Alpha Lipoic Acid Capsules
DEFINITION
Alpha Lipoic Acid Capsules contain NLT 90.0% and NMT 115.0% of the labeled amount of C8H14O2S2.
IDENTIFICATION
• The retention time of the major peak of the Sample solution corresponds to that of the Standard solution, as obtained in the test for Content of Alpha Lipoic Acid.
STRENGTH
• Content of Alpha Lipoic Acid
Mobile phase:
0.025 M phosphoric acid and acetonitrile (62:38)
Standard solution:
0.05 mg/mL of USP Alpha Lipoic Acid RS in acetonitrile and water (1:1)
Sample solution A (for hard gelatin Capsules):
Empty and mix thoroughly the contents of NLT 20 Capsules. Transfer a portion of the powder, equivalent to 100 mg of alpha lipoic acid, to a suitable container. Add 70 mL of a mixture of acetonitrile and water (1:1), and shake for 45 min by mechanical means. Transfer to a 100-mL volumetric flask, dilute with the mixture of acetonitrile and water (1:1) to volume, and filter a portion of this preparation, discarding the first 5 mL of the filtrate. Transfer 5.0 mL of the remaining filtrate to a 100-mL volumetric flask, and dilute with acetonitrile and water (1:1) to volume.
Sample solution B (for soft gelatin Capsules):
Using a suitable cutting instrument, open a number of Capsules equivalent to 500 mg of alpha lipoic acid from a counted number of opened Capsules. Transfer the contents and the shells to a suitable container with stopper, add 500.0 mL of a mixture of acetonitrile and water (1:1), and shake for 45 min by mechanical means. Filter a portion of this preparation, discarding the first 5 mL of the filtrate. Transfer 5.0 mL of the remaining filtrate to a 100-mL volumetric flask, and dilute with acetonitrile and water (1:1) to volume.
Chromatographic system
Mode:
LC
Detector:
UV 220 nm
Column:
3.9-mm × 30-cm; packing L1
Flow rate:
1.5 mL/min
Injection size:
20 µL
System suitability
Sample:
Standard solution
Suitability requirements
Column efficiency:
NLT 1300 theoretical plates
Tailing factor:
NMT 1.2 for alpha lipoic acid
Relative standard deviation:
NMT 1.0%
Analysis
Samples:
Standard solution and appropriate Sample solution
Calculate the percentage of alpha lipoic acid in the portion of Capsules taken:
Result = (rU/rS) × (CS/CU) × 100
| rU | = | = peak response from Sample solution A or Sample solution B |
| rS | = | = peak response from the Standard solution |
| CS | = | = concentration of USP Alpha Lipoic Acid RS in the Standard solution (mg/mL) |
| CU | = | = nominal concentration of alpha lipoic acid in Sample solution A or Sample solution B (mg/mL) |
Acceptance criteria:
90.0%–115.0%
PERFORMANCE TESTS
• Disintegration and Dissolution of Dietary Supplements 
2040
:
Meet the requirements for Dissolution
2040:
Meet the requirements for Dissolution
Medium:
Water; 900 mL
Apparatus 1 (for hard gelatin Capsules):
100 rpm
Apparatus 2 (for soft gelatin Capsules):
75 rpm
Time:
60 min
Standard solution:
1 mg/mL of USP Alpha Lipoic Acid RS in a mixture of acetonitrile and water (1:1). Dilute with water to obtain a concentration of 0.02 mg/mL.
Sample solution:
Withdraw a portion of the solution under test, and filter, discarding the first portion of the filtrate. Transfer an aliquot to a volumetric flask, and dilute with water to volume to obtain a solution having an expected concentration of 0.02 mg/mL of alpha lipoic acid.
Mobile phase and Chromatographic system:
Proceed as directed in the test for Content of Alpha Lipoic Acid.
Injection size:
50 µL
Analysis
Samples:
Standard solution and Sample solution
Calculate the percentage of alpha lipoic acid (C8H14O2S2) dissolved:
Result = (rU/rS) × (V × C × D/L) × 100
| rU | = | = peak area from the Sample solution |
| rS | = | = peak area from the Standard solution |
| V | = | = volume of dissolution Medium, 900 mL |
| C | = | = concentration of USP Alpha Lipoic Acid RS in the Standard solution (mg/mL) |
| D | = | = dilution factor of the sample |
| L | = | = label claim of alpha lipoic acid (mg/Capsule) |
Tolerances:
NLT 70% of the labeled amount of C8H14O2S2 is dissolved.
• Weight Variation of Dietary Supplements 2091:
Meet the requirements
2091:
Meet the requirements
ADDITIONAL REQUIREMENTS
• Packaging and Storage:
Preserve in well-closed containers.
• USP Reference Standards 11
11
USP Alpha Lipoic Acid RS 
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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 |
| Reference Standards | RS Technical Services 1-301-816-8129 rstech@usp.org |
USP35–NF30 Page 1367
Pharmacopeial Forum: Volume No. 36(1) Page 145