Chromatograph, computer

QA SQPs should specify the amount of data to be audited and how the data points are chosen for audit. An auditor may choose to perform more thorough and more frequent audits on a recently validated system. The validation report can be used to assist in determining what and how much to audit. For example, if data summary printouts from the chromatographic computer system are used in the report, the validation report should be reviewed to verify that this summary function was tested during validation. If this portion of the computer software was successfully validated, verifying a few values from each table in the report may be sufficient. 

The solvent programmer is an apparatus that allows the composition of the mobile phase to be changed, in a defined manner, over a defined period of time, and is normally controlled by the chromatograph computer. There are basically two types of gradient programmer, one that mixes the solvents at high pressure, prior to the column and the other that involves solvent mixing that occurs at low pressures, prior to the solvent pump. 

Quantitative In Silica Chromatograph) Computational Modelling of Molecular Interactions By Toshihiko Hanai Toshihiko Hanai, 2014... 

Once a mixture has been separated into its components it becomes possible to determine the amount of each [58]. This requires a determination of the size of the concentration profile. Two possible methods are available Use of either the peak height or the peak area. The former is more sensitive in the ca.se of GC to fluctuations in details of the injection procedure and the column temperature. and in the mobile-phase composition and column temperature in LC. Peak areas are more sensitive to flow-rate fluctuations in both GC and LC. at least so long as the detector is concentration sensitive. In practice, however, only the peak-area method has been implemented in data packages currently available for chromatographic computers. 

PCC = process control computer PLC = programmable logic controller and PGCS = process gas chromatograph system. 

Whether the optimum phase system is arrived at by a computer system, or by trial and error experiments (which are often carried out, even after computer optimization), the basic chromatographic data needed in column design will be... 

P). Note the expression for (C) is also a function of the particle diameter (dp) and includes known thermodynamic and physical properties of the chromatographic system. Consequently, with the aid of a computer, the optimum particle diameter (dp(opt)) can be calculated as that value that will meet the equality defined in... 

Overall, the technical complexity of the Deans switch system is considerably greater than that of a mechanical switching valve and it is accepted that reliability and ease of use is reduced as the system complexity increases. For many compound types, however, the completely non-intrusive nature of the Deans method offers sufficient advantages to justify its application. However, the use of modern electronic pressure and flow controls integrated into the overall computer control of the chromatographic system does now make the operation of Deans switches significantly easier or more reliable than has been reported in its earlier applications. 

The purification of value-added pharmaceuticals in the past required multiple chromatographic steps for batch purification processes. The design and optimization of these processes were often cumbersome and the operations were fundamentally complex. Individual batch processes requires optimization between chromatographic efficiency and enantioselectivity, which results in major economic ramifications. An additional problem was the extremely short time for development of the purification process. Commercial constraints demand that the time interval between non-optimized laboratory bench purification and the first process-scale production for clinical trials are kept to a minimum. Therefore, rapid process design and optimization methods based on computer aided simulation of an SMB process will assist at this stage. 

Equation (10) describes the elution curve obtained from a chromatographic column and is the equation of the curve, or chromatogram, that is traced by the chart recorder or computer printer. Its pertinence is displayed in figure 2. 

The mixture is identical in each example. The peaks are shown separated by 2, 3, 4, 5 and 6 (a) and it is clear that a separation of 6a would appear to be ideal for accurate quantitative results. Such a resolution, however, will often require very high efficiencies which will be accompanied by very long analysis times. Furthermore, a separation of 6o is not necessary for accurate quantitative analysis. Even with manual measurements made directly on the chromatogram from a strip chart recorder, accurate quantitative results can be obtained with a separation of only 4a. That is to say that duplicate measurements of peak area or peak height should not differ by more than 2%. (A separation of 4a means that the distance between the maxima of the two peaks is equal to twice the peak widths). If the chromatographic data is acquired and processed by a computer, then with modem software, a separation of 4a is quite adequate. 

Each solvent passes from its reservoir directly to a pump and from the pump to a mixing manifold. After mixing, the solvents pass to the sample valve and column. The pumps control the actual program and are usually driven by stepping motors. The volume delivery of each solvent is controlled by the speed of the respective pump. In turn, the speed of each motor is precisely determined by the frequency of its power supply which can be either generated by external oscillators or, if the chromatograph is computer controlled, directly from the computer itself. 

The manifold also receives and mixes solvents from each of the programmed valves. The valves are electrically operated and programmed to open and close for different periods of time by adjusting the frequency and wave form of the supply. Thus, a predetermined amount of each solvent is allowed to flow into the manifold. The valves can be driven by oscillators contained in a separate electronic programmer or if the chromatograph is computer controlled, the controlling waveform and frequency can be provided directly from the computer. 

In their work on the precision of contemporary liquid chromatographic measurements, Scott and Reese (3) also evaluated the precision that could be expected from a computer measuring peak heights and peak areas. They again used twelve replicate samples and the results they obtained are shown in table 2. 

As one might expect, computer data processing is an expensive adjunct to a liquid chromatograph and the more sophisticated reporting systems can be very expensive. An example of a computer print-out of... 

A high pressure gel permeation chromatograph (GPC) has been used to monitor the performance of the reactor. A novel aspect of the GPC is that, it too, has been put on-line to the process control computer and both data collection and analysis have been made automatic while giving the operator full interactive facilities. 

Gel Permeation Chromatography. The instrument used for GPC analysis was a Waters Associates Model ALC - 201 gel permeation chromatograph equipped with a R401 differential refractometer. For population density determination, polystyrene powder was dissolved in tetrahydrofuran (THF), 75 mg of polystyrene to SO ml THF. Three y -styragel columns of 10, 10, 10 A were used. Effluent flow rate was set at 2.2 ml/min. Total cumulative molar concentration and population density distribution of polymeric species were obtained from the observed chromatogram using the computer program developed by Timm and Rachow (16). 

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