Wide-bore Capillary Column Research Articles

In Situ Polymerization of Phenolic Methylolurea in Cell Wall and Induction of Pulse–Pressure Impregnation on Green Wood

Impregnation of the cell wall with various chemicals continues to attract interest. For most studies, the method of impregnation is the vacuum-pressure process which is limited by the specimens’ size in thickness and the requirement for low moisture content. In the present study, we impregnated fast-growing poplar (Populus euramericana) green wood by pulse–pressure at 0.7–0.8 MPa for 50 min with phenolic methylolurea, and then the modifier in situ polymerized within the wood cell wall by kiln drying. The microscopy analysis showed that the pulse–pressure impregnation method could be feasible because of the presence of a wide-bore capillary column system in the poplar xylem. As a result, the chemical treatment reduced the hygroscopicity and increased the dimensional stability of wood. Reactions mainly happened within the interfibrillar amorphous region of the cell wall. Among the reactions were etherification and esterification since the covalent bonds formed between modifier methylol groups, wood hydroxyl, and acetic acid derived from hemicelluloses.

Determination of persistent organic pollutants by gas chromatography/laser multiphoton ionization/time-of-flight mass spectrometry

An authentic mixture of polychlorinated biphenyls was measured using a short wide-bore capillary column for the group separation of major components present in an actual sample of Kanechlor. The limits of detection were improved by ca. 2 fold in comparison with those obtained using a conventional capillary column, since the retention time was reduced and the amount of analytes introduced into the mass spectrometer per unit time could be increased. On the other hand, surface-water and sediment samples containing polycyclic aromatic hydrocarbons (PAHs) were collected from the river located in the vicinity of a waste water treatment plant. Even acenaphthylene, a minor component of the mixture could be measured for the sediment sample, and the concentrations were determined for several heavy PAHs. As demonstrated, a technique involving laser multiphoton ionization/time-of-flight mass spectrometry was useful as a sensitive and selective analytical tool for the trace analysis of persistent organic pollutants in an environmental sample.

Gas Chromatographic Determination of Bifenthrin in Technical and Selected Formulated Products: Collaborative Study

A GC method for the analysis of technical and formulated bifenthrin samples was evaluated in a collaborative study. Bifenthrin is determined by using a 50% (trifluoropropyl)-methylpolysiloxane wide-bore capillary column and flame ionization detector. Ten samples, consisting of four formulations and a technical material were analyzed by 12 collaborators using Youden pairs. The four formulation types included in this study were microemulsion (ME), wettable powder (WP), suspension concentrate (SC), and emulsifiable concentrate (EC). Variability in the analysis of two of the formulation types, SC and EC, was later found to be due to the noncommercial containers used to hold the test samples. Because of this, valid data could not be obtained for the EC and SC. For the two formulations for which valid data could be obtained, ME and WP, and the technical chemical, accuracy and variability results are typical of large data sets. For the technical chemical and the two formulations for which valid data were obtained, Official First Action is recommended.

Pressure-adjusted continual flow heart-cutting for the high throughput determination of amphetamine-type stimulant drugs in whole blood by fast multidimensional gas chromatography–mass spectrometry

Innovative features and technical improvements in modern bench-top quadrupole gas chromatograph–mass spectrometer (GC–MS) have prepared the way for faster and more cost-effective applications while still maintaining sufficient chromatographic resolution, speed of MS data acquisition and reliability of analytical methodology. In this paper, a short wide-bore capillary column with low film thickness (5m×0.32mm i.d., 0.1μm) was used a pre-fractionating column and only chosen heart-cuts were transferred to the second chromatographic dimension (15m×0.25mm i.d., 0.25μm) by means of a pressure-adjusted continual flow type switching device for quantification of five common amphetamine-type stimulant drugs. The instrumental setting used, in combination with carefully optimized operational fast GC and MS parameters, markedly decreased the retention times of the targeted analytes, e.g., amphetamine 0.891min and methamphetamine 1.037min, and the total chromatographic runtime (1.700min), as well as reducing the need for continuous cleaning of the MS ion source and increasing column life compared with conventional GC–MS approaches. The performance of the instrumental configuration and analytical method was evaluated in validation experiments and the method was also applied to authentic samples. The method demonstrates the potential of fast GC–MS in combination with a gas-phase microfluidic Deans switch device for analysing of (semi)volatile compounds, such as amphetamine-type stimulant (ATS) drugs. This should be particularly useful in modern laboratories aiming at cost-efficient analysis as well as the optimum use of available laboratory capacity and instrumentation.

