Quality Assurance

Quality Assurance

Missing the Mark: Raw Materials Rejected Due To Solvent Issues or Contamination

Rick Liva, ND, RPh


As always, the doctors at the CT Center for Health advocate for dietary supplement companies to be comprehensive and diligent in their raw material testing as the primary tool to ensure identity, potency, and minimal-to-no contamination. By testing comprehensively, companies can assurance end users that the products they sell have met a high standard of quality. In the last few months, I rejected 3 herbal raw materials and 1 probiotic raw material due to quality assurance issues. I briefly highlight them here because I think it is important to periodically remind you that the market is not a level playing field when it comes to quality in raw materials or finished products that get consumed every day. 


Before beginning, the following are some points to remember:


Certificate of Analysis: All raw materials come with a certificate of analysis (COA) denoting the specifications and quality parameters of the material bought. It is imperative that dietary supplement companies verify the COA quality parameters themselves by testing to verify identity, potency, and contamination. In the following examples, although the individual COAs had no mention of any problems and 3 were rejected due to residual solvent issues and the 4th, a probiotic, was rejected because of serious bacterial contamination.


Solvent Residue Testing: It is important to note that solvent residue testing it is not mandated as part of the US Food and Drug Administration (FDA) guidelines for Good Manufacturing Practices (GMPs) in regard to dietary supplements. It is up to the dietary supplement manufacturer themselves to determine if solvent residue testing is needed. In my opinion, this is a big hole in the FDA GMPs.  Hence, unacceptable residual solvent levels will be an ongoing quality challenge for many dietary supplement manufacturers.


Raw Materials Rejected Due To Solvent Issues


Boswellia Extract 65%

A batch of boswellia (Boswellia serrata) extract 65% was rejected because it contained a little more than 3 ppm (parts per million) of benzene, a toxic, carcinogenic chemical labeled as a Class 1 solvent (ie, a category that the US Pharmacopeia [USP] has labeled as “solvents to be avoided [because they are] known human carcinogens, strongly suspected human carcinogens, and/or environmental hazards;”). The USP allows a limit of 2 ppm for benzene, and, at that, only if there is no other way to make the product (ie, if les toxic distraction methods are available–which for boswellia there are. 


Ideally, no one should consume a product containing Class I solvents even if it has less than what the USP allows. Products such as benzene belong in chemistry labs, not in things we consume. However, the supplier of the raw material had no qualms selling it to me, a manufacturer of dietary supplements. In fact, this extract was purchased from a suppler that has a reputation for high-quality raw materials.


Curcumin Extract 95%

I returned a batch of curcumin (Curcuma longa) extract 95% because it contained 260 ppm of ethylene dichloride (EDC), another USP Class I toxic solvent. The USP allows a limit of 5 ppm–so this was over the limit by 5200%!  The supplier claimed it did not contain any EDC when they sent the material; however, upon further questioning, it became evident that they never tested the material to verify the claims of their grower. Curcumin extract is a popular and clinically useful material that is found in many products. At these levels, it could do much more harm than good.


These raw material products with unacceptably high levels of solvent residue are a result of the original manufacturer not taking the time to sufficiently dry the material to either blow off all of the solvent or reduce it to minimal levels.


In addition, it is usually not necessary to employ toxic solvents, especially–as designated by USP–not class I solvents. There are alternative that are much more acceptable.


Licorice Extract 12%

A batch of licorice (Glycyrrhiza glabra) extract 12% was rejected because it contained 36,400 ppm of ethanol. The USP allows a limit of 5000 ppm. Although ethanol is generally non-toxic at low levels, at 36,400 ppm (more than 7 times the legal limit) it may be enough to adversely affect some users and sensitive individuals. This extract was purchased from a European supplier that also has a reputation for high-quality raw materials.


Lactobacillus Sporogenes Rejected Due To Contamination

A batch of the probiotic (good bacteria) Lactobacillus Sporogenes was rejected and sent back to the supplier because it was contaminated with 3 unacceptable bacteria. DNA gene-sequence testing performed at an independent lab revealed the probiotic contained the following bacterial contaminants;


Clostridium bifermentans: A species common in feces, sewage, and soil.


Propionibacterium acnes: A largely commensal bacteria that is part of the skin flora present on most people; it lives on fatty acids in the sebaceous glands and may also be found throughout the gastrointestinal tract in humans and many other animals. It has been associated with a wealth of human pathologies.


Enterocuccus durans: Enterococci are normal flora of the gastrointestinal tract of humans and animals. They also may be found in oral secretions, the upper respiratory tract, skin, and the vagina. Human infections can occur due to Enterococcus durans, Enterococcus raffinosus, Enterococcus casseliflavus, or Enterococcus avium.


When sold as raw materials, probiotic bacterial organisms should be singular organisms and not be contaminated with any other type of bacteria or fungi. I have tested and used this probiotic product for years and this is the first time I ever found contamination–highlighting the importance of testing each and every lot/batch, as one never knows when an outlier poor quality batch will be found.


