Tuesday, February 4, 2014

Field Measurement of Common Fumigants via Portable GC with PID & FUV Detectors

The session "Real Time Detection Systems II",  PO123 occurred on June 4, 2014 from 10:00 AM to 12:00 PM.  

AUTHORS (FIRST NAME INITIAL LAST NAME): J. N. Driscoll1, J. L. Maclachlan1PID Analyzers, LLC, Sandwich, Massachusetts, Massachusetts, UNITED STATES


CURRENT TOPICS: Real-Time Detection Systems
Field Measurement of Common Fumigants via Portable GC with PID & FUV Detectors

Objective: More than two dozen different chemicals have been used as fumigants for grain including organics like methyl bromide, inorganic chemicals like sulfuryl fluoride ,and even chemical agents such as cyanogen chloride. Deaths from fumigants have occurred in rail cars, ships, grain elevators, green houses, pest control … A field method for detecting common fumigants is essential since many workers encounter these dangerous chemicals which do not have OSHA field detection methods.

Utilizing a portable gas chromatograph Model GC312 equipped with a battery and weighing in at 26 pounds, this field tool can detect part per billion (ppb) levels of fumigants with a photoionization detector (PID). A 30M x 0.32 mm capillary with 5 or 10 micron methyl silicone film is used for separating gases and volatile compounds. The far UV absorbance (FUV) detector detects the low or sub ppm levels of a variety of hydrocarbons & low molecular weight (MW) gases such as hydrogen cyanide, sulfur dioxide, and sulfuryl fluoride that absorb at 126 nano meters (nm).

Results : 
Some of the common fumigants used today are methyl bromide, ethylene oxide, phosphine, and ethylene dibromide. All of these compounds can be detected at ppb levels by GC/PID with a thick film capillary column. The PID has a detection limit of < 5 ppb for PH3, and can detect part per trillion (ppt) levels of dibromochloro propane (PEL = 1ppb) by PID if the internal concentrator on the portable GC is used. The FUV can detect hydrogen cyanide, ethylene dichloride, dichloropropane, sulfur dioxide and sulfuryl fluoride at low or sub ppm levels. The detection limit for SO2 by FUV is 0.5 ppm.

A portable GC with a thick film cap column equipped with PID and Far UV detectors can detect the most common fumigants in use today at levels of 0.1 of the PEL. The portable GC is easily carried to the field and can be operational in about 20-30 minutes. It can detect the ten most common fumigants described above plus many of the more than two dozen chemicals used in fumigation.

Below is a new application note illustrating the use of our Model 100 series portable analyzer for fumigant gas analysis

No comments:

Post a Comment