Ionization Tandem Mass Spectrometry Detection Research Articles

Evaluation of a Capillary Microsampling Device for Analyzing Plasma Lenvatinib Concentration in Patients With Hepatocellular Carcinoma.

The anticancer drug, Lenvima (lenvatinib), has severe side effects. Therapeutic drug monitoring helps ensure its efficacy and safety. Regular and optimally timed blood sampling is tough, especially when lenvatinib is self-medicated. Microsampling using the easy to handle Microsampling Wing (MSW) may help circumvent this problem. However, current lenvatinib detection methods are not sensitive enough to detect its concentrations in microsamples (<50-250 μL). Thus, the aim of this study was 2-fold (1) develop an analytic method to estimate plasma lenvatinib concentrations in microsamples and (2) verify whether this method works on micro (5.6 μL) blood plasma samples obtained clinically through MSW from patients with unresectable hepatocellular carcinoma (HCC). A simple, highly sensitive, and specific liquid chromatography-electrospray ionization tandem mass spectrometry method was developed. Using this novel protocol, the trough blood plasma concentration of lenvatinib was measured for both blood sampled conventionally and that using MSW. Thirty-five venous whole blood samples were obtained from 11 patients with HCC. Furthermore, the stability of lenvatinib in MSW samples during storage was evaluated. The mean plasma lenvatinib concentration estimates were not significantly different between the MSW and conventional venous blood samples. CV for interday and intraday assays was low. Up to day 5, the lenvatinib concentration in the MSW samples was 85%-115% of the initial day concentration (when stored at 25°C or 4°C). The interference of endogenous matrix components in the human plasma was low. These results indicate that the novel mass spectrometry protocol accurately measures lenvatinib in human plasma and is reproducible. Thus, MSW could be a useful microsampling device for lenvatinib therapeutic drug monitoring in patients with HCC when used in combination with this novel liquid chromatography-electrospray ionization tandem mass spectrometry detection method.

Magnetic Solid-Phase Extraction Based on Magnetite-Multiwalled Carbon Nanotubes of Non-Steroidal Anti-Inflammatories from Water Followed by LC-ESI-MS/MS.

An analytical method based on liquid chromatography-electrospray ionization-tandem mass spectrometry detection (LC-ESI-MS/MS) has been developed for the determination of pharmaceutical compounds in water samples. Five non-steroidal anti-inflammatory drugs (NSAIDs) namely Naproxen, Ketoprofen, Piroxicam, Diflunisal and Celecoxib were investigated. Magnetic solid phase extraction (MSPE) was used for sample pre concentration of water samples and magnetic carbon nanotubes (Fe3O4-MWCNTs) were considered as solid phase extraction sorbent. Important parameters influencing the extraction efficiency such as nature and volume of eluent, sample pH and adsorbent mass were optimized. The developed MSPE method involved 75mg of Fe3O4-MWCNTs sorbent, 5mL of water sample at pH = 4 and 5mL of 10% ammonia in methanol in the elution step. Under the optimized extraction conditions, linearity, detection and quantification limits and reproducibility were evaluated. The proposed method was successfully applied to the analysis of NSAIDs in surface waters, and mean recoveries of all the NSAIDs were above 90% with relative standard deviations < 17%. The detection and quantification limits were comprised between 0.05-3.6ng.mL-1 and 0.2-11.9ng.mL-1, respectively.

Liquid Chromatography-Electron Capture Negative Ionization-Tandem Mass Spectrometry Detection of Pesticides in a Commercial Formulation.

