Gas Chromatographic Procedure Research Articles

Determination of dihydroartemisinic acid in Artemisia annua L. by gas chromatography with flame ionization detection.

Dihydroartemisinic acid (DHAA) is the direct precursor to artemisinin, an effective anti-malaria compound from Artemisia annua L. (A. annua), and it can be transformed to artemisinin without the catalysis of enzyme. A rapid and sensitive analysis of DHAA in A. annua is needed to screen excellent plant resources aimed to improve artemisinin production. In order to develop a rapid and sensitive determination method for DHAA in plant, the extraction and analysis conditions were extensively investigated in the present work. As a result, extraction of powdered A. annua leaves at 55°C for 50 min with chloroform resulted in the highest yield of DHAA, with a recovery of >98%. The precision of this gas chromatographic procedure ranged from 1.22 to 2.94% for intra-day and from 1.69 to 4.31% for inter-day, respectively. The accuracy was 99.55-103.02% for intra-day and 98.86-99.98% for inter-day, respectively. The measured LOQ and LOD values of the proposed method reached 5.00 and 2.00 μg/mL, respectively. Validation indicated the method was robust, quick, sensitive and adequate for DHAA analysis.

Levels of Polycyclic Aromatic Hydrocarbons in Some Organs of Tilapia species from New Calabar River, Niger Delta, Nigeria

The issues of haphazard discharge of polycyclic aromatic hydrocarbons (PAHS) into aquatic environment and its adverse impact on aquatic lives have attracted wide attentions in recent times. This study therefore examined the concentrations of PAHs in some organs (muscle, gill and brain) of Tilapia species (T.guineensis and T.zilli), which are the dominant fish consumed and marketed in Bille community Niger Delta, Nigeria. Samples of the fish were collected from the effluent impacted and control areas. The samples were prepared and levels of PAHs in the organs analyzed using gas chromatography and mass spectrophotometry (GC/MC) analytical procedures. The total PAHs levels determined from the muscle, gill and brain of T. guineensis were 0.13, 0.022 and 0.005 mg/kg, respectively. The control value were muscle (0.0005mg/kg), gill (0.0008mg/kg) and brain (0.0009 mg/kg). Similarly, the organs of T. Zilli had total PAHs values of 0.021, 0.077 and 0.008 mg/kg for the muscle, gill and brain in that order, while the values from the control samples were 0.0006, 0.0006 and 0.0007 mg/kg representing the muscle, gill and brain, respectively. All the values were above WHO limit of 0.001mg/kg Naphthalene with the highest concentrations of 0.064 mg/kg in thegill, and also posed the greatest danger to aquatic lives and humans.

Determination of Nutritional and Cyclopropenoid Fatty Acids in Cottonseed by a Single GC Analysis

AbstractHistorically, a complete analysis of cottonseed fatty acids required two separate analyses: gas chromatography (GC) for nutritional fatty acids and a separate analysis for cyclopropenoid fatty acids (CPFA). Using base esterification and optimized GC conditions, the method presented combines both analyses into a single GC procedure that improves analytical processes and streamlines workflow. While there were challenges, the resolution of critical pairs malvalic/stearic and dihydrosterculic/alpha linolenic methyl esters were adequately separated, allowing for accurate quantitation. Single lab reproducibility measurements (RSD) for major nutritional fatty acids ranged from 0.7 to 2.0 %. For CPFA the RSD ranged from 1.1 to 5.4 %, with the higher variability seen in the extracted cottonseed. In oils, the precision was similar between nutritional fatty acids and CPFA at equivalent concentrations, indicating the variation comes from the extraction process. Average spiked recovery results ranged from 93.3 to 106.5 % for selected fatty acids. In addition, complete fatty acid profile results compare favorably with other methodologies and historical data, demonstrating that it is possible to combine two legacy methods into one.

Determination of N-nitrosamines by automated dispersive liquid-liquid microextraction integrated with gas chromatography and mass spectrometry.

