Quality control calibration

Quality control Calibration, (certified) reference materials... 

In contrast, ACR emphasizes the quality control, calibration of the equipment, and technology used in the procedures, and accordingly has developed three modules - module 1 for oncology, module 2 for brain, and module 3 for heart. A PET center must apply for all modules that are performed at the facility. For accreditation, the facility is required to submit information on the quality control and quality assurance program, data collection, reporting, radiopharmaceuticals procedures, and laboratory safety, along with chnical and approved phantom images. So, all equipment in a PET center is required to be calibrated and tested for accurate functionahty for accreditation by ACR. 

Quality control, calibration Data archiving Security of data... 

Quality control elements required by the instrumental analyzer method include analyzer calibration error ( 2 percent of instrument span allowed) verifying the absence of bias introduced by the sampling system (less than 5 percent of span for zero and upscale cah-bration gases) and verification of zero and calibration drift over the test period (less than 3 percent of span of the period of each rim). 

A solvent free, fast and environmentally friendly near infrared-based methodology was developed for the determination and quality control of 11 pesticides in commercially available formulations. This methodology was based on the direct measurement of the diffuse reflectance spectra of solid samples inside glass vials and a multivariate calibration model to determine the active principle concentration in agrochemicals. The proposed PLS model was made using 11 known commercial and 22 doped samples (11 under and 11 over dosed) for calibration and 22 different formulations as the validation set. For Buprofezin, Chlorsulfuron, Cyromazine, Daminozide, Diuron and Iprodione determination, the information in the spectral range between 1618 and 2630 nm of the reflectance spectra was employed. On the other hand, for Bensulfuron, Fenoxycarb, Metalaxyl, Procymidone and Tricyclazole determination, the first order derivative spectra in the range between 1618 and 2630 nm was used. In both cases, a linear remove correction was applied. Mean accuracy errors between 0.5 and 3.1% were obtained for the validation set. 

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 ... 

In addition to fulfilling the in-house requirements for quality control, state and local air monitoring networks which are collecting data for compliance purposes are required to have an external performance audit on an annual basis. Under this program, an independent organization supplies externally calibrated sources of air pollutant gases to be measured by the instrumentation undergoing audit. An audit report summarizes the performance of the instruments. If necessary, further action must be taken to eliminate any major discrepancies between the internal and external calibration results. 

Documentation Data volume includes all quality control forms, e.g., zero/span control charts and multipoint calibration results... 

Quality Assurance/Quality Control parameter and metrics to ensure data reproducibility, e.g. the establishment of calibrated RNA samples and reference datasets to objectively assess the performance of different microarray platforms (see also MAQC project http //w w w.nature. com/nbt/focus/maqc/). 

Research use of analytical results in the framework of a nonanalytical setting, such as a governmental investigation into the spread of pollution here, a strict protocol might exist for the collection of samples (number, locations, time, etc.) and the interpretation of results, as provided by various consultants (biologists, regulators, lawyers, statisticians, etc.) the analytical laboratory would only play the role of a black box that transforms chemistry into numbers in the perspective of the laboratory worker, calibration, validation, quality control, and interpolation are the foremost problems. Once the reliability and plausibility of the numbers is established, the statisticians take over. 

The quality control unit in a cosmetics company supervised the processing of the weekly batch of shampoo by determining, among other parameters, the viscosity and the dry residue. Control charts showed nothing spectacular. (See Fig. 4.10, top.) The cusum charts were just as uneventful, except for that displaying the dry residue (Fig. 4.10, middle and bottom) The change in trend in the middle of the chart was unmistakable. Since the analytical method was very simple and well-proven, no change in laboratory personnel had taken place in the period, and the calibration of the balances was done on a weekly basis, suspicions turned elsewhere. A first hypothesis,... 

Enzyme Reference Serums. Several companies sell lyophilized or stabilized reference serums for the calibration of instruments and for quality control. The label values given for the enzymatic activity of these serums should never be taken at face value, as at times they may be quite erroneous (19,33). Also, these values should only be used for the assay with which they were standardized, as interconversion of activity from one method to another for the same enzyme may often lead to marked errors. For instance, it is not recommended that alkaline phosphatase expressed in Bodansky units be multiplied by a factor to convert it to the units of the Ring-Armstrong method, or any other method for that matter. 

Permeability is another method for obtaining information about pcirticle diameters. If one packs a tube with a weight of powder exactly equal to its density, and applies a calibrated gas pressure through the tube, the pressure drop can be equated to an average particle size. The instrument based on this principle is called the "Fisher Sub-Sieve Sizer ". Only one value can be obtained but the method is fast and reproducible. The instrument itself is not expensive and the method can be applied to quality control problems of powders. Permeametry is usefiil in the particle range of 0.5 to 50 n. 

