## 1 Introduction
Though no literature currently exists on the use of SPME Arrow to collect VOCs from biological matrices, it could provide significant benefits. Many forensic and medical studies that analyze biological samples are currently interested in profiling volatiles from different species of bacteria. In forensic science, this information can assist in the improvement of search and recovery procedures [29; 30; 31], since many microbes have now been closely associated with deceased individuals [32]. In medicine, the volatiles given off by microbes and human cell lines can be key indicators of health or disease status [33; 34; 35; 36]. When investigating sources of this nature, a number of challenges are present including the high diversity in the VOC profile, the dynamic range of concentrations of VOCs, the large number of samples that must be investigated based on project design, as well as the sensitive and critical nature of each individual sample [35; 37]. When dealing with volatile sampling, repeated sample injection may not be possible, and so the reliability and robustness of the sampling technique is extremely important. An increase in sensitivity based on higher VOC loading during the collection process will be a major advantage in dealing with the dynamic range experienced with such samples. As such, it is likely that SPME Arrow will become a more common sampling technique used in these fields over traditional SPME fibers, particularly for biological matrices. _B. subtilis_ (Bacillus: Bacillaceae) is a species of bacteria that is facultatively aerobic, Gram-positive, motile, and rod shaped (typically 0.7-0.8 \(\upmu\)m \(\times\) 2.0-3.0 \(\upmu\)m) [38]. _B. subtilis_ was selected for the current study because it is widely distributed throughout nature [39], associated with decomposing remains [40], and serves as the type species for the genus _Bacillus_[38]. This species can colonize diverse habitats because it has the ability to decompose a wide range of organic and inorganic resources including protein, amino acids, ammonium, and nitrate; all of these compounds are forensically-relevant as they are associated with decomposing remains and represent key steps in the nitrogen cycle [41]. Additionally, in medical contexts, _B. subtilis_ has been shown to be associated with cases of food poisoning due to spoiled meat, dermatitis, respiratory problems, tumor infection, bacteremia, and septicemia [42]. Improving our ability to profile temporal trends in volatile byproducts during the metabolic activity of _B. subtilis_ using a more sensitive and robust SPME Arrow technology has implications across all these areas. There currently exists minimal published data on the SPME Arrow technique to demonstrate optimal conditions for VOC analysis from biological matrices, as well as the dynamics of different VOCs that may be encountered during the sampling process. In particular, the limited studies that highlight SPME Arrow [18; 27; 28; 43] do not target compounds encountered in life sciences applications such as forensic science and biomedical disease detection. The objective of this work was to provide preliminary data on the headspace SPME collection of a range of common VOCs encountered in life sciences applications using this high capacity SPME Arrow technique. A volatile reference mixture (VRM) was created to be used in the assessment of the SPME Arrow collection parameters. Fiber type, exposure time, desorption time, carryover, and method reproducibility were investigated to better understand fiber dynamics. A comparison to traditional SPME fiber design was also performed. Finally, the optimized SPME Arrow collection parameters were applied to the VOC profiling of a microbiological source, the headspace of cultured _B. subtilis_, which is a common microbe associated with forensic, medical, and agricultural applications.