Friday, May 11, 2012

Sensitivity matters

Updated blog post: April 16, 2014

Jack Driscoll and Fred Spaziani: the founding fathers of HNU Systems, Inc. applied the photoionization detector to gas chromatography in 1976. Having borrowed a Tracor GC equipped with a Flame Ionization Detector and utilizing Fred's uncanny mechanical engineering skills, they built a crude version of the PID modeled after the portable PID they had introduced to the industrial hygiene market in 1974 and modified the detector to run on the Tracor. The purpose of this exercise was to develop a sensitive detector for hydrocarbons. What they had not expected to find was that their PID was fifty times more sensitive than the FID for aromatic hydrocarbons! 

The HNU PID is one of the most sensitive detectors available for VOC’s. It has the widest dynamic range of any detector available and does not require any support gases except the carrier.

The photoionization detector (PID) is used for the measurement of low (ppb) organic and inorganic species that can be ionized by the UV lamp (9.5, 10.6 and 11.7). Nearly 20,000 of these detectors have been sold worldwide since it was first released by HNU Systems in 1976. It has been used for the measurement of VOC’s in water (EPA method 602, EPA Method 50--, EPA Method SW846…, numerous OSHA methods), quality control.

There are two Models that are described below:
  • The Model PI52 has a PID, a power supply for the lamp and bias and an electrometer. The electrometer output is 0-10 VDC. The customer needs a separate ADC channel to feed the signal into the GC’s data system. Alternately, PID Analyzers sells a data system (Model 50) that will feed the signal into a separate PC.

  • The Model PI51 has a PID and a power supply for the lamp and bias. Here, the customer uses the electrometer (FID type with a positive bias) already in the Gas chromatograph. This should already have the ADC connection to the customer GC data system.
Driscoll published a paper in 1978 on the work with Spaziani (1976) described above. Although it is over thirty years old, the analytical technique remains relevant today. In fact, we will be presenting a modernized version with the PID/FID coupling on the fast GC at the American Chemical Society Fall National Meeting in August 2012 in Philadelphia.

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