Preparative liquid chromatographs, requirement

See Selectivity, above, and Table 21.9. Industrial problems usually generate samples with complex matrices and many potential interferences. Selective analytical methods or sample preparation are normally required. Separation techniques are quite commonly used. In the average industrial analytical lab, the most numerous instruments are usually gas or liquid chromatographs because they combine separation with detection. 

The use of small columns such as microbore liquid chromatographic columns, requiring smaller sample size, and computer-controlled solvent delivery and collection systems should lead to the development of fully integrated and automated cleanup systems. Small sample sizes facilitate miniaturization of sample preparation procedures, which in turn brings several benefits including reduced solvent and reagent consumption, reduced processing time, less demand for bench space, and ease of automation. 

NP-HPLC Normal-phase liquid chromatographic methods applying Diol-columns or common silica columns are well suited for the analysis of the total steryl ferulate content. They require very little sample preparation, as total lipid extracts can frequently be directly injected into the column without purification or fractionation. Run times for SFs are also relatively short, and a good separation from other lipid components can be obtained in less than 10 min in traditional HPLC systems. Depending on the column type and the sample, SFs elute as one or two peaks. Two peaks are obtained from the separation of SFs, which have ferulic acid both in cis- and trans- configuration (Nystrom et ah, 2008). The relative retention time (obtained with a silica column and hexane/ethyl acetate 97 3 as eluent) of the cis- form is about 0.5 smaller than that of steryl irans -ferulates (Akihisa et al., 2000). 

The routine analysis of picomole quantities of nucleic acid fragments requires an increased compatibility between prechromatographic sample preparation procedures and sensitive liquid chromatographic detection... 

The BP and EP require liquid chromatographic method to determine impurities of glimepiride [3,7], However, BP and EP differentiate between liquid chromatographic method used to determine impurity A and liquid chromatographic used to examine other impurities. Por the determination of impurity A, test solution and reference solution should be prepared freshly and stored at a temperature not exceeding 12 °C for not more than 15 h. For the test solution, 10.0 mg of the assayed substance is dissolved first in 5 mL of methylene chloride and diluted to 20.0 mL with mobile phase. For the reference solution, 1 mg of glimepiride CRS which contains impurity A is dissolved in 1 mL methylene chloride and diluted to 4.0 mL with the mobile phase. The mobile phase comprises of anhydrous... 

With many sensitive liquid chromatographs, little or no pretreatment is necessary, but with GLC partial purification and isolation are required. Since most biological substances have low volatility or poor thermal stability, it is usually necessary to prepare suitable volatile and stable derivatives before analysis. At present, pretreatment methods involve little or no specialized instrumentation, but this will undoubtedly be developed for use with faster automated chromatographs. Methods of sample injection for GLC are relatively crude and an internal standard is necessary to compensate for errors in the volume injected. If large numbers of samples are to be analyzed repeatedly, some form of automatic injection, linked to a timing device, will need to be developed (J6, Zl). 

Most of the reported spectrophotometric methods for BZ are based on a derivatization technique, and these have poor selectivity, sensitivity and require additional software. Although electrophoresis and liquid chromatographic methods have high sensitivities, they are expensive, involving the use of complex procedures with several sample manipulations and involve long analysis time. Hence, the development of a new effective and efficient method for the determination of BZ in pharmaceutical preparation and biological fluids is an important task. 

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