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Unrealistic journal requirement for chemical purity of samples

7 July 2022

Researchers at the Cardiff Catalysis Institute collaborated with three international research groups on a study that showed an unrealistic journal requirement for chemical purity of samples.

Journals in chemistry set purity requirements that newly synthesised chemical compounds must adhere to before being accepted for publication. One of these is elemental analysis; a technique that can determine exactly how much of an element is present in a sample through combustion. This is commonly measured for mass fractions of carbon, hydrogen and nitrogen, and gives a ratio (in %) of elements in the sample. Journals typically ask for ±0.4% of each value, which requires 99.6% purity for samples.

When buying starting chemicals for a reaction, chemical suppliers often list reagents as ‘high purity’ or >99% purity and these cannot be further purified. The research team hence believe that at maximum, the standards for purity of synthesised samples should not be greater than the reagents they are derived from.

Laboratories generally send milligrams of a sample to external parties for elemental analysis and receive processed data back. Hence, common sources of error are completely out of the investigating laboratories’ hands. Several articles have raised questions about the integrity of elemental analysis data in chemical literature and whether the journal guidelines are realistic.

To investigate this, the researchers at Cardiff University (UK), La Trobe University (Australia), Dalhousie University (Canada), and Baylor University (USA) studied elemental analysis results for a set of 5 commercial and pure samples at 18 industrial services and academic institutions, spanning 4 continents. This is the first time a rigorous, international and statistically relevant study has been done on elemental analysis.

At Cardiff the research was undertaken by Prof. Rebecca Melen and PhD student Yara van Ingen from the Cardiff Catalysis Institute.

The results showed that more than 10% of the results deviated from the journal guidelines (±0.4%) and these variations were likely from random errors. This means that up to 10% of chemicals in a study may actually be pure but give unsatisfactory elemental analysis results and not be accepted for publication. This shows that the requirements set by academic journals for purity are not statistically realistic for synthetic samples.

The full article is available at ACS Central Science.

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