UC Davis

Trace chemical detection plays an important role in evaluating environmental hazards as well as benign chemical sources. The adequate odorization of natural gas is critical to identify gas leaks and to reduce accidents. To ensure odorization, natural gas utility companies collect samples to be processed at core facilities or a trained human technician smells a diluted natural gas sample. In this dissertation, a low power dual-polarity ionization-based detector was developed. The detector electronics are operated with a single 9 V battery and provide concentration sensitive voltage outputs. The complete assembly and operation of the detector is detailed. The detector can achieve a system step response of ~1.6 s. We performed laboratory measurements with several ionized chemicals using both positive and negative mode. The results showed highly linear responses at trace concentrations as low as 100 ppb. Following, we report a detection platform that addresses the lack of mobile solutions capable of providing quantitative analysis of mercaptans, a class of compounds used to odorize natural gas. Designed to be portable, the platform hardware facilitates extraction of mercaptans from natural gas, separation of individual mercaptan species, and quantification of odorant concentration, with results reported at point-of-sampling. The software was developed to accommodate skilled users as well as minimally trained operators. Detection and quantification of six commonly used mercaptan compounds at typical odorizing concentrations of 0.1–5 ppm was performed using the device. We demonstrate the potential of this technology to ensure natural gas odorizing concentrations throughout the distribution pipeline.