Determination limit, definition

Limit of Quantification For the limit of quantification, or limit of determination, definitions and formulas are very similar to those of LOD, except that for LOQ, is taken to be 5, 6, or even 10 [2, 4,15, 56,72, 96]. A value of 10 for means that the %RSD at the limit of quantification is 10%. The LOQ thus corresponds to that concentration or amount of analyte quantifiable with a variation coefficient not higher than 10% [98]. The LOQ is always higher than the LOD and is often taken as a fixed multiple (typically 2) of the detection limit [4]. Also, the determination limit is referred to as the signal 10 times above the noise or background signal, corresponding to a signal-to-noise ratio of 10 1 [72, 85]. 

Let the convective-diffusion-controlled region be defined as those sets of conditions (Pe, R, A/kT) for which the rate may he calculated to within 10% by ignoring London forces. Similarly, let the London-force-controlled region be those sets of conditions for which the rate may be calculated to within 10% by ignoring Brownian motion. These definitions suggest a method for determining limits for the regions. 

But the question remains as to what const outes no residue." Currie (] ) examined the corresponding problem of detection limits in radiochemical procedures and was frustrated by the differences in terminology and definitions which resulted in a range of three orders of magnitude for detection limits calculated for the same system. Figure 4, taken from his paper, shows the situation with respect to a specific radioactivity process. The horizontal lines indicate three specific levels L, "decision limit," the level a signal must exceed to permit a decision as to whether or not the result of an analysis indicates detection Lj), "detection limit," the level above which an analytical procedure can be relied upon to lead to detection and Lq, "determination limit," the level above... 

Wilson s definitions generally agree with those of Currie except that he uses the terms criterion of detection and limit of detection rather than critical level and detection limit, and restricts himself to a consideration of paired observations. Currie also Introduces a new term, the determination limit, Lq, which is defined as that concentration for whl the relative standard deviation is 10%. Results above the determination limit may therefore be considered satisfactory for quantitative analysis. Table II compares the definitions by Currie with those of Kaiser for "paired observations . ... 

Detection Limit Criterion. The criterion used to define the detection limit, or perhaps as important, the protocol used to measure it, can be critical in establishing a valid detection limit. Currie [9] has described the wide variation in detection limit definitions for radiochemical measurements reported in the literature. lUPAC [2] recommends the detection limit, c, be defined as the concentration of an analyte equal to a background-corrected signal, xl - X3, three times the estimated standard deviation of a single determination using 20 measurements of the blank. 

This coupling, for example, follows immediately from the fact that the potential differences for separate electrochemical steps are strictly determined by intervalence equilibrium constants values see Eq. (2.23). If the whole process is irreversible, then such coupling invokes uncertainty to the determination (even definition) of the irreversible limiting step. 

Definition The determination limit of an individual analytical procedure, although not officially defined, is widely recognised as being the lowest amount of an analyte in a sample, which can be determined as an exact value. 

At X-ray fluorescence analysis (XRF) of samples of the limited weight is perspective to prepare for specimens as polymeric films on a basis of methylcellulose [1]. By the example of definition of heavy metals in film specimens have studied dependence of intensity of X-ray radiation from their chemical compound, surface density (P ) and the size (D) particles of the powder introduced to polymer. Have theoretically established, that the basic source of an error of results XRF is dependence of intensity (F) analytical lines of determined elements from a specimen. Thus the best account of variations P provides a method of the internal standard at change P from 2 up to 6 mg/sm the coefficient of variation describing an error of definition Mo, Zn, Cu, Co, Fe and Mn in a method of the direct external standard, reaches 40 %, and at use of a method of the internal standard (an element of comparison Ga) value does not exceed 2,2 %. Experiment within the limits of a casual error (V changes from 2,9 up to 7,4 %) has confirmed theoretical conclusions. 

The potentiometry sensor (ion-selective electrode) controls application for determination of polymeric surface-active substances now gets the increasing value. Potentiometry sensor controls are actively used due to simple instmment registration, a wide range of determined concentrations, and opportunity of continuous substances contents definition. That less, the ionometry application for the cation polymeric SAS analysis in a solution is limited by complexity of polycation charge determination and ion-exchanger synthesis. 

Opening segments of the IP2 PRA data analysis section describe the definitions of terms and concepts employed, the assumptions made, and limitations recognized during the data base construction. A set of 39 plant-specific component failure mode summaries established the basis for component service hour determinations, the number of failures, and the test data source for each failure mode given for each component. Generic data from WASH-1400, IEEE Std 500, and the LER data summaries on valves, pumps, and diesels were combined with plant-specific failure data to produce "updated" failure information. All the IP2 specialized component hardware failure data, both generic and updated, are contained in Table 1.5.1-4 (IP3 1.6.1-4). This table contains (by system, component, and failure mode) plant-specific data on the number of failures and service hours or demands. For some components, it was determined that specifications of the system was warranted because of its impact on the data values. 

