Chromatographic data systems CDS

Most of the instruments used in the laboratory are commercial off-the-shelf (COTS) instruments, and consequently the users have little or no input into their design. A full system development life-cycle (SDLC) approach [8], which is used to develop complex computerized systems such as Laboratory Information Management System (LIMS) or Chromatographic Data System (CDS) or custom design laboratory equipment, is not appropriate for COTS instruments. Some laboratory instruments such as a pH meter or centrifuge are fairly simple and therefore do not warrant the SDLC approach. 

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. 

There is hardly any laboratory without at least a computerized instrument. A good example is the Chromatography Data System (CDS). Before, these instruments create graphs on a paper, and we cut them out and weigh them to determine the component. Today every chromatograph is connected to a CDS, which makes all the calculations according to how we set it up. 

Experimental Procedure. Figure 3 presents a schematic diagram of the apparatus. The chromatograph is a Varian Aerograph Series 1400 with a thermal conductivity detector and an associated Varian CDS 111 Chromatography Data System (integrator). We modified the chromatograph in two ways ... 

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 chromatographic system incorporated a Varian (Walnut Creek, CA, U.S.A.) Model 5000 liquid chromatograph, a Varian CDS lllL data system and a Valeo injection valve fitted with a 10 1. injection loop. Solute elution was monitored with a Perkin Elmer... 

Gas Chromatograph Hach/Carle AGC Series 400, Model 04192-A Data Aquisition Peikin-Elmer Sigma 15 Chromatography Data System Sample Handling Vacuum manifold with Validyne Model CD 223 Digital Manometer. 

In the late 1970s, Hewlett-Packard introduced the HP-3300 series data-acquisition system, which was able to connect to 60 chromatographic instruments through an A/D converter. This was the beginning of what would become a revolution in CDS development within the analytical instrument industry. By the mid-1980s, all of the major analytical instrument manufacturers offered network-based data-acquisition systems Beckman, HP, PE, VG, and Waters. These were multi-user, time-sharing systems that used A/D converters to acquire data from the instruments. Instrument control, both HPLC and GC, was a capability that would soon follow. Several CDS manufacturers offered serial control of the HP 5890 GC while Waters also offered instrument control for their own HPLCs. 

It should be noted that regardless of the CDS used, a data-acquisition rate that is too low will produce a peak that is impossible to integrate accurately. There must be enough data points to define the peak accurately. It is always safer to have too many points across a peak than too few, provided that the noise generated by the A/D is sufficiently lower than the detector noise generated by the chromatographic system. 

Virtually all client server CDS systems will have a buffering capacity within their A/D or data collection units (if acquiring digital data from chromatographs via network interfaces). Therefore, part of the adequate size requirements must be the ability to capture and buffer data if the network is unavailable, followed by the successful transfer of data to the server when the network connection is reestablished. 

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