Measurement procedure

Peaks are intermediately stored before the measurement, and thus very labile compounds may undergo decomposition or isomerization during this procedure. 

The chromatographic stage is not interrupted and therefore no stop-start effects will create disturbances. The peaks are separated in the storage loops, and therefore the NMR measurement time is not limited and will not decrease the performance of other peaks. In complex chromatograms the chance of finding the peak(s) of interest is dramatically increased. As in the direct stop-flow mode, the static conditions provide stability and the best NMR conditions for the acquisition of all kinds of high-resolution ID and 2D NMR spectra. 

The first attempts to include a mass spectrometer in the LC-NMR set-up were made several years ago. Nowadays, LC-NMR/MS systems are commercially available, and the usage of this kind of set-up will be briefly evaluated below [1-7]. 

The first idea for including an MS system in such a set-up was to yield all information about a sample with just one sample preparation, i.e. to provide one hyphenated experiment. A closer look at the practical situation shows that due to the large sensitivity difference between the NMR and MS instruments, of at least 103 to 106, and even higher, the performance of the mass spectrometer would be hindered by the NMR spectrometer. The speed and sensitivity of the MS unit would provide detailed data concerning all compounds, even in the onflow mode, whereas only the major compounds would be visible in the NMR spectra. 

In the stop-flow mode, the additional time could be used to acquire MS spectra of higher order, although these experiments would still be finished long 

The instrumentation needed includes a spectrophotometer, optical cells (at least two, one for determining pH in the stock solution and one for the sample) plus equipment for automation if this is desirable. The determination of the absorbance at several wavelengths can be achieved either by a scanning spectrophotometer or by a diode array spectrophotometer. The advantage with the latter instrument is that it measures the whole spectrum in a short time, making it suitable for automated measurements. 

In the manual system, a known volume of the indicator stock solution is added directly to the optical cell, after the cell has been filled with seawater sample. The volume of indicator stock solution added depends on its concentration and the cell volume. The best accuracy in the absorbance readings is achieved if they are in the range of 0.2-1 absorbance units. Typically, the optical cell volume during the manual procedure is about 30 mL with a path length of 100 mm. The cell should be temperature-controlled and the temperature has to be recorded at the time of the absorbance reading. 

This pertmbation is an effect of the difference between the pH of the sample and that of the indicator stock solution. A correction can be made in two ways. One option is to add double volumes of indicator stock solution to seawater samples of varying pH. A plot is made of the absorbance ratio (Q) against indicator volume added, and the linear regression fit to this Une can then be used to make the correction. Alternatively, the coirection to be made can be read from an error diagram, computed by the theoretical titration of a sample by the indicator added, such as that shown in Fig. (7-4). 

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There are two types of measurement errors, systematic and random. The former are due to an inherent bias in the measurement procedure, resulting in a consistent deviation of the experimental measurement from its true value. An experimenter s skill and experience provide the only means of consistently detecting and avoiding systematic errors. By contrast, random or statistical errors are assumed to result from a large number of small disturbances. Such errors tend to have simple distributions subject to statistical characterization. 

A first comprehensive round robin test described in 4.1 which is open to all interested parties will be followed periodically by round robin tests in a reduced extent to ensure the further harmonisation of measurement procedures. The check of measurering equipments and procedures is an inalienable requirement for the further steps for providing the users with constant film quality. Together with sample tests performed by BAM as indicated in section 4.2 and and the production control by the manufacturer it will be possible to survey the film systems whether they meet the requirements of one of the film classes of EN 584-1. 

Metrological attestation as the procedure that ensures reproducibility and comparability of the results of measurements is specified in GOST 8.010-90 State System of Measurements. Procedures of Measurements Implementation didn t find wide use in NDT. In airspace industry, railway and naval transport the requirements of approval of test procedures is in force more than 20 years. In chemical and oil-chemical sectors the similar requirements were less explicit. In some industries, for example in building GOST 8.010-90 was not put into account. 

GOST 8.010-90 State System of Measurements. Procedures of Measurements Implementation... 

CTB 8006-93 State metrological surveillance and inspection of measuring procedures... 

A measurement procedure has been developed that allows to determine the mass of the inclusions as well as their locations with respect to radius, angle, and depth (2). For the depth determination use is made of the approximate 1/R dependence of the magnetic field strength from the distance R to the inclusion When in a first measurement at a small lift off an inclusion is detected, the measurement is repeated at an increased lift off From the signal ratio the depth can be calculated or seen from a diagram like fig. 5a which was generated experimentally. After that, from calibration curves like fig. 5b the absolute value of the signal leads to the mass of the inclusion. 

Handbook of Radioactivity Measurements Procedures, NCRP Report No. 58, 2nd ed.. National Council on Radiation Protection and Measurement, Bethesda, Md., 1985. 

Acceptance Testing Test procedures to determine the water cooling capacity of towers. Instrumentation used and measurement procedures should be those recommended by the Cooling Tower Institute (CTI) in its "Acceptant Text Procedures. "... 

The measurement procedure must have been tested previously under realistic conditions and should give representative results of worker exposure. Thus, it should not be influenced by unusual work schedules, where tasks may not be well defined or planned. The procedure should include... 

The measuring procedure used must be appropriate to the chemical agent to be measured, its limit value, and the wotkplace atmosphere so that the results show the concentration of the agent in the same terms as the limit value. Also, the limits of detection, sensitivity, and precision of the measuring procedure must be appropriate to the limit value. 

The goals and the final quantities to be obtained determine the method to be used. As a first approach, it is always worth checking if a documented and proven method exists. Standardized methods are often the best. They are developed by experts in the field and are usually of a high quality and are well documented. Frequently no standards can be applied and generally known methods have to be relied on. Sometimes situations occur when the whole of the measurement procedure has to be tailored for the specific situation. This is a very demanding task and considerable experience is required. 

