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SOLID PHASE MICROEXTRACTION: CHROMATOGRAPHY

المؤلف:  Max M. Houck، Jay A. Siegel

المصدر:  Fundamentals of Forensic Science

الجزء والصفحة:  p128-129

2026-07-04

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SOLID PHASE MICROEXTRACTION: CHROMATOGRAPHY

Solid and liquid phase extractions have proven to be reliable, versatile methods of separation of many types of analytes. However, they are by no means universal and even the microextraction methods developed for solid phase extraction are not suit able for extremely small amounts of material. These techniques work best with solid samples that are soluble in at least one volatile solvent. Neither of these techniques are quantitative; one cannot easily determine the concentration of an analyte by these methods. At the turn of the last century, a Russian botanist revolutionized analytical chemistry by developing a separation method that has evolved into a whole family of analytical techniques applicable to a huge variety of mixtures of solids, liquids, and vapors, over a large temperature range, whether they are soluble in solvents or not. This family is collectively known as chromatography. The term “chromatography” means literally “to write with color.” This seems like an odd name for a

family of techniques that seem to have little to do with color, and everything to do with separating mixtures of substances. The reason for the name is that the technique was originally developed by a Russian botanist, Michael Tswett (whose name in Russian means color!) in 1901, who was interested in separating colored pigments in plants. He purified a fine, sand-like substance and filled a long column with it. He then prepared a solution of the pigments that he wanted to separate and poured this through the column. He found that the pigments were divided into colored bands at various points along the length of the column. Each band represented a component of the pigments. The bands were identifiable by their different colors. This column was able to separate the pigments this way. He could then take each band of the column and elute off the pigment. This technique worked only for substances that had a native color. The “detector” was the naked eye. Transparent pigments could not be detected by this method. Chromatography evolved and developed over the next century. It would have had much more limited uses if it depended on color to detect substances and could only have been operated at ambient temperature. Since these original experiments, however, chromatography has come a long way. The term has come to represent a family of techniques that all do essentially the same thing: separate complex mixtures of substances into their individual components and then display these components so that the analyst can get information about their number and chemical nature and sometimes concentration. There are many advantages of chromatography over solid and liquid phase extractions and a huge variety of materials may be separated by one type of chromatography or another. Chromatography methods are also generally more sensitive than extractions. Some chromatography methods can separate millionths or billionths of a gram of material.