2015.14 Vitamin B (July 2018)

2015.14 (JULY 2018) BVit-02 Total B_AOAC_2015.14_MLT_Final

FOR ERP USE ONLY DO NOT DISTRIBUTE riboflavin acid stock. Volume provides sufficient ISSM for 6 working standards and 32 samples. Scale as needed. Prepare fresh daily. 7. Phosphate Buffer Solution, pH 5.0 (0.10M Potassium Phosphate Dibasic, 1% EDTA, 2% Metaphosphoric Acid) . a) Weigh 20.0 ± 0.2 g of EDTA into a tarred weighing vessel and quantitatively transfer to a 2000 mL beaker containing approximately 1800 mL laboratory water and add a magnetic stir bar. b) Weigh 34.8 ± 0.1 g of potassium phosphate dibasic into a tarred weighing vessel and quantitatively transfer to the 2000 mL beaker already containing approximately 1800 mL laboratory water and EDTA. Mix by stirring on a magnetic stir plate until both the EDTA and potassium phosphate dibasic is completely dissolved. c) Weigh 40.0 ± 0.2 g grams of metaphosphoric acid into a tarred weighing vessel and quantitatively transfer to the 2000 mL beaker containing approximately 1800 mL laboratory water, EDTA, and potassium phosphate dibasic. Mix by stirring on a magnetic stir plate until the metaphosphoric acid is completely dissolved. Adjust the pH of the solution to pH 5.00 ± 0.02 using 40% potassium hydroxide or 85% phosphoric acid. Quantitatively transfer the solution to a 2000 mL volumetric flask and dilute to volume with laboratory water. Expiration: 48 hours. 8. Native Compounds – Stock Standard Solutions a) Vitamin Standard Stock Mixture (VSSM) - Accurately weigh the indicated amounts for the following standards using separate weighing funnels or other appropriate weighing vessel and quantitatively transfer to a 100 mL volumetric flask using phosphate buffer (pH 5): (a) Niacinamide: 70.5 ± 0.5 mg (b) Thiamine hydrochloride: 10.5 ± 0.2 mg Determine the moisture of the USP thiamine hydrochloride reference standard as directed on the container immediately prior to weighing. The percent moisture determined for the reference standard is used to calculate the concentration of thiamine in the VSSM. (c) Riboflavin: 7.0 ± 0.2 mg - Dry an appropriate amount of the USP riboflavin reference standard at 105 (±1) °C for 2 hours (± 10 minutes) prior to weighing. (d) Pyridoxine Hydrochloride: 10.8 ± 0.2 mg - Dry an appropriate amount of the USP pyridoxine hydrochloride reference standard over indicating absorbent in vacuo for 4 hours prior to weighing. QS to volume with phosphate buffer (pH 5) solution. Heat and slowly stir until the standards have completely dissolved (riboflavin dissolves more slowly) and the solution is clear. Do not heat the solution for more than 40 minutes and do not exceed 90°C. Store refrigerated (2˚-8˚C). Expiration: 3 months. b) Nicotinic Acid Stock Solution (550 ug/mL) - Accurately weigh 13.7 ± 0.1 mg USP niacin (nicotinic acid, catalog 1461003) reference standard. Quantitatively transfer the nicotinic acid to a 25 mL volumetric flask. Add lab water to a total volume of about 20 mL and swirl until completely dissolved. Bring to volume with lab water. Mix well. Expiration: 3 months.