Rapid and simple analysis of oxazolobenzodiazepine drugs in sera by wide-bore capillary gas chromatography with nitrogen-phosphorus detection using on-column methylation

A rapid and simple method for determination of oxazolobenzodiazepines (oxazolam, haloxazolam, mexazolam, cloxazolam, and flutazolam) in sera was developed by gas chromatography (GC) using nitrogen-phosphorus detection (NPD) and a methyl silicone fused-silica wide-bore capillary (DB-1) column. Underivatized oxazolobenzodiazepine drugs gave relatively low sensitivity, because of decomposition during their passage through the column. On the other hand, on-column methylation of the oxazolobenzodiazepines with 0.4 mM trimethylanilium hydroxide in methanolic solution resulted in higher sensitivity; detection was possible at levels at least two to eight times lower than those without derivatization. The average recoveries of five oxazolobenzodiazepines from 0.5-ml volumes of sera containing 1.0 or 0.1 μg of each drug were 88–101% and 66–106%, respectively. The limits of detection of methylated oxazolobenzodiazepines by wide-bore capillary GC-NPD were 50–100pg on column. This method could be used for determination of the drugs in actual serum specimens with concentrations as low as 25–70ng/ml.

Direct dating of archaeological pottery by compound-specific 14C analysis of preserved lipids.

A methodology is described demonstrating the utility of the compound-specific 14C technique as a direct means of dating archaeological pottery. The method uses automated preparative capillary gas chromatography employing wide-bore capillary columns to isolate individual compounds from lipid extracts of archaeological potsherds in high purity (>95%) and amounts (>200 microg) sufficient for radiocarbon dating using accelerator mass spectrometry (AMS). A protocol was developed and tested on n-alkanes and n-carboxylic acids possessing a broad range of 14C ages. Analytical blanks and controls allowed background 14C measurements to be assessed and potential sources of errors to be detected, i.e., contamination with modern or dead 14C, isotopic fraction effects, etc. A "Russian doll" method was developed to transfer isolated target compounds onto tin powder/capsules prior to combustion and AMS analyses. The major advantage of the compound-specific technique is that 14C dates obtained for individual compounds can be directly linked to the commodities processed in the vessels during their use, e.g., animal fats. The compound-specific 14C dating protocol was validated on a suite of ancient pottery whose predicted ages spanned a 5000-year date range. Initial results indicate that meaningful correlations can be obtained between the predicted date of pottery and that of the preserved lipids. These findings constitute an important step forward to the direct dating of archaeological pottery.

Determination of nitroaromatic, nitramine, and nitrate ester explosives in soil by gas chromatography and an electron capture detector

