Method development defining system suitability

Starting with validated software and instrument qualification a validated analytical method is developed using the qualified system. Finally, total validation is achieved by defining system suitability. The analytical chemist is mostly concerned with steps (Hi) and (iv), but he might be (rightly) suspicious regarding developments beyond his field of vision. 

System Suitability. Although method validation is performed once at the end of method development, system suitability tests are performed on a specific system periodically (usually daily) or prior to each batch during validation and sample analysis to determine the system performance (see Chapter 13). During method development or/and upon completion of the validation, system suitability data should be evaluated and used to define acceptance criteria to use before starting sample analysis. System suitability tests include (1) the reproducibility of retention time, (2) adequate sensitivity to quantify LLOQ (minimum detector response), (3) appropriate sensitivity to quantify ULOQ (within range of detector), and (4) chromatographic separation. 

The bond graph method defines the structure and constitutive equations of the system. Standard bond graph elements are used to build a model of the structure of the system. Suitable computer programs are available to generate the governing equations, and alternative methods have also been developed for deriving equivalent block diagrams, which can represent nonlinear systems. 

Relative retention time fRJ. The main practical disadvantage of using k to describe retention arises from the difficulties associated with the accurate measurement of The accurate measurement of t, requires correct choice of a reference compound that is neither retained by the column nor excluded from its pores. Problems with the accurate and reproducible measurement of k have led to the use of a retained compound for system suitability tests for liquid chromatography and related techniques when it has been checked that the column, mobile phase and equipment are performing identically to when the method being used was first developed. The relative retention time of a solute j may be defined by... 

The risk index defined in Equation 6.1 (see Section 6.2.1) is intended to provide a measure of the potential risk that arises from disposal of any waste that contains hazardous substances. In Section 6.3, the general definition of the risk index is elaborated and recommendations on suitable approaches to calculating the risk index for individual hazardous substances are presented. For purposes of developing a comprehensive and risk-based waste classification system, a simple method of calculating the risk from disposal of mixtures of hazardous substances is needed. The method must take into account that the allowable concentrations of particular hazardous substances in waste of a given class generally will be lower when multiple substances are present than when only a single substance is present. Such a method is presented and discussed in this Section. 

---