Evaluation and optimization of sample transfer process for Bio-VOCTM breath sampler
Background,aim,and scope Examination of volatile organic compounds(VOCs)in human exhaled breath finds utility in both environmental exposure assessment and disease diagnosis.Alveolar gas,a constituent of human exhalation,serves as a reflection of both exogenous exposure and endogenous metabolism,while minimizing interference from external environmental gases and dead space gas in the oral and nasal cavities.The Bio-VOCTM breath sampler stands out as specialized commercial equipment designed for collecting alveolar gas.The gas sample collected by this sampler requires transfer to an adsorption tube for GC-MS detection,rendering the transfer efficiency of the sample from the sampler to the adsorption tube a crucial indicator for evaluating the sampler's collection efficiency.Despite the lack of literature on the transfer efficiency of Bio-VOCTM breath samplers,this study undertakes an evaluation of the sample transfer efficiency of the Bio-VOCTM breath sampler and optimizes its traditional transfer process.Materials and methods The Bio-VOCTM breath sampler was utilized for collecting simulated exhaled breath samples containing ethanol,acetone,isoprene,n-butanol,n-hexane,and n-heptane.A comparison was conducted between the transfer efficiency observed under traditional and optimized transfer processes.The samples transferred to the adsorption tubes underwent analysis using thermal desorption-gas chromatography-mass spectrometry(TD-GC-MS).Subsequently,the optimization method was implemented to analyze the exhaled breath of the population.Results During traditional operation,the transfer efficiency remains below 50％,with a relative standard deviation(RSD)ranging from 11.3％to 15.6％.However,enhancements are evident by reducing the transfer flow.Following additional optimization,transfer efficiencies reach levels between 90.0％and 101.0％,with an RSD below 5％.Statistical analysis reveals a notable increase in the peak area of VOCs collected using the optimized transfer method(P＜0.01).Discussion In conventional operation,an excess transfer flow might result in insufficient adsorption efficiency between the VOCs and the adsorbent in the adsorption tube.However,despite reducing the transfer flow rate,the enhancement in transfer efficiency was not effectively achieved.This issue could be attributed to inadequate sealing of the sampler,allowing ambient gas to infiltrate the adsorption tube through the gap between the piston and the sampler.To address this,the step of transferring the sample from the sampler should be executed at a swifter flow rate to minimize ambient air introduction through the sampler gap.Furthermore,the transfer to the adsorption tube should occur at appropriate flow rates to ensure thorough sample adsorption while traversing the tube.As a result,the transfer process underwent further optimization to expedite the sample transfer from the sampler to the Tedlar bag.Subsequently,the samples were transferred from the gas bag to the adsorption tube using a gas sampling pump with a flow rate of 200 mL·min-1 in this study.Conclusions The transfer efficiency from the Bio-VOCTM breath sampler to the adsorption tube was inadequate under traditional operation,failing to meet sampling requirements.Nonetheless,through process optimization involving adjustments in the sample transfer flow rate from the sampler to the adsorption tube,notable enhancements in transfer efficiency were realized.This optimization enhances the precision and dependability of employing the Bio-VOCTM breath sampler for alveolar gas analysis.Recommendations and perspectives The optimized operational approach offers insights into the judicious utilization of the Bio-VOCTM breath sampler in exhaled breath analysis,thereby furnishing technical assistance for standardizing the process of acquiring alveolar gas.
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