Hazardous waste site characterization, forensic investigations, and land mine detection are scenarios where soils may be collected and analyzed for traces of nitroaromatic, nitramine, and nitrate ester explosives. These thermally labile analytes are traditionally determined by high-performance liquid chromatography (HPLC); however, commercially available deactivated injection port liners and wide-bore capillary columns have made routine analysis by gas chromatography (GC) possible. The electron-withdrawing nitro group common to each of these explosives makes the electron capture detector (ECD) suitable for determination of low concentrations of explosives in soil, water, and air. GC-ECD and HPLC-UV concentration estimates of explosives residues in field-contaminated soils from hazardous waste sites were compared, and correlation ( r>0.97) was excellent between the two methods of analysis for each of the compounds most frequently detected: 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), 2,4-dinitrotoluene (2,4-DNT), 1,3-dinitrobenzene (1,3-DNB), 1,3,5-trinitrobenzene (TNB), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX). The analytes were extracted from soils with acetonitrile by 18 h of sonication in a cooled ultrasonic bath. Two soil-to-solvent ratios were evaluated: 2.00 g:10.00 ml and 25.0 g:50.0 ml. GC-ECD method detection limits were similar for the two soil-to-solvent ratios and were about 1 μg kg −1 for the di- and trinitroaromatics, about 10 μg kg −1 for the mono-nitroaromatics, 3 μg kg −1 for RDX, 25 μg kg −1 for HMX, and between 10 and 40 μg kg −1 for the nitrate esters (nitroglycerine [NG] and pentaerythritol tetranitrate [PETN]). Spike recovery studies revealed artifacts introduced by the spiking procedure. Recoveries were low in some soils if the amount of soil spiked was large (25.0 g) compared to the volume of spike solution added (1.00 ml). Recoveries were close to 100% when 2.00-g soil samples were spiked with 1.00 ml of solution. Analytes most frequently found in soils collected near buried land mines were the microbial transformation products of TNT (2-amino-4,6-dinitrotoluene [2-Am-DNT] and 4-amino-2,6-dinitrotoluene [4-Am-DNT]), manufacturing impurities of TNT (2,4-DNT, 2,6-DNT, and 1,3-DNB), and TNT. The microbial reduction products of the isomers of DNT and of 1,3-DNB were also detected, but the ECD response to these compounds is poor.

Injection of large-volume samples into wide-bore capillary columns

Some parameters (injected sample volume and the completeness of sample transfer) in the injection of large-volume gas-vapor and liquid samples into a wide-bore capillary column with intermediate sorption preconcentration were examined. It was demonstrated that this sample injection technique can be used in analytical practice.

Ultra-sensitive method for determination of ethanol in whole blood by headspace capillary gas chromatography with cryogenic oven trapping

We have established an ultra-sensitive method for determination of ethanol in whole blood by headspace capillary gas chromatography (GC) with cryogenic oven trapping. After heating a blood sample containing ethanol and isobutyl alcohol (internal standard, IS) in a 7.0-ml vial at 55°C for 15 min, 5 ml of the headspace vapor was drawn into a glass syringe and injected into a GC port. All vapor was introduced into an Rtx-BAC2 wide-bore capillary column in the splitless mode at −60°C oven temperature to trap entire analytes, and then the oven temperature was programmed up to 240°C for GC measurements with flame ionization detection. The present method gave sharp peaks of ethanol and IS, and low background noise for whole blood samples. The mean partition into the gaseous phase for ethanol and IS was 3.06±0.733 and 8.33±2.19%, respectively. The calibration curves showed linearity in the range 0.02–5.0 μg/ml whole blood. The detection limit was estimated to be 0.01 μg/ml. The coefficients of intra-day and inter-day variation for spiked ethanol were 8.72 and 9.47%, respectively. Because of the extremely high sensitivity, we could measure low levels of endogenous ethanol in whole blood of subjects without drinking. The concentration of endogenous ethanol measured for 10 subjects under uncontrolled conditions varied from 0 to 0.377 μg/ml (mean, 0.180 μg/ml). Data on the diurnal changes of endogenous ethanol in whole blood of five subjects under strict food control are also presented; they are in accordance with the idea that endogenous blood ethanol is of enteric bacterial origin.

Conditions of solid-phase extraction for the mixture of organophosphates and synthetic pyrethroids in human body fluids

Pesticide products composed of different types of chemicals are very common in China; one of the most typical examples is the mixture of organophosphate(s) and synthetic pyrethroid(s) being used as an insecticide. Suicides and accidents due to poisoning with these mixed pesticides are occasionally encountered in forensic practice. The isolation procedures for each group of pesticides by solid-phase extraction (SPE) from human plasma, urine and whole blood before analyses by gas chromatography (GC) were reported in our previous publications [1–3]. However, convenient isolation conditions to be used for a mixture of organophosphate and synthetic pyrethroid pesticides seem worthwhile studying. Three organophosphates (demeton, dimethoate and parathion) and four synthetic pyrethroids (methothrin, cyhalothrin, fenpropathrin and fenvalerate), as well as an internal standard (IS) cypermethrin, were used in our experiments. Sep-Pak C18 cartridges were obtained from Waters Associates, Milford, MA, USA, and a fused silica HP-17 wide-bore capillary column (10 m30.53 mm I.D., film thickness 2.0 mm) from Hewlett-Packard (HP) Co., Wilmington, DE, USA. GC was carried out on an HP-5890A instrument with flame ionization detection. GC conditions were: injection temperature 2508C, detection temperature 2808C, column temperature 150–2508C (158C/min). Seven pesticides were made up together into methanolic solution at 200 mg/ml (demeton, dimethoate and fenvalerate) and at 100 mg/ml (parathion, methothrin,

