Vertical Microfurnace Pyrolyzer Research Articles

Analysis of n-6 / n-3 ratio of polyunsaturated fatty acids in human serum by reactive thermal desorption-gas chromatography using a vertical microfurnace pyrolyzer

Thermally assisted hydrolysis and methylation-gas chromatography (THM-GC) using a vertical microfurnace pyrolyzer and a flame ionization detector (FID) was applied to rapid analysis of chemical composition for polyunsaturated fatty acid (PUFA) components in human serum. Here, the authors used a reactive thermal desorption (RTD) method, where 2 μL of a serum sample was subjected to the THM reaction at 250 °C for 20 s, to detect PUFA components with high selectivity and sensitivity. The resulting chromatograms clearly showed a series of fatty acid methyl esters including PUFAs without any interference peaks derived from the matrix components of the serum samples. Furthermore, the observed chemical composition and n-6 / n-3 ratio for PUFA components were in good agreement with those obtained by a conventional analytical technique involving solvent extraction and transmethylation.

The composition analysis of free and bonded fatty acids in Polysorbate 80 by on-line two-step pyrolytic methylation-gas chromatography

An on-line two-step pyrolytic methylation technique combined with gas chromatography was developed for rapid analysis of free and bonded fatty acids in Polysorbate 80 respectively. Free fatty acids in Polysorbate 80 were transformed to their corresponding fatty acid methyl esters in the presence of tetramethylammonium acetate (TMAAc) in the first step with a vertical microfurnace pyrolyzer at 300 °C. After the analysis of free fatty acids, bonded fatty acids were then transformed into methyl esters in the presence of tetramethylammonium hydroxide (TMAH) at 300 °C. The effects of pyrolytic methylation temperature, TMAAc concentration and ratio to Polysorbate 80 were evaluated. The range of linearity, reproducibility, the detection limits (LODs), and the quantitation limits (LOQs) were also investigated using linoleic (C18:2), oleic (C18:1), stearic (C18:0) acids. The recoveries ranged from 92.2 to 105.0%. The RSDs of intra-day and inter-day precision were in the range of 2.89–5.9% (n = 6) and 4.4–7.2% (n = 3) respectively. Compositions of free and bonded fatty acids in five Polysorbate 80 samples were analyzed respectively to evaluate the feasibility of the proposed method. The results prove that the proposed method is simple, solvent saving and environmentally friendly since it avoids off-line derivatization and solvent extraction, and has a potential application in the high quality control of Polysorbate 80.

Investigation on pyrolysis-gas chromatography fingerprint with pattern recognition for Fritillaria bulbus

Identification of Fritillaria bulbus species was investigated by pyrolysis-gas chromatography combined with fingerprint analysis. An amount of 0.2 mg of sample powder was pyrolyzed in a vertical micro-furnace pyrolyzer at 470 °C, and the pyrolysis products were directly taken into a gas chromatography with a flame ionization detector or a mass spectrometer. A total of 15 samples from different Fritillaria bulbus species were characterized by the relative areas of 32 common peaks. The established method had a good reproducibility and the fingerprints showed a high similarity. In addition, the discrimination of Fritillaria bulbus samples from different species was performed by principal component analysis and hierarchical cluster analysis on the basis of the obtained database. The results proved the Py-GC fingerprint combined with statistical approach could be a good supplementary method for the traditional morphology-based taxonomy identification.

Authentication of Schisandra chinensis and Schisandra sphenantherae in Chinese patent medicines by pyrolysis-gas chromatography/mass spectrometry and fingerprint analysis

Authentication of Schisandra chinensis fruits (S. chinensis fruits) and Schisandra sphenantherae fruits (S. sphenantherae fruits) used in Chinese patent medicines (CPMs) was investigated by pyrolysis-gas chromatography coupled with fingerprint analysis on the basis of the lignan components. 0.3 mg powder of CPM sample was pyrolyzed in a vertical microfurnace pyrolyzer at 400 °C, and the products were directly introduced into a gas chromatograph equipped with a flame ionization detector or a mass spectrometer. Then, each sample was analyzed by the relative peak area of 12 lignan components in thus obtained pyrogram. The pyrogram fingerprints of 16 CPM samples containing S. chinensis fruits or S. sphenantherae fruits showed good reproducibility with the relative standard deviations (RSDs) of the retention time less than 0.15% (n = 5) and the RSDs of the relative percent of peak areas less than 5.29% (n = 5). Furthermore, the discrimination of different Schisandra fruits in CPM samples was achieved by principle component analysis (PCA) and hierarchical cluster analysis (HCA) via recognizing the 18 × 12 data matrix. The results revealed the Py-GC fingerprint combined with chemometric approach is a simple, rapid and selective method for the differentiation of Schisandra fruits used in CPMs.

