Standards:
Glycerin Standard (5g)
Diethylene Glycol (1g)
Ethylene Glycol (1g)
Internal Standard Solution: 2,2,2-Trichloroethanol (1 mg/mL: 4mL)

SAMPLES:
Glycerin Sample A (~1.2mL) at 0.5 g/ml in Methanol
Glycerin Sample B (~1.2mL) at 0.5 g/m in Methanol

1. Preparation of Standard Solution:

a. Standard Stock 1 - Transfer 50 mg of diethylene glycol, accurately weighed, to a 100mL volumetric flask and dilute with methanol to volume and mix.

b. Standard Stock 2 - Transfer 50 mg of ethylene glycol, accurately weighed, to a 100mL volumetric flask and dilute with methanol to volume and mix.

c. Standard Stock 3 - Transfer 2000mg of Glycerin, accurately weighed, to a 100mL volumetric flask and dilute with methanol to volume and mix.

d. Standard Solution - Transfer 1.0 mL of each stock solution prepared in steps 1a to 1c, and 1.0 mL of the internal standard solution into a 10 mL volumetric flask, dilute with methanol and mix.

The Standard Solution contains the following Concentrations:
    Glycerin: 2.0mg/mL
    Ethylene glycol: 0.050mg/mL
    Diethylene glycol: 0.050mg/mL
    2,2,2-Trichloroethanol: 0.10mg/mL

2. Preparation of the Test Solutions:

a. Test Solution A - Transfer 1.0mL of Glycerin Sample A and 1.0mL of Internal Standard Solution into a 10mL volumetric flask, dilute with methanol to volume and mix to give a concentration of 50mg/mL.

b. Test Solution B - Transfer 1.0mL of Glycerin Sample B and 1.0mL of Internal Standard Solution into a 10mL volumetric flask, dilute with methanol to volume and mix to give a concentration of 50mg/mL.

3. Perform the gas chromatography according to the USP Glycerin Monograph - Limit of Diethylene Glycol and Ethylene Glycol (see Revision Bulletin Official May 1, 2009), or the company's SOP for gas chromatographic analysis of Glycerin impurity analysis.

4. Calculate and Report the percentage of Diethylene glycol and Ethylene glycol in Glycerin Sample A and Glycerin Sample B as a percentage of Glycerin.

5. Identify which Glycerin Sample passes according to the Glycerin Monograph (NMT 0.1% Diethylene glycol or Ethylene glycol).

Percentage of Diethylene glycol in Glycerin Sample A (Data = Numeric)
Percentage of Ethylene glycol in Glycerin SAmple A (Data = Numeric)

Percentage of Diethylene glycol in Glycerin Sample B (Data = Numeric)
Percentage of Ethylene glycol in Glycerin SAmple B (Data = Numeric)

Identify which Glycerin Sample is passing according to the Glycerin Monograph for Diethylene glycol and Ethylene glycol impurities. (Data = A or B)

Impurity Ranges = Non-detectable to 0.75%

Data reported to 2 significant digits.

x = Conc. of DEG (or EG) in Std. Sol. (mg/mL)
y = Conc. of Glycerin Sample Glycerin (mg/mL)
z = Area of DEG (or EG) in  Glycerin Sample (from chromatogram)
a = Area of Internal Standard in Glycerin Sample (from chromatogram)
b = Area of DEG (or EG) in Glycerin Sample (from chromatogram)
c = Area of Internal Standard in Std. Sol. (from chromatogram)

% = {x/y} * { (z/a) / (b/c) } *100