Capillary Column Gas Research Articles

Impact of a pressure drop on a monolithic capillary column on the efficiency and separation ability of the column

The impact of inlet and outlet column pressures on column separation properties was investigated for monolithic capillary column in gas chromatography. It was demonstrated that the classical Van Deemter equation does not allow us to make a clear choice of the optimal separation conditions. More relevant data can be obtained from the dependence of the height equivalent to a theoretical plate (HETP) on the inlet and outlet column pressures. The dependence ensures that the minimum HETP value can be achieved at high values of inlet and outlet column pressures, but the ratio of the pressures must approach 1. The efficiency of the column under these optimal conditions can exceed by 25–35% the column efficiency under the optimal conditions found using the classical Van Deemter plot. It was shown that a decrease in inlet and outlet column pressures even at a relative pressure close to 1 leads to an increase in HETP and the loss of column separation ability.

High temperature and highly selective stationary phases of ionic liquid bonded polysiloxanes for gas chromatography

Due to the special performance of “dual nature” and synthetic flexibility, ionic liquids (ILs) have been an attractive research subject of stationary phases for gas chromatography (GC). In this work, a novel ionic liquid (IL) bonded polysiloxane ([PSOMIM][NTf 2]) with anion of bis-trifluoromethanesulfonylimide (NTf 2 −) was synthesized, and another one with chloride anion ([PSOMIM][Cl]) was also prepared for the purpose of comparison. The thermo-stability of the product was evaluated by thermogravimetric (TG) test and the result indicated that [PSOMIM][NTf 2] did not decompose slightly until 380 °C. Then the solvation behaviors of the ILs were characterized using solvation parameter model. Subsequently, [PSOMIM][NTf 2] and [PSOMIM][Cl] were used as stationary phases to prepare capillary columns for GC, respectively. The column efficiency of [PSOMIM][NTf 2] column was 4776 plates/m ( k = 3.64 ± 0.08, naphthalene), and that of the other one was 3170 plates/m ( k = 2.84 ± 0.11, naphthalene). The selectivity of the novel stationary phases for analytes, including Grob reagent, aromatic positional isomers was further evaluated. Furthermore, the chromatograms of n-alkanes and polycyclic aromatic hydrocarbons (PAHs) on [PSOMIM][NTf 2] column were compared with that on [PSOMIM][Cl] column. [PSOMIM][NTf 2] stationary phase also exerted good selectivity for fatty acid methyl esters (FAMEs), polychlorinated biphenyls (PCBs) and aromatic amines.

A new procedure for the determination of distillation temperature distribution of high-boiling petroleum products and fractions

The distribution of distillation temperatures of liquid and semi-fluid products, including petroleum fractions and products, is an important process and practical parameter. It provides information on properties of crude oil and content of particular fractions, classified on the basis of their boiling points, as well as the optimum conditions of atmospheric or vacuum distillation. At present, the distribution of distillation temperatures is often investigated by simulated distillation (SIMDIS) using capillary gas chromatography (CGC) with a short capillary column with polydimethylsiloxane as the stationary phase. This paper presents the results of investigations on the possibility of replacing currently used CGC columns for SIMDIS with a deactivated fused silica capillary tube without any stationary phase. The SIMDIS technique making use of such an empty fused silica column allows a considerable lowering of elution temperature of the analytes, which results in a decrease of the final oven temperature while ensuring a complete separation of the mixture. This eliminates the possibility of decomposition of less thermally stable mixture components and bleeding of the stationary phase which would result in an increase of the detector signal. It also improves the stability of the baseline, which is especially important in the determination of the end point of elution, which is the basis for finding the final temperature of distillation. This is the key parameter for the safety process of hydrocracking, where an excessively high final temperature of distillation of a batch can result in serious damage to an expensive catalyst bed. This paper compares the distribution of distillation temperatures of the fraction from vacuum distillation of petroleum obtained using SIMDIS with that obtained by the proposed procedure. A good agreement between the two procedures was observed. In addition, typical values of elution temperatures of n-paraffin standards obtained by the two procedures were compared. Finally, the agreement between boiling points of polar compounds determined from their retention times and actual boiling points was investigated.

