Monitoring quinolone antibacterial residues in bovine tissues: extraction with hot water and liquid chromatography coupled to a single- or triple-quadrupole mass spectrometer

A rapid and sensitive procedure for determining residues of seven quinolone antibacterials in bovine muscle, kidney and liver is presented. The method is based on the matrix solid-phase dispersion (MSPD) technique with hot water as extractant followed by liquid chromatography/single quadrupole mass spectrometry (LC/MS) or triple-quadrupole mass spectrometry (LC/MS/MS). After dispersing tissue samples on hydrazine sulfate treated sand, target compounds were eluted from the MSPD column by passing through it 4 mL of water heated at 100 degrees C. After pH adjustment and filtration, 200 and 5 microL of the aqueous extracts were respectively injected into the LC/MS and LC/MS/MS instruments. With the former instrument, MS data were acquired in the three-ion selected ion monitoring mode, while MS/MS data acquisition was performed in the multi-reaction monitoring mode by selecting two precursor ion to product ion transitions for each target compound. Hot water appeared to be an efficient extracting medium, since absolute recoveries of the analytes were 84-102%. Using norfloxacin (a quinolone not used in veterinary medicine) as surrogate internal standard, the accuracy of the method at three concentration levels equal to 0.5, 1 and 1.5 times the maximum residue limits (MRLs) set by the european union was 88-109% with relative standard deviations (RSDs) not higher than 7%. The use of LC/MS/MS allowed detection and quantification of the analytes in any tissue considered to be performed at concentrations by far lower than half of their MRLs. Vice versa, the single-quadrupole MS arrangement, while succeeding in monitoring quinolones in muscle tissue at the 0.5 MRL level, showed to be not sufficiently selective for unambiguous identification of some quinolones in kidney and liver.     

Sample preparation for determination of macrocyclic lactone mycotoxins in fish tissue, based on on-line matrix solid-phase dispersion and solid-phase extraction cleanup followed by liquid chromatography/tandem mass spectrometry

A new method based on matrix solid-phase dispersion (MSPD) on-line with a solid-phase extraction (SPE) cleanup process followed by liquid chromatography with tandem mass spectrometry (LC/MS/MS) is presented for the determination of 3 macrocyclic lactone mycotoxins in fish tissues: zearalenone, alpha-zearalenol, and beta-zearalenol. The sample was prepared in a device that used a reversed-phase material (C18) or a normal-phase material (neutral alumina) as a matrix dispersing agent, and a graphitized carbon black cartridge was used for sequential cleanup by SPE. LC/MS/MS was used for selective determination. Isocratic elution with acetonitrile-methanol-water was used for LC separation; for MS/MS, 2 types of interfaces (a pneumatically assisted electrospray ionization interface or an atmospheric pressure chemical ionization interface) were evaluated and compared in terms of the intensity of the total ion current produced by each analyte. The use of highly selective MSPD on-line with SPE for sample preparation before analysis allowed the removal of interfering matrix compounds present in tissue extracts that would otherwise cause severe ionization suppression of zearalenone and its metabolites during the ionization process. Average recoveries at 100 ng/g were between 83 and 103% with C18 and > or = 67% with neutral alumina; the relative standard deviations were < 11% with C18 and < 18% with alumina. The limits of detection ranged from 0.1 to 1.0 ng/g. Sample preparation is simple to perform, no special technical equipment is required, and solvent volumes are minimal.     

A simple and rapid confirmatory assay for analyzing antibiotic residues of the macrolide class and lincomycin in bovine milk and yoghurt: hot water extraction followed by liquid chromatography/tandem mass spectrometry

