AOAC RI ERP E-Book - DS DF

Obtain the values for the peak areas of D-glucose and internal standard (glycerol) from duplicate chromatograms. The ratio of peak area of D-glucose/peak area of glycerol to the ratio of the mass of D-glucose/mass of glycerol is the “response factor.” The average response factor for D-glucose is approximately 0.82 vs. glycerol.

Response factor (Rf) = (PA-IS)/(PA-Glu) x (Wt-Glu)/(Wt-IS)

where PA-Glu = peak area of D-glucose; PA-IS = peak area of internal standard (glycerol); Wt-Glu = mass of D-glucose in standard; and Wt-IS = mass of internal standard (glycerol) in standard. (e) Calibrate the area of the chromatogram to be measured for SDFS. Use a 100- μL LC syringe, B(dd) to fill the 50-μL injection loop with retention time standard, C(h) . Inject in duplicate. Determine the demarcation point between DP2 and DP3 oligosaccharides (disaccharide maltose versus higher oligosaccharides) (Figure 2017.xxD). (f) Determine peak areas of SDFS (PA-SDFS) and internal standard (PA-IS) in chromatograms of sample extracts. Inject sample extracts, H(c) on LC. Record areas of all peaks of DP greater than the DP2/DP3 demarcation point as PA-SDFS. Record the peak area of internal standard as PA-IS.

I. Calculations for HMWDF (by gravimetry) Blank (B, mg) determination . AOAC Research Institute ERP Use O ly B = [(BR 1 + BR 2 )]/2 – P B – P A

Where: BR 1 and BR 2 = residue mass, in milligrams, for duplicate blank determinations, respectively, and P B and P A = mass, in milligrams, of protein and ash, respectively, determined on first and second blank residues.

HMWDF = (mg/100 g) = [(R 1 + R 2 )/2 – P B – P A – B]/(M 1 + M 2 )/2] x 100

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