Evaluation of Thermal Migration of Ester-Type Plasticizers in Acrylonitrile-Butadiene Rubbers by Highly Sensitive Automated Thermal Desorption Gas Chromatography

A new method to evaluate thermal migration of plasticizers in acrylonitrile (AN)-butadiene rubbers was developed by use of automated thermal desorption gas chromatography (GC). A small piece of rubber sample weighing ca. 0.5 mg was subjected to thermal desorption at 260°C for 15 min in an automated thermal desorption GC system under a flow of nitrogen carrier gas. The desorbed plasticizer condensed in a trap was then directly stripped at 300°C for 15 min into a wide-bore fused-silica capillary separation column, programmed from 50°C to 280°C at a rate of 7.5°Cmin−1. Thus rapid and precise determination became possible for various plasticizers. such as di(2-ethylhexy1)-adipate. di(2-ethylhexy1)phthalate and di(2-ethylhexy1)sebacate in samples weighing less than 1 mg taken from given depths of the rubber sheet. This highly sensitive method enabled not only depth profiling of the plasticizers in rubber samples, but also rapid estimation of the diffusion coefficients for the plasticizers in various rubber samples with different AN content at various temperatures.

Determination of Nitroaromatic, Nitramine, and Nitrate Ester Explosives in Water Using Solid-Phase Extraction and Gas Chromatography--Electron Capture Detection: Comparison With High-Performance Liquid Chromatography

An analytical method for nitroaromatic, nitramine, and nitrateester explosives and co-contaminants in water based on solid-phase extraction (SPE) and gas chromatograph-electron capture detector (GC-ECD) is described. Samples are preconcentrated using cartridge or membrane SPE followed by elution with acetonitrile. The extract is compatible with GC and liquid chromatography, allowing direct comparison of concentration estimates obtained by different methods of determination and confirmation based on different physical properties. Quantitative GC analyses are obtained with deactivated direct-injection port liners, short widebore capillary columns, and high linear carrier gas velocities. Recoveries are 90% or greater for each of the nitroaromatics and nitrate esters and greater than 70% for nitramines and aminonitrotoluenes. Concentration estimates for well water extracts from military sites analyzed by GC-ECD and high-performance liquid chromatography (HPLC) methods show good agreement for the analytes most frequently detected (octahydro-1,3,5,7-tetranitro1,3,5,7-tetrazocine, hexahydro-1,3,5-trinitro-1,3,5-triazine, 2,4,6trinitrotoluene, and 1,3,5-trinitrobenzene). The GC provides lower method detection limits than HPLC for most analytes, but accurate calibration is more difficult. The ultraviolet detector used for HPLC has a much greater linear range than the ECD. The GC requires more care than the HPLC. Specifically, the injection port liner must be changed frequently for accurate determinations.

Determination of Methylmercury in Food Commodities by Gas-Liquid Chromatography with Atomic Emission Detection

A method was developed for determining methylmercury in various food commodities. The organomercurial species was converted to methylmercuric chloride by treatment of a sample homogenized with 1.8M HCl. The resulting chlorinated species was eluted from a Celite 545-sample homogenate column with methylene chloride. The eluate was treated with stannic chloride, and the analyte was isolated from coextractives by using a wide-bore capillary column with microwave-induced plasma atomic emission detection. The method was applied to both high- and low-moisture commodities during analysis of 32 samples of grains, cereal products, fruits, and vegetables. Methylmercury was found at trace levels (i.e., between a signal-to-noise ratio of 3:1 and 10:1) and up to 0.85 ppb. Recoveries of added methylmercury ranged from 70.0 to 114.0%. Limits of quantitation and detection were 0.63 and 0.24 pg on column, respectively, corresponding to 0.30 and 0.11 ng Hg/g sample for a 40 g sample treated according to the method.

