Particulate and Column-contaminating Matter

Inline filters are very effective to protect columns from particulate material. These filters have low dead volume so that they can be placed anywhere after the injector and before the column. The filters are usually replaceable and cost effective to replace. The filter bodies and filter inserts can be metal or polymer. Metal filters are usually made of 316 stainless steel and can be used even if the rest of the chromatographic is plastic. It is a good idea to have an inline filter regardless of whether samples are pre-filtered or not. 

Solid or semi-solid samples may require extraction with an aqueous solution to isolate the ionic components in a form suitable for IC. The actual procedures vary widely, depending on the type of sample. For example, meat and sausage products to be analyzed for nitrate and nitrite are first homogenized mechanically, extracted with a 5% borax buffer solution in a hot water bath, and then subjected to a precipitation with strong solutions of potassium hexacyano ferrate and zinc sulfate. The aqueous extracts are diluted further with de-ionized water and filtered through a membrane prior to injection. 

Organic substances in the sample matrix may interfere with ion chromatographic separations. In some cases it is sufficient to add enough methanol or other organic solvent to completely dissolve the organic matter. But in samples that are soluble in water alone, the organic components may be adsorbed by the IC column packing and prevent reproducible results. This often occurs with dyes that are added to many commercial products. 

Dyes and many other types of soluble organic compounds can usually be removed by some form of solid-phase extraction (SPE) without altering the inor- 

---