Continuous Real-Time Monitoring of Phosphine Concentrations in Air Using Electrochemical Detectors Interfaced by Radio Telemetry

Abstract

This work involves the novel use of a radio telemetry-based system that continuously monitors phosphine using two different types of electrochemical detectors (ECD/RT). The ECD/RT units were used to monitor phosphine inside and at varying distances from large tobacco storage warehouses. A master controller unit transferred the data to a personal computer that received and displayed the data. Supervisory control and data acquisition software assimilated the data from each ECD/RT unit, displayed and updated it as new transmissions were received, and stored the data in secure databases. Phosphine concentrations outside five warehouses simultaneously under fumigation and at the facility boundaries were <0.3 parts per million (ppm). Phosphine levels ranged from 0 to 580 ppm inside sealed warehouses. A comparison was made between the data collected at an ECD/RT unit approximately 4 m downwind of a sealed warehouse and a colorimetric tube at the same location. The final phosphine concentration from the colorimetric method was 0.05 ppm and the average over the 20-minute collection period for the ECD/RT was 0.13 ppm. This system allows for continuous, remote monitoring around warehouses under fumigation and superior time resolution allowing timely response to fugitive emissions of phosphine.

Determination of phosphine and other fumigants in air samples by thermal desorption and 2D heart-cutting gas chromatography with synchronous SIM/Scan mass spectrometry and flame photometric detection

“…Only a few techniques for the sampling and analysis of airborne phosphine have been discussed in the recent literature, namely: reactive sorption on silver nitrate impregnated tubes with subsequent elution followed by ICP-AES (inductively coupled plasma atomic emission spectrometry) analysis [13], cryo focussing with subsequent GC-ICP-MS (gas chromatography with inductively coupled plasma mass spectrometry) analysis [14], GC-NPD (gas chromatography with nitrogen phosphorus detector) analysis [15], SIFT-MS (Single Ion Flow Tube Mass Spectrometry) determination [16] or GC-TSD (gas chromatography thermionic specific detection) analysis [17], direct injection with packed column gas chromatography with alkali flame ionisation detection [18] or Real-Time Monitoring with Electrochemical Detectors interfaced by Radio Telemetry [19]. The unequivocal disadvantage of these methods is that they confine the analysis to phosphine only (or sometimes additional hydrides) and they restrict the applications to situations where the presence of phosphine is already known.…”

Evaluation of Wireless Phosphine Sensors for Monitoring Fumigation Gas in Wheat Stored in Farm Bins

“…The use of wireless technology for monitoring fumigations would, in addition to being less labor intensive, be an inherently safer technique because of the fact that the monitoring information is acquired at further distances from the grain bins or treatment sites, and would consequently avoid the potential toxic off-gas within the proximity of those structures. Early remote monitoring of phosphine was performed inside and outside of five tobacco warehouses [12]. Their system included radio telemetry and used sensors to successfully monitor the phosphine concentration inside the tobacco warehouses over 12 days.…”