/L范围内与色谱峰面积呈良好的线性,线性相关系数r~2=0.999 2,检出限为0.188μg/L,测定结果的相对标准偏差为4.3%~10.0%(n=7),加标回收率为93.0%~114.0%。该方法灵敏度高、重现性好,可用于饮用水中微囊藻毒素的检测。     

Determination of diallyldimethylammonium chloride in drinking water by reversed-phase ion-pair chromatography-electrospray ionization mass spectrometry

A method for the direct determination of diallyldimethylammonium chloride (DADMAC) in water samples, using ion-pair liquid chromatography-mass spectrometry system was developed. The chromatographic separation was performed using a C18 column. The type, the concentration of ion-pair reagent and the pH were optimized to give good chromatographic retention and sensitivity for DADMAC. Quantification was achieved in the positive electrospray ionization mode using selected ion monitoring. The cone voltage was also studied to establish the optimal experimental conditions. Finally, the reproducibility of the proposed method was shown by good run-to-run and day-to-day precision values. No sample preparation was required and the detection limit was 0.1 microg/L. The method was used to detect residual DADMAC at drinking water treatment plants in Tianjin, north China. The concentration of DADMAC observed in drinking water ranged from below quantitation limit to 22.0 microg/L.     

Analysis of 70 Environmental Protection Agency priority pharmaceuticals in water by EPA Method 1694

The U.S. Environmental Protection Agency (EPA) Method 1694 for the determination of pharmaceuticals in water recently brought a new challenge for treatment utilities, where pharmaceuticals have been reported in the drinking water of 41-million Americans. This proposed methodology, designed to address this important issue, consists of solid-phase extraction (SPE) followed by liquid chromatography–mass spectrometry (LC/MS–MS) using triple quadrupole. Under the guidelines of Method 1694, a multi-residue method was developed, validated, and applied to wastewater, surface water and drinking water samples for the analysis of 70 pharmaceuticals. Four distinct chromatographic gradients and LC conditions were used according to the polarity and extraction of the different pharmaceuticals. Positive and negative ion electrospray were used with two MRM transitions (a quantifier and a qualifier ion for each compound), which adds extra confirmation not included in the original Method 1694. Finally, we verify, for the first time, EPA Method 1694 on water samples collected in several locations in Colorado, where positive identifications for several pharmaceuticals were found. This study is a valuable indicator of the potential of LC/MS–MS for routine quantitative multi-residue analysis of pharmaceuticals in drinking water and wastewater samples and will make monitoring studies much easier to develop for water utilities across the US, who are currently seeking guidance on analytical methods for pharmaceuticals in their water supplies.     

在线固相萃取-超高效液相色谱-三重四极杆质谱法测定水源水和饮用水中107种典型农药及代谢产物

为进行我国水体中农药风险监测,针对水体中农药种类多、浓度低的特点,建立了在线固相萃取-超高效液相色谱-串联质谱法快速筛查和检测水源水及饮用水中107种典型农药及代谢产物(有机磷类、有机氮类、有机杂环类、氨基甲酸酯类、酰胺类、苯甲酰脲类、新烟碱类等)的方法。样品经0.22 μm孔径亲水性聚四氟乙烯滤膜过滤后,通过自动进样器取5 mL样品注入在线固相萃取系统,经X Bridge C₁₈在线固相萃取柱吸附后用纯水淋洗,以乙腈和0.1%甲酸水溶液为流动相对在线固相萃取柱梯度洗脱后再经ACQUITY HSS T₃色谱柱分离,采用电喷雾离子源正离子及负离子模式分析检测,外标法定量。以水源水及饮用水作为基质,对其准确度和精密度进行方法学验证,结果表明:107种农药及代谢产物在不同范围内线性关系良好(r²>0.995),方法检出限(LOD, S/N=3)为0.03~1.5 ng/L,定量限(LOQ, S/N=10)为0.1~5.0 ng/L。将目标分析物在1、20、50 ng/L水平下加标,水源水和饮用水中的加标回收率分别为60.6%~119.8%和61.2%~119.0%,相对标准偏差(RSD, n=6)分别为0.3%~18.6%和0.4%~17.1%。用该方法测定水源水和饮用水中的农药残留,结果显示,酰胺类、三嗪类除草剂、三唑类杀菌剂与烟碱类、氨基甲酸酯类杀虫剂有较高的检出率,其中水源水中检出含量为0.1~97.1 ng/L,饮用水中检出含量为0.1~93.6 ng/L。该方法适用于水源水和饮用水中107种典型农药及代谢产物的痕量分析测定,有效提高了水体中农药类物质的检测效率,实际应用价值较高。     

