非水毛细管电泳法测定藤黄中藤黄酸的含量

藤黄酸(gambogic acid, GA)等环氧杂蒽酮类化合物的水溶性差,可通过非水毛细管电泳(non-aqueous capillary electrophoresis, NACE)分析。本文系统地考察了添加20%~60%(v/v)的甲醇或乙腈的运行电解质溶液对藤黄提取液中藤黄酸分离的影响。比较了不同的运行电解质溶液、运行电解质溶液浓度、pH、添加剂 β-环糊精的浓度、分离温度及分离电压的影响,建立了测定藤黄药材中藤黄酸含量的非水毛细管电泳方法。在40%乙腈、10 mmol/L β-环糊精、20 mmol/L四硼酸钠(pH 9.86)为运行电解质溶液、分离电压为10 kV、分离温度为30 ℃、检测波长为280 nm的条件下进行测定。结果表明,藤黄酸在2~2000 mg/L范围内线性关系良好,相关系数为0.9996,检出限(S/N=3)为2 mg/L。将本方法应用于越南、泰国、缅甸、印度4个产地的藤黄药材中藤黄酸的含量测定,测得含量为1.67~472.40 mg/g(相对标准偏差(RSD)为1.12%~2.60%),其中越南产藤黄中藤黄酸含量低,其他产地藤黄中藤黄酸的含量高。实际藤黄样品中藤黄酸的加标回收率为95.2%~105.6%。非水毛细管电泳方法简单、快速、重现性好,可用于藤黄药材中藤黄酸的含量测定。     

Determination of erythromycin A in rat plasma and urine by high-performance liquid chromatography with chemiluminescence detection using Tris(2,2'-bipyridine)ruthenium(II)

A simple and sensitive method was developed for the determination of erythromycin A (EA), decladinosyl erythromycin A (dClEA) and erythromycin B (EB) in rat plasma and urine by high-performance liquid chromatography with electrogenerated chemiluminescence detection using Tris(2,2'-bipyridine)ruthenium(II). The recovery rates of EA, dClEA and EB were 97, 94 and 85% from rat plasma and 89, 83 and 93% from rat urine, respectively. The calibration curves were linear over the concentration ranges 0.05-5 microg/mL for plasma and 0.5-50 microg/mL for urine. The precision and accuracy for all analytes in rat plasma were < or =9.0 and -6.3-7.2%, and those in urine were < or =9.4% and -6.1-7.6%, respectively. This method proved to be a powerful tool for determination of EA, dClEA and EB concentrations in samples from rats.     

Determination of erythromycin and related substances in commercial samples using liquid chromatography/ion trap mass spectrometry

A sensitive, precise and accurate quantitative liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for the measurement of erythromycin A (EA) and related substances in commercial samples was developed and validated. The samples were chromatographed on a reversed-phase column with a polar endcapping and analyzed by ion trap tandem mass spectrometry in the multiple reaction monitoring (MRM) mode using positive electrospray ionization. The method showed high recovery (>or=98.82%), high sensitivity (lower limit of quantitation of 0.25 ng/mL for EA and less than 7.3 ng/mL for the related substances) and high precision (or=0.991) with a run time of only 13 min. The method was successfully applied to the determination of EA and related substances in commercial samples. Moreover, using the advanced data-dependent acquisition capability of the ion trap software two new unexpected EA related substances could be detected and possible structures for these substances were postulated.     

Fullerenes as sorbent materials for benzene, toluene, ethylbenzene, and xylene isomers preconcentration

A simple and novel SPE system for benzene, toluene, ethylbenzene, and xylene isomers (BTEX) compounds in water is proposed in which samples are directly propelled from a 15 mL glass vial through a sorbent column by means of a needle, thereby avoiding evaporative losses and the sorption of BTEX on the manifold materials. Following elution with 150 microL of ethyl acetate, 1 microL of extract is injected into a gas chromatograph-mass spectrometer system. A comparative study of various sorbent materials (C60 fullerene, Tenax TA, and RP-C18) revealed C60 fullerene to be the best choice in terms of sensitivity (a likely result of its increased sample breakthrough volume), precision (the surfactant medium used to prepare samples minimizes evaporative losses), selectivity (C60 fullerene only interacts with nonpolar aromatic compounds), and reusability (columns containing 60 mg of C60 fullerene remain serviceable for at least 6 months). This C60 fullerene-based method exhibits a linear range of 0.1-100 microg/L, a detection limit of 0.04 microg/L, and an RSD of ca. 3%. It was applied to the determination of BTEX in various types of water including sea and waste water with good precision.     