An automated dispersive liquid-liquid microextraction integrated with gas chromatography and mass spectrometric procedure was developed for the determination of three N-nitrosamines (N-nitroso-di-n-propylamine, N-nitrosopiperidine, and N-nitroso di-n-butylamine) in water samples. Response surface methodology was employed to optimize relevant extraction parameters including extraction time, dispersive solvent volume, water sample pH, sodium chloride concentration, and agitation (stirring) speed. The optimal dispersive liquid-liquid microextraction conditions were 28 min of extraction time, 33 μL of methanol as dispersive solvent, 722 rotations per minute of agitation speed, 23% w/v sodium chloride concentration, and pH of 10.5. Under these conditions, good linearity for the analytes in the range from 0.1 to 100 μg/L with coefficients of determination (r(2) ) from 0.988 to 0.998 were obtained. The limits of detection based on a signal-to-noise ratio of 3 were between 5.7 and 124 ng/L with corresponding relative standard deviations from 3.4 to 5.9% (n = 4). The relative recoveries of N-nitroso-di-n-propylamine, N-nitrosopiperidine, and N-nitroso di-n-butylamine from spiked groundwater and tap water samples at concentrations of 2 μg/L of each analyte (mean ± standard deviation, n = 3) were (93.9 ± 8.7), (90.6 ± 10.7), and (103.7 ± 8.0)%, respectively. The method was applied to determine the N-nitrosamines in water samples of different complexities, such as tap water, and groundwater, before and after treatment, in a local water treatment plant.

Physico-chemical Characteristics and Fatty Acids Composition of Some Selected Nigerian Vegetable Oils for Quenching Medium

Four vegetable oils (cotton seed oil, palm kernel oil, neem seed oil and palm oil) were characterized with respect to their physicochemical properties and fatty acids profiles with the aim of investigating their suitability as quenching media for medium ca rbon steels. The physicochemical properties were determined by using appropriate ASTM methods. The fatty acid ester compositions were determined by a gas chromatographic analysis procedure. The results obtained showed that the different vegetable oils exhi bited different viscosity and viscosity - temperature behaviour corresponding to their varying molecular structures and level of saturation. The following values were obtained for the various physicochemical parameters measured in cotton seed oil, palm kerne l oil, neem seed oil and palm oil: viscosity value at 40o C were (34.8, 41.69, 32.41 and 39.7) cSt; viscosity value at 100 °C were (6.9, 8.94, 7.89 and 8.2) cSt; the Iodine values were (115.09,

Simultaneous Quantitation of FFA, MAG, DAG, and TAG in Enzymatically Modified Vegetable Oils and Fats

A novel and easy-to-implement high temperature gas chromatographic procedure for the simultaneous quantitation of free fatty acids (FFA), monoacylglycerols (MAG), diacylglycerols (DAG), and triacylglycerols (TAG) for products arising from fats and oils modification processes has been developed. The method involves silylation in the presence of pyridine at room temperature, standard injection system, and FID detection. Species were separated by carbon number and degree of unsaturation; thus, a total of 53 individual compounds could be quantified. An identification plot for unavailable triacylglycerol standard species relating relative retention time with the number of double bonds was built. Calibration curves for the quantitation of by-products (FFA, MAG, and DAG) and a calibration surface for TAG were constructed using standard solutions. Multiple internal standards were used, achieving good repeatability. The method was tested over a wide range of fatty acid unsaturation level (0 to 3 double bonds) and chain length (C14 to C18). The results achieved in real samples were in agreement with those obtained by fatty acid methyl esters (FAME) analysis and HPLC-RI. The method developed is a rapid and reliable technique to quantify FFA, MAG, DAG, and TAG in substrates and products of modification, ideal to monitor the degree of conversion in fats and oils enzymatic esterification, among others.

