Simultaneous determination of nine anticoagulant rodenticides in soil and water by LC–ESI‐MS

A new and sensitive analytical method is presented to determine nine anticoagulant rodenticide (chlorophacinone, bromadiolone, pindone, diphacinone, warfarin, coumatetralyl, brodifacoum, floucomafen, and difenacoum) residues in water and soil samples by LC–ESI‐MS. Rodenticides were extracted from soil using a methanol and ammonium formate 30 mM mixture, while ethyl acetate was employed in the water samples. A Gemini 5 μm C₁₈ column was employed, and a mobile phase comprising a mixture of ammonium formate 30 mM and di‐n‐butylamine 30 mM in water (pH 3.5), ammonium formate 30 mM and di‐n‐butylamine 20 mM in water (pH 4.4), ammonium formate 30 mM in water (pH 6.5), and methanol in a gradient elution mode was selected. The method was fully validated and it was found to be selective and precise in terms of linearity and accuracy. Extraction recoveries ranged from 90 to 104% for the compounds studied, while the detection and quantification limits were between 0.09 and 2.2 μg/kg in soil or 0.08 and 1.7 μg/L in water. The method was applied to simultaneously measure these compounds in water and soil samples.     

Liquid chromatography with atmospheric pressure chemical ionization and electrospray ionization mass spectrometry of flavonoids with triple-quadrupole and ion-trap instruments

With 15 flavonoids as test compounds, the analytical performance of four modes of LC-MS, multiple MS (MSn) and tandem MS operation (atmospheric pressure chemical ionization (APCI), electrospray ionization, positive and negative ionization) was compared for two mass spectrometers, a triple-quadrupole and an ion-trap instrument. Two organic modifiers, methanol and acetonitrile, and two buffers, ammonium acetate and ammonium formate, were used. In general, the use of APCI in the negative ion mode gave the best response, with the signal intensities and the mass-spectral characteristics not differing significantly between the two instruments. The best results were obtained when methanol-ammonium formate (pH 4.0) was used as LC eluent. Under optimum conditions full-scan limits of detection of 0.1-30 mg/l were achieved in the negative APCI mode. Here it needs to be emphasized that up to 2-order response differences were found both between analytes and between modes of ionization. This implies that one should be very cautious when interpreting data on the screening of real-life samples. The main fragmentations observed in the MSn spectra on the ion-trap, or the tandem MS spectra on the triple-quadrupole were generally the same. The advantage of the former approach is the added possibility to ascertain precursor-->product ion relationships.     

Effect of eluent on the ionization efficiency of flavonoids by ion spray, atmospheric pressure chemical ionization, and atmospheric pressure photoionization mass spectrometry.

The effect of nine different eluent compositions on the ionization efficiency of five flavonoids was studied using ion spray (IS), atmospheric pressure chemical ionization (APCI), and the novel atmospheric pressure photoionization (APPI), in positive and negative ion modes. The eluent composition had a great effect on the ionization efficiency, and the optimal ionization conditions were achieved in positive ion IS and APCI using 0.4% formic acid (pH 2.3) as a buffer, and in negative ion IS and APCI using ammonium acetate buffer adjusted to pH 4.0. For APPI work, the eluent of choice appeared to be a mixture of organic solvent and 5 mM aqueous ammonium acetate. The limits of detection (LODs) were determined in scan mode for the analytes by liquid chromatography/mass spectrometry using IS, APCI and APPI interfaces. The results show that negative ion IS with an eluent system consisting of acidic ammonium acetate buffer provides the best conditions for detection of flavonoids in mass spectrometry mode, their LODs being between 0.8 and 13 microM for an injection volume of 20 microl.     

Effect of ammonium formate as ionizing additive in thermospray liquid chromatography-mass spectrometry for the determination of triazine,phenylurea and chlorinated phenoxyacetic acid herbicides

A comparison between the use of ammonium acetate and ammonium formate in thermospray liquid chromatography-mass spectrometry with positive and negative ion modes using ‘filament-on’ mode has been applied for the determination of simazine, atrazine, propazine, monuron, diuron, linuron, 2,4,-D, 2,4,5-T and silvex. By using ammonium formate, the positive ion mode showed for triazine and phenylurea herbicides [M + H]⁺ and [M + NH₄]⁺, respectively, and the formation of other adduct ions different from ammonium acetate. In the negative ion mode, chlorinated phenoxyacetic acid herbicides exhibited [M + acetate]^? or [M + formate]^?, depending on the ionizing additive. Applications are reported for the determination of triazine and chlorinated phenoxyacetic acid herbicides in spiked soil and water samples, respectively.     