Rapid Analysis of Fatty Acid Composition in Polysorbate 80 by Gas Chromatography with On-line Pyrolytic Methylation Technique

A novel method of on-line pyrolytic methylation–gas chromatography was developed for the rapid analysis of fatty acid composition in Polysorbate 80 without any tedious pre-treatment steps. Fatty acids in Polysorbate 80 were converted into their corresponding fatty acid methyl esters in the presence of trimethylsulfonium hydroxide with a vertical microfurnace pyrolyzer at 300 °C. The premixing procedure of sample and organic alkali reagent was necessary before the on-line pyrolytic methylation to improve the repeatability. The relative standard deviations for peak areas of fatty acids in Polysorbate 80 were over the range of 0.3–9.1% (n = 5). Six Polysorbate 80 samples, consisting of three samples of pharmaceutical grade and three samples of non-pharmaceutical grade, were analyzed to evaluate the feasibility of the proposed method. The relative percentages (%) of fatty acids for samples of pharmaceutical grade meet the Chinese Pharmacopoeia requirements with the amount of oleic acid varying from 78.4 to 89.3%. On the other hand, the relative percentages (%) for palmitic acid and stearic acid in samples of non-pharmaceutical grade were out of the specification limits, with the amount of oleic acid varying from 62.0 to 63.5%. The quantitative results determined by on-line pyrolytic methylation were in agreement with those obtained by off-line methylation. The result proved that gas chromatography with on-line pyrolytic methylation technique is of great value for rapid screening analysis of Polysorbate 80 samples in bulks.

Discrimination of the Traditional Chinese Medicine from Schisandra Fruits by Flash Evaporation-Gas Chromatography/Mass Spectrometry and Fingerprint Analysis

Flash evaporation-gas chromatography/mass spectrometry (FE-GC/MS) with 0.3 mg sample powder in a vertical microfurnace pyrolyzer at 300 °C was applied to analyze Schisandra fruits without any tedious pretreatment. In total, 80 compounds, 74 compounds of which were identified, were observed, including low-molecular-weight compounds, essential oils (especially terpenoids), fatty acids and esters, and lignans, with the relative standard deviations (RSDs) of the relative percent of peak areas less than 7.79 % (n = 5). 32 compounds of terpenoids and lignans were selected as fingerprint components, since they are the main bioactive constituents in Schisandra fruits. The standard characteristic fingerprints of S. chinensis fruits and S. sphenantherae fruits were established, based on the 32 fingerprint components of 11 genuine S. chinensis fruit samples and 9 genuine S. sphenantherae fruit samples. The discrimination of samples from different growing places was achieved by principle component analysis and hierarchical cluster analysis. Furthermore, a similarity evaluation method was developed to evaluate the quality of each Schisandra fruit sample on the basis of the 32 fingerprint components. The results proved that the FE-GC fingerprint combined with a chemometric approach is a simple, rapid, and effective method for the origin discrimination and quality control of Schisandra fruits.

A novel analytical pyrolysis device applicable for measurements of less volatile pyrolyzates

A novel analytical pyrolysis device suitable for the measurements of the less volatile pyrolyzates was developed. This device is comprised of a pyrolysis unit based on the vertical microfurnace pyrolyzer and a movable pyrolysis tube made of stainless steel. The upper side of the pyrolysis tube is first set at the heated center of the pyrolysis unit. A polymer sample in a sample cup is introduced into the heated center and pyrolyzed under the flow of nitrogen carrier gas. The pyrolyzates are then transferred to the bottom side of the pyrolysis tube which is cooled down by air blow and the less volatile pyrolyzates are condensed. After that the pyrolysis tube is moved down out of the pyrolysis unit and blocked from the hot zone by moving the three port valve. Finally the trapped pyrolyzates are flushed by an appropriate solvent into a collection vial. The recovered pyrolyzates in the solution can be then subjected to the measurements suitable for less volatile products such as matrix-assisted laser desorption/ionization mass spectrometry. Moreover, this device is also on-line connected to the injection port of a high performance liquid chromatographic system, which is also appropriate for the measurements of oligomeric products. The basic performance of the developed device was tested by using some polymer samples forming less volatile pyrolyzates such as poly(butylene terephthalate) and poly(2,6-dimethyl-1,4-phenylene ether). In addition, the usefulness of this method was demonstrated through the characterization of the crosslinking sequences in a photocured resin combined with the thermally-assisted hydrolysis and methylation reaction.

