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analytical lab news1 News #1: Chondroitin
analytical lab news2 News #2: Glucosamine
analytical lab news3 News #3: L-Carnitine
analytical lab news4 News #4: Chondroitin & Glucosamine in Pet Food
analytical lab new5 News #5: Single Lab Validation
analytical lab news6 News #6: Identification and Quantification of Oversulfated Chondroitins
Member of AOAC method Committee for Dietary Supplement
Active participant in Dietary Supplement Task Force
Official contractor for NIH through BPA program (Blanket Purchase Agreement)
Completed Single Lab Validation of Enzymatic-HPLC Method for Chondroitin Sulfate Assay funded by NIH, and the paper is going to be published on Journal of AOAC
Developed Pre-Column Derivatization Method for Glucosamine Assay funded by NIH, and the paper have been published on Journal of AOAC
An Ion-Exchange HPLC Method For Assay L-Carnitine In Complex Nutriceutical Formulation With Complete Separation From It's Degradant

L-carnitine is a high polarity compound, and lack of retention by reversed-phase HPLC. Ion pair methods can increase the retention time of L-carnitine, but still not enough. In complex nutriceutical formulation the L-carnitine peak is easily to be interfered by some other ingredients.Currently we developed an Ion-Exchange HPLC method which xhibits a much longer retention for L-carnitine. The k' is about 6~10, dependant on pH an ionic strength of the mobile phase.

L- carnitine, as its structure shows, has low UV absorption. Its natural degradant Crotonoylbetain on the other hand has two conjugated double-bonds, which gives it about 200 times stronger UV absorption than the parent compound. Chemical structures of L-carnitine and crotonoylbetaine are shown below:


Theoretically, a 0.5% of crotonoylbetaine as impurity existing in the L-carnitine (99.0% purity) could double the measured amount of L-carnitine, if these two peaks are not fully separated from each other. An example of such method would be one that was published in the USP23.

We urge raw material suppliers and finished product manufacturers look into the current methodology used in the quality control testing of your L-carnitine. Complete separation of the two compounds is imperative for two reasons:

  • Trace amount of degradant, even at 0.01% content, would falsely increase the result on L-carnitine by 2% when they are not separated.

  • L-carnitine stored at room temperature for one year has shown substantial increase in crotonoylbetaine. Therefore, proper testing of L-carnitine could assure that already degraded material would not give a falsely "better" result than the fresh and good products.

  • We do not know the biological activity of the degradant, therefore it would be better to minimize its presence by testing the raw material properly.

Our Ion-exchange HPLC methods not only gives excellent separation within a reasonably long retention time, it also can be easily adjusted for the elution time by varying the pH and ionic strength of the mobile phase, when a complex formulation requires to do so.
The method LOD (Limit of Detection) = 0.00228mg/ml
LOQ (Limit of Quantitation) = 0.00762 mg/ml
Linearity spans a range of 104
Spike recovery ranged from 98.1% to 101.0%

Typical chromatogram: a raw material with degradant.

testing data diagram

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