Packed Column Gas Chromatography Research Articles

Evaluation of thermal adsorption and desorption properties of dioxins on 11 adsorbents

筛选在低温下高效捕集并在一定的高温下可以快速完全脱附二噁英的吸附/脱附材料是二噁英在线热捕集的关键。该研究以1,2,3,4-四氯代二苯并-对-二噁英(1,2,3,4-TCDD)和1,2,3,8,9-五氯代二苯并呋喃(1,2,3,8,9-PCDF)为二噁英模型物,以电子捕获检测器(ECD)作为检测器,利用填充柱气相色谱系统,测定了这两种二噁英单体在11种吸附剂上4~5个温度点下的保留体积,并建立了相应的范特霍夫方程。结果表明,11种吸附剂的线性方程决定系数(R2)均大于0.96。根据范特霍夫方程,预测了吸附剂在120、150、180 ℃时的气固分配系数(KSA)。弗洛里硅土在120、150、180 ℃ 3个温度点下都具有最强的吸附能力,特别是在120 ℃时,1,2,3,4-TCDD、1,2,3,8,9-PCDF在弗洛里硅土上的KSA分别高达1.82×108 m3/g、1.46×1013 m3/g。碳基吸附剂的高分子多孔微球GDX系列的GDX-101、GDX-102、GDX-103、GDX-105、GDX-203在最高耐受温度270 ℃下都可以实现二噁英的热脱附,证实了碳基吸附剂作为二噁英热吸附/脱附的吸附剂的可行性。310 ℃下,在丝光沸石上1,2,3,4-TCDD可实现热脱附,而1,2,3,8,9-PCDF在相同条件下无法实现热脱附,体现了沸石对二噁英同系物的选择性吸附的特性。而硅藻土和蒙脱土对气相中的二噁英几乎没有吸附能力,不适合作为二噁英热捕集的吸附剂。弗洛里硅土、硅胶、氧化铝、GDX-102、GDX-103和GDX-203对1,2,3,4-TCDD、1,2,3,8,9-PCDF都具有很强的吸附能力,因此被初步选为二噁英的候选吸附剂。通过比较120 ℃下和270 ℃下二噁英在这6种吸附剂上的lnKSA,发现弗洛里硅土在两个温度点下的保留体积都是最大的;在侧重低温下二噁英的热捕集性能时,弗洛里硅土是捕集二噁英的最佳吸附剂;而GDX-102是6种吸附剂中lnKSA,270 ℃最小的,在侧重高温下二噁英的热脱附性能时,GDX-102是二噁英热脱附的最佳吸附剂。同时,硅胶、GDX-103和GDX-203的lnKSA,120 ℃和lnKSA,270 ℃与GDX-102相近,也可以作为快速热吸附/脱附的材料。该文通过系统评价1,2,3,4-TCDD和1,2,3,7,8-PCDF在11种吸附剂的热吸附/脱附性能,对简化二噁英的采样和制备过程提供了新的解决思路,为实现二噁英的热捕集提供了技术支撑。

Statistical Analysis for Comparison of the Results Obtained by Capillary Columns and Packed Columns in the Determination of Water Yield in Smoke Condensates Analyzed in Cigarettes for the 24th Asia Collaborative Study

Summary Recently, capillary columns have been widely used in the methodology for the determination of water yields in smoke condensate, even though ISO 10362-1:1999, “Cigarettes - Determination of water in smoke condensates – Part 1: Gas chromatographic method” specifies a packed gas chromatographic column. As a result of a systematic review in 2015, ISO/TC126 decided to revise the standard to include the use of capillary columns. The goal of this study was to confirm the comparability of water yields obtained from capillary column methodology to those yields from packed columns by the statistical analysis of yield data from the 24th Asia Collaborative Study which included 86 datasets submitted by 64 laboratories. After the exclusion of outliers by Cochran’s and Grubbs’ tests, the datasets were classified by GC column type and then mean water yields, and their repeatability and reproducibility were calculated for each type of column. No significant differences were observed in water yields between capillary and packed columns. Repeatability and reproducibility of water yields using capillary column were comparable to those using packed columns as described in ISO 10362-1:1999. From these results, it was confirmed that the capillary columns are an appropriate alternative to packed columns for the gas chromatographic procedure described in ISO 10362-1:1999.

