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* Details given are for chromatographic or electrophoretic location and will differ for use with liquid samples. ** Amino acids customarily detected are in bold type.

* Details given are for chromatographic or electrophoretic location and will differ for use with liquid samples. ** Amino acids customarily detected are in bold type.

Other reagents that are more specific for particular amino acids have been described (Table 10.8) and their use significantly assists in the identification process. The different locating reagents may be applied either to separate chromatograms or as part of a multi-dip sequence, when they should be used in the recommended order to prevent interference of one reagent by another. Many reagents are hazardous and must be handled in accordance with approved safety procedures.

The formation of DNP or dansyl amino acid derivatives followed by chromatography or electrophoresis is a useful technique in certain circumstances. The preparation of DNP derivatives may be indicated when the sample for analysis contains a variety of other substances, removal of which would be complicated, leading possibly to considerable analytical errors. However, the derivative formation and extraction is time consuming and itself can introduce inaccuracies into the analysis and should be used only when it offers an advantage over the separation of untreated amino acids.

The use of dansyl derivatives is not recommended for routine analysis of free amino acids but is very suitable in the identification of an unknown amino acid that has been selectively extracted from the original sample and is present in small quantities. Both kinds of derivative Can be easily separated by chromatography or electrophesis and no locating reagent is required for either because the DNP derivatives are themselves yellow in colour and the dansyl derivatives are fluorescent.

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