Octadecyl silane - 18 percent of C load 500 mg/unit Solid phase extraction is a chromatographic technique used to prepare samples for subsequent analysis by removing interfering substances that may be present. This is done either by retaining the substance of interest and washing off everything else or by retaining the interfering substances and eluting the product of interest. These Whatman SPE (Solid Phase Extraction) devices are designed to concentrate or isolate analytes from complex sample matrices. Available with a variety of packing media, these devices offer the advantage of working with different types of interactions between the sample components, sorbent and suitable eluent. The polarity (polar, nonpolar) or charge (anion, cation) of the analyte of interest will determine the proper choice of sorbent and solvent. These have a silica-based chemistry and are available in several configurations. Column capacities include 3, 6 and 12 mL size columns and a cartridge format for use with a syringe is also available. Whatman SPE devices contain high quality sorbets for LC chromatographers.