Maltol

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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C₆H₆O₃ 126.11

4H-Pyran-4-one, 3-hydroxy-2-methyl-;

3-Hydroxy-2-methyl-4H-pyran-4-one CAS RN^®: 118-71-8.

1 DEFINITION

Maltol contains NLT 98.0% and NMT 102.0% of 3-hydroxy-2-methyl-4H-pyran-4-one, calculated on the anhydrous basis.

2 IDENTIFICATION

A. SPECTROSCOPIC IDENTIFICATION TESTS (197), Infrared Spectroscopy: 197K

B. CHROMATOGRAPHIC IDENTITY

Analysis: Examine the chromatograms obtained in the Assay.

Acceptance criteria: The retention time of the major peak of the Sample solution corresponds to that of the Standard solution.

3 ASSAY

3.1 PROCEDURE

Diluent: Alcohol, absolute

Internal standard solution: 0.5 mg/mL of USP Benzyl Alcohol RS (internal standard) in Diluent

System suitability solution: 1.0 mg/mL of USP Maltol RS and 0.2 mg/mL of USP Ethyl Maltol RS in Internal standard solution

Standard solution: 1.0 mg/mL of USP Maltol RS in Internal standard solution

Sample solution: 1.0 mg/mL of Maltol in Internal standard solution

3.2 Chromatographic system

(See Chromatography (621), System Suitability.)

Mode: GC

Detector: Flame ionization

Column: 0.32-mm x 30-m capillary; bonded with a 0.5-µm layer of phase G42

Temperatures

Detector: 300°

Injection port: 280°

Column: See Table 1.

Table 1

Carrier gas: Helium

Flow rate: 2 mL/min (constant flow mode)

Injection volume: 1.0 µL

Injection type: Split, split ratio 10:1

Liner: Ultra inert with glass wool, low pressure drop¹

3.3 System suitability

Samples: System suitability solution and Standard solution

[NOTE-The approximate relative retention time of ethyl maltol with reference to maltol is 1.2.]

Suitability requirements

Resolution: NLT 1.5 between the maltol and ethyl maltol peaks, System suitability solution

Tailing factor: NMT 2.0, determined from the maltol peak, System suitability solution

Relative standard deviation: NMT 1% for the peak response ratio of maltol to the internal standard, Standard solution

3.4 Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of Maltol in the portion of the sample taken:

Result = (R_U/R_S) x (C_S/C_U) x 100

R_U = peak response ratio of maltol to the internal standard from the Sample solution

R_S = peak response ratio of maltol to the internal standard from the Standard solution

C_S = concentration of USP Maltol RS in the Standard solution (mg/mL)

C_U = concentration of Maltol in the Sample solution (mg/mL)

Acceptance criteria: 98.0%-102.0% on the anhydrous basis

4 IMPURITIES

4.1 ORGANIC IMPURITIES

Diluent and Chromatographic system: Proceed as directed in the Assay.

Protectant solution: 1.0 mg/mL of 4-hydroxy-6-methyl-2-pyrone (protectant) in Diluent

System suitability solution: 1 mg/mL of USP Maltol RS and 0.2 mg/mL of USP Ethyl Maltol RS in Protectant solution

Standard solution: 0.02 mg/mL of USP Maltol RS in Protectant solution

Sample solution: 20.0 mg/mL of Maltol in Protectant solution

System suitability

Samples: System suitability solution and Standard solution

[NOTE-The approximate relative retention time of ethyl maltol with reference to maltol is 1.2.]

Suitability requirements

Resolution: NLT 1.5 between the maltol and ethyl maltol peaks, System suitability solution

Relative standard deviation: NMT 5.0%, determined from the maltol peak, Standard solution

Signal-to-noise ratio: NLT 10, determined from the maltol peak, Standard solution

Analysis

Samples: Standard solution and Sample solution

Calculate the percentage of each individual unidentified impurity in the portion of sample taken:

Result = (r_U/r_S) x (C_S/C_U) x 100

r_U = peak area of any individual unidentified impurity from the Sample solution

r_S = peak area of maltol from the Standard solution

C_S = concentration of USP Maltol RS in the Standard solution (mg/mL)

C_U = concentration of Maltol in the Sample solution (mg/mL)

Acceptance criteria: See Table 2.

Table 2

4.2 RESIDUE ON IGNITION (281)

NMT 0.2%, determined on 1.0 g

Change to read:

4.3 LEAD (251), Procedures, Procedure 1 (CN 1-JUN-2023)

NMT 10 ppm

5 SPECIFIC TESTS

5.1 MELTING RANGE OR TEMPERATURE (741), Procedures, Procedure for Class la

160°-164°

5.2 WATER DETERMINATION (921), Method I

NMT 0.5%

6 ADDITIONAL REQUIREMENTS

6.1 PACKAGING AND STORAGE

Preserve in tight containers protected from light, and avoid contact with metals. No storage requirements are specified.

6.2 USP REFERENCE STANDARDS (11)

USP Benzyl Alcohol RS

USP Ethyl Maltol RS

USP Maltol RS

¹ Agilent PN 5190-2295 liner has been used. Other equivalent liners can be also used.