Zinc and Vitamin C Lozenges
DEFINITION
Zinc and Vitamin C Lozenges contain NLT 90.0% and NMT 110.0% of the labeled amount of zinc (Zn) derived from substances generally recognized as safe and furnishing an ionizable form of zinc; and NLT 90.0% and NMT 120.0% of the labeled amount of vitamin C, as ascorbic acid (C6H8O6), sodium ascorbate (C6H7NaO6), or calcium ascorbate dihydrate (C12H14CaO12·2H2O). It contains no other vitamins or minerals for which nutritional value is claimed. It may contain other labeled added substances or additional ingredients in amounts that are unobjectionable.
IDENTIFICATION
• A.
Analysis:
Proceed as directed in Strength for Content of Zinc.
Acceptance criteria:
The Sample solution produces line emissions or absorptions at the characteristic wavelengths for zinc.
• B.
Analysis:
Triturate a quantity of finely powdered Lozenges with sufficient alcohol to obtain a solution containing the equivalent of 20 mg/mL of ascorbic acid, sodium ascorbate, or calcium ascorbate dihydrate, and filter. Add 1 mL of 0.1 N hydrochloric acid to 4 mL of the filtrate from Lozenges containing sodium ascorbate or calcium ascorbate.
Acceptance criteria:
A portion of the filtrate reduces alkaline cupric tartrate TS slowly at room temperature but more readily upon heating.
STRENGTH
• Content of Zinc
Procedure 1
[Note—A standard stock solution is commercially available at different zinc concentrations, which may be used for preparation of Standard stock solution. Necessary volumetric adjustment can be made in the Standard solution. Concentrations of the Standard solution and the Sample solution may be modified to fit the linear or working range of the instrument. ]
Standard stock solution:
Dissolve 625 mg of zinc oxide, weighed, and previously ignited to constant weight, in 10 mL of nitric acid, and add water to make 500.0 mL. This solution contains 1000 µg/mL of zinc.
Standard solution:
To a 500-mL volumetric flask add 200 mL of water and 10 mL of nitric acid, and mix thoroughly. Pipet 10.0 mL of the Standard stock solution into the volumetric flask, and dilute with water to volume to obtain a solution having a known concentration of about 20 µg/mL of zinc.
Sample solution:
Weigh and finely powder NLT 20 Lozenges. Transfer an accurately weighed portion of the powdered Lozenges, equivalent to about 0.1 g of zinc, to a 50-mL flask. Add 10 mL of nitric acid, and heat the solution on a hot plate to boil gently, during which process fuming evolves. Boil the solution for an additional 30 min with constant swirling, during which no fuming should be observed. Cool the solution to room temperature, quantitatively transfer all of the solution to a 500-mL volumetric flask, dilute with water to volume, and mix. Pipet 25.0 mL of this solution into a 250-mL volumetric flask, add 5 mL of nitric acid, dilute with water to volume, mix, and filter.
Inductively coupled plasma system
(See Plasma Spectrochemistry 
730
.)
730.)
Mode:
Atomic emission spectroscopy
Analytical wavelength:
206.20 nm
[Note—The operating conditions may be developed and optimized based on the manufacturer's recommendation. A typical setting includes radio frequency (RF) power of about 1300 watts, argon torch flow of about 15 L/min, argon auxiliary flow of about 0.2 L/min, and a nebulizer flow rate of about 0.8 L/min. ]
Blank:
2% nitric acid solution
Analysis
Samples:
Standard solutions, Sample solution, and Blank
Calculate the percentage of the labeled amount of zinc (Zn) in the portion of Lozenges taken:
Result = (rU/rS) × (CS/CU) × 100
| rU | = | = response from the Sample solution |
| rS | = | = response from the Standard solution |
| CS | = | = concentration of zinc in the Standard solution (µg/mL) |
| CU | = | = nominal concentration of zinc in the Sample solution (µg/mL) |
Acceptance criteria:
90.0%–110.0% of the labeled amount of zinc
Procedure 2
Standard stock solution A:
Dissolve zinc oxide in 5 M hydrochloric acid with warming, if necessary, to obtain a solution with a concentration of 3.89 mg/mL. Dilute with water to obtain a solution with a concentration of 1000 µg/mL of zinc.
