Analysis of waterborne paints by gas chromatography-mass spectrometry with a temperature-programmable pyrolyzer

Gas chromatography-mass spectrometry (GC-MS) with a temperature-programmable pyrolyzer was used for the analysis of waterborne paints. Evolved gas analysis (EGA) profiles of the waterborne paints were obtained by this temperature-programmed pyrolysis directly coupled with MS via a deactivated metal capillary tube. The EGA profile suggested the optimal thermal desorption conditions for solvents and additives and the subsequent optimal pyrolysis temperature for the remaining polymeric material. Polymers were identified from pyrograms with the assistance of a new polymer library. The solvents were identified from the electron ionization mass spectra with the corresponding chemical ionization mass spectra. The additive was identified as zinc pyrithione by comparison with authentic standard. Zinc pyrithione cannot be analyzed by GC-MS as it is. However, the thermal decomposition products of zinc pyrithione could be detected. The information on the decomposition temperature and products was useful for the identification of the original compound.     

铁皮石斛的裂解气相色谱指纹图谱及其系统聚类分析

采用裂解气相色谱/质谱法(Py-GC/MS)测定了10种不同产地的铁皮石斛并结合系统聚类分析法比较了这些铁皮石斛的指纹图谱,采用释放气体分析法考察了裂解温度对指纹图谱的影响。结果表明,0.4 mg样品在450 ℃下可瞬间裂解,10种样品的指纹图谱具有相似性,且重现性好;采用系统聚类分析能区别不同产地的样品。本法快速、简便、准确,不失为药材质量控制的良好方法。     

Development of new pyrolysis–GC/MS system incorporated with on-line micro-ultraviolet irradiation for rapid evaluation of photo, thermal, and oxidative degradation of polymers

A new pyrolysis–GC/MS system incorporating with on-line micro-ultraviolet (UV) irradiation was developed to make rapid evaluation of the synergistic material deterioration during UV irradiation under thermal and oxidative atmospheres. The basic effectiveness of the system was demonstrated by polystyrene, polypropylene and polycarbonate as the test samples. The volatile products evolved during deterioration of the polymers were analyzed on-line by thermal desorption GC/MS, and then the residual degraded polymers were analyzed by evolved gas analysis (EGA) and/or Py–GC/MS to obtain specific thermograms and pyrograms. Based on these results, the deterioration mechanism of the polymeric materials during irradiation under thermal and oxidative atmosphere can be evaluated using a sub-milligram polymer sample within a relatively short period of time.     

莪术药材的闪蒸气相色谱测定及其模式识别分析研究

建立了莪术药材的闪蒸-气相色谱法(FE-GC),采用FE-GC测定了3个产地的9个莪术样品.0.4mg的粉末样品, 在200℃下闪蒸,经色谱分离,基于闪蒸色谱图上分离鉴定到的35个共有峰的相对强度,结合化学模式识别即主成分分析和系统聚类分析法对莪术样品进行了鉴别分析.3个产地的莪术样品可以很好地得到区别.本法快速、简便、准确, 不失为药材质量控制的良好方法.     

Thermal characterization of starch-based polymers produced by <Emphasis Type="Italic">Ophiostoma</Emphasis> spp

The thermal behavior of modified starches (MS) produced by biosynthetic pathway is described based on a comparative analysis with native starches (NS). MS were produced by fermentation in presence of Ophiostoma spp. cultures. Thermogravimetric analysis (TG) with successive derivatives (DTG) and differential scanning calorimetry (DSC) were used for this study. NS results showed a single peak dominating both the TG (DTG) and DSC plots. A double thermal transition event was detected in samples of MS. The procedural decomposition temperature (T _i–T _f; lowest onset temperature of initial and final mass change) was carried out within a narrow interval of temperatures for NS (610–640 °C). This interval could not be reached within the 1,000 °C range in MS. Residues higher than 10% were recorded for MS at this temperature. The presence of the double thermal transition in MS is discussed.     