Determination of microcystin-LR in drinking water using UPLC tandem mass spectrometry-matrix effects and measurement

A simple detection method using ultra-performance liquid chromatography electrospray ionisation tandem mass spectrometry (UPLC-ESI-MS-MS) coupled with the sample dilution method for determining trace microcystin-LR (MC-LR) in drinking water is presented. The limit of detection (LOD) was 0.04 μg/L and the limit of quantitation (LOQ) was 0.1 μg/L. Water matrix effects of ionic strength, dissolved organic carbon (DOC) and pH were examined. The results indicate that signal detection intensity for MC-LR was significantly suppressed as the ionic strength increased from ultrapure water condition, whereas it increased slightly with solution pH and DOC at low concentrations. However, addition of methanol (MeOH) into the sample was able to counter the signal suppression effects. In this study, dilution of the tap water sample by adding 4% MeOH (v/v) was observed to be adequate to compensate for the signal suppression. The recoveries of the samples fortified with MC-LR (0.2, 1, and 10 μg/L) for three different tap water samples ranged from 84.4% to 112.9%.     

Determination of pesticide residues and related compounds in water and industrial effluent by solid-phase extraction and gas chromatography coupled to triple quadrupole mass spectrometry

Pollution of drinking water supplies from industrial waste is a result of several industrial processes and disposal practices, and the establishment of analytical methods for monitoring organic compounds related to environmental and health problems is very important. In this work, a method using solid-phase extraction (SPE) and gas chromatography coupled to triple quadrupole tandem mass spectrometry (GC-QqQ-MS/MS) was developed and validated for the simultaneous determination of pesticide residues and related compounds in drinking and surface water as well as in industrial effluent. Optimization of the method was achieved by using a central composite design approach on parameters such as the sample pH and SPE eluent composition. A single SPE consisting of the loading on a polymeric sorbent of 100 mL of sample adjusted to pH 3 and elution with methanol/methylene chloride (10:90, v/v) permitted the obtaining of acceptable recoveries in most cases. The concentration factor associated with sensitivity of the chromatographic analysis permitted the achievement of the method limit of detection values between 0.01 and 0.25 μg L^?1. Recovery assays presented mean recoveries between 70 and 120 % for most of the compounds with very good precision, despite the different chemical nature of the compounds analyzed. The selectivity of the method, evaluated through the relative intensity of quantification and qualification ions obtained by GC-QqQ-MS/MS, was considered adequate. The developed method was finally applied to the determination of target analytes in real samples. River water and treated industrial effluent samples presented residues of some compounds, but no detectable residues were found in the drinking water samples evaluated.     

固相萃取-GC/MS法测定水样中20种有机氯农药

建立了用固相萃取小柱提取和净化、GC/MS定性定量同时测定水样中20种有机氯农药的方法。方法采用OasisHLB固相萃取小柱萃取富集水样,二氯甲烷洗脱,加入菲-d₁₀作为内标,利用GC/MS进行定性定量,步骤简便,线性响应良好,干扰小,方法检出限为0.21～0.72 ng/L（按水样1L计）,加标回收率为64.8%～122%,RSD为1.2%～11.0 %。成功利用该方法对广西实际河水样品进行了检测。结果表明方法可以同时满足环境水样中20种痕量有机氯农药的测定。     

Bioanalytical LC‐MS/MS method validation for plasma determination of topiramate in healthy Indian volunteers

A LC‐MS/MS method for plasma topiramate analysis is delineated involving least number of healthy volunteers. Topiramate and amlodipine internal standard (IS) were extracted by simple centrifuge‐coupled solid‐phase extraction and reverse‐phase chromatographic separation was performed on an Ascentis C₁₈ column. Turbo‐spray negative‐ion mode multiple‐reaction monitoring was selected for mass pair detection at m/z 338.3 → 78.0 and m/z 407.3 → 295.5 for analyte and IS respectively. The method showed a dynamic linearity range from 10.4 to 2045.0 ng/mL, lower limit of quantitation achieved at 10.4 ng/mL and finally a mass spectrometric total run time of within 2.5 min for human sample analysis. Bioequivalence was assessed successfully using this fully validated method on 16 fasted Indian male subjects with 25 mg topiramate tablet administration. An appropriate study design describes plasma samples collection up to 216 h post dose in two periods, separated by a 28 day washout period. The challenge of half‐life matching for test and reference drug was achieved with 73.43 ± 9.68 and 73.06 ± 14.03 h, respectively, and intra‐subject coefficient of variation achieved within 11% for AUCs and C_max evaluated by non‐compartmental pharmacokinetic analysis. The results of LCMS topiramate complete method validation supported by pharmacokinetic study have not been published before, and are presented and discussed for the first time in this article. Copyright © 2009 John Wiley & Sons, Ltd.     

