High Performance Liquid Chromatography-tandem Research Articles

Fate of 17β-Estradiol in Anaerobic Lagoon Digesters

The fate of [C]17β-estradiol ([C]E2) was monitored for 42 d in triplicate 10-L anaerobic digesters. Total radioactive residues decreased rapidly in the liquid layer of the digesters and reached a steady-state value of 22 to 26% of the initial dose after 5 d. High-performance liquid chromatography and liquid chromatography-tandem mass spectrometry analyses of the liquid layer of the anaerobic digesters indicated a rapid degradation of E2 to estrone (E1), which readily adsorbed to the sludge layer subsequent to its formation. Estrone was the predominant steroid identified under anaerobic digestion in the liquid layer or sorbed to sludge at 42 d. Methane formation represented 11.1 ± 5.7% of the initial E2 fortification with 0.3 to 0.5% of the starting E2 mineralized to carbon dioxide. Maximum [C]methane production appeared between Days 4 and 7. An estimate of estrogenicity of the final product based on reported estrogen equivalents for E1 and E2 was 2% of the original in active digesters. Anaerobic digestion of swine waste has several management benefits; moreover, this study demonstrated that it reduces the potential of environmental release of estrogens, which are known endocrine disruptors.

Determination of simeprevir: A novel, hepatitis C protease inhibitor in human plasma by high-performance liquid chromatography–tandem mass spectrometry

Simeprevir (also known as TMC435 or TMC435350) is a novel hepatitis C protease inhibitor. A validated high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the sensitive and selective quantification of simeprevir in human EDTA plasma is described. During assay development, special attention was given to light instability of the drug in plasma and blood. The method consisted of precipitation of plasma proteins with acetonitrile after which the supernatant was analyzed using electrospray LC-MS/MS. The linearity was confirmed in the concentration range from 2.00 to 2000ng/mL, with 50-fold dilution extending to 100,000ng/mL. The precision of this assay, expressed as CV, ranged between 4.4% and 8.5% over the entire concentration range with assay accuracy between -0.3% and 8.5%. The method was applied successfully in many clinical studies to document the pharmacokinetics of simeprevir in plasma from healthy volunteers and patients.

Simultaneous high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS-MS) analysis of cyanide and thiocyanate from swine plasma

An analytical procedure for the simultaneous determination of cyanide and thiocyanate in swine plasma was developed and validated. Cyanide and thiocyanate were simultaneously analyzed by high-performance liquid chromatography tandem mass spectrometry in negative ionization mode after rapid and simple sample preparation. Isotopically labeled internal standards, Na(13)C(15)N and NaS(13)C(15)N, were mixed with swine plasma (spiked and nonspiked), proteins were precipitated with acetone, the samples were centrifuged, and the supernatant was removed and dried. The dried samples were reconstituted in 10mM ammonium formate. Cyanide was reacted with naphthalene-2,3-dicarboxaldehyde and taurine to form N-substituted 1-cyano[f]benzoisoindole, while thiocyanate was chemically modified with monobromobimane to form an SCN-bimane product. The method produced dynamic ranges of 0.1-50 and 0.2-50μM for cyanide and thiocyanate, respectively, with limits of detection of 10nM for cyanide and 50nM for thiocyanate. For quality control standards, the precision, as measured by percent relative standard deviation, was below 8%, and the accuracy was within ±10% of the nominal concentration. Following validation, the analytical procedure successfully detected cyanide and thiocyanate simultaneously from the plasma of cyanide-exposed swine.

Simultaneous Detection of Six Urinary Pteridines and Creatinine by High-Performance Liquid Chromatography-Tandem Mass Spectrometry for Clinical Breast Cancer Detection

Recent preliminary studies have implicated urinary pteridines as candidate biomarkers in a growing number of malignancies including breast cancer. While the developments of capillary electrophoresis-laser induced fluorescence (CE-LIF), high performance liquid chromatography (HPLC), and liquid chromatography-mass spectroscopy (LC-MS) pteridine urinalyses among others have helped to enable these findings, limitations including poor pteridine specificity, asynchronous or nonexistent renal dilution normalization, and a lack of information regarding adduct formation in mass spectrometry techniques utilizing electrospray ionization (ESI) have prevented application of these techniques to a larger clinical setting. In this study, a simple, rapid, specific, and sensitive high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method has been developed and optimized for simultaneous detection of six pteridines previously implicated in breast cancer and creatinine as a renal dilution factor in urine. In addition, this study reports cationic adduct formation of urinary pteridines under ESI-positive ionization for the first time. This newly developed technique separates and detects the following six urinary pteridines: 6-biopterin, 6-hydroxymethylpterin, d-neopterin, pterin, isoxanthopterin, and xanthopterin, as well as creatinine. The method detection limit for the pteridines is between 0.025 and 0.5 μg/L, and for creatinine, it is 0.15 μg/L. The method was also validated by spiked recoveries (81-105%), reproducibility (RSD: 1-6%), and application to 25 real urine samples from breast cancer positive and negative samples through a double-blind study. The proposed technique was finally compared directly with a previously reported CE-LIF technique, concluding that additional or alternative renal dilution factors are needed for proper investigation of urinary pteridines as breast cancer biomarkers.

