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This method is for the quantitative determination of the amino acid tyrosine in whole blood saturated filter paper disks using the APF™ 300 SPOTCHECK® Analyzer or the RFA 300 System. Measurements obtained by this device are used primarily to screen newborns for congenital tyrosinemia, a disease that can cause liver/kidney disorders.

The proposed device, Tyrosine 50-Hour Reagent Kit, is a set of reagents to be used with the API™ 300 SPOTCHECK® Analyzer or the RFA 300 System for the quantitative determination of the amino acid tyrosine (Tyr) in whole blood saturated filter paper disks. The amount of Tvr is determined by measuring the fluorescent compound produced in the reaction of tyrosine with 1-nitroso-2-naphthol, catalyzed by nitrous acid at 80°C. The excitation wavelength of the product is 450 nm and emission is measured at 550 nm. The method is specific for para-substituted phenolic compounds. Excess 1-nitroso-2-naphthol is removed from the reaction mixture by reduction with sodium m-bisulfite. The method is designed for mass screening, with enough reagents in each 50-Hour ' Reagent Kit for 1 week plus start-up (50 hours total) of run time. It is packaged to reduce storage space and to require a minimum of time to prepare. Each component is packaged with the correct weight to prepare the required volume of reagent. The standard is in a concentrated form, to permit easy dilution to prepare a standard curve.