The determination of the temperature at which an oil begins to boil is often of importance, as is also the percentage of the oil which distils within definite limits of temperature. The results obtained in distillation processes must, however, be interpreted very carefully, as the quantitative results depend so largely on the exact conditions of distillation. For ordinary purposes, an ordinary Wurtz flask is useful for determining the temperature at which the liquid first boils, but when an examination of... 

Various materials (e.g., metal, plastics, or rubber) are used to make the flexing elements in these couplings. The use of the couplings is governed by the operational fatigue limits of these materials. Practically all metals have fatigue limits that are predictable, therefore, they permit definite boundaries of operation to be established. Elastomers such as plastic or rubber, however, usually do not have a well-defined fatigue limit. Their service life is determined primarily by conditions of installation and operation. 

The detection limit is another value which is often quoted, and this may be defined in a variety of ways. The most widely accepted definition is that the detection limit is the smallest concentration of a solution of an element that can be detected with 95 per cent certainty. This is the quantity of the element that gives a reading equal to twice the standard deviation of a series of at least ten determinations taken with solutions of concentrations which are close to the level of the blank. 

The compressive data are of limited design value. They can be used for comparative material evaluation and design purposes if the conditions of the test approximate those of the application. The data are of definite value for materials that fail in the compressive test by a shattering fracture. On the other hand, for those that do not fail in this manner, the compressive information is arbitrary and is determined by selecting a point of compressive deformation at which it is considered that a complete failure of the material has taken place. About 10% of deformation are viewed in most cases as maximum. 

When RPs are granulated, the lengths of the fibers are reduced. On reprocessing with virgin materials or alone, their processability and product performances are definitely change. So it is important to determine if the change will affect final product performances. If it will, a limit for the amount of regrind mix should be determined or no recycled RP is to be used. Use it in some other product such as simulated wood. 

The preferred kinetic model for the metathesis of acyclic alkenes is a Langmuir type model, with a rate-determining reaction between two adsorbed (complexed) molecules. For the metathesis of cycloalkenes, the kinetic model of Calderon as depicted in Fig. 4 agrees well with the experimental results. A scheme involving carbene complexes (Fig. 5) is less likely, which is consistent with the conclusion drawn from mechanistic considerations (Section III). However, Calderon s model might also fit the experimental data in the case of acyclic alkenes. If, for instance, the concentration of the dialkene complex is independent of the concentration of free alkene, the reaction will be first order with respect to the alkene. This has in fact been observed (Section IV.C.2) but, within certain limits, a first-order relationship can also be obtained from many hyperbolic models. Moreover, it seems unreasonable to assume that one single kinetic model could represent the experimental results of all systems under consideration. Clearly, further experimental work is needed to arrive at more definite conclusions. Especially, it is necessary to investigate whether conclusions derived for a particular system are valid for all catalyst systems. 

In some cases there also occur semistable limit cycles (in this discussion the single term cycle is used wherever it is unambiguous or if no confusion is to be feared) characterized by stability on one side and instability on the other side. Figure 6-5(a), (b), and (c) illustrate these definitions. Physically, only stable cycles are of interest the unstable cycles play the role of separating the zones of attraction of stable cycles in the case when there are several cycles. It is seen from this definition that, instead of an infinity of closed trajectories, we have now only one such trajectory determined by the differential equation itself and the initial conditions do not play any part. In fact, the term initial conditions means just one point (x0,y0) of the phase plane as a spiral trajectory O passes through that point and ultimately winds itself onto the cycle 0, it is clear that the initial conditions have nothing to do with this ultimate closed trajectory C—the stable [Pg.329]

As indicated in Section 3.7.9, this definition of ReMR may be used to determine the limit of stable streamline flow. The transition value (R ur)c is approximately the same as for a Newtonian fluid, but there is some evidence that, for moderately shear-thinning fluids, streamline flow may persist to somewhat higher values. Putting n = 1 in equation 3,140 leads to the standard definition of the Reynolds number. 

Various in situ and ex situ methods have been used to determine the real surface area of solid electrodes. Each method10,15 32 67,73 74 218 is applicable to a limited number of electrochemical systems so that a universal method of surface area measurement is not available at present. On the other hand, a number of methods used in electrochemistry are not well founded from a physical point of view, and some of them are definitely questionable. In situ and ex situ methods used in electrochemistry have been recently reviewed by Trasatti and Petrii.73 A number of methods are listed in Table 3. 

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