Characterization of Chinese crude propolis by pyrolysis–gas chromatography/mass spectrometry

A method for analysis of Chinese crude propolis was developed by pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS) with a vertical microfurnace pyrolyzer. Propolis sample powder about 0.1mg was pyrolyzed directly at the optimum pyrolytic temperature of 550°C without any time-consuming pretreatments. 76 compounds were identified on the resulting pyrogram after the pyrolysis of crude propolis, and all the compounds were grouped into 8 categories such as flavonoids, terpenoids, acids, esters, hydrocarbons, phenols and alcohols, aldehydes and ketones, and others. On the basis of peak areas, the relative intensities of 76 peaks were precisely determined with the relative standard deviations (RSDs (%), n=3) between 1.1 and 14.0%. Furthermore, the compositions of crude propolis samples from different geographical regions in China were analyzed and compared. The contents of 8 categories of compounds in crude propolis samples were different, the predominant categories being flavonoids, esters or hydrocarbons. And also the contents of main bioactivity compounds such as flavonoids and terpenoids were extremely different, and varied largely with 0–54.9% and 0.6–21.6%, respectively. In addition, abundant triterpenoids were identified in Chinese propolis for the first time. It is proved that Py–GC/MS is a simple, rapid and sensitive method for the characterization of the crude propolis.

Development of a new micro reaction sampler for pyrolysis-GC/MS system facilitating on-line analytical chemolysis of intractable condensation polymers

A new micro reaction sampler is developed to facilitate the thermally assisted hydrolysis and methylation (THM) reaction of intractable condensation polymers, at an elevated temperature in a sealed glass capsule under high pressure. The sampler is integrated with a glass capsule and a crushing metal rod, and it is air-tightly mounted inside a vertical micro-furnace pyrolyzer of a pyrolysis (Py)-GC/MS system. The developed sampler is firstly applied for THM-GC/MS measurements of polycarbonate (PC) whose structural characterization using tetramethylammonium hydroxide (TMAH) as a reagent has been reported in detail previously, to confirm the applicability of the developed sampler. Two peaks are clearly observed in the pyrogram and they are assigned to methyl derivatives of a main chain unit (bisphenol A) and a terminal group (tert-butyl phenol) which are the THM reaction products of PC. The area ratio of these two peaks is almost the same as that obtained by the conventional THM-GC/MS, suggesting the effectiveness of the developed reaction sampler. Further, the developed sampler is applied for THM of nylon 6.6 which has been hardly analyzed by conventional THM-GC/MS using TMAH as a reagent in the open system where samples are exposed to the ambient gas in a pyrolyzer. Using the developed method, measured pyrogram clearly shows several peaks with fairly high yields that are assigned to methyl derivatives of monomer units of nylon 6.6, that is, adipic acid and hexamethylenediamine, and a hybrid dimer of each monomer. Therefore, it can be said that the developed sampler based on the closed system, sealed glass capsule, is quite useful for the pyrolysis analysis of intractable condensation polymers such as nylon 6.6, compared to the conventional THM-GC/MS using the open system.

Validation of Thermally Assisted Hydrolysis and Methylation–Gas Chromatography Using a Vertical Microfurnace Pyrolyzer for the Compositional Analysis of Fatty Acid Components in Microalgae

Thermally assisted hydrolysis and methylation-gas chromatography (THM-GC) in the presence of trimethylsulfonium hydroxide, using a vertical microfurnace pyrolyzer, was validated for the compositional analysis of fatty acid components in microalgae. The chromatograms of a microalga, Pavlova lutheri , obtained under optimized THM conditions clearly showed a series of fatty acid methyl esters including thermally labile polyunsaturated fatty acid components. On the basis of these peak areas, their chemical compositions were rapidly determined without using any tedious sample pretreatment with a precision of <8% relative standard deviation. Moreover, the compositions thus obtained were in good agreement with those obtained by the conventional technique involving solvent extraction. Finally, the THM-GC technique was applied for the compositional analysis of fatty acid components in a newly found microalga, Coccomyxa gloeobotrydiformis . The obtained data showed a high abundance (24 mol %) of α-linolenic acid components, suggesting its potential usefulness as feed sources and/or functional foods.

