Standardization reference standards

In other words, the purity of analyte and IS reference standards determines the maximum possible concentration span. Sometimes, it is impossible to simultaneously satisfy both (1) and (2), i.e C >C In this case, either calibration range needs to be adjusted (narrowed) or analyte or internal standard reference standards of higher purity must be used. 

Reference Standards. Reference standards for TLC, GC, and MS were obtained as follows. Pure abietic acid (mp 172-173 °C) was used as received. Dehydroabietic acid was prepared by oxidation of abietic acid with selenium dioxide to hydroxy abietic acid and subsequent dehydration with glacial acetic acid (11). 7-Ketodehydroabietic acid was prepared by oxidation of dehydroabietic acid with potassium permanganate and isolation of the product by way of the Girard reagent T (12). Pyroabietic acid (a mixture of dehydro- and dihydroabietic acids) was prepared by heating abietic acid with 10% palladium on charcoal to 250 °C for 1 h (13). 

Unfortunately this infrastructure of working standards, reference standards and primary standards does not exist for analytical measurements. Although the Comity International des Poids et Me-sures (CIPM) have started work on the development of such an infrastructure, it will take several years, if not decades, to develop. Thus the VAM programme is designed to meet the objectives of the NMS, i.e. to enable organisations to make measurements that are fit for their intended purpose, by ... 

In addition to commercial producers, the National Institute of Standards and Technology supplies primary standard chemicals. NIST Special Publication 260 catalogs standard reference materials. (See http //ts.nist.gov/ts/htdocs/23Q/232/232.htm for information on the SRM program and lists of reference standards.) Reference standards are complex materials, such as alloys that have been carefully analyzed for the ingredients and are used to check or calibrate an analytical procedure. 

Reference standards may be available in the form of official reference standards. Reference standards prepared by the producer should be tested, released, and then stored in the same way as official standards. They should be kept under the responsibility of a designated person in a secure area. 

Two kinds of information reveal if there are environmental hazards. In most cases exposures require measurements with suitable instmments. In addition, there is a need for reference standards. Reference standards state what level of exposure is dangerous. Effective procedures determine if a hazard exists. 

From the three items of information it is possible to find out if an exposure is hazardous. For some agents it is necessary to complete a computation to determine the hazard for an exposure. To determine if there is a hazard, it is necessary to compare the acmal exposure to a reference standard. Reference standards come from studies of illnesses and related exposures. In some cases scientific specialists recommend allowable exposures. In other cases, government agencies set exposure limits. Not all reference standards agree on allowable exposures and exposure limits. Over time, additional studies may lower recommended exposures. Government agencies in different countries will not agree on allowable exposures. The philosophies that influence reference standards may differ. 

Standard reference standard hydrogen electrode (SFIE = 0.0 V)... 

In a binary liquid solution containing one noncondensable and one condensable component, it is customary to refer to the first as the solute and to the second as the solvent. Equation (13) is used for the normalization of the solvent s activity coefficient but Equation (14) is used for the solute. Since the normalizations for the two components are not the same, they are said to follow the unsymmetric convention. The standard-state fugacity of the solvent is the fugacity of the pure liquid. The standard-state fugacity of the solute is Henry s constant. 

We find that the standard-state fugacity fV is the fugacity of pure liquid i at the temperature of the solution and at the reference pressure P. ... 

Enthalpies are referred to the ideal vapor. The enthalpy of the real vapor is found from zero-pressure heat capacities and from the virial equation of state for non-associated species or, for vapors containing highly dimerized vapors (e.g. organic acids), from the chemical theory of vapor imperfections, as discussed in Chapter 3. For pure components, liquid-phase enthalpies (relative to the ideal vapor) are found from differentiation of the zero-pressure standard-state fugacities these, in turn, are determined from vapor-pressure data, from vapor-phase corrections and liquid-phase densities. If good experimental data are used to determine the standard-state fugacity, the derivative gives enthalpies of liquids to nearly the same precision as that obtained with calorimetric data, and provides reliable heats of vaporization. 

The computer subroutines for calculation of vapor-phase and liquid-phase fugacity (activity) coefficients, reference fugac-ities, and molar enthalpies, as well as vapor-liquid and liquid-liquid equilibrium ratios, are described and listed in this Appendix. These are source routines written in American National Standard FORTRAN (FORTRAN IV), ANSI X3.9-1978, and, as such, should be compatible with most computer systems with FORTRAN IV compilers. Approximate storage requirements and CDC 6400 execution times for these subroutines are given in Appendix J. 

PURE calculates pure liquid standard-state fugacities at zero pressure, pure-component saturated liquid molar volume (cm /mole), and pure-component liquid standard-state fugacities at system pressure. Pure-component hypothetical liquid reference fugacities are calculated for noncondensable components. Liquid molar volumes for noncondensable components are taken as zero. 

Thermodynamic quantities which refer to the standard state are denoted by superscript zeros ( ), e.g. AG/, AH/, AS/, the subscript denoting the temperature T of the system. 

All these methods begin with combustion of the sample resulting in the sulfur being oxidized to SO2 and SO3. Table 2.3 summarizes the different analytical methods with references to the corresponding standards. 

T being the boiling temperature (Kelvin) and S being tbe standard specific gravity (15.6°C/15.6°C). Refer to Chapter 4. 

The exact calculation of the index is given in the ASTM D 2270 standard. The kinematic viscosity at 40°C (f/) of an oil whose viscosity index (V7) is being calculated is compared with those of two reference oils for which the viscosity indices are 0 and 100 respectively, and which have at 100°C the same kinematic viscosity as that of the oil being examined )... 