Determination of nine benzotriazole UV stabilizers in environmental water samples by automated on-line solid phase extraction coupled with high-performance liquid chromatography–tandem mass spectrometry

A method using automated on-line solid phase extraction coupled with a high-performance liquid chromatography-tandem mass spectrometry system was developed for the determination of emerging benzotriazole UV stabilizers (BZTs) in different environmental water matrices including river water, sewage influent and effluent. Water sample was injected directly and the analytes were preconcentrated on a Polar Advantage II on-line SPE cartridge. After cleanup step the target BZTs were eluted in back flush mode and then separated on a liquid chromatography column. Experimental parameters such as sample loading flow rate, SPE cartridge, pH value and methanol ratio in the sample were optimized in detail. The method detection limits ranged from 0.21 to 2.17 ng/L. Recoveries of the target BZTs at 50 ng/L spiking level ranged from 76% to 114% and the inter-day RSDs ranged from 1% to 15%. The optimized method was successfully applied to analyze twelve water samples collected from different wastewater treatment plants and rivers, and five BZTs (UV-P, UV-329, UV-350, UV-234 and UV-328) were detected with concentrations up to 37.1 ng/L. The proposed method is simple, sensitive and suitable for simultaneous analysis and monitoring of BZTs in water samples.

Ultra high performance liquid chromatography–tandem mass spectrometry method for the determination of soluble milk glycans in rat serum

The main objective of the present work was to develop and validate a multicompound method to measure soluble milk glycans (SMGs) in biological fluids such as serum. An ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method for the identification and quantification of the following SMGs and their precursors 2'-fucosyllactose, 3'-sialyllactose, 6'-sialyllactose, lacto-N-neotetraose, N-acetylneuraminic acid, fucose, lactose and glucose in rat serum samples was set up. These analytes were separated in an Acquity UPLC BEH Amide column using acetonitrile-water gradient with ammonia as additive, in a 10 min run, and were detected and quantified using a triple quadrupole (QqQ) mass spectrometer. The mass spectrometric conditions in negative electrospray ionization mode (ESI-) were individually optimized for each analyte to obtain maximum sensitivity in the Selected Reaction Monitoring (SRM) mode. Selection of two specific fragmentation reactions for each compound allowed simultaneous quantification and identification in one run, ensuring a high specificity of the method. The limits of detection (LODs) ranged from 5 to 70 ng mL(-1) and the limits of quantification (LOQs) from 20 to 200 ng mL(-1). The inter- and intra-day variability was lower than 15% and the recoveries ranged from 85% to 115%. A biological application of the method was also described, specifically the time-course of SMGs in rat serum after an oral challenge.

Pharmacokinetics, Safety, and Tolerability of Maraviroc in HIV-Negative Subjects with Impaired Renal Function

Purpose: This open-label, nonrandomized, parallel-group study was conducted to explore the pharmacokinetics, safety, and tolerability of maraviroc in renally impaired subjects.Methods: Subjects with normal renal function; mild, moderate, or severe renal impairment; or end-stage renal disease (ESRD) (n = 6 per group) were enrolled. Subjects with normal function (period 1), severe impairment, and ESRD received a single 300 mg dose of maraviroc. Subjects with normal function (period 2), mild impairment, and moderate impairment received 150 mg for 7 days at adjusted intervals of twice daily, once daily, and every 48 hours, respectively, with saquinavir/ritonavir (SQV/r). Maraviroc was quantified in plasma, urine, and dialysate by tandem high-performance liquid chromatography–mass spectrometry.Results: With SQV/r, geometric mean steady-state maraviroc area under the plasma concentration-time curve for the dosing interval (AUCtau) was 5,341 (coefficient of variation [CV], 27%), 8,119 (35%), and 6,193 (27%) h•ng/mL, in normal function, mild, and moderate impairment groups, respectively. Without SQV/r, 2% to 3% of the maraviroc dose was recovered in urine versus 15% to 25% of steady-state dose when given with SQV/r. Moderate to high intersubject variability in exposure was noted. AUC from zero to infinity (AUCinf) was similar to historical single-dose data in subjects with ESRD: low in those with normal function, and high in those with severe impairment. Dialysis did not influence maraviroc exposure. Maraviroc was well tolerated.Conclusions: The data suggest that no dosing interval adjustments are required in subjects with renal impairment when maraviroc is administered alone. However, maraviroc dosing intervaladjustment is warranted in renally impaired patients receiving potent CYP3A4 inhibitors. Reference to local prescribing information is recommended, because dose recommendations in renally impaired patients may differ between regions.