Application of pyrolysis-gas chromatography and hierarchical cluster analysis to the discrimination of the Chinese traditional medicine Dendrobium candidum Wall. ex Lindl.

The pyrogram fingerprints of Dendrobium candidum Wall. ex Lindl. samples from 3 different growing places and 2 other different species were analyzed on the basis of pyrolysis-gas chromatography. An amount of 0.4 mg of sample powder was pyrolyzed in a vertical microfurnace pyrolyzer at 450 °C, and the products were directly introduced into a gas chromatograph equipped with a flame ionization detector or a mass spectrometer. Then, each sample was characterized by the relative peak area of 40 peaks in thus obtained pyrogram. The pyrogram fingerprints of 16 samples from different growing places and species showed good similarity and reproducibility with the relative standard deviations (RSDs) of the retention time less than 0.12% ( n = 5) and the RSDs of the relative percent of peak areas less than 3.77% ( n = 5). Furthermore, the discrimination of the samples from different growing places and species was achieved by hierarchical cluster analysis via recognizing the 16 × 40 data matrix. Thus, the results proved the Py-GC fingerprint combined with chemometric approach is a simple, rapid and selective method which is suitable for the quality control of the raw materials of herbal medicine.

Museum Laboratories: Where Art Meets Science

Museum Laboratories: Where Art Meets Science

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 “flow-through” sample cup for the vertical micro-furnace pyrolyzer to reduce undesirable secondary reactions and band broadening of resulting pyrolyzates

When a vertical micro-furnace pyrolyzer is adopted for pyrolysis-gas chromatography (Py-GC), the sample is usually introduced into the center of the preheated pyrolysis chamber by mounting it in a small cylindrical sample cup with a dead-end bottom having a volume of a few dozens micro liters which in some case might be responsible for a stagnant flow of carrier gas in the pyrolysis chamber to cause undesirable secondary reactions of the resulting pyrolyzates and/or peak broadening phenomenon. In order to quench the dead-end flow, a new “flow-through” sample cup in which a small hole (ca. 1.0 mm i.d.) was drilled through its bottom was developed, and its basic characteristics were first examined by measuring the pyrogram of polycarbonate (PC) at 600 °C under different carrier gas flow rates. Various secondary products such as phenol and p-isopropenyl phenol derived from bisphenol A, the main pyrolyzatate of PC were observed when the conventional sample cup without the hole was used under a relatively lower flow rate as 25 ml/min. However, they were markedly decreased when the “flow-through” sample cup was used. Furthermore, the resolution of the lower boiling point pyrolyzates (C 1–C 8) from high density polyethylene (HDPE) was also much improved by use of the “flow-through” sample cup.

Determination of dihydroxyacetone and glycerol in fermentation broth by pyrolytic methylation/gas chromatography

A method to determine dihydroxyacetone (DHA) and glycerol in fermentation broth was developed on the basis of pyrolytic methylation–gas chromatography (GC) using a vertical microfurnace pyrolyzer. With the on-line pyrolytic methylation in the presence of an organic alkali, tetramethylammonium hydroxide ((CH 3) 4NOH, TMAH), DHA and glycerol were converted into their corresponding methyl ethers. Thus, fermentation broth samples containing DHA and glycerol could be well determined simultaneously by this pyrolytic methylation–GC without using any pretreatment procedures. Important factors such as reaction temperature, the amount of TMAH to DHA and glycerol were investigated in order to obtain the optimum methylation conditions. Thus, obtained results showed that 0.4 μl 25% TMAH aqueous solution at 400 °C enabled the highly sensitive determination of DHA and glycerol contained in 0.2 μl aqueous samples. The achieved calibration curves exhibit good linearity with regression coefficients of 0.996 and 0.998 for DHA and gelycerol at the concentration range from 1 to 100 g/l, respectively. The precision was quite high with the R.S.D. within 5.0% for DHA at 30 g/l and glycerol at 15 g/l concentration levels, and the limit of detection reached 0.016 g/l. The potential of the proposed method was assessed by applying it to determination of both the analytes in fermentation broth during the bioconversion of glycerol to DHA by Acetobacteria sp. The results proved that this on-line pyrolytic methylation–GC technique was a rapid, convenient and highly sensitive method for monitoring the bioprocesses of DHA.

