Alcohol

Alcohol

Proposed For Comment Version 0.2

C2H6O                                                                                               46.07

Ethanol;    
Ethyl alcohol     [64-17-5].


 

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 C2H5OH.

 

IDENTIFICATION

A. It meets the requirements of the test for Specific Gravity <841>.

B. Infrared Absorption <197F> or <197S>: Neat

 

IMPURITIES

Inorganic Impurities

Limit of Nonvolatile Residue

Analysis: Evaporate 100 mL in a tared dish on a water bath, dry at 100°–105° for 1 h, and obtain the weight of the residue

Acceptance criteria: NMT 2.5 mg

Organic Impurities

Procedure

Sample solution A: Alcohol (substance under test)

Sample solution B: 300 ppm of 4-methylpentan-2-ol in Sample solution A

Standard solution A: 200 ppm of methanol in Sample solution A

Standard solution B: 10 ppm of methanol and 10 ppm of acetaldehyde in Sample solution A

Standard solution C: 30 ppm of acetal in Sample solution A

Standard solution D: 2 ppm of benzene in Sample solution A

Chromatographic system

(See Chromatography <621>, System Suitability.)

Mode: GC

Detector: Flame ionization

Column: 0.32-mm × 30-m fused silica capillary column bonded with a 1.8-μm layer of phase G43 (similar to DB-624) 

Split ratio: 20:1

Temperature

Detector: 280°

Injector: 200°

Column: See the temperature program table below.

 

Initial
Temperature
(º)

Temperature Ramp
(º /min)

Final
Temperature
(º)

Hold Time at Final
Temperature
(min)

40

0

40

12

40

10

240

10

  

Linear velocity: 35 cm/s

Carrier gas: Helium

Injection size: 1.0 μL

System suitability

Sample: Standard solution B

Suitability requirements

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

Analysis

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

 

Methanol calculation

 

Result = (rU/rS)

 

rU = peak area of methanol from Sample solution A

rS = peak area of methanol from Standard solution A

 

Acetaldehyde and Acetal calculation

 

Result = {[AE/(AT AE)] × CS} + {[DE/(DT DE)] × CU}

 

AE = area of the acetaldehyde peak from Sample solution A

AT = area of the acetaldehyde peak from Standard solution B

CS = concentration of acetaldehyde added in Standard solution B, 10 ppm

DE = area of the acetal peak from Sample solution A

DT = area of the acetal peak from Standard solution C

CU = concentration of acetal added in Standard solution C, 30 ppm

 

Benzene calculation

 

Result = [BE/(BT BE)] × CS

 

 

BE = area of the benzene peak from Sample solution A

BT = area of the benzene peak from Standard solution D

CS = concentration of benzene added in Standard solution D, 2 ppm

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

 

Other impurities calculation

 

Result = (rU/rM) × CM

 

rU = peak area of each impurity in Sample solution B

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

CM = concentration of 4-methylpentan-2-ol in Sample solution B

 

Acceptance criteria: See Impurity Table 1.

 

 

                    Impurity Table 1

Name

Acceptance Criteria

Methanol

NMT 0.5, corresponding to 200 ppm

Acetaldehyde and Acetal

NMT 10 ppm, expressed as acetaldehyde

Benzene

NMT 2 ppm

Sum of all other impuritiesa

NMT 300 ppm

  aDisregard any peaks of less than 9 ppm.

 

SPECIFIC TESTS

• 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 C2H5OH

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 absorption curve is smooth

Clarity of Solution

[NOTE—The Sample solution is to be compared to Reference suspension A and to water in diffused daylight 5 min after preparation of Reference suspension A.]

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

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

Primary opalescent suspension: Transfer 25.0 mL of Hydrazine solution to the Methenamine solution in the 100-mL glass-stoppered flask. Mix, and allow to stand for 24 h. [NOTE—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 opalescent suspension to a 1000-mL volumetric flask, and dilute with water to volume. [NOTE—This suspension should not be used beyond 24 h after preparation.]

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

Reference 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.

Analysis: Transfer a sufficient portion of Sample solution A and Sample solution B to separate test tubes of colorless, transparent, neutral glass with a flat base and an internal diameter of 15–25 mm to obtain a depth of 40 mm. Similarly transfer portions of Reference suspension A, Reference suspension B, and water to separate matching test tubes. Compare Sample solution A, Sample solution B, Reference suspension A, Reference suspension B, and water in diffused daylight, viewing vertically against a black background. (See Spectrophotometry and Light-Scattering <851>, Visual Comparison.)

[NOTE—The diffusion of light must be such that Reference suspension A can readily be distinguished from water, and that Reference suspension B can readily be distinguished from Reference 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 Reference suspension A.

 • Acidity or Alkalinity

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

Analysis: To 20 mL of alcohol 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 ppm, expressed as acetic acid).

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 g/L).

Standard solution: Transfer 1.0 mL of Standard stock solution to a 100-mL volumetric flask, and dilute with dilute hydrochloric acid (10 g/L). [NOTE—Prepare the Standard solution immediately before use.]

Sample solution: Substance to be examined

Analysis: Transfer a sufficient portion of the Sample solution to a test tube of colorless, transparent, neutral glass with a flat base and an internal diameter of 15–25 mm to obtain a depth of 40 mm. Similarly transfer portions of the Standard solution and water to separate, matching test tubes. Compare the Sample solution, Standard solution, and water in diffused daylight, viewing vertically against a white background. (See Spectrophotometry and Light-Scattering <851>, Visual Comparison.)

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

 

ADDITIONAL REQUIREMENTS

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

• USP Reference Standards  <11>

USP Alcohol RS

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Other Versions

Final Authorized Version 1.0