Valko et al. [37] developed a fast-gradient RP-HPLC method for the determination of a chromatographic hydrophobicity index (CHI). An octadecylsilane (ODS) column and 50 mM aqueous ammonium acetate (pH 7.4) mobile phase with acetonitrile as an organic modifier (0-100%) were used. The system calibration and quality control were performed periodically by measuring retention for 10 standards unionized at pH 7.4. The CHI could then be used as an independent measure of hydrophobicity. In addition, its correlation with linear free-energy parameters explained some molecular descriptors, including H-bond basicity/ acidity and dipolarity/polarizability. It is noted [27] that there are significant differences between CHI values and octanol-water log D values. 

P.C. Thijssen, S.M. Wolfrum, G. Kateman and H.C. Smit, A Kalman filter for calibration,eval-uation of unknown samples and quality control in drifting systems Part 1. Theory and simulations. Anal. Chim. Acta, 156 (1984) 87-101. 

ISO Guide 33 (1998) deals with other uses of RMs. It elaborates on various uses of RMs, excluding calibration, which is the subject of ISO Guide 32. In most cases, RMs are used as a quality control measure, i.e. to assess the performance of a measurement method. Most matrix RMs are produced with this purpose in mind. Other purposes of RMs are the maintenance of conventional scales, such as the octane number and the pH scale. ISO Guide 33 provides guidance on the proper use of RMs, and therefore it is together with ISO Guide 32 the most important document for users of CRMs. 

A further distinction is made between pure solutions and matrix-based RMs. The former are available for many organic and inorganic analytes, with certified concentrations, but their role in quality control and assessment is limited. They may be used for the preparation of calibration solutions for a particular measurement but more usually these materials represent the base for traceability, through secondary... 

Some of the intended categories of use of radioisotopic reference material have been reviewed recently by Fajgelj et al. (1999). They include assignment of property values, establishing the traceability of a measurement result, determining the uncertainty of a measurement result, calibration of an apparatus, assessment of a measurement method, use for recovery studies and use for quality control purposes. It should be noted however that, in general, natural matrix reference materials are not recommended for calibration purposes. This should preferably be done with pure chemical forms of the element labelled with the isotope of interest. Calibrated isotopic sources of this kind are available from a number of commercial suppliers and are not the subject of this review. 

Even inside the controlled conditions of a research laboratory, analyzing clean and standardized test samples PCR procedures requires careful quality control, taking into consideration differences in sample preparation, variation in pipetting, differences in reaction tube thickness, poor calibration or instability of the thermal cycler, and reagent quality. 

On most occasions CRMs are used as Quality Control materials, rather than as calibrations . As outlined above, this common application adds significantly to the user s uncertainty budget, since at a minimum it is necessary to consider at least two independent measurement events (Um). so increasing the combined uncertainty of the results. Again this process rapidly increases the combined uncertainty with increasing complexity of the analytical system and so the usefulness of a control analysis may be downgraded when a correct uncertainty budget is formulated. 

Finally, it is very difficult to keep standard solutions for monitoring or recalibration purposes. Control batches should be purged and kept with a dry, inert gas. As long as results are reproduced, the system is considered to be in calibration. The relatively long extraction times usually prohibit the use of these methods for quality control analysis applications in a plastics manufacturing plant. 

The underlying calibration procedure of a newly developed analytical method has to be examined by basic validation studies to determine the reliability of the method and its efficiency in comparison with traditional methods. In order to ensure long-term stability, it is necessary to perform revalidations, which can be combined with the use of quality control charts, over meaningful time periods. 

To understand the role of calibration and quality control in making analytical measurements. 

Uses may include the calibration of a measurement system, assessment of a measurement procedure, assigning values to other materials and quality control. 

Note (4) is very important as it highlights the fact that the reference material used for the method validation cannot be used again when the method is in routine use for calibration purposes. The same type of material can be used, but it needs to come from a different supplier. The same material cannot be used for calibration purposes and then as a quality control material. 

The development and characterization of Certified Reference Materials is an expensive process. Because of this, emphasis on the use of Certified Reference Materials is usually directed more towards the initial validation of a method it is rarely economical to use a reference material for routine quality control although it can be used to calibrate other, cheaper, secondary materials which can be used for routine quality control. 

There are two uses of chemical standards in chemical analysis. In the first place, they may be used to verify that an instrument works correctly on a day-to-day basis - this is sometimes called System Suitability checking. This type of test does not usually relate to specific samples and is therefore strictly quality assurance rather than quality control. Secondly, the chemical standards are used to calibrate the response of an instrument. The standard may be measured separately from the samples (external standardization) or as part of the samples (internal standardization). This was dealt with in Section 5.3.2. 

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