Monday, August 15, 2011

Advantages of a Hyphenated PID/MS Combination for GC Applications #pittcon 2012

Advantages of a Hyphenated PID/MS Combination for GC Applications 
Accepted for POSTER Presentation Pittcon 2012:    ACS Analytical Chemistry Divison 
Slot #24 03/12/12

Methodology: Gas Chromatography/Mass Spectrometry

Flavor/Essential Oil
Forensic Chemistry
Gas Chromatography/Mass Spectrometry

Authors & Affiliations:
Jack Driscoll, PID Analyzers, LLC
Clifford M. Taylor, Shimadzu Scientific
Jennifer Maclachlan, PID Analyzers, LLC

There are many situations where a second detector can save time and effort, even for a mass selective detector (MSD).  These include critical analyses (forensic samples) where duplicate analyses are needed, where small samples or low concentration samples are being analyzed, where flavors or odorous compounds are being analyzed or if a high level sample is being analyzed.

The photoionization detector (PID) is a very sensitive, non destructive detector for VOC’s (low or sub ppb), with a wide dynamic range (>5 x 107. When arson samples are analyzed, one serious problem is a “no detect”. When a sample is not detected, one is required to run additional samples to confirm those results since it could be either a bad injection or bad sample. If a second sensitive detector is run at the same time and a small peak is observed then only one additional sample has to be run.   In addition, the data generated in arson analysis must be legally defensible - this creates the need for duplicate sample analysis (or dual detector analysis) as well as sample archival.

The PID is non destructive so the effluent, a flavor component, can be sniffed as the peak is being detected. This allows olfactometry to be coupled with the specific identification of a peak. No splitter is required. Elimination of the splitter is an advantage since a small difference in flow could cause an error in identification of the peak. The PID is very sensitive for aromatic hydrocarbons. The detection limit of the PID is 0.5 ppb of benzene so low levels of sample can be detected and “no detects” should be minimized. The PID is not easily contaminated by high levels of sample. If the MSD is run downstream of the PID, and a low dead volume valve is in front of the MSD, then a high level sample could be switched to minimize contamination of the MSD.

We will evaluate these applications and others to determine the feasibility of using a second detector in combination with the MSD.

No comments:

Post a Comment