Development and validation of a direct headspace GC-FID method for the determination of sevoflurane, desflurane and other volatile compounds of forensic interest in biological fluids: application on clinical and post-mortem samples

A simple and reliable headspace GC‐flame ionization detection (HS‐GC‐FID) method has been developed and validated for the simultaneous determination of seven volatile compounds of forensic interest: sevoflurane, desflurane, ethanol, methanol, 1‐propanol, acetone and acetaldehyde. All seven compounds including acetonitrile (internal standard) eluted within 10 min and were well resolved with no endogenous interference. Good linearity was observed in the range of 1–12 mg/dL for both anesthetics and 2.5–40 mg/dL for the other five analytes. The method showed good precision, sensitivity and repeatability. Most of the analytes remained stable during the storage of samples at 4°C. Desflurane and acetone degraded (>10%), when the samples remained on the autosampler for more than 2 and 3 h, respectively. The method was finally applied on clinical and post‐mortem blood and urine samples. The clinical samples were collected both from patients who underwent surgery, as well as from the occupationally exposed medical and nursing staff of the university hospital, working in the operating rooms. The hospital staff samples were found negative for all compounds, while the patients' samples were found positive for the anesthetic administered to the patient. The post‐mortem blood samples were found positive for ethanol and acetaldehyde.     

Accurate analysis of trace earthy-musty odorants in water by headspace solid phase microextraction gas chromatography-mass spectrometry

A simple and sensitive method was developed for the simultaneous separation and determination of trace earthy-musty compounds including geosmin, 2-methylisoborneol, 2-isobutyl-3-methoxypyrazine, 2-isopropyl-3-methoxypyrazine, 2,3,4-trichloroanisole, 2,4,6-trichloroanisole, and 2,3,6-trichloroanisole in water samples. This method combined headspace solid-phase microextraction (HS-SPME) with gas chromatography-mass spectrometry and used naphthalene-d(8) as internal standard. A divinylbenzene/carboxen/polydimethylsiloxane fiber exposing at 90°C for 30 min provided effective sample enrichment in HS-SPME. These compounds were separated by a DB-1701MS capillary column and detected in selected ion monitoring mode within 12 min. The method showed a good linearity from 1 to 100 ng L(-1) and detection limits within (0.25-0.61 ng L(-1)) for all compounds. Using naphthalene-d(8) as the internal standard, the intra-day relative standard deviation (RSD) was within (2.6-3.4%), while the inter-day RSD was (3.5-4.9%). Good recoveries were obtained for tap water (80.5-90.6%), river water (81.5-92.4%), and lake water (83.5-95.2%) spiked at 10 ng L(-1). Compared with other methods using HS-SPME for determination of odor compounds in water samples, this present method had more analytes, better precision, and recovery. This method was successfully applied for analysis of earthy-musty odors in water samples from different sources.     

Separation and determination of seven fluoroquinolones by pressurized capillary electrochromatography

In this paper, pressurized CEC was used for the separation and determination of seven fluoroquinolones (FQs). The effect of different experimental conditions, such as the concentration and pH of the buffer, the organic modifier concentration, the surfactant and ion-paring agents added to the electrolyte, and applied voltage were studied. All the seven FQs were baseline separated using mobile phase containing 27% v/v ACN, 5 mmol/L Na2HPO4 buffer (pH 4.0 adjusted using citric acid), 11 mmol/L SDS, and 0.01% TEA v/v at detection wavelength of 287 nm and at an applied voltage of -10 kV. The calibration curves were linear (r>0.9991) over a concentration range of 1.0-50.0 mg/L for norfloxacin (NFLX); 2.5-50.0 mg/L for fleroxacin (FLX), ciprofloxacin (CPFX), and lomefloxacin (LMX); and 5.0-50.0 mg/L for enoxacin (ENX), ofloxacin (OFLX), and gatifloxacin (GFLX). The detection limits (S/N = 3) for ENX, OFLX, FLX, NFLX, CPFX, LMX, and GFLX were 0.5, 0.8, 0.4, 0.2, 0.4, 0.5, and 1.0 mg/L, respectively. The method is simple, rapid, and reproducible. It was successfully applied to the analysis of fish muscle samples spiked with FQs. Mean recoveries ranged from 81.6 to 97.6%.     