Separation characteristics of fatty acid methyl esters using SLB-IL111, a new ionic liquid coated capillary gas chromatographic column

The ionic liquid SLB-IL111 column, available from Supelco Inc., is a novel fused capillary gas chromatography (GC) column capable of providing enhanced separations of fatty acid methyl esters (FAMEs) compared to the highly polar cyanopropyl siloxane columns currently recommended for the separation of cis- and trans isomers of fatty acids (FAs), and marketed as SP-2560 and CP-Sil 88. The SLB-IL111 column was operated isothermal at 168°C, with hydrogen as carrier gas at 1.0mL/min, and the elution profile was characterized using authentic GC standards and synthetic mono-unsaturated fatty acids (MUFAs) and conjugated linoleic acid (CLA) isomers as test mixtures. The SLB-IL111 column provided an improved separation of cis- and trans-18:1 and cis/trans CLA isomers. This is the first direct GC separation of c9,t11- from t7,c9-CLA, and t15-18:1 from c9-18:1, both of which previously required complimentary techniques for their analysis using cyanopropyl siloxane columns. The SLB-IL111 column also provided partial resolution of t13/t14-18:1, c8- from c6/c7-18:1, and for several t,t-CLA isomer pairs. This column also provided elution profiles of the geometric and positional isomers of the 16:1, 20:1 and 18:3 FAMEs that were complementary to those obtained using the cyanopropyl siloxane columns. However, on the SLB-IL111 column the saturated FAs eluted between the cis- and trans MUFAs unlike cyanopropyl siloxane columns that gave a clear separation of most saturated FAs. These differences in elution pattern can be exploited to obtain a more complete analysis of complex lipid mixtures present in ruminant fats.

Characterization of Brazilian oil shale byproducts planned for use as soil conditioners for food and agro-energy production

The Brazilian oil shale byproducts resulting from the Petrosix pyrolysis (retortage) process were submitted to a set of analytical techniques to evaluate their possible use as agricultural soil conditioners. Liquid dichloromethane extracts from the solid samples were analyzed using capillary column gas chromatography–mass spectrometry. The results showed that of the 16 PAHs designated by the U.S. EPA as priority pollutants, only phenanthrene, fluorene and naphthalene, present in the retorted oil shale sample taken from inside storage piles; benzo[k]fluoranthene, present in the dolomite limestone layer between the two layers of oil shale in the mine structure; and naphthalene, present in powdered raw oil shale, were above the limits established by the EPA. The solid Brazilian oil shale byproduct samples were also analyzed by X-ray diffractometry (XRD), diffuse reflectance ultraviolet–visible spectroscopy (DRUV–VIS), X-ray fluorescence spectroscopy (XRF) and electron paramagnetic resonance (EPR) spectroscopy. The XRD analysis showed that the pyrolysis process produces a “weathering” transformation, for example with the appearance of kaolinite diffraction lines in the retorted samples. The DRUV–VIS and XRF spectroscopy results indicated iron oxide goethite interactions with the PAHs present in the solid samples studied. The EPR spectroscopy showed that the samples row oil shale (g=2.0044) and the powder oil shale (g=2.0035), before the dichloromethane extraction, presented organic free radical signals associated with oxygen atoms. The other Brazilian oil shale byproduct samples, before and after the dichloromethane extraction, showed organic free radical signals associated with carbon atoms (g=2.0022–2.0031).

