Calibration terminology

The corrections and calibration of filterFRET differ significantly for CCD microscopes and confocal microscopes. This is because in confocal experiments, channel sensitivities are adjusted at will by the experimenter, and because relative excitation intensities show intended-as well as unintended variations (adjustments and drift, respectively). Confocal filterFRET therefore requires frequent, if not in-line, recalibration however, if properly streamlined this should not take more than 15 min a day. It also slightly complicates the mathematical framework, as compared to CCD imaging filterFRET. We aimed to arrive at a comprehensive theory that is equally applicable to both imaging modes. We also proposed mathematical jargon that is a compromise between the widely differing terminologies used in the various publications on this topic. 

Note that some organizations may not use the terminology used in this book and may not distinguish between SOPs and WIs. Standard Operating Procedures provide details of how a series of operations are carried out. An example of a SOP would be the detailed instruction for carrying out a particular analytical method. Work Instructions give details of how a specific operation is carried out. What might be classed as a WI is how to operate a particular instrument, how to estimate measurement uncertainty or how to calibrate a piece of equipment. 

Calibration, in current Good Manufacturing Practices (GMP) terminology, refers to instrument qualification or performance verification... 

Calibration, in current Good Manufacturing Practices (cGMP) terminology, refers to instrument qualification or performance verification of the HPLC. Note that neither any internal instrumental adjustment nor detector response curve for quantitation is intended here as in the common usage of the terminology. In most pharmaceutical laboratories. 

The ISO/IEC 17025 standard (ISO/IEC 2005) has the title General requirements for the competence of testing and calibration laboratories and is the main standard to which analytical chemical laboratories are accredited. The word calibration in the title arises from the use of the standard to accredit bodies that calibrate instruments such as balances, electrical equipment, and utility meters. It must also be stressed that the standard is not written for analytical chemists, but for any measurement scientists. Therefore, the terminology tends to be general, and the emphasis is sometimes not clear for the chemist. However, the standard is wide ranging and covers a whole community of measurement scientists. 

Multivariate calibration can be used with any suitable multivariate data to model any property. However, the terminology used here associates instrumental responses with sample spectra and the property of interest with the analyte concentration since the bulk of this book deals with this type of data. 

Most chemometricians prefer inverse methods, but most traditional analytical chemistry texts introduce the classical approach to calibration. It is important to recognise that there are substantial differences in terminology in the literature, the most common problem being the distinction between V and y variables. In many areas of analytical chemistry, concentration is denoted by V, the response (such as a spectroscopic peak height) by y However, most workers in the area of multivariate calibration have first been introduced to regression methods via spectroscopy or chromatography whereby the experimental data matrix is denoted as 6X , and the concentrations or predicted variables by y In this paper we indicate the experimentally observed responses by V such as spectroscopic absorbances of chromatographic peak areas, but do not use 6y in order to avoid confusion. 

Regression techniques. Principal components are sometimes called abstract factors, and are primarily mathematical entities. In multivariate calibration the aim is to convert these to compound concentrations. PCR uses regression (sometimes called transformation or rotation) to convert PC scores onto concentrations. This process is often loosely called factor analysis, although terminology differs according to author and discipline. 

Relevant national standards are available covering particle size analysis by microscopy. BS 3406 Part 4 [11] is the British Standard guide to optical microscopy. The American standard ASTM E20 was discontinued in 1994 [12]. ASTM 175-82 [13] is a standard defining terminology for microscope related applications. ASTM E766-98 [14] is a standard practice for calibrating the magnification of an SEM. NF XI1-661 [15] is the French standard for optical microscopy. NF XI1-696 [16] covers... 

ASTM E175-82 (1995), Standard terminology of microscopy, 144 ASTM E766-98 (1998), Standard practice for calibrating the magnification of an scanning electron microscope, 144... 

In these circumstances, where routine kinetic measurements are uninformative and direct measurements of the product-forming steps difficult, comparative methods, involving competition between a calibrated and a non-calibrated reaction, come into their own. Experimentally, ratios of products from reaction cascades involving a key competition between a first-order and a second-order processes are measured as a function of trapping agent concentration. Relative rates are converted to absolute rates from the rate of the known reaction. The principle is much the same as the Jencks clock for carbenium ion lifetimes (see Section 3.2.1). However, in radical chemistry Newcomb prefers to restrict the term clock to a calibrated unimolecular reaction of a radical, but such restriction obscures the parallel with the Jencks clock, where the calibrated reaction is a bimolecular diffusional combination with and the unknown reaction a pseudounimolecular reaction of carbenium ion with solvent. Whatever the terminology, the practical usefulness of the method stems from the possibility of applying the same absolute rate data to all reactions of the same chemical type, as discussed in Section 7.1. 

In the field of calibration the concept of an interferent is very important.1 A useful terminology is as follows an analyte (sometimes also called analyte of interest) is a compound in the sample for which quantification is needed, and an interferent is another compound in the sample that gives a contribution to the instrumental response but for which quantification is not needed. For a zeroth order instrument an interferent makes calibration impossible. The traditional way of dealing with interferents in analytical chemistry is to pretreat the sample such that only the analyte contributes to the signal of the zeroth order instrument. Extraction, separation, and or selective reagents are often used for this purpose. 

The principles causing retention behaviour, separation variables, molecular weight calibration and associated terminology such as interparticle and intraparticle volume, selective permeation, fractionation range and molecular hydrodynamic radius are as for open column size exclusion (Chapter 4). 

El 142, Standard Terminology Relating to Thermophysical Properties E1952, Standard Test Method for Thermal Conductivity and Thermal Dif-fusivity by Modulated Temperature Differential Scanning Calorimeter E2069, Standard Test Method for Temperature Calibration on Cooling for Differential Scanning Calorimeters... 

The method of calibration equation selection developed by the NIRS Forage Network follows in an abbreviated form. Note that the terminology used is that of the Forage Network and it is not consistent with all NIR users or statisticians. Each term and abbreviation will soon be standardized by ASTM Task Group on NIR E-13.03.03. For each constituent, the standard error of calibration (SEC) and coefficient of determination (R ) for each calibration equation are important criteria for decision making with respect to equation selection. As wavelength (independent terms) are added to the equation, SEC will decrease and will increase. 

Although calibrating or classifying spectra are merely two different applications of the mathemati-cal/statistical technique of regression, historically they have evolved independently, with different goals and requirements. Whenever possible attempts will be made to connect the two by drawing attention to common concepts and methods that only differ in their terminology and emphasis. Occasionally, for the sake of simplicity in presentation, discussion will cover certain aspects and peculiarities of the two disciplines separately. 

Documentary standards are now available to guide AES and XPS users on terminology, specimen handhng procedures, calibrations and performance tests of instruments, and many aspects of data acquisition and analysis (Tables 3.2.3.1 and 3.2.3.2). Additional recommendations for XPS have been published [132-134]. Nevertheless, a recent survey has identified many additional needs for documentary standards, reference materials, and reference data to facilitate AES and XPS analyses in the future [121]. 

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