Analysis of thiamine in dried yeast by high-performance liquid chromatography and high-performance liquid chromatography/atmospheric pressure chemical ionization-mass spectrometry

Summary High-performance liquid chromatography (HPLC) and high-performance liquid chromatography/atmospheric pressure chemical ionization-mass spectrometry (HPLC/APCI-MS) have been applied to the analysis of thiamine in dried yeast. Thiamine was extracted from dried yeast with isobutanol containing sodium 1-octanesulfonate as an ion-pairing agent and determined by HPLC on a reversed phase ODS column with UV detection at 254 nm. Response was linear in the range 25–300 μg/g of thiamine in dried yeast with a coefficient of variation in the reproducibility of 8.0%. Thiamine was recovered in good yield (109.2%, n=5). Identification of the thiamine peak was obtained by the mass spectrum using the HPLC/APCI-MS system. The utility of the selected ion monitoring technique using the HPLC/APCI-MS was also investigated. The results obtained by this method are in good agreement with those obtained by the thiochrome method [1].     

液相色谱-大气压化学电离离子阱质谱法测定烟草中的游离茄尼醇

用液相色谱/大气压化学电离离子阱质谱建立了一种分析烟草中游离茄尼醇的方法。烟草样品用甲醇振荡提取30 min,在分析前无需进行其它前处理。在1.8μm快速分离C18色谱短柱上用V(甲醇)∶V(异丙醇)=85∶15等梯度洗脱实现了茄尼醇的快速分离。用不带碰撞能量的二级质谱全扫描选择监测离子m/z 613.6进行定量,检出限为0.4μg/L,RSD为1.1%,两种添加量的回收率分别为97%和99%。方法应用于不同烟草和烟草制品样品的检测分析。     

Determination of quaternary ammonium compounds in seawater samples by solid-phase extraction and liquid chromatography-mass spectrometry

A method for the simultaneous determination of two biocidal quaternary ammonium compounds; didecyldimethylammonium chloride (didecyldimethyl quat) and dodecylbenzyldimethylammonium chloride (benzyl quat), in seawater by solid phase extraction (SPE) followed by liquid chromatography-mass spectrometry (LC-MS) was developed. The optimised procedure utilised off-line extraction of the analytes from seawater using polymeric (Strata-X) SPE cartridges. Recoveries ranged from 80 to 105%, with detection limits at the low parts-per-trillion (ng/l) level for both analytes. To demonstrate sensitivity, environmental concentrations were measured at three different locations along the North East coast of England with measured values in the range 120-270ng/l.     

Determination of benzoylurea insecticide residues in tomatoes by high-performance liquid chromatography with ultraviolet-diode array and atmospheric pressure chemical ionization-mass spectrometry detection

A simple and sensitive method using high-performance liquid chromatography/ mass spectrometry (LC/MS) was developed and validated for simultaneous determination of 5 benzoylurea insecticides-diflubenzuron, triflumuron, teflubenzuron, lufenuron, and flufenoxuron-in tomatoes. Residues were successfully separated on a C18 column by methanol-water isocratic elution. Detection was carried out by an ultraviolet diode array detector (UV-DAD) coupled with a quadrupole mass spectrometer, using atmospheric pressure chemical ionization (APCI) in negative-ion mode. The main ions were the deprotonated molecules [M-H]- for triflumuron, and the anions formed by elimination of hydrofluoric acid [M-H-HF]- for diflubenzuron and flufenoxuron, and [M-2H-HF] for lufenuron and teflubenzuron. The calibration plots were linear for both detectors over the range 0.05 to 10 microg/mL, and the method presented good quality parameters. The limits of detection for standard solutions were 0.008-0.01 mg/L (equivalent to 0.08-0.1 ng injected) for both detectors, and the limits of quantification (LOQs) were approximately 10 times lower than national maximum residue levels (MRLs). Depending on the compound and the detector, the LOQ values ranged from 0.2 to 0.4 ng injected. The optimum LC-UV-DAD/APCI-MS conditions were applied to the analysis of benzoylureas in tomatoes. The obtained recoveries from fortified tomato samples (50 g), extracted with ethyl acetate and purified by solid-phase extraction on silica sorbent, were 88-100 and 92.9-105% for the UV-DAD and MS detectors, respectively, with precision values (relative standard deviations) of 2.9-11 and 3.7-14%, respectively. The method was applied to 12 tomato samples from local markets, and diflubenzuron and lufenuron were detected in only one sample at concentrations lower than the MRLs. The results indicate that the developed LC/MS method is accurate, precise, and sensitive for quantitative and qualitative analysis at low levels of benzoylureas required by legislation.     