Headspace single-drop microextraction of herbal essential oils

A method employing the headspace single-drop microextraction (HS-SDME) is presented for the determination of essential oils in dried herbal leaves. By optimising the key experimental parameters, a linear response for the individual target compounds was obtained in the concentration range from LOQ to 4 mg/mL (r(2) = 0.9912-0.9998), with LODs from 3.3 up to 20.5 microg per 100 g of dried leaves, and the repeatability within the RSD of 2.1-8.9%. The HS-SDME-based procedure, enabling a rapid and simple analysis of essential oils in herbs, was applied to selected real samples (nine essential oils in four different samples) in combination with GC-FID identification and quantification of the target volatiles.     

Residue determination of glyphosate, glufosinate and aminomethylphosphonic acid in water and soil samples by liquid chromatography coupled to electrospray tandem mass spectrometry

This paper describes a method for the sensitive and selective determination of glyphosate, glufosinate and aminomethylphosphonic acid (AMPA) residues in water and soil samples. The method involves a derivatization step with 9-fluorenylmethylchloroformate (FMOC) in borate buffer and detection based on liquid chromatography coupled to electrospray tandem mass spectrometry (LC-ESI-MS/MS). In the case of water samples a volume of 10 mL was derivatized and then 4.3 mL of the derivatized mixture was directly injected in an on-line solid phase extraction (SPE)-LC-MS/MS system using an OASIS HLB cartridge column and a Discovery chromatographic column. Soil samples were firstly extracted with potassium hydroxide. After that, the aqueous extract was 10-fold diluted with water and 2 mL were derivatized. Then, 50 microL of the derivatized 10-fold diluted extract were injected into the LC-MS/MS system without pre-concentration into the SPE cartridge. The method has been validated in both ground and surface water by recovery studies with samples spiked at 50 and 500 ng/L, and also in soil samples, spiked at 0.05 and 0.5 mg/kg. In water samples, the mean recovery values ranged from 89 to 106% for glyphosate (RSD <9%), from 97 to 116% for AMPA (RSD < 10%), and from 72 to 88% in the case of glufosinate (RSD < 12%). Regarding soil samples, the mean recovery values ranged from 90 to 92% for glyphosate (RSD <7%), from 88 to 89% for AMPA (RSD <5%) and from 83 to 86% for glufosinate (RSD <6%). Limits of quantification for all the three compounds were 50 ng/L and 0.05 mg/kg in water and soil, respectively, with limits of detection as low as 5 ng/L, in water, and 5 microg/kg, in soil. The use of labelled glyphosate as internal standard allowed improving the recovery and precision for glyphosate and AMPA, while it was not efficient for glufosinate, that was quantified by external standards calibration. The method developed has been applied to the determination of these compounds in real water and soil samples from different areas. All the detections were confirmed by acquiring two transitions for each compound.     

Characterisation of hydrolysable tannins from leaves of Betula pubescens by high-performance liquid chromatography-mass spectrometry

A high-performance liquid chromatography-electrospray ionisation mass spectrometry (HPLC-ESI-MS) method, assisted by diode array detection, for the characterisation of individual hydrolysable tannins in birch leaves was developed. With the method, it was found that birch (Betula pubescens) leaves contained an exceptionally complex mixture of hydrolysable tannins; 14 gallotannins and 20 ellagitannins were identified. The developed HPLC-ESI-MS method allows the qualitative and quantitative determination of individual gallotannins and ellagitannins directly from crude birch leaf extract. This is important in studying ecological functions of these phenolic compounds, especially their role in the resistance of birch leaves against insects.     

