Dehydrated Alcohol

Dehydrated Alcohol

Proposed For Comment Version 0.2

C2H5OH                   46.07 

Ethanol;    
Ethyl alcohol          [64-17-5] 


 

DEFINITION

Dehydrated Alcohol contains NLT 99.2% by weight, corresponding to NLT 99.5% by volume, at 15.56º, of C2H5OH.

 

IDENTIFICATION

Specific Gravity  <841>: NMT 0.7962 at 15.56° , indicating NLT 99.2% of C2H5OH by weight  

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

 

IMPURITIES

•  Limit of Nonvolatile Residue

Sample: 100 mL of Dehydrated 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.

•  Volatile Impurities

Sample solution A: Substance to be examined

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

Standard solution B: 10 µL/L of methanol and 10 µg/L of 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

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 (similar to DB-624)

Split ratio: 1:20

Temperatures 

Injector: 200°

Detector: 280°

Column: See Table 1.

                                        

                                      Table 1

Initial

Temperature

(º)

Temperature

Ramp

(º/min)

Final

Temperature

(º)

Hold Time at Final
Temperature
(min)

40

0

40

12

40

10

240

10

 

Flow rate: 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 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 calculation (sum of acetaldehyde and acetal)

 

Result = {[AE/(AT – AE)] ×CA} + {[DE/(DT  DE)] ×CD}

 

AE  =  area of the acetaldehyde peak from Sample solution A

AT  =  area of the acetaldehyde peak from Standard solution B

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

DE  = area of the acetal peak from Sample solution A

DT  = area of the acetal peak from Standard solution C

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

Benzene calculation

 

Result = (BE/(BT BE)) ×CB

 

BE = area of the benzene peak from Sample solution A

BT = area of the benzene peak from Standard solution D

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

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

Any other impurity calculation

 

Result = (rU/rm) ×Cm

 

rU = peak area of each impurity from Sample solution B

rm = peak area of 4-methylpentan-2-ol from Sample solution B

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

Acceptance criteria: See Table 2.

 

                              Table 2 

 Name

Acceptance
Criteria

Methanol

NMT 0.5, corresponding to 200 µL/L

Acetaldehyde and acetal

10 µL/L, expressed as acetaldehyde

Benzene

2 µL/L

Sum of all other impuritiesa

300 µL/L

 a Disregard any peaks less than 9 µL/L

 

SPECIFIC TESTS

Ultraviolet Absorption

Analytical wavelength: 200–400 nm

Cell: 5 cm 

 Reference: Water

Acceptance criteria 

Absorbance: NMT 0.40 at 240 nm; NMT 0.30 between 250 and 260 nm; NMT 0.10 between 270 and 340 nm

Curve: Smooth between 235 and 340 nm

•  Clarity of Solution

[Note—The Sample solution is to be compared 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-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. 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. This suspension should not be used beyond 24 h after preparation.

Standard suspension A: Dilute 5.0 mL of Standard stock suspension with water to 100.0 mL.

Standard suspension B: Dilute 10.0 mL of Standard stock suspension with water to 100.0 mL.

Sample solution A: Substance to be examined

Sample solution B: 1.0 mL of Sample solution A diluted with water to 20 mL. 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 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 Standard suspension A, Standard suspension B, and Blank to separate matching test tubes. Compare samples in diffused daylight, viewing vertically against a black background (see Spectrophotometry and Light-Scattering <851>, Visual Comparison).

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

•  Acidity or Alkalinity

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

Sample solution: 20 mL of Dehydrated Alcohol

Analysis: To the Sample solution 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 µg/g, 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 hydrochloride acid (10 mg/mL).

Standard solution: 1.0 mL of Standard stock solution, diluted with dilute hydrochloric acid (10 mg/mL) to 100 mL. Prepare this immediately before use.

Sample solution: Substance to be examined

Analysis

Samples: Standard solution, Sample solution, and water

Transfer a sufficient portion of each of the Samples to individual 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. Compare the Samples 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 Dehydrated Alcohol RS

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Other Versions

Final Authorized Version 1.0