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

This research looks at using isotope ratio mass spectrometry to identify the doping practice of administering sodium bicarbonate to horses before races to boost their performance. The isotopic analysis works by isolating and analysing the bicarbonate/CO2 in the horse’s urine and by doing this technique on 60 horse urine samples, the researchers found a variation of over 10‰ in the C13/C12 ratios.

Enhanced Buffer Capacity

• The aim of the study was to identify instances where sodium bicarbonate has been administered to competition horses to enhance their buffer capacity. Buffer capacity, in this context, refers to the horse’s ability to neutralise the lactic acid produced in their muscles during vigorous exercise, thus delaying fatigue and enhancing performance.
• This is considered doping and is therefore a prohibited practice in horse racing and other equestrian sports.

Isotopic Analysis

• To identify exogenous (externally administered) bicarbonate sources, the researchers carried out an isotopic analysis of the horse’s urinary bicarbonate/CO2 (also termed as TCO2).
• The reason they chose this approach is that technical sodium bicarbonate, the type most likely to be used in doping, exhibits high delta(13)C values compared to the total carbon in urine.

Total Carbon Analysis

• This study used 60 equine urine samples for the isolation of TCO2, followed by isotopic analysis. This analysis showed a significant variability in delta(13)C for TCO2, with a range of more than 10 per thousand.
• These variations in delta(13)C of total carbon and TCO2 seem to reflect varying proportions of C3 and C4 plant material in the horses’ diet.

Storage Time

• In the process of analysing mixtures of technical NaHCO3 and equine urine, the researchers found that TCO2 can be easily isolated without significant isotopic fractionation.
• However, they found that the storage time of urine samples was a significant variable, as it could lead to a shift of delta(13)C of TCO2 towards lower values. This implies that delaying analysis could potentially lead to false negatives in doping tests.