A rapid and simple sample preparation procedure for determining residues of antibiotics of the class of macrolides and lincomycin in whole milk and yoghurt by liquid chromatography/tandem mass spectrometry (LC/MS/MS) is presented. The method is based on the matrix solid-phase dispersion (MSPD) technique with hot water as extractant. After dispersing samples of milk and yoghurt on sand, target compounds were eluted from the MSPD column by passing through it 5 mL of water acidified with 30 mmol/L formic acid and heated at 70 degrees C. After pH adjustment and filtration, a volume of 200 microL of the aqueous extract was directly injected into the LC column. MS data acquisition was generally performed in the multiple reaction monitoring (MRM) mode, selecting two precursor ion to product ion transitions for each target compound. Hot water appeared to be an efficient extracting medium, since absolute recoveries of the analytes in milk and yoghurt were respectively 68-86% and 82-96%. The method proved to be robust as matrix effects, even though present, did not affect significantly the accuracy of the method, as evidenced by analyzing six different batches of both milk and yoghurt. Using roxithromycin (a macrolide antibiotic not used in veterinary medicine) as surrogate internal standard, the accuracy of the method at three different spike levels of the analytes in milk and yoghurt was 86-107% (RSDs not larger than 10%) and 97-117% (RSDs not larger than 13%), respectively. On the basis of a signal-to-noise ratio of 10, we estimated this method can quantify a few ppb of the analytes in milk and yoghurt. These concentrations are well below the tolerance levels of macrolides and lincomycin in milk set by both the European Union and the US Food and Drug Administration. On analyzing six yoghurt samples, we found evidence for the fact that one of the six samples was contaminated with erythromycin B.     

New micromethod combining miniaturized matrix solid-phase dispersion and in-tube in-valve solid-phase microextraction for estimating polycyclic aromatic hydrocarbons in bivalves

Miniaturized matrix solid-phase dispersion (MSPD) was developed for the extraction of common polycyclic aromatic hydrocarbons (PAHs) from bivalve samples (100mg, dry weight). Additional clean-up and analyte enrichment was accomplished by in-tube solid-phase microextraction (SPME). For this purpose the extracts collected after MSPD were diluted with water and injected into a capillary column coated with the extractive phase. This capillary column was connected to the analytical column by means of a switching valve. Separation and quantification of the PAHs were carried out using a monolithic LC column and fluorescence detection. Since the in-tube SPME device allowed the processing of large volumes of the extracts (2.0 mL) excellent sensitivity was achieved, thus making solvent evaporation operations unnecessary. The overall recoveries ranged from 10% to 28% for the studied compounds. The relative standard deviation (RSD) ranged from 2% to 10% for intra-day variation (n=3), and the limits of detection (LODs) were < or =0.6 ng/g (dry weight). The proposed procedure was very simple and rapid (total analysis time was approximately 20 min), and the consumption of organic solvents and extractive phases was drastically reduced. The reliability of the proposed MSPD/in-tube SPME method was tested by analysing several bivalves (mussels and tellins) as well as a standard reference material (SRM).     

液相色谱–串联质谱法测定水果及其制品中氯吡脲残留量

建立了液相色谱–三重四极杆串联质谱测定水果及其制品中氯吡脲的方法。样品经乙腈提取,氨基固相萃取小柱净化后,用ZORBAX Extend-C18柱(150 mm×2.1 mm,5μm)分离,以甲醇–水为流动相等度洗脱,采用多反应监测正离子模式检测,外标法定量。氯吡脲的质量浓度在4.0~200.0 ng/m L范围内线性良好,相关系数大于0.999,在5.0,10.0,20.0μg/kg 3个添加水平下,氯吡脲的平均加标回收率为86%~92%,测定结果的相对标准偏差为5.3%~7.6%(n=5),方法定量下限为2.0μg/kg。方法灵敏度高,操作简便,定量准确,可满足梨、柑桔、黄桃等水果及其罐头制品中氯吡脲残留的检测与确证需要。     

Determination of residues of azamethiphos in salmon tissue by liquid chromatography with fluorescence detection.

A liquid chromatographic (LC) method with fluorescence detection (FLD) is described for determining residues of the pesticide azamethiphos (AZA) in salmon tissue. The sample is extracted with ethyl acetate, centrifuged, dehydrated with anhydrous sodium sulfate, evaporated, reconstituted in water, and defatted with hexane. The aqueous phase is passed through a C18 solid-phase extraction (SPE) column. The SPE column is eluted with methanol, and the eluate is evaporated to dryness and then taken up in 10% acetonitrile (ACN) in water. The analyte is determined by LC using a C18 column, ACN-H2O (32 + 68) mobile phase, and FLD with excitation at 230 nm and emission at 345 nm. Composited salmon tissues were fortified with AZA at 5, 10, 21, 42, and 83 ng/g or ppb (target level, X = 10 ng/g). Overall recoveries were 86%, with between-day variability of 5.3%. The method detection limit was calculated as 1.2 ppb AZA based on a 5 g sample. The limit of quantitation as determined empirically by this method is the lower limit of the standard curve, approximately 5 ppb.     

