Determination of the mycotoxin moniliformin in cultures of Fusarium subglutinans and in naturally contaminated maize by high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry.

A LC-MS method employing triethylamine as ion-pairing reagent for the determination of moniliformin in culture material and naturally contaminated maize samples is described. Mass spectrometric detection of moniliformin was accomplished following atmospheric pressure chemical ionization to yield the deprotonated molecular ion [M-H]- at m/z 97. The moniliformin response was found to be linear over the injected range 10 ng to 700 ng and a detection limit of 10 ng was attainable at a signal-to-noise (S/N) ratio of 4. Five South African strains of Fusarium subglutinans were grown on maize kernels and moniliformin extracted with an acetonitrile-water (95:5) mixture. Following sample clean up with reversed-phase (C18) solid-phase extraction cartridges, the extracts were subjected to LC-MS analysis. Triethylamine was used as an ion-pair reagent and found to improve the retention characteristics of moniliformin without any detrimental effects to the instrument. Moniliformin concentrations ranged between 130 mg/kg and 1460 mg/kg culture. Application of this method to naturally contaminated maize samples from Transkei showed that it was capable of measuring moniliformin levels down to 10 micrograms/kg in selected moldy maize cobs. This is the first report on the application of LC-MS to the analysis of moniliformin in cultures of F. subglutinans and in naturally contaminated maize.     

Determination of amoxicillin in trout by liquid chromatography with UV detection after derivatization

A liquid chromatographic (LC) method based on solid-phase extraction was developed for determination of amoxicillin in muscle tissue of rainbow trout. The compound was extracted in an aqueous solution by precipitation of organic material with a mixture of sulfuric acid and sodium tungstate. The extract was processed by solid-phase extraction on an end-capped phenyl sorbent, and concentrated on a divinylbenzene-co-N-vinylpyrrolidone polymeric sorbent. The extract was derivatized and analyzed by reversed-phase gradient LC on a C18 column with UV detection at 323 nm. The method detection limit was 2.9 micrograms/kg. Mean recovery in muscle was 80.5% (range 10-200 micrograms/kg). The method was applied to fillets from trout offered feed containing amoxicillin in an aquaculture pilot plant. Amoxicillin was detected in muscle tissue shortly after administration but not 3 weeks later. The relative repeatability standard deviation for incurred residues in muscle tissue was 6.4% (range 11-143 micrograms/kg).     

Automated high-performance liquid chromatographic determination of chloramphenicol in milk and swine muscle tissue using on-line immunoaffinity sample clean-up.

An on-line high-performance liquid immunoaffinity chromatographic (HPLIAC) system for the direct determination of chloramphenicol in milk and swine muscle tissue is described. The system consisted of a dual-column system in which an HPLIAC column was directly coupled to an RP-8 high-performance liquid chromatographic column. Skimmed and deproteinated milk or aqueous muscle tissue extract was directly injected into the HPLIAC column. After a washing step with phosphate-buffered saline, chloramphenicol was desorbed by a glycine-NaCl buffer (pH 2.8) and directly concentrated on the RP-8 column. Next, chromatography was carried out using acetonitrile-sodium acetate buffer as the mobile phase. Chloramphenicol was detected at 280 nm. Mean recoveries from spiked raw milk were 70 +/- 2% (1-50 micrograms/kg) and from spiked swine muscle tissue 64 +/- 2% (10-50 micrograms/kg). The calibration curves were linear in the range 1-200 micrograms/kg spiking levels. Limits of determination were 1 microgram/kg for milk and 10 micrograms/kg for muscle tissue.     

