Large volume injection of explosive compounds using the CIS 4

Martin Perkins

17th September 2013

Explosives can be demanding analytes

The analysis of explosives by GC can be very demanding. Explosive compounds can be very polar and stick to many surfaces; they are also thermally labile and often disappear from the chromatogram entirely, degrading into light, gaseous compounds.

LC-MS is often a better bet, but doesn’t suit every customer’s needs.

The application note, Large Volume Injection of Selected Explosives using the GERSTEL CIS 4 PTV Inlet and Agilent 5975C GC-MS, shows the effectiveness of the GERSTEL CIS 4 inlet, when used in solvent vent mode for large volume injections (LVI) for this challenging application.

An LVI method was developed by Anatune’s application chemists for the analysis of five explosive compounds – Nitroglycerine, Dinitrotoluene, Trinitrotoluene, Pentaerithyritotol Tetranitrate, and Research Department Explosive – in which analytes needed to be diluted in both dichloromethane (DCM) and isopropyl alcohol (IPA). This resulted in two slightly different analytical methods.

Calibration standards were analyzed on an Agilent 7890A-5975C GC-MSD. The GERSTEL CIS 4 PTV inlet with Universal Peltier Cooling (UPC) was used as the injection port and speed programmed injections were performed using a GERSTEL MPS. Injection speed was optimized using the GERSTEL LVI calculator.

This instrumental set-up worked very well and two points stood out:

  1. Cooling using the UPC gives excellent temperature stability at 20 degrees Celsius, which is critical when performing LVI as small changes in inlet temperature can dramatically affect solvent evaporation rates and precision as a consequence (note that a low initial temperature was readily obtained without the use of cryogenics).
  2. Excellent precision was observed for 100ul injections in IPA and DCM. The generated correlation coefficient of > 0.998, indicate that the method is suitable for fully quantitative analysis.

The GERSTEL CIS 4 is designed specifically to produce the best chromatography for sample introduction into high resolution capillary columns. The CIS 4 provides unsurpassed temperature control and sample transfer by using patented heating/cooling technology and an optimized 2mm inner diameter liner.

The CIS 4 is designed for use with Agilent Technologies 7890, 6890 and 6850 gas chromatographs. It can also be retrofitted into these models.

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