Evaluation of GC-Orbitrap for urine volatolome investigation

Volatilomics is a field of research that focuses on analyzing volatile organic compounds (VOCs) released by biological systems1. These VOCs present different classes with some properties such as boiling point less than 300 °C, and low molecular weight. After being produced by different metabolic processes they enter into the blood system to be released later through breath, urine, feces, and skin. Compared to other types of metabolites, which must be extracted from tissues before analysis, a part of VOCs is directly accessible in the gaseous phase (headspace) at room temperature (25 °C), thus requiring minimal sample preparation and allowing non-invasive and real-time monitoring. Among biofluids, urine is considered the most convenient as it is easily accessible and available through non-invasive sampling, and it can be stored for long periods. Additionally, urine samples provide a comprehensive metabolic profile with VOCs ranging in polarity and complexity. Nevertheless, volatilome investigation was based on untargeted compound strategy and so need to optimize the operating condition to detect a large variety of compounds and to limit the instrumentation variability. Optimization of the conditions for extracting VOCs analysis were performed to increase the number of VOCs extracted by HS-SPME from urine. A sesign of the experiment were built using Azurad software, and it allowed us to allow us to evaluate different parameters and their factors in a limited number of experiments and obtain the optimum parameters. The different parameters optimized were the amount of added salt (Salting-out effect), extraction time, the coating material of the fiber, and extraction temperature. Moreover, the impact on the variability of some operating conditions like tune frequency, resolution, source temperature were evaluated. Finally, different parameters of compound discoverer software were investigated on the accuracy of identification of a set of compounds.