This probiotic was purchased from a suppler that has a reputation for high-quality raw materials.


There are 2 essential questions we have to think about and consider:

1) How many dietary supplement manufacturers bought the materials I highlighted above and did not adequately test for contamination and hence used them to make finished products?


2) I wonder what the above suppliers did with the materials I rejected: Sold it to another company? Destroyed it?


If suppliers just returned the material to be sold again, then whose shelf are they sitting on just waiting to be consumed tomorrow and the next day and the next?


ConsumerLab Valerian Testing

ConsumerLab.com reported in November that most of the valerian herbal supplements recently selected for testing contained less of the herb than expected and/or were contaminated with lead.


Among 9 products selected by ConsumerLab.com for review, only 2 passed testing. Of the 7 that failed, 1 contained no detectable key valerian compounds and 2 others had only 26.7% to 82.5% of amounts expected from ingredient listings. One of these products was found to be contaminated with lead, as were 2 other products for a total of 3. These results were confirmed in independent laboratories.


Lead contamination was found to be an issue in products consisting primarily of valerian root powder as opposed to valerian root extract. The extraction process removes heavy metals.


Comment on Valerian Testing:  The Valerian products that tested at 26.7% and 82.5% of label claim are professional products companies.  Hmmmm, what quality assurance testing didn’t happen to allow subpotent product to get into the market?  ConsumerLab is the only company out there testing products in the marketplace.  What they do and the limits they apply are controversial at times. 


Clinicians use natural products to help their patients improve health, restore balance and reduce or eliminate disease symptoms.  Many of us assume those products meet label claim and have no harmful contamination.  It is imperative that dietary supplement manufacturers perform consistent comprehensive testing of raw materials and finished product to ensure potency and lack of or minimal contamination.  We can only hope that some day that becomes the standard and the norm that ALL manufacturers adhere to. 


Rick Liva, ND, RPh, graduated from Temple University School of Pharmacy in 1975 and National College of Naturopathic Medicine in 1982. He is the managing physician at the Connecticut Center for Health, located in Middletown and West Hartford. Dr Liva is a founding member of the American Association of Naturopathic Physicians and past president of the Connecticut Society of Naturopathic Physicians. As mentioned in the disclosure, he is also the president, CEO, and director of Quality Control and Quality Assurance at Vital Nutrients, a company certified by the Natural Products Association for current Good Manufacturing Practices.


A Solvent Primer

The issue of solvents is complex and involved. Official US policy began in 1997 when a joint initiative involving both regulators and research-based industry members from numerous countries published the International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals For Human Use, ICH Harmonised Tripartite Guideline, Impurities: Guideline for Residual Solvents. This was then adopted by the US Food and Drug Administration. Based on these guidelines, the US Pharmacopeia (USP) revised Chapter 467, “Residual Solvents,” of its National Formulary in 2007. This then became official policy on July 1, 2008. Basically, there are 4 classes of solvents. Following is  a simple primer based on the more current USP revision.


Class I Solvents

These solvents should not be employed in the manufacture of drug substances, excipients, and drug products (and, hence, natural medicines either) because of their unacceptable toxicity or their deleterious environmental effects. However, to produce a drug product (or natural medicine), if their use is unavoidable, then their levels should be restricted as shown in Table 1.


Table 1. Class I Solvents (Solvents That Should Be Avoided)


Acceptable Limit  in ppm*


1,1,1 Trichloroethane


Environmental hazard

1,1 Dichloroethene



1,2 Dichloroethane






Carbon tetrachloride


Toxic and environmental hazard

*parts per million (ppm)


Class II Solvents

These solvents should be limited in use because of their inherent toxicity. There are 27 in this category, with acceptable limits from 50 ppm to 4840 ppm. Some examples are chloroform, cyclohexane, hexane, methanol, and toluene.


Class III Solvents

These solvents are regarded as less toxic and of lower risk to human health. There are also 27 in this category, all with limits of 5000 ppm. Some examples are acetone, dimethyl sulfoxide, ethanol, ethyl acetate, and methyl acetate.


Class IV Solvents

May be of interest but no toxicity data were found.


Solvents Good to Routinely Test

Since my company began solvent testing before the 2008 USP revision, we base our testing protocol on the 1997 (now revised to 2002) ICH Harmonised Tripartite Guideline, mentioned above. Thus, the 22 solvents we routinely test for vary slightly from the Class I to III USP listing also given above. Our testing list includes the following:


Class I

(4): 1,1,1-trichloroethane, 1,1,2-trichloroethane, 1,2-dichloroethane (methylchloroform), benzene


Class II

(7): chloroform, cyclohexane, dichloromethane, hexane, methanol, toluene, xylenes (dimethylbenzene)


Class III

(11): 1-butanol, 2-butanone, acetic acid N-butyl ester, acetone, diethyl ether, ethanol, ethyl acetate, heptane, isopropyl alcohol, methyl tertiary butyl ether (tert-butylmethyl ether), N-butyl ester.