Modifications of the automated procedure for blood phenylalanine.

MODIFICATIONS of tile automated fluorirnetric pilellylalaIllne proedure (1), which may prove advantageous to those analyzing tile blood of newborn babies for phenylalanine concentration, have been studied and are as follows: 1. A 10-20 times less expensive dipeptide, glycyl-L-leucine ((enera1 Biochemicals, Chagrin Falls, Ohio, Mann Research Laboratories, Inc., New York, N. Y., and Sigma Chemical Co., St. Louis, Mo.) may be substituted for the L-leucyl-L-alanine. 2. An increase in sensitivity of approximately two and a half times may be obtained by substituting a No. 7-51 Corning glass filter for the No. 7-60 filter. In the process of evaluating the above modifications, data were obtained that increased the length of time over that previously reported (1) for the stability of phenylalanine in dried blood spots and which validated a 60/hr. sampling rate for the purposes of screening. The manual method for serum phenylalanine reported by McCaman