Temperature fused-silica capillary columns

For routine separations, there are about a dozen useful phases for capillary columns. The best general-purpose columns are the dimethylpolysiloxane (DB-1 or equivalent) and the 5% phenyl, 95% dimethylpolysiloxane (DB-5 or equivalent). These relatively nonpolar columns are recommended because they provide adequate resolution and are less prone to bleed than the more polar phases. If a DB-1, DB-5, or equivalent capillary column does not give the necessary resolution, try a more polar phase such as DB-23, CP-Sil88, or Carbowax 20M, providing the maximum operating temperature of the column is high enough for the sample of interest. See Appendix 3 for fused silica capillary columns from various suppliers. 

The use of a fused silica capillary column for the GC analysis of the neutral oil extract has provided the means for improving the resolution of components in a more inert system. The sultones are determined by temperature-programmed GC over CP-Sil-5 CB (methyl silicone fluid) in a 25 m x 0.2 mm fused silica capillary column using nonadecane as internal standard. A sample split ratio of 1 100 is recommended for a 3-pl injection. 

Chromatography Hewlett-Packard Ultra2 (25 m x 0.33 mm) cross-linked phenyl methyl silicone fused silica capillary column. Temperature program 55° (1 min.) -I- 30°C/min. to 180°C, and 4°C/min. to 320°C. 

Early work relied on the use of packed columns, but all modern GC analyses are accomplished using capillary columns with their higher theoretical plate counts and resolution and improved sensitivity. Although a variety of analytical columns have been employed for the GC of triazine compounds, the columns most often used are fused-silica capillary columns coated with 5% phenyl-95% methylpolysiloxane. These nonpolar columns in conjunction with the appropriate temperature and pressure programming and pressure pulse spiking techniques provide excellent separation and sensitivity for the triazine compounds. Typically, columns of 30 m x 0.25-mm i.d. and 0.25-qm film thickness are used of which numerous versions are commercially available (e.g., DB-5, HP-5, SP-5, CP-Sil 8 CB, etc.). Of course, the column selected must be considered in conjunction with the overall design and goals of the particular study. 

Oxyfluorfen column, fused-silica capillary column coated with cross-linked methyl silicone (25 m x 0.3-mm i.d., 0.52- am film thickness) temperature, column 200 °C (1 min), 10°Cmin to 250 °C (5 min), inlet and detector 250 and 300 °C, respectively gas flow rates, N2 carrier gas 30mLmin , N2 makeup gas 30mLmin H2 3.5mLmin" air llOmLmin injection volume, 2 p.L. ... 

Chromatographic columns (glass with stopcock and solvent reservoir, 10-mm i.d.) Fused-silica capillary column, DB-1701, 60 m x 0.32-mm i.d., O.lS-qm film thickness (14% cyanopropylphenyl)methylpolysiloxane Varian 3400 gas chromatograph equipped with a temperature-programmed SPI injector, a Varian 8100 autosampler, and a Varian Saturn II lontrap mass spectrometer Centrifuge vials, 10- and 250-mL Evaporation flasks, 100- and 250-mL Separatory funnel, 250-mL... 

The extracted fractions were esterified with either BF3-MeOH reagent or diazomethane and analyzed by GLC. Gas liquid chromatography (GLC) was conducted with a Perkin-Elmer Sigma 3 equipped with flame ionization detector. Separations were obtained on a Hewlett Packard 12 m x 0.2 mm i.d. capillary column coated with methyl silicon fluid (OV-101). The temperature was maintained at 80°C for 2 min then programmed from 80 to 220°C at 8°C/min. The injector temperature was 250°C. Mass spectra were obtained on a Hewlett Packard model 5995 GC-MS mass spectrometer, equipped with a 15 m fused silica capillary column coated with 5% phenyl methyl silicone fluid. Spectra were obtained for major peaks in the sample and compared with a library of spectra of authentic compounds. 

Gas chromatography of the soil extract was carried out on a Varian 3700 instrument equipped with a flame ionization detector and a fused silica capillary column (25in, 0.25mm i.d.) coated with CP-SIL 5. Samples were injected spitlessly, and nitrogen was used as a carrier gas. The oven temperature was programmed from 40°C (5min) to 300°C at 5°C/min. 

Analysis was performed on a 25-m fused silica capillary column with DX-3 (polymethylsiloxane) stationary phase and a temperature program from 50°C-150°C. 

The solution, 10 pL, prepared as outlined in Note 18 was loaded an a Chirasil-Val fused-silica capillary column of Machery-Nagel (25 m, 0.4 mm) in a Carlo-Erba-Fraktovap 4160 HR GC. After 5 min at 160°C, the column temperature was increased by 2°C per min up to 200°C. 

All aldehydes used in the experiment were freshly distilled or washed with aqueous NaHC03 solution to minimize the amount of free acid. Chiral HPLC was performed using a chiral OJ-H column (0.46 cm x 25 cm, Daicel industries) with a water 717 auto sampler and a UV-vis detector (254 nm). The eluting solvent used was different ratios of hexane and 2-propanol. Chiral gas chromatography analysis was performed in a Shimadzu auto sampler with cyclodextrins columns as chiral stationary phase (fused-silica capillary column, 30 m X 0.25 mm x 0.25 gm thickness, /3-Dex-120 and /3-Dex-325 from Supelco, USA) using He as a carrier gas (detector temperature 230 °C and injection temperature 220 °C). 

