Determination of Cineole and Menthol by GLC (GC)

This method is applicable for the determination of cineole and menthol in production concentrates, finished goods (including aerosols), and raw materials. And determinations may be conducted individually or on both analytes simultaneously. ASSAY of CINEOLE and MENTHOL by GC.

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Principle

The cineole and menthol are extracted into a solvent and analyzed by GC using benzyl acetate as an internal standard.

Safety: Observe proper laboratory safety rules, personal protection, and chemical handling procedures at all times.

Read MSDS before handling chemicals or products.

Be aware of safety precautions when handling aerosol cans.

Apparatus

Hewlett Packard 5890 Series II Capillary Gas Chromatograph with FID detector and autosampler, or equivalent.

Appropriate software for data analysis (e.g. Chem station)

Volumetric glassware and pipettes

Analytical balance

Ultrasonic bath

Reagents/Chemicals :

Acetone - AR grade

Standards of known purity

Benzyl acetate - AR grade

Instrument Conditions :

Column : HP5 (30m x 0.32mm x 0.25u) or equivalent.

Carrier Gas : Helium

Head Pressure : 150 kpa

Make - Up Gas : Nitrogen - 30 mL/min

Split ratio : 50 : 1

Oven Temperature: 90°C

Oven Maximum: 300°C

Initial Time: 6 min

Injector Temperature: 250°C

Detector (FID) Temperature: 260°C

Injection Volume: 1 uL

Note: These are the proposed conditions and are to be used as a starting point. Column brand and age may affect the chromatography of the analytes. In order to obtain adequate results, the chromatographic conditions may need to be adjusted. An experienced chromatographer will be able to do this without significantly deviating from this procedure. Any changes made to the method should be recorded in the results.

Procedure

Standards

Internal Standard Solution (ISD) 0.26% w/v benzyl acetate in acetone. Use 2.0ml per 25ml flask. Standard Weigh 0.01 - 0.03g of each standard into a 25ml volumetric flask.

Add 2.0 ml ISD and makeup to volume with acetone. Mix well and ensure compounds are dissolved completely. Approximate Retention Times

Cineole: 2.4 mins

ISD - benzyl acetate: 4.6 mins

Menthol: 4.8 mins

Samples

1. Production Concentrates

Weigh about 0.8g sample into a 25ml volumetric flask and make up to volume with acetone. Take 2mL of the above solution into another 25mL volumetric flask. Add 2.0 ml of internal standard solution, make up to volume with acetone and mix well. Filter if necessary.

2. Finished Products

For aerosol cans follow the sampling procedure (TEX 31451) to obtain a sample of the finished product. Weigh 2.0-3.0g sample into a 25ml volumetric flask and make up to volume with acetone. Take 2mL of the above solution into another 25mL volumetric flask. Add 2.0ml of internal standard solution, make up to volume with acetone and mix well. Filter if necessary.

3. Raw Materials

Prepare the raw material samples in duplicate and compare them with duplicate preparations of the standard. 

Weigh 0.01-0.03g of the raw material into a 25ml volumetric flask. 

Add 2.0 ml of internal standard solution and make up to volume with acetone and mix well. 

ASSAY of CINEOLE and MENTHOL by GC.

Calculations

% w/w = Sample ratio x Standard Concentration (% w/v) x Sample volume (mL)

                                  Standard ratio x Sample weight (g)

where

 Sample ratio = Sample peak area / ISD peak area

Standard ratio = Standard peak area / ISD peak area

Results : Express results as % w/w.

>Operation and Calibration of GC with FID & ECD