Abstract:

Ascorbic acid-molybdenum blue spectrophotometric method was used for the determination of phosphate in beer. In order to obtain optimal determination results, 4 crucial determination parameters, including detection wavelength, color development time and amounts of chromogenic reagent and sulfuric acid were investigated. Results showed that the optimal values of the above parameters were as follows: detection wavelength 820 nm, sulfuric acid (9.58 mol/L) amount 2.00 mL, ammonium molybdate solution (60 g/L) 2.00 mL, ascorbic acid amount 1.00 mL, and color development time in 70 ℃ water bath 20 min. Under these conditions, a good linear relationship between absorbance (A) and phosphate concentration (c) was observed, which could be expressed as A = 0.2001c+ 0.0225 (r = 0.9996). Mean recoveries of phosphate in Harbin wheat beer varied from 94.04% to 102.03%, with a mean RSD of 1.14%. The method has the merits of omitted sample pretreatment and easy operation, and therefore is applicable to the quality control in beer production.

Key words: beer, phosphate, ammonium molybdate, spectrophotometry