Application of a monolithic silica capillary adsorbent for the preconcentration of airborne trichloroethylene and tetrachloroethylene

Monolithic silica with a bimodal pore structure was prepared in a fused silica capillary by the sol-gel process and investigated as an adsorbent for the preconcentration of airborne trichloroethylene and tetrachloroethylene. The airborne trichloroethylene and tetrachloroethylene are adsorbed when they flow through the silica capillary column and can be desorbed by liquid hexane followed by GC/MS analysis. The monolithic silica adsorbent is mechanically stable and no frits or other special structures are needed to retain them in place. In addition, owing to the smaller size of the capillary column, only a small volume of desorption solvent is needed. The present investigation demonstrates the satisfactory applicability of monolithic silica as a capillary adsorbent.     

Fused silica capillary GC/MS coupling: A new,innovative approach

A novel fused silica capillary GC/MS direct coupling is described which ensures quantitative transfer of sample from the point of injection to the ion source of a mass spectrometer without contacting any surfaces other than the column wall. This device permits GC analysis of highly labile substances. Aflatoxin B₁, previously considered unassayable by GC, can now be determined by GC/MS.     

Detection of PAH of molecular weight between 300 and 402 in airborne particulate matter by fused silica capillary GC and GC/MS

Gas chromatography (GC), low-voltage mass spectrometry (LV MS), and gas chromatography/mass spectrometry (GC/MS) have been used for detecting polycyclic aromatic hydrocarbons (PAH) of molecular weight between 300 and 402 in airborne particulate matter. Nearly 200 high molecular PAH separated by fused silica capillary columns could be characterized by their El mass spectra. The lack of reference substances precluded further structure elucidation.     

GC/MS characterization of urinary metabolites of doxylamine succinate: Identification of the aglycones formed from intestinal microflora metabolism of the polar glucuronide metabolites

This study describes the use of high performance liquid chromatography (HPLC) and capillary gas chromatography/mass spectrometry (GC/MS) in the characterization of polar glucuronide conjugates of doxylamine and their subsequent aglycones following deconjugation. Rat urinary extracts which contained doxylamine and both nonconjugated and conjugated doxylamine metabolites, were examined by HPLC before and after incubation with rat intestinal microflora. The subsequent deconjugated urinary metabolites and the nonconjugated products remaining in the urinary extracts were then isolated, acetylated, and assayed by GC/MS. Incubation with the intestinal microflora indicated that anaerobic bacteria were capable of effecting hydrolytic cleavage of these polar O-glucuronide metabolites of doxylamine and its demethylated products to their subsequent aglycones. GC/MS analysis was performed using a fused silica DB-5 GC column and was utilized for the identification of these deconjugated metabolites.     

High speed analysis of underivatized drugs by gas chromatography–mass spectrometry

The technique of choice for many types of forensic drug confirmations is gas chromatography/mass spectrometry (GC/MS). Significant amounts of analytical time can be involved in a GC/MS run. The use of a 0.1 mm i.d. fused silica capillary column with hydrogen carrier gas can significantly increase the speed of an analysis without sacrificing resolution. Nanogram levels of underivatized drugs, from amphetamine to strychnine, can be eluted in less than twelve minutes. The multitasking system permits data acquisition, while performing data reduction on the previous run.     

Simultaneous determination of two serine proteinases by hydrophobic interaction chromatography

Summary An LC clean-up procedure based upon a complexation between polycyclic aromatic hydrocarbons (PAHs) and silica with chemically bonded 2,4-dinitroaniline has been combined with GC/MS. The LC pre-separation makes it possible to obtain a relatively clean fraction of PAHs free from alkanes, alkylbenzenes and naphthalenes, PCBs, chlorinated pesticides and many other interfering compounds. This fraction has been analyzed using capillary GC and mass selective detector (MSD). Substantial improvement of the MS spectra of PAHs with three or more fused benzene rings is achieved.     