Improved gas chromatography with electron-capture detection using a reaction pre-column for the determination of blood cyanide: a higher content in the left ventricle of fire victims

We developed a head-space method for the determination of blood cyanide by gas chromatography with electron-capture detection. In this technique, a reaction pre-column, packed with chloramine-T, was used for the conversion of hydrogen cyanide into cyanogen chloride. Since the reaction pre-column eliminated the necessity for trapping hydrogen cyanide from the biological samples, blood cyanide was quickly analysed by acidification only. The reaction pre-column was durable for at least several months. The calibration curve gave good linearity when dichloromethane was used as the internal standard, and the lower detection limit taken from this plot was ca. 0.05 micrograms/ml. The relative standard deviation of spiked blood samples was in the range 0.6-3.9%. We determined blood cyanide levels at autopsy in victims who had died from fire using this method. A significantly higher cyanide content was detected in the left ventricular blood than in the right. There was a positive correlation between blood cyanide and carboxylhaemoglobin contents. This simple and sensitive technique could be very useful for the determination of cyanide in various samples.     

Determination of non-volatile N-nitrosamines in baby bottle rubber nipples and pacifiers by high-performance liquid chromatography-thermal energy analysis

A method is described for the determination of non-volatile N-nitrosamines in baby bottle rubber nipples and pacifiers. It consists of extraction of the sample with dichloromethane in the presence of ascorbyl palmitate (an inhibitor of artifactual formation of nitrosamines), clean-up on silica or basic alumina, and final analysis by high-performance liquid chromatography-thermal energy analysis, a technique which is highly specific for N-nitroso compounds. The method worked well for the determination of four rubber-related non-volatile nitrosamines, namely, N-nitrosomethylphenylamine, N-nitrosoethylphenylamine, N-nitrosodicyclohexylamine, and N-nitrosodibenzylamine (recoveries from spiked samples greater than 80%; detection limit, ca. 5 micrograms/kg for each). Eighteen out of twenty four samples analyzed were found to contain varying levels (mean, 41 micrograms/kg; range, 8-146 micrograms/kg) of N-nitrosodibenzylamine. The identity of the compound was confirmed by gas chromatography-thermal energy analysis as well as by gas chromatography-mass spectrometry analyses.     

Determination of residues of carazolol and a number of tranquilizers in swine kidney by high-performance liquid chromatography with ultraviolet and fluorescence detection

A rapid and sensitive method has been set up for the determination of the beta-receptor blocker carazolol and the tranquillizers acepromazine, azaperone, chlorpromazine, haloperidol, propionylpromazine and xylazine in swine kidneys. The procedure involves extraction with acetonitrile, rapid sample clean-up with a Sep-Pak C18 cartridge and high-performance liquid chromatography with ultraviolet and fluorescence detection. The mean recoveries range from 93 to 101%, with the exception of xylazine (52%), and the coefficients of variation from 5.3 to 18.9% at a fortification level of 20 micrograms/kg. The limits of determination range from 0.3 micrograms/kg for carazolol to 1-10 micrograms/kg for the other drugs. The method has been tested in routine monitoring programmes.     

Liquid chromatographic determination of flumetsulam in soybeans

A liquid chromatography (LC) method with UV detection is reported for the determination of the sulfonamide herbicide flumetsulam in soybeans. The ground soybean sample was partitioned between methanol and hexane. The hexane removed the lipids, and the methanol layer containing the analyte was further partitioned between dichloromethane and aqueous phosphate buffer at pH 7.0. The aqueous layer, containing the analyte, was acidified to pH 2.2 and partitioned with fresh dichloromethane. The dichloromethane layer containing the analyte was evaporated, and the residue was dissolved in the LC mobile phase for analysis. A polar embedded C18 column was used with a mobile phase of pH 2.2 aqueous phosphate buffer-acetonitrile (68 + 32), run isocratically with detection at 225 nm. The average recovery was 82% with a relative standard deviation (RSD) of 10%. A coefficient of determination of R2 = 0.9992 was achieved for the analyte calibration curve, from 0.005 to 1 microg/mL. The limit of detection, determined from 3 times the standard deviation of 7 replicate extractions of the lowest fortification level (0.01 microg/g), was 0.005 microg/g with an RSD of 22%. LC/electrospray ionization/mass spectrometry in the positive-ion mode was used for identity confirmation of flumetsulam in the fortified soybean extract. The ions at m/z 326, 348, and 129 were observed.     

