The journal of microcolumn separations : JMS最新文献

{"title":"Comprehensive two-dimensional gas chromatography (GC×GC) of atropisomeric PCBs, combining a narrow bore β-cyclodextrin column and a liquid crystal column","authors":"Mikael Harju,&nbsp;Peter Haglund","doi":"10.1002/mcs.10010","DOIUrl":"10.1002/mcs.10010","url":null,"abstract":"<p>Peak assignment and quantification of PCBs in environmental samples is a time-consuming and costly process, and the analysis of atropisomeric PCBs is even more laborious and costly due to the elaborate analytical work involved. GC×GC can solve some of the problems entailed by increasing congener resolution and instrument sensitivity. In this study, a comprehensive two-dimensional gas chromatography (GC×GC) system was utilized with a combination of a permethylated β-cyclodextrin column in the first dimension and a liquid crystal column in the second dimension. Using this system, in a single GC×GC run six out of nine studied atropisomeric PCBs (PCBs 91, 132, 135, 136, 149, and 176) can be resolved, and two (PCBs 84 and 174) can be partially separated from coeluting congeners in a mixture of 144 congeners (the most abundant congeners in technical PCBs). The chiral resolution (R_S) of the enantiomeric pairs ranged between 0.6 and 2.0, with PCB 132 having the highest resolution. Furthermore, the congers that (partially) coelute with enantiomers of PCBs 84, 95, and 174 have low abundance in technical PCB as well as in environmental samples. Thus, all of the nine target PCBs could be separated from significant interfering compounds in a single GC×GC run. © 2001 John Wiley &amp; Sons, Inc. J Micro Sep 13: 300–305, 2001</p>","PeriodicalId":83120,"journal":{"name":"The journal of microcolumn separations : JMS","volume":"13 7","pages":"300-305"},"PeriodicalIF":0.0,"publicationDate":"2001-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/mcs.10010","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51277492","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Determination of tri- through heptachlorobiphenyls in water samples by SPME-GC-MS-MS: Comparison of PDMS and PDMS-DVB coatings","authors":"Pedro Landín,&nbsp;María Llompart,&nbsp;Mercedes Lourido,&nbsp;Rafael Cela","doi":"10.1002/mcs.10007","DOIUrl":"10.1002/mcs.10007","url":null,"abstract":"<p>Solid-phase microextraction technique coupled to gas chromatography-mass spectrometry–mass spectrometry has been applied to the extraction of polychlorinated biphenyls ranging from three to seven chlorine substituents. The behavior of two polymeric coatings, polydimethylsiloxane and polydimethylsiloxane-divinylbenzene was extensively studied. The influence of experimental parameters as extraction mode (direct and headspace approach), temperature, volume of sample, agitation, and sample time were evaluated. The two fibers were adequate for polychlorobiphenyl (PCB) extraction and analytes could be quantified at the subpicogram per milliliter level with extraction times of 60 min. Nevertheless, comparison of extraction efficiencies showed the advantages of working with the mixed coating, specially for less chlorinated PCBs. Linearity was evaluated for a 200-fold concentration range from femtogram per milliliter to picogram per milliliter level. The two coatings were applied to the determination of the target analytes in two different matrices. © 2001 John Wiley &amp; Sons, Inc. J Micro Sep 13: 275–284, 2001</p>","PeriodicalId":83120,"journal":{"name":"The journal of microcolumn separations : JMS","volume":"13 7","pages":"275-284"},"PeriodicalIF":0.0,"publicationDate":"2001-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/mcs.10007","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51277126","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Relationships for modeling the performance of rectangular gas chromatographic columns","authors":"Glenn E. Spangler","doi":"10.1002/mcs.10008","DOIUrl":"10.1002/mcs.10008","url":null,"abstract":"<p>Golay's theory for open tubular GC columns was recently revised for application to rectangular GC columns. The HETP was found to be the same as for open tubular columns provided the average linear velocity, <i>ū</i>, and the resistance-to-mass-transfer-in-the-gas-phase, <i>C_M</i>, are redefined. In this paper, a simplified expression for the average linear velocity is derived and used to fit a variety of exit flow data collected on microfabricated rectangular GC columns. Also the resistance-to-mass-transfer-in-the-gas-phase is studied and the results compared to earlier relationships derived by Giddings, Chang, Myers, Davis and Caldwell, and by Golay. The three theories agree, with the present theory