On-line Analysis of Catalytic Reaction Products Using a High-Pressure Tandem Micro-reactor GC/MS.

When a GC/MS system is coupled with a pressurized reactor, the separation efficiency and the retention time are directly affected by the reactor pressure. To keep the GC column flow rate constant irrespective of the reaction pressure, a restrictor capillary tube and an open split interface are attached between the GC injection port and the head of a GC separation column. The capability of the attached modules is demonstrated for the on-line GC/MS analysis of catalytic reaction products of a bio-oil model sample (guaiacol), produced under a pressure of 1 to 3 MPa.

Rapid Quantification of N-Methyl-2-pyrrolidone in Polymer Matrices by Thermal Desorption-GC/MS.

Analysis of a residual solvent in polymeric materials has become an important issue due to the increased regulations and standards for its use. N-Methyl-2-pyrrolidone (NMP) is a solvent widely used in many industries and restricted as one of the chemicals under EU REACH regulations due to its potential harmful effects. In this study, thermal desorption-gas chromatography/mass spectrometry (TD-GC/MS) is applied for the quantitative analysis of NMP with the use of a polymer-coated sample cup. By using the polymer-coated sample cup, the vaporization of NMP was prevented during waiting time before TD-GC/MS analysis. The calibration curve for the TD method showed good linearity (correlation coefficient, r2 = 0.9998) and precision values (below 5.3% RSD). NMP recovery rates in different polymer matrices (PS, PMMA and PVC) were in the range of 98.8 to 106.6% with RSD values below 5.0%. The quantification result (600 mg NMP/kg PVC) for the blind NMP carrying sample in a PVC matrix by TD-GC/MS was higher than that (532 mg NMP/kg PVC) by solvent extraction-GC/MS method.

Characterization of soil organic matter with different degrees of humification using evolved gas analysis-mass spectrometry.

Evolved gas analysis-mass spectrometry (EGA-MS) provides a direct connection between the pyrolyzer and mass spectrometer through a deactivated capillary tube, and provides both a thermal profile relating to the differential thermogravimetric curve of the sample and a mass spectrum of evolved gas from the sample. In this study, EGA-MS was performed to obtain thermal profiles and identify the pyrolysis products of 12 humic acids (HAs) with different degrees of humification extracted from 5 Andisols, 3 Entisols, and 3 Inceptisols, as well as soil samples. All HAs were thermally decomposed gradually over a wide temperature range (100-700°C), and the EGA curves showed four peaks and shoulders at around 250, 350, 450, and 550°C. The peaks at around 550°C were observed for the Andisol HAs only. Carboxyl groups, carbohydrates, and short chain alkanes and alkenes of the HAs and bulk soil samples evolved at a relatively low-temperature region (200-300°C). On the other hand, aromatics including benzenes and lignin derivatives evolved at a relatively high-temperature region (300-600°C). While the shapes of the EGA curves were different between the soils and extracted HAs, the major components of the evolved gas and the pyrolysis behavior of the constituents in the HAs and soil samples were similar. The amount of evolved gas from the Andisol HAs, which mainly consisted of CO2, was very low in comparison to that from the Entisol and Inceptisol HAs. The amount of evolved gas and the molecular weight of the pyrolysis products decreased as humification progressed, but the proportion of CO2 in the total area of the EGA curves increased. The results demonstrated that humification reduces the proportion of volatile components and increases the amount of carboxyl groups. As a result, the molecular structure of HAs is found to be mainly composed of non-volatile components and carboxyl groups. Since EGA-MS can provide information about the chemical structure and pyrolysis characteristics of a small sample without pretreatment, it is a useful tool for soil organic matter research.

Comparative study of thermal desorption and solvent extraction-gas chromatography-mass spectrometric analysis for the quantification of phthalates in polymers.

