Multiresidue herbicide analysis in soil: subcritical water extraction with an on-line sorbent trap

We evaluated the feasibility of extracting selectively and rapidly herbicide residues in soils by hot water and collecting analytes with a Carbograph 4 solid-phase extraction (SPE) cartridge set on-line with the extraction cell. Phenoxy acid herbicides and those nonacidic and acidic herbicides which are often used in combination with phenoxy acids were selected for this study. Five different soil samples were fortified with target compounds at levels of 100 and 10 ng/g (30 ng/g of clopyralid and picloram) by following a procedure able to mimic weathered soils. Herbicides were extracted with water at 90 °C and collected on-line by the SPE cartridge. After the cartridge was disconnected from the extraction apparatus, analytes were recovered by stepwise elution to separate nonacidic herbicides from acidic ones. The two final extracts were analyzed by liquid chromatography/mass spectrometry with an electrospray ion source. At the lowest spike level considered, analyte recoveries ranged between 81 and 93%, except those for 2,4-DB and MCPB, which were 63%. For 16 herbicides out of 18, the ANOVA test showed recoveries were not dependent on the type of soil. The method detection limit was in the 1.7-10 ng/g range. For the analytes considered, method comparison showed this extraction method was overall more efficient than Soxhlet and sonication extraction techniques.     

Extraction and isolation of triazine herbicides from water and vegetables by a double trap tandem system

The ability of a two-trap tandem system, one containing a nonspecific adsorbing material, such as graphitized carbon black (Carbopack B), and the other one filled with a sulfonic acid type silica-based cation exchanger (SCX), in extracting and isolating basic compounds from real matrices was evaluated by applying this device to the determination of triazine residues in water and vegetables. After percolation through the Carbopack column (extraction cartridge) of water samples or suitably prepared vegetable extracts, the two traps were connected in series, a methylene chloride-methanol mixture was allowed to flow along them, and triazines displaced from the extraction cartridge were selectively reabsorbed via salt formation on the strong acid exchanger column (isolation cartridge). After the column was washed, the analytes were removed from the isolation cartridge by 0.7 mL of aqueous methanol containing 70 mmol/L KCl. After the internal standard was added, the final solution was directly injected into the "high-performance" liquid chromatographic apparatus, which was operated isocratically in the reverse-phase mode with UV detection at 220 nm. The analytical recoveries of eight triazines from the two matrices considered ranged between 95% and 100%. The limits of sensitivity of this method for triazines were set at 10 ng/g of vegetable material and 10 ng/L of water by sampling 100 mL of it.     

Determination of clenbuterol in bovine liver by combining matrix solid-phase dispersion and molecular imprinted solid-phase extraction followed by liquid chromatography/electrospray ion trap multiple-stage mass spectrometry

Matrix solid-phase dispersion (MSPD) is a new sample pretreatment for solid samples. This technique greatly simplifies sample pretreatment but, nonetheless, the extracts often still require an extra cleanup step that is both laborious and time-consuming. The potential of combining MSPD with molecularly imprinted solid-phase extraction (MISPE) was investigated in this study. Liver samples were ground in a mortar with C18 sorbent and the homogenized mixture packed into an SPE cartridge and placed on top of a MISPE cartridge. Subsequently, clenbuterol was eluted from the MSPD cartridge onto the MISPE cartridge using acetonitrile containing 1% acetic acid. The ability of the molecularly imprinted polymer to selectively adsorb analyte in acetonitrile was exploited for re-extracting clenbuterol directly from this acetonitrile extract via the double cartridge tandem system. The analyte was eluted from the MISPE cartridge using acidified methanol. A clear eluate was obtained, which was subsequently evaporated, redissolved, and analyzed by HPLC electrochemical detection (ECD) or ion trap mass spectrometry (LC/IT-MS). The MISPE cartridge used in this study was imprinted using bromoclenbuterol, a structural analogue of clenbuterol, as the template. These MISPE cartridges showed excellent stability. The complete extraction procedure was rapid, and recoveries exceeded 90% for the target analyte. The method detection limit for the LC/IT-MS procedure was < 0.1 microg/kg. This method, therefore, satisfies the stringent requirements of European Union regulation EEC 2377/90.     

