Fast GC for real time detection accepted at #AIHCE

LOCATION: ICC Wabash 3 Title: Fast GC-PID/FID Analyses Using Resistively Heated Columns for Rapid Analyses in the Field Topic 1: Real-Time Detection Systems Presentation Start: 6/19/2012 10:50:00 AM Presentation End: 6/19/2012 11:10:00 AM Author Block: J. Driscoll, PID Analyzers, LLC, Sandwich, MA; P. Smith, US DOL, Salt Lake City, UT; S. Stearns, VICI Valco Instruments, Houston, TX. Presentation Number: SR-111-2 Abstract: Objective: Gas chromatographic analysis times for ketone and aromatics methods (NIOSH 1301, 1501 & 2005) are between 25-35 minutes due to long temperature ramping and cooling times. Also, if peaks are not resolved chromatographically, non-target components may interfere with the analysis. We employed resistively heated columns to reduce the total analysis times by 50-60%, and used the PID/FID response ratios to enhance identification of components of interest. Methods: A field-portable GC with an external laptop was used for the analysis. The column used incorporates new technology based on fused silica tubing (FST). The typical polyimide layer is removed and nickel is electroplated on the outside of the FST column. Superior heat transfer characteristics of the nickel coating allows rapid and efficient heating, and excellent resolution using a 30 m capillary column. A mini-FID was designed that will easy attach to the outlet of the PID in a single detector port to provide improved analyte identification. Results: Initial runs with a series of 12 ketones showed complete separation for 10 of the components by increasing the ramp rate from 10 to 20 degrees C/min, also reducing analysis time to 11 minutes. Separately, we separated 15 of the 17 aromatic target compounds in 14 minutes instead of 35 minutes. Nitrobenzene and naphthalene were not resolved, but the large difference in the PID/FID response ratios for these analytes allows easy identification. Conclusions: We have shown that the resistively heated columns can be used to improve both separations and time of analysis in a field-portable instrument. The use of a second detector (FID) for confirmation of peak identity is more helpful for faster separations where complete resolution is not attained.

Fast GC-PID/FID Analyses using Resistively Heated Columns for Rapid Analyses in the Field

Fast GC-PID/FID Analyses using Resistively Heated Columns for Rapid Analyses in the Field

Oral presentation in Real-Time Detection Systems

 Authors:

John N.  Driscoll, PID Analyzers, Sandwich, MA 02653

Stan Stearns, VICI, Houston, TX 77055

Philip Smith, OSHA Labs, Salt Lake City, UT 84081

Objective- The analysis times for NIOSH ketone and aromatics methods (# 1301, 1501 & 2005) are between 25-35 minutes. The time consuming operations are the long ramping and cooling times required. The other difficulty is that if peaks are not adequately resolved, other components could interfere with the analysis. We will employ resistively heated columns to reduce the total analysis times by 50-60% to 12-15 minutes and use the PID/FID response ratios to enhance identification of components of interest. These ratios have been used previously (1) to identify the molecular structure of hydrocarbons. 

Methods- A PID Analyzers compact GC (<20#) with an external laptop will be used for the analysis that incorporates  new technology developed by VICI  that takes  polyimide-coated fused silica (FST) and removes  the polyimide layer. Then the (FST) is electroplated with nickel.  As a result of the superior heat transfer of the electroplated nickel, we are able to  rapidly and efficiently heat and achieve excellent resolution for a 30M capillary column. A mini-FID was designed that will easy attach to the outlet of the PID taking a single detector port and providing improved identification of components.

Results –For  the initial runs with the series of 12 ketones (NIOSH #1301), we were able to separate 10 of the components by just increasing the ramp rate from 10^o/min to 20⁰ /min. The final time for analysis was 11 minutes. We do have 8 ramp rates and 4 cooling fan rates so with an additional ramp, we should be able to separate methyl amyl ketone and ethyl amyl ketone and use a faster fan rate to reduce the cool down time. For NIOSH Method #1501, we were able to separate 15 of the 17 compounds in 14 minutes instead of 35 minutes. We were not able to separate nitrobenzene and naphthalene but there is a such a significant difference in the PID/FID response ratio that each of the components can be easily identified.

Conclusions 

We have shown that the resistively heated columns can be used to improve both separations & time of analysis. The use of a second detector (FID) for confirmation of peak identity is more helpful for faster separations where complete resolution is not attained.

1.   Driscoll, et al., "Gas Chromatographic Detection and Identification of Aromatic and Aliphatic Hydrocarbons in Complex Mixtures by Coupling Photoionization and Flame Ionization Detectors," J. Chrom., 158, 171 (1978).

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Rapid Separations on a Portable GC with Resistively Heated Columns

Methodology:	Gas Chromatography
Application:	Environmental
Primary Focus:	Application
Title:	Rapid Separations on a Portable GC with Resistively Heated Columns
Keywords:	Detection Environmental Environmental Analysis Gas Chromatography

Assignment Status:	Assigned ORAL		Session Title:	Environmental Analysis: Pharmaceutical and Biologically Active Materials
Session Date	03/14/2012	Starting Time:	( Slot # 7 ) CO-1671

A previous paper (Pittcon 2011 # 180 - 20P  ) on fast GC focused on long (30M) capillary columns with a thick film (5u) programmed quickly over a short range from 50-75C. The analysis was much faster (>2x) as a result of the low thermal mass of the resistively heated column and resultant short cool down time. The detectors used were the photoionization detector (PID), the pulsed discharge detector (PDD) and the Far UV absorbance detector (FUV). The GC was a Model 312 portable GC.

Much of the work on “fast GC” utilizes short (5M) thin films capillary columns to elute solutes  quickly and the result is rapid but inferior separations because of the short column. New technology developed at Valco’s capillary column development center where VICI  takes  polyimide-coated fused silica (FST) and removes  the polyimide layer. Then the (FST) is electroplated with nickel.  As a result of the superior heat transfer of the electroplated nickel, we are able to  rapidly and efficiently heat and achieve excellent resolution for a 30M capillary column. 

The PLOT columns with Hayesep present some interesting opportunities for improvement with Fast GC capability. With a 30M PLOT-S, C1-C5 HC & a ramp @ 8C/min. separates the HC into 4 groups (C1-C2, C3, C4, C5) with several minute gaps between each group for this nearly 18 minute separation. A multilevel rapid ramp could easily reduce the run time to 8 minutes and the total time to 10 minutes instead of 22 minutes.

We evaluated the fast GC with a short (7.5M) column for the analysis of chemical weapons surrogates. Here we were able to reduce the analysis time from 15 minutes to 5 minutes by changing the programming from 70-130C in one minute while still resolving all the peaks.

We will also be evaluating this technology for environmental applications such as  PAH’s and PCB’s which currently can take up to an hour per sample.

Authors: Jack Driscoll, PID Analyzers, LLC and Stanley D. Stearns, VICI Valco