A Mini-System Integrated with Metal-Oxide-Semiconductor Sensor and Micro-Packed Gas Chromatographic Column.

In this work, a mini monitoring system integrated with a microfabricated metal oxide array sensor and a micro packed gas chromatographic (GC) column was developed for monitoring environmental gases. The microfabricated packed GC column with a 1.6 m length was used to separate the environmental gas, and the metal oxide semiconductor (MOS) array sensor, fabricated with nano-sized SnO-SnO2 sensitive materials, was able to effectively detect each component separated by GC column. The results demonstrate that the monitoring system can detect environmental gas with high precision.

Comparison of residual styrene monomer determination of pharmaceutical materials packed with polystyrene using gas chromatography and ultraviolet/visible spectrophotometer

Background: Plastics such as plastic wrapping are an integral part of today’s society. Plastics are made by polymerization of styrene monomers. If the polymerization reaction is not perfect, then there will be unreacted monomer residues. Although styrene is still considered harmless, if there is a metabolic process will form styrene oxide that can cause effects that are carcinogenic. Aims and Objectives: This study aims to determine the residue of pharmaceutical styrene materials packed with polystyrene using gas chromatography (GC) and ultraviolet (UV)/visible spectrophotometers which are usually available in chemical analysis laboratories. Materials and Methods: Orientation of analysis method was performed using latex polystyrene sample. Styrene monomer analysis was performed using a GC and UV/visible spectrophotometer. Then a comparative study was conducted on both methods. Once this method was accepted, it was applied to a polystyrene-containing sample obtained from the market. Styrene was isolated from the sample; then, both methods were tested and compared. Results: Using polystyrene latex sample and varying column temperature, for GC, the optimum condition was obtained at column temperature 110°C, detector temperature 200°C, and temperature of injector 200°C. Using the packing column, we got a repeatability of 96.67%, PRECISION test of 2.81%, 96.49% recovery test, and a detection limit of 0.25 ppm. For the quantitative test of latex polystyrene samples, the average residual content obtained was 0.276%. When using GC with a capillary column, used column DB-17 at 110°C, detector, and injector temperature at 200°C, the average content of styrene residue was 0.278%. When using the spectrophotometer UV/visible, λ maximum at 280.5 nm, the reliability, assay, recovery test, and detection limits were 94.83%, 4.36%, 93.72% and 0.30 ppm, respectively. The residual styrene results obtained with this instrument was an average of 0.271%. Using variance analysis with the fixed model for all three methods (GC with the capillary column, GC with packing column, and spectrophotometer UV/visible) obtained H0 hypothesis was rejected so that it was continued with Duncan test with the result of all three methods could be used for analysis of styrene residue. The result of average analysis for beverage sample with Spectrophotometer UV/visible method was 0.0220%, packed column GC was 0.0221% packing, and capillary column GC of 0.0.223%. For medication samples in each instruments were found 0.0239%, 0.0241%, and 0.0242%, whereas for food samples obtained 0.0236%, 0.0238%, and 0.0239%. Conclusions: A GC method with either a packing column or a capillary column and a spectrophotometer UV/visible could be used to analyze the residual styrene monomer of a polystyrene-grade pharmaceutical sample. The best analysis could use GC with a capillary column. It is recommended to use differential scanning calorimetry and thermogravimetric analysis, if available, as well as infrared spectrophotometer to obtain a cheaper and better method.

2 H/1 H measurements of amphiboles and nominally anhydrous minerals (clinopyroxene, garnet and diamond) using high-temperature continuous flow elemental analyser/pyrolysis/isotope ratio mass spectrometry.