Ultra high performance liquid chromatography–tandem mass spectrometry method for cyclosporine a quantification in biological samples and lipid nanosystems

Cyclosporine A (CyA) is an immunosuppressant cyclic undecapeptide used for the prevention of organ transplant rejection and in the treatment of several autoimmune disorders. An ultra high performance liquid chromatography-tandem mass spectrometry method (UHPLC-MS/MS) to quantify CyA in lipid nanosystems and mouse biological matrices (whole blood, kidneys, lungs, spleen, liver, heart, brain, stomach and intestine) was developed and fully validated. Chromatographic separation was performed on an Acquity UPLC(®) BEH C18 column with a gradient elution consisting of methanol and 2mM ammonium acetate aqueous solution containing 0.1% formic acid at a flow rate of 0.6mL/min. Amiodarone was used as internal standard (IS). Retention times of IS and CyA were 0.69min and 1.09min, respectively. Mass spectrometer operated in electrospray ionization positive mode (ESI+) and multiple reaction monitoring (MRM) transitions were detected, m/z 1220.69→1203.7 for CyA and m/z 646→58 for IS. The extraction method from biological samples consisted of a simple protein precipitation with 10% trichloroacetic acid aqueous solution and acetonitrile and 5μL of supernatant were directly injected into the UHPLC-MS/MS system. Linearity was observed between 0.001μg/mL-2.5μg/mL (r≥0.99) in all matrices. The precision expressed in coefficient of variation (CV) was below 11.44% and accuracy in bias ranged from -12.78% to 7.99% including methanol and biological matrices. Recovery in all cases was above 70.54% and some matrix effect was observed. CyA was found to be stable in post-extraction whole blood and liver homogenate samples exposed for 6h at room temperature and 72h at 4°C. The present method was successfully applied for quality control of lipid nanocarriers as well as in vivo studies in BALB/c mice.

Analysis of Phospholipids in Infant Formulas Using High Performance Liquid Chromatography–Tandem Mass Spectrometry

Phospholipids have been used widely in the food industry as emulsifiers, but it is their biological and nutritional function that has been the focus over recent years. The recognition of the importance of phospholipids and sphingomyelin for infant development has led to an increase in the number of infant formulas claiming to contain these complex lipid components. Therefore, the ability to measure these lipids in infant formulas and dairy-derived complex lipid ingredients for fortification purposes is important. A high-performance liquid chromatography-tandem mass spectrometry method that quantifies phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, and sphingomyelin found in infant formulas and dairy-derived complex lipid ingredients is described. The method uses external standards of similar fatty acid profile for calibration. The recovery of phospholipids ranged from 92% to 102% with a method repeatability coefficient of variation of 6-10%. In addition to the specificity and selectivity of the method, details of the molecular species in the individual phospholipid classes are available using this method.

Quantitative determination of fifteen basic pharmaceuticals in ante- and post-mortem whole blood by high pH mobile phase reversed phase ultra high performance liquid chromatography–tandem mass spectrometry

An ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was developed and validated for the determination of fifteen basic pharmaceuticals, for analysis of post- and ante-mortem whole blood samples. The following compounds were included: amitriptyline and its metabolite nortriptyline, trimipramine, mianserin, mirtazapine, citalopram, paroxetine, sertraline, and venlafaxine (all antidepressants), levomepromazine and quetiapine (antipsychotics), ketobemidone and tramadol (analgesics), alimemazine (sedative antihistamine), and metoprolol (beta-blocker). The sample pretreatment consisted of liquid-liquid extraction (LLE) using ethylacetate:n-heptane (80:20, v/v). Six deuterated analogues were used as internal standards (IS). The compounds were separated using a reversed phase C18-column (2.1mm×100mm, 1.7μm), a flow rate of 0.5mL/min, and gradient elution with 5mM ammonium formate pH 10.2 and acetonitrile. Quantification was done by MS/MS using multiple reaction monitoring (MRM) in positive mode, using two transitions for the compounds and one transition for the IS. The run time of the method was 8min including equilibration time. The calibration curves had R(2) values above 0.995 for all the compounds. The intermediate precision had a relative standard deviation (RSD, %) ranging between 2.0 and 16%. Recoveries of the compounds were ≥81%. The lower limits of quantifications (LLOQs) for the compounds varied from 5.0nmol/L to 0.10μmol/L (1.3-26ng/mL) and the limits of detections (LODs) from 1.0 to 20nmol/L (0.24-5.3ng/mL). LLOQ corresponds to 0.28-5.5pg injected on column. Matrix effects (ME) were between 91 and 113% when calculated against an IS. A comparison with former confirmation LC-MS methods at the Norwegian Institute of Public Health, Division of Forensic Medicine and Drug Abuse Research (NIPH) was performed during method validation. Good correlation was seen for all compounds except sertraline, where the old LC-MS method was showing 33% higher results. The method has been running on a routine basis for more than a year, and has proven to be very robust and reliable with results for external quality samples, including sertaline, corresponding well to consensus mean or median.

Determination of pesticide residues in ginseng by dispersive liquid–liquid microextraction and ultra high performance liquid chromatography–tandem mass spectrometry

A procedure involving acetonitrile-based extraction combined with dispersive liquid-liquid microextraction (DLLME) and detection by ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was used for determination of 39 pesticides in ginseng. The extraction of pesticide residues in ginseng was performed with acetonitrile, applying QuEChERS methodology, and the extract was further disposed by DLLME method before analyzed by UHPLC-MS/MS. The average recoveries ranged from 70 to 120% for 82% of the analytes with RSD lower than 15%. The calibration curves obtained with blank matrices were linear with a correlation coefficient of over 0.99. The limits of detection were between 0.01 and 1.0μg/kg. Matrix effects were studied by comparing solvent calibration curves and matrix-matched calibration curves. The results indicate the feasibility of this method for the determination of 39 pesticides in ginseng.

Simultaneous quantitation of azole antifungals, antibiotics, imatinib, and raltegravir in human plasma by two-dimensional high-performance liquid chromatography–tandem mass spectrometry

High-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) is a standard analytical technique for therapeutic drug monitoring (TDM). A rapid LC-MS/MS method was developed for simultaneous quantitation of 3 antifungals and one active metabolite (posaconazole, voriconazole, itraconazole, and hydroxy-itraconazole), 5 antibiotics (daptomycin, ciprofloxacin, oxacillin, levofloxacin, and rifampicin), an antineoplastic agent (imatinib), and an antiretroviral (raltegravir) in human plasma. Protein precipitation of 10 μL of plasma with acetonitrile was used as a single-extraction procedure. After 2-dimensional LC, all drugs were quantified by electrospray ionization-triple quadrupole mass spectrometry by selected reaction monitoring detection in the positive mode. The method was validated per FDA recommendations including the study of extraction recovery (from 79.3% to 105.9%) and matrix effect via ion suppression/enhancement phenomenon. This method is precise (intra- and inter-assay coefficients of variation of 1.95-12.77%, 2.56-8.16% and 2.12-11.38% for low, medium and high levels of internal quality controls respectively) and accurate (intra- and inter-assay biases of 0.19-12.67%, 0.04 to -12.17% and 0.22-12.98% respectively). This method is an efficient tool for routine TDM and optimization of laboratory resource utilization.

Identification of novel penta- and hexamethylated branched glycerol dialkyl glycerol tetraethers in peat using HPLC–MS2, GC–MS and GC–SMB-MS

A Siberian peat contains a high abundance of three unknown isomers of hexamethylated branched (br) GDGTs, of which two are present as a second peak eluting shortly after the known hexamethyl br GDGT containing two 5,13,16-trimethyloctacosanyl moieties. Tandem high performance liquid chromatography–mass spectrometry (HPLC–MS2) did not reveal substantial differences in the MS2 spectrum of the two peaks. HPLC isolation of the two peaks of the hexamethylated br GDGT followed by ether cleavage and GC–MS characterization of the hydrocarbons formed, using supersonic molecular beam (SMB) ionization, revealed the second peak to be composed mainly of a novel hexamethyl br GDGT, possessing two 6,13,16-trimethyloctacosanyl moieties. In addition, both chromatographically separated hexamethylated br GDGTs contained a smaller quantity (20–33%) of a non-symmetrical isomer, with one 13,16-dimethyloctacosanyl and one tetramethyloctacosanyl (either 5,13,16,24- or 6,13,16,23-) moiety. Hexamethylated br GDGTs thus consist of four structural isomers. Furthermore, the pentamethylated br GDGT was also isolated and shown to contain both 5,13,16- and 6,13,16-trimethyloctacosanyl moieties, so is composed of two structural isomers. The assignments reveal why environmental distributions of br GDGTs are sometimes complex, which may have implications for the use of br GDGTs in palaeoclimate reconstruction.

