Repeatability injection, system suitability

Repeatability can be divided into two areas injection repeatability and analysis repeatability. Injection repeatability is measured by analyzing multiple injections of the same solution preparation. It is an indicator of the performance of the HPLC system under the specified conditions and at the time of the analyses. This information is included as part of the validation package and is also used during routine analysis in the form of a system suitability. During the validation the specification for % RSD will be set, which will determine the variation limit for the analysis. If the value is low... 

In addition to the ICH levels repeatability and intermediate precision, the system precision, i.e., repeated injections/determinations of a single sample solution (also referred to as injection repeatability or injection precision), provides valuable information. Evaluation of these data will help us to show that the chosen equipment is suitable for its intended use. Injection precision will also become part of the system suitability requirements of the method and an acceptance... 

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 column should be reassembled and reattached to the HPLC system. It should be allowed to reequiUbrate and an injection should be performed. The peak shape should be assessed and, if an improvement is apparent and the system suitability criteria are met, the column can be used for the analysis. Quite often it is necessary to repeat the slurry application several times in order to fill the void completely. This can be time consuming and in some instances the preferred option is to replace the column. 

System suitability checks should be performed before the first injection of the analytical batch and, for some methods, it is advisable to repeat this check when the analyses are completed. A detailed discussion of system suitability is given in Section 9.8.3, but the following description of a practical check procedure for LC-MS/MS systems has been found to be fit for purpose in many situations. 

Table 9.11 shows the effect of this concentration on the responses of the other pesticides. In every instance the peak height was increased while the peak area remained constant. All of the columns used for this study were aged by repeated sample injections, but had not deteriorated to the point where they would normally be replaced. No values are included in Table 9.11 where the chromatographic system was not suitable for the pesticide concerned. 

Capella-Peiro et al. (28) used a 3 full factorial design to optimize the capillary zone electrophoresis (CZE) separation of a group of seven antihistamines (brompheniramine, chlorpheniramine, cyproheptadine, diphenhydramine, doxylamine, hydroxyzine, and loratadine). In this case, critical parameters such as pH (a concentration of 20 mM phosphate was kept constant in all the experiments) and the applied voltage were studied to evaluate their effect on the resolution and efficiency. Maximum response was achieved at pH 2.0 and an applied voltage of 5 kV. After a repeatability study to check the precision of the electrophoretic method, as well as a suitable calibration, the usefulness of this optimized method was demonstrated through the determination of the listed histamines in pharmaceuticals, urine, and serum samples (recoveries were in agreement with the stated contents). Urine samples were diluted and directly injected in the CE system, while serum samples were previously extracted by means of a solid-phase extraction (SPE) procedure. 

The cheapest fluid temperature control can be carried out using circuit water. Of course, it is only suitable for hard temperature control. For this purpose, a water distribution system is provided in all parts of the injection moulding machines, to which the temperature control circuits of the mould can be connected. The cooling intensity is set by the water throughput using valves. So as to obtain values with a certain amount of repeatability, throughput gauges and thermometers (in the counterflow) are required in each circuit. 

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