Tuesday, September 20, 2011

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
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

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