Regional differences of the mouse brain in response to an α-linolenic acid-restricted diet: Neurotrophin content and protein kinase activity

Aims The purpose of this study was to determine a relatively short-term effect of feeding an α-linolenic acid (ALA, n-3)-restricted, linoleic acid (LA, n-6)-adequate diet on neurotrophin contents and protein kinase activities in brain regions of the mouse. Main methods After feeding mice a safflower oil (SAF) diet (ALA-restricted, LA-adequate) or perilla oil (PER) diet (containing adequate amounts of ALA and LA) for 4 weeks from weaning, the fatty acid compositions of brain regions were analyzed by capillary column gas–liquid chromatography, nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) contents were measured using enzyme-linked immunosorbent assay. Key findings The striatum and hippocampus, but not the cerebral cortex, from the SAF group, contained a smaller amount of docosahexaenoic acid (DHA, 22:6n-3) than those from the PER group. The NGF contents in these brain regions were not different between the two dietary groups. However, the striatal BDNF content of the SAF group was significantly lower than that of the PER group. Protein kinase A, protein kinase C, and p44/42 mitogen-activated protein kinase (p44/42 MAPK) activities in brain regions showed no significant difference between the two dietary groups. However, the striatal p38 MAPK activity was significantly lower in the SAF group than in the PER group. No such differences were observed in the hippocampus or the cerebral cortex. Significance A relatively short-term feeding of an α-linolenic acid-restricted, linoleic acid-adequate diet was found to lower the DHA content, BDNF content and p38 MAPK activity in the mouse striatum.

Porous structure of the monolithic sorbent and separation properties of monolithic capillary columns in gas and liquid chromatography

Macroporous polymer based on polydivinylbenzene was used for the preparation of monolithic capillary columns with the diameter from 0.01 to 0.53 mm for separations by gas and liquid chromatography. The separation properties of the columns were studied by analysis of model systems of aromatic (in liquid chromatography) and light (in gas chromatography) hydrocarbons. The permeability was determined and the C parameter of the Van-Deemter equation was found for each column. The permeability of the majority of columns determined by gas chromatography is independent of the column diameter. The permeability of the same columns in liquid chromatography is also almost constant for the columns 0.53–0.1 mm in diameter; however, the permeability decreases sharply on going to columns of smaller diameter. In gas chromatography the value of the C parameter reflecting the effect of the mass transfer of the sorbate between the mobile and stationary phases on the smearing of a chromatographic peak in the column approximately the same for all columns. In liquid chromatography the value of the C coefficient in the Van-Deemter equation for the same capillary columns changes with a change in the column diameter and reaches a minimum for the columns 0.1 mm in diameter. The differences observed for the characteristics of the columns in gas and liquid chromatography are due to different structures of the macroporous monolith formed in columns of different diameter and to the effect of solvation of the monolith by the mobile phase under the conditions of liquid chromatography.

Characterization of Walnut Oils (Juglans regia L.) from Asturias, Spain

AbstractA total of 15 walnut (Juglans regia L.) samples from 15 cultivars from different geographical areas (Villaviciosa, Colunga, Ribadesella, Llanes, Nava, Peñamellera and Sariego) from Asturias, Spain were studied. Samples of virgin walnut oil were obtained from dehusked ground walnuts by extraction at a pressure of 160 kg cm−2 and temperature below 40 °C for 3 min. The oil obtained by pressure was filtered for analysis. Fatty acid, sterol and tocopherol compositions as determined by capillary column gas chromatography (GC) and triacylglycerols composition as determined by high performance liquid chromatography (HPLC) are reported. The overall composition (percentages of husk, oil and moisture) was also determined. The higher percentages of fatty acids, as determined by capillary GC, corresponded to palmitic (6.11 ± 0.06–7.49 ± 0.04%), oleic (11.70 ± 1.10–18.90 ± 1.19%), linoleic (59.81 ± 1.03–64.77 ± 1.25%) and linolenic (11.11 ± 0.05–15.65 ± 1.09%). γ‐Tocopherol was the major component of the total tocopherols in the sample under study (289.01 ± 6.02–676.52 ± 5.98 mg kg−1 oil). β‐Sitosterol was the major sterol found (78.61 ± 1.45–86.50 ± 1.35%) followed by Δ5‐avenasterol (5.54 ± 0.92–13.81 ± 1.06%). The main triacylglycerides were LLL (24.67 ± 1.31–29.20 ± 1.22%), followed by LLLn (14.63 ± 1.01–17.06 ± 1.13%), OLL + PoLO (13.81 ± 1.01–16.14 ± 1.16%) and PLL + LnOO (11.83 ± 1.09–14.10 ± 1.10%).

