When monitoring air pollution with continuously operating automated GC-systems, large and complex datasets are produced. Managing and processing these amounts of data require a new approach in order to obtain highly reliable results. Not only peak integration, but also compound identification and concentration determination need to be rigidly automated for correct peak assignment and quantification. At the same time, processing should remain flexible enough for optimal tuning of critical resolved pairs and for specific quantitation requirements. Finally, processing should comply with GLP constraints, such as traceability and consistency.
The MetaChrom software package has been designed to meet these needs. Raw data (i.e. retention times and peak areas or heights) from any commercially available integrator form the basis for processing. Raw data is not altered by MetaChrom in any way. The consistency of all results is maintained by automatically reprocessing after any relevant modification of processing parameters, through consistent presentation of new results, and by keeping an audit trail. Manual overrides may be applied when abnormal conditions have dramatically affected the chromatography. Each such manual adjustment is clearly marked.
Identification and quantification parameters can be tuned in an easy, explorative way to determine the best parameter settings for a complete dataset. The effect of modifying a parameter is instantly visible in various overviews, showing actual results as well as the quality of the identification and quantification processes. Anomalies are easily recognized and can be examined in more detail. A central overview, the Frequentogram, clearly shows all identified and unknown compounds as peakclusters. By applying a simple algorithm it is easily and quickly shown that retention time variations are reduced to a minimum and that the identification of critical resolved pairs can be substantially improved. This algorithm is fully controlled by a few parameters and is based on relative retention times by designating any of the abundant compounds as "retention time calibrating peaks".
Quantification is usually based on one or more calibration analyses including all compounds. However, identified as well as non-identified compounds can also be quantified using the detector response factors obtained from any of the other compound calibrations. Various calibration methods are available, including single- and multipoint, linear and non-linear. Processing results from a number of simultaneous analyses, using simultaneous detectors or different columns or both, can be combined for improved identification and quantification of compounds.
Once parameter settings have been tuned, hundreds of chromatographic analysis result files can be processed simultaneously. New input data is processed without operator intervention and presented in selected overviews. The arrival of new data is continuously shown and the process of identification and quantification can easily be monitored. If required, parameters can be re-tuned without any loss of consistency and traceability.
At any given time, a full or partial selection of the results can be reported using flexible report file formats, designed for immediate use from spreadsheet-, statistical-, modeling-, and graphing-software packages, as well as for loading into databases and final report documents. Generated reports are uniquely identified for traceability and are automatically mentioned in the audit trail. Reports include sample identity, compound identity and the concentration, as well as indicators for the quality of identification and quantification. Various other reports are available for details such as process parameters, manual overrides, calibration parameters and audit trails.
On several sites, MetaChrom has proven to be a prerequisite for monitoring.
MetaChrom is available for Microsoft Windows and for Apple Macintosh.