We have used a high-precision, high-efficiency method for the measurement of the 2 H/1 H ratios of hydrous silicates (amphiboles) and nominally anhydrous minerals (NAM) such as clinopyroxene, garnet and diamond, which are usually extremely resistant to pyrolysis. This opens up new fields of investigation to better understand the conditions of formation for deep-Earth minerals. The technique described here involves Isotope Ratio Mass Spectrometry (IRMS) on-line in continuous flow mode with an Elemental Analyser (EA) using "purge and trap" technology rather than separation by conventional packed column gas chromatography (GC). The system is equipped with a special high-temperature furnace reaching 1500°C, with a longer hot zone and improved temperature stability. Emphasis is put on the efficiency of the system to reliably pyrolyse refractory minerals difficult to analyse with other conventional systems. While conventional systems usually fail to generate hydrogen suitable for isotopic analyses, with the technique presented here we were able to measure 2 H/1 H ratios from four diamond samples (δ2 H=-60, -77, -84 and -79‰ V-SMOW; average SD=4.5‰; n=2), three garnet samples (δ2 H from -70 to -63‰), and nine clinopyroxenes (δ2 H from -92 to -58‰) associated with seven amphiboles (δ2 H from -76 to -27‰) from single mantle rock. The possibility of using such a system to reliably measure 2 H/1 H ratios from refractory minerals, which are usually extremely difficult to analyse, offers a new tool of investigation for providing us with unrivaled clues to study the deep interiors of Earth.

A High-Volume Cryosampler and Sample Purification System for Bromine Isotope Studies of Methyl Bromide*

Abstract A system was developed for collecting from the ambient atmosphere the methyl halides CH3Cl and CH3Br in quantities sufficient for chlorine and bromine isotope analysis. The construction and operation of the novel cryogenic collection system (cryosampler) and sample purification system developed for this task are described. This study demonstrates the capability of the cryosampler by quantifying the CH3Cl and CH3Br collected from atmospheric samples and the nonfractionating bromine isotope fingerprint of CH3Br from synthetic air samples of controlled composition. An optimized cryosampler operation time of 4 h at a flow rate of 15 L min−1 is applied to yield the nearly 40 ng required for subsequent δ81Br-CH3Br analyses. The sample purification system is designed around a packed column gas chromatography–quadropole–mass spectrometry (GCqMS) system with three additional cryotraps and backflushing capacity. The system's suitability was tested by observing both the mass recovery and the lack of Δ81Br isotope fractionation induced during sample purification under varying flow rates and loading scenarios. To demonstrate that the entire system samples and dependably delivers CH3Br to the isotope analysis system without inducing isotope fractionation, diluted synthetic air mixtures prepared from standard gases were processed through the entire system, yielding a Δ81Br-CH3Br of +0.03‰ ± 0.10‰ relative to their starting composition. Finally, the combined cryosampler–purification and analysis system was applied to demonstrate the first-ever δ81Br-CH3Br in the ambient atmosphere with two samples collected in the autumn of 2011, yielding −0.08‰ ± 0.43‰ and +1.75‰ ± 0.13‰ versus standard mean ocean bromide for samples collected at a suburban Stockholm, Sweden, site.

Separation of alkanes and aromatic compounds by packed column gas chromatography using functionalized Multi-Walled Carbon Nanotubes as stationary phases

In the present work, we show a novel application of pristine and functionalized Multi-Walled Carbon Nanotubes (MWCNTs) as stationary phase in low-cost packed columns for the gas chromatographic separation of alkanes and aromatic hydrocarbons. The MWCNTs were deeply investigated by means of physical and chemical methods, like thermal analysis, IR and atomic force microscopy, and Inverse Gas Chromatography (IGC) in order to correlate the adsorption process and surface properties with the material purity level and functionalization degree. The derivatization process of the pristine nanotubes was a key factor to achieve a successful separation of both the light n-alkanes (C 3–C 5) and the related isomers (C 4–C 5 branched alkanes). Satisfactory results were similarly obtained in the case of separation of aromatic hydrocarbons (BTX).

Effect of the Amount of Liquid Phase in Packed Column GC on Air Oxidation Product of Methyl Oleate

The analysis or preparative isolation of a specimen by a packed column gas chromatograph is affected by the kind and amount (concentration) of the liquid phase coated on the stationary phase. In particular, compounds having the same or similar molecular weight and similar functional groups are largely affected. Methyl oleate, which is a typical component of fats and oils, produces hydroperoxide by air oxidation as a first step. After that, various oxygenated compounds with a carbon number of 19 are produced. In this study, the effect of the concentration of ethylene glycol succinate polyester (EGS) as the liquid phase was examined for these compounds. The retention time of the hydroxides increased with an increase in the EGS concentration. The effect of the EGS concentration on the retention time decreased when these compounds were trimethyl silylated (TMS). The retention time of epoxides and oxo compounds increased with an increase in the EGS concentration independently of trimethyl silylation. Correction values were required for all quantitation.

