Capillary column conditioning

The HPLC-GFAA instrumentation and analyses condition have been described previously (see references 25-28). The AA detection of arsenic was at 193.7 nm. The HPLC column was a Dionex anion exchange column with 0.2M (NH ) CO in aqueous methanol as the eluting solvent. The GC-MS analyses were accomplished using a Finnigan 4023 mass spectrometer system with a 30 m x 0.3 mm DB-5 (J W) capillary column, conditions 55° 3 min.) - 300°/min. 

In a technique referred to as GC X GC or two-dimensional GC, direct coupling of two columns with different selectivities allows for a continuous separation of closely eluting or coeluting peaks therefore, it readily separates PAH isomers and many other species that coelute under ordinary capillary column conditions. A GC X GC-MS system has been described where the first separation was on a 20 m X 0.25 mm i.d. 5% phenyl dimethylpolysiloxane column with 0.25 /rm film thickness. Eluate from the first column passed through a cryogenic modulator onto a... 

Figure 4.11 Effect of mode pore diameter on flow velocity of mobile phase through monolithic capillary columns. Conditions capillary column, 100pm ID x 30cm active length stationary phase with 0.3 wt% 2-acrylamido-2-methyl-1-propanesulfonic acid mobile phase, 80 20 v/v mixture of acetonitrile and 5 mmol phosphate buffer, pH = 7. (Reprinted from [416] with permission of Wiiey Sons inc).

Generally, alkan olamines are analyzed by gas chromatography or wet test methods. Details on gas chromatography conditions are available in the fiterature (1) for packed or glass capillary columns. 

Electrophoretic condition 60 cm (effective length of 50 cm)x75 p.m I.D. fused capillary column, run buffer borate buffer pH 9,0, P-cyclodextrin, electrophoresis voltage 20 kV, detection at 254 nm. 

For carrying out of given researches method of synthetic pyrethroids determination in air has been developed. Chromatographic behaviour is investigated and optimum conditions of the synthetic pyrethroids analysis with application of capillary column with stationary phase DB-5 and electron-capture detector are selected. 

Figure 12.13 Illustration of isothermal dual capillary column clnomatography used for separation of UV photolysis products of methyl isopropyl ether, (a) Heait-cut and hack-flushing at preseparation clnomatogram 1, PPG pre-column (20 m X 0.25 mm i.d.) 55 °C, 0.2 har N2 3p.L. Clnomatogram 2, Marlophen main column (100 m X 0.25 mm i.d.) 1.5 har N2 sample, heait-cut from chromatogram 1. (h) Obtained under the same conditions as (a), hut without capping of the heait-cut. Reprinted with permission from Ref. (19).

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).

For capillary columns, the usual practice is to insert the exit end of the column into the ion source. This is possible because under normal operating conditions the mass spectrometer pumping system can handle the entire effluent from the column. It is then only necessary to heat the capillary column between the GC and the MS ion source, taking care to eliminate cold spots where analyte could condense. The interface must be heated above the boiling point of the highest-boiling component of the sample. 

Ethylene hydrogenation was carried out in a once-through flow reactor. The effluent gas mixture was analyzed with an online gas chromatograph (Hewlett-Packard HP 6890) equipped with an AI2O3 capillary column and a flame ionization detector. Testing conditions included Phydrogen = 200 Torr, Pethyiene = 40 Torr, catalyst mass of 10 to 20 mg and temperature varied from -50 to -25°C. 

Typical operating conditions by GC and HPLC are listed in Tables 2 and 3, respectively. Anilides are separated using a weakly polar liquid-phase capillary column, such as SPB-1 or HP-5, which is prepared based on 5% diphenyl-95% dimethylpolysilox-ane for GC. For HPLC, ODS columns are used. 

The determination of acifluorfen in soybean was performed using CE," under the following conditions capillary column (total length 83 cm, 65 cm to the detector, with a 3-mm pathlength, 75-p.m i.d.) absorbance detector, 240 nm capillary oven temperature, 20 °C mnning buffer, 50 mM ammonium acetate buffer (pH, 4.75) applied voltage, 17 kV injection, 0.4 min at 4 mbar migration time, 20 min. 

Under these chromatographic conditions, the CS2 retention time is about 3 min on a fused-silica capillary column and about 2 min on a Teflon Chromosil 330 packed column. 

Figure 1.17 Separation of large ring polycyclic aroaatic hydrocarbons extracted from carbon black on a 1.8 x 0.2 n I.D. fused silica capillary column packed with 3 micrometer spherical octadecylsllanized silica gel eluted with a stepwise solvent gradient at a flow rate of 1.1 mlcroliters/min with an inlet pressure of about 360 atmospheres. Under isocratic conditions this column yielded ca. 225,000 theoretical plates. (Reproduced with permission from ref. 238. Copyright Friedr. Vieweg t Sohn).

Extracolumn dispersion is a major problem for the packed fused silica capillary columns with internal diameters less than 0.35 mm. Peak standeunl deviations will be in the submicroliter range and extensive equipment modification is required for operation under optimum conditions. A reasonable compromise is to esploy injection voluMs of a few hundred nanoliters or less with detector volumes of a similar or preferably smaller size. This demands considerable ingenuity on behalf of the analyst since, as... 

Gebauer, P. and Thormann, W., Isotachophoresis of proteins in uncoated open-tubular fused-silica capillaries with a simple approach for column conditioning, J. Chromatogr., 558, 423, 1991. 

NMR spectroscopy is essential for the structure determination of carotenoid isomers because the TI-NMR signals of the olefinic range are characteristic for the arrangement of the isomers. The stereoisomers of astaxanthin, as shown in Figure 4.16, can be separated on a shape-selective C30 capillary column with methanol under isocratic conditions. 

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