Deactivation fused-silica capillary columns

Capillary gas chromatography was carried out on an Hewlett-Packard methyl silicone fluid coated, Carbowax 20M deactivated fused silica capillary column, 50m x 0.2mm ID programmed from 100°C to 280°C at 4°/min. A Varian 3700 GC was used with flame ionization detection. 

The surrogate compounds were mono-, tetra-, octa-, deca- C-PCBs, dg-naphthalene, C-PCP and C-phenol. The soil samples were dried with Na2S04 (60 g) and then Soxhlet extracted with hexane acetone (9 1) for 16 h. The extract was dried with sodium sulfate, concentrated, and split. While one portion was held for other analyses, the other portion was placed on a 3% deactivated silica gel column and eluted with increasing solvent polarity systems [hexane, followed by methylene chloride hexane (1 1), and then methylene chloride acetone (95 5)]. The extracts were combined and reduced to 1 mL, split and two internal standards added (tetrafluorobiphenyl and di2 Chrysene). The extracts were chromatographed on a 15-m DB-5 fused silica capillary column and detected with flame ionization (FID). Sludge samples were extracted according to the EPA sludge protocol (2) developed at Midwest Research Institute. 

BPX-5, 30 m, capillary, with deactivated fused-silica quard column... 

Pretorius, V., and Desty, D. H. (1981). Deactivation of fused silica capillary columns with pyrocarbon. J. High Resolut. Chromatogr. Chromatogr. Commun. 4, 122-123. 

Apparatus Gas chromatograph with flame ionization detector (Hewlett-Packard 5890 Series II, or the equivalent) equipped with a 5-pL syringe for 0.32-mm (id) columns. Automatic sampler (HP 7673, or equivalent). Chromatographic data system or integrator (HP 3365 Series II software, or the equivalent). Retention gap, deactivated fused silica, 1-mm x 0.32-mm (id) with capillary column connectors. DB 5-HT, 15-m x 0.32-mm (id) fused silica capillary column (J W Scientific, Inc., 91 Blue Ravine Road, Folsom, CA 95630-4714, catalog number 123-5711, or the equivalent). Crimp caps and vials (HP 5181-3375, or the equivalent) for an on-line autosampler. 

Triazine herbicides represent another class of herbicides that are found widely in groundwater and surface water. This method uses the automated analysis of 10-mL water samples by SPE followed by analysis directly by GC/MS (Brinkman, 1995). The method uses innovative technology to interface the SDU of the PROSPEKT with a precolumn in the GC. The GC is modified such that the sample may be injected onto a precolumn, which is essentially a retention gap column of uncoated deactivated fused-silica capillary that is several meters in length, with the analytical column off-line (see Fig. 10.20). Then the GC may be turned on and analyze the sample automatically. Because the retention-gap column is uncoated, there is refocusing of the analyte on the retaining precolumn, even with large injection volumes of up to 100 pL. 

Figure 2.15. Activity test for an uncoated fused silica capillary column after (A) deactivation with poly(phenylmethylhydrosiloxane) and (B) before deactivation. Precolumn 15 m x 0.20 mm I.D. coated with SE-54. Test columns 10 m x 0.20 mm I.D. The column tandem was programmed from 40 to 180°C at 4°C/min after a 1 min isothermal hold with a hydrogen carrier gas velocity of 50 cm/s. The test mixture contained C q = n-decane, CgNH2 = 1-aminooctane, PY = 3,5-dimethylpyrimidine, C 2 = n-dodecane, C10NH2 = 1-aminodecane, DMA = 2,6-dimethyIaniline, DCHA = N,N-dicyclohexylamine, C12NH2 = 1-aminododecane, and C17 = n-heptadecane. (From ref. [355]. Wiley-VCH).

Capillary Columns for SFC-MS. At present, the major limitation to broad application of capillary SFC technology is related to the availability of columns compatible with supercritical fluid mobile phases. The fused silica capillary columns used in this work were deactivated and coated with crosslinked and surface-bonded stationary phases using techniques similar to those reported by Lee and coworkers (40,41). Columns from less than 1 m to more than 20 m in length and with inner diameters of 10 to 200 ym have been examined. Colvimn deactivation was achieved by purging with a dry nitrogen flow at 350 C for several hours followed by silylation with a polymethylhydrosiloxane. Any unreacted groups on the hydro-siloxane were capped by treatment with chlorotrimethylsilane at 250 C. After deactivation, the columns were coated with approximately a 0.15-.25 ym film of SE-54 (5Z phenyl polymethylphenyl-siloxane) or other polysiloxane stationary phases. The coated stationary phases were crosslinked and bonded to the deactivation layer by extensive crosslinking with azo-t-butane (41). The importance of deactivation procedures for elution of more polar compounds, such as the trichothecenes, has been demonstrated elsewhere (42). 

