Studying Analyte Binding To Syringe Filters During Filter Validation

By Vivek Joshi, Ph.D., Senior R&D Manager, Applications Development and Wayne K. Way, Ph.D., Pharma Analysis & QC Strategy, MilliporeSigma

Many pharmaceutical QC tests such as dissolution testing, content uniformity, assay, and blend uniformity require sample filtration prior to HPLC or UHPLC analysis. Since quantifying analytes is critical for these tests, method validation should include filter validation studies to evaluate analyte loss to the membrane. Different membrane filters can bind analyte to varying degrees depending on membrane type, the nature of the analyte and analyte concentration.

The easiest method for determining analyte binding to a syringe filter is to filter the sample through it and subsequently collect and analyze various filtrate fractions. Comparing these samples with a centrifuged sample that represents 100% recovery will provide information on analyte binding as well as the volume required for filter saturation.

Filter validation is a critical part of various pharmaceutical QC tests, and various filter parameters need to be taken into consideration during method validation. Since these QC tests require accurate analyte quantitation, analyte binding is an important factor.

This article sums up the results of experiments comparing acidic, neutral, and basic analytes’ binding propensity to hydrophilic PTFE, hydrophilic PVDF, and nylon membranes. It also examines how analyte concentration and filter pore size impact analyte binding.