Development and validation of high-performance liquid chromatography/electrospray ionization mass spectrometry for assay of madecassoside in rat plasma and its application to pharmacokinetic study

A rapid, sensitive and specific high-performance liquid chromatography/electrospray ionization mass spectrometric (LC-ESI-MS) method was developed and validated for the quantification of madecassoside, a major active constituent of Centella asiatica (L.) Urb. herbs, in rat plasma. With paeoniflorin as an internal standard (IS), a simple liquid-liquid extraction process was employed for the plasma sample preparation. Chromatographic separation was achieved within 6 min on a Shim-pack CLC-ODS column using acetonitrile and water (60:40, v/v) containing 0.1% (v/v) formic acid as the mobile phase. The detection was performed by MS with electrospray ionization interface in negative selected ion monitoring (SIM) mode. The linear range was 11-5500 ng/mL with the square regression coefficient (r(2) ) of 0.9995. The lower limit of quantification was 11 ng/mL. The intra- and inter- day precision ranged from 4.99 to 9.03%, and the accuracy was between 95.82 and 111.80%. The average recoveries of madecassoside and IS from spiked plasma samples were >92%. The developed method was successfully applied to the pharmacokinetic study of madecassoside in rats after an oral administration.     

Analysis of microcystins using high‐performance liquid chromatography and magnetic solid‐phase extraction with silica‐coated magnetite with cetylpyridinium chloride

Microcystins (MCs), produced by freshwater cyanobacteria, can be serious water pollutants, so it is important to monitor their concentration in drinking water. We have developed a method for rapid and accurate determination of microcystin levels in environmental water, using magnetic solid‐phase extraction and high‐performance liquid chromatography with UV detection. The magnetic composite material, which was combined with cetylpyridinium chloride, was prepared by hydrothermal synthesis. The optimal extraction of microcystins in water sample was achieved by optimizing the amount of adsorbent, time of adsorption, ratio of eluting solvent, and volume of eluent. Under the optimal conditions, the limit of detection of MC‐LR was 0.001 μg/L, and the limit of quantification was 0.0028 μg/L. The limit of detection of MC‐RR was 0.001 μg/L, and the limit of quantification was 0.003 μg/L. These values are far lower than those established by the International Health Organization for the maximum concentration of microcystins in drinking water. The magnetic solid‐phase extraction adsorbent used in this method has the advantages of simple preparation, low price, and easy solid–liquid separation, and it can be used for the rapid and sensitive monitoring of trace microcystins in environmental water samples.     

Rapid Screening of Haloacetonitriles in Water Samples by Optimized Vortex‐assisted Liquid–Liquid Microextraction

This paper describes an optimized method for the quick screening of low levels of haloacetonitriles (HANs), a nitrogenous disinfection byproduct. The method is especially geared toward screening of water used for drinking and in swimming pools. The method is based on vortex‐assisted liquid–liquid microextraction (VALLME), which is carried out before determination of the gathered samples by gas chromatography‐mass spectrometry (GC‐MS). Factors that can potentially affect the extraction efficiency of the desired trace chemicals from the gathered sample were enhanced using the Box–Behnken design method. The optimal VALLME parameters for a 10‐mL water sample (pH 4, containing 3 g of sodium sulfate), according to the Box–Behnken design method, are extractant 160 μL dichloromethane and vortex extraction time of 1 min at the maximum speed (2500 rpm). The limits of quantitation calculated were 16–35 ng/L. Precision for both intra‐ and inter‐day analysis was also calculated, which was less than 11% on three concentration levels. Mean extraction recovery, otherwise known as trueness, was between 71 and 92%. The developed method was applied successfully to extract HANs from drinking and swimming pool water samples.     