For chiral analyses the GC system was equipped with a Marcherey 212117/91 Hydrodex-/ 3P fused-silica capillary column. The oven temperature was... 

For qualitative analyses, the GC system was equipped with a J W Scientific HP-5 or a Supelco Simplicity 1 fused-silica capillary column. Injector and detector temperatures were set at 220 °C and 240 °C respectively the oven temperature was programmed from 60 to 230 °C at 40 °C min V Helium was employed as carrier gas (1 mL min ). Compound identification was based on a comparison of mass spectra with those of synthetic racemic and enantiomeric-enriched samples. The retention times for tetralin, 1-tetralol and 1-tetralone were 5.6 min, 6.5 min and 6.6 min respectively. 

The derivatized samples were analyzed on a Hewlett-Packard 5890 series IIGC (helium carrier gas) coupled to a Hewlett-Packard 5971 mass-selective detector (MSD). A 60 m, 0.32 mm i d., 0.25-im film, SE-30 fused silica capillary column (J W Scientific, Folsom, CA) was installed in the GC, and an on-column injector (SGE model OCl-3) held at ambient temperature was fitted to the colunrn inlet. Samples (0.5 p,L) were injected directly into the column held at 105°C... 

Determination of CholesteroL For meat extraction, the procedures for determining the cholesterol of extracted lipid samples were described Chao et al. (2i). For edible beef tallow extraction, the preparation of samples for cholesterol content was based on the AOAC (22) method Section 28.110. The prepared sample was then injected into a Supelco SPB-1 fused silica capillary column of 30 meters x 032 mm i.d. in a Varian Model 3700 gas chromatograph equipped with dual flame ionization detectors. The initial holdup time was 4 min at 270°C and then programmed to a temperature of 300°C at a ramp rate of 10°C/min. Helium flow rate and split ratio were 13 ml and 50 1, respectively, while the injector/detector temperature was 310°C. 

The GC was calibrated using a mixture of known quantities of d-limonene, d-limonene oxide (cis and trans), 2-octanone, and carvone. GC analyses were performed by injecting 1 pi samples with 1 40 split (column flow split flow), into a Hewlett-Packard 5840A GC equipped with a flame ionization detector. A fused silica capillary column 50m x 0.25 mm i.d., coated with OV-101 as a liquid phase was used. Column temperature was programmed from 50-250 C at 10 C/min, and helium was used as the carrier gas. 

SFC chromatographs represent hybrids between GC and HPLC instruments (Fig. 6.4). In order to deliver the supercritical fluid, syringe pumps or reciprocal pumps are used and maintained above the critical temperature using a cryostat regulated at around 0 "C. In instances where an organic modifier is used, a tandem pump is employed which has two chambers, one for the critical fluid and one for the modifier. The liquid then passes through a coil maintained above the critical temperature so that it is converted into a supercritical fluid. Stainless steel packed columns like those used in HPLC (1 to 4 mm in diameter) or fused silica capillary columns like those used in capillary GC (2 to 20 m in length, internal diameters as low as 50 pm and stationary phase film thickness of at least 1 pm) are used in SFC. 

Pyrolysis GC-MS Analysis. Flash pyrolysis was performed by using a pyroprobe 100 (Chemical Data Systems) temperature-control system. Samples were pyrolyzed from 150 to 750 °C with a temperature program of 20 °C/ms and a final hold for 20 s. After pyrolysis, the fragments were separated on a 25-m CP WAX 57 fused silica capillary column (temperature program 25-220 °C at 3 °C/min), followed by MS on a R 10-10 C (Ribermag, Rueil-Malmaison, France) operated at 70 eV and scanned from 20 to 400 m/z. 

Standards with a poor UV chromophore (4-methyl-2-pentanone, 1-chlorododecane, and stearic acid) were analyzed on a Perkin-Elmer 3920 gas chromatograph with a flame ionization detector and a 30-m SE-54 wall-coated open tubular (WCOT) fused-silica capillary column (J W Scientific). The injector temperature was 200 °C the detector interface temperature was 280 °C. The carrier gas was He at 16.5 lb/in.2, and the makeup gas was nitrogen at a flow of 40 cm3/min. Splitless l-/zL injections of the 25,000 1 concentrates were made by starting with an oven temperature of 45 °C and the oven door open after 2.75 min, the oven door was closed and the temperature was programmed at 4 °C/min to 280 °C, which was held for 8 min. The syringe was kept in the injection port for 15 s after injection. 