Effects of Permeation of Helium through the Walls of Fused Silica Capillary GC Columns

Hold-up times and peak widths have been measured in long fused silica GC capillary columns at high temperature with helium as the carrier gas. The results lead to the conclusion that the helium permeates through the column walls. The conventional Poiseuille theory of carrier gas flow has been extended to include this phenomenon. The resulting “loss modified Poiseuille” model, which uses literature values for the permeability of fused silica to helium, has been used to simulate the observed behavior. Good agreement between simulation and experiment validates the model. Simulations have been used to explore the effect of column permeability on hold-up times, peak widths, and velocity profiles over a broad range of column geometries.     

Fused silica capillary column GC/MS for the analysis of priority pollutants

Operational characteristics have been determined for fused silica capillary column (FSCC) GC/MS as applied to “extractable” priority polutants. Chromatographic data show excellent relative retention time (RRT) intralaboratory precision and interlaboratory accuracy when multiple internal standards are empolyed. Potential chromatographic problems, such as column overload and “double peaking”, are addressed. Response factor relative standard deviations (RSD) at 50 ng for most of the extractable priority pollutants over the long term indicated precise determination (i.e. RSD generally ≤ 10%). Linearity was demonstrated over two orders of magnitude for FSCC GC/MS analysis of compounds with relatively low and high RF (response factor) values. Potential quantitative problems, such as saturation, are discussed. For certain aromatic priority pollutants interlaboratory RF agreement was observed. This was noted as perhaps the most important property of FSCC GC/MS analysis when the multiple internal standard approach is utilized. Determinations of extractable priority pollutants are directly compared for paced column GC/MS and FSCC GC/MS analysis of separate and composited extracts. For six extracts analyzed in triplicate, the latter configuration was shown to produce more consistent results. In view of the superior analysis logistics of composite extract FSCC GC/MS analysis, this approach was established as the preferred method for the analysis of priority pollutants classified as extractable.     

用台式色谱-质谱仪同时进行原油芳烃色谱和色谱-质谱分析

 摘要：用HP6890GC/5973MSD仪器,一次进样同时测定原油、烃源岩抽提物中芳烃馏分的芳烃色谱和色谱-质谱信息,效果良好,在有机地球化学研究工作中很有实用价值,方法具有高效、经济等优点。     

用台式色谱-质谱仪同时进行原油芳烃色谱和色谱-质谱分析

用ＨＰ６８９０ＧＣ／５９７３ＭＳＤ仪器,一次进样同时测定原油、烃源岩抽提物中芳烃馏分的芳烃色谱和色谱－质谱信息,效果良好,在有机地球化学研究工作中很有实用价值,方法具有高效、经济等优点。     

Simplifying the setup for vacuum‐outlet GC: Using a restriction inside the injection port

The application of vacuum GC has several advantages over pressurized GC. One of the key characteristics is that the optimal gas velocity is very high. Combined with short capillary columns of wide internal diameter, this results in short analysis times using standard GC‐MS equipment. To make vacuum GC possible using a GC‐MS system, a restriction must be positioned at the injection side of the column. This restriction is usually made of deactivated 0.1 mm i.d. fused‐silica tubing which is coupled to the analytical column. Such restrictions will work, but practical challenges are found in coupling, reducing dead volume and robustness. A new way of making restrictions is by incorporating the restriction into the injection port. Using well‐defined short pieces of fused silica with internal diameter of 0.025 mm, one can make a restriction using a Press‐Tight® type connector, and position this inside the injection port. By doing this, the restriction is very short and at high temperature all the time. Activity plays a minimal role, and also leaks will not be an issue as the coupling is in 100% inert gas. Data obtained using this concept is promising as vacuum GC becomes easier and more robust.     

双活性官能团冠醚固定相的合成及毛细管柱的研制

本项研究合成了一种新的气相色谱固定相：３－端烯丙基－不对称二苯并１４－冠－４－二羟基冠醚。其结构经元素分析、红外光谱、核磁共振及质谱的数据证实。将这种固定相涂渍在弹性石英毛细管内,测定其柱效、热稳定性、平均极性及选择性。结果表明：该固定相具有良好的色谱特性,对某些极性位置异构体有着良好的选择性。     

