Readers of the blog have been presented with a wealth of information on for their GC columns, LC columns, detectors, syringes, carrier gases, TO-Canisters, and the list go on. What’s missing? Analytical Reference Standards.
Although not all reference standards have special handling instructions, the following general guidelines should assist you with the proper handling of these critical resources.
Storage temperatures can have a big impact upon your reference standard solutions. Volatile compounds (ex: vinyl chloride through naphthalene) are normally recommended to be stored frozen, since they can readily evaporate at room temperature. Make sure you store these solutions with minimal headspace in a well-sealed vial. On the other hand, solutions containing less volatile compounds (ex: PAHs and Cannabinoids), are typically recommended to be stored refrigerated. Others, such as Aroclor PCBs, are to be stored at room temperature. Since some of our certificates of analysis (CoA) list “less than 10°C” as the storage condition, I do have some advice for anyone that stores these less volatile compounds in their freezer. Once the solution warms to room temperature, place the solution in a sonicator for 10-15 minutes to allow these compounds to dissolve back into solution. By doing so, you will not be “missing” these compounds from your assay.
Some compounds are sensitive to light and can easily degrade when exposed to it. These photosensitive compounds, such as organophosphorus pesticides, can be protected by storing them in amber vials. For this purpose, Restek supplies a deactivated amber secondary vial with all of its solutions. A good practice is to always store your reference standards, including those at room temperature, away from light. Some additional precautions to avoid light exposure are to work under yellow light and to use red-tinted glassware when preparing dilutions. If you are working with known photosensitive compounds, use amber autosampler vials for your solutions. Minimize exposure to light and to return all standards to their storage area as soon as possible after use.
Finally, some compounds are incompatible with acids, bases, other compound classes or specific compounds. Because of the number and variety of potential reactions, I’m not going to go into specific details. I will note that Restek’s standard solutions are evaluated for solution feasibility to ensure compatibility between compounds. Since there are numerous multi-component methods, analysts do end up mixing solutions to create calibration standards. If you experience the loss of analytes or see new analytes in these cocktails, try analyzing your purchased solutions individually. There’s likely an interaction occurring between compound(s).
If you’re ever in doubt, don’t forget the CoA. The CoA contains storage recommendations and any warnings be it photosensitivity or chemical incompatibility. The manufacturer should have data to support their recommendations. The ability to search Restek’s CoA documentation is one click at:
Now, reference standards can have their 15 minutes of fame in ChromaBLOGraphy.