Studies on Chromatographic Properties of Perhydroxycucurbit[6]uril as a New Type of Gas Chromatographic Column Packing Material

AbstractPerhydroxycucurbit[6]uril {(HO)12CB[6]} has been used successfully as a stationary phase for packed column gas chromatography for the first time. Perhydroxycucurbit[6]uril stationary phase (PSP) exhibited wide operational temperature, outstanding thermostability and good selectivities to various organic compounds, such as alkanes, aromatic hydrocarbons, alcohols, esters, ketones, amines, etc. It was also found that some positional isomers, such as disubstituted benzenes could be well separated on this column. PSP has excel1ent separation abilities to some complicate samples, for example, commercial toilet water. Some mechanism of the new packing for GC‐separation was preliminarily discussed. It was observed that the partial inclusion complexation of PSP with analytes could improve separation selectivity and column efficiency, instead of complete inclusion. Moreover, PSP exhibited low baseline shift even at dramatically programmed temperature for complicate samples covering a wide boiling point range so as to fast assay.

Columns for gas chromatography: performance and selection

Preface. Acknowledgments. 1 Introduction. 1.1 Evolution of Gas Chromatographic Columns. 1.2 Central Role Played by the Column. 1.3 Justification for Column Selection and Care. 1.4 Literature on Gas Chromatographic Columns. 1.5 Gas Chromatographic Resources on the Internet. References. 2 Packed Column Gas Chromatography. 2.1 Introduction. 2.2 Solid Supports and Adsorbents. Supports for Gas-Liquid Chromatography. Adsorbents for Gas-Solid Chromatography. 2.3 Stationary Phases. Requirements of a Stationary Phase. USP Designation of Stationary Phases. Kovats Retention Index. McReynolds and Rohrschneider Classifications of Stationary Phases. Evaluation of Column Operation. Optimization of Packed Column Separations. 2.4 Column Preparation. Coating Methods. Tubing Materials and Dimensions. Glass Wool Plugs and Column Fittings. Filling the Column. Conditioning the Column and Column Care. 2.5 United States Pharmacopeia and National Formulary Chromatographic Methods. References. 3 Capillary Column Gas Chromatography. 3.1 Introduction. Significance and Impact of Capillary Gas Chromatography. Chronology of Achievements in Capillary Gas Chromatography. Comparison of Packed and Capillary Columns. 3.2 Capillary Column Technology. Capillary Column Materials. Fused Silica and Other Glasses. Extrusion of a Fused-Silica Capillary Column. Aluminum-Clad Fused-Silica Capillary Columns. Fused-Silica-Lined Stainless Steel Capillary Columns. 3.3 Preparation of Fused-Silica Capillary Columns. Silanol Deactivation Procedures. Static Coating of Capillary Columns. Capillary Cages. Test Mixtures for Monitoring Column Performance. Diagnostic Role Played by Components of Test Mixtures. 3.4 Chromatographic Performance of Capillary Columns. Golay Equation Versus the van Deemter Expression. Choice of Carrier Gas. Measurement of Linear Velocity and Flow Rate. Effect of Carrier Gas Viscosity on Linear Velocity. Phase Ratio. Coating Efficiency. 3.5 Stationary-Phase Selection for Capillary Gas Chromatography. Requirements. History. Comparison of Columns from Manufacturers. Polysiloxane Phases. Polyethylene Glycol Phases. Cross-Linked Versus Chemically Bonded Phase. Chemical Bonding. MS-Grade Phases Versus Polysilarylene or Polysilphenylene Phases. Sol-Gel Stationary Phases. Phenylpolycarborane-Siloxane Phases. 3.6 Specialty Columns. EPA Methods. Chiral Stationary Phases. Gas-Solid Adsorption Capillary Columns: PLOT Columns. 3.7 Capillary Column Selection. Practical Considerations of Column Diameter, Film Thickness, and Column Length. Capillary Columns of 0.53mm i.d.: Megabore Columns. Correlation of Column Dimensions and Film Thickness with Parameters in the Fundamental Resolution Equation. Column Selection for Gas Chromatography by Specifications. 3.8 Column Installation and Care. Carrier Gas Purifiers. Ferrule Materials and Fittings. Column Installation. Column Conditioning. Column Bleed. Retention Gap and Guard Columns. Column Fatigue and Regeneration. 3.9 Special Gas Chromatographic Techniques. Simulated Distillation. Multidimensional Gas Chromatography. Computer Modeling of Stationary Phases. References. 4 Column Oven Temperature Control. 4.1 Thermal Performance Variables and Electronic Considerations. 4.2 Advantages of Temperature Programming over Isothermal Operation. 4.3 Oven Temperature Profiles for Programmed-Temperature Gas Chromatography. 4.4 Role of Computer Assistance in Optimizing Separations in Gas Chromatography. DryLab (LC Resources). ProezGC (Restek Corporation). GC-SOS (Chem SW). 4.5 Fast or High-Speed Gas Chromatography. Selectivity Tuning. Resistively Heated Columns and Column Jackets. 4.6 Subambient Oven Temperature Control. References. Selected References. Appendix A: Guide to Selection of Packed Columns. Appendix B: Column Selection. Index.