Negative chemical ionization (NCI) and electron-capture negative ionization (ECNI) are gas chromatography–mass spectrometry (GC–MS) techniques that generate negative ions in the gas phase for compounds containing electronegative atoms or functional groups. In ECNI, gas-phase thermal electrons can be transferred to electrophilic substances to produce M–• ions and scarce fragmentation. As a result of the electrophilicity requirements, ECNI is characterized by high-specificity and low background noise, generally lower than EI, offering lower detection limits. The aim of this work is to explore the possibility of extending typical advantages of ECNI to liquid chromatography–mass spectrometry (LC–MS). The LC is combined with the novel liquid-EI (LEI) LC–EIMS interface, the eluent is vaporized and transferred inside a CI source, where it is mixed with methane as a buffer gas. As proof of concept, dicamba and tefluthrin, agrochemicals with herbicidal and insecticidal activity, respectively, were chosen as model compounds and detected together in a commercial formulation. The pesticides have different chemical properties, but both are suitable analytes for ECNI due to the presence of electronegative atoms in the molecules. The influence of the mobile phase and other LC- and MS-operative parameters were methodically evaluated. Part-per-trillion (ppt) detection limits were obtained. Ion abundances were found to be stable with quantitative linear detection, reliable, and reproducible, with no influence from coeluting interfering compounds from the sample matrix.

Application of Dispersive Liquid-Liquid Microextraction Followed by High-Performance Liquid Chromatography/Tandem Mass Spectrometry Analysis to Determine Tetrabromobisphenol A in Complex Matrices.

An accurate and sensitive ultrasound-dispersive liquid-liquid microextraction technique followed by high-performance liquid chromatography separation coupled with electrospray ionization tandem mass spectrometry detection method to determine the presence of tetrabromobisphenol A (TBBPA) in complex environmental matrices is proposed. The miniaturized procedure was used to extract and quantify the analyte in domestic sewage, anaerobic sludge, and the aquatic test organism species Daphnia magna and Chironomus sancticaroli, which are standardized organisms for ecotoxicity bioassays. Limits of detection of 2 ng L-1 (domestic sewage), 2 ng g-1 (anaerobic sludge), 0.25 ng g-1 (D. magna), and 5 ng g-1 (C. tentans) were obtained. The presence of TBBPA was determined in domestic sewage and anaerobic sludge from an anaerobic batch bioreactor at a concentration of 0.2 ± 0.03 μg L-1 and 507 ± 79 ng g-1 , respectively. In D. magna and C. sancticaroli exposed to TBBPA in an acute toxicity bioassay, the micropollutant accumulated at 3.74 and 8.87 μg g-1 , respectively. The proposed method is a simple and cost-effective tool to determine TBBPA environmental occurrence and biomagnification potential compared with conventional extraction methods. To the best of our knowledge, this is the first liquid-liquid miniaturized extraction method to be applied to D. magna and C. sancticaroli. Environ Toxicol Chem 2020;39:2147-2157. © 2020 SETAC.

Dispersive Liquid–Liquid Microextraction of Pesticides Using Ionic Liquids As Extractants

It is found that ionic liquids (ILs) based on imidazole can be used as extractants in the dispersive liquid–liquid microextraction of combined pesticide preparations (imidacloprid, biphenthrin, cypermethrin, malathion, phosalone, and diazinon) followed by their determination by HPLC with electrospray ionization tandem mass spectrometry detection with. The effect of the IL (1-hexyl-3-methylimidazolium tetrafluoborate [C6MIM] [BF4], 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C6MIM] [NTf2], 1‑butyl-3-methylimidazolium hexafluorophosphate, [C4MIM] [PF]6) nature and of the dispersive solvent (acetonitrile, methanol, acetone) volume, extraction time, pH of sample solution, and salting-out agent on the efficiency of analyte extraction is studied. It is found that the maximum recoveries (86–99%) of pesticides were reached using acetonitrile as a dispersive solvent and the [C4MIM] [PF]6 ionic liquid as an extractant. The absence of the effect of pH on the distribution of analytes between the water and organic phases confirms the distributive extraction mechanism. The effect of the ionic liquid on the ionization of pesticides is estimated, and conditions of the back extraction of pesticides to hexane are proposed for its reduction.

Quantification of three chlorinated dialkyl phosphates, diphenyl phosphate, 2,3,4,5-tetrabromobenzoic acid, and four other organophosphates in human urine by solid phase extraction-high performance liquid chromatography-tandem mass spectrometry.