Sample preparation based on dynamic ion-exchange solid-phase extraction for GC/MS analysis of acidic herbicides in environmental waters

The newly established enrichment technique, dynamic ion-exchange solid-phase extraction (DIE-SPE), was studied for sample preparation for GC/MS analysis of 16 acidic herbicides in environmental waters. C18 bonded silica was the solid-phase material used. The optimal sample pH was weakly acidic to neutral. However, for common tap water and surface water, which run pH 6-9, all the acidic herbicides except for Chloramben could be effectively extracted from a sample of 1,000-mL volume without pH adjustment. The humic acid could be concurrently extracted from water, but most of it was separated from the sample by using 3 mL of 10% methanol in acetone as the eluent, which would completely elute the analytes and leave a large part of the humic acid on the cartridge. The selective elution reduced the interference of humic acid and made the DIE-SPE an effective approach for the analysis of the acidic herbicides in surface water. Comparing DIE-SPE with conventional reversed-phase SPE (RP-SPE), the former gave higher recoveries for the acidic herbicides and was less affected by sample matrixes. A tandem-cartridge system combining RP- and DIE-SPE in sequence was set up for the simultaneous isolation of the acidic herbicides and removal of the interfering substances. Despite some minimal retention on the upper RP-SPE cartridge, most of the acidic herbicides could be extracted on the lower DIE-SPE cartridge with recovery over 80% except for Chloramben (50%), fenoprop (73%), MCPB (67%), and 2,4-DB (70%) when a 500-mL aqueous sample of pH 9.5 was percolated through the tandem-cartridge system. The effectiveness of the system in removing the long carbon chain fatty acids as well as the basic and neutral organic interfering substances from the sample was also demonstrated.     

基于视觉的某炮弹药筒退弹槽槽底宽度精确测量研究

目的某炮弹药筒退弹槽底宽检测速度和精度要求比较高,传统的手工测量适应不了自动化生产的需要。方法用DH-SV1410型CCD摄像机及可调LED光源构建图像采集系统,并在VS2010平台上用C#语言编写一套基于机器视觉的测量系统。采用亚像素边缘轮廓提取方法精确定位退弹槽的边缘轮廓,并设计一个针对退弹槽底宽检测算法。结果通过对一个零件相同部位进行重复对比实验和多个零件测量对比试验表明,该系统在微米级上有误差,但最大误差最大不超过2μm。结论该系统的检测精度能够达到10μm,完全能满足某炮弹药筒在线测量的速度和精度要求,且测量结果不受主观因素的影响。     

Separation of chiral biodegradation intermediates of linear alkylbenzenesulfonates by capillary electrophoresis

High-performance capillary electrophoresis (HPCE) with α-cyclodextrin as the chiral selector was applied to separate the enantiomers of p-sulfophenyl-2-butyrate (SP2B) and p-sulfophenyl-3-butyrate (SP3B), which occur as biodegradation intermediates of linear alkylbenzenesulfonates (LAS), the widely used anionic surfactants. With this analytical method, we studied the transformation of both SP3B enantiomers in a laboratory batch incubation with activated sewage sludge of a municipal wastewater treatment plant. (S)-(+)-SP3B and (R)-(-)-SP3B could be detected in mechanically treated sewage effluent. After enrichment on graphitized carbon black (Carbopack B), the extracts were analyzed by HPLC with UV diode array and fluorescence detection as well as by HPCE with UV diode array detection. Quantification of SP3B in a 24-h composite sample of primary sewage effluent yielded 34 μg/L (limit of detection, 0.1 μg/L) of the racemic mixture determined by HPLC and 18 μg/L of each enantiomer measured by HPCE (limit of detection, 1 μg/L).     

