DB-5 Capillary Column Research Articles

TNF-α plays a role in hepatocyte apoptosis in Niemann-Pick type C liver disease

Niemann-Pick type C (NPC) is a fatal autosomal recessive lysosomal storage disease clinically characterized by neurodegeneration and liver disease. Heterogeneous mutations in the NPC1 and NPC2 genes cause impaired egress of free cholesterol from lysosomes, leading to accumulation of cholesterol and glycosphingolipids. Key features of NPC liver disease include hepatic apoptosis, inflammation, and fibrosis. It is unclear what signaling events regulate these disease processes in NPC. We hypothesize that tumor necrosis factor alpha (TNF-alpha), which is involved in both proinflammatory and apoptotic signaling cascades, is a key mediator of inflammation, apoptosis, and fibrosis in NPC liver disease. In this study, we evaluated the role of TNF-alpha signaling in NPC liver disease by utilizing NPC1-specific antisense oligonucleotides to knock down NPC1 expression in control and TNF-alpha knockout mice. In the absence of TNF-alpha, NPC1 knockdown produced liver disease with significantly less inflammation, apoptosis, and fibrosis.

A Novel Method for the Determination of Guanfacine in Urine by Gas Chromatography-Mass Spectrometry

Guanfacine (Tenex), an antihypertensive available since 1975, has recently been indicated for the treatment of attention deficit hyperactivity disorder in children (Intuniv). Because of this new usage, a gas chromatography-mass spectrometry method was developed and validated for the determination of guanfacine in urine. Guanfacine and 100 ng of protriptyline (internal standard) were extracted from 1.0 mL urine with 0.5 mL of saturated carbonate/bicarbonate buffer and 2 mL of ethyl acetate. The solvent extract was evaporated and derivatized with heptaflurobutyric anhydride in n-butyl chloride. Chromatographic separation was achieved using a DB-5 capillary column (30 m x 0.32 mm, 0.25 microm). Ions monitored for guanfacine were m/z 86.1, 272.1, and 274.1, and ions monitored for protriptyline were m/z 191.1 and 189.1. Concentrations were determined using calibrators over the range of 0.1-2.0 mg/L. The linear regression for all calibration curves had r2 values > or = 0.99. The limit of detection was 0.05 mg/L; limit of quantitation was 0.1 mg/L; and upper limit of linearity was 10.0 mg/L. Percent recovery of guanfacine at 0.1 and 2.0 mg/L was 93% and 71%, respectively. The method was found acceptable for routine quantitative analysis of guanfacine in urine.

Rapid Determination of Low-Level Sulfur Compounds in Beer by Headspace Gas Chromatography with a Pulsed Flame Photometric Detector

Off-flavors in beer are frequently due to the presence of sulfur compounds. A simple and sensitive method for the analysis of volatile sulfur compounds in beer at trace levels was developed using headspace gas chromatography with a pulsed flame photometric detector. Different capillary columns were tested, and a 60-m nonpolar DB-1 capillary column was found to be the most appropriate. Four sulfur compounds, including hydrogen sulfide, methanethiol, ethanethiol, and dimethyl sulfide, could be quantified simultaneously using ethyl methyl sulfide as the internal standard. Calibration curves were established in a 4% (vol/vol) ethanolic solution with pH adjusted to 4.0; linear correlation coefficients (r) were greater than 0.99 for all target compounds. This method enables four sulfur compounds in beer to be determined at trace levels, with recoveries greater than 96%, a repeatability error of less than 5%, and limits of detection between 0.1 and 2 μg/L. The overall method was successfully applied to the determination of sulfur compounds studied in several beers.

Unusual Fatty Acids in the Fat Body of the Early Nesting Bumblebee, Bombus pratorum

Unusual fatty acids with 24, 26, and 28 carbon atoms were found in triacylglycerols (TAGs) isolated from fat body tissue of bumblebee Bombus pratorum. The most abundant one was (Z,Z)-9,19-hexacosadienoic acid. Its structure was determined by mass spectrometry after derivatization with dimethyl disulfide and by infrared spectroscopy. ECL (equivalent chain length) values of its methyl ester were determined on both DB-1 and DB-WAX capillary columns. (Z,Z)-9,19-Hexacosadienoic acid is quite rare in nature. So far it has been identified only in marine sponges, and this work is the first evidence of its occurrence in a terrestrial organism. HPLC/MS analysis of the bumblebee TAGs showed that (Z,Z)-9,19-hexacosadienoic acid is present in one third of all TAG molecular species. As it was found in all sn-TAG positions, it is likely that (Z,Z)-9,19-hexacosadienoic acid is transported to tissues. Interestingly, labial gland secretion of B. pratorum was found to contain (Z,Z)-7,17-pentacosadiene, a hydrocarbon with markedly similar double bond positions and geometry. Possible biosynthetic relationships between these two compounds are discussed.