Application of gas chromatography analysis to quality control of residual organic solvents in clopidogrel bisulphate

A direct-injection, split-mode capillary gas chromatographic procedure with a flame ionization detection is developed for the analysis of eight solvents used in the synthesis and purification of an anti-thrombotic drug clopidogrel bisulphate. The solvents analyzed were methanol, acetone, dichloromethane (DCM), 2-butanol, cyclohexane, toluene, acetic acid and N, N-dimethyl formamide (DMF). In addition, as a result of dehydration of 2-butanol during drying process, in clopidogrel bisulphate samples, significant amounts of 2-butanol dehydration products (1-butene, cis and trans isomers of 2-butene, 2,2'-oxydibutane and 1-(1-methylpropoxy)butane) may be detected. The content of each of these volatile products can be evaluated using the same gas-chromatographic method, with quantification based on the response factor established for the chromatographic peak of 2-butanol. For each solvent used in the process of clopidogrel bisulphate preparation, the procedure is validated for selectivity, linearity, recovery, precision, robustness, quantitation limit, and detection limit. All eight solvents plus five 2-butanol degradation products are fully separated. System suitability test is validated, and requirements are set. Based on a large number of result sets, retrospectively, from many different batches analyzed, conclusions were made about process variations and reliability and a lack of consistency was identified in the quality of the active substance from a particular producer source. Multivariate analysis was used as statistical technique to classify samples. From the analyzed set of 11 solvents, 6 of them were preselected based upon their occurrence in the samples and both Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) were performed.

Phytase activity of fungi from oil polluted soils and their ability to degrade bonnylight crude oil.

Fungi were isolated from contaminated soil samples taken from three selected automobile workshops, screened for phytase activities and biodegradative abilities. Physicochemical and total petroleum hydrocarbon analyses were carried using standard chemical and gas chromatography procedures, respectively. There was significant increase (at P≤0.05) in the potassium, sodium, calcium, magnesium, pH and organic matter of all contaminated soil samples. The fungi isolated were Aspergillus niger, Aspergillus saprophyticus, Aspergillus fumigatus, Aspergillus flavus, Trichoderma viride, Penicillium italicum, Articulospora inflata and Neurospora crassa . Of all the fungal isolates, A. flavus had the maximum phytase activity at the 48 h of incubation while N. crassa produced the least phytase activity at all the hour of incubation. Phytase activity of A. flavus and A. saprophyticus were found to be most active at pH 5.0 and 50°C. A. niger had the highest degrading ability on crude oil and spent engine oil at all days of incubation while N. crassa had the least degrading ability on crude and spent engine oil. The high total petroleum hydrocarbon (TPH) concentration in contaminated soil may be as a result of consistent exposure of the soil to spent engine oil which could make the soil conditions unsatisfactory for microbial growth. Keywords : Fungi, biodegradation, bonny light crude oil, phytase African Journal of Biotechnology Vol. 12(36), pp. 5540-5548

Elevated Carbon Monoxide in the Exhaled Breath of Mice during a Systemic Bacterial Infection

Blood is the specimen of choice for most laboratory tests for diagnosis and disease monitoring. Sampling exhaled breath is a noninvasive alternative to phlebotomy and has the potential for real-time monitoring at the bedside. Improved instrumentation has advanced breath analysis for several gaseous compounds from humans. However, application to small animal models of diseases and physiology has been limited. To extend breath analysis to mice, we crafted a means for collecting nose-only breath samples from groups and individual animals who were awake. Samples were subjected to gas chromatography and mass spectrometry procedures developed for highly sensitive analysis of trace volatile organic compounds (VOCs) in the atmosphere. We evaluated the system with experimental systemic infections of severe combined immunodeficiency Mus musculus with the bacterium Borrelia hermsii. Infected mice developed bacterial densities of ∼107 per ml of blood by day 4 or 5 and in comparison to uninfected controls had hepatosplenomegaly and elevations of both inflammatory and anti-inflammatory cytokines. While 12 samples from individual infected mice on days 4 and 5 and 6 samples from uninfected mice did not significantly differ for 72 different VOCs, carbon monoxide (CO) was elevated in samples from infected mice, with a mean (95% confidence limits) effect size of 4.2 (2.8–5.6), when differences in CO2 in the breath were taken into account. Normalized CO values declined to the uninfected range after one day of treatment with the antibiotic ceftriaxone. Strongly correlated with CO in the breath were levels of heme oxygenase-1 protein in serum and HMOX1 transcripts in whole blood. These results (i) provide further evidence of the informativeness of CO concentration in the exhaled breath during systemic infection and inflammation, and (ii) encourage evaluation of this noninvasive analytic approach in other various other rodent models of infection and for utility in clinical management.