Polybrominated diphenyl ethers (PBDEs), produced as flame retardants worldwide, have been phased-out in many countries, and chlorinated and non-chlorinated organophosphates and non-PBDE brominated formulations (e.g., Firemaster 550 (FM550)) have entered the consumers' market. Recent studies show that components of organophosphate esters and FM550 are frequently detected in many products common to human environments. Therefore, urinary metabolites of these compounds can be used as human exposure biomarkers. We developed a method to quantifynine compounds in 0.4mL urine: diphenyl phosphate (DPhP), bis(1,3-dichloro-2-propyl) phosphate (BDCPP), bis-(1-chloro-2-propyl) phosphate, bis-2-chloroethyl phosphate, di-p-cresylphosphate, di-o-cresylphosphate (DoCP), di-n-butyl phosphate, dibenzylphosphate (DBzP), and 2,3,4,5-tetrabromobenzoic acid. The method relies on an enzymatic hydrolysis of urinary conjugates of the target analytes, automated off-line solid phase extraction, reversed phase high performance liquid chromatography separation, and isotope dilution-electrospray ionization tandem mass spectrometry detection. The method is high-throughput (96 samples/day) with detection limits ranging from 0.05 to 0.16ngmL-1. Spiked recoveries were 90-113%, and interday imprecision was 2-8%. We assessed the suitability of the method by analyzing urine samples collected from a convenience sample of adults (n = 76) and from a group of firefighters (n = 146). DPhP (median, 0.89; range, 0.26-5.6ngmL-1) and BDCPP (median, 0.69; range, 0.31-6.8ngmL-1) were detected in all of the non-occupationally exposed adult samples and all of the firefighter samples (DPhP [median, 2.9; range, 0.24-28ngmL-1], BDCPP [median, 3.4; range, 0.30-44ngmL-1]); DBzP and DoCP were not detected in any samples.

The influence of salt matrices on the reversed-phase liquid chromatography behavior and electrospray ionization tandem mass spectrometry detection of glyphosate, glufosinate, aminomethylphosphonic acid and 2-aminoethylphosphonic acid in water

The analysis of highly polar and amphoteric compounds in seawater is a continuing challenge in analytical chemistry due to the possible formation of complexes with the metal cations present in salt-based matrices. Here we provide information for the development of analytical methods for glyphosate, glufosinate, AMPA, and 2-AEP in salt water, based on studies of the effects of salt matrices on reversed-phase liquid chromatography–heated electrospray ionization-tandem mass spectrometry (RP-LC-HESI–MS/MS) after derivatization of the target compounds with FMOC-Cl. The results showed that glyphosate was the only analyte with a strong tendency to form glyphosate-metal complexes (GMC), which clearly influenced the analysis. The retention times (RTs) of GMC and free glyphosate differed by approximately 7.00min, reflecting their distinct RP-LC behaviors. Divalent cations, but not monovalent (Na+, K+) or trivalent (Al3+, Fe3+) cations, contributed to this effect and their influence was concentration-dependent. In addition, Cu2+, Co2+, Zn2+, and Mn2+ prevented glyphosate detection whereas Ca2+, Mg2+, and Sr2+ altered the retention time. At certain tested concentrations of Ca2+ and Sr2+ glyphosate yielded two peaks, which violated the fundamental rule of LC, that under the same analytical conditions a single substance yields only one LC-peak with a specific RT. Salt-matrix-induced ion suppression was observed for all analytes, especially under high salt concentrations. For glyphosate and AMPA, the use of isotopically labeled internal standards well-corrected the salt-matrix effects, with better results achieved for glufosinate and 2-AEP with the AMPA internal standard than with the glyphosate internal standard. Thus, our study demonstrated that Ca2+, Mg2+, and Sr2+ can be used together with FMOC-Cl to form GMC-FMOC which is suitable for RP-LC-HESI–MS/MS analysis.

An LC/MS quantitative and microdialysis method for cyclovirobuxine D pharmacokinetics in rat plasma and brain: The pharmacokinetic comparison of three different drug delivery routes.