Determination of musty odorants, 2-methylisoborneol and geosmin, in environmental water by headspace solid-phase microextraction and gas chromatography–mass spectrometry

A simple and sensitive method for the determination of musty odorants, 2-methylisoborneol (MIB) and geosmin (GSM), in environmental water was developed by headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography–mass spectrometry. MIB and GSM were separated within 10 min using a DB-1 capillary column and detected in the selective ion monitoring mode. HS-SPME using a polydimethylsiloxane/divinylbenzene fiber provided effective sample enrichment, and was carried out by fiber exposition at 70 °C for 30 min. Using this method, the calibration curves of MIB and GSM were linear in the range of 0–500 pg/mL, with a correlation coefficient above 0.9977 ( n = 24). The detection limits (S/N = 3) of MIB and GSM were 0.9 and 0.6 pg/mL, respectively. This method was successfully applied to the analysis of environmental water samples without interference peaks.

The impurity characteristics of methamphetamine synthesized by Emde and Nagai method

Impurity profiling and classification of seized methamphetamine may play an important role in the interpretation of analytical results, the determination of the synthetic method employed, and the criminal investigations of drug traffic routes. Our study is focused on classifying seized methamphetamine samples according to the groups sorted by the types and quantities of impurities present in illicit methamphetamine samples. The samples (100 mg) were dissolved in 2 mL of potassium phosphate buffer (pH 7.0), extracted with 200 μL of ethyl acetate under basic condition, and then analyzed by gas chromatography-mass spectrometry (GC–MS) with a DB-1 capillary column (30 m × 0.25 mm i.d., 0.25 μm). Five impurities are used as criteria for the classification of seized methamphetamine samples by Emde and Nagai method. A total of fifty-two samples of seized methamphetamine were analyzed by GC–MS and classified by five organic impurities, and then sorted into four groups, which are Nagai type, Emde Type, Undetermined I type, and Undetermined II type.

Comparison and classification of methamphetamine seized in Japan and Thailand using gas chromatography with liquid–liquid extraction and solid-phase microextraction

Methamphetamine (MA) is one of the most frequently abused drugs worldwide. The aim of this study is to improve the analytical method for profiling MA impurity in order to compare and classify MA crystals seized in different countries and to investigate the relationships between seizures. To compare MA samples seized in Japan and Thailand, the following analytical method was adopted. A 50 mg sample of MA·HCl was dissolved in 1 ml of buffer solution (four parts 0.1 M phosphate buffer, pH 7.0, and one part 10% Na 2CO 3), impurities were extracted with 0.5 ml of ethyl acetate containing four internal standards ( n-decane, n-pentadecane, n-eicosane and n-octacosane) and analyzed by gas chromatography with a flame ionization detector on a DB-5 capillary column (0.32 mm i.d. × 30 m, film thickness 1.0 μm). Fourteen characteristic peaks on chromatograms were selected for the comparison and classification of samples, and the data were evaluated by the Euclidean distance of the relative peak areas after logarithmic transformation. Sixty-nine samples seized in Japan and 42 seized in Thailand were analyzed. The samples were classified into four groups roughly by cluster analysis. In addition, when it was difficult to compare samples that had fewer impurities on chromatograms obtained from liquid–liquid extraction (LLE), solid-phase microextraction (SPME) was effective. Because many characteristic peaks were detected using SPME, SPME made it easy to compare samples of high purity. The combination of LLE and SPME was useful for impurity profiling of MA samples seized in different countries.