For the quantitative analysis of phthalates in polymers, a thermal desorption (TD)-GC-MS method was compared with solvent extraction (SE)-GC-MS methods which require the long pretreatment procedures using large amount of harmful organic solvents. Calibration curves of TD-GC-MS showed good linearity (r(2)>0.9997) and low method detection limit (<30mg/kg with 9.0% RSD). Quantification results for three kinds of test phthalate polymer samples (test PTPSs) showed an RSD below 7.4% and acceptable recoveries (78.3-117.4%) as in the standard method of International Electrotechnical Commission. Even in a sample with a high concentration of phthalates (PTPS #3), the method also showed good recovery with low RSD values. The TD-GC-MS results were comparable with those results by SE-GC-MS methods, indicating that TD-GC-MS method also can be used for the quantification of phthalates in polymers. The average recovery (92-103%) and RSD (<20%) values obtained from international inter-laboratory study for TD-GC-MS performed in six laboratories also indicated that TD-GC-MS can be used as an international standard method for the quantification of phthalates in polymers.

Polymer-coated sample cup for quantitative analysis of semi-volatile phthalates in polymeric materials by thermal desorption-gas chromatography-mass spectrometry.

A new "polymer-coated" sample cup useful for the analysis of phthalates in polymeric materials by thermal desorption (TD)-GC/MS using a temperature programmable furnace type pyrolyzer as a TD device was developed to suppress the emission of semi-volatile phthalates such as dimethyl phthalate (DMP) and diethyl phthalate (DEP) during the measurements. The inner surface of a sample cup was coated by polymers which act as a sorbent for the phthalates. Three polymers, polyvinyl chloride, polystyrene and poly (methyl methacrylate), were chosen as the coating polymers. A mixture of ten phthalates including DMP and DEP was used as the test sample to estimate the performance of the sample cups. When a conventional sample cup without any polymer coating was used, 90 and 50% reductions in the peak areas of DMP and DEP were respectively observed at the waiting time of 200 min. On the contrary, no reduction of peak area of DMP and DEP during the same waiting time was observed with any one of the three coating polymers at the proper polymer film thickness. These results suggest that the polymer-coated sample cup suppresses the emission of semi-volatile phthalates and is effective for the analysis of phthalates containing DMP and DEP by TD-GC/MS.

Evaluation of the thermal desorption-GC/MS method for the determination of decabromodiphenyl ether (DeBDE) in order of a few hundred ppm contained in a certified standard polystyrene sample.

Thermal desorption (TD)-GC/MS, recently developed for the determination of DeBDE in a polystyrene (PS) sample to an order of a few %, was evaluated in detail by using a certified standard PS sample containing 317 ppm of DeBDE. Not only the accuracy and precision of the results, but also the linearity of the working calibration curve were discussed in terms of the catalytic decomposition of DeBDE induced by the degrading macro-radical of the matrix polymer.

Rapid determination of decabromodiphenyl ether in polystyrene by thermal desorption-GC/MS.

A rapid determination of decabromodiphenyl ether (DeBDE) in polystyrene (PS) by thermal desorption (TD)-GC/MS was studied. The TD-GC/MS method using a pyrolysis-GC/MS system allowed the quick quantification of DeBDE in a waste TV back plate composing of a PS flame-retarded with polybrominated diphenyl ethers on the basis of the resulting chromatogram with a ca. 4% relative standard deviation without using any tedious sample pretreatment, such as solvent extraction.

Development of a novel solid-phase extraction element for thermal desorption gas chromatography analysis.

A novel solid-phase extraction element is developed for sorptive enrichment of dilute analytes from liquid samples with high extraction efficiencies due to its larger amounts of polydimethylsiloxane (PDMS) absorbent than the conventional syringe type of solid-phase microextraction (SPME). The extraction element is made of titanium (Ti) open tubular tube (30 mm x 1.2 mm i.d. x 1.6 mm o.d.) coated with a chemically bonded layer of PDMS (500 microm in thickness). The extraction element combined with thermal desorption-gas chromatography-mass spectrometry using a pyrolysis-gas chromatography-mass spectrometry system was used to extract and analyze a typical herbicide, bethrodine in water samples over a concentration range from 2.5 to 2.5 x 10(4) ng/l. Thus obtained calibration curve showed good linearity for the tested whole concentration range with regression coefficient of 0.992. Detection limit of 0.5 ng/l level was achieved and the reproducibility of the measurements for bethrodine at 10 ng/l level was found to be fairly good with relative standard deviation below 7.5%.