To explore the brain-targeting of cyclovirobuxine D(CVB-D) after administered intranasally, the pharmacokinetics of CVB-D via three different drug delivery routes: intragastric (i.g.), intranasal (i.n.), and intravenous (i.v.) in rat brain and blood was compared. Firstly, an in vivo microdialysis method for sampling CVB-D in both plasma and brain of the rat was established. Secondly, a liquid chromatography-tandem mass spectrometry method has been developed and validated for determination of CVB-D in microdialysis samples. For plasma and brain microdialysis samples, liquid-liquid extraction was used and donepezil was chosen as internal standard. Both were followed by HPLC separation and positive electrospray ionization tandem mass spectrometry detection (ESI-MS/MS). Chromatographic separation was achieved on a agilent C18 column with a mobile phase of methanol-water (50:50, v/v) (pH 3.2) containing 0.1% formic acid and 5mM ammonium acetate. Mass spectrometric detection in the positive ion mode was carried out by selected reaction monitoring (MRM) of the transitions at m/z 403.4→372.3 for CVB-D and m/z 380.2→243.1 for donepezil (IS). Good linearities were obtained in the range of 10-4000ng/mL in rat microdialysates for CVB-D. The lowest limit of quantitation was 5ng/mL, with an extraction recovery >75%, and no significant matrix effects. Intra- and inter-day precisions were all <15% with accuracies of 97.26-116.20%. All of which proved that the established method was successfully applied to the pharmacokinetic study of CVB-D. Simultaneously, brain uptake and pharmacokinetic studies were performed by determination of CVB-D concentration in blood and brain respectively for CVB-D i.g., i.n. and i.v.. Results showed that the intranasal CVB-D could improve brain targeting and had advantages for direct nose to brain transport of CVB-D when compared with injection and oral delivery routes, which indicates that intranasal administration of CVB-D could be a promising approach for the treatment of cerebrovascular disease.

Pressurized hot water extraction followed by miniaturized membrane assisted solvent extraction for the green analysis of alkylphenols in sediments

A novel and Green analytical methodology for the determination of alkylphenols (4-tert-octylphenol, 4-n-octylphenol, 4-n-nonylphenol, nonylphenol) in sediments was developed and validated. The method was based on pressurized hot water extraction (PHWE) followed by miniaturized membrane assisted solvent extraction (MASE) and liquid chromatography–electrospray ionization tandem mass spectrometry detection (LC–ESI-MS/MS). The extraction conditions were optimized by a Plackett–Burman design in order to minimize the number of assays according to Green principles. Matrix effect was studied and compensated using deuterated labeled standards as surrogate standards for the quantitation of the target compounds. The analytical features of the method were satisfactory: relative recoveries varied between 92 and 103% and repeatability and intermediate precision were <9% for all compounds. Quantitation limits of the method (MQL) ranged from 0.061 (4-n-nonylphenol) to 1.7ngg−1 dry weight (nonylphenol). Sensitivity, selectivity, automaticity and fastness are the main advantages of the exposed methodology. Reagent consumption, analysis time and waste generation were minimized. The “greenness” of the proposed method was evaluated using an analytical Eco-Scale approach and satisfactory results were obtained. The applicability of the proposed method was demonstrated analysing sediment samples of Galicia coast (NW of Spain) and the ubiquity of alkylphenols in the environment was demonstrated.

Ultra-Performance Liquid Chromatography with Electrospray Ionization Mass Spectrometry for the Determination of Coenzyme Q10 as an Anti-Aging Ingredient in Edible Cosmetics

A simple and rapid method for the determination of coenzyme Q10 in edible cosmetics was developed and validated. Cleanup utilizing a solid-phase extraction technique provided a simple and reliable method for extracting both coenzyme Q10 and its internal standard coenzyme Q9 from the lecithin-rich samples with efficiencies of 92 ± 4% and 89 ± 3%, respectively. The separation of analytes through a reversed-phase C18 column was carried out within 10 min. By employing authentic coenzyme Q10 and the internal standard spiked into blank matrices, the combined use of solid phase extraction cleanup and chromatographic separation coupled with electrospray ionization-tandem mass spectrometry detection was shown to be sufficiently accurate to detect coenzyme Q10 in edible cosmetic matrices. The limit of quantification of coenzyme Q10 determined by the validated method was 54 ng/g in the matrices. In addition, the intra- and inter-day precision was <4% and the accuracy ranged from 87.1 to 92.3%. Quantitative results for coenzyme Q10 levels in two different edible cosmetic samples obtained by the established analytical protocol were reproducible. This is the first report of the determination of coenzyme Q10 in lipophilic edible cosmetic matrices by liquid chromatography–electrospray ionization tandem mass spectrometry.