Determination of polycyclic aromatic hydrocarbons in fractions in asphalt mixtures using liquid chromatography coupled to mass spectrometry with atmospheric pressure chemical ionization

An analytical method using liquid chromatography coupled to mass spectrometry with atmospheric pressure chemical ionization for the determination of polycyclic aromatic hydrocarbons in asphalt fractions has been developed. The 14 compounds determined, characterized by having two or more condensed aromatic rings, are expected to be present in asphalt and are considered carcinogenic and mutagenic. The parameters of the atmospheric pressure chemical ionization interface were optimized to obtain the highest possible sensitivity for all of the compounds. The limits of detection ranged from 0.5 to 346.5 μg/L and the limits of quantification ranged from 1.7 to 1550 μg/L. The method was validated against a diesel particulate extract standard reference material (NIST SRM 1975), and the obtained concentrations agreed with the certified values. The method was applied to asphalt samples after its fractionation according to ASTM D4124 and the method of Green. The concentrations of the seven polycyclic aromatic hydrocarbons quantified in the sample ranged from 0.86 mg/kg for benzo[ghi]perylene to 98.32 mg/kg for fluorene.     

Determination method for steroid 5alpha-reductase activity using liquid chromatography/atmospheric pressure chemical ionization-mass spectrometry.

A determination method for steroid 5alpha-reductase activity using liquid chromatography/atmospheric pressure chemical ionization-mass spectrometry (LC/APCI-MS) in the positive-ion mode has been developed. The rat prostatic enzyme source was used and the enzymatically formed 5alpha-dihydrotestosterone and 5a-androstane-3alpha,17beta-diol were determined by LC/APCI-MS using absolute calibration curve method. The sum of the formed products was used as a measurement of the enzyme activity. This method was applied to kinetic study of this enzyme and inhibitory experiments using Finasteride as a model inhibitor.     

Rapid analysis of six trace trichlorophenols in seawater by magnetic micro‐solid‐phase extraction and liquid chromatography with tandem mass spectrometry

A new facile, rapid, inexpensive, and sensitive method for the analysis of six trace trichlorophenols in seawater samples was developed by magnetic micro‐solid‐phase extraction coupled to liquid chromatography with tandem mass spectrometry. Core–shell covalently functionalized ferroferric oxide coated with aminated silicon dioxide and decorated with multiwalled carbon nanotubes was applied as an adsorbent to perform the extraction process. The effect of factors including solution pH, contact time, adsorbent amount, and ionic strength were investigated in detail. The obtained results revealed that the proposed adsorbent was a highly effective and low‐cost magnetic micro‐solid‐phase extraction material for the enrichment of 2,3,4‐trichlorophenol, 2,3,5‐trichlorophenol, 2,3,6‐trichlorophenol, 2,4,5‐trichlorophenol, 2,4,6‐trichlorophenol, and 3,4,5‐trichlorophenol from seawater. Under the optimized conditions, the recoveries ranged from 88.0 to 99.5% at the three spiking levels, the limits of detection and the limits of quantification were 0.002 and 0.007 μg/L for the six trichlorophenols, respectively. The intra‐ and interday relative standard deviations were 2.0–6.7 and 4.5–8.9%, respectively. The calibration curves showed a good linearity in the range of 0.02–5.0 μg/L. The routine run analyses showed that the developed method was fast, simple, accurate, solvent‐saving and high resolution, and it was suitable for the determination of trace trichlorophenols in seawater.     

