Fused-silica capillary columns characteristics

The presence of residual THF in the final product is easily detected by the characteristic NMR signals at 6 1.85 (4 H) and 3.75 (4 H). The checkers found GLC to be more convenient than 1H NMR for analysis at this point. Either a 6 x 2 mm glass column of 3% 0V-101 on MHP 80/100 with 30 nt/min He or a 15 m x 0.25 mm fused silica capillary column of DB-5 (cross-linked phenyl silicone) with 1 mL/min H2 proved sufficient to resolve butane, trimethylsilylacetylene, butyltrimethylsilane, THF, 1-chlorobutane, and b1s trimethylsilyl)acetylene. 

A GC-MS method was used in the study of the analytical characteristics of volatile Al(dik)3 and Cr(dik)3, dik = acac and tfac. Aluminum and chromium chelates were well separated on a fused silica capillary column of 25 m length and 0.20 mm i.d. with electron impact ionization MS detection, and yielded the unique base peak pattern corresponding to the loss of one ligand from the molecular ion. Cr(tfac)3 exhibited a pair of chromatographic peaks which were found to produce nearly identical mass spectra, pointing to the existence of two geometrical isomers. ... 

Table 31-4 compares the performance characteristics of fused-silica capillary columns with other types of wall-coated columns as well as with support-coated and packed columns. 

Capillary electrophoresis is the name for a relatively new group of related techniques which have been attracting increasing interest in which separation of analyte species is achieved on the basis of differential migration in an electric field through narrow bore fused silica capillary columns (25-100 pm, i.d.). The techniques which differ significantly in operative and separation characteristics include... 

Phthalate esters listed as EPA priority pollutants may be analyzed in wastewaters by U.S. EPA (1984) Methods 606 (GC), 625 (GC/MS), and 1625 (isotope dilution). Soils, sediments, groundwater, and hazardons wastes may be analyzed by GC using FID or ECD (Method 8060) or by GC/MS (Method 8270 or 8250) (U.S. EPA 1986). The primary and secondary characteristic ions to identify these compounds by GC/MS (electron-impact ionization) are as follows dimethyl phthalate, 149, 177, and 150 din-butyl phthalate, 149, 150, and 104 butyl benzyl phthalate, 149, 167, and 279 and din-octyl phthalate, 149, 167, and 43. Other phthalate esters may be analyzed by GC or GC/MS techniques. A fused-silica capillary column is suitable for the purpose. 

Polynuclear aromatic hydrocarbons at trace concentrations may be analyzed by HPLC, GC and GC/MS by US EPA Methods 610, 8100, 8270 and 8320 (US EPA 1997). GC techniques involve the use of a flame ionization detector and a fused silica capillary column or a packed column such as 3% OV-17 on Chromosorb W-AW or equivalent. Certain PAH compounds may coelute on a GC column. This problem does not occur in the reversed phase HPLC analysis using UV and fluorescence detectors. A column such as HC-ODS Sil-X or equivalent having a 5-/Lim particle size is suitable for separating PAH mixtures. GC/MS is a confirmative method to identify individual compounds although some of the compounds produce the same characteristic masses. The compounds should be identified from fheir characferisfics mass ions and refenfion times. Various analytical methods and the characteristic mass ions of some... 

GC-FID, GC-PID, GC-HECD, or GC/MS. A fused-silica capillary column is suitable for chromatographic analysis. Characteristic ions for GC/MS identification (electron-impact ionization) are 157, 78, and 79. 

Acetone is analyzed by GC-FID. A Car-bowax 20 M, Carbopack, fused-silica capillary column, or any equivalent column may be suitable. It may be analyzed by GC/MS using a purge and trap technique or by direct injection. Characteristic ions are 43 and 58 (electron-impact ionization) (U.S. EPA 1986, Method 8240). Acetone in air is adsorbed over coconut shell charcoal, desorbed with CS2, and analyzed by GC-FID using a 10% SP-2100 or DB-1 fused-silica capillary column (NIOSH 1984, Method 1300). Airflow rate 10 to 200mL/min volume 0.5-3 L of air. Trace acetone in water can be determined by the fast HPLC method discussed in Chapter 5. 

Comparison of chromatographic characteristics for two fused-silica capillary columns of the same dimensions (20 m x 0.25 mm) [129]. 

This procedure was used by Berezkin and coworkers for flexible fused silica columns [109]. The results of comparison of two squalane-coated fused silica capillary columns, one of which had previously been wall-coated with barium carbonate crystals, are given in Table 6-6 [109]. The capillary column with rough inner walls has better chromatographic characteristics. This result was confirmed by comparison of two chromatograms obtained on these columns (see Fig. 6-23 [106]). Only 7 chromatographic peaks were separated on the column with smooth walls while all 12 peaks were separated on the column with walls covered by barium car-... 

Chromatographic characteristics of two fused silica capillary columns with squalane [109], ... 

Lipids were separated by TLC according to Kates (7) and identified by comparison with standard lipids and by characteristic color reactions. Bands were scraped from TLC plates. For fatty acid analysis, samples from TLC plates or freeze-dried samples of Porohyridium were treated with methanol-acetyl chloride (95 5). Heptadecanoic acid was added and the mixture was handled up as previously described (8,9). Gas chromatographic analysis was performed on a SP-2330 fused silica capillary column at 200°. Fatty acids were identified by comparison with authentic samples and by GC-MS. 

One-step method for the preparation of highly enantioselective monolithic columns for CEC has been developed by Frechet et al. The chiral polymer bed of defined pore distribution and chiral ligand concentration has been synthesized within the confines of untreated fused silica capillaries using a mixture of O-[2-(methacryloyloxy)ethylcarbamoyl]-10,ll-dihydroquinidine 76, ethylene dimethacrylate (EDMA), and glycidyl methacrylate or 2-hydroxyethyl methacrylate (HEMA) in the mixture of cyclohexanol and 1-dodecanol as porogenic solvents. Under optimized synthetic and chromatographic conditions, these materials with the desired characteristics were demonstrated to efficiently separate a model racemic DNZ-Leu, Figure 13.24 [146],... 

Sarin in water may be analyzed by gas chromatography after extraction with chloroform. Using an internal standard linearity was determined to faU in the range 10-1000 ppb with flame photometric detector (Shih and Ellin 1986). Flame photometric or a nitrogen-phosphorus detector should be operated in the phosphorus-specific mode. A fused-silica capillary GC column should be effi-cienf in separation. Sarin may be analyzed by GC/MS. The primary mass ion is 99. Ofher characteristic mass ions are 125, 81,43, and 79. 

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