Determination of Seven Free Anabolic Steroid Residues in Eggs by High-Performance Liquid Chromatography–Tandem Mass Spectrometry

A cheap, reliable and practical high-performance liquid chromatography-tandem mass spectrometric method was developed for the simultaneous determination of seven anabolic steroids in eggs, including trenbolone, boldenone, nandrolone, stanozolol, methandienone, testosterone and methyl testosterone. The analytes were extracted from the egg samples using methanol. The extracts were subjected to the removal of fat by freezing-lipid filtration and then further purified by liquid-liquid extraction using tert-butyl methyl ether. The analytes were separated on a Luna C18 column by a gradient elution program with 0.1% formic acid and acetonitrile. This method was validated over 1.00-100 ng/g for all steroids of interest. The correlation coefficients (r) for each calibration curve are higher than 0.99 within the experimental concentration range. The decision limits of the steroids in eggs ranged from 0.20 to 0.44 ng/g, and the detection capabilities were below 1.03 ng/g. The average recoveries were between 66.3 and 82.8% in eggs at three spiked levels of 1.00, 1.50 and 2.00 ng/g for each analyte. The between-day and within-day relative standard deviations were in the range of 2.4-11%. High matrix suppression effects were observed for all compounds of interest.

Simultaneous Determination of Ten Kinds of Perfluorinated Compounds in Lubricant Samples by High-performance Liquid Chromatography-Tandem Mass Spectrometry

An analytical method based on high-performance liquid chromatography tandem mass spectrometry has been developed for the determination of 10 perfluorinated compounds.Various lubricant samples were extracted with the solvent.Then the extract was cleaned up by Oasis WAX and Envi-carb solid phase cartridge.Qualitative and quantitative analyses were carried out for the analyte under the multiple reaction monitoring(MRM) mode after the chromatographic separation over Waters Xbridge C18(150 mm×2.1 mm,3.5 μm)column.The limits of detection for 10 perfluorinated compounds were 0.001~0.005 mg/kg.The mean recoveries at the three spiked levels were 79.05%~106.26%,with the intra-day precision less than 10% and the inter-day precision less than 20%.

Speciation of trace elements in human serum by micro anion exchange chromatography coupled with inductively coupled plasma mass spectrometry

Speciation analysis of essential trace elements in human serum provides important information on nutritional status and homeostatic mechanisms regulating transport processes, acute phase reactions, and protection against oxidative damage. Anion exchange high-performance liquid chromatography (HPLC) combined with inductively coupled plasma mass spectrometry (ICP–MS) has proved to be a useful tool in speciation. Here we describe a fast method that can be applied to carry out the speciation of Fe, Cu, Zn, and Se in as little as 1 ml of serum. The method employs monolithic anion exchange micro columns installed on a tandem HPLC system coupled on-line with an ICP–MS detector. The chromatographic separation is similar to those reported previously but with considerable gain in terms of time and sample requirement. Reproducibility is acceptable for most species. Using our method, we were able to find species-specific differences between different commercially available trace element reference materials. Because the method chosen to collect blood might interfere with speciation, the proposed methodology was used to compare heparinized plasma, ethylenediaminetetraacetic acid (EDTA) plasma, and serum from adult healthy volunteers. As expected, EDTA strongly affects speciation analysis (especially for Fe and Zn), whereas changes due to the use of lithium–heparin (Li–He) as anticoagulant appear to be minimized.

