Calibration and Standards

Modem techniques can be used to obtain highly reproducible standards for calibration of analytical instruments. One technique developed by NIST scientists is based on deposition of a controlled amount of analyte using a dot matrix printer that, instead of using printing ink, injects a solution of the analyte, as has been done for explosives, to mention just one example. This technique cannot be used for 

Reduced Mobility of Several Common Illicit Drugs and Medications that Can Be Abused (from Ion Mobility Spectrometry, 2nd edition) 

Reduced Mobility of Several Common Illicit Drugs and 

Source DeTulleo-Smith, A.M., Methamphetamine vs. nicotine detection on the Bairinger ion mobility spectrometer, IMS meeting, Jackson Hole, WY, August 20-22, 1996 Lawrence, A.H., Detection of drug residues on the hands of subjects by surface sampling and ion mobility spectrometry, Forens. ScL bit. 1987,34, 73S3. 

the drift gas, ionization source flow, and the sample vapors were carried by air wire, insertion of a metal wire with absorbed vapors or solution (sol). 

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Campbell (6) was perhaps the first to investigate the relationship between tenderometer values for raw peas and the texture characteristics of collateral samples after freezing and cooking. A high degree of correlation was observed. The investigations of Nielsen and co-workers (31) indicate the usefulness of the instrument for estimation of maturity in peas intended for freezing preservation. In order to secure consistent and reproducible results, the instrument requires standardization and calibration, and the measurements must be made under standardized conditions of temperature and interval after harvest. 

In conclusion, one must insist on the importance of the main metrological characteristic, the traceabilility (generally of a result), ensuring a clear (unbroken) relationship between the final result and the complete measurement scheme by using appropriate procedures, standards and calibrated equipment. However, for chemical metrology and particularly for on-site measurement, some adaptations are needed for a wider meaning of traceability [66]. 

The ability to make analytical measurements depends intimately on the availability of well-defined standards and calibrants. Many measurements of analytes in seawater (such as dissolved organic carbon and dissolved organic nitrogen) cannot be compared among laboratories because of the lack of appropriate reference materials and blanks for instrument calibration and testing. Intercomparison exercises are critical (NRC, 1993, p. 75). 

Standardization The instrument response function can vary from analyzer to analyzer. If calibration transfer is to be achieved across all instrument platforms it is important that the instrument function is characterized, and preferably standardized [31]. Also, at times it is necessary to perform a local calibration while the analyzer is still on-line. In order to handle this, it is beneficial to consider an on-board calibration/standardization, integrated into the sample conditioning system. Most commercial NIR analyzers require some form of standardization and calibration transfer. Similarly, modem FTIR systems include some form of instrument standardization, usually based on an internal calibrant. This attribute is becoming an important feature for regulatory controlled analyses, where a proper audit trail has to be established, including instrument calibration. 

J.S. Shenk and M.O. Westerhaus, New standardization and calibration procedures for NIRS analytical systems. Crop Sci. 31, 1694-1696 (1991). 

Significant changes in the facihties other than those currently reported must be closely examined. Any equipment used in the specific study must be examined to determine if it was standardized and calibrated prior to, during, and after use in connection with the study. It must be also determined—if at the time of the study there was equipment malfunction—the impact of the malfunction on the study and the remedial action taken. 

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. 

Research and Development Needed, 74 Standards and Calibration, 75 Resources for Instrument Development, 75 The Role of Academic Scientists, 78... 

The methods outlined below include protocols for direct and indirect immunofluorescence staining, that can be adapted easily for the cell type of interest as indicated in the relevant notes. The principal approaches to flow cytometric analysis, standardization and calibration are then given, followed by two more detailed protocols illustrating quantitation using direct immunofluorescence, and a competitive binding assay, which demonstrates the application of linear amplification of fluorescence. 

Fay, L.B., Metairon, S., and Blank, I. 2000. Stable isotope dilution assay mass spectometry in flavour research Internal standard and calibration issues. In Frontiers of Flavour Science (P. Schieberle and K.-H. Engel, Eds.) Deutsche For-schungsanstalt ftlr Lebensmittelchemie, Garching, Germany. 

As a result of the introduction of cytometers into the hospital setting, three aspects of clinical practice have led to some general reassessment of the nature of flow analysis. First, clinical laboratories are, because of the import of their results, overwhelmingly concerned with so-called quality control. This concern has forced all cyto-metrists to become more aware of the standardization and calibration... 

While the establishment and implementation of national traceability systems is left to the countries and their legislation, the mutual recognition of these national systems calls for an international mechanism, at least if worldwide mutual recognition is aimed at. The MRA of the Meter Convention for national measurement standards and calibration and measurement certificates issued by NMIs [2] can be expected to at least provide for one important aspect of the task, namely the establishment of international equivalence at the national standards level. Together with the success of the work currently carried out by the International Laboratory Accreditation Cooperation (ILAC) for the harmonization of national laboratory accreditation schemes, the MRA will be the key to comparability and hence to ac-... 

The development of gas standards and calibration techniques for measurements of vehicle, aircraft and industrial emissions, natural gas, occupational exposure and air quality... 

Wadhwa M, Thorpe R. Standardization and calibration of cytokine immunoassays meeting report and recommendations. Cytokine (1997) 9 791-793. 

Feam, T., Standardization and calibration transfer for near infrared instruments a review, J. Near Infrared Spectrosc., 9, 229-244, 2001. 

Once the standardized and calibrated direct chemiluminescence quantum yield (0 ) has been acquired experimentally, the singlet excitation yield (0 ) can be calculated for the chemienergized process from Eq. 35. However, as already stated, this requires that the fluorescence quantum yield (0 ) be known under the same experimental conditions at which 0 was determined. This is not always the case... 

In general, quantitative analyses are carried out as usual, using internal or external standards and calibration curves. Detection limits can be achieved in the lower picogram range dependent on the selected derivatization procedure. 

An offline analytical HPLC method with small injection volumes can be used to confirm the composition of cuts collected from a preparative run. Ideally, an analytical HPLC method provides an acceptable separation of the mixture components, displays peaks that can be assigned to known components, and gives a detector response that is a linear function of analyte concentration. Using isolated standards and calibrating the analytical detector for the concentration of each component is a good way to know the mass of each component eluting from a chromatography column, when such standards are available. 

The control of analytical variables, which includes analytical methodology, standardization and calibration procedures, documentation of analytical protocols and procedures, and the monitoring of critical equipment and materials. 

The quality of the calibrators and the calibration procedure used are major factors in determining the reliability of the analytical values obtained with a procedure. To appreciate the problems in standardization and calibration, knowledge of the overall structure of an accuracy-based measurement system is necessary. Uriano and Cali and Tietz have defined a hierarchy of analytical methods and reference materials that shows the relationship between reference materials and analytical methods of different quality. Figure 19-7 illustrates how "field methods are related to "reference methods by secondary reference materials and how reference methods are related to definitive methods by primary reference materials. ... 

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