Determination of nine organophosphorus pesticides in cereals and kidney beans by capillary gas chromatography with flame photometric detection

A method is developed for the determination of nine organophosphorus pesticide residues in cereals and kidney beans by capillary gas chromatography with flame-photometric detection. In this method, dichloromethane is used for clean-up after liquid-liquid extraction. It is shown that good separations are obtained using a fused-silica capillary column (DB-1701) by the optimized temperature program. In the spiked levels of 0.012-0.43 mg/kg, the recoveries are from 83.7% to 107%, with the relative standard deviation between 3.2% and 13% and limits of detection from 8.2 to 15 microg/kg. The method is rapid, sensitive, and practical.     

Plasma determination of the novel anticonvulsant D,L-3-hydroxy-3-ethyl-3-phenylpropionamide and preliminary pharmacokinetic studies in the rat.

A sensitive gas chromatographic method with flame ionization detection was developed for the analysis in plasma of the novel anticonvulsant D,L-3-hydroxy-3-ethyl-3-phenylpropionamide (HEPP), using D,L-2-hydroxy-2-ethyl-2-phenylacetamide as the internal standard. HEPP was extracted from alkalinized plasma into dichloromethane and quantified after derivatization with bis(trimethylsilyl)-trifluoroacetamide: Standard curves were linear from 0.5 to 50 and from 2 to 100 micrograms/ml of plasma, using 1.5 and 5 micrograms of the internal standard, respectively. The lower limit of detection at a signal-to-noise ratio of 3 standard deviations was 0.33 micrograms/ml of sample. The sensitivity, accuracy and reproducibility of the method were shown to be satisfactory for pharmacokinetic studies of HEPP. After intraperitoneal administration of 50 mg/kg to Wistar rats, the principal kinetic parameters were: absorption half-life = 0.04 h; volume of distribution = 1.32 l/kg; clearance = 4.40 ml/min; peak concentration = 50 micrograms/ml; peak time = 0.25 h; mean residence time = 4.55 h.     

超声萃取-气相色谱-质谱联用测定海洋沉积物中39种多溴联苯醚残留

建立了超声萃取-气相色谱-质谱法测定海洋沉积物中39种多溴联苯醚残留的分析方法.样品用V(正己烷):V(二氯甲烷) =1:1混合溶液提取,超声(控制水浴温度为25 ℃)提取60 min,采用硅胶和氧化铝净化,负化学离子源-气相色谱-质谱法进行检测,39种组分图谱在49 min 内能得到很好的分离. 39种混合样品的检出限为0.003～0.10 μg/kg; 加标回收率为66.2%～118.6%;相对标准偏差为0.8%～18.2%.用于实际样品分析,结果令人满意.     

等度反相高效液相色谱法测定熊胆中磷脂类化合物

 摘要：建立了一种分离、测定磷脂酰胆碱（PC）、磷脂酸（PA）、心磷脂（CL）和磷脂酰甘油（PG）的等度RP-HPLC法。色谱条件为：在P-EC18柱上,用V（甲醇）：V（乙腈）：V（水）＝79:8:13的溶液作流动相,以2.0mL/min的流速进行等度洗脱,紫外检测波长205nm,谱带宽5nm。以熊胆为样品,经预处理后用所建立的方法进行分析,结果表明：6个熊胆样品中PC的质量比差别较大;PA的质量比除2号样品较低外,其余相近;PG除2号样品外都能检出,其中6号样品中PG的质量比稍大。PC的平均回收率为89     