Determination of residual solvents in pharmaceuticals by thermal desorption-GC/MS.

A novel method for the determination of residual solvents in pharmaceuticals by thermal desorption (TD)-GC/MS has been established. A programmed temperature pyrolyzer (double shot pyrolyzer) is applied for the TD. This method does not require any sample pretreatment and allows very small amounts of the sample. Directly desorbed solvents from intact pharmaceuticals (ca. 1 mg) in the desorption cup (5 mm x 3.8 mm i.d.) were cryofocused at the head of a capillary column prior to a GC/MS analysis. The desorption temperature was set at a point about 20 degrees C higher than the melting point of each sample individually, and held for 3 min. The analytical results using 7 different pharmaceuticals were in agreement with those obtained by direct injection (DI) of the solution, followed by USP XXIII. This proposed TD-GC/MS method was demonstrated to be very useful for the identification and quantification of residual solvents. Furthermore, this method was simple, allowed rapid analysis and gave good repeatability.     

Determination of the temperature—time profile of the sample in pyrolysis—gas chromatography

The mean temperature-time profile in a sample has been determined in order to establish whether it is possible to equate the temperature of the pyrolyzer with that of the sample being pyrolyzed. This was done by studying the degradation of cis-1,4-polybutadiene be sequential pyrolysis. The rate of degradation was determined for different amounts (0.5–20 μg) of sample. The temperature dependence of the degradation rate was determined from an Arrhenius plot. The experimental results were combined with theoretically derived expressions for the heating of samples subjected to pyrolysis. The temperature–time profiles of different amounts of sample could then be calculated.It was found that samples thinner than 1 μm were heated to a mean temperature of 95% of the temperature of the pyrolyzer in 40 ms or faster. Too thin samples can give rise to noticeable catalytic effects.By choosing the appropriate pyrolysis conditions of sample thickness, time and temperature it is possible to assume that the temperature of the sample is nearly the same as that of the pyrolyzer.     

Quantitative analysis of phthalates using a pyrolyzer gas chromatography/mass spectrometry method

A pyrolyzer gas chromatography/mass spectrometry (GC/MS) method eliminates toxic solvents that burden our environment and can address the crucial problem of the solvent extraction GC/MS method. The purpose of this study is to establish an efficient quantitative analysis method for 10 phthalates that are regulated by the several governments. A change of concentrations over time for phthalates and internal standards was measured to verify the feasibility of using an auto sampler that facilitates analyzing multiple samples. Both standards maintained constant concentrations over the appropriate time for analysis. A certified reference material under the auspices of the Korea Research Institute of Standards and Science was used to verify the calibration curve obtained by the pyrolyzer GC/MS method, and a deviation was considered similar to the solvent extraction GC/MS method. Then, the limit of detection and limit of quantitation values were confirmed for various consumer products. To verify the reliability of the method, a comparative test with several accredited testing institutes was conducted, and the results were within the standard deviations of the results provided by the institutes. These results indicate that the pyrolyzer GC/MS method can be used in not only screening but also in accurate quantitative analysis.     

Development of a multi-sample micro UV irradiator for accelerated deterioration of polymers

The authors previously developed a pyrolysis-gas chromatograph/mass spectrometry (Py-GC/MS) system incorporating a micro ultraviolet (UV) irradiator which allowed more rapid deterioration of polymeric materials compared to outdoor exposure tests and various accelerated weathering test methods such as weather meters. The micro UV irradiator, however, could handle only a single sample at a time. To achieve multi-sample deterioration in a short time, herein a new UV irradiator was developed by which up to 18 samples on a rotatable sample cup holder can be simultaneously deteriorated at a desired temperature under UV irradiation. The basic performance of the irradiator is evaluated in terms of the rate and reproducibility of accelerated deterioration by using high impact polystyrene (HIPS) as the test sample. The HIPS samples before and after deterioration are subjected to evolved gas analysis-mass spectrometry (EGA-MS) focusing on the changes in the peak width observed in the thermograms. High precision in the peak width measurements among the samples irradiated at various positions on the rotatable sample cup holder is observed with RSD values less than 4.3%. The newly developed irradiator for multi-samples requires a six times longer period to accomplish a comparable deterioration level than the previously developed irradiator. This lengthening can be attributed to the difference in the light intensities of both irradiators at the sample position. However, the relationship between the peak width and the irradiation time has similar profiles for both irradiators. This similarity indicates a good correlation of data measured by both irradiators.     

