Stationary phase fused-silica capillary columns

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). 

Gas chromatography (GC) was performed on a Varian Associates Inc. (Palo Alto, CA) model 3700 gas chromatograph equipped with a flame ionization detector (FID) and modified to accommodate a laboratory-made capillary on-column injector (ref. 12). All gas chromatographic separations were carried out on a J W Scientific (Folsom, CA) bonded phase fused silica capillary column (60 m X 0.32 mm ID, DB-1 stationary phase, 0.25 fim film thickness) unless otherwise noted. The GC oven temperature was programmed from 50°C to 300°C at 20°C/min. 

Fused silica capillary columns of various internal bores and of lengths in the range 25 to 50 m are mainly employed for analytical separations. A variety of polar and non-polar column types are available including those open tubular types with simple wall coatings (WCOT), those with coatings dispersed on porous solid-supports to increase adsorbent surface area (SCOT) and porous layer open tubular (PLOT) columns. Important stationary phases include polyethylene glycol, dimethylpolysiloxane and different siloxane copolymers. Various sample introduction procedures are employed including ... 

Fused silica capillary column containing stationary phase... 

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. 

Capillary gas chromatography (GC) using modified cyclodextrins as chiral stationary phases is the preferred method for the separation of volatile enantiomers. Fused-silica capillary columns coated with several alkyl or aryl a-cyclo-dextrin, -cyclodextrin and y-cyclodextrin derivatives are suitable to separate most of the volatile chiral compounds. Multidimensional GC (MDGC)-mass spectrometry (MS) allows the separation of essential oil components on an achiral normal phase column and through heart-cutting techniques, the separated components are led to a chiral column for enantiomeric separation. The mass detector ensures the correct identification of the separated components [73]. Preparative chiral GC is suitable for the isolation of enantiomers [5, 73]. 

The purity of the Dess-Martin periodinane (2) was assayed by treatment of 2 (1 equiv) with an excess of benzyl alcohol (2 equiv) in methylene chloride (CH2CI2) followed by analysis of the reaction mixture for benzaldehyde by capillary vapor phase chromatography (15-m fused silica capillary column, Durawax DX3 stationary phase, 120°C). After correction for response factors, the purity was established to be >95%. 

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. 

The N-alkylation of 2-methyl-6-ethylaniline (MEA) with methoxy-2-propanol (MOIP) was investigated in the same flow microreactor under atmospheric pressure. Feed MEA MOIP = 0.5 (3 ml/h) and hydrogen (4,7 ml/min). The reaction product was condensed in a cooling trap. Each catalyst was tested for 24 h and 7 samples were collected and analyzed separately by GLC on a fused silica capillary column with methylsilicon fluid (Hewlett Packard) as stationary phase. 

To establish chiral separation method for donepezil hydrochloride enantiomers by capillary electrophoresis (CE) and to determine the two enantiomers in plasma [39], alkalized plasma was extracted by isopropa-nol-n-hexane (3 97) and L-butefeina was used as the IS. Enantioresolution was achieved using 2.5% sulfated-beta-cyclodextrin as chiral selector in 25 mmol/1 triethylammonium phosphate solution (pH 2.5) on the uncoated fused-silica capillary column (70 cm x 50 fim i.d.). The feasibility of the method to be used as quantitation of donepezil HC1 enantiomers in rabbit plasma was also investigated. Donepezil HC1 enantiomers were separated at a baseline level under the above condition. The linearity of the response was evaluated in the concentration range from 0.1 to 5 mg/1. The linear regression analysis obtained by plotting the peak area ratio (A(s)/A(i)) of the analyte to the IS versus the concentration (C) showed excellent correlation coefficient The low limit of detection was 0.05 mg/1. The inter- and intra-day precisions (RSD) were all less than 20%. Compared with chiral stationary phase by HPLC, the CE method is simple, reliable, inexpensive, and suitable for studying the stereoseletive pharmacokinetics in rabbit. 

Fused silica capillary columns give better separation than packed columns. Columns having inside diameters of 0.25, 0.32, and 0.53 mm and film thickness between 0.25 and 1 pm have found use in herbicides analysis. The stationary phase is generally made out of phenyl silicone, methyl silicone, and cyanopropyl phenyl silicone in varying compositions. Some common columns are DB-5, DB-1701, DB-608, SPB-5, SPB-608, SPB-1701, Rtx-5, AT-1701, HP-608, BP-608, or equivalent. Use helium as carrier gas flow rate 30 cm/s on narrowbore columns with 0.25 or 0.32 mm ID and 7 mL/min for megabore 0.53 ID columns. 

