Alcohol

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

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

DOWNLOAD PDF HERE

Portions of this monograph that are national USP text, and are not part of the harmonized text, are marked with symbols to specify this fact.

C₂H₆O 46.07

Ethanol;

Ethyl alcohol CAS RN®: 64-17-5.

1 DEFINITION

Alcohol contains NLT 92.3% and NMT 93.8%, by weight, corresponding to NLT 94.9% and NMT 96.0%, by volume, at 15.56°, of Ethanol (C₂H₅OH).

2 IDENTIFICATION

A. It meets the requirements of the test for Specic Gravity 〈841〉.

B. Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197F or 197S: Neat

C. Limit of Methanol

[Note—This test must be performed to be in compliance with USP, in addition to Identication A and B above.] Sample solution A, Standard solution A, Standard solution B, Chromatographic system, and System suitability: Proceed as directed in Organic Impurities.

Analysis: Proceed as directed in the Organic Impurities test, Methanol calculation.

Acceptance criteria: Meets the requirements in Table 2 for methanol.

3 IMPURITIES

Limit of Nonvolatile Residue

Sample: 100 mL of Alcohol

Analysis: Evaporate the Sample in a tared dish on a water bath, and dry at 100°–105° for 1 h.

Acceptance criteria: The weight of the residue is NMT 2.5 mg.

Organic Impurities

Sample solution A: Alcohol (substance under test)

Sample solution B: 300 µL/L of 4-methylpentan-2-ol in Sample solution A

Standard solution A: 200 µL/L of methanol in Sample solution A

[Note—To be prepared for use in Identication C]

Standard solution B: 10 µL/L each of methanol and acetaldehyde in Sample solution A

Standard solution C: 30 µL/L of acetal in Sample solution A

Standard solution D: 2 µL/L of benzene in Sample solution A

3.1 Chromatographic system

(See Chromatography 〈621〉, System Suitability.)

Mode: GC

Detector: Flame ionization

Column: 0.32-mm × 30-m fused-silica capillary; bonded with a 1.8-µm layer of phase G43

Injection type: Split; split ratio 20:1

Temperatures

Injection port: 200°

Detector: 280°

Column: See Table 1.

Table 1

Linear velocity: 35 cm/s

Carrier gas: Helium

Injection volume: 1.0 µL

System suitability

Sample: Standard solution B

Suitability requirements

Resolution: NLT 1.5 between the rst major peak (acetaldehyde) and the second major peak (methanol)

3.2 Analysis

Samples: Sample solution A, Sample solution B, Standard solution A, Standard solution B, Standard solution C, and Standard solution D Methanol calculation

[Note—To be performed as a part of Identication C.]  

Result = (r_U /r_S )

r_U = peak area of methanol from Sample solution A

r_S = peak area of methanol from Standard solution A

OFFICIAL

Acetaldehyde calculation (sum of acetaldehyde and acetal)

Result = {[A_E /(A_T− A_E )] × C_A } + {[D_E /(D_T − D_E )] × C_D × (M_r1 /M_r2 )}

A_E = peak area of acetaldehyde from Sample solution A  

A_T= peak area of acetaldehyde from Standard solution B

C_A = concentration of acetaldehyde in Standard solution B (µL/L)

D_E = peak area of acetal from Sample solution A

D_T = peak area of acetal from Standard solution C

C_D = concentration of acetal in Standard solution C (µL/L)

M_r1 = molecular weight of acetaldehyde, 44.05

M_r2 = molecular weight of acetal, 118.2

Benzene calculation

Result = [B_E /(B_T − B_E )] × C_B

B_E = peak area of benzene from Sample solution A  

B_T = peak area of benzene from Standard solution D

C_B = concentration of benzene in Standard solution D (µL/L)

[Note—If necessary, the identity of benzene can be conrmed using another suitable chromatographic system (stationary phase with a different polarity).]

Any other impurity calculation

Result = (r_U /r_M ) × C_M

r_U = peak area of each impurity in Sample solution B  

r_M = peak area of 4-methylpentan-2-ol in Sample solution B  

C_M = concentration of 4-methylpentan-2-ol in Sample solution B (µL/L)

Acceptance criteria: See Table 2.

Table 2

^a Disregard any peaks of less than 9 µL/L (0.03 times the area of the peak corresponding to 4-methylpentan-2-ol in Sample solution B).

