Selective analysis of compound of interest in complicated matrix such as body fluids is extremely difficult. This is because unexpected interference admixtures with almost identical retention time may co-elute with overlapping. It is essential to remove admixtures by appropriate pretreatment for selective analysis. For that purpose there exists several sorts of pretreatment methods, i.e. solid phase extraction (SPE) using column or membrane, dialysis, filtration, ultrafil- tration, super fluid critical extraction (SFE) or adsorption using charcoal or other appropriate adsorbent. There have been reported several pretreatment methods for acidic, basic and neutral compounds in biological fluids. Body fluids direct injection column is also available in the market, however this column has restriction of concentration of organic solvent in the eluent, thus resulting in poor or no elution of strongly hydrophobic compounds. Artifact formation must also be considered during pretreatment methods. Artifact formation may cause lower recovery of the compound of interest and may also cause misunderstanding to the researcher, which he/she extracts unexpected highly strong toxic compound extraction. According to the recent advancement of analytical column fabrication technology, several new columns based on innovated technology are now commercially available. Some of them diminish completely residual silanol effect, thus no common ion addition for strong basic or acidic compounds or no ion-pair method was required. Ion-pair method is so popular, but it often causes to shorten column life by retaining and deteriorating with paring reagent. These columns are also described by comparing conventional columns in this paper.
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