Film thickness capillary columns

The methyl esters can be also determined by GC-FID. Using a 30 m x 0.32 mm ID x 0.25 pm (film thickness) capillary column, such as DB-1701 or equivalent, the compounds can be adequately separated and detected by FID. The recommended carrier gas (helium) flow rate is 35 cm/s, while that of the makeup gas (nitrogen) is 30 cm/min. All of the listed herbicides may be analyzed within 25 min. The oven temperature is programmed between 50 and 260°C, while the detector and injector temperatures should be 300 and 250°C, respectively. The herbicides may alternatively converted into their trimethylsilyl esters and analyzed by GC-FID under the same conditions. FID, however, gives a lower response as compared with ECD. The detection level ranges from 50 to 100 ng. For quantitation, either the external standard or the internal standard method may be applied. Any chlorinated compound stable under the above analytical conditions, which produces a sharp peak in the same RT range without coeluting with any analyte, may be used as an internal standard for GC-ECD analysis. U.S. EPA Method 8151 refers the use of 4,4,-dibromooctafluorobiphenyl and 1,4-dichlorobenzene as internal standards. The quantitation results are expressed as acid equivalent of esters. If pure chlorophenoxy acid neat compounds are esterified and used for calibration, the results would determine the actual concentrations of herbicides in the sample. Alternatively, if required, the herbicide acids can be stoichiometrically calculated as follows from the concentration of their methyl esters determined in the analysis ... 

GC-MS (70 eV) analysis is possibly performed with a modern sensitive instrument equipped with a PEG-type bound-phase fused-silica (30 m x 0.32 mm i.d. 0.25 pm film thickness) capillary column, working with helium as carrier gas at flow-rate of 1.2mL/min, transfer line temperature 220 °C and MS source temperature 150 °C. Analysis is carried out in single ion recording (SIR) mode. In the optimized chromatographic conditions proposed by Fedrizzi et al. (2007a), the GC injector is set at a temperature of 250 °C and operates in splitless injection mode for 1 min the oven temperature is programmed to start at 35 °C (5 min), then increased by 1 °C/min to 40 °C, and finally increased by 10°C/min to 250 °C. 

Fig. 2. Partial gas chromatogram of total cyclic fatty acid methyl esters derived from a-linolenic acid. A Cp-Wax 52CB (25 m x 0.25 mm i.d., 0.20 pm film thickness) capillary column was used. There was an initial temperature of 160°C for 5 min followed by a program at 0.5°C/min to 180°C. Peaks a-h were cyclopentenyl acids and i-p were cyclohexenyl acids. Source Ref. 22.

FIGURE 6.2 Fast GC analysis of a lime essential oil on a 5 m x 5 mm (0.05 pm film thickness) capillary column, applying fast temperature programming. The peak widths of three components are marked to provide an illustration of the high efficiency of the column, even under extreme operating conditions (for peak identification see on Ref. [50]). (From Mondello, L. et al., 2004. J. Sep. ScL, 27 699-702. With permission.)... 

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. ... 

Figure 11" represents the simultaneous effects of changing film thickness and column length. These examples also demonstrate that there are techniques available to produce capillary columns of high precision and reproducibility ( ). The coliimns are characterized from top to bottom by a film thickness of 2.0, 1.0 and 0.5 urn and a column length of 15, 30 and 60 m, respectively. 

Fig. 1 Total ion chromatograms of an SCCP top panel) and MCCP bottom panel) technical mixture containing 60 and 53% Cl by weight, respectively. Separation obtained using a DB-5MS (dimension 30 m x 0.25 pm 0.25 pm stationary film thickness) capillary gas chromatography (GC) column [11, 16]...

Sterane and terpane biomarkers in the saturated hydrocarbon fractions of oil samples were analyzed by MRM-GCMS using a Micromass ProSpec-Q instrument. Compound separation was achieved using a 30-m J W Scientific DB-5 capillary column (0.32 mm ID., 0.25 /rm film thickness). The column was programmed from 75 to 200°C at 5°C/min using helium carrier gas and 5p-cholane as the internal standard. Further details are in Peters and Moldowan (1993). 

Carbon Dioxide Carbon dioxide is a compound which is quite difficult to quantify. On liquid stationary phases CO2 already shows some retention at temperatures of 30 °C, albeit only when very thick-film coated capillary columns are used. The separation between the air peak and CO2 is possible only with very accurate control of the injection parameters. By using gas-solid chromatography the retention of CO2 can easily be increased. Several materials show a very high retention towards CO2, for instance aluminum oxide. CO2 is adsorbed and will only elute at temperatures of 200 C as a shifted baseline. 