Determination of isophorone in food samples by solid-phase microextraction coupled with gas chromatography–mass spectrometry

A simple and sensitive method for the determination of isophorone in food samples was developed by headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography–mass spectrometry (GC–MS). Isophorone was separated within 10 min by GC–MS using a DB-1 capillary column and detected with selective ion monitoring mode. The HS-SPME using a polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber provided effective sample enrichment, and was carried out by fiber exposition at 60 °C for 45 min. The extracted isophorone was easily desorbed by fiber exposition in the injection port of a capillary GC–MS system, and carryover was not observed. Using this method, the calibration curve of isophorone was linear in the range 20–1000 pg/mL, with a correlation coefficient 0.9996 ( n = 18), and the detection limit (S/N = 3) was 0.5 pg/mL. The HS-SPME/GC–MS method showed 25,000-fold higher sensitivity than the direct injection method (1 μL injection). The within-day and between-day precisions (relative standard deviations) at the concentration of 1 ng/mL isophorone were 3.9% and 6.1% ( n = 5), respectively. This method was successfully applied to the analysis of food samples without interference peaks. The recoveries of isophorone spiked into food sample were above 84% for a 50 or 500 pg/mL spiking concentration. The analytical results of the contents of isophorone in various food samples were presented.

Determination of the Enthalpies of Vaporization of Cyclic Organic Peroxides by Correlation of Changes in Gas Chromatographic Retention Times

Liquid and solid cyclic peroxides derived from aliphatic ketones are explosive materials so their enthalpies of vaporization and other thermodynamic or condensed-phase properties cannot be measured directly. In this work the enthalpies of vaporization of peroxides at 298.15 K were estimated simply from gas chromatographic retention times measured at different temperatures. The technique correlates changes in the retention times of compounds whose enthalpies of vaporization are known (called the reference series), with those of the compounds of interest. If tR′ is the adjusted retention time (retention time of each compound minus the retention time of unretained diethyl ether, used as solvent) a plot of ln tR′ against 1/T for each compound (reference compounds and cyclic peroxides) results in a straight line (r2 > 0.99 for all compounds). The enthalpy of transfer from solution to the vapor state (ΔsolgHm) can be obtained by multiplying the slope by the gas constant (R). A second plot correlates the enthalpies of transfer from solution to the vapor state (ΔsolgHm), as measured by gas–liquid chromatography (GLC), with enthalpies of vaporization of reference materials (ΔvapHm at 298.15 K) available in the literature. C9–C15 fatty acid methyl esters and hydrocarbons were used as reference compounds. The enthalpies of vaporization of the cyclic organic peroxides were calculated from the equation of the line obtained in this second correlation, the slope of which was ΔvapHm (at 298.15 K)/ΔgsolHm. The experiments were performed under isothermal conditions with a DB-5 capillary column, flame-ionization detection (FID), and nitrogen as carrier gas. The column temperature was varied over a range of at least 30–70 K between 403 and 473 K, with chromatograms being acquired at 10 K intervals. Enthalpies of vaporization of cyclic organic peroxides are not available in the literature, and the values given in this paper, obtained by gas chromatography, are the first to be reported.

Simultaneous determination of urinary hippuric acid, o-, m- and p-methylhippuric acids, mandelic acid and phenylglyoxylic acid for biomonitoring of volatile organic compounds by gas chromatography–mass spectrometry

A sensitive and precise method for the simultaneous determination of hippuric acid, o-, m- and p-methylhippuric acids, mandelic acid and phenylglyoxylic acid, which are major urinary metabolites of toluene, o-, m- and p-xylenes, styrene and ethylbenzene, respectively, was developed. These metabolites were converted into their methyl ester derivatives with methanol in hydrochloric acid, and then quantitated by gas chromatography–mass spectrometry (GC–MS) with selected ion monitoring using a DB-1 capillary column. The injected compounds were quantitatively and reproducibly resolved within 19 min with a detection limit of 8–27 pg. The calibration curves were linear in the range of 0.05–25 μg for each compound, with correlation coefficients above 0.9999. This method was successfully used to analyze small amounts of both rat and human urine samples without any interference from coexisting substances. Overall recoveries of these compounds spiked in urine samples were 92–104%. The analytical results of the contents of these metabolites in the rat and human urine samples are presented.

The temperature dependence of the retention index for n-alkyl esters of acetic, propionic, cyclohexanecarboxylic, benzoic and phenylacetic acid on DB-1 and DB-5 capillary columns

The temperature dependence of the retention index was studied for n-alkyl esters of acetic, propionic, cyclohexanecarboxylic, benzoic and phenylacetic acid on DB-1 and DB-5 capillary columns. The study was performed over various temperature ranges depending on the volatility of the ester. Two linear equations of the temperature dependence of the retention data on the column temperature and its reciprocal as variables were studied. Agood linearity of the retention index versus column temperature was found.