Determination of adefovir in human plasma by liquid chromatography/tandem mass spectrometry: application to a pharmacokinetic study

A liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was developed and validated to determine the concentrations of adefovir [9-(2-phosphonylmethoxyethyl)adenine, PMEA] in human plasma. After one-step protein precipitation of plasma samples by methanol, adefovir was analyzed by LC/MS/MS using positive electrospray ionization. Chromatography was performed on a C18 column. The extraction recoveries of adefovir were found to be 85.1-89.3%. Adefovir was stable under routine laboratory conditions. A minimal matrix effect resulting in a slight ionization enhancement of adefovir (<10.9%) was observed, which did not markedly affect the behavior of the calibrations curves and accuracy and precision data. The method had a chromatographic run time of 7.8 min and a linear calibration curve over the concentration range 1.5-90 ng/mL for adefovir. The lower limit of quantification of the method was 1.5 ng/mL. The intra- and inter-day precision was less than 8.4%. These results indicated that this LC/MS/MS method has high selectivity and efficiency, and acceptable accuracy, precision and sensitivity. The validated LC/MS/MS method has been successfully used in a pharmacokinetic study in healthy volunteers treated with oral adefovir dipivoxil at 10 and 20 mg.     

Fast and selective extraction of chloramphenicol from soil by matrix solid‐phase dispersion using molecularly imprinted polymer as dispersant

The molecularly imprinted polymer (MIP) was synthesized and used as dispersant of matrix solid‐phase dispersion (MSPD) for the extraction of chloramphenicol (CAP) in soil samples. The satisfactory recovery of CAP was obtained by the optimized extraction conditions: 1:2 as the ratio of sample to MIPs; 5 min as the dispersion time; 30% aqueous methanol as washing solvent and methanol as elution solvent. The CAP extracted from soil was determined by LC‐MS/MS. The slight ion suppression phenomenon was observed for the CAP when the sample was cleaned up by MSPD with MIP as dispersant, when compared with C18 as MSPD dispersant, which caused significant ion suppression. LOD of CAP is 4.1 ng/g. RSDs of intra‐ and inter‐day tests ranging from 3.1 to 6.2% and from 3.9 to 8.3% are obtained. At all three fortified levels (20, 100 and 500 ng/g), recoveries of CAP are in the range of 86.9–92.6%. The effect of ageing time of spiked soil sample on the CAP recovery was examined. The CAP recovery decreased from 91.0 to 36.9% when the ageing time changed from 1 day to 4 wk.     

Determination of diazepam and its metabolites in human urine by liquid chromatography/tandem mass spectrometry using a hydrophilic polymer column

Diazepam and its major metabolites, nordazepam, temazepam and oxazepam, in human urine samples, were analyzed by liquid chromatography (LC)/tandem mass spectrometry (MS/MS) using a hydrophilic polymer column (MSpak GF-310 4B), which enables direct injection of crude biological samples. Matrix compounds in urine were eluted first from the column, while the target compounds were retained on the polymer stationary phase. The analytes retained on the column were then eluted into an acetonitrile-rich mobile phase using a gradient separation technique. All compounds showed base-peak ions due to [M+H]+ ions on LC/MS with positive ion electrospray ionization, and product ions were produced from each [M+H]+ ion by LC/MS/MS. Quantification was performed by selected reaction monitoring. All compounds spiked into urine showed method recoveries of 50.1-82.0%. The regression equations for all compounds showed excellent linearity in the range of 0.5-500 ng/mL of urine. The limits of detection and quantification for each compound were 0.1 and 0.5 ng/mL of urine, respectively. The intra- and inter-day coefficients of variation for all compounds in urine were not greater than 9.6%. The data obtained from actual determination of diazepam and its three metabolites, oxazepam, nordazepam and temazepam, in human urine after oral administration of diazepam, are also presented.     