Characterisation of honeys according to their content of phenolic compounds using high performance liquid chromatography/tandem mass spectrometry

A simple, fast and specific high performance liquid chromatography separation with an electro-spray ionisation tandem mass spectrometry detection in a negative single reaction ion monitoring scan mode was developed and used for the characterization of Polish honeys according to the content of phenolic acids, including caffeic, chlorogenic, p-coumaric, ferulic, homogentisic, p-hydroxybenzoic and vanillic acids, and flavonoids, i.e., apigenin, genistein, hesperetin, kaempferol, luteolin, rhamnetin, rutin, tricetin and quercetin. Target compounds were isolated and pre-concentrated from the honey matrix by means of the solid phase extraction using Strata X (500mg) cartridges. Analysed honeys did not contain tricetin and genistein. Hesperetin was determined for the first time in heather and linden honeys while rutin in rape honey.

Application of dispersive liquid–liquid microextraction for the determination of phosphatidylethanol in blood by liquid chromatography tandem mass spectrometry

Phosphatidylethanol (PEth) is a phospholipid which requires for its metabolic formation the presence of relatively high ethanol levels. PEth is thus a promising marker to quentify ethanol abuse. Dispersive liquid–liquid microextraction has become a popular technique because it is fast, inexpensive, easy to operate and consumes low volume of organic solvent. In this method, the appropriate mixture of extraction solvent (230μL dichloromethane) and disperser solvent (630μL acetone) are injected into the sample by syringe, rapidly. The liquid chromatography method using a reversed phase-C8 column and a negative ion mode electrospray ionization tandem mass spectrometry detection instrument was developed for the determination of small amounts of PEth that might be present in blood samples, using phosphatidylbutanol (PBut) as an internal standard. The sensitivity of detection obtained with tandem MS was better than that of previous methods. Good linearity was obtained for a range of LOQ-10μg/mL for PEth, whereas all of the deviations in precision and accuracy were less than 15% except for the LLOQ, where it should not exceed 20%. A set of 50 blood samples were analyzed by such method and whole blood concentrations of PEth 16:0/18:1 ranged from LLOQ to 1.71μg/mL.

Simultaneous qualitative and quantitative analysis of triterpenic acids, saponins and flavonoids in the leaves of two Ziziphus species by HPLC–PDA–MS/ELSD

The leaves of Ziziphus jujuba and Z. jujuba var. spinosa have been utilized as crude drugs for their health benefits in China for thousands of years. To control their quality, a reliable method based on high-performance liquid chromatography coupled with photo diode array and electrospray ionization tandem mass spectrometry detection (HPLC–PDA–ESI-MS/MS) was developed for exploration of the chemical profiles of these jujube leaves. As the results, fourteen constituents including three flavonoids, two saponins and nine triterpenic acids were identified or tentatively characterized. Then, twelve of them such as quercetin-3- O-rutinoside, zizyphus saponins I and II, ceanothic acid, alphitolic acid, maslinic acid, 2 α-hydroxyursolic acid, zizyberanalic acid, epiceanothic acid, ceanothenic acid, betulinic acid, and oleanolic acid were selected as the chemical markers and were determined using an HPLC coupled with evaporative light scattering detection (ELSD) method. The separation was carried out on a Waters Sunfire C 18 column with 0.2% acetic acid and acetonitrile as the mobile phase under gradient elution. The operating conditions of ELSD were set as 80 °C for drift tube temperature and 2.7 l/min for nitrogen flow rate. The developed method was fully validated in terms of linearity, sensitivity, precision, repeatability as well as recovery, and subsequently applied to evaluate the quality of eight batches of Z. jujuba and Z. jujuba var. spinosa leaves from different collections.