Determination of aflatoxins in olive oil by liquid chromatography-tandem mass spectrometry

A liquid chromatography-tandem mass spectrometric with electrospray ionization (LC/ESI-MS/MS) method for determining the four naturally occurring aflatoxins (AFs) B1, B2, G1, and G2 in olive oil is proposed. AFs were extracted from oil sample by means of matrix solid phase dispersion (MSPDE), utilizing C18 as dispersing material. No further purification step, such as lipid removal, was performed. Aflatoxin M1, the hepatic metabolite of AFB1, was employed as internal standard. Olive oil extract was analyzed by LC/ESI-MS/MS in positive ionization mode, with multireaction monitoring acquisition. Due to a signal suppression ranging between 4 and 23%, quantitation was performed by matrix-matched calibration curves. The regression line coefficients of determination were above 0.9991. Sample recoveries ranged from 92 to 107%, with relative standard deviations below 13% for spiking levels between 0.5 and 5 ng g⁻¹; method quantification limits ranged between 0.04 and 0.12 ng g⁻¹. The developed LC/ESI-MS/MS method, although not as sensitive as LC coupled to fluorescence detection, is rapid, selective, accurate and precise, thus it can be used as confirmatory assay. The MSPDE appears suitable for application to other oleaginous matrices and for multiresidue investigation.     

分散固相萃取-液相色谱-串联质谱法测定农产品中吡氟甲禾灵

应用液相色谱-串联质谱联用技术,建立了农产品中吡氟甲禾灵的分析方法.样品经乙腈提取,无水Mg2SO4和NaCl混合盐盐析,N-丙基乙二胺、C18填料分散固相萃取净化;采用乙腈和5 mmol/L甲酸铵水溶液为流动性,二元梯度洗脱,C18(2.1×150 mm,3.5 μm)色谱柱分离;电喷雾正离子模式采集,多反应监测模式...     

Liquid chromatography/atmospheric pressure ionization-mass spectrometry in drug metabolism studies

The study of the metabolic fate of drugs is an essential and important part of the drug development process. The analysis of metabolites is a challenging task and several different analytical methods have been used in these studies. However, after the introduction of the atmospheric pressure ionization (API) technique, electrospray and atmospheric pressure chemical ionization, liquid chromatography/mass spectrometry (LC/MS) has become an important and widely used method in the analysis of metabolites owing to its superior specificity, sensitivity and efficiency. In this paper the feasibility of LC/API-MS techniques in the identification, structure characterization and quantitation of drug metabolites is reviewed. Sample preparation, LC techniques, isotope labeling, suitability of different MS techniques, such as tandem mass spectrometry, and high-resolution MS in drug metabolite analysis, are summarized and discussed. Automation of data acquisition and interpretation, special techniques and possible future trends are also the topics of the review.     

Identification of degradation products of antioxidants in polyolefins by liquid chromatography combined with atmospheric pressure photoionisation mass spectrometry

Round robin tests have revealed the trend that the concentration of stabilizers in polyolefins is usually underestimated. However, it is still unclear whether this underestimation is due to systematic errors of the analysis procedures or to degradation of the stabilizers during the production of the round robin sample itself. Within the present work, the degradation pathways of six common antioxidants (ADK Stab AO-60, Everfos 168, Kinox 30, Irganox 3114, Irganox 1076, and Cyanox 1790) were investigated. Methods based on high-performance liquid chromatography with UV detection or hyphenated with mass spectrometry (employing either an ion trap or a quadrupole/time-of-flight instrument) were developed, whereby the suitability of atmospheric pressure photoionisation was studied and compared with the performance of more established ionisation techniques like electrospray ionisation and atmospheric pressure chemical ionisation. While ADK Stab, Kinox 30, Everfos 168, and Irganox 1076 turned out to be thermally stable at 115 °C, Irganox 3114 and Cyanox 1790 were partly degraded by oxidation. In the presence of talcum, which is a widely used inorganic filler for polyolefins, additional degradation reactions such as the cleavage of ester bonds and the loss of tert-butyl groups were observed at elevated temperature.     

