Modern chromatographic data systems

Beyond simple data storage and instrument control, modern data systems provide extensive data analysis capabilities, including fitted baselines, peak start and stop tic marks, named components, retention times, timed events and baseline subtraction. Further, they provide advanced capabilities, such as multiple calibration techniques, user-customizable information and reports and collation of multiple reports. If a Laboratory Information Management System (LIMS) is available, the chromatographic data system should be able to directly transfer data files and reports to the LIMS without user intervention. The chapter by McDowall provides a terse but thorough description of the... 

A modern gas chromatograph, whether configured for packed or capillary column use, consists of several basic components. All of them must be properly chosen and operated for successful analysis. These are pneumatics and gas-handling systems, an injection device, an inlet, a column oven and column, a detector and a data system. Since the inception of GC in the 1950s, instrumentation has evolved significantly as new techniques and technologies were developed. This section provides an overview of the major components of a modern gas chromatograph, with details about how to choose components based on analytical needs, and applications. 

Today, most modern data systems provide a comprehensive array of quantitation methodologies. In general, chromatographic peaks may be quantitated using area, height, % area, and % height. Within these basic techniques, the chromatographic assay may also require the use of an Internal Standard to help correct for injector variability or sample-prep... 

Extremely complex mixtures can be separated and quantitatively analyzed by modern chromatography techniques. However, having achieved a separation, the structure of any hitherto unknown substances present in the mixture remains to be elucidated or the presumed identity of the expected components still needs to be confirmed. Generally, chromatographic data alone is insufficient evidence to substantiate the presence of a specific substance in a mixture. Supporting evidence from other analytical systems is considered essential before the identity of a substance can gain legal acceptance. 

LC is a sensitive, adaptable, and quantitative analytical technique to separate compounds that are dissolved in solution. Figure 3 depicts the main components of a modern LC system (1) a pump with a constant flow control, (2) a high-pressure injection valve, (3) a chromatographic column, (4) a detector, and (5) a data system for measuring peak areas and retention times (Figure 3). 

The GC data system performs the tasks of recording, handling, evaluation, and documentation of the chromatogram. In a modern gas chromatographic system, these can be performed by means of a computer with specialized software. Nowadays, software for calculating the quantitative results and for the method validation is available. " ... 

The preceding discnssion has attempted to snmmarize some general fnndamental concepts nnderlying the practical goal of integrating appropriate chromatographic peak areas (e.g. EIC vs TIC). Modern mass spectrometer data systems inclnde integration rontines and these are briefly discussed in Section 7.4.3 bnt practical issues... 

The system shown in Fig. 4.11 is designed to dehver optimal performance when coupled to sample-preparation, sample-introduction and data-handhng products available. The HP 6890 series GC offers a smooth transition for users of HP 5890 series gas chromatographs through methods compatibihty, extremely useful for modern laboratories whose methodology is costly to develop. 

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