Multiwalled carbon nanotubes as a solid-phase extraction adsorbent for the determination of bisphenol A, 4-n-nonylphenol,and 4-tert-octylphenol

The adsorptive potential of multiwalled carbon nanotubes (MWNTs) for solid-phase extraction of bisphenol A, 4-n-nonylphenol, and 4-tert-octylphenol was investigated for the first time. The three analytes are quantitatively adsorbed on a MWNTs-packed cartridge, then the analytes retained on the cartridge are quantitatively desorbed with suitable amounts of methanol. Finally, the analytes in the methanol eluate are determined by high performance liquid chromatography-fluorometric detection. Parameters influencing the extraction efficiency, such as volume of the sample solutions, pH of the sample, and the eluent volume, were examined. Comparative studies showed that MWNTs were superior to C18 for the extraction of the more polar analyte bisphenol A and at least as effective as C18 for the extraction of 4-n-nonylphenol and 4-tert-octylphenol. Compared to XAD-2 copolymer, MWNTs exhibited a better property for the extraction of all three analytes. The developed method has been applied to determine bisphenol A, 4-n-nonylphenol, and 4-tert-octylphenol in several environmental water samples. The accuracy of the proposed method was tested by recovery measurements on spiked samples, and good recovery results (89.8-104.2%) were obtained. Detection limits of 0.083, 0.024, and 0.018 ng mL(-1) for bisphenol A, 4-n-nonylphenol, and 4-tert-octylphenol, respectively, were achieved under the optimized conditions.     

Simultaneous quantification of acetanilide herbicides and their oxanilic and sulfonic acid metabolites in natural waters

This paper describes a procedure for simultaneous enrichment, separation, and quantification of acetanilide herbicides and their major ionic oxanilic acid (OXA) and ethanesulfonic acid (ESA) metabolites in groundwater and surface water using Carbopack B as a solid-phase extraction (SPE) material. The analytes adsorbed on Carbopack B were eluted selectively from the solid phase in three fractions containing the parent compounds (PCs), their OXA metabolites, and their ESA metabolites, respectively. The complete separation of the three compound classes allowed the analysis of the neutral PCs (acetochlor, alachlor, and metolachlor) and their methylated OXA metabolites by gas chromatography/mass spectrometry. The ESA compounds were analyzed by high-performance liquid chromatography with UV detection. The use of Carbopack B resulted in good recoveries of the polar metabolites even from large sample volumes (1 L). Absolute recoveries from spiked surface and groundwater samples ranged between 76 and 100% for the PCs, between 41 and 91% for the OXAs, and between 47 and 96% for the ESAs. The maximum standard deviation of the absolute recoveries was 12%. The method detection limits are between 1 and 8 ng/L for the PCs, between 1 and 7 ng/L for the OXAs, and between 10 and 90 ng/L for the ESAs.     

Selective HPLC Analysis of n-Alkyl Hydroperoxides up to C(18)H(38)O(2)

A series of n-alkyl hydroperoxides are separated by HPLC and detected by their postcolumn reaction with horseradish peroxidase and p-hydroxyphenylacetic acid (HPAA) to yield a fluorescent product; several secondary and tertiary hydroperoxides, some 1-hydroxyalkyl hydroperoxides, and a few branched hydroperoxides are also examined. n-Alkyl hydroperoxides up to at least C-18 react with the enzyme with only minimally reduced efficiency at greater alkyl chain length. The effects of the column, the eluent, and the pH of the sample reaching the detector are described. The detection limit with gradient elution ranges from 0.4 μmol L(-)(1) for n-hexyl hydroperoxide to 1 μmol L(-)(1) for n-octadecyl hydroperoxide.     

Identification and quantification of 77 pesticides in groundwater using solid phase coupled to liquid-liquid microextraction and reversed-phase liquid chromatography

This paper describes a method for the extraction, separation, identification, and quantification of 77 pesticides (neutral, acidic, and basic) including some s-triazine metabolites. The method is appropriate for organically (e.g. with humic acids) highly loaded groundwater samples. A comparative study of a pH-controlled mixed solid phase (LiChroprep RP18/LiChrolut EN) extraction with different desorption solvents (acetonitrile or acetonitrile and dichloromethane/methanol) is elaborated. A subsequent liquid-liquid microextraction reduces matrix effects. The pesticides in the sample are separated using RP-HPLC, detected, and identified by diode array. The efficiency is illustrated on a natural groundwater sample from a phreatic aquifer.     

