Calibration of instruments

This procedure describes conditions pertaining to an adequate and organized calibration system of measuring devices. 

The calibration manager is responsible for establishing an adequate and organized calibration program. Supervision of the whole program should be done by the quality assurance manager. 

Purchase and control measuring equipment and reference material necessary for internal calibration certification of calibrated instruments. Label them with the date when last calibrated and also date when the next calibration is due. Write a calibration report and, if necessary, an incident report or a calibration variance report. 

The reference standards used for calibration of instruments should be checked for accuracy annually by an authorized measuring institution (e.g.. Office of Weights and Measures or Bureau of Standards). The reference standard employed should have an uncertainty of measurement which is 1/10 to 1/5 the uncertainty required in the measurement equipment. 

The uncertainties of all equipment used in the calibration procedure and the method of combining them should be shown on the calibration certificate. 

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Requirements for standards used In macro- and microspectrofluorometry differ, depending on whether they are used for Instrument calibration, standardization, or assessment of method accuracy. Specific examples are given of standards for quantum yield, number of quanta, and decay time, and for calibration of Instrument parameters. Including wavelength, spectral responslvlty (determining correction factors for luminescence spectra), stability, and linearity. Differences In requirements for macro- and micro-standards are considered, and specific materials used for each are compared. Pure compounds and matrix-matched standards are listed for standardization and assessment of method accuracy, and existing Standard Reference Materials are discussed. 

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. 

These reference materials are also suitable for calibration of instruments for isotopic measurements, calibration and evaluation of isotopic measurement procedures, development of isotopic measurement methods, and nuclear material accountability measurements. Many of these IRMM materials are, in fact, concerned with the last of these applications, i.e. in the area of nuclear material accountability. Some of them have been examined by a nuclear experts committee and certified as EC-NRMs (European Community - Nuclear Reference Materials). 

Suitable calibration of instruments used is a fundamental necessity, and it is rarely performed in an appropriate way. Most often, linear calibration functions are regarded... 

Errors in density result from errors in temperature measurement or control calibration of instruments transfer, handling and weighing of samples and impurities in the samples. At temperatures well below the critical temperature and near room temperature, standard techniques easily achieve accuracies of +0.05%. For the compounds in this compilation, that level corresponds to about +0.4 kg m"3. Under these conditions, errors in temperature are not very significant. This level of accuracy only requires... 

Calibration of Instruments, Apparatus and Applying Necessary Corections... 

Calibration of instruments and apparatus (if) Parallel control determination (// / ) Blank determination... 

Methods of measuring the components of photochemical smog are reviewed in Chapter 6. There have been significant advances in the calibration of instruments for monitoring ozone in ambient air. A method based on the absorption of ultraviolet radiation at 254 nm has been adopted by California for the calibration of air monitoring instruments. The method is based on the use of a commercially available instrument that measures ultraviolet absorption as a transfer standard in the calibration process. 

For the most reliable results, chamber environment should be monitored continuously with instruments and techniques equivalent to those used in ambient-air monitoring networks (see Chapter 6). Calibration of instruments should follow recommendations by appropriate agencies and be checked by cross comparisons with those in other analytic laboratories. 

Another approach to a source of vapors to calibration of instruments, and similar to that described above, was that of Davies et al. [67] who used a computer-controlled pulsed vapor generator with TNT, RDX, and PETN. The explosive solid was coated on quartz beads, which were then packed into a stainless steel tube. The tube was coiled and placed into a temperature-controlled chamber. Ultrapure air was passed through the coil at temperature and vapors of explosives were vented from the coil at rates or concentrations governed by coil temperature, airflow rate, and pulse width. Calibrations could reach the picogram to nanogram range when an IMS analyzer was used as the calibrating instrument. 

Absorbed dose is a fundamental and basic physical quantity which can be used in all fields where ionizing radiations are used. It is directly related to the physical, chemical, and biological effects produced by the irradiation. The concept of absorbed dose thus has broad applications and is indeed widely used. Metrological institutions provide standards and calibration of instruments in terms of absorbed dose. 

Calibration of instruments, analytical/microbiological test methods, and qualification runs... 

In the United States GMP regulations [7] issues related to laboratory controls are covered in Subpart I, which consists of regulations 211.160,211.165,211.166,211.167, 211.170, 211.173, and 211.176. The contents of Subpart I is presented in Table 24. Regulation 211.160 states the requirements for the establishment of laboratory controls such as specifications, standards, sampling plans, and test procedures. Furthermore, it covers the requirements stated for the calibration of instruments, apparatus, gauges, and recording devices. Regulation 211.165 states the require-... 

