Saturday, January 16, 2016

Onsite real-time analysis of fumigants via GC-PID/TCD



ANYL 335 
PAPER TITLE: Onsite real-time analysis of fumigants via GC-PID/TCD 

DIVISION: Division of Analytical Chemistry
SESSION: Advances in Analytical Separations
SESSION TIME: 8:00 AM - 11:45 AM

PRESENTATION FORMAT: Oral 
DAY & TIME OF PRESENTATION: 9:20am-9:45am 
AUTHORS (FIRST NAME, LAST NAME): John N. Driscoll2 , Jennifer L. Maclachlan1 INSTITUTIONS (ALL): 1. PID Analyzers, LLC, Centerville, MA, United States. 2. PID Analyzers, LLC, Sandwich, MA, United States. ABSTRACT BODY: Abstract: Although many different chemicals have been used as fumigants for agricultural products and soils, we have focused on some of the more common fumigants that can be detected by gas chromtaography (GC) using a photoionization detector (PID). These include methyl bromide, 1,3 dichloropropene, phosphine and methyl isothiocyanate (MITC). Deaths from fumigants have occurred in ships, grain elevators, soil fumigation, green houses, and even residential sites. A field method for detecting common fumigants is essential since many workers encounter these toxic chemicals, which do not have OSHA field detection methods. CA Deptartment of Pesticide Regulation requires that an area which has been fumigated and aerated must be checked for safe levels of that fumigant before entry into the area. Using a Model 312 portable gas chromatograph (GC), which is battery operated and weighs 26 pounds, it is possible to detect ppb levels of some common 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. For phosphine, a 6’ x 1/8” porous polymer column is used for the chromatography since it is a gas. If a thermal conductivity detector (TCD) is used on the same GC, it can detect all of the common fumigants during the fumigation process since it is a universal detector with a response from 0.1% to 100% levels. All of the compounds above have ionization potentials between 10.1 and 10.5 eV so these compounds be detected at ppb levels by GC-PID. The MITC hydrolyzes to methyl isocyanate (MIC), so this is the active component to be detected. The TCD does respond to all of the fumigants both organic and inorganic. A portable GC-PID with a thick film capillary column or a 6’ porous polymer column can detect methyl bromide, 1,3 dichloropropene, phosphine and methyl isothiocyanate (MITC 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. If a GC-TCD is also used, the GC-TCD can monitor any of the fumigants during the process of fumigation.

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