predicting a slightly higher value for <i>C_M</i> for large retention indices. The slightly higher value for <i>C_M</i> is attributed to the geometry for the rectangular column that is better modeled with the present theory than the former theories. © 2001 John Wiley &amp; Sons, Inc. J Micro Sep 13: 285–292, 2001</p>","PeriodicalId":83120,"journal":{"name":"The journal of microcolumn separations : JMS","volume":"13 7","pages":"285-292"},"PeriodicalIF":0.0,"publicationDate":"2001-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/mcs.10008","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51277149","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Use of cyclodextrins for the separation of monoterpene isomers by micellar electrokinetic capillary chromatography","authors":"Maria Regina A. Rodrigues,&nbsp;Elina B. Caramão,&nbsp;Lourdes Arce,&nbsp;Angel Rios,&nbsp;Miguel Valcárcel","doi":"10.1002/mcs.10009","DOIUrl":"10.1002/mcs.10009","url":null,"abstract":"<p>The micellar electrokinetic capillary chromatographic method for the determination of monoterpenes such as camphene, α-pinene, β-pinene, γ-terpinene, α-terpinene, terpinolene and p-cymene was established. Addition of cyclodextrins (CDs) to the buffer solution permits the separation of these monoterpenes. The separation is dependent on the type of CD, and gamma-CD was the most effective cyclodextrin, in the method here developed. The method permits low concentrations of monoterpenes to be separated and detected. The addition of an organic solvent (acetonitrile) as modifier in the buffer (10 m<i>M</i> NaH₂PO₄, 6 m<i>M</i> Na₂B₄O₇, 50 m<i>M</i> SDS, 7 m<i>M</i> de γ-CD) allowed this separation. The analysis was performed with a positive power supply of 20 kV at a temperature of 25°C. The samples were hydrostatically (5 s) introduced into the anodic end of the capillary and electropherograms were recorded at 200 nm. This method could be highly suitable for the separation and determination of monoterpenes in essential oils of leaves, and the flowers of marjoram and oregano among other real samples. © 2001 John Wiley &amp; Sons, Inc. J Micro Sep 13: 293–299, 2001</p>","PeriodicalId":83120,"journal":{"name":"The journal of microcolumn separations : JMS","volume":"13 7","pages":"293-299"},"PeriodicalIF":0.0,"publicationDate":"2001-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/mcs.10009","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51276786","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Shape selectivity: A key factor in comprehensive two-dimensional gas chromatographic analysis of toxic PCBs","authors":"Peter Haglund,&nbsp;Mikael Harju,&nbsp;Ruby Ong,&nbsp;Philip Marriott","doi":"10.1002/mcs.10011","DOIUrl":"10.1002/mcs.10011","url":null,"abstract":"<p>A number of toxic planar PCBs, that is, PCB 77, 105, 118, 126, 156, and 169, were successfully separated from other PCB congeners present in technical PCB formulations using comprehensive GC×GC. The planar PCBs were selectively retained using a liquid crystal column, which was used as the first-dimension column. A short and narrow bore (0.25 m×0.1 mm) nonpolar 5%-phenyl-methylpoly-siloxane column was used as the second-dimension column. A longitudinally modulating cryogenic system (LMCS) was used to modulate the first-dimension signal. Since the planar PCBs elute from the first column at relatively high oven temperatures they were rapidly eluted from the second column. Altogether, this resulted in a significant peak sharpening, and a 20-fold increase in the signal-to-noise ratio, as compared to standard one-dimensional GC. This column set also seems to separate seven frequently measured congeners, that is, PCBs 28, 52, 101, 118, 138, 153, and 180, from other major PCB congeners. © 2001 John Wiley &amp; Sons, Inc. J Micro Sep 13: 306–311, 2001</p>","PeriodicalId":83120,"journal":{"name":"The journal of microcolumn separations : JMS","volume":"13 7","pages":"306-311"},"PeriodicalIF":0.0,"publicationDate":"2001-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/mcs.10011","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51277541","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Critical assessment of electrolyte systems for the capillary electrophoresis analysis of phenolic compounds in herbal extracts","authors":"Fabiana Novaes Fonseca,&nbsp;Massuo Jorge Kato,&nbsp;Levi Oliveira Jr.,&nbsp;Nestor Pinto Neto,&nbsp;Marina Franco Maggi Tavares","doi":"10.1002/mcs.1047","DOIUrl":"10.1002/mcs.1047","url":null,"abstract":"<p>This work presents a comparative evaluation of electrolyte systems for the capillary electrophoresis analysis of the phenolic compounds apigenin and luteolin, and