In diverse fields ranging from environmental samples to complex flavor preparations, high performance, high resolution capillary gas chromatography/mass spectrometry, GC-MS, has become the preferred technique for identifying and quantifying target compounds at trace levels. Many of these samples are characterized by very complex matrices, which provide a substantial challenge for contemporary capillary GC-MS. This situation is now even more complicated by the current trend towards faster GC analysis using reduced diameter columns, accelerated column heating, or a combination of both.
In complex mixture analysis, new approaches and techniques are needed in order to extract the required data from the total ion current chromatogram. Although two-dimensional GC can chromatographically deconvolve complex samples, it can be a relatively expensive and time-consuming process that may not always be the best choice for routine analysis. Retention time locked GC-MS techniques, with dedicated libraries, work well when the matrix is not too complex. As the complexity of the sample increases, however, a limit is reached beyond which powerful spectral deconvolution algorithms are needed to extract component spectra from complex spectral background.
In this presentation, interactive mass spectrometry deconvolution software (IST for GC-MS) is used to determine the presence of trace pesticide levels in a complex essential oil. The oil is injected without sample preparation and the chromatography is run under accelerated heating conditions at either 40°C/min or 120°C/min to give total run-times of between 5 min and 10 min. The IFD algorithms, the core technology, extend measurement sensitivity by deconvoluting the spectral fingerprint of the target compound from the random nature of instrumental noise. Method detection limits are also improved as the target compound fingerprint is separated from the random “sampleto-sample” variation of chemical background and spectral noise. In this way reporting limits approach method detection limits, which increases measurement precision and robustness. The software has unique and powerful interactive software features for QC validation of target compounds. The simple visual presentation and table format of the scan-to-scan data fit allows the analyst to judge whether the compound is truly present in the sample.
These considerations are true for conventional GC run-times. When fast GC conditions are applied the IFD algorithms become even more useful in extending measurement sensitivity, selectivity, accuracy, precision and robustness of the data produced.