New Method and Detection of High Concentrations of Monomethylarsonous Acid Detected in Contaminated Groundwater

Monomethylarsonous acid (MMAIII) was detected in groundwater from a former herbicide production plant in the USA. The site has total arsenic concentrations up to thousands of mg/L, representing one of the most severe cases of arsenic contamination ever reported. Structure-specific detection of MMAIII, along with arsenite (AsIII), arsenate (AsV), monomethylarsonic acid (MMAV), and dimethylarsinic acid (DMAV), was achieved using liquid chromatography separation with electrospray ionization tandem mass spectrometry detection (HPLC-ESI-MS/MS). To enable the electrospray of MMAIII and AsIII, dimercaptosuccinic acid (DMSA) was used to derivatize these trivalent arsenicals online, so that their complexes with DMSA could be detected using negative ionization ESI-MS/MS. The presence of MMAIII was verified using high resolution mass spectrometry to measure accurate mass, tandem mass spectrometry to monitor fragmentation, and three different separation techniques to resolve arsenic species. The measured accurate mass of the suspected MMAIII compound in a groundwater sample was 122.9607+/-0.0003 amu, which was in good agreement with the theoretical value and that of the MMAIII standard. Simultaneous monitoring of AsO+ at m/z 91 and SO+ at m/z 48 using HPLC-ICPMS operating in dynamic reaction cell mode ruled out possible confounding from any sulfur-containing arsenic compound. The concentrations of MMAIII found in the groundwater samples from a contaminated site were as high as 3.9-274 mg/L, the highest ever observed in the environment.

Bioanalysis of pentoxifylline and related metabolites in plasma samples through LC‐MS/MS

Analytical aspects related to the assay of pentoxifylline (PTX), lisofylline (M1) and carboxypropyl dimethylxanthine (M5) metabolites are discussed through comparison of two alternative analytical methods based on liquid chromatography separation and atmospheric pressure electrospray ionization tandem mass spectrometry detection. One method is based on a 'pure' reversed-phase liquid chromatography mechanism, while the second one uses the additional polar interactions with embedded amide spacers linking octadecyl moieties to the silicagel surface (C-18 Aqua stationary phase). In both cases, elution is isocratic. Both methods are equally selective and allows separation of unknowns (four species associated to PTX, two species associated to M1) detected through specific mass transitions of the parent compounds and owning respective structural confirmation. Plasma concentration-time patterns of these compounds follow typical metabolic profiles. It has been advanced that in-vivo formation of conjugates of PTX and M1 is possible, such compounds being cleaved back to the parent ones within the ion source. The first method was associated with a sample preparation procedure based on plasma protein precipitation by strong organic acid addition. The second method used protein precipitation by addition of a water miscible organic solvent. Both analytical methods were fully validated and used to assess bioequivalence between a prolonged release generic formulation and the reference product, under multidose and single dose approaches.

Qualitative and quantitative analysis of flavonoids in the leaves of Isatis indigatica Fort. by ultra-performance liquid chromatography with PDA and electrospray ionization tandem mass spectrometry detection

A novel method based on ultra-performance liquid chromatography with photo diode array and electrospray ionization tandem mass spectrometry detection (UPLC-PDA-ESI-MS/MS) was developed for the qualitative and quantitative analysis of flavonoids in the leaves of Isatis indigotica Fort. (Daqingye). The separation was carried out on an Acquity UPLC BEH C 18 column with 0.1% formic acid and methanol as the mobile phase under gradient conditions. Eight flavone C-glucosides were identified and their mass spectrometric fragmentation patterns were studied. Among them, the fragmentation pathways of three flavone 6- C-diglucosides with the rare 1 → 3 interglycosidic linkage were investigated for the first time. In addition, a quantitative analytical method for six flavone C-glucosides in Daqingye by UPLC-ESI-MS/MS was established and applied for the determination of commercial Daqingye samples from different resources.