离子交换固相萃取-高效液相色谱法研究吡虫啉在梨中的分布及残留动态

建立一种以固相萃取(SPE)、高效液相色谱(HPLC)为基础的测定梨果皮、果肉中吡虫啉残留量的方法。样品用乙腈进行提取,经二氯甲烷液液分配后用阳离子交换固相萃取(SCX-SPE)柱净化,高效液相色谱/二极管阵列检测法(HPLC/DAD)测定。各种添加水平(果皮:0.05、0.1、0.5、2 mg/kg;果肉:0.05、0.5、1mg/kg)的回收率为83%~103%,相对标准偏差(RSD)小于10%,方法的检出限为0.05 mg/kg。运用此方法分别对梨果皮和果肉中吡虫啉的残留动态进行研究,发现吡虫啉主要在梨果皮中残留,得到吡虫啉在果皮中的消解动态方程为:wt=w0×exp(-0.235t),半衰期是2.98 d。     

Screening for coumatetralyl in soft drinks by solid-matrix extraction and high-performance liquid chromatography with diode-array detection.

A method was developed for the rapid determination coumatetralyl in cola- and orange-type soft drinks, which includes extraction using solid-matrix column, clean-up by silica cartridge chromatography and reversed-phase high-performance liquid chromatography with diode-array detection. The recovery of coumatetralyl from 50 ml of soft drinks was better than 80% at spiking levels down to 50 micrograms/kg (ppb).     

反相高效液相色谱法测定血浆中的单硝酸异山梨酯

建立了反相高效液相色谱测定血浆中单硝酸异山梨酯浓度的方法。样品在碱性条件下经二氯甲烷提取后,用C18柱进行分离,以H2O(用0.03 mol/L氨水调pH至7.8)-乙腈(体积比为80∶20)为流动相,对乙酰氨基酚为内标,于230 nm处测定。结果表明,单硝酸异山梨酯的质量浓度为20~1000 μg/L时其峰面积与内标峰面积之比与单硝酸异山梨酯浓度有良好的线性关系。方法的最低检测质量浓度为12 μg/L,平均回收率为(97.11±2.45)％~(104.34±2.17)%,日内测定的相对标准偏差(RSD)≤2.52%,日间测定的RSD≤5.21%。     

Validation of a solid-phase microextraction method for the determination of organophosphorus pesticides in fruits and fruit juice

A method for the determination of organophosphorus pesticides (diazinon, fenitrothion, fenthion, quinalphos, triazophos, phosalon and pyrazophos) in fruit (pears) and fruit juice samples was developed and validated. The samples were diluted with water, extracted by solid-phase microextraction (SPME) and analysed by gas chromatography (GC) using a flame photometric detector in phosphorous mode. Limits of detection of the method for fruit and fruit juice matrices were below 2 micrograms/kg for all pesticides. Relative standard deviations for triplicate analyses of samples fortified at 25 micrograms/kg of each pesticide were not higher than 8.7%. Recovery tests were performed for concentrations between 25 and 250 micrograms/kg. Mean recoveries for each pesticide were all above 75.9% and below 102.6% for juice, and between 70 and 99% for fruit except for pyrazophos in the fruit sample (with mean recovery of 53%). Therefore, the proposed method is applicable in the analysis of pesticides in fruit matrices and the use of the method in routine analysis of pesticide residues is discussed.     

同位素内标-液相色谱-串联质谱法测定动物源性食品中氯霉素残留

加入氯霉素同位素内标的动物源性样品(龙虾、肠衣)经乙酸乙酯提取浓缩、正己烷去脂后,采用液-液萃取,水相经0.45μm滤膜过滤后,用液相色谱-串联质谱定量.在0.1、0.2,0.3μg/kg3个浓度水平上进行添加回收试验.回收率为71.8%～90.0%,检出限为0.05μg/kg.该法简化了前处理操作步骤,缩短了检测时间...     

Thin-layer chromatographic separation and in situ fluorimetric determination of ofloxacin in plasma and pleural fluid

A thin-layer chromatographic assay for the determination of ofloxacin in human plasma and pleural fluid is described. After extraction of ofloxacin from samples with dichloromethane, chromatography was performed on thin-layer plates (silica gel) with a mobile phase consisting of ethanol and water; the tank atmosphere was equilibrated with concentrated ammonia. The precision of the assay could be considerably increased along with the measured fluorescence intensity of ofloxacin by spraying the plate with a citric acid solution and dipping it into paraffin or using a mixture of both components. Peaks were quantified by densitometric evaluation of the chromatograms. The method shows a very low limit of detection (1 ng/ml) as well as good precision and linearity in the range 0.001-2.0 micrograms/ml for both plasma and pleural fluid.     