The use of a simple backflush technology to improve sample throughput and system robustness in routine gas chromatography tandem mass spectrometry analysis of doping control samples

A simple, low cost system for the backflushing of capillary gas chromatography (GC) columns has been investigated and integrated into a method for the detection of anabolic steroids in equine urine. The modification to the method was simple to make and quick to setup and optimize. The use of backflushing technology was found to offer significant benefits in terms of sample throughput and improved system robustness.

Tandem capillary column gas chromatography–mass spectrometric determination of the organophosphonate nerve agent surrogate dimethyl methylphosphonate in gaseous phase

A procedure based on capillary column gas chromatographic-mass spectrometric (GC-MS) confirmation was developed for the verification of the ubiquitous and versatile chemical and nerve agent simulant, dimethyl methyl phosphonate (DMMP; CAS# 756-79-6), from gaseous samples. This method was developed to verify low nanogram DMMP concentrations during testing of a nerve agent detection system. Standard solutions of 1, 5, 10, 50, 100, 500, and 1000ng/ml DMMP in acetonitrile were employed. Through 15 calibration curves using the 5 lowest concentrations, coefficient of determination (r(2)) values showed a mean of 0.998 (0.992-1.000). An additional 15 calibration curves likewise containing 5 concentrations of DMMP spanning 3 orders of magnitude (1, 50, 100, 500, and 1000ng/ml) yielded a mean r(2) of 0.997 (0.991-1.000). Sixty-five nitrogen diluted gaseous samples varying from 1.0 to 10.0microl in volume were analyzed and concentrations of DMMP ranging from 1 to 1000ng/ml were confirmed. An additional 35 vapor samples in UHP N(2) ranging in DMMP concentration from 5.8microg/m(3) to 1.0mg/m(3) were analyzed by increasing sample volume range to between 10.0 and 100microl. For gaseous samples with volumes>1.0microl, the lowest concentration observed was 5.8microg/m(3). The method detection limit (Appendix B of Title 40 CFR, United States) for 1.0microl autoinjected standards in acetonitrile was determined to be 0.331ng/ml. Method precision for 15 independently analyzed standards of 25ng/ml had a relative standard deviation of 1.168. This method demonstrated high linearity across a wide range of concentrations, as well as excellent sensitivity and repeatability, and proved applicable to other lower alkyl-phosphonates.

Urinary steroid profiling in the evaluation of patients with adrenocortical neoplasms.

Background: Adrenocortical tumours are relatively common in childhood. Clinical presentation with an abdominal mass often signifies metastatic disease with poor prognosis. On the other hand, modern imaging techniques have significantly increased the pick up rate of adrenal masses (dubbed ‘incidentalomas’). Endocrine hypersecretion may result in varying degrees of vague symptomatology that may be clinically challenging to adequately evaluate. Objectives: To determine the urinary steroid profiles (by capillary gas chromatography) in a series of patients presenting with adrenocortical masses). Methods: The fifty patients included in this study had an adrenocortical tumour diagnosed on the basis of abdominal ultrasound, CT or at laparatomy. An aliquot of a 24 hours urine collection was analysed by capillary column gas chromatography after enzymatic hydrolysis and derivatization of constituent steroid metabolites. Twenty steroid derivative compounds were identified and quantified. Results: All 23 children (less than 16 years) in this series presented with endocrine symptoms with only 3 additionally presenting with a clinically evident abdominal mass. 11 out of 20 adult patients presented with Cushing’s syndrome, including 5 presenting with a clinically evident abdominal mass. Only one of the 50 patients studied here had a normal urinary steroid profile. The pattern or the amount of overall steroid metabolites excreted was abnormal in all the other patients. There was heterogeneity of urinary steroid profiles in both children (=

Determination of 4-nonylphenol in water samples using 4-(2,6-dimethylhept-3-yl)phenol as new internal standard