4 SPECIFIC TESTS

Change to read:

Specific Gravity 〈841〉: 0.812–0.816 at 15.56°, indicating 92.3%–93.8%, by weight, or 94.9%–96.0%, by volume, of ethanol (C H OH) 2 5

[Note—In the event that a temperature of 15.56° cannot be reached, the Alcoholometric Table found in the Reagents and Reference Tables section of USP-NF can be used to provide the conversion factors needed to complete this test at other temperatures. ] (USP 1-Dec-2021)

4.1 Ultraviolet Absorption

Analytical wavelength: 235–340 nm

Cell: 5 cm

Reference: Water Acceptance criteria Absorbance: NMT 0.40 at 240 nm; NMT 0.30 between 250 nm and 260 nm; NMT 0.10 between 270 nm and 340 nm Curve: The spectrum shows a steadily descending curve with no observable peaks or shoulders.

4.2 Clarity of Solution

[Note—Compare each Sample solution to Standard suspension A and to water in diffused daylight 5 min after preparation of Standard suspension A.]

Hydrazine solution: 10 mg/mL of hydrazine sulfate in water. Allow to stand for 4–6 h.

Methenamine solution: Transfer 2.5 g of methenamine to a 100-mL glass-stopper ask, add 25.0 mL of water, insert the glass stopper, and mix to dissolve.

Primary opalescence suspension: Transfer 25.0 mL of Hydrazine solution to the Methenamine solution in the 100-mL glass-stopper ask. Mix, and allow to stand for 24 h. This suspension is stable for 2 months, provided it is stored in a glass container free from surface defects. The suspension must not adhere to the glass and must be well mixed before use.

Opalescence standard: Transfer 15.0 mL of the Primary opalescence suspension to a 1000-mL volumetric ask, and dilute with water to volume. This suspension should not be used beyond 24 h after preparation.

Standard suspension A: Opalescence standard and water (1 in 20)

Standard suspension B: Opalescence standard and water (1 in 10)

Sample solution A: Substance to be examined

Sample solution B: Dilute 1.0 mL of Sample solution A with water to 20 mL, and allow to stand for 5 min before testing. Blank: Water

Analysis

Samples: Standard suspension A, Standard suspension B, Sample solution A, Sample solution B, and Blank

Transfer a sucient portion of Sample solution A and Sample solution B to separate test tubes of colorless, transparent, neutral glass with a at base and an internal diameter of 15–25 mm to obtain a depth of 40 mm. Similarly transfer portions of Standard suspension A, Standard suspension B, and Blank to separate matching test tubes. Compare the Samples in diffused daylight, viewing vertically against a black background (see Visual Comparison 〈630〉). The diffusion of light must be such that Standard suspension A can readily be distinguished from water, and Standard suspension B can readily be distinguished from Standard suspension A.

Acceptance criteria: Sample solution A and Sample solution B show the same clarity as that of water or their opalescence is not more pronounced than that of Standard suspension A.

4.3 Acidity or Alkalinity

Phenolphthalein solution: Dissolve 0.1 g of phenolphthalein in 80 mL of alcohol, and dilute with water to 100 mL. Sample: 20 mL of Alcohol

Analysis: To the Sample add 20 mL of freshly boiled and cooled water and 0.1 mL of Phenolphthalein solution. The solution is colorless. Add 1.0 mL of 0.01 N sodium hydroxide.

Acceptance criteria: The solution is pink (30 µL/L, expressed as acetic acid).

4.4 Color of Solution

Standard stock solution: Combine 3.0 mL of ferric chloride CS, 3.0 mL of cobaltous chloride CS, 2.4 mL of cupric sulfate CS, and 1.6 mL of dilute hydrochloric acid (10 mg/mL).

Standard solution: Transfer 1.0 mL of Standard stock solution to a 100-mL volumetric ask, and dilute with dilute hydrochloric acid (10 mg/mL). Prepare the Standard solution immediately before use.

Sample solution: Substance under test

Blank: Water

Analysis

Samples: Standard solution, Sample solution, and Blank

Transfer a sucient portion of the Sample solution to a test tube of colorless, transparent, neutral glass with a at base and an internal diameter of 15–25 mm to obtain a depth of 40 mm. Similarly transfer portions of the Standard solution and Blank to separate, matching test tubes. Compare the Samples in diffused daylight, viewing vertically against a white background (see Visual Comparison 〈630〉).

Acceptance criteria: The Sample solution has the appearance of water or is not more intensely colored than the Standard solution.

5 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in tight containers, protected from light.

USP Reference Standards 〈11〉

USP Alcohol RS