GC Determination of Famotidine, Ranitidine, Cimetidine, and Metformin in Pharmaceutical Preparations and Serum Using Methylglyoxal as Derivatizing Reagent

A capillary gas chromatography (GC) procedure has been developed for the determination of four pharmaceutical preparations (famotidine, ranitidine, cimetidine, and metformin) after precolumn derivatization with methylglyoxal (MGo). GC was carried out using an HP-5 column (30 m × 0.32 mm id) at an initial column temperature of 90 °C for 2 min, followed by heating rate of 25 °C min−1 up to 265 °C. Nitrogen flow rate was 2.5 mL min−1 with split ratio 10:1. A linear calibration curve was obtained within 50–1,000 ng mL−1 and the limit of detection (LOD) was within 17–25 ng mL−1. The derivatization, GC elution, and separation were repeatable in terms of retention time and peak height/peak area with relative standard deviation within ±4.6 %. The procedure was applied to the determination of the drugs in pharmaceutical preparations and the sera of volunteers who were given oral doses of the drugs. The results of the analysis agreed with the labeled values of the pharmaceutical preparations and were 147–4,903 ng mL−1 in serum with an RSD within 1.0–4.2 %, after ingestion of a single dose of 40–500 mg of active ingredient in a tablet.

A novel microextraction by packed sorbent–gas chromatography procedure for the simultaneous analysis of antiepileptic drugs in human plasma and urine

A simple, accurate, and sensitive microextraction by packed sorbent-gas chromatography-mass spectrometry method has been developed for the simultaneous quantification of four antiepileptic drugs; oxcarbazepine, carbamazepine, phenytoin, and alprazolam in human plasma and urine as a tool for drug monitoring. Caffeine was used as internal standards for the electron ionization mode. An original pretreatment procedure on biological samples, based on microextraction in packed syringe using C(18) as packing material gave high extraction yields (69.92-99.38%), satisfactory precision (RSD < 4.7%) and good selectivity. Linearity was found in the 0.1-500 ng/mL range for these drugs with limits of detection (LODs) between 0.0018 and 0.0036 ng/mL. Therefore, the method has been found to be suitable for the therapeutic drug monitoring of patients treated with oxcarbazepine, carbamazepine, phenytoin, and alprazolam. After validation, the method was successfully applied to some plasma samples from patients undergoing therapy with one or more of these drugs. A comparison of the detection limit with similar methods indicates high sensitivity of the present method over the earlier reported methods. The present method is applied for the analysis of these drugs in the real urine and plasma samples of the epileptic patients.

A Quick, Optimized Method for Routine Analysis of Essential and Trans-Octadecenoic Acids in Edible Fats and Oils by GLC

A gas chromatography procedure using a 30-m capillary column (VF-23ms) has been optimized for quick analysis (run time less than 20 min). The method is suitable for routine analysis of the fatty acid composition of edible fat and oil samples (milk, fish, vegetal and synthetic origin). The results were comparable with those obtained with a 100-m-long CP-Sil 88 column (run times between 60 and more than 100 min) in the analysis of geometric and positional isomers of polyunsaturated fatty acids. The achieved resolution of compounds from 4 to 26 carbon atoms with 0-6 double bonds, as omega-3 and omega-6 fatty acids, major trans-octadecenoic isomers and conjugated linoleic acid isomers, was higher than those reported in other proposed and reference methods for similar samples using short-length columns. The response factors obtained from the fatty acid composition of reference milk fat exhibited high feasibility and the inter-assay (VF23ms versus CP-Sil 88) and intra-assays based on relative standard deviation showed good accuracy, because they were lower than 10%.