Determination of aripiprazole in rat plasma and brain using ultra-performance liquid chromatography/electrospray ionization tandem mass spectrometry

Aripiprazole is an important antipsychotic drug. A simple, sensitive and rapid ultra‐performance liquid chromatography/electrospray ionization tandem mass spectrometry (UPLC‐ESI‐MS/MS) method was developed and validated for the simultaneous quantification of this compound in rat plasma and brain homogenate. The analyte was extracted from rat plasma and brain homogenate using a weak cation exchange mixed‐mode resin‐based solid phase extraction. The compound was separated on an Agilent Eclipse Plus C₁₈ (2.1 × 50 mm, 1.8 µm) column using a mobile phase of (A) 0.1% formic acid aqueous and (B) acetonitrile with gradient elution. The analyte was detected in positive ion mode using multiple reaction monitoring. The method was validated and the specificity, linearity, limit of quantitation (LOQ), precision, accuracy, recoveries and stability were determined. The LOQ was 0.5 ng/mL for aripiprazole in plasma and 1.5 ng/g in brain tissue. The MS response was linear over the concentration range 0.5–100 ng/mL for aripiprazole in plasma and 1.5–300 ng/g in brain tissue. The precision and accuracy for intra‐day and inter‐day were better than 14%. The relative and absolute recoveries were above 72% and the matrix effects were low. This validated method was successfully used to quantify the rat plasma and brain tissue concentrations of the analyte following chronic treatment with aripiprazole. Copyright © 2012 John Wiley & Sons, Ltd.     

Simple assay for monitoring seven quinolone antibacterials in eggs: Extraction with hot water and liquid chromatography coupled to tandem mass spectrometry: Laboratory validation in line with the European Union Commission Decision 657/2002/EC

A simple and rapid method able to determine residues of seven quinolone antibacterials in whole eggs is presented here. This method is based on the matrix solid-phase dispersion technique with hot water as extractant followed by liquid chromatography–tandem mass spectrometry. After depositing 1.5 g of an egg sample containing the analytes and the analyte surrogate (norfloxacin) on sand (crystobalite), this material was packed into an extraction cell. Quinolones were extracted by flowing 6 mL of water acidified with 50 mmol/L formic acid through the cell heated at 100 °C. After pH adjustment and filtration of the extract, 100 μL of it was injected into the LC column. MS data acquisition was performed in the multiple reaction monitoring mode, selecting two precursor ion to product ion transitions for each target compound. Hot water appeared an efficient extracting medium, since absolute recoveries of the analyte in egg at the level of 20 ng/g were 89–103%. Estimated limits of quantification (S/N = 10) were 0.2–0.6 ng/g. Based on the EU Commission Decision 2002/657/EC, the method was validated in terms of ruggedness, specificity, linearity, within-laboratory reproducibility, decision limit (CCα and detection capability (CCβ). Depending on the particular analyte, CCαs ranged between 0.41 and 2.6 ng/g, while CCβs were 0.64–3.7 ng/g. The method was linear in the 3–30 ng/g range, with typical R² values higher than 0.97. The within-laboratory reproducibility (n = 21) at 6 ng/g level was in the 9.0–12% range. After validation, a depletion study of enrofloxacin and one of its metabolites, i.e. ciprofloxacin, in eggs was conducted.     

Liquid chromatography/tandem mass spectrometry determination of (4S,2RS)-2,5,5-trimethylthiazolidine-4-carboxylic acid, a stable adduct formed between D-(-)-penicillamine and acetaldehyde (main biological metabolite of ethanol), in plasma, liver and brain rat tissues