Simultaneous determination of three organophosphorus pesticides in different food commodities by gas chromatography with mass spectrometry

A sensitive and selective gas chromatography with mass spectrometry method was developed for the simultaneous determination of three organophosphorus pesticides, namely, chlorpyrifos, malathion, and diazinon in three different food commodities (milk, apples, and drinking water) employing solid‐phase extraction for sample pretreatment. Pesticide extraction from different sample matrices was carried out on Chromabond C₁₈ cartridges using 3.0 mL of methanol and 3.0 mL of a mixture of dichloromethane/acetonitrile (1:1 v/v) as the eluting solvent. Analysis was carried out by gas chromatography coupled with mass spectrometry using selected‐ion monitoring mode. Good linear relationships were obtained in the range of 0.1–50 μg/L for chlorpyrifos, and 0.05–50 μg/L for both malathion and diazinon pesticides. Good repeatability and recoveries were obtained in the range of 78.54–86.73% for three pesticides under the optimized experimental conditions. The limit of detection ranged from 0.02 to 0.03 μg/L, and the limit of quantification ranged from 0.05 to 0.1 μg/L for all three pesticides. Finally, the developed method was successfully applied for the determination of three targeted pesticides in milk, apples, and drinking water samples each in triplicate. No pesticide was found in apple and milk samples, but chlorpyrifos was found in one drinking water sample below the quantification level.     

Reversed-phase liquid chromatography/electrospray ionization/mass spectrometry with isotope dilution for the analysis of nitrate and nitrite in water

A new method was developed for the analysis of nitrate and nitrite in a variety of water matrices by using reversed-phase liquid chromatography/electrospray ionization/mass spectrometry in the negative ion mode. For this direct analysis method, nitrate and nitrite anions were well separated under the optimized LC conditions, detected by monitoring m/z 62 and m/z 46 ions, and quantitated by using an isotope dilution technique that utilized the isotopically labeled analogs. The method sensitivity, accuracy, and precision were investigated, along with matrix effects resulting from common inorganic matrix anions. The isotope dilution technique, along with sample pretreatment using barium, silver, and hydrogen cartridges, effectively compensated for the ionization suppression caused by the major water matrix anions, including chloride, sulfate, phosphate, and carbonate. The method detection limits, based on seven reagent water replicates fortified at 0.01 mg N/L nitrate and 0.1 mg N/L nitrite, were 0.001 mg N/L for nitrate and 0.012-0.014 mg N/L for nitrite. The mean recoveries from the replicate fortified reagent water and lab water samples containing the major water matrix anions, were 92-103% for nitrate with an imprecision (relative standard deviation, RSD) of 0.4-2.1% and 92-110% for nitrite with an RSD of 1.1-4.4%. For the analysis of nitrate and nitrite in drinking water, surface water, and groundwater samples, the obtained results were generally consistent with those obtained from the reference methods. The mean recoveries from the replicate matrix spikes were 92-123% for nitrate with an RSD of 0.6-7.7% and 105-113% for nitrite with an RSD of 0.3-1.8%.     

Direct determination of non-steroidal anti-inflammatory drugs by column-switching LC-MS

A method for determination of 16 non-steroidal anti-inflammatory drugs (NSAIDs) in human plasma samples without time-consuming sample pre-treatments was developed. The system consisted of two pumps for mobile phase delivery, a six-port switching valve, a pre-column (Oasis HLB Cartridge Column), and a reversed phase analytical column (COSMOSIL 3C18-MS-II). The analytes were trapped on the precolumn and subsequently separated on the analytical column. The present method allowed on-line sample clean-up and enrichment, leading to improved sensitivity without any tedious sample preparation. The recoveries of NSAIDs from human plasma by column-switching were greater than 72.6%. The total analysis time for a single analytical run was approximately 11 min. The detection limits of NSAIDs were 0.0025 to 0.2 microg/mL using the selected ion monitoring mode.     

Selective and sensitive determination of bis(7)-tacrine, a high erythrocyte binding acetylcholinesterase inhibitor, in rat plasma by high-performance liquid chromatography-tandem mass spectrometry

The current study aims to develop a specific and sensitive LC-MS/MS method for determination of bis(7)-tacrine (B7T) in rat plasma. A 100 microL plasma sample was extracted with ethyl acetate. B7T and the internal standard (IS), pimozide, in the samples were then analyzed with LC-MS/MS in positive electrospray ionization condition. Chromatographic separation of B7T and IS was achieved in a C(18) reversed-phase HPLC column (150 x 2.1 mm i.d.) by isocratic elution with a mobile phase consisting of 0.05% formic acid in water and acetonitrile (1:1, v/v) at a flow rate of 0.35 mL/min. Multiple-reaction monitoring (MRM) mode was employed to measure the ion transitions: m/z 247 to 197 for B7T and m/z 462 to m/z 328 for IS, respectively. The method was linear over the studied ranges of 100-5000 and 10-100 ng/mL. The intra-day and inter-day variations of the analysis were less than 6.8% with standard errors less than 9.0%. The detection limit of B7T in rat plasma was 1 ng/mL. The developed method was successfully applied to the pharmacokinetic study of B7T after intravenous administration of 1 mg/kg B7T and further proved to be readily utilized for determination of B7T in rat plasma samples.     