Ionization mechanism in gel permeation chromatography mass spectrometry (GPC-MS) with atmospheric pressure chemical ionization (APCI) interface

The ionization mechanism in gel permeation chromatography (GPC) coupled with mass spectrometry (MS) using an atmospheric pressure chemical ionization (APCI) interface is explained when chloroform is used as GPC solvent. The even electron anions [CHCl₃+Cl]^? generated by thermal electrons in negative APCI mode are responsible for further ionization of the solute compounds as [M?+?Cl]^? adducts. In positive APCI mode, the contaminants in chloroform generate a relatively high background noise. These cations can be suppressed by adding 10% of tetrahydrofuran (THF). Supporting the described mechanism are key experiments done in the absence of solvent, in GPC solvents and using a mixture of anionic polystyrene (PS) standards from dimer up to 12,000?g/mol, covering the molecular masses of great interest in studies related to Registration, Evaluation, Authorization, and Restriction of Chemicals (REACH) and Food and Drug Administration (FDA). Advantages of suppressing the oligomer signals for polymer additive analyses were presented using Irgafos^® 168.     

Development and validation of a liquid chromatography with mass spectrometry method to determine resveratrol and piceid isomers in beeswax

This paper represents the first report of a liquid chromatography coupled to electrospray ionization mass spectrometry method for simultaneously analyzing resveratrol and piceid isomers (cis and trans) in beeswax. An efficient extraction procedure has been proposed (average analyte recoveries were between 89 and 95%); this involved a solid–liquid extraction using a mixture of ethanol and water (80:20, v/v) and a concentration step in a rotary evaporator. The separation of all the compounds was achieved using a C₁₈ column and a mobile phase composed of ammonium formate 0.03 M in water and acetonitrile in gradient elution mode at a flow rate of 1 mL/min. The method was fully validated in terms of selectivity, limits of detection and quantification, linearity, precision, and accuracy. The limits of detection and quantification ranged from 1.0 to 1.7 and 3.5 to 5.5 μg/kg, respectively. Finally, the proposed method was applied to analyze beeswax samples collected from experimental and organic apiaries.     

Gaseous acidity and basicity scales as guides to chemical ionization in reversed-phase liquid chromatography-mass spectrometry with direct liquid introduction

During direct liquid introduction (DLI) liquid chromatography-mass spectrometry (LC-MS), the detectability of acetone is shown to be predictable, based on consideration of the gas-phase acidities and basicities of solvents methanol and acetonitrile and modifiers formic acid and ammonium formate. Consequently, ion formation in DLI LC-MS resembles gas-phase chemical ionization processes; since the order of acidities is altered in solution, solution ionization must be much less important than gas-phase. Ion populations could be predicted on the basis of gas-phase proton affinities and acidities: acetone could be detected in all solvent mixture by positive ions, but it was not readily detected by negative ions when acid was also present. In solvents without additives it was always detected.     