Warning Odor of the North American Porcupine(Erethizon dorsatum)

Volatile compounds in the lipid coating of the lower-back quills of the North American porcupine,Erethizon dorsatum, were collected using headspace trapping on Tenax and analyzed by gas chromatography–mass spectrometry (GC-MS), GC with organoleptic detection, and GC with a chiral stationary phase. Over 50 components were isolated, primarily oxygenated aliphatics, lactones, and isoprenoids. The most abundant constituent was tetradecyl acetate, which does not contribute significantly to the odor of the quill lipids. GC with a wide-bore capillary column and a human nose as detector was used to determine the retention time of the peak with the characteristic porcupine odor. Comparison of this organoleptic chromatogram with those obtained with a flame ionization detector and GC-MS showed the compound to be a δ-decalactone. The racemic mixture of this optically active substance does not possess the unique odor. Resolution of the enantiomers of δ-decalactone by GC with a chiral cyclodextrin phase shows that the isomer possessing the characteristic porcupine odor is the(R)-δ-decalactone. We suggest the biological function of this compound is to serve as a warning odor, which, in conjunction with an initial quill strike, produces a conditioned aversion in potential predators.

A simple, rapid gas-liquid chromatographic procedure for the determination of valproic acid in serum.

A simple, rapid method for the gas-liquid chromatographic (GLC) determination of valproic acid in serum without prior derivatization on a Nukol wide-bore capillary column is presented. The method was determined to have a lower limit of detection (LOD) of 5 mg/L and a lower limit of quantitation (LOQ) of 10 mg/L; the method was linear up to 6000 mg/L. Within-run precision (expressed as percent coefficient of variation [CV]) for control specimens containing 60 mg/L and 120 mg/L was 4.3% CV (n = 10) and 3.0% CV (n = 10), respectively. The between-run precision of control sera analyzed over four week yielded 8% at 25 mg/L, 5% at 60 mg/L, and 3% at 120 mg/L. The absolute, uncorrected, analytical recoveries of valproic acid at 10, 32, and 120 mg/L were 97% (n = 5), 101% (n = 5), and 84% (n = 5), respectively. The absolute recovery of the internal standard was 97% (n = 9). Drugs commonly indicated for therapeutic monitoring and other serum constituents were found not to interfere with the procedure. The results of an intermethod comparison study of serum specimens analyzed by TDx immunoassay versus the presented GLC method demonstrated good correlation. At 95% confidence limits, no statistically significant differences were observed between results (p < 0.05). The method is particularly advantageous to toxicology laboratories because chromatography is performed on a polar GLC column that can be modified readily for the routine clinical analysis of other polar compounds such as ethylene glycol and other glycols.

Determination of Monoglycerides and Propylene Glycol Esters of Fatty Acids in Food Additive Preparations by GC without Derivatization

A simple method was developed for the determination of monoglycerides (MG) and propylene glycol esters of fatty acid (PGE) in food additive preparations without derivatization, using a gas chromatograph equipped with a deactivated inlet tube, by splitless injection. A wide-bore capillary column of 0.53mm i. d. was used for separation, and a flame ionization detector was used for detection. GC/MS (CI) and GC/FTIR were used for identification. Tetrahydrofuran was used as the extracting solvent, and hexane, diethyl ether and ethyl acetate as eluents. Monocaprylin, monocaprin, monopalmitin, monostearin, monoolein and monolinolein were detected in commercial food additive preparations.