Direct analysis of alkylphenols in Ginkgo biloba leaves by thermochemolysis–gas chromatography/mass spectrometry in the presence of tetramethylammonium hydroxide

Thermochemolysis–gas chromatography/mass spectrometry (GC/MS) in the presence of tetramethylammonium hydroxide (TMAH) was applied to the determination of alkylphenols in Ginkgo biloba leaves directly using a vertical microfurnace pyrolyzer. TMAH thermochemolysis–GC enabled the highly sensitive determination of alkylphenols including ginkgolic acids and ginkgols in G. biloba leaves as their methyl derivatives on the resulted pyrograms. On the basis of their peak areas, the contents of the alkylphenols in G. biloba leaf sample were rapidly and precisely determined without using any tedious and time-consuming pretreatment.     

Development of a new pyrolyzer for thermal desorption and/or pyrolysis gas chromatography of polymeric materials

A new vertical microfurnace-type pyrolyzer for thermal desorption and/or pyrolysis-gas chromatography has been developed. The pyrolyzer consists of two independent temperature-controlled ovens. Initially, in the desorption process, a sample cup containing the polymeric sample of interest is inserted into an oven at 300°C; the sample is then re-positioned at the upper part of the pyrolyzer where the temperature is maintained at room temperature. The resulting vaporized components such as residual solvents and additives give a desorption chromatogram. The relative peak intensities of desorbed plasticizers in acrylonitrile butadiene-rubber gave a relative standard deviation (RSD) of less than 2%. Subsequently, pyrolysis of the remaining polymer is conducted by dropping the sample cup into the second, pyrolyzing, oven at 55°C; at this stage the pyrogram is recorded. The resulting two chromatograms of desorbed components and pyrolysis products make it easier to characterize the polymer formulation than the complicated pyrogram obtained by an ordinary, single-step pyrolysis.     

大体积进样技术在气相色谱-质谱法测定 二英类化合物中的应用

利用大体积进样技术(large volume injection,LVI),结合气相色谱-质谱方法对二英的测定效果进行了研究。同时与传统分流/不分流进样技术进行了对比。对进样体积为1,5,10,25,50和100 μL的色谱图进行了分析。研究表明使用大体积进样方式,在不影响色谱分离度的同时,大幅度提高了分析灵敏度。通过对土壤样品的检测,证明该方法可以用于环境样品的实际测定。     

Speciation Analysis of Thallium by Reversed‐phase Liquid Chromatography ‐ Inductively Coupled Plasma Mass Spectrometry

An inductively coupled plasma mass spectrometer (ICP‐MS) was used as a liquid chromatographic detector for the speciation analysis of thallium in environmental samples. In this study, ionic thallium species, namely Tl(I) and Tl(III) were well separated by reversed‐phase high performance liquid chromatography (RP‐HPLC) with a C8‐HPLC column as the stationary phase and 1 mmol L^?1 tetrabutylammonium phosphate (TBAP), 2 mmol L^?1 diethylenetriamine pentaacetic acid (DTPA) in 1% v/v methanol solution (pH 6) as the mobile phase. Effluent from the HPLC column was delivered to the nebulizer of the ICP‐MS for the determination of thallium. The separation was complete in less than 3 min. Detection limit was 0.002 μg L^?1 for both Tl(I) and Tl(III) compounds based on peak height. The relative standard deviation of the peak areas for five injections of a mixture containing 1 μg Tl L^?1 was better than 3.4%. The concentrations of Tl compounds were determined in standard reference materials, including NIST SRM 1643e Trace Elements in Water and NRCC NASS‐5 Open Ocean Seawater and water samples collected in Kaohsiung area, Taiwan. The HPLC‐ICP‐MS results of the reference samples agreed with the reference values. This method has also been applied to determine Tl(I) and Tl(III) compounds in custard apple (Annona squamosa) leaves collected from Chai‐shan Mountain, Kaohsiung and Taitung City, Taiwan. The thallium species were quantitatively leached from the leaves with a 5 mmol L^?1 DTPA in 100 mmol L^?1 ammonium acetate solution in an ultrasonic bath during a period of 30 min. The HPLC‐ICP‐MS result that was obtained after the analysis of leaves sample showed a satisfactory agreement with the total thallium concentration obtained by ICP‐MS analysis of completely dissolved sample.     