Standard stock solution B:
50 µg/mL of zinc from Standard stock solution A in 0.125 N hydrochloric acid
Standard solutions:
Transfer 1.0, 2.0, 3.0, 4.0, and 5.0 mL of Standard stock solution B to separate 100-mL volumetric flasks. Dilute the contents of each flask with 0.125 N hydrochloric acid to volume to obtain solutions containing 0.5, 1.0, 1.5, 2.0, and 2.5 µg/mL of zinc.
Sample solution:
Finely powder NLT 20 Lozenges. Transfer an equivalent to 5 Lozenges to a porcelain crucible. Heat the crucible in a muffle furnace maintained at 550
for 6–12 h, and cool. Add 60 mL of hydrochloric acid, and boil gently on a hot plate or steam bath for 30 min, intermittently rinsing the inner surface of the crucible with 6 N hydrochloric acid. Cool, and quantitatively transfer the contents of the crucible to a 100-mL volumetric flask. Rinse the crucible with small portions of 6 N hydrochloric acid, and add the rinsings to the flask. Dilute with water to volume, and filter, discarding the first 5 mL of the filtrate. Dilute this solution quantitatively with 0.125 N hydrochloric acid to obtain a nominal concentration of 2 µg/mL of zinc.
for 6–12 h, and cool. Add 60 mL of hydrochloric acid, and boil gently on a hot plate or steam bath for 30 min, intermittently rinsing the inner surface of the crucible with 6 N hydrochloric acid. Cool, and quantitatively transfer the contents of the crucible to a 100-mL volumetric flask. Rinse the crucible with small portions of 6 N hydrochloric acid, and add the rinsings to the flask. Dilute with water to volume, and filter, discarding the first 5 mL of the filtrate. Dilute this solution quantitatively with 0.125 N hydrochloric acid to obtain a nominal concentration of 2 µg/mL of zinc.
Instrumental conditions
Mode:
Atomic absorption spectrophotometry
Analytical wavelength:
213.8 nm
Lamp:
Zinc hollow-cathode
Flame:
Air–acetylene
Blank:
0.125 N hydrochloric acid
Analysis
Samples:
Standard solutions and Sample solution
Determine the absorbances of the solutions against the Blank. Plot the absorbances of the Standard solutions versus the concentration, in µg/mL, of zinc, and draw the straight line best fitting the five plotted points. From the graph so obtained, determine the concentration, C, in µg/mL, of zinc in the Sample solution.
Calculate the percentage of the labeled amount of zinc (Zn) in the portion of Lozenges taken:
Result = (C/CU) × 100
| C | = | = determined concentration of zinc in the Sample solution (µg/mL) |
| CU | = | = nominal concentration of zinc in the Sample solution (µg/mL) |
Acceptance criteria:
90.0%–110.0% of the label claim
• Content of Vitamin C
Sample solution:
Transfer NLT 20 Lozenges to a 1000-mL volumetric flask containing 250 mL of metaphosphoric–acetic acids TS. Insert the stopper in the flask, and shake by mechanical means for 30 min or until the lozenges have disintegrated completely. Dilute with water to volume. Transfer a portion of the solution to a centrifuge tube, and centrifuge until a clear supernatant is obtained. Quantitatively dilute the clear supernatant with water, if necessary, to obtain a solution containing 0.5 mg/mL of ascorbic acid.
Blank:
A mixture of 5.5 mL of metaphosphoric–acetic acids TS and 15 mL of water
Titrimetric system
(See Titrimetry 541.)
541.)
Mode:
Direct titration
Titrant:
Standard dichlorophenol–indophenol VS
Endpoint detection:
Visual, a rose-pink color that persists for at least 5 s
Analysis:
Transfer a volume of the Sample solution, equivalent to 2 mg of ascorbic acid, into a 50-mL conical flask. Add 5 mL of metaphosphoric–acetic acids TS, and titrate with Titrant. Correct for the volume of the Titrant consumed by the Blank.