Analysis of the Essential Oil from Radix Bupleuri Using Capillary Gas Chromatography

A simple and rapid capillary gas chromatographic (CGC) method with flame ionization detection has been newly developed for analysis of the essential oil from Radix Bupleuri. Twenty components were identified with gas chromatography-mass spectrometry. E-2-heptenal, furan, 2-pentyl, and E-2-nonenal were quantified simultaneously using the internal standard method. Decane was used as an internal standard. Separation and quantification were achieved on a DB-5 capillary column (30 m x 0.25 mm i. d., 0.25-microm film thickness). The oven temperature was programmed as follows: 60 degrees C to 70 degrees C at 1 degree C/min rate, 70 degrees C for 10 min, 3 degrees C/min to 120 degrees C, 20 degrees C/min to 250 degrees C, and held at 250 degrees C for 5 min. The oven pressure was programmed as follows: 46.1 kPa for 25 min, 20.0 kPa/min to 77.6 kPa, and then held for 22 min. Split injection was conducted with a split ratio of 10:1; flow-rate, 1.00 ml/min; carrier gas, nitrogen; injector temperature, 280 degrees C; and detector temperature, 280 degrees C. The system proved effective in resolving E-2-heptenal, furan, 2-pentyl, and E-2-nonenal peaks from their interfering components. The method displayed excellent linearity in the range of 26.8-1072 microg/ml (E-2-heptenal), 6.5-1292 microg/ml (furan, 2-pentyl), and 7.8-1564 microg/ml (E-2-nonenal). The average recovery rates of E-2-heptenal, furan, 2-pentyl, and E-2-nonenal were 100.3%, 102.8%, and 97%, respectively. CGC is a quick and accurate method for analysis of the essential oil from Radix Bupleuri.

A COMPARATIVE STUDY OF THE ESSENTIAL OILS OF FOUR GONIOTHALAMUS SPECIES

A COMPARATIVE STUDY OF THE ESSENTIAL OILS OF FOUR GONIOTHALAMUS SPECIES

ESSENTIAL OILS FROM THREE CURCUMA SPECIES COLLECTED IN THAILAND

ESSENTIAL OILS FROM THREE CURCUMA SPECIES COLLECTED IN THAILAND

Gas chromatographic–mass spectroscopic determination of benzene in indoor air during the use of biomass fuels in cooking time

A gas chromatography-mass spectroscopic method in electron ionization (EI) mode with MS/MS ion preparation using helium at flow rate 1 ml min(-1) as carrier gas on DB-5 capillary column (30 m x 0.25 mm i.d. film thickness 0.25 microm) has been developed for the determination of benzene in indoor air. The detection limit for benzene was 0.002 microg ml(-1) with S/N: 4 (S: 66, N: 14). The benzene concentration for cooks during cooking time in indoor kitchen using dung fuel was 114.1 microg m(-3) while it was 6.6 microg m(-3) for open type kitchen. The benzene concentration was significantly higher (p < 0.01) in indoor kitchen with respect to open type kitchen using dung fuels. The wood fuel produces 36.5 microg m(-3) of benzene in indoor kitchen. The concentration of benzene in indoor kitchen using wood fuel was significantly (p < 0.01) lower in comparison to dung fuel. This method may be helpful for environmental analytical chemist dealing with GC-MS in confirmation and quantification of benzene in environmental samples with health risk exposure assessment.

Preparative Monohydroxyflavanone Syntheses and a Protocol for Gas Chromatography-Mass Spectrometry Analysis of Monohydroxyflavanones

We describe a facile efficient, and preparative approach for monohydroxyflavanone syntheses. Using this protocol, a hydroxyl is regio-selectively introduced at one carbon of a flavanone A- or B-ring per synthesis. The seven possible isomers were each synthesized from the corresponding monomethoxymethoxylated 2'-hydroxychalcones in acidic solution. These monohydroxyflavanones were characterized using a gas chromatography-mass spectrometry (GC-MS) system that incorporated a DB-5 capillary column. Ours is the first report of a preparative synthetic method during which a single hydroxyl can be selectively added to a flavanone A- or B-ring at any position. We are also the first to develop a procedure that separates the seven isomers by GC and characterizes the mass spectra of the isomers. Both the synthetic method and the GC-MS conditions may become important tools during future flavanone metabolism and oxidation studies.

