Agilent Technologies has developed a chemical sensor, the Agilent 4440A, which can rapidly distinguish among similar products with volatile constituents. The instrument consists of a modified Agilent headspace autosampler coupled directly to a modified Agilent mass selective detector. Unlike headspace gas chromatography with mass selective detection (HS/GC/MS), this system has no GC, and there is virtually no separation of the volatile constituents. Instead, the headspace volatiles are transferred directly to the mass selective sensor, which typically gives rise to a single broad peak composed of all the volatile constituents in the sample. Because the mass spectra of all these compounds are also overlaid, multivariate analysis and pattern recognition software are used to classify the samples. The advantages of this system over conventional HS/GC or HS/GC/MS are its speed and ease of use. Samples can be analyzed every 2 to 6 minutes, depending upon the amount of headspace equilibration time required, and operator training takes less than an hour. This application note discusses how the 4440A chemical sensor has been used to discriminate among various products. Most interestingly, this application note also shows how to use the information from the 4440A chemical sensor to identify unknowns.
Agilent Technologies has developed the 4440A chemical sensor, which uses a modified headspace autosampler coupled directly to a mass selective detector without gas chromatography. This system rapidly distinguishes among similar products with volatile constituents by generating composite mass spectra. Multivariate analysis and pattern recognition software, specifically Pirouette, are used to classify samples and identify differences based on volatile components.
| Mass range | 2 to 800 amu |
|---|---|
| Typical mass range for volatiles | 35 to 180 amu |
| Sample analysis time | 2 to 6 minutes |
| Vial equilibration time | 5 to 30 minutes |
| Carrier pressure | 2 psi |
| Vial pressure | 14 psi |
Pirouette from Infometrix is used for data analysis and model building.
The 4440A system has no gas chromatograph and virtually no separation of volatile constituents, transferring them directly to the mass selective sensor.