Calibration procedures Program

The evaluation of the various XRF measurements will be discussed for different effects in EDXRS the spectra evaluation is perfonned by different programs with varying assumptions, partially different mass attenuation coefficients are used, the calibration procedures are principally different (e.g., thin foils with given thickness, or, infinitely thick samples), measurement under atmospheric pressure or in vacuum, secondary excitation (enhancement) mainly of Al by Si radiation. 

The components of a quality assurance program are designed to serve the two functions just mentioned—control and assessment. Quality control operations are defined by operational procedures, specifications, calibration procedures, and standards and contain the following components ... 

To perform an external or internal standard calibration procedure and to calculate sample results, the laboratory conducts a series of calculations. Although these calculations are computerized at a modern laboratory, professional judgment and experience of the analyst are critical in the selection of the appropriate calibration model and for correct programming of the data acquisition system that collects the data and performs the calculations. 

Design Qualification (DQ) is the first validation element of a new facility system or equipment, where adherence to the user s specifications and to GMP rules is demonstrated. Installation Qualification (IQ) follows with the verification of adequacy of the area, installation of equipment pipelines, utilities, instrumentation, and conformity of the material used to the project specifications. At the Operational Qualification (OQ) phase, carried out after installation of all equipment, it is verified whether the system, when in operation, complies with the acceptance criteria defined in the validation plan. Once the OQ phase is successfully finalized it is possible to proceed with the calibration procedures, operation and cleaning, operator training, and preventive maintenance program. After IQ and OQ are concluded, it is time for the Performance Qualification (PQ), with the aim of verifying that what was designed, built, and operated results in a product that meets the expected specifications. Production and QC personnel are specially trained for these assessments. The tests can be done with the product of interest or a placebo, and are related to all operations, from raw material reception to product release (EC, 2001). 

System calibration refers to the periodic operational qualification of the HPLC, typically every 6 to 12 months in most regulated laboratories. This calibration procedure is usually coordinated with an annual preventative maintenance (PM) program and is performed immediately after PM. A calibration sticker is placed on the instrument to indicate its calibration status and readiness for GMP work. The reader is referred to the principles and strategies behind HPLC calibration criteria published elsewhere.8 A summary of the calibration procedures and acceptance criteria, including additional procedures recommended for initial operational qualification, is listed in Table 9.3. 

Similar results were presented in [9]. In uninhibited CO2 environments it was observed that in general the P-factors were of the order of 15-20 mV for pH-statted test procedures. However, as soon as a corrosion product layer formed, the factors increased. It is for this reason that the original PAIR -meter by Petrolite pre-programmed a P-factor of 37 mV based on extensive laboratory and field calibrations [45]. Newer commercial instruments allow the user to dial in a value for the p-factor. However, this presupposes that the Tafel slopes are known, and since these cannot be reha-bly determined as indicated above, the user is still left to guess, unless calibration procedures are in place, such as weight loss determinations or iron counts. 

In the step from the raw experimental data to data that can be treated by conventional computer programs, transformations are often necessary. For titrations, the raw data are EMF values as a function of titrant added (volume changes may be more or less important). These would typically be transformed to log[H ] (or pH), total acid concentration, and dilution factors (e.g., for FITEQL). With LAKE [32], raw data can be treated directly. An input file or the code itself must, in such a case, provide all the information necessary for the calculation of equilibria (e.g., LAKE must perform the transformations to obtain concentrations from the raw data). For the majority of eodes, however, pH or log[H ] as a function of titrant added is required. EMF values must be transformed to pH or log[H" ] using the apphed calibration procedures. Here, the calibration and, sometimes, assumptions in the data treatment may be important. Calibration can be performed on the eoneentration or on the activity scale. The concentration scale has the advantage that, a priori, no assumptions about activity coefficients are necessary the disadvantage is that such an approach is limited to one ionic medium (the constant ionic medium approach), although in work on suspensions, the variation of the ionic medium certainly is of importance. The activity scale requires assumptions concerning the treatment of activity coefficients it must be realized that sueh assumptions must lead to self-consistency between the finally presented experimental data and the model calculations. 

Chambers used in the formal stability program must go through qualification and calibration procedures. The chambers should be qualified at the time of purchase to assure a proper installation, a process denoted installation qualification (IQ). This procedure documents that the chamber has been installed properly and that it meets the manufacturer s specifications. The chamber should also be... 

Note S—The instrument manufacturer provides an alternative calibration procedure using two reference points, zero pressure (<0.1 kPa) and the ambient barometric pressure. However, since this procure was not included in the interlaboratory program, the precision and bias can be affected by its use. 

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