Acetaldehyde, the main biological metabolite of ethanol, is nowadays considered to mediate some ethanol-induced effects. Previous studies on alcohol effect attenuation have shown that D-(-)-penicillamine (3-mercapto-D-valine), a thiol amino acid, acts as an effective agent for the inactivation of acetaldehyde. In the study reported here, laboratory rats were treated with ethanol and D-(-)-penicillamine at different doses looking for the interaction (in vivo) of D-(-)-penicillamine with metabolically formed acetaldehyde following a condensation reaction to form the stable adduct (4S,2RS)-2,5,5-trimethylthiazolidine-4-carboxylic acid (TMTCA). A novel and rapid procedure based on liquid chromatography coupled to tandem mass spectrometry (LC/MS/MS) was developed for quantification and reliable identification of TMTCA in different rat tissues, including plasma, liver and brain. Firstly, plasma was obtained from whole blood. Then, proteins were precipitated from plasma, brain and liver extracts with acetonitrile and the clarified extracts diluted 10-fold. A 20 microL aliquot of the final extracts was then analyzed using an Atlantis C18 5 microm, 100x2 mm column which was connected to the electrospray source of a LC/triple quadrupole mass spectrometer. The analyte was detected in positive ion mode acquiring four MS/MS transitions in selected reaction monitoring (SRM) mode.The method has been validated and it has proved to be fast, reliable and sensitive. The accuracy and precision were evaluated by means of recovery experiments from plasma, liver and brain samples fortified at two concentration levels obtaining satisfactory recoveries in all cases: 95 and 105% in plasma (at 10 and 100 ng/mL, respectively), 79 and 89% in brain (100 and 1000 ng/g), 85 and 99% in liver (100 and 1000 ng/g). Precision, expressed as repeatability, was in all tissues analyzed lower than 17% at the two concentrations tested. The estimated detection limits were 1 ng/mL in plasma, 4 ng/g in brain and 5 ng/g in liver. The limit of quantitation objective (the lowest concentration that was validated with acceptable results) was set up at 10 ng/mL for plasma and 100 ng/g for brain and liver tissue.The reliable identification of the analyte was ensured by the acquisition of four transitions and by their ion abundance ratio measurement. Due to its excellent selectivity and sensitivity, the method developed in this work provides an excellent tool for the specific determination of this cyclic amino acid in biological samples.     

Analysis of β‐blockers in groundwater using large‐volume injection coupled‐column reversed‐phase liquid chromatography with fluorescence detection and liquid chromatography time‐of‐flight mass spectrometry

Atenolol, nadolol, metoprolol, bisoprolol and betaxolol were simultaneously determined in groundwater samples by large‐volume injection coupled‐column reversed‐phase liquid chromatography with fluorescence detection (LVI‐LC‐LC‐FD) and liquid chromatography‐time‐of‐flight mass spectrometry (LC‐TOF‐MS). The LVI‐LC‐LC‐FD method combines analyte isolation, preconcentration and determination into a single step. Significant reductions in costs for sample pre‐treatment (solvent and solid phases for clean up) and method development times are also achieved. Using LC‐TOF‐MS, accurate mass measurements within 3 ppm error were obtained for all of the β‐blockers studied. Empirical formula information can be obtained by this method, allowing the unequivocal identification of the target compounds in the samples. To increase the sensitivity, a solid‐phase extraction step with Oasis MCX cartridge was carried out yielding recoveries of 79–114% (n=5) with RSD 2–7% for the LC‐TOF‐MS method. SPE gives a high purification of β‐blockers compared with the existing methods. A 100% methanol wash was allowed for these compounds with no loss of analytes. Limit of quantification was 1–7 ng/L for LVI‐LC‐LC‐FD and 0.25–5 ng/L for LC‐TOF‐MS. As a result of selective extraction and effective removal of coextractives, no matrix effect was observed in LVI‐LC‐LC‐FD and LC‐TOF‐MS analyses. The methods were applied to detect and quantify β‐blockers in groundwater samples of Almería (Spain).     

Determination of malachite green and leucomalachite green in a variety of aquacultured products by liquid chromatography with tandem mass spectrometry detection

A liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was developed for determining the residues of malachite green (MG) and leucomalachite green (LMG) in a number of aquatic species. MG and its metabolite were extracted from homogenized tissues with a perchloric acid-acetonitrile solution; the extract was centrifuged; and an aliquot was taken, concentrated, and passed through a chemically bonded octadecyl C18 solid-phase extraction column. The compounds of interest were eluted with acetonitrile, and the eluate was evaporated to dryness. The residue was dissolved in acetonitrile and diluted with water in preparation for analysis by LC/MS/MS. MG and its metabolite were determined by reversed-phase LC using a Luna C18 column with an ammonium hydroxide-formic acid buffer in acetonitrile gradient and MS/MS detection using multiple reaction monitoring. Calibration curves were linear for all analyses between 5 and 500 pg injected for both analytes, with recoveries ranging from 81% for LMG to 98% for MG in salmon spiked at the 1 ng/g level. Detection limits of 0.1 ng/g for both MG and LMG were easily obtainable using the recommended method. The operational errors, interferences, and recoveries for spiked samples compared favorably with those obtained by established methodology. The recommended method is simple, rapid, and specific for monitoring residues of MG and LMG in a number of aquatic species.     