Application of ACC method to synchronous luminiscence: determination of alpha-tocopherol and alpha-tocopheryl acetate in beverages

A new method based on the Q parameter, that permits the determination of the C(compound A)/C(compound B) ratio without preparing calibration graphs of the two compounds, is proposed. This method has been applied to signals obtained by synchronous luminiscence. Simultaneous determination of alpha-tocopherol and alpha-tocopheryl acetate in beverages using synchronous fluorescence has been carried out. To isolate the compounds from samples, liquid extraction with n-hexane as the organic phase was employed. The presence of interferences was tested using the apparent content curves (ACC) method and the C(alpha-tocopherol)/C(alpha-tocopheryl acetate) ratio was calculated using the Q parameter. The reproducibility and detection limit for the determination of alpha-tocopherol and alpha-tocopheryl acetate were 6.6% and 0.016 mg/L and 1.8% and 0.017 mg/L, respectively.     

Spectrophotometric determination of tannins in tea and beer samples with iron(III) and 1,10-phenanthroline as reagents

A simple and accurate spectrophotometric method is proposed for the determination of tannins in tea and beer samples based on the reduction of iron(III) to iron(II) by tannins at 80 degrees C for 20 min. The iron(II) was then reacted with 1,10-phenanthroline at pH 4.4 to form a coloured complex. Background correction could be effected by precipitating the tannins in the sample solution twice with gelatin and kaolin. Absorbance measurements were made at 540 nm and the calibration graph was linear from 0 to 5.5 micrograms ml-1 of tannic acid with a slope of 0.213 A p.p.m.-1. The precision for the determination of tannins in a tea sample containing 9.45% of tannins was 1.8%. Most of the ingredients commonly found in tea and beer samples do not interfere with the determination. Several tea and beer samples were analysed for their tannin content using the proposed method.     

Simultaneous spectrophotometric kinetic determination of four flavor enhancers in foods with the aid of chemometrics

A sensitive kinetic spectrophotometric method was developed for the determination of four flavor enhancers--maltol, ethyl maltol, vanillin, and ethyl vanillin--in food samples. The method was based on the reduction of iron(III) by the four analytes in a sulfuric acid medium (0.012 mol/L), and the subsequent interaction of iron(II) with hexacyanoferrate(III) to form the strongly colored Prussian blue complex, which exhibited an absorption maximum at 800 nm. The optimized method had linear calibrations over the concentration ranges of 0.2-2.8 mg/L for maltol, ethyl maltol, and vanillin, as well as 0.2-1.8 mg/L for ethyl vanillin; the corresponding detection limits were 0.07, 0.07, 0.06, and 0.06 mg/L, respectively. Calibration models were constructed from the original and first-derivative spectral data with the use of partial least-squares (PLS) and principal component regression chemometrics methods. Ultimately, the proposed analytical procedure was successively applied for the determination of the four compounds in commercial food samples with the use of a PLS calibration based on the first-derivative spectral data. The results were comparable with those from a reference HPLC method.     

Analysis of hemoglobin adducts of acrylamide and glycidamide by liquid chromatography-electrospray ionization tandem mass spectrometry, as exposure biomarkers in French population

The determination of biomarkers of acrylamide exposure in humans from general French population by measurement of hemoglobin adduct levels of acrylamide (AA) and glycidamide (GA) is presented. The analytical procedure included modified Edman degradation and LC-ESI-MS/MS analysis of the final derivatives using deuterated internal standards. Method performances were evaluated in terms of linearity, precision, accuracy, and sensitivity. The method was firstly assessed on rat blood samples and then applied to the study of background adducts levels of AA and GA in 68 human hemoglobin samples, showing mean levels of 33 and 23 pmol/g globin for AA and GA adducts, respectively.     

