Chromatographic data system products

Chromatographic techniques represent one of the most significant sources of analytical data found in today s pharmaceutical laboratories. All of the chromatographic techniques produce data that must be acquired, interpreted, quantified, compared, reported, and finally archived (see Chapter 21). Whether the analysis is qualitative or quantitative in nature, the data must somehow be interpreted and reported so that meaningful decisions can be made. It may be as simple as a qualitative decision that indicates whether a reaction has reached completion successfully, or it may be a series of quantitative analyses that help determine if a batch or lot of product meets its specifications and may now be released. This chapter also examines the evolution and perhaps the revolution that has taken place within the chromatography data system (CDS) marketplace. 

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. 

Analytical Methods. Liquefied samples of the feed and reactor effluent were analyzed by gas chromatography. All gas chromatographs were tied to a chromatographic data processing system which determined peak areas and calculated sample compositions. Sample components were identified on the basis of their retention times. Response factors were determined experimentally, using synthetic blends resembling actual alkylation feeds and products. Except In those cases where RON was to be determined on a test engine, n-hexane was added to the samples as an Internal standard. 

The master gas chromatograph is a Varian 2760 instrument with thermal conductivity and flame ionization detection. A second Varian 2760 gas chromatograph (GC-2) serves for analysis of samples from two sources, pyrolysis products from the CDS 820 and from the structural determination function of the CDS 1200. The latter instrument (Chemical Data System) is a functional group and elemental analyzer which generates a vapor-phase thermolytic dissociation pattern for functional group analysis and also performs elemental analysis. The effluent from the master GC is split so that 10% of it is directed to the detector and 90% of it to the CDS 1200. A stop-flow valve admits one... 

The gas chromatograph (GC) resembles the MS in providing both qualitative and quantitative EGA but is significantly slower in operation. The interval between analyses is normally controlled by the retention time of the last component to be eluted from the column such delay may permit the occurrence of secondary reactions between primary products [162]. Several systems and their applications have been described [144,163— 167] sample withdrawal can be achieved [164] without the necessity for performing the reaction in an atmosphere of carrier gas. By suitable choice of separation column or combination of columns [162], it is possible to resolve species which are difficult to measure in a small low-resolution MS, e.g. H20, NH3, CH4, N2 and CO. Wiedemann [168] has made a critical comparison of results obtained by MS and GC techniques and adjudged the quality of data as being about equal. 

In this case the survey scan was set as a full scan and the dependent scan as a product ion scan. The problem with data dependent acquisition is to determine the selection criteria. In most cases the system picks up the most abundant ion in the full scan spectrum. An inclusion list with masses of potential metabolites or exclusion list of known interferences significantly improves the procedure. In the example shown in Fig. 1.39, a procedure called dynamic background subtraction (DBS) was applied. This procedure considers chromatographic peak shapes and monitors not the most abundant signal in the spectrum but the largest increase of an ion in a spectrum. The advantage is that once a signal of a peak has... 

First, the low boiling point (37 C) can lead to handling difficulty. We found it necessary to replace the Waters 6000A pump in the Waters Model 244 high performance liquid chromatograph (HPLC) with a Waters M45 pump to avoid an occasional interruption in flow which we assured to be caused by vapor lock. Second, there are health hazards associated with the use of HFIP, and hygenlc laboratory procedures should be followed. The system should not be used prior to consulting the HFIP Product Information and Material Safety Data Sheet from Du Pont. 

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