Simple confirmatory assay for analyzing residues of aminoglycoside antibiotics in bovine milk: hot water extraction followed by liquid chromatography-tandem mass spectrometry

A simple, selective and sensitive procedure for determining nine widely used aminoglycoside antibiotics (AGs) in bovine whole milk is presented. It is based on matrix solid-phase dispersion with heated water, at 70 degrees C, as extractant followed by liquid chromatography (LC)-tandem mass spectrometry (MS) using an electrospray ion source. After acidification and filtration, 0.2 ml of the aqueous extract was injected into the LC column. MS data acquisition was performed in the multi reaction monitoring mode, selecting two (three, when possible) precursor ion > product ion transitions for each target compound. Analyte recoveries ranged between 70 and 92%. Using aminosidine (an AG not used in veterinary medicine) as surrogate internal standard, the accuracy of the method at three spike levels varied between 80 and 107% with R.S.D. not larger than 11%. The limits of quantification were between 2 ng/ml (apramycin) and 13 ng/ml (streptomycin). They are well below the tolerance levels set by both the European Union and the U.S. Food and Drug Administration.     

Electrospray ionization tandem mass spectrometry for the simultaneous determination of opiates and cocaine in human hair

A fast and highly sensitive electrospray ionization tandem mass spectrometry (ESI-MS/MS) method has been developed for the simultaneous determination of morphine, 6-methylacetylmorphine (6-MAM), codeine, cocaine and benzoylecgonine (BZE) in hair from drug abusers. Pulverized hair samples were subjected to an optimized matrix solid phase dispersion (MSPD) procedure with alumina, followed by diluted hydrochloric acid elution on column solid-phase extraction (SPE) clean-up/pre-concentration. Alternatively, samples were also subjected to an optimized ultrasound assisted enzymatic hydrolysis (USEH) with Pronase E, followed by an off-line SPE clean up/pre-concentration procedure. Positive electrospray ionization and multiple reaction monitoring (MRM) with one precursor ion/product ion transition were used for the identification and quantification (deuterated analogues of each target as internal standards) of each analyte. The chromatographic pump and the autosampler were used for injecting the standards and the hair extracts (20 μL) as a flow injection analysis mode. The highest sensitivity was achieved when delivering the targets with an acetonitrile/water/formic acid (80/19.875/0.125) mixture. The limits of detection of the method were 39.2, 4.4, 6.8, 7.0 and 7.4 ng g(-1) for morphine, 6-MAM, codeine, cocaine and BZE, respectively. Relative standard deviations of intra- and inter-day precision were lower than 9 and 12%, respectively; whereas, analytical recoveries ranged from 96±5 to 106±4%. The developed method (MSPD-ESI-MS/MS) was applied to different hair samples from polydrug abusers, and results were statistically compared to those obtained after a conventional gas chromatography-mass spectrometry (GC-MS) analysis and also after USEH and ESI-MS/MS or GC-MS determinations.     

Simultaneous determination of residues of chloramphenicol,thiamphenicol, florfenicol,and florfenicol amine in farmed aquatic species by liquid chromatography/mass spectrometry

A liquid chromatographic (LC)/mass spectrometric (MS) method was developed for determining the residues of chloramphenicol, thiamphenicol, florfenicol, and florfenicol amine in a number of aquatic species. The phenicols are extracted with acetone, the extracts are partitioned with dichloromethane, the aqueous layer is removed, and the organic layer is evaporated to dryness. The residue is dissolved in dilute acid and defatted with hexane, and the aqueous layer is prepared for analysis by LC. The phenicols are determined by reversed-phase LC by using a Hypersil C18-BD column with a water-acetonitrile gradient and MS detection using selected-ion recording. Calibration curves were linear for all analytes between 0.015 and 0.425 ng injected. The relative standard deviations for measurements by the proposed method were < 10% for all of the analytes studied, with recoveries ranging from 71% for florfenicol amine to 107% for florfenicol in salmon tissue spiked at the 2 ng/g level. Detection limits of 0.1 ng/g for florfenicol and chloramphenicol, 0.3 ng/g for thiamphenicol, and 1.0 ng/g for florfenicol amine are easily obtainable. The operational errors, interferences, and recoveries for spiked samples compare favorably with those obtained by established LC methodology. The proposed method is simple, rapid, and specific for monitoring residues of chloramphenicol, thiamphenicol, florfenicol, and florfenicol amine in a number of aquatic species.     