their corresponding 7-<i>O</i>-glucosides naringenin, rutin, quercetin, umbelliferone, herniarin, chlorogenic, and caffeic acids, in methanolic, glycolic, and hydroalcoholic extracts of <i>Matricaria recutita</i> L. (Asteraceae). The electrolytes included tetraborate buffer at different pHs and concentrations, containing varied amounts of sodium dodecyl sulfate, β-cyclodextrin, and acetonitrile. The electrophoretic profile of the extracts changes considerably from electrolyte to electrolyte. However, in a single electrolyte, the profile of different extracts seems to be very similar (identical elution order), varying only in relative composition. The best condition for quantitative work was 20 mmol/L tetraborate buffer, pH 10, using direct detection at 337 nm. Baseline resolution of 9 among 11 selected standards was achieved readily in this electrolyte, showing distinct migration patterns for flavonoid aglycones (flavones, dihydroflavonols, and flavonols), coumarins, and acidic phenylpropanoids. To assure reproducibility, several capillary conditioning procedures were tested. Electrokinetic rinses with tetraborate buffer prior to sample injection gave the best results. Precision of migration times and peak areas were better than 4 and 2%, respectively, for 10 consecutive injections of the methanolic extract. A few method validation parameters also are reported, such as linearity (<i>r</i>²&lt;0.999, concentration range from 5.0 to 75.0 μg/mL), limit of detection (3.8 μg/mL), and limit of quantitation (11.5 μg/mL), referred to apigenin, a commonly used compound to standardize chamomile extracts for topical use. Flavonoid glucosides that have distinct sugar moieties were separated readily in free solution; however, those with similar sugar moieties were separated only in micellar medium, using β-cyclodextrin as the additive. The presence of reference compounds in the extracts was confirmed by spiking techniques and their identification was assisted by a UV-spectra library. The validity of the diode array detector as an identification tool for phenolic compounds also is discussed. © 2001 John Wiley &amp; Sons, Inc. J Micro Sep 13: 227–235, 2001</p>","PeriodicalId":83120,"journal":{"name":"The journal of microcolumn separations : JMS","volume":"13 6","pages":"227-235"},"PeriodicalIF":0.0,"publicationDate":"2001-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/mcs.1047","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51279971","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ion trap mass spectrometry as detector for capillary electrochromatography of peptides: Possibilities and limitations","authors":"Marco Gaspari,&nbsp;Marjan Guček,&nbsp;Karin Walhagen,&nbsp;Rob J. Vreeken,&nbsp;Elwin R. Verheij,&nbsp;Ubbo R. Tjaden,&nbsp;Jan Van der Greef","doi":"10.1002/mcs.1049","DOIUrl":"10.1002/mcs.1049","url":null,"abstract":"<p>Capillary electrochromatography has been coupled to an ion trap mass spectrometer via a sheath flow electrospray interface. Peptide analysis was performed on 25 cm columns packed with C₁₈-bonded silica particles, and very fast separations were obtained. Full mass spectrometry and tandem mass spectrometry (MS/MS) detection were evaluated in terms of sensitivity and scanning speed. The separation of seven selected peptides and their detection by MS/MS in selected reaction monitoring mode was demonstrated. The performance of this sheath flow interface also was compared with the previously reported sheathless interface. Despite the loss in sensitivity (20–40-fold), the sheath flow interface was shown to be superior in terms of ruggedness, and allowed the use of higher electric fields to achieve faster analysis times. © 2001 John Wiley &amp; Sons, Inc. J Micro Sep 13: 243–249, 2001</p>","PeriodicalId":83120,"journal":{"name":"The journal of microcolumn separations : JMS","volume":"13 6","pages":"243-249"},"PeriodicalIF":0.0,"publicationDate":"2001-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/mcs.1049","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51279682","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Determination of alkaloids in Sophora flavescens ait. and Sophora viciifolia Hance by capillary zone electrophoresis","authors":"Xiaodan Su,&nbsp;Xiukun Wang,&nbsp;Yan Li,&nbsp;Jiashi Li,&nbsp;Yuning Yan,&nbsp;Yuting Chen,&nbsp;Huwei Liu","doi":"10.1002/mcs.1046","DOIUrl":"10.1002/mcs.1046","url":null,"abstract":"<p>Capillary zone electrophoretic (CZE) separation of pharmacologically active alkaloids, matrine, sophocarpine, sophoridine, oxymatrine, and oxysophocarpine, was systematically optimized, and their contents in different parts of <i>Sophora</i> species were