Chromatographic suitability

Procedure (See Chromatography, Appendix IIA.) Use a liquid chromatograph suitable for size-exclusion chromatography and equipped with a refractive index detector and a 60-cm x 7.5-mm (id) column packed with 5-p.m, 500A porosity PL-Gel, or equivalent, both operated at 40°. Operate the chromatograph at 500 to 1500 psi at a flow rate of 1.0 mL/min. 

Due to often limited sample size, it is an absolute must not to waste sample material by preparing it before the HPLC method is considered suitable for use. Problems encountered at this stage may take some time to diagnose and repair (see Chapter 10) and samples can and do degrade with time (see Chapter 6). System suitability parameters can usually be defined in two ways the system performance and the chromatographic suitability. 

Gas Chromatographic System, equipped with temperature programmable gas chromatograph suitable for split injections with WCOT column or cool-on-column injector which allows the injection of small (for example, 0.1 pL) samples at the head of the WCOT column or a retention gap. An autosampler is mandatory for the on-column injections. 

Gas Chromatograph, a temperature programmable gas chromatograph suitable for splitless injections equipped with an electron capture detector (ECD). 

By connecting a gas chromatograph to a suitable mass spectrometer and including a data system, the combined method of GC/MS can be used routinely to separate complex mixtures into theii individual components, identify the components, and estimate their amounts. The technique is widely used. 

Gyclodextrins. As indicated previously, the native cyclodextrins, which are thermally stable, have been used extensively in Hquid chromatographic chiral separations, but their utihty in gc appHcations was hampered because their highly crystallinity and insolubiUty in most organic solvents made them difficult to formulate into a gc stationary phase. However, some functionali2ed cyclodextrins form viscous oils suitable for gc stationary-phase coatings and have been used either neat or diluted in a polysiloxane polymer as chiral stationary phases for gc (119). Some of the derivati2ed cyclodextrins which have been adapted to gc phases are 3-0-acetyl-2,6-di-0-pentyl, 3-0-butyryl-2,6-di-0-pentyl,... 

In addition to modem spectroscopic methods ( H nmr spectroscopy, ftir spectroscopy) and chromatographic methods (gc, hplc), HBr titration (29) is suitable for the quantitative analysis of ethyleneimine samples which contain relatively large amounts of ethyleneimine. In this titration, the ethyleneimine ring is opened with excess HBr in glacial acetic acid, and unconsumed HBr is back-titrated against silver nitrate. 

Air Monitoring. The atmosphere in work areas is monitored for worker safety. Volatile amines and related compounds can be detected at low concentrations in the air by a number of methods. Suitable methods include chemical, chromatographic, and spectroscopic techniques. For example, the NIOSH Manual of Analytical Methods has methods based on gas chromatography which are suitable for common aromatic and aHphatic amines as well as ethanolamines (67). Aromatic amines which diazotize readily can also be detected photometrically using a treated paper which changes color (68). Other methods based on infrared spectroscopy (69) and mass spectroscopy (70) have also been reported. 

Several gas-Hquid chromatographic procedures, using electron-capture detectors after suitable derivatization of the aminophenol isomers, have been cited for the deterrnination of impurities within products and their detection within environmental and wastewater samples (110,111). Modem high pressure Hquid chromatographic separation techniques employing fluorescence (112) and electrochemical (113) detectors in the 0.01 pg range have been described and should meet the needs of most analytical problems (114,115). 

Chromatographic separation of diluted molasses streams into a high purity fraction suitable for concentration and crystallization and a second low purity by-product, which can be concentrated and sold as an animal feed product, has been employed in Finland since the 1970s and in the United States since the mid-1980s. Since the early 1990s, production of sugar from beet molasses has almost tripled, and the trend is expected to continue for the next two years to consume most of the domestic beet molasses (Fig. 7) (3,9). 

Various aspects of the chromatography of vitamin B 2 and related corrinoids have been reviewed (59). A high performance Hquid chromatographic (hplc) method is reported to require a sample containing 20—100 p.g cyanocobalamin and is suitable for premixes, raw material, and pharmaceutical products (60). 

The high degree of sensitivity, selectivity, and efficiency of gas chromatography allows the elucidation of a complete profile of the volatile components of distilled spirits. The wide selection of chromatographic columns and techniques, such as gc-ms, gc-ftir, and gc-ms-ftir, has allowed the chemist to routinely identify and quantify individual constituents on a parts-per-biUion level. The two most critical variables in the analysis of volatile components of distilled spirits by gas chromatography are the selection of a suitable chromatographic column and of the most appropriate detector. 

The measurement of VLE can be carried out in several ways. A common procedure is to use a recycle stiU which is designed to ensure equiHbrium between the phases. Samples are then taken and analy2ed by suitable methods. It is possible in some cases to extract equiHbrium data from chromatographic procedures. Discussions of experimental methods are available (5,11). Eor the more challenging measurements, eg, conditions where one or more components in the mixture can decompose or polymeri2e, commercial laboratories can be used. 

Methods which ai e described in Phamiacopoeias (American, British, and European) ai e based on using narrow standai ds for calibration and broad standai d for system suitability test. Prescribed limits of system suitability ar e broad and therefore it may cause large uncertainty of results. But on the other side results ar e strongly influenced by par ameters of chromatographic system. 

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