Gas chromatography coupled with atomic absorption spectrometry — a sensitive instrumentation for mercury speciation

New instrumentation for the speciation of mercury is described, and is applied to the analysis of natural water samples. The separation of mercury species is effected using gas chromatography of derivatized mercury species on a widebore capillary column. The solvent is vented using a bypass valve and the separated mercury species are pyrolysed on-line at 800°C for production of mercury atoms. These are then detected by atomic absorption spectrometry (AAS) at the 253.7 and 184.9 nm lines simultaneously in a quartz cuvette. The use of the 184.9 nm line provides a more than five-fold increase in sensitivity compared with the conventional 253.7 nm line and an absolute detection limit of 0.5 pg of mercury. The dynamic range of the combined analytical lines provides a linear response over more than three orders of magnitude. A number of organic compounds not containing mercury are also detected following pyrolysis, especially at the 184.9 nm line. These background species must not co-elute at the retention times for methyl- and inorganic mercury, as otherwise a positive interference would result. By maximizing the chromatographic resolution and minimizing the band broadening in the cuvette by use of a make-up gas, the retention times of interest are freed from co-eluting background peaks. The instrumentation has been applied to the determination of ng l −1 concentrations of methyl- and inorganic mercury in Lake Constance, Germany and within the Lake Constance drinking water supply organization, Bodenseewasserversorgung (BWV). The accuracy for the sum of methyl- and inorganic mercury has been assessed by comparison with an independent method for total mercury based on AAS detection implemented at BWV. Relative detection limits using 1 litre water samples and 15 ml injections of the final hexane extract were 0.03 ng l −1 for methylmercury and 0.4 ng l −1 for inorganic mercury based on the 3j criterion.

Capillary GC Determination of Fentanyl and Midazolam in Human Plasma

A capillary GC method is described for simultaneously measuring fentanyl and midazolam in human plasma. Plasma was extracted at basic pH with cyclohexane–isopentanol (197:3) with Ro21-2212 added as internal standard and fentanyl derivative as carrier. The drug was back-extracted in H2SO4, and then the extract was made basic and reextracted with hexane. The organic phase was evaporated at 40°C under N2and the residue was dissolved in ethanol. A portion was analyzed on a wide-bore capillary column (10 m × 0.53 mm) of HP-1 (2.65 μm), operated at 255°C with N2as carrier gas and N–P detector. The calibration graph for fentanyl and midazolam was linear within the respective ranges of 0.5–100 and 5–1000 ng/ml with a correlation coefficient of 0.9998. The recovery of fentanyl and midazolam was 99.5 ± 4.5 and 99.9 ± 3.2%. The coefficient of variation within a run and between runs was less than 7%. The detection limit for fentanyl was 0.2 ng/ml plasma, and for midazolam was 0.5 ng/ml plasma. The method was applied to therapeutic drug monitoring and pharmacokinetic studies.

Determination of Dinoseb in Agricultural Products by NPD-GC

A simple method for the determination of dinoseb in agricultural products by capillary GC without methylation was developed. Dinoseb was extracted from grains and beans with acetonitrile, and the solution was washed with hexane. In the case of fruits and vegetables, dinoseb was extracted with acetone-hexane mixture (1:1), and the solution was washed with water. The extract was cleaned up with a silica gel column, and subjected to NPD-GC with a DB-1 widebore capillary column. Recoveries of dinoseb from agricultural products fortified with 0.05ppm were 79.2-87.8%, and the limit of detection was 0.005ppm.

A rapid gas chromatographic method quantitating clozapine in human plasma or serum for the purpose of therapeutic monitoring.

A gas chromatographic method using nitrogen-phosphorus detection was developed to quantitate clozapine in plasma or serum. Methyl clonazepam was used as an internal standard. Sample preparation included a single-step extraction with ethyl acetate, which was injected directly onto a wide-bore capillary column. Within-run and total precision, measured as percent coefficient of variation, were determined at low, therapeutic, and high clozapine plasma concentrations. The within-run precision for the low, therapeutic, and high clozapine plasma samples was 5.2, 2.7, and 2.4%, respectively. The total precision for the low, therapeutic, and high clozapine plasma samples was 10.0, 2.6, and 2.0%, respectively. Analytical accuracy was evaluated by comparing quantitative results with those obtained from a reference laboratory. Those samples containing therapeutic or high concentrations agreed within 3%; the sample containing a subtherapeutic concentration differed by 11.9%. The limit of quantitation was determined to be 35 ng/mL, and the upper limit of linearity was 3000 ng/mL. No significant interferences were detected after testing more than two dozen drugs and metabolites.