Understanding Certificates of Analysis (COAs)

A Certificate of Analysis (COA) is a laboratory document used to report analytical testing results for a sample. Understanding how these reports are generated and interpreted can help researchers evaluate analytical data, testing methods and laboratory documentation. This educational guide explains some of the terminology commonly found in Certificates of Analysis, including analytical purity, HPLC, mass spectrometry and batch-specific testing.

What is a Certificate of Analysis?

A Certificate of Analysis (COA) is a document that reports the results of laboratory testing performed on a particular sample or batch. Depending on the analytical methods used, a COA may include information about sample identity, analytical purity, quantity and other measured characteristics. COAs allow analytical results to be reviewed alongside information such as the testing method, sample identification and laboratory reference details.

Why Independent Laboratory Testing Matters

Independent laboratory testing provides analytical data from a laboratory that is separate from the supplier of the sample. This separation can provide an additional level of transparency when reviewing research materials. Laboratories may use analytical techniques such as High-Performance Liquid Chromatography (HPLC) and Mass Spectrometry (MS) to evaluate characteristics including purity and molecular identity. A laboratory report should also be linked to the specific sample or batch tested. This is why batch-specific Certificates of Analysis can be more informative than a generic testing statement.

How to Read a Certificate of Analysis

A Certificate of Analysis contains several pieces of analytical information. Understanding what each section represents can help researchers interpret laboratory results correctly. Sample or Batch Identification: Identifies the specific sample submitted to the laboratory and helps connect the analytical report to the material that was actually tested. Analytical Purity: Purity testing estimates the proportion of the detected material represented by the target compound under the analytical method used. HPLC is commonly used for this type of analysis. Mass Spectrometry: Mass spectrometry can provide information about molecular mass and can help support identification of the compound being analysed. Laboratory Reference or Report Number: A unique reference number can allow a laboratory report to be independently located or verified when the testing laboratory provides a verification system.

Purity vs Quantity — They Are Not the Same Thing

Analytical purity and quantity are two different measurements that may appear on a laboratory report. Understanding the distinction is important when interpreting a Certificate of Analysis. Purity describes the relative proportion of the target compound compared with other components detected by a particular analytical method. For example, HPLC may be used to evaluate chromatographic purity. Quantity refers to the measured amount of the target compound present in the tested sample. Depending on the laboratory and analytical method, this may be reported as mass or another quantitative measurement. A high purity percentage does not, by itself, establish the quantity of material in a sample. Likewise, knowing the quantity does not automatically establish its purity. For this reason, purity and quantity results should be interpreted separately and in the context of the analytical methods reported by the laboratory.

Purity vs Quantity — They Are Not the Same Thing

Analytical purity and quantity are two different measurements that may appear on a laboratory report. Understanding the distinction is important when interpreting a Certificate of Analysis. Purity describes the relative proportion of the target compound compared with other components detected by a particular analytical method. For example, HPLC may be used to evaluate chromatographic purity. Quantity refers to the measured amount of the target compound present in the tested sample. Depending on the laboratory and analytical method, this may be reported as mass or another quantitative measurement. A high purity percentage does not, by itself, establish the quantity of material in a sample. Likewise, knowing the quantity does not automatically establish its purity. For this reason, purity and quantity results should be interpreted separately and in the context of the analytical methods reported by the laboratory.

Understanding HPLC and Mass Spectrometry

Laboratories use different analytical techniques to examine different characteristics of a sample. Two methods commonly referenced on Certificates of Analysis are High-Performance Liquid Chromatography (HPLC) and Mass Spectrometry (MS). High-Performance Liquid Chromatography (HPLC) HPLC separates components within a sample. The resulting chromatogram displays detected components as peaks. The relative peak areas can be used to assess chromatographic purity under the conditions of the test. Mass Spectrometry (MS) Mass spectrometry measures the mass-to-charge ratio of ions generated from a sample. The resulting data can help support identification by comparing the observed molecular mass with the expected molecular mass of the compound. Why both can be useful HPLC and mass spectrometry provide different types of analytical information. A purity result alone does not necessarily confirm molecular identity, while an observed molecular mass alone does not establish overall purity. Together, these techniques can provide complementary information when evaluating analytical results.

What a COA Can — and Cannot — Tell You

A Certificate of Analysis provides analytical information about the specific sample tested by a laboratory. However, it is important to understand both the information a COA can provide and its limitations. What a COA can tell you: A COA may provide information about sample identification, analytical purity, measured quantity, molecular mass and the analytical methods used. The exact information depends on the tests performed by the laboratory. What a COA cannot tell you: A COA should not automatically be interpreted as evidence that a substance is safe, effective, approved for therapeutic use or suitable for human consumption. Analytical testing answers specific laboratory questions about the submitted sample. Why batch identification matters: Analytical results apply to the sample or batch that was actually tested. Checking identifying information and laboratory reference numbers helps establish which material the report relates to.

How to Verify a Laboratory Report

Laboratory reports may contain identifying information that allows the analytical results to be traced back to the testing laboratory and the specific sample submitted for analysis. Check the laboratory details Look for the name of the laboratory responsible for the analysis and any identifying information provided on the report. Check the report or reference number Many laboratories assign a unique reference number to each analytical report. This can help distinguish one test report from another. Check the sample information Review the sample name, batch information and other identifiers to confirm which submitted sample the analytical results relate to. Use independent verification when available Some laboratories provide an online verification system where a report or reference number can be checked directly against the laboratory’s records. Review the analytical methods Check which tests were actually performed. A report containing an HPLC result, for example, provides different information from a report containing mass spectrometry or quantitative analysis.

Important Context When Interpreting COAs

A Certificate of Analysis should be interpreted within the context of the analytical methods used and the specific sample or batch tested. Results such as purity, identity and quantity describe different analytical characteristics and should not be interpreted as interchangeable measurements. Laboratory results represent the sample submitted for analysis at the time of testing. When reviewing a COA, researchers should consider the testing method, laboratory reference number, sample identification and any limitations stated in the report.

This article summarises laboratory and published research for in-vitro research purposes only. Nothing here is advice about use in people or animals.