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10Application of High-Performance LiquidChromatography in Environmental AnalysisHigh-performance liquid chromatography (HPLC) is a common analyticaltechnique that is used to determine a wide range of organic compounds. Itsapplication is widespread in industries such as dyes, paints, and pharmaceuticals.More than two-thirds of all organic compounds can be analyzedusing HPLC methods. Its application in environmental analyses, however,has been relatively recent. Only a limited number of U.S. EPA methods arebased on HPLC techniques.Th e basic components of an HPLC system are (1) a pump with a constantfl ow control, (2) a high-pressure injection valve, (3) a chromatographiccolumn, (4) a detector, and (5) a strip-chart recorder or a data system formeasuring peak areas and retention times. Calibration standards are preparedat various concentrations and the retention times and peak areas ofthe analytes are compared against the standard solutions of analytes fortheir identifi cations and quantitations.Th e analytes are separated by adsorption to a polar or nonpolar supportsurface or by partition into a stationary liquid phase. Silica is the mostcommon polar adsorbent. HPLC involves the separation of compoundsby partition on a stationary liquid phase, bonded to a support. Th e support,such as silica, is derivatized with a functional group that is covalentlyattached to the surface and is more stable than any coated phase. Suchbonded phases can be used with most solvents and buff ers. A mobile liquidphase transports the sample into the column where individual compoundsare selectively retained on the stationary liquid phase and thusseparated.In normal phase liquid chromatography, a bonded polar surface, suchas cyano-, diol-, or amino group bound to silica is employed, while themobile phase is nonpolar. Such a technique is commonly used to separatesteroids, afl atoxins, saccharides, and thalidomide. On the otherhand, reversed phase liquid chromatography, a highly versatile technique
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