Analytical profiling of biosynthetic intermediates involved in the gentamicin pathway of Micromonospora echinospora by high-performance liquid chromatography using electrospray ionization mass spectrometric detection

In the present study, we developed a sensitive and highly selective method of detecting the biosynthetic intermediates involved in the gentamicin pathway from a cell culture of Micromonospora echinospora. A novel extraction method utilizing a dual solid-phase extraction (SPE) technique was employed to purify and recover all of the gentamicin-related components from the cell culture broth, and high-performance liquid chromatography (HPLC) coupled with electrospray ionization mass spectrometry (ESI-MS/MS) was used to analyze the extractant for gentamicin intermediates. The pH of the culture broth was adjusted to an acidic condition of pH 2 prior to the extraction. The samples were first cleaned with a reversed-phase AccuBOND C(18) cartridge, and then the aminoglycosidic components were purified using a cationic exchanger OASIS MCX cartridge. The detection limit of a gentamicin standard spiked in blank medium processed by this method was found to be approximately 5 ng for each component of the gentamicin C complex, and the mean recovery for each component of standard gentamicin was above 91% when analyzed by HPLC-ESI-MS/MS. We further demonstrated that this method enables the analytical profiling of the gentamicin-related compounds produced by wild-type M. echinospora ATCC 15835, which mainly produces the gentamicin C complex, and the UV-induced mutant strain KCTC 10506BP, which produces gentamicin B as the major product. Seven intermediates (paromamine, gentamicin A2, B, X2, A, JI-20A, and JI-20B) besides the gentamicin C complex were detected in the culture broth of both M. echinospora strains when analyzed by MS/MS for the distinct fragmentation patterns of each gentamicin component. This report displays the first example of the HPLC profiling in a wide range of structurally related biosynthetic intermediates involved in the gentamicin pathway.     

Development and application of porous membrane-protected carbon nanotube micro-solid-phase extraction combined with gas chromatography/mass spectrometry

A novel, multiwalled carbon nanotube (MWCNT)-supported micro-solid-phase extraction (mu-SPE) procedure has been developed. A 6-mg sample of MWCNTs was packed inside a (2 cm x 1.5 cm) sheet of porous polypropylene membrane whose edges were heat-sealed to secure the contents. The mu-SPE device, which was wetted with dichloromethane, was then placed in a stirred sewage sludge sample solution to extract organophosporous pesticides, used here as model compounds. Tumbling of the extraction device within the sample solution facilitated extraction, and the porous membrane acted as a filter to exclude the extraction of extraneous materials. After extraction, analytes were desorbed in hexane and analyzed using gas chromatography/mass spectrometry. Since the porous membrane afforded protection of the MWCNTs, no further cleanup of the extract was required. The pi-pi electrostatic interaction with the analytes and the large surface area of MWCNTs facilitated the adsorption of analytes, with good selectivity and reproducibility. Under the optimized extraction conditions, the method showed good linearity in the range of 0.1-50 mug/L, repeatability of the extractions (RSD 2-8%, n = 4), and low limits of detection (1-7 pg/g). No analyte carryover effect was observed, and each mu-SPE device could be used for up to 30 extractions. Comparison was made with hollow fiber protected solid-phase microextraction and headspace solid-phase microextraction; mu-SPE was demonstrated to be a fast, accurate, and cost-effective pretreatment method for sewage sludge samples.     

镁铝铁层状金属氢氧化物固相萃取有机磷农药的研究

建立镁铝铁层状金属氢氧化物(Mg-Al-Fe-LDH)复合材料固相萃取气相色谱质谱法(GC-MS)测定水中的敌敌畏,乐果,氯吡硫磷,水胺硫磷的分析方法.复合材料用量为2 g,萃取12 min,二氯甲烷作为洗脱剂,洗脱剂用量为2 mL,洗脱时间1 min,4种农药的质量浓度在0.01～10 ng/mL范围内与峰面积线性关...     

Determination of hydroxytyrosol in plasma by HPLC

Hydroxytyrosol (2-(3,4-dihydroxyphenyl)ethanol), a phenolic compound present in extravirgin olive oil, has been reported to contribute to the prevention of cardiovascular disease. The present study describes an accurate and reproducible reversed-phase HPLC method to measure hydroxytyrosol in plasma. This compound was extracted from acidified plasma by solid-phase extraction using an Oasis HLB copolymer. The plasma sample was rinsed with water and methanol in water (5:95; v/v). Hydroxytyrosol was eluted with methanol, which was subsequently evaporated under a nitrogen stream. Analysis by HPLC with diode array-UV detection was carried out using a C18 column and a gradient elution with acidified water and methanol/acetonitrile (50:50; v/v). The method was validated by the analyses of plasma samples spiked with pure hydroxytyrosol, obtaining a linear correlation (0.9986) and precision with a coefficient of variation ranging from 0.79 to 6.66%. The recovery was approximately 100%, and the limit of detection was 37 ng/mL. The oral administration of hydroxytyrosol to rats and its subsequent detection in plasma showed that the method is suitable for pharmacokinetic studies.     