PCB and DDE at Birth Affect Gene Expression of Sex Steroids in Adult Female Offspring

ISEE-292 Objective: Although banned in the early 1970s, the use of polychlorinated biphenyls (PCBs) and dichlorodiphenyldichloroethylene (DDE), a metabolite of DDT, has resulted in persistent and ubiquitous exposure of large populations, in particular, Michigan fish eaters. The objective was to investigate whether in utero DDE and PCB exposures induces increased gene expression of enzymes and receptors involved in sex steroid metabolism in female offspring of Michigan fish eaters. Material and Methods: Fifty-nine female offspring (average age 37.2 years) from an established cohort of women exposed to sport-caught fish in western Michigan were investigated. PCB and DDE serum levels in the mothers were measured up to 3 times between 1973 and 1981 using the Webb-McCall packed column gas chromatography. Intrauterine exposures of the daughters were backward extrapolated from maternal serum levels. Offspring blood samples were collected during days 3 to 12 of the menstrual cycle and were measured for DDE levels and mRNA expression. Expression of the major genes involved in sex steroid metabolism was measured using mRNA compared with expression of 18S rRNA, a housekeeping gene. Current levels of DDE, PCB, and polychlorinated polybrominated diphenylethers (PBDEs) in offspring were determined. The association between the relative gene expression and levels of DDE and PCB at birth was estimated using linear regression controlling for confounders. Results: Higher maternal levels of PCBs were related to increased expression of aromatase in adult offspring; higher maternal DDE levels were associated with decreased expression of 17-β-hydroxylase. Current levels of PBDEs were associated with gene expression of the estrogen receptor-β. Conclusions: Our preliminary results show that the estimated intrauterine exposure to PCB and DDE may have a direct effect on the expression of sex steroid metabolism and activity in female adult offspring. Our findings indicate that sex steroids in female offspring may be affected by their mothers’ exposure without having experiencing direct exposure.

Facile Hyphenation of Gas Chromatography and a Microcantilever Array Sensor for Enhanced Selectivity