Methamphetamine impurity profiling using a 0.32 mm i.d. nonpolar capillary column

Classification of seized methamphetamine by impurity profiling can provide very useful information in criminal investigations of drug traffic routes, sources of supply and relationships between seizures. The aim of this study is to improve and develop an analytical method for detecting impurities such as starting materials and by-products in illegally prepared methamphetamine·HCl samples. A 50 mg sample of methamphetamine·HCl was dissolved in 1 ml of buffer solution (four parts 0.1 M phosphate buffer pH 7.0 and one part 10% Na 2CO 3). Impurities were extracted with 0.5 ml of ethyl acetate containing four internal standards (ISs) ( n-decane, n-pentadecane, n-nonadecane and n-hexacosane) and analyzed by gas chromatography (GC) using a flame ionization detector (FID) on a DB-5 capillary column ( 0.32 mm i.d. ×30 m, film thickness 1.0 μm). The use of a middle-bore column offered better separation of the impurity peaks. The correction of the retention times of impurity peaks with four ISs made peak identification very accurate for subsequent data processing. Twenty-four characteristic peaks were selected for comparison and similarity and/or dissimilarity between samples, and the data were evaluated by the Euclidean distance of the relative peak areas after logarithmic transformation. The results indicate that the present method would be useful for methamphetamine impurity profiling.

Determination of ticlopidine in human plasma by capillary gas chromatography with ion trap detection

A gas chromatographic method for determination of ticlopidine in human plasma using mass spectrometric detection was developed. A Perkin Elmer model 8500 gas chromatograph coupled to an ion trap detector (ITD) in electron impact mode (EI) was used. The gas chromatograph was fitted with a 30 m×0.32 mm i.d., DB-17 capillary column with a film thickness of 0.25 μm. The compounds were isolated from plasma by Extrelut-1 solid-phase extraction using hexane as the solvent of elution. The detection and quantification limits for this method were 0.005 and 0.01 μg/ml, respectively. The calibration curves were linear from 0.01 and 2.5 μg/ml. Recoveries from human plasma spiked at 0.01 and 2.0 μg/ml ranged from 84.4 and 87.3%. The coefficient of variation (CV) was between 5.1 and 6.9%. The results show that the sensitivity, accuracy and precision of the method are adequate for the determination of ticlopidine in human plasma samples. The ITD in SIM mode allows the unequivocal identification of ticlopidine. The suitability of this method was evaluated in the determination of ticlopidine in plasma from healthy volunteers following oral administration of a dose of 500 mg/day.

Determination of Geosmin and 2-Methylisoborneol in Water using Solid Phase Extraction and Headspace-GC/MS.

A sensitive and reliable method for the analysis of geosmin and 2-methylisoborneol (2-MIB) in water sample was developed. In this study, geosmin and 2-MIB in the sample were enriched 40-fold using a technique of solid phase extraction and the resulting enriched solution was subjected to automated headspace-GC/MS system to determine them. The separation of the compounds was performed on a DB-1 capillary column and the detection was carried out by EIMS operated in either full-scan or selected ion monitoring (SIM) mode. In the SIM mode, the two compounds were determinable at the concentration of 0.1 ppt, and the recoveries and coefficients of variations were 104 and 6.1% for geosmin, and 115 and 7.5% for 2-MIB, respectively, at the addition level of 1 ppt. Although the detection limits in full-scan mode were 10-fold worse than those of SIM, it allows both determination and mass spectroscopic identification of the two compounds at the level of 1 ppt.

Gas chromatographic retention indices for N-substituted amino s-triazines on capillary columns. Part V. Temperature dependence of the retention index

The temperature dependence of the retention index was studied for N-substituted amino s-triazines on DB-1, DB-5 and DB-WAX capillary columns within the temperature range 190?230 ?C. Two linear equations with the column temperature and its reciprocal as variables were studied. The first one shows a slightly better precision for 2,4-bis(alky lamino)-6-chloro-s-triazines and 2-alkylamino-4,6-dichloro-s-triazines while the second one shows a better precision for 2,4-bis(cycloalkylamino)-6-chloro-s-triazines.