A 384-well solid-phase extraction for LC/MS/MS determination of methotrexate and its 7-hydroxy metabolite in human urine and plasma

A solid-phase extraction procedure, in a 384-well format, has been developed for methotrexate and its primary metabolite, 7-hydroxymethotrexate, in human urine and plasma. This format has not been utilized previously for solid-phase extraction of drugs from biological fluids. The 384-well plates contained a C-18 stationary phase bonded to silica particles which are incorporated into a glass-fiber membrane. Methotrexate and 7-hydroxymethotrexate have been quantified across the curve range of 1 to 50 microg/mL and 50 to 1000 ng/mL, respectively, in urine and from 5 to 250 ng/mL and 5 to 100 ng/mL, respectively, in plasma. Both analytes are quantified by linear regression using 20-microL sample aliquots. Experiments to evaluate the influence of particle size, elution volume, and injection volume on signal intensity were conducted and are reported, along with the results of experiments examining cross contamination between wells. Recovery was determined to be > or = 95% from urine. Results from a run of 384 samples analyzed over a 14-h period indicate that 384-well SPE can be successfully utilized to increase analytical run sizes and sample throughput for LC/MS/MS determination of small drug molecules in biological samples.     

Advantages of molecularly imprinted polymers LC-ESI-MS/MS for the selective extraction and quantification of chloramphenicol in milk-based matrixes. comparison with a classical sample preparation

A simple and fast selective extraction of the antibiotic chloramphenicol (CAP) from milk (raw milk, skimmed milk, and milk powder) using a molecularly imprinted polymer (MIP) sorbent is described. The method entails a single centrifugation step prior to loading the supernatant onto the MIP cartridge and subsequent elution with a mixture of solvents. CAP was further analyzed by isotope dilution liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) operating in negative ionization acquisition mode. The advantages of the MIP approach were assessed by comparing the data generated from a classical solid-phase and liquid-liquid extractions procedure, previously developed in our laboratory. A better recovery of CAP due to an enhanced selectivity and a faster turnaround time (18 samples processed within 3 h compared to 8 h with the classical approach) were evidenced when using the MIP cleanup. The analysis of CAP in raw milk was further validated according to the 2002/657/EC European Union criteria for the analysis of veterinary drug residues at the minimum required performance limit (MRPL) of 0.3 microg/kg, using CAP-d(5) as internal standard. Non-internal-standard corrected recovery values ranged between 50% and 87% over the range of concentrations considered. The decision limit (CCalpha) and detection capability (CCbeta) were calculated to be 0.06 and 0.10 microg/kg, respectively.     

High-throughput identification of in-gel digested proteins by rapid, isocratic HPLC/MS/MS

The high sensitivity and accuracy of mass spectrometry for identifying proteins has led to an explosive expansion of proteomics research, necessitating rapid procedures for HPLC/MS/MS analysis. Current HPLC/MS/MS analysis usually relies on elution of peptides from the HPLC column with a gradient that takes a total of 45-70 min for each cycle, limiting sample throughput and the speed of protein identification. Here we report a simple method for high-throughput protein identification, using isocratic, either methanol- or acetonitrile-based buffer systems, HPLC elution into an LTQ mass spectrometer. This procedure allows each cycle of highly sensitive HPLC/MS/MS analysis to be completed in 5 min, thus boosting the efficiency of HPLC/MS/MS analysis 9-14-fold. Using this method, each operator can acquire HPLC/MS/MS data for 96 in-gel proteolytic digests in one 8-h working day. The method can easily be implemented in any laboratory with an LTQ mass spectrometer. This protocol should find wide application in mass spectrometry laboratories that require high-throughput analysis but are limited by inefficient use of machine time.     