The very simple coupling of a standard, packed-column gas chromatograph with a microcantilever array (MCA) is demonstrated for enhanced selectivity and potential analyte identification in the analysis of volatile organic compounds (VOCs). The cantilevers in MCAs are differentially coated on one side with responsive phases (RPs) and produce bending responses of the cantilevers due to analyte-induced surface stresses. Generally, individual components are difficult to elucidate when introduced to MCA systems as mixtures, although pattern recognition techniques are helpful in identifying single components, binary mixtures, or composite responses of distinct mixtures (e.g., fragrances). In the present work, simple test VOC mixtures composed of acetone, ethanol, and trichloroethylene (TCE) in pentane and methanol and acetonitrile in pentane are first separated using a standard gas chromatograph and then introduced into a MCA flow cell. Significant amounts of response diversity to the analytes in the mixtures are demonstrated across the RP-coated cantilevers of the array. Principal component analysis is used to demonstrate that only three components of a four-component VOC mixture could be identified without mixture separation. Calibration studies are performed, demonstrating a good linear response over 2 orders of magnitude for each component in the primary study mixture. Studies of operational parameters including column temperature, column flow rate, and array cell temperature are conducted. Reproducibility studies of VOC peak areas and peak heights are also carried out showing RSDs of less than 4 and 3%, respectively, for intra-assay studies. Of practical significance is the facile manner by which the hyphenation of a mature separation technique and the burgeoning sensing approach is accomplished, and the potential to use pattern recognition techniques with MCAs as a new type of detector for chromatography with analyte-identifying capabilities.

Surveillance of polychlorinated biphenyl congeneric patterns in human breast milk from 1973 to 2000 in Osaka, Japan

Because the analysis of polychlorinated biphenyls (PCBs) in 1970's was performed using a packed column gas chromatograph, with an electron capture detector to determine total-PCB concentration, analytical data obtained by this analysis do not meet the requirement for the risk assessment of PCB congeners. In this context, the present study was carried out to reevaluate the congeneric analysis data by analyzing breast milk fat specimens that have been kept frozen. PCB congeners in human breast milk were analyzed by high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS) using a capillary column for the selected ion monitoring (SIM) of PCBs. Twelve major PCB congeners were detected in breast milk. The concentrations of all congeners of PCBs in breast milk were found to decrease annually, and their changes over time differed greatly for each congener. Between 1973 and 2000, almost no changes in the proportions of the 12 congeners of heptachlorinated biphenyls (HpCBs) and hexachlorinated biphenyls (HxCBs) were found whereas a marked and a slight decrease in the proportion of pentachlorinated biphenyls (PeCBs) and tetrachlorinated biphenyls (TeCBs), respectively, were observed. The PCB contamination of the Japanese population is estimated to be largely caused by seafood intake, but the proportions of PCB congeners in fish commodities were different from those in breast milk. The absorption, metabolism and therefore the accumulation of PCBs in the human body differ greatly depending on the congener.

Composition of Products from the Supercritical Water Gasification of Glucose: A Model Biomass Compound

Glucose, as a representative biomass model compound, was gasified under supercritical water conditions in a batch reactor. The influences of temperature in the subcritical and supercritical regimes of water, oxidant concentration, glucose concentration, and residence time were examined in relation to the yield and composition of the product gases and oils. The product gases were analyzed by packed-column gas chromatography, and the oils were extracted using solid-phase extraction and analyzed by coupled gas chromatography/mass spectrometry. The main gases produced were carbon dioxide, carbon monoxide, methane, and hydrogen, and there was significant production of oil and char. As the temperature was increased, there was an increase in the yield of gas; similarly, gas yield also increased as the concentration of the oxidant, hydrogen peroxide, was increased. The influence of residence time on the yield of products was small, with a slight decrease in oil yield and an increase in char yield. The oils were composed of a range of oxygenated compounds, including cyclopentanone, methoxybenzene, acetic acid, furfural, acetophenone, phenol, benzoic acid, and their alkylated derivatives. A reaction mechanism is proposed that describes a possible reaction route for the formation of the characteristic compounds found in the oils.

Handbook of basic tables for chemical analysis

Handbook of basic tables for chemical analysis

Gas chromatographic method for detection of urinary sucralose: application to the assessment of intestinal permeability

