Sampling guideline techniques

Sample preparation techniques must be chosen and optimized with careful regard to the method purpose. As stated in the ICH guidelines, the validated method must be appropriate for the intended purposes. Sample preparation procedures used in bioanalytical applications and their important features are described in Table 4.1. An appropriate technique should be chosen with regard to extraction time, selectivity, the number of steps, solvent consumption, and the possibility of using on-line techniques. 

The recommendations all have difficulties. In the first place, there is a specification that a minimum of five concentrations are to be used. However, reflecting the background of the guidelines in a world of univariate analyses, the different concentrations are to be created using dilution techniques. This method of creating samples is generally unsuitable for spectroscopic (especially NIR) analysis. 

In some cases, when petroleum and/or petroleum products are released to the environment, a free phase is formed and sample(s) of the hydrocarbon material can be collected directly for characterization. The ability to analyze free product greatly aids the determination of product type and potential source. The samples may be diluted prior to analysis EPA SW-846 3580 (waste dilution) gives some guidelines for proper dilution techniques. However, caution is advised since as part of the initial sample collection procedure, water and sediment may be included in the sample inadvertently. Several protocols involved in initial isolation and cleanup of the sample must be recognized. In fact, considerable importance attaches to the presence of water or sediment in crude oil (ASTM D1796, D4007), for they lead to difficulties in other analyses. 

This unit describes procedures for extraction, purification, and identification by MALDI-MS of fiavonol glycosides from a plant source. The extraction and purification protocols are not meant to be comprehensive, but rather to offer guidelines for sample preparation prior to a MALDI-MS analysis. The MALDI-MS technique is suggested as a complement to other analytical methods such as HPLC or NMR. Its strength lies in the ability to rapidly screen a number of samples for the presence of fiavonol glycosides, which can be identified on the basis of their molecular weights. 

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