Direct measurement of part-per-billion levels of dimethyl sulfoxide in water by gas chromatography with stacked injection and chemiluminescence detection

Dimethyl sulfoxide (DMSO) is a chemical of industrial significance with many important applications. DMSO is used as an industrial solvent, in drug delivery and healthcare applications, among others. Analysis of DMSO in water typically involves extensive sample preparation, enrichment, and derivatization to improve solute detectability. A novel gas chromatographic procedure has been developed for the direct measurement of trace levels of DMSO in an aqueous matrix, such as potable water. The technology utilizes stacked injection techniques for in-column solute enrichment, a precolumn to enhance solute focusing effects, and sulfur chemiluminescence detection for matrix suppression and sensitivity. A detection limit of 2 parts per billion (ppb) (v/v) of DMSO in water was attained. Relative precision of less than 7% at the concentration of 10 ppb (v/v) of DMSO was demonstrated. A correlation coefficient of 0.9988 was obtained over a range of 2 ppb (v/v) to 100 ppb (v/v). No detectable carry-over was found at the 5 ppb (v/v) level whereas less than 4% carry-over was observed at the 100 ppb (v/v) level. Various sample storage media including glass, polyethylene, and polycarbonate were also studied to minimize solute loss. Recoveries greater than 84% were achieved with all storage media tested. The method was found to be reliable and simple to implement.

Gas-chromatographic determination of impurities of organic and chlorinated organic compounds and carbon monoxide and dioxide in high-purity hydrogen chloride

A gas-chromatographic procedure was developed for determining impurities (CH4, C2H6, C3H8, C4H10, iso-C4H10, C5H12, iso-C5H12, neo-C5H12, CH3Cl, C2H5Cl, CH2Cl2, CHCl3, CO, and CO2) in hydrogen chloride using two columns and a column switching technique in an isothermal mode with a flame ionization detector; the detection limits were 0.01–0.1 ppm. The matrix was separated in a precolumn packed with urea. CO and CO2 were determined by reaction gas chromatography with their conversion into methane.

A fast ethanol assay to detect seed deterioration

AbstractThe most common way to test seed quality is to use a simple and reliable but time- and space-consuming germination test. In this paper we present a fast and simple method to analyse cabbage seed deterioration by measuring ethanol production from partially imbibed seeds. The method uses a modified breath analyser and is simple compared to gas chromatographic or enzymatic procedures. A modified method using elevated temperatures (40°C instead of 20°C) shortened the assay time and improved its sensitivity. The analysis showed an inverse correlation between ethanol production and seed quality (e.g. the final percentages or speed of germination and the number of normal seedlings). The increase in ethanol production was observed when cabbage seeds were deteriorated by storage under ambient conditions or hot water treatments, both of which reduced the number of normal seedlings. Premature seeds produced more ethanol upon imbibition than mature seeds. Ethanol production occurred simultaneously with oxygen consumption, indicating that lack of oxygen is not the major trigger for ethanol production.

Gas chromatographic analysis of acetylsalicylic acid, phenacetin, caffeine, and codeine in APC and codeine tablets

Abstract All active ingredients in APC and codeine tablets are determined by gas chromatographic procedures after separation of acetylsalicylic and phenacetin from caffeine and codeine.

Identification and quantitative determination of some metabolites of methadone, isomethadone and normethadone.

Abstract Isomethadone and normethadone are metabolized by microsomal preparations of guinea-pig liver to yield 2-ethyl-1,4-dimethyl-3,3-diphenyl-1-pyrroline and 2-ethyl-1-methyl-3,3-diphenyl-1-pyrroline respectively. The structures of the pyrrolines were established (by comparison with the pyrroline derived from methadone) by thin-layer chromatography and by infrared and nuclear magnetic resonance spectral data. Methadone, isomethadone and normethadone are also metabolized to the corresponding N-oxides. A gas chromatographic procedure for the quantitative determination of unchanged drugs, cyclic metabolites and N-oxides of methadone, isomethadone and normethadone in microsomal homogenates is described. The N-oxides were reduced before analysis.

