Add the following:
» Corn Syrup is an aqueous solution of saccharides obtained by partial hydrolysis of edible corn starch by food grade acids and/or enzymes. It contains not less than 20.0 percent reducing sugar content (dextrose equivalent) expressed as d-glucose, calculated on the dried basis.
Packaging and storage Preserve in tightly closed containers. No storage requirements are specified.
Labeling Label it to indicate its nominal dextrose equivalent. Label it also to indicate the presence of sulfur dioxide if the residual concentration is greater than 10 µg per g.
Identification Add a few drops of a solution of Syrup (1 in 20) to 5 mL of hot, alkaline cupric tartrate TS: a copious, red precipitate of cuprous oxide is formed.
Microbial enumeration tests 61 and Tests for specified microorganisms 62 The total aerobic microbial count does not exceed 1000 per g, and the total combined molds and yeast count does not exceed 100 per g.
Residue on ignition 281: not more than 0.5%, determined on 20 g of Syrup.
Heavy metals, Method II 231: not more than 5 µg per g.
Starch Dissolve 1 g in 10 mL of water, and add 1 drop of iodine TS: a yellow color indicates the absence of soluble starch.
Total solids Use a suitable refractometer (see Refractive Index 831) equipped with a jacket for water circulation or some other mechanism for maintaining the test specimen at 20 ± 0.1 or 45 ± 0.1. Before proceeding with measurements, ensure that the test specimen and the prism have reached the equilibrium temperature and that the instrument has been properly checked and calibrated against a standard provided by the manufacturer (see Refractive Index 831). Convert the refractive index value to approximate percent solids value using Table 1 and Table 2. [noteTable 1 covers the approximate total solids levels of these products in commerce. If the ash or dextrose equivalent of the test specimen differs from that of the product in Table 1, use Table 2 for the ash and dextrose equivalent correction.] The total solids value is not less than 70.0%.
Table 1. Reference for Converting the Refractive Index to Approximate Percent Solids
Table 2. Ash and Dextrose Equivalent (DE) Corrections for Corn Syrup: Changes in Refractive Index for an Increase in Dry Substance (DS)
Limit of sulfur dioxide Transfer about 100 g of Syrup, accurately weighed, to a 250-mL conical flask, add 100 mL of water, and mix. Cool to between 5 and 10. While stirring with a magnetic stirrer, add 10 mL of cold (between 5 and 10) 1.5 N sodium hydroxide. Stir for an additional 20 seconds, and add 10 mL of starch indicator solution, prepared as follows. Mix 10 g of soluble starch with 50 mL of cold water, transfer to 1000 mL of boiling water, stir until completely dissolved, cool, and add 1 g of salicylic acid preservative. [noteDiscard this solution after 1 month.] Add 10 mL of cold (between 5 and 10) 2.0 N sulfuric acid, and titrate immediately with 0.005 N iodine VS until a light blue color persists for 1 minute (see Titrimetry 541). Perform a blank determination, using 200 mL of water treated similarly to the solution under test, and make any necessary correction. Each mL of 0.005 N iodine is equivalent to 0.16 mg of SO2: not more than 40 µg per g is found.
Limit of lead [noteFor the preparation of all aqueous solutions and for the rinsing of glassware before use, employ water that has been passed through a strong-acid, strong-base, mixed-bed ion-exchange resin before use. For digestion, use acid-cleaned, high-density polyethylene, polypropylene, polytef, or quartz tubes. Select all reagents to have as low a content of lead as practicable, and store all reagent solutions in borosilicate glass containers. Cleanse glassware before use by soaking in warm 8 N nitric acid for 30 minutes and rinsing with deionized water. Store final diluted solutions in acid-cleaned plastic or polytef tubes or bottles.]
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, 50, 25, and 10 ng per mL, respectively.
Test solution [notePerform this procedure in a fume hood.] Transfer about 1.5 g of Syrup, accurately weighed, to a digestion tube, and add 0.75 mL of nitric acid to the tube. Warm the solution slowly (to avoid spattering) to between 90 and 95. Heat until all brown vapors have dissipated and any rust-colored tint has disappeared from the tube (20 to 30 minutes). Cool, add 0.5 mL of 50% hydrogen peroxide, dropwise, to the solution, heat to between 90 and 95 for 5 minutes, and cool. Add a second 0.5-mL portion of 50% hydrogen peroxide dropwise to the solution, and heat between 90 and 100 until clear (5 to 10 minutes). Cool and transfer the solution to a 10-mL volumetric flask. Rinse the digestion tube with 5% nitric acid, add the rinse 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 [noteUse 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. [noteThe 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:
0.01(C/W)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 0.5 µg per g.
Assay for reducing sugars (dextrose equivalent)
Apparatus Mount a ring support on a ring stand 1 to 2 inches above a gas burner, and mount a second ring 6 to 7 inches above the first. Place 6-inch open-wire gauze on the lower ring to support a 250-mL conical flask, and place a 4-inch watch glass with a center hole on the upper ring to deflect heat. Attach a 25-mL buret to the ring stand so that the tip just passes through the watch glass centered above the flask. Place an indirectly lighted white surface behind the assembly for observing the endpoint.
Standard preparation Dissolve an accurately weighed quantity of USP Dextrose RS in water, and dilute quantitatively with water to obtain a solution having a known concentration of about 6 mg per mL.
Assay preparation Transfer about 5 g of Syrup, accurately weighed, to a 500-mL volumetric flask, add water to volume, and mix.
Procedure Transfer 25.0 mL portions of alkaline cupric tartrate TS to each of two flasks, and boil. Immediately place one flask on the wire gauze of the Apparatus, and adjust the burner so that the boiling point is reached in about 2 minutes. Titrate with the Standard preparation to within 0.5 mL of the anticipated endpoint. Heat the flask, with swirling, boil moderately for 2 minutes, and add 2 drops of methylene blue solution (1 in 100). Immediately add about 2 drops of the Standard preparation from the buret, and bring to a boil. Allow the cuprous oxide to settle slightly, and observe the color of the supernatant. Complete the titration within 1 minute by adding the Standard preparation dropwise, and boiling after each addition to the disappearance of the blue color, as determined by viewing against a white background in daylight or under equivalent illumination. If more than 0.5 mL of the titrant is required after the addition of the indicator, repeat the titration, adding the necessary volume of titrant before adding the indicator. Bring the contents of the second flask to a boil, and similarly titrate with the Assay preparation. Calculate the percentage of reducing sugars as d-glucose, calculated on the dried basis, in the portion of Syrup taken by the formula:
(100/0.01A)(CS / CU)(VS / VU)in which A is the percentage of dry solids in Syrup measured by the refractive index; CS is the concentration, in mg per mL, of USP Dextrose RS in the Standard preparation; CU is the concentration, in mg per mL, of Syrup in the Assay preparation; and VS and VU are the titrated volumes, in mL, of the Standard preparation and the Assay preparation, respectively.NF27
Auxiliary Information Please check for your question in the FAQs before contacting USP.
USP32NF27 Page 1211Pharmacopeial Forum: Volume No. 33(6) Page 1240