反相液相色谱-质谱法使用甲酸甲胺改善甘油三酯电喷雾离子化检测灵敏度

提出使用甲酸甲胺作为新型电离增强剂改善反相液相色谱-电喷雾质谱(LC-ESI-MS)检测甘油三酯灵敏度的方法.使用反相C18色谱柱,以玉米油的异丙醇溶液为样品,选择文献中常用的异丙醇-乙腈-甲醇-水,异丙醇-乙腈流动相,在考察甲酸、乙酸、甲酸铵、乙酸铵、甲酸丁胺、甲酸二丁胺、甲酸三乙胺、甲酸二乙胺、甲酸甲胺、甲酸乙胺等不同电离增强剂的基础上,比较了甲酸甲胺和常用的甲酸铵电离增强剂对LC-ESI-MS分析甘油三酯检测灵敏度的影响,结果表明,甲酸甲胺可以使其中三亚油酸甘油酯组分的质谱峰响应值和信噪比均约为使用甲酸铵的5倍.考察了使用甲酸甲胺时,甲酸甲胺电离增强剂的浓度、流动相流速以及雾化气流速对检测的影响.通过测定不同玉米油浓度与其中甘油三酯总离子流色谱峰面积的关系曲线,显示玉米油中甘油三酯组分在不同流动相的电喷雾过程中出现聚集的最小浓度相差不大,三亚油酸甘油酯峰面积与浓度在7×10-7~2×10-4 mol/L范围内的线性关系较好,相关系数R2=0.9997,在更高的浓度时则峰面积增加缓慢.根据实验数据分析甲酸甲胺改进检测的机理,提出含有疏水性基团的加合甲胺单电荷离子具有较低的溶剂化能,在雾滴表面富集的加合甲胺离子容易被蒸发,从而提高了电喷雾离子化效率.本方法为LC-ESI-MS分析食用油中甘油三酯时提高检测灵敏度提供了有效途径.     

Determination of silodosin and its active glucuronide metabolite KMD‐3213G in human plasma by LC–MS/MS for a bioequivalence study

A sensitive and selective liquid chromatography–tandem mass spectrometry (LC–MS/MS) method is described for the simultaneous determination of silodosin (SLD) and its active metabolite silodosin β‐d ‐glucuronide (KMD‐3213G) in human plasma. Liquid–liquid extraction of plasma samples was carried out with ethyl acetate and methyl tert‐butyl ether solvent mixture using deuterated analogs as internal standards. The extraction recoveries of SLD and KMD‐3213G were in the ranges 90.8–93.4 and 87.6–89.9%, respectively. The extracts were analyzed on a Symmetry C₁₈ (50 × 4.6 mm, 5 μm) column under gradient conditions using 10 mm ammonium formate in water and methanol–acetonitrile (40:60, v/v), within 6.0 min. For MS/MS measurements, ionization of the analytes was carried out in the positive ionization mode and the transitions monitored were m/z 496.1 → 261.2 for SLD and m/z 670.2 → 494.1 for KMD‐3213G. The method showed good linearity, accuracy, precision and stability in the range 0.10–80.0 ng/mL for SLD and KMD‐3213G. The IS‐normalized matrix factors obtained were highly consistent, ranging from 0.962 to 1.023 for both analytes. The method was used to support a bioequivalence study of SLD and its metabolite in healthy volunteers after oral administration of 8 mg silodosin capsules.     

Ultra high performance supercritical fluid chromatography coupled with tandem mass spectrometry for screening of doping agents. I: Investigation of mobile phase and MS conditions

The conditions for the analysis of selected doping substances by UHPSFC–MS/MS were optimized to ensure suitable peak shapes and maximized MS responses. A representative mixture of 31 acidic and basic doping agents was analyzed, in both ESI+ and ESI− modes. The best compromise for all compounds in terms of MS sensitivity and chromatographic performance was obtained when adding 2% water and 10 mM ammonium formate in the CO₂/MeOH mobile phase. Beside mobile phase, the nature of the make-up solvent added for interfacing UHPSFC with MS was also evaluated. Ethanol was found to be the best candidate as it was able to compensate for the negative effect of 2% water addition in ESI− mode and provided a suitable MS response for all doping agents.     

Determination of terbinafine in human plasma using UPLC–MS/MS: Application to a bioequivalence study in healthy subjects

A high‐throughput and sensitive ultra‐performance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS) method has been developed for the determination of terbinafine in human plasma. The method employed liquid–liquid extraction of terbinafine and terbinafine‐d7 (used as internal standard) from 100 μL human plasma with ethyl acetate–n‐hexane (80:20, v/v) solvent mixture. Chromatography was performed on a BEH C₁₈ (50 × 2.1 mm, 1.7 μm) column using acetonitrile–8.0 mm ammonium formate, pH 3.5 (85:15, v/v) under isocratic elution. For quantitative analysis, MS/MS ion transitions were monitored at m/z 292.2/141.1 and m/z 299.1/148.2 for terbinafine and terbinafine‐d7, respectively, using electrospray ionization in the positive mode. The method was validated according to regulatory guidance for selectivity, sensitivity, linearity, recovery, matrix effect, stability, dilution reliability and ruggedness with acceptable accuracy and precision. The method shows good linearity over the tested concentration range from 1.00 to 2000 ng/mL (r² ≥ 0.9984). The intra‐batch and inter‐batch precision (CV) was 1.8–3.2 and 2.1–4.5%, respectively. The method was successfully applied to a bioequivalence study with 250 mg terbinafine in 32 healthy subjects. The major advantage of this method includes higher sensitivity, small plasma volume for processing and a short analysis time.     