Determination of Gastrodin and Ligustrazine Hydrochloride in Plasma and Brain Dialysate by LC–Tandem MS

A gradient liquid chromatography-tandem mass spectrometry method has been developed and validated for the determination of gastrodin and ligustrazine hydrochloride in rat plasma and brain dialysates. Zolpidem was used as internal standard. For plasma samples, solid-phase extraction was used and the brain dialysates were collected from freely moving rats using brain microdialysis. Both were followed by HPLC separation and positive electrospray ionization tandem mass spectrometry detection (ESI–MS–MS). Chromatographic separation was achieved on a Symmetry RP-18 column using gradient elution with methanol and water containing 0.5% formic acid and 2 mM ammonium formate. Selected reaction monitoring (SRM) mode was used for quantitation. Good linearities were obtained in the range of 0.05–100 and 0.01–50 μg mL−1 for gastrodin and ligustrazine hydrochloride in rat plasma, and 0.05–1,000 ng mL−1 for both in dialysate. The lower limit of quantitation was 0.01 ng mL−1 for gastrodin and 0.05 ng mL−1 for ligustrazine. The method is precise and reliable and can be applied to pharmacokinetic studies.

Pharmacokinetics and Bioequivalence Study of Two Tablet Formulations of Lovastatin in Healthy Volunteers

Lovastatin is a lipid-lowering agent indicated for primary hypercholesterolemia. This study has assessed single-dosing pharmacokinetics of lovastatin and of its main metabolite, lovastatin beta-hydroxyacid, and has compared the pharmacokinetics of two formulations of lovastatin, a test lovastatin generic (LVSG), and a reference (mevinacor 40 MSD) preparation. The pharmacokinetics and bioequivalence of the two formulations of lovastatin were evaluated by a two-way cross-over randomized double blinded study, in 36 healthy volunteers after a single oral dose of 2 × 40 mg per subject. On plasma samples, collected at given intervals of time (0–24h), lovastatin and its main active metabolite were assayed by high pressure liquid chromatography with positive turbo ion spray ionization tandem mass spectrometry detection. The pharmacokinetic parameters, area under the curve total (AUCt) and to infinity (AUCinf), peak plasma concentration (Cmax), time to attain peak (tmax), and elimination half-life (t1/2) were determined and analyzed statistically. Only minor differences in the pharmacokinetics of lovastatin and lovastatin hydroxyacid between LVSG and mevinacor were found. Analysis of variance (ANOVA) did not show any significant difference between the two formulations, and 90% confidence intervals fell within the acceptable range for bioequivalence. The tolerability profile was good and comparable for the two formulations of lovastatin. Our study, which was performed with the largest number of subjects compared with those published in literature, indicates the bioequivalence of LVSG and mevinacor tablets. The high inter-subject variability of parameters investigated indicate the need of appropriate sample size in pharmacokinetics studies with lovastatin.

Rapid measurement of sphingolipids from Arabidopsis thaliana by reversed‐phase high‐performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry

Changes in sphingolipids have been associated with profound effects in cell fate and development in both plants and animals. Sphingolipids as a group consist of a large number of different compound classes of which numerous individual species may vary in response to environmental stimuli to affect cellular responses. The ability to measure all sphingolipids simultaneously is, therefore, essential to an understanding of the biochemical regulation of sphingolipid metabolism and signaling molecules derived from it. In the model plant Arabidopsis thaliana, the major sphingolipid classes are glycosylinositolphosphoceramides, glucosylceramides, hydroxyceramides and ceramides. Other minor but potentially important sphingolipids are free long-chain bases and their phosphorylated derivates. By using a single solvent system with reversed-phase high-performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry detection we have been able to separate and measure 168 sphingolipids from a crude sample. This greatly speeds up and simplifies the analysis of plant sphingolipids and should pave the way for a better understanding of their role in plant performance.

Validation of a method for the analysis of quinolones residues in bovine muscle by liquid chromatography with electrospray ionisation tandem mass spectrometry detection

A liquid chromatography–tandem mass spectrometry method for the determination and confirmation of nine quinolones was optimised and validated according to Commission Decision 2002/657/EC. Analytes were extracted from veal muscle with water and extracts purified with 96-well plates Oasis HLB cartridges. Separation was carried out in a silica-based C 18 column (50 mm × 2.1 mm) with mobile phases consisting of water/acetonitrile mixtures containing acetic acid. Linear calibration curves in the ranges 4–400 and 50–800 ng g −1, with correlation coefficients at least 0.995, were obtained for all the analytes. At concentration levels above 10 ng g −1, quantification errors were lower than 10% and repeatability and within-laboratory reproducibility standard deviations below 6% and 10%, respectively. Decision limits and detection capabilities are reported.