A fast and accurate method for the determination of total and soluble fluorine in toothpaste using high-resolution graphite furnace molecular absorption spectrometry and its comparison with established techniques

A fast and reliable method has been developed for the determination of total and soluble fluorine in toothpaste, important quality control parameters in dentifrices. The method is based on the molecular absorption of gallium mono-fluoride, GaF, using a commercially available high-resolution continuum source atomic absorption spectrometer. Transversely heated platform tubes with zirconium as permanent chemical modifier were used throughout. Before each sample injection, a palladium and zirconium modifier solution and a gallium reagent were deposited onto the graphite platform and thermally pretreated to transform them into their active forms. The samples were only diluted and introduced directly into the graphite tube together with additional gallium reagent. Under these conditions the fluoride was stable up to a pyrolysis temperature of 550 °C, and the optimum vaporization (molecule formation) temperature was 1550 °C. The GaF molecular absorption was measured at 211.248 nm, and the limits of detection and quantification were 5.2 pg and 17 pg, respectively, corresponding to a limit of quantification of about 30 μg g −1 (ppm) F in the original toothpaste. The proposed method was used for the determination of total and soluble fluorine content in toothpaste samples from different manufactures. The samples contained different ionic fluoride species and sodium monofluorophosphate (MFP) with covalently bonded fluorine. The results for total fluorine were compared with those obtained with a modified conventional headspace gas chromatographic procedure. Accuracy and precision of the two procedures were comparable, but the proposed procedure was much less labor-intensive, and about five times faster than the latter one.

Monitoring light hydrocarbons in Brazilian coal mines and in confined coal samples

Abstract Monitoring light hydrocarbons (LHCs) in coal mines, particularly methane, is important not only because of their implications for global climate change but also for economic and safety reasons. Furthermore, the identification and quantification of LHCs in coal mine air samples and desorbed from confined coal may contribute to a better understanding of coal seam characteristics. The paucity of information about the levels of methane in Brazilian underground coal mines can be attributed to their difficult access and a lack of adequate procedures for correct gas sampling. The aim of this study is to optimize and apply standard gas chromatography procedures to determine LHC levels in the air of coal mines and in confined coal from five mines under operation, three underground (A, B, C) and two surface (D, E) mines, in southern Brazil. The results indicate methane (C1) levels varying from 3 ppm to 27% in the atmosphere of the underground mines. Mine A presented high levels of all LHCs analyzed (C1 to C5), while only C1 and C2 were detected in mine B, and hydrocarbons ranging from C1 to C4 were found in mine C. On the other hand, surface mines presented narrow concentration range for C1 (3 ppm to 470 ppm) and C2–C3, with higher levels observed for puncture explosive points. Among LHCs, methane is desorbed in higher concentrations from confined coals and the presence of C2 was detected in all samples while C3–C5 were only observed in coals from underground mines. These data are consistent with those obtained from the air gas samples collected in the mines under study. Geological events such as faulting and intrusions can accelerate the release of gas or the trapping of large amounts of previously released methane. The LHC emissions from coal mines were found to be highly variable, indicating the need for a comprehensive survey of Brazilian coal mine emissions.

Sensitive headspace gas chromatography analysis of free and conjugated 1-methoxy-2-propanol in urine

Glycol ethers still continue to be a workplace hazard due to their important use on an industrial scale. Currently, chronic occupational exposures to low levels of xenobiotics become increasingly relevant. Thus, sensitive analytical methods for detecting biomarkers of exposure are of interest in the field of occupational exposure assessment. 1-Methoxy-2-propanol (1M2P) is one of the dominant glycol ethers and the unmetabolized urinary fraction has been identified to be a good biological indicator of exposure. An existing analytical method including a solid-phase extraction and derivatization before GC/FID analysis is available but presents some disadvantages. We present here an alternative method for the determination of urinary 1M2P based on the headspace gas chromatography technique. We determined the 1M2P values by the direct headspace method for 47 samples that had previously been assayed by the solid-phase extraction and derivatization gas chromatography procedure. An inter-method comparison based on a Bland-Altman analysis showed that both techniques can be used interchangeably. The alternative method showed a tenfold lower limit of detection (0.1 mg/L) as well as good accuracy and precision which were determined by several urinary 1M2P analyses carried out on a series of urine samples obtained from a human volunteer study. The within- and between-run precisions were generally about 10%, which corresponds to the usual injection variability. We observed that the differences between the results obtained with both methods are not clinically relevant in comparison to the current biological exposure index of urinary 1M2P. Accordingly, the headspace gas chromatography technique turned out to be a more sensitive, accurate, and simple method for the determination of urinary 1M2P.