Methods of Calibration

Direct calibration of methods and instrumentation i.e. ensuring that an analytical device is giving a correct reading. For some types of direct soUd sample analysis, sample results can be calibrated using several CRMs with suitable matrices (Kur-furst 1998) see also Section 4.4. 

A method performance study may also be used to evaluate the performance of a new analytical method or an automated form of an already existing method [1,19]. Under certain circumstances a method performance study may be called intercalibration study. This should only concern exercises where the calibration of methods is investigated e.g. studies on calibrants, calibrant solutions, calibration procedures etc. Such studies are more frequent in physical measurements for metrological purposes. 

The F + H2 - FH + FI reaction has received considerable attention from theory as it is an excellent system for the calibration of methods there is experimental data for the reaction rate as a function of temperature, information on product vibrational energy distribution, and the reaction thresholds are known for both H2 and In Table IX, several... 

The elaborated method of applying elements for calibration of devices composed of the body with a nartensite structure, with elements made of austenite steel placed in it, allows to ensure calibration repeatability,... 

The calibration of the SPATE system can be carried out by two different methods ... 

Flow measurements using tracers are performed in all piping systems carrying oil, gas or water including separators, compressors, injector systems, and flares. Calibration of elsewhere difficult accessible flow meters is regularly performed by the tracer methods, which are based on international standards. Tracer flow measurements are also well suited for special purposes... 

In situ control and calibration of flare and other gas metering systems is performed by gaseous tracers using the transit time method without affecting the normal production. Details about methodology are given in / /. 

Fuzzy logic and fuzzy set theory are applied to various problems in chemistry. The applications range from component identification and spectral Hbrary search to fuzzy pattern recognition or calibrations of analytical methods. 

Table II, 9, A.—Reference Substances for the Calibration of Thermometers BY THE Melting Point Method...

The most satisfactory and the most accurate method for the calibration of a thermometer is to compare it directly with short-scale thermometers, each of limited range, which have been standardised at the National Physical Laboratory.f The comparison should be made as far as possible under the same conditions as the thermometer is to be used. For experiments demanding the highest precision e.g., in research work), it is a good plan to have two similar sets of short-scale thermometers, one of which has been standardised at the N.P.L. the unstandardised set is... 

As explained in Section 2.13, the use of iz,-plots makes it possible to avoid the involvement of either n or when an alternative adsorptive is being used for evaluating the surface areas of a set of related solids. It is then no longer necessary to exclude the use of isotherms having a low value of c, consequently the method is applicable even if the isotherm of the alternative adsorptive is of Type III (cf. Chapter 5). Calibration of one sample by nitrogen or argon adsorption is still required. 

Description of Method. The amount of chlorpromazine in a pharmaceutical formulation is determined voltammetrically at a graphite working electrode in a nonstirred solution. Calibration is achieved using the method of standard additions. 

The U.S. Environmental Protection Agency publishes sets of Series Methods that describe procedures for detecting and estimating the quantity of environmentally hazardous substances. There are strict requirements for accuracy, reproducibility, and for calibration of mass spectrometers. 

The equations and methods for determining viscosity vary greatly with the type of instmment, but in many cases calculations may be greatly simplified by calibration of the viscometer with a standard fluid, the viscosity of which is known for the conditions involved. General procedures for calibration measurement are given in ASTM D2196. The constant thus obtained is used with stress and shear rate terms to determine viscosity by equation 25, where the stress term may be torque, load, or deflection, and the shear rate may be in rpm, revolutions per second (rps), or s F... 

Robustness of methods based on broad-on-nar row approach (one of narrow standar ds is used as broad standard for correction of calibration function) is higher but some disadvantages also are observed. 

In this work there is proposed approach which allows using broad standar ds for calibration and system suitability test. The approach is based on main principle of using of standards i.e. maximal closeness of tested sample and standar d. It has been shoved that the approach allows achieving essential improvement of robustness of method for determination of MWD of dextrans. 

If the one-point calibration in ambient air is not sufficient, the next best approach is to use the calibration box method.- The air state is created in a closed box made of nonhygroscopic material, like metal or plastic. A controlled state of humidity is maintained by exposing the air in the box to a liquid surface of a saturated salt solution. In practice, a dish containing the saturated water solution of a salt is placed on supports at the bottom of the box. The air in the box is circulated by means of a small fan. The box should be airtight and positioned in a constant temperature environment. The calibrated instruments are placed in the box. A dewpoint hygrometer can be used as a reference. A wide range of humidity can be created by using solutions of different salts. Table 12.5 shows a few examples of equilibrium humidities achieved with different salt solutions. 

The standard requires the supplier to define the process employed for the calibration of inspection, measuring, and test equipment, including details of equipment type, unique identification, location, frequency of checks, check method, acceptance criteria, and the action to be taken when results are unsatisfactory. 

Whilst an instrumental method is ideally suited to the performance of a large number of routine determinations, for an occasional, non-routine, analysis it is often simpler to use a classical method than to go to the trouble of preparing requisite standards and carrying out the calibration of an instrument. 

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