System suitability parameters

PQ is the demonstration that the entire system functions as one unit. PQ is also the demonstration that the system works as you intend to use it. This is done by running an assay and ensuring all system suitability parameters are met. If a number of different methods are going to be run on the system, then the worst-case method should be selected. It is not necessary to run every method on the system, but tbis can be done. 

In the System Suitability section, different parameters are described which can be applied in order to check the behavior of the CE system. The choice of the appropriate parameters depends on the mode of CE used. The system suitability parameters include retention factor (k) (only for MEKC), apparent number of theoretical plates (N), symmetry factor (Af), resolution (Rs)> Rtea repeatability, migration time repeatability, and signal-to-noise ratio. Practical equations to calculate different system suitability parameters from the electropherograms are presented, which are also included in Table 3. 

The evaluation of robustness should be considered in the development of the assay and will depend on the type of procedure under development. It must show the reliability of a method with respect to deliberate variations in method parameters. If measurements are susceptible to variations in analytical conditions, the analytical conditions should be suitably controlled or a precautionary statement might be included in the procedure. One consequence of the evaluation of robustness may be that a series of system suitability parameters is established to ensure that the validity of the analytical procedure is maintained whenever used. Typical parameters to be tested would be the following sample concentration, sample stability, labeling variability (if applicable), injection variability, reagent lot-to-lot variability, and capillary vendor. 

The system suitability tests are performed to verify that the analytical system meets predefined acceptance criteria at the time of performance. System suitability parameters should be established based on the type of method being considered and before the validation of the method actually starts. A common method of system suitability will request bracketing reference injections, with measurable quantitative acceptance criteria, such a migration time and/or a range on the main peak area. The peak of interest can be the major peak but it can also be a secondary peak, which may give more control over the sample preparation (e.g., the HMW peaks in non-reduced CE-SDS or incomplete reduced in the case of reduced CE-SDS LIE). 

Computerised data handling systems will generate reports including a number of system suitability parameters. Figure 10.11 shows a chromatogram with a report form appended. In order for the report to be generated, the computer has to be given... 

Other results obtained from the ruggedness test are the definition of optimized method conditions for the factors and of system suitability criteria for a number of responses. System suitability parameters [6,17] are defined as an interval in which a response can vary for a rugged method. The system suitability criteria are the range of values between which a response (e.g. retention time, capacity factor, number of theoretical plates, resolution) can vary without affecting the quantitative results of the analysis. For instance, a design is performed and the retention time of the main substance varies between 200 s and 320 s without affecting the quantitative determination of the substances. The system suitability criteria for the retention time is then defined as the interval 200 s - 320 s. 

Other results from a ruggedness test described by some authors are the definition of rugged intervals and of system suitability parameters and the selection of optimal values for the factors. Rugged intervals are defined as the interval between the levels of a factor for which no significant effect is seen on a response [19]. 

System suitability parameters [6,17] are defined as an interval in which a response (e.g. retention time, resolution, number of theoretical plates) are allowed to vary for a robust method. They can be derived from the minimal and maximal result for the considered response as seen with a design in which the quantitative results of the method were found to be rugged. 

If analytical measurements are susceptible to variations in the analysis parameters or sample preparation conditions, the method must be suitably controlled or a precautionary statement must be included in the written procedure that alerts the chemist to the susceptibility. The method s system suitability parameters should be defined in such a way that meeting all system suitability criteria would ensure that the method is currently being performed within the acceptance window provided by validation robustness testing. 

In eluent compositions beyond those that are typically part of the routine adjustments carried out by the analyst to meet system suitability parameters. As expected, the use of short columns packed with 3-um particles results in reduced solvent consumption and reduced mobile phase re-equilibration time in gradient elution. 

Unless otherwise directed in the monograph, system suitability parameters are determined from the analyte peak. 

System suitability parameters with their respective acceptance criteria should be a requirement for any method. This will provide an added level of confidence that the correct mobile phase, temperature, flow rate, and column were used and will ensure the system performance (pump and detector). This usually includes (at a minimum) a requirement for injection precision, sensitivity, standard accuracy (if for an assay method), and retention time of the target analyte. Sometimes, a resolution requirement is added for a critical pair, along with criteria for efficiency and tailing factor (especially if a known impurity elutes on the tail of the target analyte). This is added to ensure that the column performance is adequate to achieve the desired separation. 

TABLE 9-22. System Suitability Parameters Determined as a Function of Concentration of H3PO4 (v/v%)... 

In addition to validation of the automation, full validation of the chromatographic procedure, as described in Chapter 12, should be conducted for late-phase methods. This should include specification of system suitability parameters to ensure that the performance obtained during method development and validation is maintained during routine use. The system suitability parameters may include specification of acceptable injection repeatability, criteria for resolution between critical pairs, maximum allowable tailing factors, and a means of verifying that the requisite sensitivity is obtained. As recommended by Vander Heyden et al., system suitability limits are best set following robustness tests. 

The following system suitability parameters should be included in HPLC methods to evaluate and monitor performance. 

Additional System Suitability Parameters. Other parameters for system suitability testing can be considered (e.g., capacity factor, number of theoretical plates, etc.). 

As in any scientific document, one must provide a rationale for the parameters chosen and their effect on the overall success of the transfer. This includes an explanation for the system suitability parameters that have been established for the method. System suitability can be a powerful tool for troubleshooting method discrepancies in addition to being a test of the conformance of the system to a set of parameters before analysis. 

Figure 5.12. A summary report for system suitability testing documenting result i.d., precision, and other system suitability parameters (S/N ratio, tailing factors, plate count, and resolution). Note that means and precision of each table column can be automatically calculated.

Due to often limited sample size, it is an absolute must not to waste sample material by preparing it before the HPLC method is considered suitable for use. Problems encountered at this stage may take some time to diagnose and repair (see Chapter 10) and samples can and do degrade with time (see Chapter 6). System suitability parameters can usually be defined in two ways the system performance and the chromatographic suitability. 

All of the validation parameters above deal with method performance during the critical phases of validation and method review. Unfortunately, no matter how rigorous the validation protocol is for a method, validation cannot preclude or anticipate the effect of instrumentation that is not wofijing properly or analyst error. It is for this reason that an on-going method-specific test (or set of tests) is needed. This is the reasoning behind the use of system suitability parameters. 

System suitability refers to a unique set of performance specifications that is directly linked to a method. These specifications are not accuracy, precision, linearity, etc., which are measures of method performance and are used to support product release. These data are generated after the analysis set is complete. Conversely, a system suitability parameter directly ties the immediate performance of the method for a specific portion of an analytical sequence. Some parameters that are commonly used as system suitability parameters include theoretical plates aaA/oc peak symmetry for the analyte peak Ifl), resolution or a for multiple analyte peaks in a determination), or check sample results (analysis of a previously analyzed sample). 

This book serves two separate and important functions for the chromatographen practical and operational. The first duee chapters deal with the opoational aspects of solvents. They contain information regarding solvents and solvent classes, method optimization techniques, and the definition and use of method validation proto-cols/system suitability parameters. These chapters describe solvents from a practical use-oriented point of view. Here the physical and chemical properties of numerous solvents are discussed with respect to their impact on the chromatographic system. A clear understanding of the implications presented by these properties will save the chromatographer considerable time and effort. 

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