Calculate the percentage of the labeled amount of ascorbic acid (C6H8O6) in the portion of the Lozenges taken:
Result = {[(VS 
VB) × F]/W} × 100
VB) × F]/W} × 100| VS | = | = Titrant volume consumed by the Sample solution (mL) |
| VB | = | = Titrant volume consumed by the Blank (mL) |
| F | = | = ascorbic acid equivalent of the Titrant (mg/mL) |
| W | = | = nominal weight of ascorbic acid taken for Analysis (mg) |
Acceptance criteria:
90.0%–120.0% of the labeled amount
SPECIFIC TESTS
• Microbial Enumeration Tests 2021:
The total aerobic microbial count does not exceed 103 cfu/g, and the total combined yeasts and molds count does not exceed 102 cfu/g.
2021:
The total aerobic microbial count does not exceed 103 cfu/g, and the total combined yeasts and molds count does not exceed 102 cfu/g.
• Absence of Specified Microorganisms 2022:
It meets the requirements of the test for absence of Escherichia coli.
2022:
It meets the requirements of the test for absence of Escherichia coli.
PERFORMANCE TESTS
• Disintegration and Dissolution 2040
2040
Medium:
0.1 N hydrochloric acid; 900 mL
Apparatus 2:
75 rpm
Time:
60 min
Analysis:
Determine the amount of zinc (Zn) and vitamin C dissolved, using the procedures in Strength for Content of Zinc and Content of Vitamin C, making any necessary volumetric adjustments. [Note—Proceed without delay in the vitamin C determination. ]
Calculate the percentage of the labeled amount of zinc (Zn) dissolved:
Result = C × (VM/a) × (D/L) × 100
| C | = | = measured concentration of Zinc in the Sample solution (mg/mL) |
| VM | = | = volume of Medium, 900 mL |
| a | = | = aliquot of solution under test taken (mL) |
| D | = | = dilution factor to prepare the Sample solution from the aliquot taken |
| L | = | = labeled amount of zinc (mg/Tablet) |
Calculate the percentage of the labeled amount of vitamin C, as ascorbic acid (C6H8O6), dissolved:
Result = (VS VB) × F × [(VM/a)/L] × 100
VB) × F × [(VM/a)/L] × 100| VS | = | = Titrant volume consumed by the Sample solution (mL) |
| VB | = | = Titrant volume consumed by the Blank (mL) |
| F | = | = concentration of the Titrant in terms of the equivalent of ascorbic acid (mg/mL) |
| VM | = | = volume of Medium, 900 mL |
| a | = | = volume of the aliquot taken for Analysis |
| L | = | = labeled amount of ascorbic acid (mg/Tablet) |
Tolerances:
NLT 75% of the labeled amount of zinc (Zn) and vitamin C is dissolved.
• Weight Variation 2091:
Meet the requirements
2091:
Meet the requirements
ADDITIONAL REQUIREMENTS
• Packaging and Storage:
Preserve in well-closed containers.
• Labeling:
The label states the quantity of zinc and vitamin C as ascorbic acid in mg per Lozenge, and the salt form of zinc and the chemical form of vitamin C present in the Lozenges.
Auxiliary Information—
Please check for your question in the FAQs before contacting USP.
| Topic/Question | Contact | Expert Committee |
|---|---|---|
| Monograph | Natalia Davydova
Scientific Liaison 1-301-816-8328 |
(DS2010) Monographs - Dietary Supplements |
| 2021 |
Radhakrishna S Tirumalai, Ph.D.
Principal Scientific Liaison 1-301-816-8339 |
(GCM2010) General Chapters - Microbiology |
| 2022 |
Radhakrishna S Tirumalai, Ph.D.
Principal Scientific Liaison 1-301-816-8339 |
(GCM2010) General Chapters - Microbiology |
USP35–NF30 Page 1664
Pharmacopeial Forum: Volume No. 34(2) Page 317