Simultaneous analysis of cocaine and its metabolites in urine by capillary electrophoresis-electrospray mass spectrometry using a pressurized liquid junction nanoflow interface

A new method for the simultaneous separation of cocaine and four metabolites in urine by CE-ESI-MS via a pressurized nanoliquid junction interface was developed. The resolution of cocaine, cocaethylene, benzoylecgonine, norcocaine, and ecgonine methyl ester was achieved in a polyvinyl-alcohol-coated capillary with 75 μm id × 50 cm total length, using a 15 mM ammonium formate electrolyte solution (pH 9.5) in less than 15 min. In addition, to enhance sensitivity, a field-amplified sample injection (FASI) was evaluated in terms of injection time and sample solvent composition. The limits of detection achieved with the FASI method ranged from 1.5 to 10 ng/mL for all the compounds. The detection of the studied compounds was performed using an ion-trap mass spectrometer in a positive ionization mode. A mixture of methanol:water (80:20 v/v) containing 0.1% v/v of formic acid was employed as spray liquid and delivered at ~200 nL/min. Under optimal CE-MS conditions, linearity was assessed in the concentration range of interest for all analytes with correlation coefficients r2 ≥ 0.9913. Intra- and inter-day precision provided a relative standard deviation lower than 1.54% for migration times and lower than 12.15% for peak areas. Finally, urine samples, spiked with the standard mixture, were extracted using a solid-phase extraction procedure and injected under FASI conditions, providing recoveries from 80% to 94% for all analytes.     

液相色谱-串联质谱法快速筛查减肥类中药及保健品中非法添加30种化学药

建立了中药及保健品中30种减肥类化学药的高效液相色谱-串联质谱(LC-MS/MS)快速筛查方法。实验优化了前处理方法、色谱分离条件和质谱参数。样品采用甲醇超声萃取,Agilent poroshell 120 ECC18(4.6 mm×100 mm,2.7μm)色谱柱分离,流动相为乙腈-水溶液(含10 mmol/L甲酸铵,0.1%甲酸,10%甲醇),梯度洗脱,流速0.25 m L/min,采用正负离子切换模式的电喷雾质谱检测,多反应选择离子监测(MRM)。该方法能同时筛查30种化学药,覆盖面广,简便、快速、准确可靠,已用于减肥类中药及保健品中非法添加化学药的筛查及检测。     

An Alternative Strategy for Screening and Confirmation of 330 Pesticides in Ground- and Surface Water Using Liquid Chromatography Tandem Mass Spectrometry

The presence of pesticide residues in water is a huge worldwide concern. In this paper we described the development and validation of a new liquid chromatography tandem mass spectrometric (LC-MS/MS) method for both screening and quantification of pesticides in water samples. In the sample preparation stage, the samples were buffered to pH 7.0 and pre-concentrated on polymeric-based cartridges via solid-phase extraction (SPE). Highly sensitive detection was carried out with mobile phases containing only 5 mM ammonium formate (pH of 6.8) as an eluent additive and using only positive ionization mode in MS/MS instrument. Hence, only 200-fold sample enrichment was required to set a screening detection limit (SDL) and reporting limit (RL) of 10 ng/L. The confirmatory method was validated at 10 and 100 ng/L spiking levels. The apparent recoveries obtained from the matrix-matched calibration (5–500 ng/L) were within the acceptable range (60–120%), also the precision (relative standard deviation, RSD) was not higher than 20%. During the development, 480 pesticides were tested and 330 compounds fulfilled the requirements of validation. The method was successfully applied to proficiency test samples to evaluate its accuracy. Moreover, the method robustness test was carried out using higher sample volume (500 mL) followed by automated SPE enrichment. Finally, the method was used to analyze 20 real samples, in which some compounds were detected around 10 ng/L, but never exceeded the assay maximum level.     

