Tag Archives: GC-MS

From The Lab

QuEChERS 101

By Danielle Mackowsky
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Sample preparation experts and analytical chemists are quick to suggest QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) to cannabis laboratories that are analyzing both flower and edible material for pesticides, mycotoxins and cannabinoid content. Besides having a quirky name, just what makes QuEChERS a good extraction technique for the complicated matrices of cannabis products? By understanding the chemistry behind the extraction and the methodology’s history, cannabis laboratories can better implement the technology and educate their workforce.

QuEChERS salt blends can be packed into mylar pouches for use with any type of centrifuge tubes
QuEChERS salt blends can be packed into mylar pouches for use with any type of centrifuge tubes

In 2003, a time when only eight states had legalized the use of medical cannabis, a group of four researchers published an article in the Journal of AOAC International that made quite the impact in the residue monitoring industry. Titled Fast and Easy Multiresidue Method Employing Acetonitrile Extraction/Partitioning and “Dispersive Solid-Phase Extraction” for the Determination of Pesticide Residues in Produce, Drs. Michael Anastassiades, Steven Lehotay, Darinka Štajnbaher and Frank Schenck demonstrate how hundreds of pesticides could be extracted from a variety of produce samples through the use of two sequential steps: an initial phase partitioning followed by an additional matrix clean up. In the paper’s conclusion, the term QuEChERS was officially coined. In the fourteen years that have followed, this article has been cited over 2800 times. Subsequent research publications have demonstrated its use in matrices beyond food products such as biological fluids, soil and dietary supplements for a plethora of analytes including phthalates, pharmaceutical compounds and most recently cannabis.

QuEChERS salts can come prepacked into centrifuge tubes
QuEChERS salts can come prepacked into centrifuge tubes

The original QuEChERS extraction method utilized a salt blend of 4 g of magnesium sulfate and 1 g of sodium chloride. A starting sample volume of 10 g and 10 mL of acetonitrile (ACN) were combined with the above-mentioned salt blend in a centrifuge tube. The second step, dispersive solid phase extraction (dSPE) cleanup, included 150 mg of magnesium sulfate and 25 mg of primary secondary amine (PSA). Subsequent extraction techniques, now known as AOAC and European QuEChERS, suggested the use of buffered salts in order to protect any base sensitive analytes that may be critical to one’s analysis. Though the pH of the extraction solvent may differ, all three methods agree that ACN should be used as the starting organic phase. ACN is capable of extracting the broadest range of analytes and is compatible with both LC-MS/MS and GC-MS systems. While ethyl acetate has also been suggested as a starting solvent, it is incompatible with LC-MS/MS and extracts a larger amount of undesirable matrix components in the final aliquot.

All laboratories, including cannabis and food safety settings, are constantly looking for ways to decrease their overhead costs, batch out the most samples possible per day, and keep their employees trained and safe. It is not a stretch to say that QuEChERS revolutionized the analytical industry and made the above goals tangible achievements. In the original publication, Anastassiades et al. established that recoveries of over 85% for pesticides residues were possible at a cost as low as $1 per ten grams of sample. Within forty minutes, up to twelve samples were fully extracted and ready to be analyzed by GC-MS, without the purchase of any specialized equipment. Most importantly, no halogenated solvents were necessary, making this an environmentally conscious concept. Due to the nature of the cannabis industry, laboratories in this field are able to decrease overall solvent usage by a greater amount than what was demonstrated in 2003. The recommended starting sample for cannabis laboratories is only one gram of flower, or a tenth of the starting volume that is commonly utilized in the food safety industry. This reduction in sample volume then leads to a reduction in acetonitrile usage and thus QuEChERS is a very green extraction methodology.

