Fructose Content	% Dry Substance	Refractive Index at 20	Refractive Index at 45
42%	70.5	1.4632	1.4577
	71.0	1.4643	1.4589
	72.0	1.4667	1.4612
	73.0	1.4691	1.4635
55%	76.5	1.4774	1.4716
	77.0	1.4786	1.4728
	78.0	1.4811	1.4752
	79.0	1.4835	1.4776

Modifier solution— Prepare a solution of magnesium nitrate in water containing about 200 mg per mL. Just before use, transfer 1.0 mL of this solution to a 10-mL volumetric flask, dilute with 5% nitric acid to volume, and mix.

Standard solutions— Transfer 10.0 mL of Lead Nitrate Stock Solution, prepared as directed under Heavy Metals 231, to a 100-mL volumetric flask, add 40 mL of water and 5 mL of nitric acid, dilute with water to volume, and mix. Transfer 1.0 mL of this solution to a second 100-mL volumetric flask, dilute with 5% nitric acid to volume, and mix. This solution contains 0.1 µg of lead per mL. Transfer portions of this solution to four suitable containers, and dilute quantitatively, and stepwise if necessary, with 5% nitric acid to obtain Standard solutions having lead concentrations of 100 ng per mL, 50 ng per mL, 25 ng per mL, and 10 ng per mL, respectively.

Test solution— [note—Perform this procedure in a fume hood.] Transfer about 1.5 g of Syrup, accurately weighed, to two digestion tubes, labeled “Test solution” and “Temperature monitor solution”, and add 0.75 mL of nitric acid to each tube. Warm both solutions slowly to between 90 and 95 to avoid spattering. Heat until all brown vapors have dissipated and any rust-colored tint is gone from the tube labeled “Test solution” (20 to 30 minutes). Cool, add 0.5 mL of 50% hydrogen peroxide dropwise to both solutions, heat to between 90 and 95 for 5 minutes, and cool. Add a second 0.5-mL portion of 50% hydrogen peroxide dropwise to each solution, and heat to between 90 and 100 for 5 to 10 minutes until the tube labeled “Test solution” is clear. Cool, and transfer the Test solution to a 10-mL volumetric flask. Rinse the tube labeled “Test solution” with 5% nitric acid, add the rinsing to the volumetric flask, dilute with 5% nitric acid to volume, and mix.

Standard blank— Use 5% nitric acid.

Test blank— Transfer 1.5 g of water to a digestion tube, and proceed as directed for the Test solution, beginning with “add 0.75 mL of nitric acid.”

Procedure— [note—Use peak area measurements for all quantitations.] Add 5 µL of the Modifier solution to 20 µL each of the Standard solutions, the Test solution, the Standard blank, and the Test blank, and mix. Separately inject equal volumes (about 20 µL) of the Standard solutions, the Test solution, the Standard blank, and the Test blank into a suitable graphite furnace atomic absorption spectrophotometer equipped with pyrolytically coated graphite tubes and adequate means of background correction. The temperature is programmed as follows. Maintain the drying temperature of the furnace at 200 for 30 seconds after a 20-second ramp time using an argon gas flow of about 300 mL per minute; maintain the ashing temperature at 750 for 40 seconds after a 40-second ramp time using an airflow of about 300 mL per minute; cool down and purge the air from the furnace for 60 seconds using a 20 set temperature and an argon gas flow of about 300 mL per minute; and maintain the atomization temperature at 1800 for 10 seconds after a 0-second ramp time with the argon gas flow stopped. [note—The temperature program may be modified to obtain optimum furnace temperatures.] Using the Standard blank to set the instrument to zero, determine the integrated absorbances of the Standard solutions at the lead emission line at 283.3 nm. Plot the integrated absorbances of the Standard solutions versus their contents of lead, in ng per mL, and draw the line best fitting the four points to determine the calibration curve. Similarly determine the integrated absorbances of the Test solution and the Test blank at the lead emission line at 283.3 nm. Correct the absorbance value of the Test solution by subtracting from it the absorbance value obtained from the Test blank. Calculate the concentration, in µg per g, of lead in the portion of Syrup taken by the formula: in which C is the concentration, in ng per mL, of lead in the Test solution, as determined from the calibration curve; and W is the weight, in g, of Syrup taken to prepare the Test solution: the limit is 0.1 µg per g.

Mobile phase— Use filtered and degassed water.

Standard preparation— Prepare a solution in water containing a total of about 10% saccharide solids of USP Dextrose RS, USP Fructose RS, and USP Maltose Monohydrate RS, in which the USP Dextrose RS and USP Fructose RS percentage concentrations are in the same ratio as those in the Assay preparation, based on the labeled nominal fructose percentage for the Syrup under test. Calculate the percentage of USP Maltose Monohydrate RS by the formula: in which F is the labeled nominal fructose percentage for the Syrup under test; and D is the difference between the specified minimum percentage concentration of total monosaccharides for the Syrup and F.

Assay preparation— Dilute a known volume of Syrup, determined from the results of the test for Total solids and on the nominal total saccharides content, with water to a total saccharides concentration of about 10% (w/v), and mix.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a refractive index detector maintained at 45 and a 7.8-mm × 30-cm column that contains packing L19. The column is maintained at a constant temperature of about 85. The flow rate is about 0.6 mL per minute. Chromatograph the Standard preparation, and record the peak areas as directed for Procedure: the relative retention times are about 0.83, 1.0, and 1.32 for maltose, dextrose, and fructose, respectively; and the resolution, R, between maltose and dextrose is not less than 1.2.

Procedure— Separately inject equal volumes (about 10 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the areas for the major peaks. Calculate the percentage of fructose and of dextrose in the portion of Syrup taken by the formula: in which C is the concentration, in mg per mL, of USP Fructose RS or USP Dextrose RS in the Standard preparation; VA is the volume, in mL, of the Assay preparation; VS is the volume, in mL, of Syrup taken to prepare the Assay preparation; S1 is the percentage of total saccharides in the Standard preparation (corresponding to 97 for High Fructose Corn Syrup 42% and to 95 for High Fructose Corn Syrup 55%); S2 is the percentage of total solids in the Syrup as determined in the test for Total solids; and rU and rS are the peak areas of fructose or dextrose obtained from the Assay preparation and the Standard preparation, respectively. Calculate the percentage of other saccharides, expressed in terms of maltose, in the portion of Syrup taken by the formula: in which C is the concentration, in mg per mL, of USP Maltose Monohydrate RS in the Standard preparation; rU is the sum of all peak areas obtained from the Assay preparation, except those of fructose and dextrose; and rS is the peak area of maltose obtained from the Standard preparation.