液相色谱-电喷雾电离质谱法检测尿液中的3种合成类固醇药物

研究建立了合成类固醇药物群勃龙、四氢孕三烯炔酮和孕三烯酮的液相色谱-电喷雾质谱的检测方法。尿样经过β-葡萄糖醛酸酶酶解和叔丁基甲醚提取后,采用Zorbax SB-C18分析柱(150 mm×2.1 mm,5 μm),在流动相为pH 3.5的甲酸铵缓冲液-乙腈的条件下进行梯度洗脱,在正离子模式下检测。考察了不同的质谱条件对这类化合物检测结果的影响。建立了人尿液中合成类固醇药物的液相色谱-电喷雾电离质谱的初筛和确证方法。     

Determination of Organic Acids in Ground Water by Liquid Chromatography/Atmospheric Pressure Chemical Ionization/Mass Spectrometry

ABSTRACT

Current methods of determining organic acids in ground water are labor-intensive, time-consuming and require a large volume of sample (100 milliliter to 1.0 liter). This paper reports a new method developed to determine aliphatic, alicyclic, and aromatic acids in ground water using liquid chromatography/atmospheric pressure chemical ionization/mass spectrometry (LC/APCI/MS). This method was shown to be fast (less than 1 hour), effective, and reproducible, requiring only 1.0 mL of ground-water sample. Ground water was pH-adjusted, filtered through 0.45 μm filters and directly injected into the LC. A binary solvent system consisting of 40 mM of aqueous ammonium acetate and methanol and a C18 column were used for chromatographical separation. The APCI was operated under negative ionization mode. Selected ion monitoring (SIM) was used for detection and quantitation of the analytes. This method was applied to the analysis of organic acids in ground-water samples collected from an aquifer contaminated with JP-4 fuel hydrocarbons at Wurtsmith Air Force Base in Oscoda, Michigan. Aromatic acids identified in the contaminated ground water include o-, m-toluic acids (2- and 3-methylbenzoic acids), 2,6-dimethylbenzoic acid, 2,3,5- and 2,4,6-trimethylbenzoic acids and two additional trimethylbenzoic acids with unknown location of methylation. The detection of aromatic acids in groundwater from the KC-135 site provided evidence for in situ microbial degradation of hydrocarbons occurring in the aquifer.     

固相萃取-超高效液相色谱-电喷雾串联质谱法同时测定地表水中16种全氟有机化合物

建立了固相萃取-超高效液相色谱-电喷雾串联三重四极杆质谱联用技术分析水中16种全氟有机化合物的高通量检测方法。样品经WAX固相萃取柱富集和净化后,采用Waters ACQUITY UPLC^TM BEH C₁₈色谱柱,含2 mmol/L乙酸铵的甲醇和含2 mmol/L乙酸铵的水作为流动相进行梯度洗脱,质谱采用电喷雾负离子电离,多反应监测模式检测。16种全氟有机化合物在0.5~100 μg/L或1.0~100 μg/L浓度范围内线性关系良好,相关系数为0.9987~0.9999,方法的检出限为0.06~0.46 ng/L;高、中、低3个添加水平的回收率为67.6%~103%,相对标准偏差为2.94%~12.0%。结果表明,该方法灵敏、准确且检测范围广,分析速度快,是一种适于实际水样中全氟有机化合物检测分析的方法。     

Development and validation of a liquid chromatography–tandem mass spectrometry method for simultaneous quantification of p-aminohippuric acid and inulin in rat plasma for renal function study