Rapid and sensitive determination of morphine in street opium samples by thermal desorption gas chromatography using a microfurnace pyrolyzer.

Thermal desorption of the alkaloids in opium samples at 300 degrees C using a vertical microfurnace pyrolyzer was followed by their on-line gas chromatographic (GC) analysis on a large-bore glass capillary column. This method permitted rapid and sensitive determination of the content of the main alkaloid, morphine, in the small (ca. 100 microg) opium samples with a relative standard deviation within 4% for 5 runs. The observed morphine contents of about 12 to 15 w/w% in the given opium samples were in fairly good agreement with those estimated by a conventional GC-MS method.

Quantitative and discriminative analysis of carnauba waxes by reactive pyrolysis-GC in the presence of organic alkali using a vertical microfurnace pyrolyzer

Reactive pyrolysis gas chromatography (reactive Py-GC) using a vertical microfurnace pyrolyzer was applied to quantitative and discriminative analysis of carnauba waxes. Pyrolysis of the wax samples in the presence of an organic alkali, tetramethylammonium hydroxide (TMAH) allowed almost quantitative recoveries of their constituents including long chain fatty acids, hydroxy acids, higher alcohols and diols, and cinnamic acids as well-resolved peaks on the resulting pyrograms. On the basis of the relative intensities of these peaks, chemical composition of the carnauba waxes was determined with less than 2% relative standard deviations without using any tedious sample pretreatment. Furthermore, discrimination of the carnauba waxes collected from the leaves at two different growing stages was achieved by use of the principal component analysis carried out on the basis of chemical composition of the waxes obtained by reactive Py-GC.

Discriminative analysis of Eucalyptus camaldulensis grown from seeds of various origins based on lignin components measured by pyrolysis-gas chromatography

Pyrolysis-gas chromatography (Py-GC) using a vertical microfurnace pyrolyzer combined with the principal component analysis (PCA) was applied to the discriminative analysis of Eucalyptus camaldulensis trees grown at the same field from the seeds of different origins. On the pyrograms of the Eucalyptus samples obtained at 450°C, many characteristic peaks derived from syringyl (S) and guaiacyl (G) units of lignin were reproducibly observed along with those derived from cellulose and hemicellulose. First, the discriminative analysis among the Eucalyptus trees was attempted on the basis of the S/G ratio calculated from the relative peak intensities of the pyrolyzates characteristic to lignin. However, it was difficult to make unequivocal specification for the origins of the seeds by the observed S/G ratio alone. Then, the PCA was applied to discriminate Eucalyptus tree samples based on the molar yields of the peaks specifically derived from lignin observed by Py-GC. As a result, the origin of Eucalyptus trees was successfully discriminated even grown at the same field.

Characterization of within-tree variation of lignin components in Eucalyptus camaldulensis by pyrolysis–gas chromatography

Pyrolysis–gas chromatography (Py-GC) using a vertical microfurnace pyrolyzer was applied to the precise determination of the ‘within-tree variation’ of the ratio of syringyl and guaiacyl units (S/G ratio) for lignin in Eucalyptus camaldulensis. On the pyrogram of the Eucalyptus obtained at 450 °C, many characteristic peaks derived from syringyl and guaiacyl units of lignin were reproducibly observed, together with those from cellulose and hemicellulose. On the basis of the relative intensities of those characteristic peaks relating to the syringyl and guaiacyl units, the ‘within-tree variation’ of the S/G ratio was determined precisely in about 1 h using only about 0.1 mg of the powdered wood sample with a 2% relative standard deviation. The results obtained were also compared with those obtained by the thioacidolysis method.

Determination of triazolam in a drug tablet by thermal desorption gas chromatography

Thermal desorption gas chromatography using a vertical microfurnace pyrolyzer was applied to determine the amount of triazolam in a tablet sample. About 1 mg of ground tablet was directly subjected to analysis without any preconcentration. When the sample was heated at 300°C, triazolam desorbed from the powder was observed as a completely isolated peak in a chromatogram together with some additional peaks formed from the main components of the tablet through pyrolysis and/or thermal desorption. The correlation coefficient of the calibration curve obtained by use of pure triazolam ranging from 2.4 to 10.5 μg was 0.999. Triazolam in the tablet sample (about 3 μg/mg) could be determined using the calibration curve. The relative standard deviation of this method was 2.4% for four runs.