Development of Isotopic Reference Materials for <sup>13</sup>C-Urea Breath Tests

Abstract

Over 30 standards and certified measurement techniques are currently used in Russia to determine carbon, oxygen, and hydrogen isotope ratios. The techniques implemented in these documents are based on foreign reference materials (RMs). Similar domestically-produced RMs are not available, which makes the use of these techniques limited in the near future. This study aims to develop a certified RM (CRM) for the isotopic composition of carbon dioxide for 13C-urea breath tests. The following objectives were formulated: to develop a technique for obtaining RMs; to manufacture an RM pilot batch; to carry out type approval tests. The RM was manufactured by gravimetric mixing of carbon dioxide of two different isotopic composition from different sources with synthetic air. The mixing ratio was calculated using a specially developed technique. The RM stability was tested by an accelerated aging procedure. Following type approval tests, the developed CRM was included in the Federal Information Fund for Ensuring the Uniformity of Measurements under the registration number GSO 11999–2022. The practical significance of the obtained results is related to the possibility of using the developed CRM for improving the accuracy and validity of 13C-urea breath tests. Compared to the analogs, the developed CRM demonstrates a higher chemical purity.