Extractables

When are Extractables a Concern?

Extractable materials can jeopardize analytical results. For chromatographic analysis, scenarios resulting from extractable materials include sample absorption, coelution, and extraneous peaks. Anomalous results are an analyst's nightmare as procedures typically require action to remedy or identify miscellaneous and unexpected peaks. If unknown peaks in a pharmaceutical chromatogram (extractables) equal 0.1% of the total area then they must be investigated.

Extractable materials become even more of a concern as the amount of analyte diminishes. With recent HPLC column trends utilizing smaller inner-diameter columns (<1 mm for
micro LC) and smaller packing sizes, the ability to separate and detect trace quantities of material is increasing. With these improvements comes increasing concern for the effects of extractable materials.

How to Avoid Extractables' Detritus Effects?

There are three primary methods to avoid the detritus effects of extractable materials. Application testing preserves analysis validity. To application test, analyze the sample fluid before it is filtered. Compare these results to the results obtained after the sample is filtered. If any quantitative or qualitative differences occur, select another filter type. Another method of application testing involves evaluating the results obtained from passing the matrix solvent through the syringe tip filter and evaluating the results. This will demonstrate if material will extract with the neat solvent. When excess sample fluid is available, discard the first few milliliters of fluid eluting from the syringe tip device. Generally, the amount of extractable materials eluted from the filter diminishes with the volume passed through the filter. As will be shown in this study, a 3 mL flush is usually adequate to reduce extractables to an acceptable level.