Isolation of bicarbonate from equine urine for isotope ratio mass spectrometry†

Abstract

Sodium bicarbonate administration to horses prior to competition in order to enhance the buffer capacity of the organism is considered as a doping offence. The analysis of the isotopic composition of urinary bicarbonate/CO(2) (TCO(2)) may help to identify an exogenous bicarbonate source, as technical sodium bicarbonate exhibits elevated delta(13)C values compared with urinary total carbon. The isolation of TCO(2) from 60 equine urine samples as BaCO(3) followed by an isotopic analysis shows a significant variability of delta(13)C for TCO(2) of more than 10 per thousand. The delta(13)C of total carbon and TCO(2) seem to reflect different proportions of C3 and C4 plant material in the diet. The isotopic analysis of different mixtures of technical NaHCO(3) and equine urine shows that TCO(2) can be easily isolated without major isotopic fractionation; however, attention has to be paid to the storage time of urine samples, as a shift of delta(13)C of TCO(2) to lower values may occur.

Doping detection in animals: A review of analytical methodologies published from 1990 to 2019

“…A threshold of 36 mM of available carbon dioxide per liter in plasma has also been adopted by the IFHA, and the ISE method is considered the reference method for the measurement of TCO 2 18 . Other studies have presented alternative methods for the determination of TCO 2 in horse plasma, 306,307 and, most recently, a headspace GC‐MS method has been developed 308 …”

“…18 Other studies have presented alternative methods for the determination of TCO 2 in horse plasma, 306,307 and, most recently, a headspace GC-MS method has been developed. 308 Gonadotropin-releasing hormone induces the secretion of luteinizing hormone that stimulates males' testes to produce testosterone. Its misuse motivated the development and application of methods for its detection in horse urine 309 and horse plasma.…”