Why do I need a PID for my laboratory?

The PID Analyzers photoionization detector (PID) is one of the most sensitive GC detectors ever developed.

Features include the following:
    Easy to use
    Sub ppb detection of aromatic hydrocarbons
    Wide dynamic range 10⁸
    No support gases are required
    Can be used to upgrade an old GC
    Ideal to add on to a new GC
    Non destructive so a second detector can be run in-series
    Response factors for two detectors can provide identification of species
   

    The PID is used for many EPA Methods 502, 602, SW846....
     

Measurement of ppb Levels of Gasoline in Groundwater by Portable GC-PID

Contamination of groundwater and soils by leaking underground storage tanks continues to be a serious environmental problem. Twelve  years ago, the EPA was monitoring about 370,000 leaking underground storage tank sites in the United States. Only about 5% were scheduled for site cleanups in 2001.  Cleanups are funded by the EPA's LUST Trust Fund, which was funded at a level of about $70 million per year. The University of Colorado at Boulder has summarized the information on Leaking Underground Storage Tanks at the following link:

http://bcn.boulder.co.us/basin/waterworks/lust.html

HNU, working with Jim Stuart, Professor Emeritus, University of Connecticut, has shown that a portable GC with a photoionization (PID) is an ideal tool for analyzing gasoline samples in groundwater and soil.  The recently introduced portable GC (Model 312 see photo) has an improved PID, improved range, is more lightweight & compact, is battery operated and will run off the 12 VDC in an automobile. Thus local power requirements are not necessary.

Photo GC312 Portable GC

Aromatics are among the most hazardous components of gasoline (the EPA maximum contaminant level in drinking water is 5 ppb of benzene). The PID has a higher sensitivity to aromatics than to any other hydrocarbons making this GC-PID ideal for cleanup of gasoline contaminated sites. EPA CLP methods as outlined in SW-846 include’ Method 3810, a headspace method for VOC’s, that provides the rapid screening of large numbers of samples.

Note that the detection limits for benzene, toluene, ethylbenzene, xylenes, TCE & PCE are all at the ppt level with just a 50 mL sample injection. The PID has a dynamic range of nearly 10⁸ . The GC312 software has a 4 point calibration so that the results can be kept linear over a wide concentration range. Some typical response curves are shown in the Figure below.

Calibration Curves for benzene and toluene

The headspace method can be performed in the same 40 mL VOA vials that samples are collected in for lab analysis. After completely filling with sample, cap the vial with a teflon faced septum. To produce the headspace, remove 10 ml of the water via a syringe (filled with clean air) while keeping the vial inverted. Shake for about 2 minutes. Remove a 25-100 mL headspace gas sample for injection into the GC.  The Table below displays the excellent results for the field headspace and the purge & trap lab GC results.

For more information on our GC312, visit our website at http://www.hnu.com  

A New PID for Trace Analysis

I have had a number of requests for copies of my paper from Pittcon 2010 entitled " A New PID for Trace Analysis". This presentation describes the 4 th generation PID which was first introduced by us at the Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy in Cleveland, OH in 1976. The 4th generation detector with improved sensitivity and lower dead volume is shown below:

4 th Generation PID

 See  presentation below.

A New PID for Trace Analysis PC2010a

Is a PID more sensitive than an FID?

A photoionization detector (PID) for gas chromatography (GC), with a proper design should be 50-100 times more sensitive than a flame ionization detector (FID) click on PID-FID ratios.  Some PIDs only have the same or less sensitivity than an FID. The PID Analyzers PID has a dynamic range of 10 exp 8 click on ( 4th-generation-photoionization-detector) and a detection limit of < 1 ppb of benzene   click on (ppt-levels-of-benzene-in-air-by-pid ) .  Contact us at http://www.hnu.com

Is is interesting to note that when we (HNU) introduced the 1st commercial PID in 1976 at #Pittcon in Cleveland, and we stated that  "Our PID is 50 times more sensitive than an FID for benzene", we were greated  with skepticism. Today, 35 years later, many people are still unaware that the PID has this kind of sensitivity.

Photo of PID

ppt Levels of benzene in Air by PID-GC

A PID Analyzers Model 312 GC (http://www.hnu.com) with a photoionization detector  (PID-10.6 eV lamp) is shown below and was used to detect ppt (parts per trillion) levels of benzene in an air nitrogen mix.  A 100 ppb standard of benzene in air was diluted with prepurified nitrogen to obtain  ppt levels of benzene. A chromatogram with 500 ppt of benzene is show in the Figure below.

The column was a 30M x 0.32 mm id with a 5 micron film of methyl silicon ( http://www.vici.com/). The column flowrate was 6 cc/min of hydrogen with an additional  makeup of 6 cc/min. The temperature was isothermal at 120C.  The sample was injected with a 10 port valve that had a 0.2 cc loop.


Our PID, with a sealed window, is the most sensitive one available since ppt levels of aromatics can be detected by direct injection without preconcentration.  This detector has a very wide dynamic range of 10⁸.

GC Detectors: Low ppb Levels of BTEX in water by Headspace GC

GC Detectors: Low ppb Levels of BTEX in water by Headspace GC: "We have used a PID Analyzers GC312 (portable GC) with a photoionization detector (PID) http://www.hnu.com/ for analysis of VOC's in water us..."

Low ppb Levels of BTEX in water by Headspace GC

We have used a PID Analyzers GC312 (portable GC) with a photoionization detector (PID) http://www.hnu.com/ for analysis of VOC's in water using the headspace method (40 ml VOA vials). The sample injected was 0.2 cc of headspace. A 1 ppm mix of 524.2 was prepared as a standard. The BTEX compounds were identified and used as standards for analysis of unknown field samples. A 30M x 0.32 mm id with a 5 micron film of methyl silicon ( http://www.vici.com/ The chromatogram for the standard is shown below:

One of the samples containing 20 ppb of BTEX  is shown below:

The sensitivity of the method is displayed in the following sample that was found to contain 3 ppb of benzene:

This method clearly has ppt level capability by simply injecting a larger sample volume eg 1 cc instead of 0.2cc. The headspace GC method is ideal for field measurements since it  requires little incremental equipment (40 ml VOA vials, 1 cc gas tight syringe) and is easy to implement.