The first liquid chromatography–tandem mass spectrometry method was developed and validated for the simultaneous quantification of p-aminohippuric acid and inulin, both typical biomarkers of kidney function. 5-(Hydroxymethyl)furfural, generated from inulin by acid and heat preparation, was used as an inulin substitute for the quantification. Acetaminophen was used as the internal standard. Solid-phase extraction was carried out with 5% methanol as the washing solution to optimize the retention of the analytes and to avoid obstruction of the orifice plate of the mass spectrometer caused by any unreacted inulin residue remaining from the sample preparation process. Chromatography separation was performed on a Symmetry C₁₈ column and a mobile phase composed of 2 mM ammonium formate and 0.1% formic acid in water (solvent A) and 2 mM ammonium formate and 0.1% formic acid in acetonitrile (solvent B) (30:70, v/v). Detection was performed with a triple-quadrupole tandem mass spectrometer using positive ion mode electrospray ionization in the multiple reaction monitoring mode. The selected transitions were m/z 195.2 → 120.2, 127.1 → 109.1, and 152.1 → 110.0 for p-aminohippuric acid, inulin [measured as 5-(hydroxymethyl)furfural], and acetaminophen, respectively. The linearity ranged from 10 to 140 μg/mL and from 100 to 1,400 μg/mL for p-aminohippurric acid and inulin (r > 0.99), respectively. The precisions and accuracies were all within 12 and 11% for the lower limit of quantification and quality control samples, respectively. This application was proven to be reliable and accurate and was successfully applied to a renal function study.     

Separation of polar mushroom toxins by mixed-mode hydrophilic and ionic interaction liquid chromatography-electrospray ionization-mass spectrometry

Reversed-phase liquid chromatography (RPLC) is commonly used to analyze nonvolatile contaminants and naturally occurring toxins in foods. However, polar compounds, such as hydrophilic polypeptides and quaternary ammonium salts, are often not satisfactorily separated by RPLC and present a challenge for analytical scientists. In this study, hydrophilic interaction liquid chromatography (HILIC), on an amide-based stationary phase in combination with electrospray ionization (ESI) tandem mass spectrometry (MS-MS), is successfully employed to simultaneously separate polar mushroom toxins, including amanitins and phallotoxins, which are cyclic oligopeptides and muscarine, a quaternary ammonium compound, in mushrooms. The sensitivity of different ionization modes is studied, and the positive ionization mode is found to provide a more sensitive and effective tool for the unambiguous identification of the concerned polar toxins because of their characteristic fragmentation patterns. The properties of the mobile phase are also found to have significant impacts on the separation. At a high acetonitrile (ACN) concentration, hydrophilic interaction dominates, and all analytes under study demonstrate a much higher affinity with the stationary phase. The addition of methanol (MeOH) as a modifier could further enhance the HILIC separation for amanitins, phallotoxins, and muscarine. Valley-to-valley separation is achieved upon the optimatizatiqn of the mobile phase (comprising of ACN, MeOH, and ammonium formate buffer at pH approximately 3.5) and the solvent gradient. HILIC coupled with ESI-MS-MS is demonstrated to be a novel technique for the simultaneous separation and confirmatory analysis of the concerned polar toxins by providing an environment of solubility and retention that could not be achieved through the use of RPLC.     

Screening and confirmation analysis of stimulants, narcotics and beta-adrenergic agents in human urine by hydrophilic interaction liquid chromatography coupled to mass spectrometry

The chromatographic behaviour of 44 polar compounds (23 beta-adrenergic agents, 11 stimulants, 4 narcotics and 6 phenolalkylamines) included in the list of prohibited substances and methods of the World Anti-Doping Agency, has been investigated under hydrophilic interaction liquid chromatography conditions by application of different mobile phase compositions (percentage of the organic solvent, type and amount of mobile phase additive and ionic strength) and column temperatures. Detection of analytes was performed by a triple quadrupole mass spectrometer in positive ionization mode and selected reaction monitoring acquisition mode after liquid/liquid extraction. Data collected using as stationary phase type-B silica materials from different producers, showed that the best chromatographic conditions in terms of peak shape, selectivity and chromatographic retention were obtained using an initial percentage of acetonitrile of 90%, a column temperature of 35 °C, a mobile phase pH of 4.5 and ammonium acetate (5 mM) and acetic acid (0.1%) as mobile phase additives. The selected chromatographic conditions were used to develop screening and confirmation analytical procedures to detect polar compounds in human urine for antidoping purpose. The developed methods were validated in terms of specificity, matrix effect, linearity, precision, accuracy, sensitivity, robustness and repeatability of retention times and relative ion abundances. Such methods offer attractive alternatives and considerable advantages over traditional approaches especially for the analysis of the phenolalkylamines.