三酰甘油氧化聚合物的制备型快速柱层析-体积排阻色谱测定法

建立了一种简便、灵敏、无需内标的检测油脂中三酰甘油氧化聚合物(TGP)的分析方法。以制备型快速层析柱(PFC)(flash硅胶柱,20 g,40～60μm,6 nm)分离1 g油脂样品中极性组分(PC),经高效体积排阻色谱(HPSEC)(GPC柱,Ф7.8 mm×300 mm,粒径5μm,孔径10 nm)将PC细分为氧化三酰甘油寡聚物(TGO)、氧化三酰甘油二聚物(TGD)、氧化三酰甘油单体(ox-TGM)、二酰甘油(DG)、游离脂肪酸(FFA)。结合重量法测定油脂中PC、面积归一法测定PC中TGP,可准确定量油脂中的TGP含量。结果表明,TGO、TGD分别在28～1 800、11～2 800 mg/L范围内线性关系良好,相关系数(r2)分别为0.998 2、0.998 7,TGO及TGD的检出限(LOD)分别为28、11 mg/L,定量下限(LOQ)分别为113、44 mg/L;相当于油脂中TGP的LOD为0.01%。PFC-HPSEC法检测油脂TGP的相对标准偏差(RSD)均小于10%。PFC对3个PC加标水平(2.27%、8.47%、30.94%)的平均回收率为95%～98%,相对标准偏差(RSD)均低于4%。PFC-HPSEC方法与经典的硅胶柱-HPSEC方法定量油脂TGP的结果吻合度高,相对误差为0～8.9%。该方法能够在2 h内实现各种油脂中TGP含量的定量检测,包括使用过的废弃油脂与未使用的食用油脂,尤其适用于低含量TGP的初榨油和精炼油脂。     

Simplified method for microlitre deuterium measurements in water and urine by gas chromatography-high-temperature conversion-isotope ratio mass spectrometry

Deuterium (2H) in water and urine can be measured by off-line and, more recently, on-line techniques using isotope ratio mass spectrometry (IRMS). We describe a new simple on-line pyrolysis method for the analysis of 2H/1H in water and urine samples by continuous flow IRMS, normally used for 2H/1H measurements in organic compounds. A deactivated column connected the split injector to a high-temperature conversion reactor (TC HD), and 0.5 microL of sample was injected. Accuracy and precision were determined with Vienna Standard Mean Ocean Water (VSMOW), Standard Light Antarctic Precipitation (SLAP), and Greenland Ice Sheet Precipitation (GISP). The range of linearity was measured with a calibration curve of enriched water from 0 up to 0.1 atom percent excess (APE) (i.e. -72 up to 6323 delta per mil (deltaD per thousand)) with a precision of <5 per thousand and accuracy ranging between 1 and 55 per thousand. Blinded reanalysis of urine samples by an equilibration device (Gas Bench) and by a dedicated pyrolysis system (TC/EA) was performed and results compared by the Bland-Altman test. Enrichments ranged between 600 and 2400 per thousand deltaD(VSMOW) with a precision of +/-5 per thousand. Urine enrichments described by our method were strongly correlated with values obtained by Gas Bench and TC/EA (p < 0.0001). There was a significant memory effect that was reduced by injecting the sample 15 times and discarding the first 10 injections, together with accurate furnace conditioning and appropriate cleaning of the syringe. Data indicate that the method is accurate, and that it can be used for water and urine deuterium determination when a Gas Bench or TC/EA instrument is not available and the amount of sample is limited.     

Highly sensitive determination of polybrominated diphenyl ethers in surface water by GC coupled to high‐resolution MS according to the EU Water Directive 2008/105/EC

The analysis of brominated flame retardants, such as polybrominated diphenyl ethers (PBDEs), has received increased interest because of their toxicity and ubiquity. According to European Union Directive 2008/105/EC, the development of highly sensitive and selective methods capable of determining PBDEs at low concentration levels (<0.5 ng/L) is necessary. In this work, an SPE method was developed for the analysis of the six PBDEs (BDE‐28, BDE‐47, BDE‐99, BDE‐100, BDE‐153, BDE‐154) specified by the aforementioned directive in surface waters. The analyses were performed by GC coupled to magnetic sector high‐resolution MS. The conditions were also optimized to detect the target compounds in water samples at concentrations below the environmental quality standards established by European legislation. The validated method provided adequate linearity (determination coefficient, R² ≥ 0.9960), recovery (101–120%, except for BDE‐47 at 5 ng/L, 127%), and precision values (RSD < 20%) at two fortification levels (0.2 and 5 ng/L). The method showed LODs and LOQs ranging from 0.02 to 0.05 and from 0.05 to 0.1 ng/L, respectively. The method was applied in surface water samples, allowing the determination of these compounds at the limits established by current legislation.     

