Routine analysis of porphyrins in urine.

A LTHOUGH a number of procedures are available for quantitative determinations of porphyrins in urine, most of them involve extractions with organic solvents and are not applicable to screening of urinary porphyrins in a large number of patients. The direct spectrophotometric procedure of Rimington and Sveinsson (1) is rapid and works very well for most normal urine specimens. However, urine specimens encountered in clinical laboratories are often highly colored. One of the reasons for this is the increasing use of a wide variety of drugs, many of which absorb light in the visible and near-ultraviolet region of the spectrum. As much as 10 per cent of urine specimens brought to a clinical laboratory for porphyrin determinations may be too highly colored, as evidenced by optical density readings on the Beckman PU spectrophotometer, for application of the spectrophotometric procedure directly to the urine specimen. Sveinsson et al. (2) have described a procedure for preliminary purification of urinary porphyrins by adsorption on calcium phosphate. With and Peterson (3) have utilized this procedure in the