The calibration of instruments, apparatus, gauges, and recording devices at suitable intervals in accordance with an established written program containing specific directions, schedules, limits for accuracy and precision, and provisions for remedial action in the event accuracy and/or precision limits are not met. Instruments, apparatus, gauges, and recording devices not meeting established specifications shall not be used. 

The cGMP requirements dictate that the calibration of instruments should be performed at suitable intervals in accordance with an established written program. Instruments not meeting established specifications must not be used. Each instrument should have a calibration sticker with information related to the status of the system, when the calibration was performed, who did the calibration, and the next calibration date. A systematic program is required to maintain the instruments in a state of calibration. The following points should be considered when setting up an instrument calibration and maintenance program. 

In contrast, the ISO Guide 25 approach (updated in 1999 to ISO Guide 17025), as expanded in ref. 14 heavily focuses on good analytical practices and adequate calibration of instruments with nationally or internationally traceable standards wherever possible. 

In addition to inspection and calibration of instrumentation carried out as part of an SAT, the need for recalibration of critical instruments prior to IQ, OQ, and PQ should be reviewed and the decision documented in the respective qualification report. All site calibration activity should be conducted in accordance with quality standards and the respective engineering procedures. Any remedial work should be undertaken under document control, and where necessary, evaluated under change control. 

Bro, R. and Ridder, C. (2002) Notes on Calibration of Instruments (Spectral Transfer), http // www.models.kvl.dk/users/rasmus/presentations/calibrationtransfer/calibrationtransfer.pdf. 

The calibration of instruments used for organic compound analyses is a particularly lengthy procedure due to the large number of target analytes that are analyzed simultaneously. For example, laboratories analyze a minimum of 55 chemicals in EPA Method 8260 and a minimum of 75 chemicals in EPA Method 8270. (These numbers may be as high as 100 for either method). Even with the help of modern computers, a calibration procedure of this enormous scope may easily take 6-8 hours or even longer in some circumstances. Fortunately for the laboratories, once... 

RMs Considering the limitations of available primary methods, emphasis is placed by the CCQM on the elaboration of synthetic RMs derived from pure materials. These would then be used for calibration of instruments and hence, could help in the metrological step of analytical procedures. As appears from the cited examples, such RMs are hardly suitable as reference samples in many applications of analytical chemistry. 

Multi-component hydrocarbon standards to provide accurate calibration of instruments (generally gas chromatographs) used to monitor the concentrations of a wide range of volatile organic hydrocarbon compounds (VOCs) in ambient air. These standards currently contain 30 different hydrocarbon species that are important to photochemical ozone formation, with concentrations ranging down to a few parts per billion by molar value. They are disseminated widely in the United Kingdom and the rest of Europe as calibration standards, and as test mixtures for assessment of the quality of international ambient hydrocarbon measurements (often under the auspices of the European Commission - EC). 

In their regular day to day practice, field laboratories use commercial reagents or prepare in-house solutions for the calibration of instruments, and they rely on purity assessment of producers. For method validation and even measurement uncertainty, field labs regularly participate in proficiency testing schemes. In such inter-laboratory comparisons, the reference value is usually obtained as the arithmetic mean of results of participants. 

Procedures—An underutilized practice in validation is the SOP, whereby repetitive activities can be defined. The use of SOPs increases reproducibility of execution and allows for further brevity in both protocols and reports. Procedures make everyone who is involved with the project substantially more efficient, and should be employed wherever possible. Practices such as calibration of instrumentation, biological indicator placement, sampling of validation batches, and microbial testing are clear candidates for inclusion in SOPs. Among the more innovative uses is the inclusion of standardized validation acceptance criteria for similar products. 

Note Species name, phylum or division, common name, and concentration of total MAAs ([MAA], in nmol mg-1 protein) are indicated. Notes describe whether samples are from a whole organism or specific tissues, and value indicates if data are from a single measurement, a maximum value from several samples (max), or a maximum mean value (mean) reported. See text Section II.A.6 for an explanation of how rankings were determined. The comparison of values from different research laboratories may be somewhat problematic as there are currently no commercial standards available for MAAs and calibration of instruments is achieved by a variety of means. 

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