ABSTRACT
Rubins is used to denote diazo-positive tetrapyrroles that contain the 4,15-biladiene skeleton. Commonly occurring rubins have eight side chains, attached at carbon positions 2, 3, 7, 8, 12, 13, 17, and 18 of the tetrapyrrole skeleton. This chapter outlines the heterogeneity of rubins and major analytical principles to set a background for discussion of the present status of analytical methodology. Specific determination of rubins can be improved by introducing a purification stage, e.g., extraction. Chromatographic procedures are required for determination of compositional parameters, e.g., the proportion of the various carbohydrate residues. Most procedures for separation and measurement of rubins rely on diazo cleavage producing dipyrrolic red-violet azo derivatives which are more stable than the parent tetrapyrroles. Reference procedures should permit assay of rubins in solutions used for calibration and evaluation of routine methods for a variety of biological samples. The chapter considers precautions that may improve storage, separation, and measurement of rubins.
