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Chemical Reference Materials

“A reference standard is a highly purified compound that is well characterized.”

This statement first appeared in the US Food and Drug Administration document “Reviewer Guidance Validation of Chromatographic Methods” shortly after the Dietary Supplement Health and Education Act passed in October of 1994.  The statement still holds true today and is again repeated with publishing of the dietary supplement cGMPs in June of 2007.  Well characterized Reference Standards are critical in product development and method validation.  Reference Standards are useful for:

• Method validation
• Retention time marker
• System suitability
• Impurity profile
• Quantitative standard
• Product development
• Laboratory control standard
• Qualitative standard
• Safety testing

The data required for a Reference Standard is dependent on the use of the product.  A Reference Standard for quantitative procedures would require a higher level of data than one for retention time verification.  Through a series of qualitative and/or quantitative procedures, specifications of Reference Standards are generated from the available data according to the guidelines for each individual product line.  A Certificate of Analysis containing the data is generated detailing all the necessary testing procedures and documentation for a specific Reference Standard. ChromaDex™ Chemical Reference Standards are categorized into seven levels of product identity.  

For an example of a Certificate of Analysis, click on one of the links below:

• Primary (P)
• Secondary (SH)
• Secondary ( SG)
• Secondary (ST)
• Reagent Grade (RG)
• Food Grade (FG)
• American Herbal Pharmacopoeia (AHP) Verified
• United States Pharmacopoeia (USP)

Primary (P)
As the highest grade Reference Standards, the purity of Primary standards is well characterized and documented.  All ChromaDexTM Primary standards come with a complete Certificate of Analysis detailing adjusted total purity as calculated by HPLC/GC, Karl Fischer (water content), and GC (residual solvent), including Mass Spectrometry and NMR spectrum for verification of structure.  Primary Reference Standards are useful for:

• Accurate quantitative validation
• Method validation
• Quality control
• Analyte identification
• Characterization of "in-house" or "working" standards
• Equipment and instrument calibration
• Proficiency testing
• Analytical method development

Secondary (SH, SG, ST)
A step below Primary is ChromaDex's Secondary standards list in which the purity is approximately determined by HPLC, GC, or TLC only.  They do not come with the rigorous testing and characterization as provided with the Primary standards.  Secondary standards are cost effective analytical tools, however their lack of full documentation restricts their use to select analytical functions including:

• Basic starting method development
• Stability studies (pure compound stability)
• In vitro or in vivo studies
• Identity testing by TLC
• For characterization as an "in-house" or "working" standard

Reagent Grade (RG)
Reagent Grade chemicals are not analytical standards due to the lack of documentation and characterization needed for quantitative calculations.  The Certificate of Analysis for Reagent grade chemicals SHOULD NOT be used for quantitative purposes as no guaranteed method of analysis is provided.  These compounds may also be suitable for other general applications requiring high-purity materials, but may not always provide consistent or homogenous results.  Reagent grade chemical are useful for:

• Basic research and method development
• As an "in-house" or "working standard only after characterization by a Primary grade standard

Food Grade (FG)
Food Grade chemicals are similar to Secondary standards listing the approximate purity determined by either HPLC, GC, or TLC.  The physical characteristics are described (appearance, odor, taste, and loss on drying) as well as microbiological results (total plate count, yeast, mold, salmonella, and E. coli).  Food Grade standards are cost effective analytical tools, however their lack of full documentation restricts their use to select analytical functions including:

• Basic starting method development
• Stability studies (pure compound stability)
• In vitro or in vivo studies
• Identity testing by TLC
• For characterization as an "in-house" or "working" standard

American Herbal Pharmacopoeia (AHP) Verified
AHP grade standards are Primary grade standards in which the Certificate of Analysis (CofA) information on identity and purity that have been independently verified by a second laboratory according to AHP standards.  AHP Verified reference standards are useful for:

• Accurate quantitative validation
• Method validation
• Quality control
• Analyte identification
• Characterization of "in-house" or "working" standards
• Equipment and instrument calibration
• Proficiency testing
• Analytical method development

United States Pharmacopoeia (USP)