We developed a capillary column gas chromatography (CCGC) method for the measurement of urinary sucralose (S) and three other sugar probes including, sucrose, lactulose (L) and mannitol (M) for use in in vivo studies of intestinal permeability. We compared the capillary method with a packed column gas chromatography (PCGC) method. We also investigated a possible role for sucralose as a probe for the measurement of whole gut permeability. Sample preparation was rapid and simple. The above four sugars were detected precisely, without interference. We measured intestinal permeability using 5- and 24-h urine collections in 14 healthy volunteers. The metabolism of sugars was evaluated by incubating the intestinal bacteria with an iso-osmolar mixture of mannitol, lactulose and sucralose at 37 °C for 19 h. Sugar concentrations and the pH of the mixture were monitored. The use of the CCGC method improved the detection of sucralose as compared to PCGC. The average coefficient of variation decreased from 15% to 4%. It also increased the sensitivity of detection by 200–2000-fold. The GC assay was linear between sucralose concentrations of 0.2 and 40 g/l ( r=1.000). Intestinal bacteria metabolized lactulose and acidified the media but did not metabolize sucralose or mannitol. The new method for the measurement of urinary sucralose permits the simultaneous quantitation of sucrose, mannitol and lactulose, and is rapid, simple, sensitive, accurate and reproducible. Because neither S nor M is metabolized by intestinal bacteria, and because only a tiny fraction of either sugar is absorbed, this pair of sugar probes appears to be available for absorption throughout the GI tract. Thus, the 24-h urinary concentrations of S and M, or the urinary S/M ratio following an oral dose of a sugar mixture, might be good markers for whole gut permeability.

Volatile metal species in coal combustion flue gas.

Metals are released in effluents of most of combustion processes and are under intensive regulations. To improve our knowledge of combustion process and their resulting emission of metal to the atmosphere, we have developed an approach allowing usto distinguish between gaseous and particulate state of the elements emitted. This study was conducted on the emission of volatile metallic species emitted from a coal combustion plant where low/medium volatile coal (high-grade ash) was burnt. The occurrence of volatile metal species emission was investigated by cryofocusing sampling procedure and detection using low-temperature packed-column gas chromatography coupled with inductively coupled plasma-mass spectrometry as multielement detector (LT-GC/ICP-MS). Samples were collected in the stack through the routine heated sampling line of the plant downstream from the electrostatic precipitator. The gaseous samples were trapped with a cryogenic device and analyzed by LT-GC/ICP-MS. During the combustion process, seven volatile metal species were detected: three for Se, one for Sn, two for Hg, and one for Cu. Thermodynamic calculations and experimental metal species spiking experiments suggest that the following volatile metal species are present in the flue gas during the combustion process: COSe, CSSe, CSe2, SeCl2, Hg0, HgCl2, CuO-CuSO4 or CuSO4 x H2O, and SnO2 or SnCl2. The quantification of volatile species was compared to results traditionally obtained by standardized impinger-based sampling and analysis techniques recommended for flue gas combustion characterization. Results showed that concentrations obtained with the standard impinger approach are at least 10 times higher than obtained with cryogenic sampling, suggesting the trapping microaerosols in the traditional methods. Total metal concentrations in particles are also reported and discussed.

Adsorption of aqueous inorganic mercury and methylmercury on suspended kaolin: influence of sodium chloride, fulvic acid and particle content

The main tendencies in the adsorption of dissolved inorganic mercury (Hg2+) and methylmercury (MeHg+) on suspended kaolin particles have been investigated in synthetic aqueous solutions. The influence of NaCl, fulvic acid (FA) and suspended particulate matter (SPM) in the system has been studied at a constant pH of 7.2. The experiments were arranged according to a full factorial design with three factors (NaCl, FA SPM) at low (−) and high (+) levels. A central point (0) was repeated four times to estimate the reproducibility of the results. The low and high levels investigated were 0–35 g l−1, 0–10 mg l−1 and 0.5–5 g l−1 for the concentrations of NaCl, FA and kaolin respectively. In order to match the linear range of the analytical technique the total concentration of mercury (as Hg2+ or MeHg+) in the synthetic suspensions was 25 ng ml−1. After chemical stabilization of each suspension, the Hg2+ or MeHg+ content in the clear filtrate was determined by an automated hyphenated technique combining the following steps: (i) derivatization by hydride generation, (ii) preconcentration by cryogenic trapping, (iii) separation by packed column gas chromatography and (iv) detection by quartz furnace atomic absorption spectrometry. The removal of Hg2+ and MeHg+ from the solution via adsorption on particles ranged, respectively, from 12.4 to 94.9% and from 1.7 to 45.6% of the total mercury compound concentration. High concentrations of NaCl led to lower adsorption rates of both mercury species. The adsorption of MeHg+ was enhanced in the presence of FA, whereas that of Hg2+ was clearly diminished. High levels of SPM promoted the adsorption of both Hg2+ and MeHg+ on kaolin particles. Several experiments were also conducted to check the adsorption rate of Hg2+ and MeHg+ on natural particles collected in the Gironde estuary. The results confirmed the general trends observed when using reference kaolin particles. The results presented here will be helpful for groups modelling the physico-chemical behaviour of mercury in estuary conditions. Copyright © 2001 John Wiley & Sons, Ltd.

