A Simple, non‐Destructive Method for Bromide Analysis in Plasma for Field Body Composition Studies

Abstract

ObjectiveExpansion of extracellular water (ECW) space serves as a measure of muscle loss, cachexia or inflammation. It is used to monitor frailty, depletion of muscle mass, and the efficacy of nutritional interventions. ECW is measured by bromide dilution, where a known amount of NaBr is administered and a plasma (or urine) sample is analyzed, after equilibrium, by instrumental neutron activation analysis (INAA) or high‐performance liquid chromatography (HPLC). The objective of this work is to develop an alternative, automated method of analysis that does not require the complexity of INAA or HPLC.MethodWe tested a non‐destructive energy dispersive X‐ray fluorescent (XRF) device which uses a Cd‐109 radioactive source, a miniature (25 mm2), electronically cooled, high resolution (<150 eV) silicon detector and a microprocessor‐controlled sample‐positioning system to obtain X‐ray spectra from plasma samples. The method requires no sample preparation and preserves 100% of each specimen.ResultsSensitivity: 0.1ug/cc, reproducibility for Br in plasma or urine <0.8%, accuracy <1.0%. Validated against INAA (R2=0.994).ConclusionThe method can be used in the field for repeated measurements. The lack of sample preparation eliminates the opportunity for bromide loss due to filtering. Being non‐destructive, XRF allows for full preservation of the specimen. Support: USDA contr. 51000–071