The first advantage of fused-silica capillary columns as compared with glass columns is their inertness, although they still require deactivation. 

In a series of papers, Lee and coworkers described the use of pentafluorobenzyl bromide as derivatization agent for the determination of 22 phenols in water samples [83,84]. Before derivatization, the phenols were extracted from the water sample into dichloromethane. In the first paper, six different columns were tested, and the OV-101 fused silica capillary column with Carbowax-deactivated surface was found to give the most efficient separation [83]. Detection was carried out using both the BCD and MS. A similar approach, using derivatization with pentafluorobenzyl chloride and BCD, was described for the analysis of monochlorinated and brominated phenols in aqueous samples [85]. 

Figure 3.13 Chromatograms of an activity mixture on 15 m x 0.25 mm (a) uncoated fused silica and (b) fused-silica capillary column after deactivation with Carbowax 20M. Column temperature 70°C 25 cm/s He split injection (100 1). Peaks (l) n-dodecane, (2) n-tridecane, (3) 5-nonanone, (4) n-tetradecane, (5) n-pentadecane, (6) 1-octanol, (7) napthalene, (8) 2,6-dimethylaniline, and (9) 2,6-dimethylphenoL (From ref. 104.)...

Column Material. If a capillary column is to be used, fused silica is the material of choice. A number of fused-silica capillary columns are available. The wall-coated open-tubular column (WCOT), where the liquid stationary phase is coated on the deactivated inside wall of the capillary, has become the most widely used type of capillary column. A second type of capillary column is the porous-layer open-tubular column (PLOT), in which the stationary phase consists of solid particles coated on the deactivated inside wall of the capillary. A third type of capillary column is the support-coated open-tubular column (SCOT), in which the liquid stationary phase is coated over the solid particles coated on the deactivated inside wall of the capillary. 

Figure 12.7 Cliromatograms of a polycarbonate sample (a) microcolumn SEC ti ace (b) capillary GC ti ace of inti oduced fractions. SEC conditions fused-silica (30 cm X 250 mm i.d.) packed with PL-GEL (50 A pore size, 5 mm particle diameter) eluent, THE at aElow rate of 2.0ml/min injection size, 200 NL UV detection at 254 nm x represents the polymer additive fraction ti ansfeired to EC system (ca. 6 p-L). GC conditions DB-1 column (15m X 0.25 mm i.d., 0.25 pm film thickness) deactivated fused-silica uncoated inlet (5 m X 0.32 mm i.d.) temperature program, 100 °C for 8 min, rising to 350 °C at a rate of 12°C/min flame ionization detection. Peak identification is as follows 1, 2,4-rert-butylphenol 2, nonylphenol isomers 3, di(4-tert-butylphenyl) carbonate 4, Tinuvin 329 5, solvent impurity 6, Ii gaphos 168 (oxidized). Reprinted with permission from Ref. (14).

Capillary column A narrow bore tube (0.25-1 mm ID) typically 30-100 m long (usually of deactivated fused silica), whose walls are coated with a liquid stationary phase to produce high-efficiency separations (N > 100,000). 

Glycerin is used in Nasonex primarily as a humectant. For its quantification, both capillary gas chromatography method and HPLC methods may be selected. The GC is equipped with a flame-ionization defector, a 0.53 mm x 30 m fused silica analytical column coated with 3.0-p,mG43 stationary phase, and a 0.53 mm x 5 m silica guard column deactivated with phenylmethyl siloxane. The carrier gas was helium with a linear velocity of about 35 cm/s. The injection port and detector temperature was maintained at 240 and 260°C, respectively. The injection mode is splitless. The column temperature is programmed to be maintained at about 40°C for 20 min, then to increase to 250°C at a rate of 10°C/min and to hold at 250°C for 15 min. 

Procedure (See Chromatography, Appendix IIA) Use a gas chromatograph equipped with an electrolytic conductivity detector operated in the halogen mode and fitted either with a capillary injector operated in the splitless mode or with a purged, packed injector with a glass insert. Use a 30-m x 0.53-mm (id), fused-silica column, or equivalent, coated with l-(xm Supelcowax 10 or an equivalent bonded carbowax column fitted with a 50-cm retention gap of 0.53-mm, deactivated, fused silica, or equivalent. Set the column temperature to 170° for 5 min, raise the temperature at a rate of 5°/min to 250°, and hold it at that temperature for 10 min. Maintain the injector temperature at 225°. Use helium as the carrier gas at a flow rate of 8 mL/min. 

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