Adsorption of aqueous inorganic mercury and methylmercury on suspended kaolin: influence of sodium chloride, fulvic acid and particle content

AbstractThe main tendencies in the adsorption of dissolved inorganic mercury (Hg2+) and methylmercury (MeHg+) on suspended kaolin particles have been investigated in synthetic aqueous solutions. The influence of NaCl, fulvic acid (FA) and suspended particulate matter (SPM) in the system has been studied at a constant pH of 7.2. The experiments were arranged according to a full factorial design with three factors (NaCl, FA SPM) at low (−) and high (+) levels. A central point (0) was repeated four times to estimate the reproducibility of the results. The low and high levels investigated were 0–35 g l−1, 0–10 mg l−1 and 0.5–5 g l−1 for the concentrations of NaCl, FA and kaolin respectively. In order to match the linear range of the analytical technique the total concentration of mercury (as Hg2+ or MeHg+) in the synthetic suspensions was 25 ng ml−1. After chemical stabilization of each suspension, the Hg2+ or MeHg+ content in the clear filtrate was determined by an automated hyphenated technique combining the following steps: (i) derivatization by hydride generation, (ii) preconcentration by cryogenic trapping, (iii) separation by packed column gas chromatography and (iv) detection by quartz furnace atomic absorption spectrometry. The removal of Hg2+ and MeHg+ from the solution via adsorption on particles ranged, respectively, from 12.4 to 94.9% and from 1.7 to 45.6% of the total mercury compound concentration. High concentrations of NaCl led to lower adsorption rates of both mercury species. The adsorption of MeHg+ was enhanced in the presence of FA, whereas that of Hg2+ was clearly diminished. High levels of SPM promoted the adsorption of both Hg2+ and MeHg+ on kaolin particles. Several experiments were also conducted to check the adsorption rate of Hg2+ and MeHg+ on natural particles collected in the Gironde estuary. The results confirmed the general trends observed when using reference kaolin particles. The results presented here will be helpful for groups modelling the physico‐chemical behaviour of mercury in estuary conditions. Copyright © 2001 John Wiley & Sons, Ltd.

Determination of Nicotine in Tobacco: Collaborative Study

Abstract An international collaborative study was performed to compare several analytical methods for the determination of nicotine in tobacco that are in current use around the world. Five nicotine methods were evaluated and compared, specifically methyl-t-butyl ether (MTBE) extraction with capillary-column gas chromatography (GC), n-hexane extraction with capillary-column GC, n-hexane extraction with packed-column GC, methanol/ammonia extraction with capillary-column GC, and aqueous extraction with continuous flow analyzer (CFA) colorimetry. A total of 37 laboratories participated in the study, with between 9 and 18 laboratories submitting data per nicotine method. Repeatability, reproducibility, and mean nicotine statistics were calculated and compared for each method. Results for reproducibility (%) and mean nicotine difference (%, relative to the mean of the three capillary-GC methods), respectively, for each method are as follows: MTBE method (2.5%, -1.40%), hexane-capillary (4.5%, +0.06%), methanol/ammonia (3.7%, +1.34%), CFA (4.4%, +4.08%), and hexane-packed (5.8%, +4.14%). Pair-wise group comparison tests with simultaneous 95% confidence intervals were used to compare the sample nicotine values between any two given methods. Eight of the ten pair-wise comparisons were statistically different at 95% confidence, the two statistically indistinguishable pair-wise comparisons being CFA vs. hexane-packed and hexane-capillary vs. methanol/ammonia. The results of this collaborative study will be useful toward the goal of standardizing on a reference method for nicotine analysis in tobacco and tobacco products.