The Reid vapor pressure characterizes the light petroleum products it is measured by a standard test (refer to Chapter 7) which can be easily simulated. 

Measurement of octane numbers is carried out using a reference motor called CFR (Cooperative Fuel Research), referring to a series of studies conducted in 1928 in the United States in order to standardize the methods for characterizing motor fuels. 

Ductility is the elongation, at the moment of failure, of a standard bitumen briquette that is stretched at a predetermined speed and temperature. References are the NF T 66-006, ASTM D 113, IP 32 methods. 

The standards for tests, which are cited in reference to the standards for characteristics. In order for a client and his supplier to compare their results during a commercial transaction, it is important that their laboratories rigorously follow the same operating procedures. The procedures are thus precisely defined in the standards. 

In the United Kingdom, the IP (Institute of Petroleum), for which most of the texts, but not all, are taken as British standards with the reference, BS (British Standard). 

These specifications and characteristics are defined with references to standard test methods which the different parties to a contract should conduct for quality control. The tables that follow show specifically the standards that are applicable in France, but a more general table in Appendix 2 shows the main test methods commonly referenced in specifications. 

A specification or standard for product characteristics is valid only if it is matched with references to well defined and recognized test methods, such that quality control tests conducted by the parties involved —client and supplier, for example— are comparable even if they are performed at different locations. 

Color NF T 60-104 ISO 2049 ASTM D 1500 Comparison with colored glass standard references... 

The most important use of the real gas law is to calculate the volume which a subsurface quantity of gas will occupy at surface conditions, since when gas sales contracts are negotiated and gas is subsequently sold it is referred to in volumes at standard conditions of temperature (Tsc) and pressure (Psc). 

The Supplement B (reference) contains a description of the process to render an automatic construction of mathematical models with the application of electronic computer. The research work of the Institute of the applied mathematics of The Academy of Sciences ( Ukraine) was assumed as a basis for the Supplement. The prepared mathematical model provides the possibility to spare strength and to save money, usually spent for the development of the mathematical models of each separate enterprise. The model provides the possibility to execute the works standard forms and records for the non-destructive inspection in complete correspondence with the requirements of the Standard. 

The sweeping test, following X, Y and Z axes, on the aluminum plate containing four standard defects and the processing software comparing between the impedance variation of the sane reference and the sample to be controlled allow the reconstitution of an image of the piece. 

The film density is chosen to be D-D = 2.0 as the values for Oj, G and G/Oj, in EN 584-1 refer to this density. For the value of the gradient G the condition given by the value G/op of the standard has to be considered, that means the value of the gradient has mostly to be greater than the minimum gradient of the film system class. 

The physics of X-ray refraction are analogous to the well known refraction of light by optical lenses and prisms, governed by Snell s law. The special feature is the deflection at very small angles of few minutes of arc, as the refractive index of X-rays in matter is nearly one. Due to the density differences at inner surfaces most of the incident X-rays are deflected [1]. As the scattered intensity of refraction is proportional to the specific surface of a sample, a reference standard gives a quantitative measure for analytical determinations. 

The removing penetrant test is performed on sanded and cracked reference block defined in standard NFA 09.520 ( see figure 1, annex 1) and permits the evaluation of the washability of penetrants. 

The computer also can leam from a defect-free test piece by rutming such a piece in a readmode. For example, if a drilled hole for lubrication purposes is present at the same location on all parts, the computer will recognise this signal and accept it on all test pieces. The computer will actually be comparing the test piece under scrutiny with standard non-defect master. In addition a reference test piece should be used to check that the specified reference defects really will be detected. This is needed to adjust the settings and sensitivity of the system. 

Following the draft european standard [4] for type testing, quality of the detection media shall be verified on 2 reference blocks as shown in Fig. 2. On the reference block No. 1, created by Mr. Dickhaut [7], (Nr. 3 of the MTU) the indications shall be valuated by comparison with the indications of a detection medium with known quality. On reference block No. 2 (AFNOR-C A-C) the lenght of the indications shall be determined as a measure for the quality. 

In order to check the the validity of this method [8], 6 detection media Px where selected and applied on the reference pieces following the instructions of the standard (inclination angle 45° 3 applications of the detection medium and averaging). The arrangements of the cuts can be seen at Fig. 3. Indications or parts of indications are chosen for the valuation and marked by dashed lines. 

Up to now the Reference Block Method and the DGS-Method are world wide the most important techniques for evaluating defect signals in manual Ultrasonic Testing. Even today, individual national standards refer to either one of these two echo evaluation techniques. However, both reflected echo signals from natural defects are compared with an echo from a known reference reflector at the same distance. The result of the evaluation is either... 

We are confident that any user of this combined evaluation technique, as well as the development of future test standards for manual ultrasonic testing will benefit from this result, because it allows a greater flexibility in the applicable method without loosing reliability. Often an expensive production of a reference block can be avoided and therefore testing costs are reduced. Since all calculations are performed by a PC, the operator can fully concentrate on his most important duty scanning the workpiece and observing the A-scan. Additional time will be saved for the test documentation, since all testing results are stored in the instrument s memory (the PC s hard drive) with full link to the Software World (Microsoft Word, Excel, etc.). 

There are two procedures for doing this. The first makes use of a metal probe coated with an emitter such as polonium or Am (around 1 mCi) and placed above the surface. The resulting air ionization makes the gap between the probe and the liquid sufficiently conducting that the potential difference can be measured by means of a high-impedance dc voltmeter that serves as a null indicator in a standard potentiometer circuit. A submerged reference electrode may be a silver-silver chloride electrode. One generally compares the potential of the film-covered surface with that of the film-free one [83, 84]. 

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