The assumption of a self-similar flow (Reynolds number-independent flow) simplifies full-scale experiments and is also a useful tool in the formulation of simple measuring procedures. This section will show two examples of self-similar flow where the Archimedes number is the only important parameter. 

Averaging time The time period over which the measuring procedure provides a single value. 

Measuring procedure Procedure for sampling and analyzing one or more chemical agents in the air, including the storage and transportation of the sample to the laboratory. 

Overall uncertainty of a measuring procedure or of an instrument The quantity used to characterize the uncertainty of results given by an apparatus or a measuring procedure, expressed on a relative basis by a combination of bias and precision, according to a formula. 

Specific measuring range The range of concentration values for w hich the overall uncertainty of a measurement procedure is intended to lie within specific limits. 

Specifications define which characteristics to measure - procedures define how the characteristics should be measured. 

Viscosity. The measurement procedure for API funnel viscosity is the same as for water-base muds. Since temperature affects the viscosity, API procedure recommends that the mud temperature should always be recorded along with the viscosity. 

We have said that every time the calibration analyzes a new unknown sample, this amounts to an additional validation test of the calibration. It can be a major mistake to believe that, just because a calibration worked well when it was being developed, it will continue to produce reliable results from that point on. When we discussed the requirements for a training set, we said that collection of samples in the training set must, as a group, be representative in all ways of the unknowns that will be analyzed by the calibration. If this condition is not met, then the calibration is invalid and cannot be expected to produce reliable results. Any change in the process, the instrument, or the measurement procedure which introduces changes into the data measured on an unknown will violate this condition and invalidate the method If this occurs, the concentration values that the calibration predicts for unknown samples are completely unreliable We must therefore have a plan and procedures in place that will insure that we are alerted if such a condition should arise. 

Ref 58 discusses the application of electronic instrumentation to moisture measurement. Procedures amenable to use for energetic materials include ... 

Shipping analysis is an extremely sensitive electrochemical technique for measuring trace metals (19,20). Its remarkable sensitivity is attributed to the combination of an effective preconcentration step with advanced measurement procedures that generate an extremely favorable signal-to-background ratio. Since the metals are preconcentrated into the electrode by factors of 100 to 1000, detection limits are lowered by 2 to 3 orders of magnitude compared to solution-phase voltammetric measurements. Hence, four to six metals can be measured simultaneously in various matrices at concentration levels down to 10 10 i. utilizing relatively inexpensive... 

Beyond specific polarographic techniques variations of these methods have been developed aiming at simplified and fast evaluation using modified measurement procedures and data processing. Oldham and... 

Definition and Uses of Standards. In the context of this paper, the term "standard" denotes a well-characterized material for which a physical parameter or concentration of chemical constituent has been determined with a known precision and accuracy. These standards can be used to check or determine (a) instrumental parameters such as wavelength accuracy, detection-system spectral responsivity, and stability (b) the instrument response to specific fluorescent species and (c) the accuracy of measurements made by specific Instruments or measurement procedures (assess whether the analytical measurement process is in statistical control and whether it exhibits bias). Once the luminescence instrumentation has been calibrated, it can be used to measure the luminescence characteristics of chemical systems, including corrected excitation and emission spectra, quantum yields, decay times, emission anisotropies, energy transfer, and, with appropriate standards, the concentrations of chemical constituents in complex S2unples. 

Functions of Standards. Fluorescent standards can be used for three basic functions calibration, standardization, and measurement method assessment. In calibration, the standard is used to check or calibrate Instrument characteristics and perturbations on true spectra. For standardization, standards are used to determine the function that relates chemical concentration to Instrument response. This latter use has been expanded from pure materials to quite complex standards that are carried through the total chemical measurement process (10). These more complex standards are now used to assess the precision and accuracy of measurement procedures. 

Procedures for determining the spectral responslvlty or correction factors In equation 2 are based on radiance or Irradlance standards, calibrated source-monochromator combinations, and an accepted standard. The easiest measurement procedure for determining corrected emission spectra Is to use a well-characterized standard and obtain an Instrumental response function, as described by equation 3 (17). In this case, quinine sulfate dlhydrate has been extensively studied and Issued as a National Bureau of Standards (NBS) Standard Reference Material (SRM). 

Nevertheless, a mutual understanding about colors does work because conunon rules have been implemented by education, habituation, socially approved behavior, and properties that appear to individuals simultaneously, e.g., the vertical signal order of traffic lights. However, those rules are of limited value when color perception is the base for aesthetic appreciation as is the case for many industrial products and food products. In order to meet the demands of as many consumers as possible, producers look for a standard consumer who is most representative of the group. This requires establishment of a reliable measurement procedure that can be reproduced easily and be adapted to the various conditions under which it is applied light conditions, more or less opaque or translucent objects, object surface structures, etc. These measurement procedures were created more than a century ago and have... 

Identify the test instrumentation and measurement procedures, schedules, etc, that are required for a fully specified test design ... 

Risk, i.e. the probability that injury of a certain severity will occur under certain conditions, safety, i.e. the measures, procedures and conditions which will minimize the risk, and loss prevention, i.e. the systematic approach to preventing accidents and their consequences to people, equipment and environment. 

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). 

Reported data should achieve a clear, purpose-oriented level of accuracy and precision, especially when data produced by several laboratories often needs to be compared as part of a decision process. It has become accepted by more and more analysts that to overcome differences between national standards and specifications and measurement procedures or to make Total Quality Management (TQM) an achievable reality, freely available and internationally agreed points of reference are needed. Therefore RMs and CRMs must be easily available indeed the availability of reference materials has been described as an issue of strategic importance to the EU (Maier et al. 1997). 

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