Simple and sensitive liquid chromatographic quantitative analysis of the novel marine anticancer drug Yondelis (ET-743, trabectedin) in human plasma using column switching and tandem mass spectrometric detection

The development of a simple and sensitive assay for the quantitative analysis of the marine anticancer agent Yondelis (ET-743, trabectedin) in human plasma using liquid chromatography (LC) with column switching and tandem mass spectrometric (MS/MS) detection is described. After protein precipitation with methanol, diluted extracts were injected on to a small LC column (10 x 3.0 mm i.d.) for on-line concentration and further clean-up of the sample. Next, the analyte and deuterated internal standard were back-flushed on to an analytical column for separation and subsequent detection in an API 2000 triple-quadrupole mass spectrometer. The lower limit of quantitation was 0.05 ng mL(-1) using 100 micro l of plasma with a linear dynamic range up to 2.5 ng ml(-1). Validation of the method was performed according to the most recent FDA guidelines for bioanalytical method validation. The time needed for off-line sample preparation has been reduced 10-fold compared with an existing LC/MS/MS method for ET-743 in human plasma, employing a labor-intensive solid-phase extraction procedure for sample pretreatment. The proposed column switching method was successfully applied in phase II clinical trials with Yondelis and pharmacokinetic monitoring.     

基质固相分散液相色谱法检测辣椒产品中的黄曲霉毒素

建立了中性氧化铝-石墨化碳黑的基质固相分散共柱提取净化前处理和以溴为衍生试剂的液相色谱-柱后在线衍生荧光检测法,并将该方法用于辣椒产品中黄曲霉毒素B1,B2,G1,G2的分析。对固相分散剂及共柱净化剂进行了选择和优化。该方法对B1,B2,G1,G2的平均回收率分别为95.4%,87.3%,91.5%和92.6%;方法对B1,G1的检出限为0.25 ng/g,对B2,G2的检出限为0.10 ng/g;对B1,B2,G1,G2进行测定的相对标准偏差(RSD)分别为3.3%,5.8%,4.7%和6.1%。对基质固相分散法和免疫亲和柱法的净化效果进行了比较,结果表明基质固相分散提取净化可以作为一种有效的方法用于辣椒产品中黄曲霉毒素的测定。     

Simultaneous determination of metformin and gliclazide in human plasma by liquid chromatography-tandem mass spectrometry: application to a bioequivalence study of two formulations in healthy volunteers

A rapid and sensitive liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was developed and validated to simultaneously determine gliclazide and metformin in human plasma using huperzine A as the internal standard (IS). After acetonitrile-induced protein precipitation of the plasma samples, gliclazide, metformin and the IS were subjected to LC/MS/MS analysis using electro-spray ionization (ESI). Chromatographic separation was performed on a Hypersil BDS C18 column (50 mm x 2.1 mm, i.d., 3 microm). The method had a chromatographic running time of 2.0 min and linear calibration curves over the concentration ranges of 10-10,000 ng ml(-1) for gliclazide and 7.8-4678.9 ng ml(-1) for metformin. The recoveries of the method were found to be 71-104%. The lower limits of quantification (LOQ) of the method were 10.0 and 7.8 ng ml(-1) for gliclazide and metformin, respectively. The intra- and interday precision was less than 15% for all quality control samples at concentrations of 100, 500, and 2000 ng ml(-1). The validated LC/MS/MS method has been used to study bioequivalence in healthy volunteers. These results indicate that the method was efficient with a very short running time (2.0 min) for metformin and gliclazide compared to the methods reported in the literature. The presented method had acceptable accuracy, precision and sensitivity and was used in clinical bioequivalence study.