A New High-Performance Liquid Chromatography–Tandem Mass Spectrometry Method Based on Dispersive Solid Phase Extraction for the Determination of the Mycotoxin Fusarin C in Corn Ears and Processed Corn Samples

Fusarin C is a mycotoxin that is produced by a variety of Fusarium species and is therefore a possible contaminant in food and feed. For this reason, a reliable high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method for the determination of fusarin C in food and feed samples was developed based on dispersive solid phase extraction (DSPE). This method has a limit of detection (LOD) of 2 μg/kg, a limit of quantitation (LOQ) of 7 μg/kg, and a recovery rate of 80%. Fifty different corn samples were analyzed, and fusarin C was detected in 40 of them. The fusarin C level varied in kernels of corn ears from not detectable up to 83 mg/kg and in food samples from not detectable up to 28 μg/kg. The co-occurrence of further structural analogues of fusarin C was confirmed by high-performance liquid chromatography Fourier transformation mass spectrometry (HPLC-FTMS). In addition, the stability of fusarin C under storage conditions was evaluated.

Quantitative determination of lisinopril in human plasma by high performance liquid chromatography–tandem mass spectrometry and its application in a pharmacokinetic study

A rapid, selective and sensitive high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was developed to determine lisinopril in human plasma. Sample pretreatment involved a one-step protein precipitation with methanol of 0.1 mL plasma. Analysis was performed on an Inertsil ODS-3 column (2.1 × 50 mm i.d., 3 µm) with mobile phase consisting of methanol-water (containing 0.2% formic acid; 55:45, v/v). The detection was performed on a triple quadrupole tandem mass spectrometer in multiple reaction monitoring mode via an electrospray ionization source. Each plasma sample was chromatographed within 2.5 min. The linear calibration curves for lisinopril were obtained in the concentration range of 1.03-206 ng/mL (r(2) ≥ 0.99) with a lower limit of quantification of 1.03 ng/mL. The intra- and inter-day precisions (relative standard deviation) were not higher than 11%, and accuracy (relative error) was within ±6.8%, determined from quality control samples for lisinopril, which corresponded to the guidance of the Food and Drug Administration. The method described herein was fully validated and successfully applied to the pharmacokinetic study of lisinopril tablets in healthy male volunteers after oral administration.

Simultaneous quantification of flavonoids and phenolic acids in Herba Scutellariae barbatae and its confused plants by high performance liquid chromatography-tandem mass spectrometry

A sensitive and selective high performance liquid chromatography–tandem mass spectrometric method (HPLC–MS/MS) has been developed for simultaneous analysis of 11 components (7 flavonoids and 4 phenolic acids) in Herba Scutellariae barbatae. Simultaneous separation of these 11 compounds was achieved on a C18 analytical column with gradient elution of methanol and 0.1‰ acetic acid (v/v) at a flow rate of 0.8mL/min. The precursor and product ions of analytes were monitored on a hybrid quadrupole linear ion trap mass spectrometer equipped with a turbo ion spray interface in negative mode using multiple-reaction monitoring (MRM). Full validation of the assay was carried out including linearity, precision, accuracy, limits of detection and quantification. The results demonstrated that the method developed was reliable, rapid and specific. Then the method was successfully applied to differentiate 18 batches of Herba Scutellariae barbatae samples and 3 batches of its confused plants from different sources.

Multi-walled carbon nanotubes as solid-phase extraction adsorbent for the ultra-fast determination of chloramphenicol in egg, honey, and milk by fused-core C18-based high-performance liquid chromatography–tandem mass spectrometry

In the present work, a high-performance liquid chromatography-tandem mass spectrometry method has been developed for the residue analysis of chloramphenicol (CAP) in several food matrices. Following the addition of D(5)-CAP as internal standard, egg, honey, and milk were extracted and cleaned by means of solid-phase extraction, utilizing multi-walled carbon nanotubes as sorbent. The extracts were separated on a Halo fused-core C18 column (50 mm × 2.1 mm, 2.7 μm) and quantified by a 4000 Q-trap mass spectrometer equipped with a TurboIonSpray™ interface using electrospray ionization and multiple-reaction monitoring mode. The method validation was performed according to the criteria of Commission Decision 2002/657/EC. The decision limit (CCα) and detection capability (CCβ) of CAP in milk were calculated for m/z 320.8 > 151.9. Due to the existence of slight signal suppression, quantification was performed by matrix-matched calibration curves, ranging from 0.1 to 100 ng mL(-1), with regression coefficients of 0.9993, 0.9998, and 0.9997 for egg, honey, and milk, respectively. Mean recoveries of the CAP ranged from 95.8% to 102.3%, with the corresponding intra- and inter-day variation (relative standard deviation) less than 7.13% and 8.89%, respectively. The limit of detection and limit of quantification of the method were also reported. This method successfully applied to several food matrixes (egg, honey, and milk) and can serve as a monitoring tool to avoid unacceptable levels of residues of CAP entering the food chain.