Reference chromatographic method

As a third option, impurities appearing in the reference chromatographic method may be isolated using analytical (under overloaded conditions) or semi-prep chromatography and then identified by MS and/or NMR. Mobile-phase components should be removed prior to analysis. Removal of mobile-phase components may entail evaporation, liquid-liquid extraction, freeze-drying, or solid-phase extraction. Identification by MS should be attempted first because its high sensitivity requires only small sample amounts. The less sensitive NMR requires the isolation of greater amounts of the impurity. An alternative to this approach is the use of LC-MS or LC-NMR. 

Results found by the NIR method compared well with those obtained by the reference chromatographic procedures. The developed PLS/NIR method does not consume any solvent as no sample preparation is necessary, improving the laboratory efficiency without sacrifice the accuracy. 

After the extrachon of total lipids from four different genotypes of flax seed (Linum usitassimum) differing markedly in their acyl composihon, PTLC was used for the isolahon of different lipid classes in the neutral lipid frachon [69]. Application of planar chromatographic methods, including PTLC, in the separahon of food lipids has been reviewed with 40 references by Olsson [70]. The polar lipid fraction of niger seed (Guizotia abyssinica Cass.) collected from different regions of Ethiopia could be separated by PTLC on silica gel [71]. 

Nova-Pak C18 column in a methanol water chloroform gradient.92 Choline chloride was added to the mobile phase. One review of techniques used in the analysis of triacylglycerols lists over 300 references on separations of the triglyceride fraction of fats using nonaqueous RPLC, aqueous RPLC, argen-tation chromatography, and other chromatographic methods.93... 

Tsuji and Goetz24 developed a quantitative high performance liquid chromatographic method for separating and measuring erythromycins A, B, and C, their epimers and degradation products. This method uses a /iBondapak Ci 8 reverse column with acetonitrile-methanol-O.2m ammonium acetate-water (45 10 10 25) as solvent. The pH and composition of the mobile phase may be adjusted to optimize resolution and elution volume. The authors utilized the procedure on USP reference standard and report a relative standard deviation of 0.64%. 

Chromatographic methods are also often used as part of systems that are called hyphenated methods, (see Chapter 15) where the output of the chromatographic section is used as the input for an identification method such as mass spectrometry. These hyphenated methods are also most often referred to by their acronyms, for example, GC-MS—gas chromatography-mass spectrometry and HPLC-MS—high-performance liquid chromatography-mass spectrometry. Note that although ultraviolet-visible (UV-Vis) is hyphenated, it is not a hyphenated method in that it does not consist of two different methods of analysis. Hyphenated methods will be discussed fully in Chapter 15. 

Dynamic coupled-column liquid chromatographic method Calculation from evaporation rates and vapor pressures of reference compound... 

Both preconcentration and purification are accomplished with traditional ion exchange chromatographic methods. More than one procedure has been used—the interested reader is referred to relevant publications for analytical details (Barling et al. 2001, Siebert et al. 2001). 

One method (EPA 8020) that is suitable for volatile aromatic compounds is often referred to as benzene-toluene-ethylbenzene-xylene analysis, although the method includes other volatile aromatics. The method is similar to most volatile organic gas chromatographic methods. Sample preparation and introduction is typically by purge-and-trap analysis (EPA 5030). Some oxygenates, such as methyl-f-butyl ether (MTBE), are also detected by a photoionization detector, as well as olefins, branched alkanes, and cycloalkanes. 

In addition to online resources, other texts and references have discussed the process of validation for methods used in the pharmaceutical industry in relation to the regulatory guidance documents. These guides include discussions on method development in relation to method validation, the validation of non-chromatographic methods and stability indicating methods. 

Any comprehensive discussion of chromatographic methods is well beyond the scope of both this chapter and the author s area of expertise, but the importance of high-quality isolates nevertheless warrants comment. There are a number of published reviews dealing with various aspects of preparative chromatography in relation to pharmaceutical impurities to which the interested reader is referred [25-30], as well as to Chapter 7. 

ISEC, which was introduced by Halasz and Martin in 1978 [119], represents a simple and fast method for the determination of the pore volnme, the pore size distribution profile, and the spe-cihc snrface area of porous solids. Generally, ISEC is based on the principle of SEC. SEC, also referred to as gel permeation or gel filtration chromatography, is a noninteractive chromatographic method that separates analytes according to their size by employing a stationary phase that exhibits a well-dehned pore distribution. 

System suitability allows the determination of system performance by analysis of a defined solution prior to running the analytical batch. System suitability should test the entire analytical system, chromatographic performance as well as the sensitivity of the mass spectrometer for the compounds of interest. Some LC-MS SOPs reference analytical methods as the source of operating details for a given analysis. This works particularly well for quantitative analysis, where analytical methods include critical details on instrument parameters and special calibrations that might be required for a particular analyte. Thus, system suitability testing provides the daily [3] checking of the system. 

J. F.M.McOmie, Chromatographic Methods in Inorganic Analysis with Special Reference to Paper Chromatography , Academic Press NY (1953) 47a)G.H.Osborne, Analyst 78, 220-21 (1953) 48)R.C.Brimley F.C. 

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