Determination of eight nitrosamines in water at the ng L levels by liquid chromatography coupled to atmospheric pressure chemical ionization tandem mass spectrometry

In this work, we have developed a sensitive method for detection and quantification of eight N-nitrosamines, N-nitrosodimethylamine (NDMA), N-nitrosomorpholine (NMor), N-nitrosomethylethylamine (NMEA), N-nitrosopirrolidine (NPyr), N-nitrosodiethylamine (NDEA), N-nitrosopiperidine (NPip), N-nitroso-n-dipropylamine (NDPA) and N-nitrosodi-n-butylamine (NDBA) in drinking water. The method is based on liquid chromatography coupled to tandem mass spectrometry, using atmospheric pressure chemical ionization (APCI) in positive mode with a triple quadrupole analyzer (QqQ). The simultaneous acquisition of two MS/MS transitions in selected reaction monitoring mode (SRM) for each compound, together with the evaluation of their relative intensity, allowed the simultaneous quantification and reliable identification in water at ppt levels. Empirical formula of the product ions selected was confirmed by UHPLC-(Q)TOF MS accurate mass measurements from reference standards.Prior to LC–MS/MS QqQ analysis, a preconcentration step by off-line SPE using coconut charcoal EPA 521 cartridges (by passing 500 mL of water sample) was necessary to improve the sensitivity and to meet regulation requirements. For accurate quantification, two isotope labelled nitrosamines (NDMA-d₆ and NDPA-d₁₄) were added as surrogate internal standards to the samples.The optimized method was validated at two concentration levels (10 and 100 ng L⁻¹) in drinking water samples, obtaining satisfactory recoveries (between 90 and 120%) and precision (RSD < 20%). Limits of detection were found to be in the range of 1–8 ng L⁻¹. The described methodology has been applied to different types of water samples: chlorinated from drinking water and wastewater treatment plants (DWTP and WWTP, respectively), wastewaters subjected to ozonation and tap waters.     

Identification of anthocyanins in wines by liquid chromatography, liquid chromatography-mass spectrometry and nuclear magnetic resonance

Liquid chromatography (LC) was used for the fractionation of particular anthocyanins in glycoside form from methanol extracts of red grape skins and solid phase extracts of red wine. By the combination of nuclear magnetic resonance spectroscopy and LC-mass spectroscopy the identification of 13 anthocyanins in a particular LC fraction and hence the in particular peaks in chromatograms were obtained. Peaks areas in the chromatograms obtained under the semi-quantitaive conditions of the solid phase extracts of red wines Pinot Noir, Cabernet Sauvignon and Merlot from the Coastal wine-growing region in Slovenia, produced in 1999, were used as input data in chemometric analysis. The chemometric methods used were hierarchical clustering analysis and regularised discriminant analysis. The results of both methods give 100% correct classification of wines regarding the vine variety.     

液相色谱-质谱法测定饲料中阿维菌素类药物

建立了饲料中阿维菌素类药物(阿维菌素、多拉菌素、埃普菌素和伊维菌素)液相色谱-质谱(LC-MS)检测法. 用乙腈提取样品中的药物, 加水稀释, 加三乙胺调节pH, 经C18固相萃取柱净化, LC-MS法测定. 结果表明, 方法平均回收率为91.3%～99.8%, RSD为2.9%～15% (n=4), 配合饲料、浓缩饲料和预混合饲料中的检出限均为10 μg/kg; 定量限均为20 μg/kg. 方法可用于饲料样品中阿维菌素类药物残留量的确证检测.     

Determination of polymer additives by liquid chromatography coupled with mass spectrometry. A comparison of atmospheric pressure photoionization (APPI), atmospheric pressure chemical ionization (APCI), and electrospray ionization (ESI)

A method for the determination of polymer additives like antioxidants, UV absorbers and processing stabilizers using liquid chromatography (LC) coupled with atmospheric pressure photoionization mass spectrometry (APPI-MS) is presented. Ion source parameters were optimized regarding temperatures, gas flow rates, and voltages applied. Detection limits were determined using APPI with or without dopant and were compared with electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI). Differences between APPI, ESI and APCI are pointed out and the effect of the dopant toluene and acetone is discussed. The optimized method yielded detection limits between 0.001 mg L⁻¹ and 0.022 mg L⁻¹ for 15 different analytes. Linear calibration plots could be obtained for all solutes over a wide concentration range showing satisfying repeatability with standard deviations of peak areas between 3.4% and 7.6%. The results indicate that the developed method can be regarded as suitable for the quantitative determination of polymer additives even at low concentration levels.     

