AOAC OMA# 2017.03 (Final Action)-OMB

2017.03 (JULY 2018) Amino-02 Tryptophan by enz hyd_Abbott Labs_Method

FOR ERP USE ONLY DO NOT DISTRIBUTE HPLC Determination of Total Tryptophan in Infant Formula and Adult/Pediatric Nutritional Formula Following Enzymatic Hydrolysis Abbott Nutrition, Division of Abbott Laboratories e) Prepare no fewer than two "blank" enzyme solutions per run. Blank solutions will contain enzyme, internal standard, and buffer only. Otherwise follow sample preparation. f) Add 0.5 mL of 5-methyl-DL-tryptophan internal standard to all tubes including the enzyme blanks. g) Add 3.0 mL of 0.1M, pH 8.5 Trizma buffer and 200 µ L methanol to all tubes including enzyme blanks. Cap tubes and vortex lightly (about 2 seconds) to mix contents. Be sure powder samples are completely dissolved but do not over agitate solution to avoid foaming. h) Incubate samples for 16 to 24 hours in heating unit previously set to 50°C. Remove samples from incubation unit after a minimum of 16 hours. Samples may be prepared for overnight incubation if removed within 24 hours. i) Let samples cool to room temperature. Remove caps and add 12 mL of methanol to each tube using a bottle re-pipettor. j) Dilute each tube to the 50 mL mark with Laboratory Water. k) Cap tubes and mix thoroughly by inversion. l) Attach a 0.45 µ m filter to a 3 or 5 cc syringe and transfer several mL of a sample to the syringe. Filter sample into an autosampler vial, and cap. Repeat with fresh syringe and filter for each sample and blank. m) Samples are ready for analysis or may be frozen for future analysis within 72 hours.

G.F.

CALCULATIONS

1. Tryptophan Concentration in Samples:

TRP (g/100g sample) = (CTS – CTB) x (volume / SW) x (100g/1000mg/g) Where:

CTS = Concentration of Tryptophan in Sample (mg/L) CTB = Concentration of Tryptophan in Blank (mg/L) Volume = Final volume in Liters i.e. 50 mL = 0.05L SW = Sample Weight in grams

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