Static headspace and purge-and-trap gas chromatography for epichlorohydrin determination in drinking water

Epichlorohydrin (ECH) can enter drinking-water supplies due to leaching from epoxy resins in contact with water and/or through the use of flocculating water treatment agents. Potential human exposure from drinking waters poses a particular concern on account of toxicological studies showing severe acute and long-term toxic effects of ECH. Recently a parametric value of 0.1 μg/L for ECH in drinking water has been established by European Union.A few methods for ECH determination in water are available. However, they usually adopt cumbersome procedures for sample preparation and provide sensitivity not matching the EU criteria for water monitoring purposes.In this study we investigated the analytical performance of gas extraction techniques, such as static headspace (HS) and purge and trap (P&T), coupled to gas chromatography (GC) with an electron capture detector (GC-ECD) for the determination of ECH in drinking water. The influence of different parameters affecting the analytical response was studied in details in order to enhance the method sensitivity, thus fulfilling the regulatory requirements.The P&T GC-ECD method was proved capable of determining ECH in water for human consumption at a detection limit of 0.01 μg/L fully complying the regulatory levels. On the contrary, the HS GC-ECD method is far less sensitive (LOD≅40 μg/L) than the previous cited method. The P&T GC-ECD method is simple, rapid, automated, safe for operators and does not require large sample volumes. Therefore, it is useful for routine laboratory activities both for control and research actions.     

Development of a solvent-free method for the simultaneous identification/quantification of drugs of abuse and their metabolites in environmental water by LC-MS/MS

This work details a rapid analytical method using direct sample injection for the simultaneous identification/quantification of 22 drugs of abuse, including some of their major metabolites, in environmental samples. This has been developed using a hybrid triple quadrupole-linear ion trap-mass spectrometer (QqLIT). With the increasing sensitivity of today's tandem mass spectrometers, direct injection analysis of water samples has become an attractive alternative to traditional analytical protocols, which often include a preliminary pre-concentration step. What's more, this kind of analysis is in accordance with many of the main objectives of so-called green analytical chemistry, or environmentally friendly practice. The analytical performance of the LC-MS/MS method was evaluated in three different water matrices (surface water, influent and effluent wastewater). Data acquisition was carried out in selected reaction monitoring (SRM) mode under time-scheduled conditions, monitoring two SRM transitions for simultaneous identification/quantification of all target compounds in the samples. Additionally, an experiment was performed using the information-dependent acquisition (IDA) scan to carry out the identification of those analytes for which the second transition was present at a low intensity. Finally, the two methodologies developed were applied to real samples for evaluation.     

Simultaneous determination of toxins in algae and water samples by high-performance liquid chromatography with triple quadrupole mass spectrometry

A facile method based on liquid chromatography coupled with electrospray ionization tandem triple quadrupole mass spectrometry working in selected reaction monitoring mode has been established to analyze toxins in the algae and water samples. Twelve types of toxins (anatoxin, cylindrospermopsin, dinophysistoxin-1, nodularin, okadaic acid, microcystins) were efficiently separated under optimized liquid chromatography coupled with mass spectrometry conditions in the selected reaction monitoring mode. Correlation coefficients of the calibration curves, all felt in the range of 0.9958-0.9998, indicated good linearity. The detection limits of toxins in this method were all lower than 0.20 ng/mL and the quantification limits were in the range from 0.04 to 0.60 ng/mL. Except for anatoxin, cylindrospermopsin, and nodularin, the other toxins' recoveries varied from 55.45 to 140.85%. And the relative standard deviations of interday and intraday precision were at 8.61% (n = 5). The high-performance liquid chromatography (HPLC)/electrospray ionization (ESI)-mass spectrometery (MS) method was also successfully applied to analyze the algae and water samples. Owing to its exclusive selectivity and excellent sensitivity, the developed method is a tool for comprehensive analyses of the 12 types of toxins at nanogram levels.