液相色谱-质谱联用法测定血液中全氟化合物

研究了快速溶剂萃取-液相色谱/质谱联用技术测定血液中PFAAs的方法。血液样品经过冷冻干燥,利用加速溶剂萃取的方法,最后使用液相色谱-质谱仪分析检测PFAAs成分。方法的回收率为74.6%~128.8%,检出限为1.10~25.1 ng/L。通过对珠江三角洲地区人群血液样本的分析,发现∑9PFAAs的浓度为26.8~557 ng/g,平均值为176±90.1 ng/g。血液中PFAAs的主要成分以PFHxA和PFOS为主,分别占血液中PFAAs浓度的20.97%和66.98%。人群血液中最常见和浓度最高的PFAAs是PFOS,而PFOA浓度相对较低。     

Atmospheric pressure photoionization-mass spectrometry and atmospheric pressure chemical ionization-mass spectrometry of neurotransmitters

A group of five neurotransmitters with different properties was analyzed using atmospheric pressure photoionization (APPI) and atmospheric pressure chemical ionization-mass spectrometry (APCI-MS). The sensitivity of the techniques for the analytes was tested in six solvents and in positive and negative ion modes. APPI was found to be superior in sensitivity for all the compounds in both positive and negative ion modes. In positive ion mode, water/methanol/formic acid was found to be the best solvent, whereas in negative ion mode, water/methanol/ammonium hydroxide performed best. Detection limits using APPI were between 2.5-250 fmol, depending on the compound. The sensitivity was best for the neurosteroids dehydroepiandrosterone and beta-estradiol, and acetylcholine (LOD 2.5-10 fmol).     

蔬菜中阔草清等8种农药残留量的高效液相色谱-质谱分析

建立了固相萃取-高效液相色谱-电喷雾质谱法同时测定蔬菜中的阔草清、西玛津、硫双威、绿麦隆、扑草净、仲丁威、马拉硫磷和二嗪农等8种农药的分析方法.蔬菜用乙腈超声波提取,经过ODS-C18固相萃取小柱富集纯化.采用C18柱分离,以体积分数0.03%甲酸乙腈-体积分数0.03%甲酸水溶液为流动相,线性梯度洗脱,以保留时间和质荷比对分离出的组分进行定性,用峰面积进行定量.结果表明,8种农药的质量浓度与其峰面积在一定的范围内呈良好的线性关系,检出限为0.1～5.0 μg/L,相关系数为0.9939～0.9998,样品的加标平均回收率为83%～106%,相对标准偏差为3.1%～9.8%.方法适用于蔬菜中阔草清等8种农药残留量的分析.     

Determination of nitrate in environmental water samples by conversion into nitrophenols and solid phase extraction−spectrophotometry, liquid chromatography or gas chromatography-mass spectrometry

Conversion of nitrate into a nitro-phenol derivative by reaction with 2-methylphenol or 2,6-dimethylphenol allowed at least 100-fold enrichment of the derivative on Lichrolut EN polymeric cartridge, and it is stable for up to 1 month on the cartridge. The derivative could be eluted with ammonia-methanol mixture. This reaction for nitrate determination has permitted a choice of final measurement by UV-Vis spectrophotometry, liquid chromatography or gas chromatography-mass spectrometry when the limits of detection were 10, 6 and 3 μg l⁻¹, respectively, and the calibration range 20 μg to 10 mg l⁻¹ nitrate. The method has been validated by spiking natural water samples, when the recovery of nitrate was 98.5-108.4% (relative standard deviation 2.5-6.1%).     

高效液相色谱-质谱联用法测定纺织品中的含氯苯酚

建立了高效液相色谱-质谱联用法检测纺织品中五氯苯酚(PCP)、四氯苯酚(TeCP)。选用ZORBAX XDB-C18柱(50 mm×2.1 mm,3.5μm)为分析柱,流动相为V(甲醇)∶V(纯水)=88∶12,流速为200μL/min;质谱条件选用气动辅助电喷雾离子源(ESI),检测方式为负离子多离子反应检测(MRM);PCP、TeCP标准曲线线性范围均为0.1~100μg/L;回收率为90%~99%;相对标准偏差为3.5%~7.6%(n=5);方法检测低限为5μg/kg。方法适用于纺织品中PCP、TeCP的测定。