Picrinic acid

To analyze free amino acids in plasma or tissue homogenates, it is necessary to remove proteins and peptides present in solution. The most widely used deproteinization method is precipitation with 5-sulfosalicylic acid followed by centrifugation for separating the precipitate. In comparison to other precipitation agents such as trichloroacetic acid, perchloric acid, picrinic acid, or acetonitrile, the best results with respect to completeness of precipitation are obtained with 5-sulfosalicylic acid [39]. Other deproteinization methods comprise ultrafiltration and ultracentrifugation [40], which have only recently been considered as sample preparation methods for amino acid analysis. 

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