The complexity of the cannabis matrix can cause great extraction difficulties if proper techniques are not used
The complexity of the cannabis matrix can cause great extraction difficulties if proper techniques are not used

As with any analytical method, QuEChERS is not perfect or ideal for every laboratory setting. Challenges remain in the cannabis industry where the polarity of individual pesticides monitored in some states precludes them from being amenable to the QuEChERS approach. For cannabis laboratories looking to improve their pesticide recoveries, decrease their solvent usage and not invest their resources into additional bench top equipment, QuEChERS is an excellent technique to adopt. The commercialization of salt blends specific for cannabis flowers and edibles takes the guesswork out of which products to use. The growth of cannabis technical groups within established analytical organizations has allowed for better communication among scientists when it comes to best practices for this complicated matrix. Overall, it is definitely worth implementing the QuEChERS technique in one’s cannabis laboratory in order to streamline productivity without sacrificing your results.

The Practical Chemist

Building the Foundation of Medical Cannabis Testing – Understanding the Use of Standards and Reference Materials – Part 2

By Joe Konschnik
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In the last article I referred to the analogy of the analytical reference material being a keystone of the laboratory foundation, the stone upon which all data relies. I then described the types of reference materials and their use in analytical testing in general terms. This article will describe the steps required to properly manufacture and deliver a certified reference material (CRM) along with the necessary documentation.

A CRM is an exclusive reference material that meets strict criteria defined by ISO Guide 34 and ISO/IEC 17025.  ISO is the International Organization for Standardization and IEC is the International Electrotechnical Commission. These organizations work together to set globally recognized standards. In order for a reference material to be labeled as a CRM it must 1) be made with raw or starting materials which are characterized using qualified methods and instruments, 2) be produced in an ISO-accredited lab under documented procedures, and 3) fall under the manufacturer’s scopes of accreditation. Verifying a CRM supplier has these credentials is easily done by viewing their certificates which should include their scopes of accreditation. Restek_accredit

There are many steps required to produce a CRM that meets the above three criteria.  The first step requires a review of the customer’s, or end-user’s requirements to carefully define what is to be tested, at what levels and which analytical workflow will be used.  Such information enables the producer to identify the proper compounds and solvents required to properly formulate the requested CRM.

The next step requires sourcing and acquiring the raw, or starting materials, then verifying their compatibility and stability using stability and shipping studies in accordance with ISO requirements. Next the chemical identify and purity of the raw materials must be characterized using one or more analytical techniques such as: GC-FID, HPLC, GC-ECD, GC-MS, LC-MS, refractive index and melting point. In some cases, the percent purity is changed by the producer when their testing verifies it’s different from the supplier label. All steps are of course documented.

restek_CRMThe producer’s analytical balances must be verified using NIST traceable weights and calibrated annually by an accredited third party provider to guarantee accurate measurement. CRMs must be prepared using Class A volumetric glassware, and all ampules and vials used in preparation and final packaging must be chemically treated to prevent compound degradation during storage. Next, CRMs are packaged in an appropriate container, labeled then properly stored to maintain the quality and stability until it’s ready to be shipped. All labels must include critical storage, safety and shelf life information to meet federal requirements. The label information must be properly linked to documentation commonly referred to as a certificate of analysis (COA) which describes all of the above steps and verifies the traceability and uncertainty of all measurements for each compound contained in the CRM. Restek_CRM2

My company, RESTEK, offers a variety of documentation choices to accompany each CRM. Depending on the intended use and data quality objectives specified by the end-user, which were defined way back at the first step, three options are typically offered:  They include gravimetric only, qualitative which includes gravimetric, and fully quantitative which includes all three levels of documentation. The graphic to the right summarizes the three options and what they include. 

It’s important to understand which level you’re purchasing especially when ordering a custom CRM from a supplier. Most stock CRMs include all three levels of documentation, but it’s important to be sure.

Understanding what must be done to produce and deliver a CRM sets it apart from other reference material types, however it’s important to understand there are some instances where CRMs are either not available, nor required and in those situations other types of reference materials are perfectly acceptable.

If you have any questions or would like more details about reference materials please contact me, Joe Konschnik at (800) 356-1688 ext. 2002 by phone, or email me at joe.konschnik@restek.com.