Cocaine can be separated from the other caine diluents on a 12-m x 0.20-nun-i.d., 0.33-p.m film thickness capillary colunm using an isothermal temperature of 220°C in a very short runtime (>5 min). Figure 16.4 shows the separation of a mixture. Capillary column methods with conditions similar to those shown in Figure 16.4 have replaced the packed column methods used in previous years simply because they provide the best resolution in the shortest analysis time. Capillary GC coupled to a selective detector such as an NPD or a mass spectrometer has become the method of choice for analyzing illicit cocaine samples. 

Figure 13 Gas chromatography-mass spectrometry TIC of the aromatic fraction of an Arabian crude oil. While the TIC of the whole oil yields a chromatographically unresolved "hump, this sample, which has had approximately 95% of the saturates removed by a fast silica SPE cleanup procedure, shows good resolution of the aromatic components, due to the fact that there are far more isomers at a given carbon number of saturates than aromatics. Conditions 100 mg oil deposited on 1-g silica SPE cartridge 2 ml pentane, followed by 2 ml ethyl ether. The ether fraction was partially evaporated and injected splitless into a Varian 3400 gas chromatograph (Varian, Palo Alto, CA) using a 100 m X 0.25 mm ID DB5-MS (0.1 pm film thickness) capillary GC column (special order fiom J W Scientific, Folsom, CA). Colutim temperature ramp 35 to 350°C at 2°C/mln. Mass spectrometer Finnigan (San Jose, CA) SSQ710 in 70-eV FI full-scan mode.

Duranglas glass capillary column (30 m X 0.23 mm i.d.) coated with OV-215 (0.23 p,m film thickness)... 

Figure 10.3 Gas cliromatograms of a cold-pressed lemon oil obtained (a) with an SE-52 column in the stand-by position and (b) with the same column showing the five heart-cuts (c) shows the GC-GC chiral chromatogram of the ti ansfeired components. The asterisks in (b) indicate electric spikes coming from the valve switcliing. The conditions were as follows SE-52 pre-column, 30 m, 0.32 mm i.d., 0.40 - 0.45 p.m film tliickness cairier gas He, 90 KPa (stand-by position) and 170 KPa (cut position) oven temperature, 45 °C (6 min)-240 °C at 2 °C/min diethyl-tert-butyl-/3-cyclodextrin column, 25 m X 0.25 mm i.d., 0.25 p.m film thickness cairier gas He, 110 KPa (stand-by position) and 5 KPa (cut position) oven temperature, 45 °C (6 min), rising to 90 °C (10 min) at 2 °C/min, and then to 230 °C at 2 °C/min. Reprinted from Journal of High Resolution Chromatography, 22, L. Mondello et al, Multidimensional capillary GC-GC for the analysis of real complex samples. Part IV. Enantiomeric distribution of monoterpene hydrocarbons and monoterpene alcohols of lemon oils , pp. 350-356, 1999, with permission from Wiley-VCH.

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).

Figure 12.18 LC-SFC analysis of mono- and di-laurates of poly (ethylene glycol) ( = 10) in a surfactant sample (a) normal phase HPLC trace (b) chromatogram obtained without prior fractionation (c) chromatogram of fraction 1 (FI) (d) chromatogram of fraction 2 (F2). LC conditions column (20 cm X 0.25 cm i.d.) packed with Shimpak diol mobile phase, w-hexane/methylene chloride/ethanol (75/25/1) flow rate, 4 p.L/min UV detection at 220 nm. SFC conditions fused-silica capillary column (15 m X 0.1 mm i.d.) with OV-17 (0.25 p.m film thickness) Pressure-programmed at a rate of 10 atm/min from 80 atm to 150 atm, and then at arate of 5 atm/min FID detection. Reprinted with permission from Ref. (23).

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. 

Chlornitrofen and nitrofen conditions for GC/MS column, cross-linked methyl silicone capillary (12 m x 0.22-mm i.d., 0.33- am film thickness) column temperature, 60 °C (1 min), 18 °C min to 265 °C inlet, transfer line and ion source temperature, 260, 200 and 200 °C, respectively He gas column head pressure, 7.5 psi injection method, splitless mode solvent delay, 3 min electron ionization voltage, 70 eV scan rate, 0.62 s per scan cycle scanned mass range, m/z 100-400. The retention times for chlornitrofen and nitrofen were 11.8 and 11.3 min, respectively. The main ions of the mass spectrum of chlornitrofen were at m/z 317, 319 and 236. Nitrofen presented a fragmentation pattern with the main ions at m/z 283, 202 and 285. ... 

Fused-silica capillary column, HP-SMS, 30 m x 0.25-mm i.d., 0.25- am film thickness, (5% phenyl)-methylpolysiloxane... 

Hewlett-Packard Model 6890 Fused-silica capillary column, HP 35MS, length 30 m, 0.32-mm i.d., film thickness 0.25-p.m (HP No. 19091G-633)... 

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