GC/MS分析羰基化产物萘普生甲酯

α－（6-甲氧基-2-萘基）-乙醇在催化剂的作用下,与甲醇和CO发生羰基化反应,一步生成α－（6-甲氧基-2-萘基）丙酸甲酯（萘晋生申酯）。应用气相色谱-质谱联用技术,对这个反应过程中生成的各种化合物进行了分析,获得两个中间产物6-甲氧基萘乙烯和1-甲氧基-1-（6'-甲氧基-2'-萘基）乙烷的GC／MS数据资料,为推测该催化反应机理提供了可靠的依据。     

气相色谱-质谱法分析橡苔浸膏中的挥发性化学成分

 用挥发油提取器提取橡苔浸膏中的挥发油,利用气相色谱-质谱法(GC-MS)分析了其中的化学成分,采用GC峰面积归一化法定量,鉴定出24种化合物,共占挥发油总量的83%以上     

Preparation of thermally stable phenylpolysiloxane fused silica capillary columns. Optimization and evaluation of the deactivation by capillary GC and solid state 29Si NMR

The deactivation of fused silica capillary columns with a laboratory-made poly-diphenylvinylmethylhydrosiloxane copolymer has been investigated. The deactivation obtained at different temperatures and reaction times is characterized with a dual column capillary GC system [1]. In parallel, the effect of the silylation temperatures and reaction times on the nature, the structure, and the chemical properties of the deactivation layer has also been studied by solid-state ²⁹Si NMR spoctroscopy. A fumed silica, Cab-O-Sil M5, was used as a model substrate for these spectroscopic studies. The deactivated fused silica capillaries show an excellent thermal stability (up to 400°C), a high resistance to solvolysis, and a minimal interaction to various critical test components. A good wettability of the fused silica capillary columns deactivated with this reagent was confirmed by successful subsequent coating with polysiloxanes with different phenyl contents.     

Parts per quadrillion level ultra-trace determination of polar and nonpolar compounds via solvent-free capillary microextraction on surface-bonded sol-gel polytetrahydrofuran coating and gas chromatography-flame ionization detection

Sol-gel polytetrahydrofuran (poly-THF) coating was developed for high-sensitivity sample preconcentration by capillary microextraction (CME). Parts per quadrillion (ppq) level detection limits were achieved for both polar and nonpolar analytes through sample preconcentration on sol-gel poly-THF coated microextraction capillaries followed by gas chromatography (GC) analysis of the extracted compounds using a flame ionization detector (FID). The sol-gel coating was in situ created on the inner walls of a fused silica capillary using a sol solution containing poly-THF as an organic component, methyltrimethoxysilane (MTMOS) as a sol-gel precursor, trifluoroacetic acid (TFA, 5% water) as a sol-gel catalyst, and hexamethyldisilazane (HMDS) as a deactivating reagent. The sol solution was introduced into a hydrothermally-treated fused silica capillary and the sol-gel reactions were allowed to take place inside the capillary for 60 min. A wall-bonded coating was formed due to the condensation of silanol groups residing on the capillary inner surface with those on the sol-gel network fragments evolving in close vicinity of the capillary walls. Poly-THF is a medium polarity polymer, and was found to be effective in carrying out simultaneous extraction of both polar and nonpolar analytes. Efficient extraction of a wide range of trace analytes from aqueous samples was accomplished using sol-gel poly-THF coated fused silica capillaries for further analysis by GC. The test analytes included polycyclic aromatic hydrocarbons (PAHs), aldehydes, ketones, chlorophenols, and alcohols. To our knowledge, this is the first report on the use of a poly-THF based sol-gel material in analytical microextraction. Sol-gel poly-THF coated CME capillaries showed excellent solvent and thermal stability (>320 degrees C).     

Short Capillary Traps in GC–GC Tandem Systems for Direct Analysis of T2 Mycotoxin in Aqueous Samples

Two-metre long pieces were cut from a 25-m long fused silica GC column with an inner diameter of 300 μm and a film thickness of 1.2 μm 5% phenyl polymetyhylsiloxane and used as traps to extract T2 mycotoxin from aqueous solutions. Water samples were pushed through the traps at various velocities using nitrogen, then rinsed and dried. The traps were installed in a PTV accessory within a GC oven with 5 cm of the outlet outside the oven. The portion of the trap within the oven was heated and the analyte was focused on the short piece outside the oven. The focused solute was then thermally desorbed and separated into another 25-m long capillary column installed in a second GC and directly coupled to the trap outlet (GC–GC tandem system). The recovery of the analyte was nearly quantitative and independent of sample salinity and experimental conditions set in the trapping operation.     