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. 

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... 

High resolution fused silica capillary columns were used to examine, and in some cases to compare, flavor and aroma essences obtained by 1) direct headspace injection, 2) simultaneous steam distillation extraction, 3) standard Soxhlet extraction using dichloromethane, and 4) high pressure Soxhlet extraction using liquid CO2 Developments in smaller- and larger-diameter fused silica open tubular columns, and columns coated with a bonded polyethylene glycol stationary phase were also explored. 

Because of the product s volatility, a hot water bath should not be used during solvent evaporation. GC and GC/MS analysis of an aliquot indicate that the product ranges in purity from 75-95% with unreacted 1-iodoheptane also present. The addition of 0.5 equiv of hexamethylphosphoramide (HMPA) prior to addition of the iodoheptane was found to improve the yield of this alkylation. The addition of 0.5 to 2.0 equiv of 1,3-dimethyl-3,4,5,6-tetrahydro-2(1 H)-pyrimidinone (DMPU) did not improve the yield. The checkers found the following GC conditions useful for monitoring the alkylation reaction initial column temperature, 40°C heating increment, fO°C/min iodoheptane R = 3.3 min, product R = 5.7 min. Column specifications were as follows SPB-f (stationary phase), fused silica gel capillary column, 30 m x 0.32 mm ID, 0.25-p.m film thickness. 

The columns used for the GC separation of phytosterols are currently almost exclusively capillary columns with 0.1-0.3 mm internal diameter, and fused-silica capillary columns with chemically bonded stationary phases are commonly used (Abidi, 2001). The best separation of structurally very similar sterols, such as sitosterol and its saturated counterpart sitostanol, is obtained with slightly polar stationary phases like 5% diphenyl-95% dimethylpolysiloxane, and they are currently the most used columns for the separation of phytosterols (Lagarda et al., 2006). For detailed lists of different columns used in sterol analysis, see the papers by Abidi (2001) and Lagarda (2006). 

The column used was a SPB-608 fused silica capillary column, 30 m x 0.53 mm ID. with a 0.5 pm film of stationary phase. It was programmed from 50°C at l°/min to 150°C and then at 8°/min to 260°C. Helium was used as the carrier gas at a flow rate of 5 ml/min and the sample consisted of 0.6 pi of a solution of the pollutants in ndecane. The mass of each pollutant present was about 120 pg. The electron capture detector is also used extensively for monitoring the separation of polychlorinated hydrocarbons and in particular the herbicides. 

The reactor was fed with 1.6 Nl/min of 1000, 2000 and 4000 ppm of methane in air. The mixtures were obtained by mixing N-50 synthetic air and 2.5 % (vol.) CH4 in N-50 synthetic air (Air Products). 40 ppm of SO2 (from a cylinder of 370 ppmV SO2 in N-50 synthetic air. Air Products) were added when the effect of sulphur on the catalysts activity was studied. Flow rates were controlled by calibrated mass flow controllers (Brooks 5850 TR). Exhaust gas was analysed by gas chromatography (Hewlett Packard HP 5890 Series II). Methane in the inlet and outlet streams was analysed using a 30 m fused silica capillary column with apolar stationary phase SE-30, and a FID detector. CO and CO2 were analysed using a HayeSep N 80/100 and a molecular sieve 45/60 columns connected in series, and a TCD detector. Neither CO, nor partial oxidation were detected in any experiment, the carbon mass balance fitting in all the cases within 2%. Methane conversions were calculated both from outlet methane and CO2 concentrations, being both values very close in all the cases. Methane (2000 ppmV) and SO2 (40 ppmV) concentrations have been selected because they are representative of industrial emissions, such as coke oven emissions. 

The separation of essential oil components is usually carried out by GC with fused-silica capillary columns. The properties and conditions of columns used are variable, depending on the polarity of the components to be separated. The most used columns include stationary phases such as DB-1, Carbowax, OV-1, OV-101, PEG 20M, BPS, and DB-5, which cover a wide range of polarities. Column lengths normally range from 25 to 100 m, and stationary phase film thickness ranges from 0.2 to 0.7 pm. Elution of components is usually performed with a temperature gradient ranging from 50°C to 280°C. 