A new method for determining the endocrine disrupting substance 4-nonylphenol (technical grade = mixture of isomers, 4-NP) from water samples has been developed by using 4-(2,6-dimethylhept-3-yl)phenol (4- sec-NP) as model compound. This branched monoalkylphenol is shown to serve as internal standard (IS) for the determination of technical 4-nonylphenol. To the best of our knowledge, 4-(2,6-dimethylhept-3-yl)phenol (racemic mixture) is a newly synthesized 4-nonylphenol isomer and has not been described elsewhere. Recoveries have been determined by analyzing spiked water samples from distilled water, river water and wastewater. Following acetylation, the compounds were enriched via solid phase extraction (SPE). Analyses of the compounds were performed by capillary column gas chromatography/mass spectrometry (GC/MS), operating in selected ion-monitoring (SIM) mode. The recovery of technical 4-NP using either the newly prepared 4- sec-NP or 4- n-nonylphenol (4- n-NP) as IS have been compared. 4- sec-NP showed slightly better results. However, in the first series of experiments using wastewater, the yields for the derivatization of the two standard compounds were remarkably different. The yield for derivatization of 4- n-NP was approximately 20%, probably due to the difficult matrix of the wastewater. In contrast, the yield for the derivatization of 4- sec-NP was considerably higher (approximately 63%). This problem can be solved by increasing the concentration of the reagent used for derivatization. For better control of the clean-up process, we recommend application of 4- sec-NP as internal standard, at least in water samples with complex matrices (e.g., high content of hydroxylated compounds).

Investigation of monolithic capillary columns based on ethylene glycol dimethacrylate in gas chromatography

The influence of the conditions of the synthesis of polymer monoliths based on ethylene glycol dimethacrylate on the properties of monolithic capillary columns for gas chromatography was investigated. It was established that the time of polymerization, the temperature of synthesis, and the composition of the polymerization mixture have a strong effect on the dynamic and chromatographic properties of the columns. It was concluded that monolithic capillary columns synthesized under optimum conditions are characterized by a height equivalent to a theoretical plate of 30–40 μm, which is considerably less than that for traditional hollow capillary columns of the same diameter.

Compounds Structurally Related to Dechlorane Plus in Sediment and Biota from Lake Ontario (Canada)

The historical occurrence of Dechlorane Plus (DP) and detection of novel compounds structurally related to DP is described in a dated Lake Ontario sediment core. Our core was collected near the mouth of the Niagara River, which is known to be a major source of DP to the lake. Maximum DP concentrations (920 ng g(-1), dry weight) were observed between 1976 and 1980, the highest reported to date. Following that time, we observed a dramatic decrease in DP concentration which coincided with the enactment of United States federal and state laws to mitigate free release of chemicals into the Niagara River and installation of an industrial wastewater treatment facility. During the course of our research, four new substances structurally related to DP were also identified. These compounds were thought to arise from the Diels-Alder reactions resulting from impurities present in 1,5-cyclooctadiene, a feedstock used in production of DP. To confirm our hypothesis, Diels-Alder reactions were performed on the individual impurities. Using different stationary-phase capillary gas chromatography columns and high-resolution mass spectrometry, we were able to positively identify some of these novel compounds in the core. Interestingly, we also were able to identify a monoadduct compound, formed by addition of 1 mol of hexachlorocyclopentadiene to 2 mol of 1,3-cyclooctadiene, in lake trout. The concentration of this monoadduct was approximately 2 orders of magnitude greater than that of DP, suggesting that it is more bioaccumulative.