quantitatively determined within 16 min under the following optimized conditions: 0.04 mol/L citrate buffer system at pH 4.5, applied voltage 30 kV, capillary temperature 25°C, and diode array detection at 201 nm. The recoveries are from 90 to 108%, with repeatability ranging from 0.7 to 4.2% (relative standard deviation) and the detection limits ranging from 0.032 to 0.070 mg/mL (signal to noise ratio=3). The proposed CZE method is suitable for routine analysis and quality control of herbal medicines that contain these alkaloids. © 2001 John Wiley &amp; Sons, Inc. J Micro Sep 13: 221–226, 2001</p>","PeriodicalId":83120,"journal":{"name":"The journal of microcolumn separations : JMS","volume":"13 6","pages":"221-226"},"PeriodicalIF":0.0,"publicationDate":"2001-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/mcs.1046","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51279930","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reference steroid profiles in 0 to 3 day old neonates*","authors":"L. C. Bekker,&nbsp;M. J. Bester,&nbsp;P. Hurter","doi":"10.1002/mcs.1050","DOIUrl":"10.1002/mcs.1050","url":null,"abstract":"<p>The excretion of 16α-hydroxypregnenolone, 16α-hydroxy-DHEA, and 11-oxo-pregnanetriol was studied in 28 neonates with unambiguous genitalia. The 16α-hydroxypregnenolone:16α-hydroxy-DHEA ratio was determined and compared with the steroid ratios described by Shackleton and by Reynolds, and used to diagnose neonates with congenital adrenal hyperplasia. The technique used was capillary gas chromatography after solid phase extraction, enzymatic hydrolysis, and derivatization of the analytes. Duplicate analyses were performed to provide identification (mass selective detection–quadrupole ion trap) and quantification (flame ionization detection). © 2001 John Wiley &amp; Sons, Inc. J Micro Sep 13: 250–254, 2001</p>","PeriodicalId":83120,"journal":{"name":"The journal of microcolumn separations : JMS","volume":"13 6","pages":"250-254"},"PeriodicalIF":0.0,"publicationDate":"2001-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/mcs.1050","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51279720","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Optimization of solid phase microextraction analysis of aroma compounds in a Portuguese muscatel wine must","authors":"Luís M. T. Vaz Freire,&nbsp;A. M. Costa Freitas,&nbsp;A. M. Relva","doi":"10.1002/mcs.1048","DOIUrl":"10.1002/mcs.1048","url":null,"abstract":"<p>The fundamental suitability of solid-phase microextraction (SPME) has been investigated for the quantitative determination of eight aroma compounds present in a Portuguese muscatel wine must. The method has been optimized using a commercially available fiber coated with 85 μm polyacrylate (PA). The matrix effect was evaluated by comparing the results obtained with the standard additions method to those obtained, for the same analyte, by means of a calibration curve (internal standard method). The results obtained with the standard additions method show poor accuracy and higher confidence limits than those obtained by the calibration curve. Experiments during the SPME process were carried out to investigate the influence of (1) ethanol concentration and (2) high concentrations of one analyte on the absorption of minor components. No significant decrease in peak response was observed either for ethanol concentration from 3 to 12% or for excess concentration of one analyte over the others. The method was evaluated with respect to the linearity, within run precision and limit of detection. The curves obtained by plotting mass ratio vs. area ratio showed higher correlation coefficient <i>R</i>²&gt;0.99 for most compounds. The use of internal standard minimizes quantitative errors due to the extraction process and injection. Ethanol concentration does not seem to affect quantitative determination. Polydimethylsiloxane (PDMS) fiber is more suitable for the analysis of esters, whereas polyacrylate is suitable for alcohols of low molecular weight and terpene quantification. The method has been applied to a Portuguese wine must to investigate the recovery of its aroma profile, formed by <i>Saccharomyces cerevisiae</i> during the wine-must fermentation, using organophilic pervaporation [1]. © 2001 John Wiley &amp; Sons, Inc. J Micro Sep 13: 236–242, 2001</p>","PeriodicalId":83120,"journal":{"name":"The journal of microcolumn separations : JMS","volume":"13 6","pages":"236-242"},"PeriodicalIF":0.0,"publicationDate":"2001-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/mcs.1048","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51280007","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}