Fig. 1 Analysis of underivatized cyclopeptidic alkaloids in chloroform extract using HT-HRGC. Condition fused-silica capillary column (6 m X 0.25 mm X 0.08 tm) coated with a LM-5 (5% phenyl, 95% polymethylsiloxane immobilized bonded phase) stationary phase. Temperature condition column at 200°C (1 min), increased by 4°C/min, then 300°C (5 min) inlet 250°C FID detector 310°C.

Fig. 2 Chromatogram of underivatized Palmist Oil Elaesis guineensis L.) triacylglyceridic fraction using HT-HRCC. Condition fused-silica capillary column (25 m X 0.25 mm X 0.1 /rm) with the stationary phase OV-17-OH (50% phenyl, 50% methylpolysiloxane immobilized phase). Temperature condition column at 350°C isothermic injector 360°C FID detector 380°C. T is the number of the underivatized triacil-glyceride (e.g., T50 means a triacylglyceride having 50 carbon atoms).

GC on a fused silica capillary column with an MS detector should be used whenever possible for the analysis of organic compounds at trace level in complex mixtures. In fact, it allows the extremely high resolution of GC to be combined with the very high sensitivity and identification power of MS, which makes it possible to determine an analyte at low pg mC levels in the final organic extract. However, GC-ECD is very common for PCB determination since it is both the most sensitive and the less expensive technique for chlorinated compounds (5). PCBs can be separated on a 30-50 m fused silica capillary column with 5% phenyl -95% methylpolysiloxane chemically bonded stationary phase (1). On-column injection is very often used, while several oven temperature programmes have been applied for PCB determinations. The initial temperature is generally 10-15°C lower than the boiling point of the solvent and the final one does not exceed 290-300°C. 

A variety of stationary phases and chromatographic supports have been employed in analyses for phosgene, depending upon the components and their respective concentrations in the particular system. Some of these are summarized in Table 3.3. A range of columns for the detection of phosgene in air has been evaluated [598] recently, a fused-silica capillary column has detected phosgene at 7 p.p.t. (v/v) in 1 litre of ambient air [98a]. 

Sample extracts were analysed by capillary gas chromatography with electron capture detection using either Perkin-Elmer series 8310 or 8510 instruments. One microlitre aliquots were injected via a split/splitless injection system operated in the splitless mode. The components were separated on a 25 m WCOT fused silica capillary column (CP-Sil-5, internal diameter 0.22 pm, Chrompack, UK). The stationary phase was non-polar 100% dimethylpolysiloxane. The temperature program for the separation of chlorobenzenes was based upon the work of Lee et al (1986). Quantification was based on the method of internal or external standard. 

One of the biggest problems in the early development of GC-MS was interfacing the column outlet to the mass spectrometer. Packed columns were used, and the high volumes of both sample and carrier gas overwhelmed the MS system, which operates under low pressure, and special interfaces had to be built. The advent of fused silica capillary columns meant that the GC-MS interface could be dispensed with, and the column eluent is introduced directly into the ion source. It is essential that column bleeding be minimized since the mass spectrometer will detect the stationary-phase materials. Bleeding is prevented by chemically bonding alkylsiloxanes to the column wall. Other low bleeding stationary phases are mentioned above. 

Cross-linked fused-silica capillary columns containing nonpolar or slightly polar stationary phases, such as 5% phenyl methylpolysiloxane or 100% methylpolysiloxane, are the most widely utilized in separating 58,64-66,68,73,90,153,170,172,189,212 percent phenyl methylpoly-... 

A 30 to 50 m fused silica capillary column with a 5% phenyl-95% methyl-polysiloxane chemically bonded stationary phase (DB-5, CP Sil-8, HP Ultra 2, PTE-5) is very often used, while several oven temperature programs have been applied for PCB analysis. Table 18.7 shows a selection of combinations of column lengths, stationary phases, oven temperature programs, and detectors. Table 18.8 shows the stationary phase composition of the capillary columns listed in Table 18.7. Cochran et al. " have reviewed the most recent developments for the capillary GC of PCBs with detailed lists of PCB retention times on common capillary columns. 

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