Ultra trace analysis of 17 organochlorine pesticides in water samples from the Arctic based on the combination of solid-phase extraction and headspace solid-phase microextraction–gas chromatography-electron-capture detector

Solid-phase extraction (SPE) was combined with headspace solid-phase microextraction (HS-SPME) for the highly effective enrichment of 17 ultra trace organochlorine pesticides in water samples. The target compounds were successfully transferred from water samples to a gas chromatography capillary column by means of four consecutive steps, namely SPE, solvent conversion, HS-SPME, and thermal desorption of the SPME fiber. Parameters, including elution volume and breakthrough volume in the SPE step, temperature in the solvent conversion step, and fiber type, ionic strength, extraction temperature, extraction time, and pH in the SPME step were optimized to improve the performance of the method through either single factor comparative experiment or the orthogonal experimental design approach. After optimization, the method gave high sensitivity with a method detection limit ranging from 0.0018 to 0.027 ng L −1, good repeatability with a relative standard deviation less than 20% ( n = 4) and acceptable recovery with a value mostly exceeding 60%. External standard calibration was employed for the quantification, and a wide linear range (from 0.0010 to 60 ng mL −1) with R 2 values ranging from 0.9988 to 0.9999 were observed. In the end, the method was successfully applied to the Arctic samples, and the results showed that, among all the organochlorine pesticides, hexachlorocyclohexanes (HCHs) were the most predominant in the Arctic surface water body with sum of their concentrations ranging from 0.262 to 3.156 ng L −1.

Contaminant profiles in Southeast Asian immigrants consuming fish from polluted waters in northeastern Wisconsin

Recent immigrants to the USA from Southeast Asia may be at higher risk of exposure to fish-borne contaminants including polychlorinated biphenyls (PCBs), p, p'-dichlorodiphenyldichloroethene (DDE) and methylmercury (MeHg) because of their propensity to engage in subsistence fishing. Exposure to contaminants was assessed in men and women of Hmong descent living in Green Bay, Wisconsin, where the Fox River and lower Green Bay are contaminated with PCBs, and to a lesser extent with mercury. Serum samples from 142 people were analyzed for PCBs and p,p'-DDE by capillary column gas chromatography with electron capture detection (ECD). Whole blood was analyzed for total mercury by cold vapor atomic absorption spectrometry and atomic fluorescence spectroscopy. Lipid-adjusted total PCB concentrations ranged from 8.7 to 3,091ng/g (full range of the data), with a geometric mean of 183.6ng/g (estimated after eliminating one outlier). DDE ranged from 0.3 to 7,083 (full range of the data) with a geometric mean of 449.8ng/g (estimated after eliminating two outliers). Men had higher PCB and DDE concentrations than women. Serum PCB concentrations were significantly correlated with fish consumption (r=0.43, p<0.0001), whereas DDE concentrations were not (r=0.09,p=0.29). Instead, serum DDE was strongly associated with the number of years spent in a Thai refugee camp before immigrating to the USA (r=0.60;p<0.0001). PCB congeners 138, 153, 118 and 180 accounted for a smaller percentage of the total PCBs than has been reported in other fish-eating populations, and several lightly chlorinated congeners were present in relatively large amounts. Mercury exposure was low in this population. In conclusion, Hmong immigrants in northeastern Wisconsin are at risk of elevated PCB exposure from consumption of locally caught fish. The pattern of exposure is somewhat different than patterns in other fish-eating populations, possibly due to use of Aroclor 1242 by the paper industry in this region.

Association of homocysteine, asymmetric dimethylarginine, and nitric oxide with preeclampsia

Endothelial dysfunction underlies the pathogenesis of preeclampsia, but its mechanism has not yet been completely understood. In this study we have aimed to measure homocysteine (Hcy), asymmetric dimethylarginine (ADMA), and nitric oxide (NO) levels as endothelial dysfunction markers in preeclamptic women. Control-case study with 62 preeclamptic patients and 30 controls without pregnancy complications was conducted. Plasma total Hcy, determined by capillary column gas chromatography/mass spectrometry (GC/MS), was correlated with serum ADMA (determined by liquid chromatography/tandem mass spectrometry using (13)C(6)-L: -arginine as the internal standard) and NO (analyzed by GC/MS). There was a highly significant increase in the plasma concentration of homocysteine (P < 0.001) and ADMA (P < 0.001) and a highly significant decrease in the plasma concentration of nitric oxide (P < 0.001) among the preeclamptic patients. The differences were more significant between mild and severe preeclampsia, with and without eclampsia, with and without HELLP (hemolysis, elevated serum level of liver enzymes, and low platelets). In the combined patients and control groups a highly significant positive correlation was found between the plasma concentrations of homocysteine and ADMA (r = 0.853, P < 0.001). In addition, significant negative correlations were detected between the plasma concentrations of nitric oxide and the plasma concentration of homocysteine (r = -0.870, P < 0.001) and ADMA (r = -0.895, P < 0.001). These significant correlations were found to persist, even when they were restricted to the preeclamptic patients. The homocysteine-ADMA-NO may be at least partly responsible for etiology in preeclampsia and could be regarded as markers for the severity of the disease. Therefore, L: -arginine may represent a novel therapy for the treatment of preeclampsia.