静态顶空-气相色谱/质谱法同时检测环境水体中59种挥发性有机物

静态顶空法是一种简单、环保的样品前处理方法.通过对比试验,优化了影响静态顶空进样方法灵敏度的主要因素,确定了较佳的样品盐度(40%)、平衡温度(80℃)、平衡时间(10 min)、平衡压力(0.103 4 MPa)、定量环平衡时间(20 s)、进样时间(3 min)等前处理方法参数.采用优化后水样前处理条件及1.00 k V的检测器电压,59种挥发性有机物在特定的线性范围内,标准曲线线性相关系数均大于0.998,方法检出限为丙烯腈4.4μg/L、硝基苯7.6μg/L,其余挥发性有机物(VOCs)介于0.06~1.4μg/L,饮用水源水及污水处理厂进水实际样品加标回收率为60%~110%,精密度(RSD)为0.33%~22%(n=6).建立的静态顶空-气相色谱/质谱法(HS-GC/MS)水样前处理过程自动化,可同时对水中59种挥发性有机物进行检测.     

An automatic data acquisition system for simultaneous operation of two Mettler thermoanalyzers

An automatic data acquisition system was developed for two Mettler Vacuum Recording Thermoanalyzers, Model TA-I, using a Hewlett-Packard 9825S calculator. The interface with the thermoanalyzers is unique in the way that it is independent of and has a wider dynamic range than the six-channel strip chart recorder supplied with the instrument. The data acquisition system permits data from two TA-Is simultaneously in operation to be collected and stored in a magnetic tape cartridge.To facilitate rapid analysis of the acquired data, five computer programs were also developed for use with a Hewlett-Packard 9872A plotter. This data reduction system would (1) plot the thermograms (DTA, TG, DTG) including the % weight changes as a function of temperature or time, (2) label the thermograms, (3) record the experimental conditions, (4) correct the thermogravimetric data for effect due to buoyancy, if desired, (5) locate and mark the peak minima and maxima on DTA and DTG curves, and (6) tabulate the % weight change between two temperatures or time.     

Large volume injection of water in gas chromatography–mass spectrometry using the Through Oven Transfer Adsorption Desorption interface: Application to multiresidue analysis of pesticides

In the present work, the potential of the Through Oven Transfer Adsorption Desorption (TOTAD) interface for the large volume injection (LVI) of aqueous samples in gas chromatography (GC) using a mass spectrometry (MS) detector is demonstrated. To this end, a new method for the determination of pesticides in water is presented, being the first developed method in which injection of large amounts of polar solvents using the TOTAD interface and an MS detector are combined, is applied to the determination of pesticides in water. Water samples, as large as 5 ml, were directly injected into a capillary GC. No sample pre-treatment step other than simple filtration was needed. The TOTAD interface allows the introduction of several millilitres of water, while maintaining good chromatographic characteristics. The water is almost entirely eliminated, so that LVI of aqueous samples and an MS detector can be used without problems. Organophosphorus, organochlorine, and triazine pesticides were determined in one run. Calibration curves were linear in the range tested and the sensitivity achieved injecting 5 ml of water sample was sufficient for most of the target pesticides but not for all of them. Sensitivity of the analysis can be improved by increasing the sample volume. No variability was observed in the retention times and relative standard deviations from absolute peak areas were good, considering that they corresponded to the overall analysis. The method was applied to the analysis of pesticide residues in real water samples.     

