Methyl Salicylate
Introduction
Thermal desorption is a convenient sample introduction method for Gas Chromatograph (GC) and Gas Chromatograph / Mass Spectrometer (GC/MS) systems, particularly for the analysis of vapor-phase samples. Thermal desorption involves the removal (separation) of compounds retained on a sorbent material by heating in gas flow. The released compounds are transferred in the flow of carrier gas to the analyzer inlet as a small, discreet and concentrated sample vapor. Thermal desorption devices can be used for multipurpose sample introduction, amenable to direct sampling and analysis of volatile organic compounds in gas and liquid-phase.
Commercial standalone thermal desorption systems are often used as an accessory to GC or GC/MS systems. Coupling such a device to the GC or GC/MS often involves time-consuming procedures such as instrument shutdown, re-plumbing, lengthy conditioning, and control with different software. Direct injection capability is also disabled with such configurations.
The standard GRIFFIN 450™ GC/MS/MS system incorporates two integrated sample introduction modules, with no hardware modifications required for operation.
- Split/Splitless Liquid Injector for liquid sampling via Direct Syringe Injection, SPME Fiber, Autosampler (option), and/or Headspace Sampler (option).
- Universal Sampling Port (USP) for vapor sampling via direct air intake through sampling line and/or portable sampling/thermal desorption with the X-Sorber™ (included). The USP is part of the fully integrated Air Sampling Module (ASM) that consists of a sample loop for high concentration gas-phase samples and a preconcentrator for low concentration gas-phase samples.
The integration of multiple sample introduction modules means the Griffin 450 is ready for both gas-phase and liquid-phase sampling and analysis at all times. When equipped with a Griffin 450, operators must only transport one piece of equipment instead of multiple sets, maintain analytical flexibility, and save precious response time because they do not have to stop and connect an external, standalone thermal desorption system.
This application note compares data from the Griffin 450 system equipped with a fully integrated ASM to data collected by a standalone thermal desorption system coupled to the Griffin 450.
Figure 1. The Griffin 450 Mobile GC/MS/MS
Instrumentation
- Griffin 450 GC/MS/MS
- Griffin System Software Suite (GSS)
| Gas Chromatograph and Conditions: | |
| Temperature Program 40 °C hold for 2 min, then increase at 35 °C per minute to 250° C. | |
| Column | Low Thermal-Mass Chromatograph (LTM-GC) Rtx-5ms, 30m X 0.25mm x 0.25µm |
| Carrier Gas | 1 mL/minute Helium |
| Sample | Methyl salicylate (MES) in methylene dichloride |
| Mass Spec Conditions: | |
| ALC enabled with maximum ionization time at 150 ms. | |
| Mass Scan Range: | m/z 50-300 |
| Detector Temp: | 150 °C |
| Injector Temp: | 200 °C |
| Integrated Thermal Desorption via Griffin 450: | |
| Tenax Tube: | 40 °C initial, desorbing at 200 °C for 4 min. |
| Sample Flow Path: | 190 °C |
| Precon Manifold: | 200 °C |
| Standalone Thermal Desorber coupled to Griffin 450: | |
| Desorbing Conditions: | 280 °C for 5 min |
| Cold Trap: | Trapping temperature 15 °C, desorbing 280 °C for 5 min |
| Sample Trap: | 150 °C |
Results /Discussion
MES solutions at three different concentration levels were injected to the sorbent tube of the standalone thermal desorption system coupled to a Griffin 450 GC/MS/MS. The same solutions were also introduced to the Griffin 450 with integrated ASM preconcentrator. Figure 2 shows the MES calibration curve for the Griffin 450 with integrated ASM preconcentrator. A linear curve with R2 of 0.9999 was observed. Figure 3 shows the MES calibration curve for the standalone thermal desorption system coupled to the Griffin 450. A linear curve with R2 of 0.9996 was observed.
Figure 2. MES calibration curve for Griffin 450 ASM preconcentrator.
Figure 3. MES calibration curve for standalone Thermal Desorption system coupled to Griffin 450.
Figure 4. GC/MS result of MES desorbed from the Griffin 450 ASM preconcentrator.
Figure 5. GC/MS results of MES desorbed from the standalone thermal desorption system coupled to Griffin 450.
Figures 4 shows the GC/MS results of MES desorbed from the Griffin 450 ASM preconcentrator. Figure 5 shows the GC/MS results of MES desorbed from the standalone Thermal Desorption System. More extraneous peaks were observed from the standalone Thermal Desorption System.
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These data represent typical results.
Conclusions
The Griffin 450 GC/MS/MS with integrated Air Sampling Module for thermal desorption provides equivalent and in some cases better data results than standalone commercial desorption systems coupled to the Griffin 450 GC/MS/MS system. By offering both liquid and vapor-phase sample inlets on one system, the Griffin 450 offers analytical flexibility in a compact package that is easy-to-use and transport for field applications.
References
1. Wells, J.M.; Badman, E.R.; Cooks, R.G. Anal. Chem. 1998, 70, 438-444.
2. Patterson, G.E.; Guymon, A.J.; Riter, L.S.; Everly, M.; Griep-Raming, J.; Laughlin, B.C.; Ouyang, Z.; Cooks, R.G. Anal. Chem. 2002, 74, 6145-6153.