Selective retention of explosives and related compounds on gas-chromatographic capillary columns coated with lanthanide(III) β-diketonate polymers

The purpose of this research was to investigate coating capillary columns with lanthanide(III) β-diketonate polymers to provide gas-chromatographic columns with selectivity toward explosives and related compounds. Capillary columns were statically coated with a mixture of a lanthanide(III) β-diketonate polymer, which utilized p-di(4,4,5,5,6,6,6-heptafluoro-1,3-hexanedionyl)benzene (dihed) as a ligand, and SE-30. A novel coating technique was developed that used a methanol-containing azeotrope to provide solubility for both polymers while maintaining a low boiling point compatible with static coating. As based on temperature-programmed retention indices, the experimental columns displayed selective retention of nitroaromatic, nitroalkane, and nitrate ester test probes relative to an appropriate SE-30 control column. Selective retention was more pronounced for strongest Lewis base analyte contained in the test mixture (i.e., cyclohexanone). Relative analyte retention on the La(dihed), Tb(dihed), and Eu(dihed) columns are discussed relative to Lewis acidity and solubility of the polymer in the azeotropic coating solution.

Determination of filbertone in spiked olive oil samples using headspace-programmed temperature vaporization-gas chromatography–mass spectrometry

A sensitive method for the fast analysis of filbertone in spiked olive oil samples is presented. The applicability of a headspace (HS) autosampler in combination with a gas chromatograph (GC) equipped with a programmable temperature vaporizer (PTV) and a mass spectrometric (MS) detector is explored. A modular accelerated column heater (MACH) was used to control the temperature of the capillary gas chromatography column. This module can be heated and cooled very rapidly, shortening total analysis cycle times to a considerable extent. The proposed method does not require any previous analyte extraction, filtration and preconcentration step, as in most methods described to date. Sample preparation is reduced to placing the olive oil sample in the vial. This reduces the analysis time and the experimental errors associated with this step of the analytical process. By using headspace generation, the volatiles of the sample are analysed without interference by the non-volatile matrix, and by using injection in solvent-vent mode at the PTV inlet, most of the compounds that are more volatile than filbertone are purged and the matrix effect is minimised. Use of a liner packed with Tenax-TA allowed the compound of interest to be retained during the venting process. The limits of detection and quantification were as low as 0.27 and 0.83 microg/L, respectively, and precision (measured as the relative standard deviation) was 5.7%. The method was applied to the determination of filbertone in spiked olive oil samples and the results revealed the good accuracy obtained with the method.

Photocatalytic activity of titanium dioxide prepared by a gamma-ray irradiation

The photocatalytic activity of titanium dioxide prepared by a gamma-ray irradiation was investigated. The particles of the prepared TiO 2 were very fine and had a narrow distribution. The particle size of the prepared TiO 2 was in the range 20–100 nm and the average particle size was 61 nm from the particle size analyzer (PSA) result. The remaining ammonia gas after a UV irradiation was measured. Ammonia gas detection and analysis were carried out on a capillary column-gas chromatography (GC) system. The remaining ammonia gas of the prepared sample in a transparent tube after a UV irradiation was decreased owing to the neutralization reaction of the ammonium hydroxide and polyacrylic acid (PAC) and the photocatalytic activity of the nanosized TiO 2 particles.