Trace determination of organotin compounds in water,sediment and mussel samples by low-pressure gas chromatography coupled to tandem mass spectrometry

A fast method for the determination of eight organotin compounds (OTs), monobutyltin (MBT), dibutyltin (DBT), tributyltin (TBT), tetrabutyltin (TeBT), monophenyltin (MPhT), diphenyltin (DPhT), triphenyltin (TPhT) and tetraphenyltin (TePhT), in water, sediments and mussels, was developed using low-pressure gas chromatography/tandem mass spectrometry (LPGC/MS/MS). The method is based on sodium diethyldithiocarbamate (DDTC) complexation of the ionic organotins, followed by extraction of the target matrices and derivatization by a Grignard reagent, as described in a previously published method for water samples. Solid-phase extraction was selected as extraction method from water samples after comparison with liquid-liquid extraction, but extraction of the OTs from sediment and mussel samples was performed using toluene. Matrix-matched calibration standards were used to minimize matrix effects. The analytical process was validated by the analysis of spiked blank samples. Performance characteristics such as linearity, detection limit (LOD), quantitation limit (LOQ), precision, and recovery were determined. Recoveries of OTs in spiked matrices ranged from 86-108% in water and from 78-110% in sediments and mussels, with precision values lower than 18%. Detection limits ranged from 0.1-9.6 ng L(-1) in water, and 0.03-6.10 microg kg(-1) in the other matrices. The present implementation of LPGC rather than conventional capillary GC permitted use of large-volume injection and reduced analysis time by a factor of two. The proposed methodology was applied to the determination of OTs in real samples of water, marine sediments and mussels from the west coast of the Mediterranean Sea (Spain).     

Determination of phenolic compounds and hydroxymethylfurfural in meads using high performance liquid chromatography with coulometric-array and UV detection

The objective of this study was the determination of 25 phenolic compounds in different mead samples (honeywines) using high performance liquid chromatography (HPLC) with coulometric-array detection and in case of hydroxymethylfurfural with UV detection. Our method was optimized in respect to both the separation selectivity of individual phenolic compounds and the maximum sensitivity with the electrochemical detection. The method development included the optimization of mobile phase composition, the pH value, conditions of the gradient elution and the flow rate using a window-diagram approach. The developed method was used for the determination of limits of detection and limits of quantitation for individual compounds. The linearity of calibration curves, accuracy and precision (intra- and inter-day) at three concentration levels (low, middle and high concentration range) were verified. Mead samples were diluted with the mobile phase at 1:1 to 1:50 ratio depending on the concentration and filtered through a PTFE filter without any other sample pre-treatment. Phenolic compounds concentration was determined in 50 real samples of meads and correlated with meads composition and hydroxymethylfurfural concentration. The most frequently occurred compounds were protocatechuic acid and vanillic acid (both of them were present in 98% samples), the least occurred compounds were (+)-catechin (10% samples) and sinapic acid (12% samples). Vanillin and ethylvanillin, which are used as artificial additives for the taste improvement, were found in 60% and 42% samples, respectively. Hydroxymethylfurfural concentration, as an indicator of honey quality, was in the range from 2.47 to 158 mg/L. Our method is applicable for the determination of 25 phenolic compounds in mead, honey and related natural samples.     

Optimization of a new resin, Amberlyst 36, as a solid-phase extractor and determination of copper(II) in drinking water and tea samples by flame atomic absorption spectrometry

A new simple and reliable method has been developed to separate and preconcentrate trace copper ion in drinking water and tea samples for subsequent measurement by flame atomic absorption spectrometry (FAAS). The copper ions are adsorbed quantitatively during passage of aqueous solutions through Amberlyst 36 cation exchange resin. After the separation and preconcentration stage, the analyte was eluted with a potassium cyanide solution and determined by FAAS. Different factors including pH of sample solution, sample volume, amount of resin, flow rate of aqueous solution, volume and concentration of eluent, and matrix effects for preconcentration were examined. The analytical figures of merit for the determination of copper are as follows: analytical detection limit (3 sigma), 0.26 microg/L; precision (RSD), 3.1% for 100 microg/L; enrichment factor, 200 (using 1000 mL of sample solution and 5 mL of eluent); time of analysis, 3.5 h (for obtaining enrichment factor of 200); capacity of resin, 125 mg/g. The method was applied for copper determination by FAAS in tap water, commercial natural spring water, commercial treated drinking water, and commercial tea bag sample. The accuracy of the method is confirmed by analyzing tea leaves (GBW 07605). The results demonstrated good agreement with the certified values.