Comparison of series 5 gas chromatography column performances from a variety of manufacturers for separation of chlorinated dibenzo-p-dioxins and dibenzofurans using high-resolution mass spectrometry

An extended study of seven fused silica capillary gas chromatographic (GC) columns has been conducted with regard to separation of international toxic equivalent factor (I-TEF) isomers (tetra- through octa-chlorinated at 2,3,7,8 positions) of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDDs/PCDFs) from closely co-eluted other isomers using high-resolution gas chromatography-high-resolution mass spectrometry (HRGC-HRMS). The data are explicated in mass chromatograms of Series 5 GC columns from a variety of manufacturers (Varian CP-Sil 8 CB LowBleed/MS, Phenomenex ZB-5UMS, Agilent HP-5MS, Restek Rtx-5MS, Supelco Equity-5, J&W Scientific DB-5 and DB-5MS), according to relative retention times, and 2,3,7,8-substituted isomer concentrations for each of the columns tested. Results showed differences between 5% phenyl methyl silicone and 5% silphenylene (Si-arylene) silicone polymer type GC stationary phases in separation of 2,3,7,8-substituted PCDDs/PCDFs from closely co-eluted isomers. The separation differences for Si-arylene type columns resulted in lower toxic equivalence (TEQ) values compared to the siloxane-based columns. Because of differences in product nomenclature and manufacturing practices by various manufacturers, incorrect assumptions and comparisons may be made regarding the interchangeability of these columns for PCCD/PCDF separations. The data presented are the most comprehensive to date and provide a valuable addition to operational criteria for the standard US Environmental Protection Agency methods 1613b and 8290.     

Strategies for compound identification and quantification using fused silica capillary column GC/MS

A test mixture containing 28 compounds plus their stable isotopically labeled analogs was analyzed on a daily basis for one month during a series of routine fused silica capillary column GC/MS analyses in order to establish the precision with which retention times and responses were produced. These long-term precision data were evaluated to determine how to best predict retention times and how to best reproduce quantification. Results clearly indicate that relative retention times should be calculated using the reference compound eluted most closely to the target compound and that quantification should be based on relative response using a chemically “similar” compound.     

Metabotyping of human colorectal cancer using two-dimensional gas chromatography mass spectrometry

Colorectal cancer (CRC) is the fourth most common cause of death from cancer in the world. The limitations of the currently available methods and biomarkers for CRC management highlight the necessity of finding novel markers. Metabonomics can be used to search for potential markers that can provide molecular insight into human CRC. The emergence of two-dimensional gas chromatography time of flight mass spectrometry (GC?×?GC/TOFMS) has comprehensively enhanced the metabolic space coverage of conventional GC/MS. In this study, a GC?×?GC/TOFMS was developed for the tissue-based global metabonomic profiling of CRC. A Pegasus GC?×?GC/TOFMS (Leco Corp., St. Joseph, MI, USA) system comprising an Agilent 7890 GC and Pegasus IV TOFMS was used for this purpose. An Agilent DB-1 (30 m?×?250 μm?×?0.25 μm) fused silica capillary column and a Restek Rxi®-17 (1 m?×?100 μm?×?0.10 μm) fused silica capillary column were used as the primary and secondary columns, respectively. The method was applied for global metabonomic profiling of matched CRC and normal tissues (n?=?63) obtained from 31 CRC patients during surgery. An attempt was also made to compare GC?×?GC/TOFMS with GC/MS and NMR in similar application. The results showed that the metabotype associated with CRC is distinct from that of normal tissue and led to the identification of chemically diverse marker metabolites. Metabolic pathway mapping suggested deregulation of various biochemical processes such as glycolysis, Krebs cycle, osmoregulation, steroid biosynthesis, eicosanoid biosynthesis, bile acid biosynthesis, lipid, amino acid and nucleotide metabolism.

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Fig Workflow of GCGC/TOFMS metabonomic profiling of human colorectal cancer