Thermochemistry of coal oxidation

Five types of Polish bituminous coal of different grades were analysed using, simultaneously, thermogravimetric analysis (TGA), differential thermogravimetry (DTG), differential thermal analysis (DTA) and evolving gas analysis (EGA) to investigate the non-isothermal coal oxidation. The TGA, DTG and DTA curves, together with EGA, provided parameters which characterize the tendency of a given coal towards oxidation. The TGA and EGA parameters can also be used to approximate the specific active surface area of coal in reaction with oxygen. Due to the negative effects of coal oxidation, such as self-oxidation, an inhibitor was proposed and tested by analysis of the above specified thermoanalytical curves and EGA.     

Determination of molecular mass distribution of silicone oils by supercritical fluid chromatography, matrix-assisted laser desorption ionization time-of-flight mass spectrometry and their off-line combination

Silicone oil samples were characterized by supercritical fluid chromatography (SFC), matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI--TOF MS), and their off-line combination. SFC was used to separate samples of silicone oils on micropacked capillary columns. The fractions for the identification studies were obtained from SFC runs at defined time intervals, when the restrictor was pulled out from the chromatographic flame ionization detector (FID) and inserted into a glass vial with acetone. MALDI--TOF MS was used for the identification of individual oligomers in the fractions separated. The molecular mass distributions determined based on SFC and MALDI--TOF MS measurements were compared. From this comparison, it follows that the results are in good agreement. However, certain differences were observed: MALDI--TOF MS was capable of detecting somewhat larger oligomers than the SFC-FID, but the lower molecular mass oligomers were not present in the MALDI spectra. Differences in the region of lower molecular masses can be explained by evaporation of the more volatile low molecular mass oligomers resulting from heating of the sample during the MALDI--TOF MS measurements as a result of the absorption of the laser shot energy. The fact that no high mass discrimination effects of the MALDI--TOF MS measurements, compared with SFC, were observed is very promising for further applications of MALDI--TOF MS in characterizing synthetic polymers of moderate polydispersity.     

Influence of the morphology of samples in the pyrolysis of PVC

PVC was used as a model substance to study the dependence of thermal measurement data on the preparation and morphological characteristics of samples The PVC treated was a commercially available suspension polymer, Ongrovil S 155, produced by the Borsodi Vegyi Kombinát. The whole thermal process was followed by TG and DTG measurements in air and argon atmospheres by means of a Du Pont 990 Thermoanalyzer. Evolved-gas analysis was performed with a home-made apparatus. Pyrolysis gas chromatography was accomplished using a Hamilton type pyrolyzer and a Carlo Erba Chromatograph furnished with a flame ionization detector. The investigations showed benzene and other components to be evolved from the initial polymer and an alteration depending on the morphological characteristics of the samples. This was suggested to be due to the different mechanisms of thermal degradation of the PVC.     

Injection by Programmed Temperature Vaporization Injection (PTV) of Gaseous Samples for Gas Chromatography – Atomic Emission Spectrometry (GC-AED)

Programmed temperature vaporization injection (PTV) coupled to gas chromatography and atomic emission detector (AED) has been studied for large volume injection of gaseous samples. As examples of the effectiveness of the technique, the results of the analysis of a series of headspace samples of foods such as garlic and onion, and of landfill gases are presented. The volumes of gaseous samples reconcentrated varied from a few milliliters up to liters depending on analyte dilution, through focusing onto a sorbent trap, then rapid liberation into the GC-AED system by programmed thermal desorption. Despite the high carrier gas flow rates associated with direct PTV-GC, AED performance and sensitivity were unaffected. The detailed elemental information obtained from the PTV-GC-AED analyses was confirmed using a PTV coupled to a gas chromatograph with ion trap detector mass spectrometer as detector (PTV-GC-ITD/MS).