A 500-L solution containing 2 mg/L of free chlorine residual in distilled water was pumped onto the four-column system the columns were eluted and the eluants were processed as described earlier. This chlorine blank and resin eluant blanks were analyzed by GC-MS by using a Finnigan 4023 with the I NCOS data system and a 31,000-compound National Bureau of Standards library. Electron impact spectra were obtained by using an electron energy of 70 eV and a scan time of 1 s for the mass range 33-550 amu. A 30-m WCOT SE-54 fused-silica capillary column (J W Scientific) was used for separations. Injections were made with the oven at 40 °C and the door open, the injector at 220 °C, and the interface at 270 °C. Two minutes after injection, the door was closed and the temperature was raised ballistically to 60 °C, ramped at 4 °C/min to 280 °C, and held there for 4 min. The split and septum purge valves were closed for injection and opened after 1 min. 

Figure 2. Chromatograms typical of a, an urban environment. GC conditions 30-m DB-1 fused silica capillary column oven temperature -50 to 100 °C at 4 °C/min. Continued on next page.

Figure D1.2.2 Sample GC chromatogram of the FAME from butter fat (Sweet Cream Butter, Wisconsin Grade AA, Roundy s, Milwaukee, Wise.) prepared using the sodium methoxide method (see Basic Protocol 2). Equipment DB-23 fused silica capillary column, 30 m x 0.32 mm i.d., 0.25 pm film thickness, FID detector. Temperature, injector 225°C detector 250°C. Column (oven) temperature program 100°C initial, hold 4 min, ramp to 198°C at 1.5°C/min, hold 10 min. Total run time was 80 min. Split injection.

Heat the sample for 30 min at 30°C while purging helium at a rate of 25 ml/min. Collect volatile compounds on the trap (packed with Tenax or equivalent) and thermally desorb at 180°C onto a 30-m x 0.32-pm i.d. x 1-pm film thickness fused-silica capillary column. After desorption is complete, hold the initial temperature for 1 min at -20°C and then program the temperature to ramp to 220°C at 6°C/min. Set the injector and the detector temperatures at 260°C and 280°C, respectively. Use helium as carrier gas at a flow rate of 3.0 ml/min and a split ratio of 20 1. 

Capillary column Fused silica capillary column, such as RTX-5, DB-5, SPB-5, or equivalent, 15 m x 0.53 mm ID x 1.5 pm film (direct injection) at 40° to 240°C at H2 carrier gas linear velocity 80 cm/s (or flow rate 10 mL/min). A longer column 30 m with smaller ID and lesser film thickness may be used with spht injection. Temperature and carrier gas flow conditions may be set accordingly. 

GC Analysis. GC analyses were performed on a Hewlett-Packard 5880 gas chromatograph equipped with a 60 m x 0.25 mm I.D. fused silica capillary column coated with a 0.25 ym film of SE-52. From an initial value of 40°C, the column temperature was programmed at... 

Conventional high pressure NICI spectra were obtained using a Hewlett-Packard 5985B quadrupole GC/MS, as described previously (1). Methane was used as the Cl reagent gas and was maintained in the source at 0.2-0.4 torr as measured through the direct inlet with a thermocouple gauge. A 200 eV electron beam was used to ionize the Cl gas, and the entire source was maintained at a temperature of 200° C. Samples were introduced into the spectrometer via the gas chromatograph which was equipped with a 25 meter fused silica capillary column directly interfaced with the ion source. For all experiments, a column coated with bonded 5% methyl phenyl silicon stationary phase, (Quadrex, Inc.) was used and helium was employed as the carrier gas at a head pressure of 20 lbs. Molecular sieve/silica gel traps were used to remove water and impurities from the carrier gas. 

Reineccius and Liardon [207] studied volatiles evolved from heated thiamine solutions. Samples of 2% thiamine hydrochloride in various 0.2M buffers were heated under various conditions. A temperature of 40°C and a sampling time of 45 min were found to minimize artifact formation and yet produce sufficient volatiles for analysis. Nitrogen was used as the purge gas at a flow rate of 50 ml/min. Several materials were evaluated as absorbents, with graphite found to be the optimum. A microwave desorption system was used to rapidly desorb the trapped volatiles onto a fused silica capillary column. Twenty-five compounds were identified in the headspace of the heated thiamine solutions. 

A GS-MS method for the analysis of etodolac in human plasma has been developed [16]. Plasma samples were spiked with meclofenamic acid (the internal standard), acidified with 5N HC1, and extracted twice with chloroform / dichloromethane / hexane (50 25 25, v/v). The organic phase was evaporated, the residue methylated with ethereal diazomethane, dried again, and reconstituted in hexane. Analytical separation was performed on a 15 m x 0.24 mm i.d., 0.25 pm film thickness, fused silica capillary column. The oven temperature was variable (150 to 260°C) and the injector was at 260°C. The carrier gas was helium at 1 mL/min. Mass spectra were obtained using positive electron impact ionization (70 eV) at m/z 228 for etodolac. The method was linear in the 1-10 ng/mL (low) and 10-100 ng/mL (high) concentration range. The detection limit was 0.5 ng/mL in plasma, and recovery of etodolac from plasma sample exceeded 92%. 

The effect of temperature on retention was studies using n-hexadecane on a 20 m, 50ji I.D. fused silica capillary column coated with an OV-17 phase using FID detection. The OV-17 was cross-linked in-situ to decrease its solubility in the supercritical fluid. The stationary phase film thickness was calculated to be 0.25pm. The... 

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