An ion-pairing liquid chromatography/tandem mass spectrometric method for the determination of ethephon residues in vegetables

A rapid, sensitive and selective method has been developed for the direct determination of ethephon residues in vegetables (apple, cherry and tomato). Given the anionic character of ethephon, the use of ion-pairing liquid chromatography (LC) in combination with tandem mass spectrometry (MS/MS, triple quadrupole) allowed its direct determination in these matrices avoiding a derivatisation step and favouring the automation of the method. Samples were extracted with a mixture of dichloromethane/aqueous formic acid (pH 3) (1:1). Then, tetrabutylammonium acetate (TBA) was added as an ion-pairing reagent, and an aliquot of the aqueous extract was directly injected into the LC/MS/MS system. Quantification was performed with matrix-matched standards prepared from blank sample extracts. MS/MS measurements were made in the selected reaction monitoring (SRM) mode, using the most sensitive transition (m/z 107 > 79) for quantification, and up to four additional transitions for confirmation. Quantitative recoveries were obtained for all matrices (between 83% and 96%) at two concentration levels tested (0.05 and 0.5 mg/kg), with relative standard deviations lower than 9% in all cases. The addition of TBA directly into the sample extract contained in the injection vial was found sufficient to obtain satisfactory LC retention for the analyte. Under these conditions, the absence of ion-pairing reagent in the mobile phase minimised the ionisation suppression for ethephon in the MS source, leading to an increase in the sensitivity of the method and reaching limits of detection of 0.02 mg/kg for all matrices investigated. The acquisition of five specific MS/MS transitions for ethephon allowed the simultaneous and reliable quantification and confirmation of the analyte in the samples.     

Rapid sample preparation method for the determination of chloramphenicol in swine muscle by high-performance liquid chromatography

A simple and rapid sample preparation method for the determination of chloramphenicol in swine muscle tissue at the 10 micrograms/kg level is described. The method comprises sonication-aided extraction with ethyl acetate, addition of hexane to the extract and cleaning up and concentration of the extract on a small column packed with silica gel. Analysis was performed by high-performance liquid chromatography on a ChromSep column with ChromSpher C8 using acetonitrile-sodium acetate buffer as the mobile phase. Detection was performed at 280 nm. Mean recoveries from spiked muscle samples were 79 +/- 3% (10-50 micrograms/kg). The distribution of chloramphenicol in different muscle and fatty tissues from a pig to which a single dose of chloramphenicol was administered was also investigated.     

Determination of the residues of eleven organophosphorus insecticides in Job's-tears by gas chromatography with a nitrogen-phosphorus detector

A simplified method for determining 11 organophosphorus insecticides (dichlorvos, methamidophos, acephate, diazinon, dimethoate, chlorpyrifos, malathion, parathion, quinalphos, methidathion, and ethion) in the Chinese herbal medicine Job's-tears is described. Standards were fortified into Job's-tears (5 g) at 4 levels. The organophosphorus insecticides were extracted with dichloromethane and cleaned up with a mixture of Celite 545-activated carbon (4 + 1). The extracts were analyzed by gas chromatography using a nitrogen-phosphorus detector. Analysis of fortified Job's-tears shows average recoveries ranged from 73.90-98.70%, 86.31-93.15%, 84.92-96.22%, and 83.29-104.23% at 0.05, 0.1, 0.5, and 1.0 mg/kg levels, respectively. The minimum detectable amount ranged from 1.0 x 10(-10) to 5.0 x 10(-10) g, and the limit of quantitation for the method was 0.05 mg/kg. The method is rapid, simple, sensitive, reproducible, and applicable to the determination of these 11 organophosphorus insecticides in Job's-tears.