Ethylene Oxide (ETO) and its Byproducts
When one considers the fact that many spices are variously scraped off trees, piled on the ground and pulled off low bushes, it should come as no surprise that their microbial quality is suspect. Consequently there has long been interest in ways to sterilize spices.
One approach, in use for a considerable length of time, is the gassing of spices with ethylene oxide (ETO). As an epoxide ETO is fairly reactive. Inevitably there are other reactions involving the epoxide ring, producing a variety of byproducts. Principal among these byproducts is ethylene chlorohydrin (ECH) and ethylene glycol, both of which are more stable then ETO.
Since ETO is fairly volatile and dissipates fairly quickly, the only evidence of exposure to ETO may be the ECH residue. Analytical methods have been designed for this purpose.
The choice of an analytical procedure for ETO and/or its byproducts depends on the purpose for which the results will be used. Clear judgements must be made in advance of testing so as to ensure that the results will be appropriate for their intended use. If the purpose is to determine if the product has ever been exposed to ethylene oxide or contains any component that has been gassed with ethylene oxide, the approach is to look for ECH. The method of choice is based on a paper by Jensen This very elegant method is optimized for detection of traces and is only modestly good for precise quantification. We believe the method is useful up to about 2500 ppb, i.e. 2.5ppm.
For products that actually have been gassed with ethylene oxide, the ECH levels can be very high, sometimes in the thousands of ppm. Testing for these products is usually done to show compliance with the Canadian regulatory specification of 1500 ppm. This method has a lower limit of quantitation in the neighborhood of 50-100 ppm. The method of choice for this purpose is ASTA (American Spice Trade Association) method 23.3.
An unfortunate fact is that between the levels of 2.5ppm and 50ppm of ECH we have a gray area where neither method is suitable. At Certified Laboratories we have addressed this area by modifying the Jensen method by using smaller sample sizes, thus extending the reach of the method upwards. An inevitable concern, of course, is that as sample sizes get smaller, it becomes difficult to maintain confidence in the representativeness of the sample.
Good communication between the laboratory and the client of the analytical result is essential to ensure that such default choices do not compromise the usability of the analytical result.
To help in deciding which method is most applicable, refer to the table below:
Analyte Method Lowest Level of Detection Highest Level of  Detection Best Used For
ETO Jensen 10 ppb Appx 1 ppm Compliance with EU/German Requirements
ETO ASTA 23.1 10-20 ppm No Limit Verification of Compliance with US Law
ETO ASTA 23.2 1-5 ppm 1000 Verification of Compliance with US Law
ECH Jensen Appx 20 ppb Appx 2.5 ppm Compliance with EU/German Requirements
ECH ASTA 23.3 Appx 50-100 ppm >2000 ppm Verification of Compliance with Canadian Rules
ECH

Internal variation of Jensen Method

 100-200 ppb Appx 50 ppm Intermediate Levels of ECH
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