Direct instrument control

Direct instrument control (or the lack of it) was an important issue for the earlier version of CDS. The scheme of connecting the detector channels through A/Ds to CDS worked well in analytical laboratories across the pharmaceutical industry. The scheme provided enough flexibility so that the CDS could collect data from a variety of instruments, including GC, HPLC, IC, SFC, and CE. It was equally important that the CDS could be connected to instruments that were manufactured by different vendors. It was not uncommon to find a variety of instruments from different vendors in a global pharmaceutical research company. The disadvantage of this scheme was that the instrument metadata could not be linked to the result file of each sample analyzed. It could not be guaranteed that the proper instrument parameters were used in sample analysis. Another need came from the increased use of... 

Since this is a batch system, it might be advisable to use direct digital control. Undoubtedly the throughput could be increased over that with the more traditional analog control system. However, the initial costs and maintenance expenses would also increase. To fully instrument the system would also greatly complicate the equipment required, especially for feeding the reactors (this is discussed later). An economic balance should be run to determine whether this is feasible. I feel it would not be warranted, and have chosen to instrument the plant in the traditional way. 

This field is therefore at an exciting stage. Ion-selective electrodes have a proven track record in terms of clinical and biomedical analysis, with a well-developed theory and a solid history of fundamental research and practical applications. With novel directions in achieving extremely low detection limits and instrumental control of the ion extraction process this field has the opportunity to give rise to many new bioana-lytical measurement tools that may be truly useful in practical chemical analysis. 

This level of control requires a controlling script from the instrument vendor and is for more serious programmers. Direct HPLC control by the MS and multiple staggered LC capabilities provided by several autosampler and instrument vendors fulfill the function but may limit the hardware used or require purchase of software/hardware. 

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... 

Automated qualification software is yet another area of CDS development that has been affected by regulatory compliance. When you look at today s CDS solutions, it is typical to see the system providing direct digital control of the instrumentation. Many CDS manufacturers offer software tools that are capable of automating the installation qualification (IQ) and operational qualification (OQ) process. In addition, some manufacturers also offer software that can automate the performance qualification (PQ) for the various forms of instrumentation that it is capable of controlling. These automated software tools are not only time savers for the laboratory, but they also help to properly document the system qualification effort. 

The Finnegan single stage quadrupole powers a very flexible system for several analytical problems. The user has a choice of electron ionization positive chemical ionization or negative chemical ionization. The Quadrupole can be Hnked to gas or Hquid chromatography and several direct insertion probes. The data features powerful, multilayered software using high performance workstations, that make data analysis and instrument control easy. 

Modifier Pump. The first feature in our adapted design is the introduction of a liquid pump via an instrument controlled VALCO (Model E04, Valeo Instruments, Houston, TX), four position selection valve. We have used an LKB Model 2150, dual piston pump for pumping modifier and entrainer fluids (LKB-Produkter AB, Bromma, Sweden). However, any suitable liquid pump could be substituted. Only pure fluids such as carbon dioxide have been introduced with the Suprex system syringe pump. With the addition of this second pump to deliver liquids, modifier is introduced directly into the extraction vessel. A wide range of alternative fluids and fluid mixtures can be rapidly selected with this dual pumping option. The criteria for selection of a modifier pump include the ability of the pump heads to withstand pressures in the range of 100 to 300 atm and interfacing capabilities, i.e. the ability to be turned on and off by the Suprex contact closure controls. 

Instrumental control over the sensitivity of potentiometric sensors will allow controlled ion uptake by the membrane, thereby generating strong super-Nernstian responses. Advances in this direction were recently realized with double- and triple-pulse experiments, where well-defined current and potential pulses were used for accurate control of the otherwise highly transient transport and extraction process [88]. 

Since a digital instrument functions at fixed points, that is discontinuous, any direct microprocessor control of an experiment has to be in steps. For example, a linear sweep appears as a staircase instead of a continuous ramp. To minimize these effects there are two possibilities ... 

Conventional microwave ovens are used less often for microwave chemistry today. Microwave reactors for chemical synthesis are commercially available and widely used in academia and in industry. These instruments have built-in magnetic stirring, direct temperature control of the reaction mixture, shielded thermocouples or IR sensors, and the ability to control temperature and pressure by regulating microwave output power. 

A pilot plant can be computer controlled in one of two ways supervisory or direct digital control as shown in Fig. 10. In the first, a computer supervises another primary control element. In the second, the interfacing element is eliminated and the controller (e.g., a valve) is regulated directly. New computer-based automatic instrumentation is likely to be supervisory because it is faster and less expensive. (See also Refs.P - l.)... 

Biotrace International (Bridgend, UK) and was mounted so that the light measurements could be made directly from the reaction chamber. As a developmental iteration the National Instruments control hardware was substituted for electronic control components integrated into a light tight box together with the fluidic block. A compact controlling computer was built in order to make the device portable. 

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