Malic Acid
(mal' ik as' id).
DEFINITION
Malic Acid contains NLT 99.0% and NMT 100.5% of C4H6O5.
IDENTIFICATION
• A. Infrared Absorption 197K:
On undried sample
ASSAY
• Procedure
Sample:
2 g
Titrimetric system
(See Titrimetry 541.)
Mode:
Direct titration
Titrant:
1 N sodium hydroxide VS
Endpoint detection:
Visual
Analysis:
Dissolve the Sample in 40 mL of recently boiled and cooled water. Add phenolphthalein TS, and titrate to the first appearance of a faint pink color that persists for NLT 30 s. Perform a blank determination.
Calculate the percentage of malic acid (C4H6O5) in the Sample taken:
Result = [(V B) × N × F × 100]/W
Acceptance criteria:
99.0%100.5%
IMPURITIES
• Residue on Ignition 281:
NMT 0.1%
• Heavy Metals, Method II 231:
NMT 20 ppm
• Fumaric and Maleic Acids
Mobile phase:
0.01 N sulfuric acid
System suitability solution:
1 mg/mL of Malic Acid, 10 µg/mL of USP Fumaric Acid RS, and 4 µg/mL of USP Maleic Acid RS in Mobile phase
Standard solution:
5.0 µg/mL of USP Fumaric Acid RS and 2.0 µg/mL of USP Maleic Acid RS in Mobile phase
Sample solution:
1.0 mg/mL of Malic Acid in Mobile phase
Chromatographic system
Mode:
LC
Detector:
UV 210 nm
Column:
6.5-mm × 30-cm; packing L17
Column temperature:
37 ± 1
Flow rate:
0.6 mL/min
Injection size:
20 µL
System suitability
Sample:
System suitability solution
[NoteThe relative retention times for maleic acid, malic acid, and fumaric acid are 0.6, 1.0, and 1.5, respectively. ]
Suitability requirements
Resolution:
NLT 2.5 for the maleic acid and malic acid peaks; NLT 7.0 for the malic acid and fumaric acid peaks
Relative standard deviation:
NMT 2.0% for the maleic acid peak
Analysis
Samples:
Standard solution and Sample solution
Calculate the percentage of maleic acid and of fumaric acid in the portion of Malic Acid taken:
Result = (rU/rS) × (CS/CU) × 100
Acceptance criteria
Fumaric acid:
NMT 1.0%
Maleic acid:
NMT 0.05%
• Water-Insoluble Substances
Sample:
25 g
Analysis:
Dissolve the Sample in 100 mL of water, filter the solution through a tared filtering crucible, wash the filter with hot water, and dry at 100 to constant weight.
Acceptance criteria:
The increase in weight is NMT 25 mg (0.1%).
ADDITIONAL REQUIREMENTS
• Packaging and Storage:
Preserve in well-closed containers.
Auxiliary Information
Please check for your question in the FAQs before contacting USP.
USP35NF30 Page 1851
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