Solid-phase extraction of pesticides from water: possible interferences from dissolved organic material

A multiresidue analysis for trifluralin, simazine, atrazine, propazine, diazinon, parathion-methyl, alachlor, malathion, parathion, chlorpyrifos, pendimethalin, methidathion, and DEF in water that utilizes liquid-solid extraction (LSE) with octadecyl-bonded silica cartridges (C18BSCs) followed by gas chromatography/mass spectrometric analysis was developed. Recoveries of most pesticides were greater than 80% with C18BSCs from fortified water at concentration levels from about 1 to 500 ppb. Recoveries with C18BSCs, from an optically adjusted humic acid solution (10 ppm dissolved organic carbon) made to simulate a natural water with a high dissolved organic content, ranged from 29 to 153% and in general were lower than recoveries obtained from pure water. 14C-Labeled diazinon and parathion were recovered from the humic acid solution at levels of 57 and 68%, respectively, with C18BSCs; the remainder of the labeled pesticides was found in the cartridge eluents. Partition coefficients with human acid were calculated based on recovery of 14C-labeled pesticides from the C18BSCs.     

Screening and selective quantification of illicit drugs in wastewater by mixed-mode solid-phase extraction and quadrupole-time-of-flight liquid chromatography-mass spectrometry

For the first time, a mixed-mode solid-phase extraction with fractionation of basic analytes from neutral and acidic species during cartridge elution and liquid chromatography-quadrupole-time-of-flight mass spectrometry (LC-QTOF-MS) was combined for the quantitative determination of 24 illicit drugs and metabolites in urban sewage samples. The effects of several sample preparation and instrumental parameters in the sensitivity and selectivity of the quantitative method are thoroughly discussed. Under final working conditions, recoveries above 63% and 82% were attained for all species in raw and treated sewage, respectively; whereas, the limits of quantification of the method, defined for a signal-to-noise of 10 (S/N = 10), ranged from 2 to 50 ng L(-1). Sequential elution of mixed-mode cartridges allowed a significant reduction of matrix effects observed during electrospray ionization of basic drugs versus those measured for hydrophilic balance reversed-phase sorbents and the same mixed-mode polymer without fractionated elution. Analysis of raw wastewater samples confirmed the ubiquity of cocaine (COC), benzoylecgonine (BE), and 11-nor-9-carboxy-Δ(9)-tetrahydrocannabinol (THCCOOH) in this matrix. The capability of the above methodology to identify new illicit drugs and/or metabolites in sewage samples is also discussed. With this aim, a two step strategy is proposed. First, high-resolution MS chromatograms, acquired throughout each chromatographic run, are automatically searched against an in-house built database, a reduced list of candidate drugs is generated, and the corresponding extracted ion chromatograms are obtained. In a further LC run, the tandem mass spectrometry (MS/MS) spectra of unknown peaks are acquired using different collision energies and compared with those existing in public libraries, or interpreted, to assign the unknown peak to one of the previously selected candidates.     

Hydrophilic interaction chromatography-based high-throughput sample preparation method for N-glycan analysis from total human plasma glycoproteins

Many diseases are associated with changes in the glycosylation of plasma proteins. To search for glycan biomarkers, large sample sets have to be investigated for which high-throughput sample preparation and analysis methods are required. We here describe a 96 well plate-based high-throughput procedure for the rapid preparation of 2-aminobenzoic acid (2-AA) labeled N-glycans from 10 microL of human plasma. During this procedure, N-glycans are released from glycoproteins and subsequently labeled with 2-AA without prior purification. A hydrophilic interaction chromatography (HILIC)-based solid phase extraction method is then applied to isolate the 2-AA labeled N-glycans, which can be analyzed by MALDI-TOF-MS, HPLC with fluorescence detection, and CE-MS. The relative standard deviation for the intrabatch repeatability and the interbatch repeatability of the sample preparation method remained below 7% and below 9%, respectively, for all peaks observed by HPLC. Similar results were obtained with MALDI-TOF-MS, where 47 N-glycans could be measured consistently. The 2-AA labeled N-glycans were additionally analyzed by a CE-ESI-Q-TOF-MS method, which featured high resolution and mass accuracy, allowing the unambiguous determination of the N-glycan compositions. Up to four times, 96 human plasma samples can be handled in parallel, which, together with the versatility of the 2-AA label, makes this procedure very attractive for glycomics analysis of larger sample cohorts.