Recovery criteria

Thus, a broad range of sometimes complementary analytical techniques is available at present for the characterisation of the various PAH/POM emissions. For standardisation purposes, candidate methods must be tested extensively in a collaborative exercise to determine and evaluate repeatability, reproducibility and recovery criteria before final definition and approval. (Recently, the method detection limit, defined as the concentration which can be detected at a specific confidence level, was proposed as one criterion for assessing the performance of an analytical method (18)). 

The type of development, type and number of development wells, recovery factor and production profile are all inter-linked. Their dependency may be estimated using the above approach, but lends itself to the techniques of reservoir simulation introduced in Section 8.4. There is never an obvious single development plan for a field, and the optimum plan also involves the cost of the surface facilities required. The decision as to which development plan is the best is usually based on the economic criterion of profitability. Figure 9.1 represents a series of calculations, aimed at determining the optimum development plan (the one with the highest net present value, as defined in Section 13). 

The first criterion was associated with improved secondary and tertiary petroleum recovery processes. This is the justification for the patent appHcations issued to the Dow (50) and Exxon (51) corporations. The additional costs of production and the increased adsorption of such modified water-soluble polymers are detrimental to the commercial appHcation of such polymers and even the academic studies in this area have decreased in recent years. 

Net Present Va.Iue, Each of the net annual cash flows can be discounted to the present time using a discount factor for the number of years involved. The discounted flows are then all at the same time point and can be combined. The sum of these discounted net flows is called the net present value (NPV), a popular profit criterion. Because the discounted positive flows first offset the negative investment flows in the NPV summation, the investment capital is recovered if the NPV is greater than zero. This early recovery of the investment does not correspond to typical capital recovery patterns, but gives a conservative and systematic assumption for investment recovery. 

Following this procedure urea can be determined with a linear calibration graph from 0.143 p.g-ml To 1.43 p.g-ml and a detection limit of 0.04 p.g-ml based on 3o criterion. Results show precision, as well as a satisfactory analytical recovery. The selectivity of the kinetic method itself is improved due to the great specificity that urease has for urea. There were no significant interferences in urea determination among the various substances tested. Method was applied for the determination of urea in semm. 

Since no special ligand design is usually required to dissolve transition metal complexes in ionic liquids, the application of ionic ligands can be an extremely useful tool with which to immobilize the catalyst in the ionic medium. In applications in which the ionic catalyst layer is intensively extracted with a non-miscible solvent (i.e., under the conditions of biphasic catalysis or during product recovery by extraction) it is important to ensure that the amount of catalyst washed from the ionic liquid is extremely low. Full immobilization of the (often quite expensive) transition metal catalyst, combined with the possibility of recycling it, is usually a crucial criterion for the large-scale use of homogeneous catalysis (for more details see Section 5.3.5). 

Precision is a measure of the agreement between replicate assays and is usually expressed as the coefficient of variation (CV). A CV of 15% or less is desired although, like accuracy, some leniency in this criterion is made for samples at very low concentrations. Also, the regulatory agencies give some consideration to the combined impact of accuracy and precision. For example, a method that has a recovery of less than 70% but a CV of less than 10% might be viewed more favorably than a method with a 90% recovery and a CV of 20%. 

The limit of detection (LOD) is an important criterion of the efficiency of an analytical method. It is characterized by the smallest value of the concentration of a compound in the analytical sample. The detectable amount of anilide compounds is in the range 0.01-0.5 ng by GC and 0.1 ng by HPLC. The limit of quantitation (LOQ) ranges from 0.005 to 0.01 mg kg for vegetables, fruits and crops. The recoveries from untreated plant matrices with fortification levels between 10 and 50 times the LOD and the LOQ are 70-120%. The relative standard deviation (RSD) at 10-50 times the level of the LOD and LOQ are <10 % and <20%, respectively. 

The example given in Table 7.2 is taken from a study to verify the trueness of clinical analyses (Streck [2004]). Recovery rates have been used as the criterion to accept a good agreement between the measured results and the reference values as it is frequently done by analysts. 

The acceptance criterion for recovery data is 98-102% or 95-105% for drug preparations. In biological samples, the recovery should be 10%, and the range of the investigated concentrations is 20% of the target concentrations. For trace level analysis, the acceptance criteria are 70-120% (for below 1 ppm), 80-120% (for above 100 ppb), and 60-100% (for below 100 ppb) [2]. For impurities, the acceptance criteria are 20% (for impurity levels <0.5%) and 10% (for impurity levels >0.5%) [30], The AOAC (cited in Ref. [11]) described the recovery acceptance criteria at different concentrations, as detailed in Table 2. A statistically valid test, such as a /-test, the Doerffel-test, or the Wilcoxon-test, can be used to prove whether there is no significant difference between the result of accuracy study with the true value [29],... 

The influence of pulp potential on the flotation of marmatite, arsenopyrite and pyrrhotite with 10 mol/L butyl xanthate as a collector in the presence of 150 mg/L 2,3-dihydroxyl propyl dithiocarbonic sodium (GX2) has been tested. Taking the flotation recovery to be 50% as a criterion, above which the mineral is considered to be floatable and otherwise not floatable, the upper and lower potential limits of the flotation of marmatite, arsenopyrite and pyrrhotite at different pH are presented in Fig. 5.25 and Table 5.1. It is evident that marmatite is floatable in some range of potential at various pH, whereas arsenopyrite and pyrrhotite are not floatable in the corresponding conditions. It suggests that the flotation separation of marmatite from arsenopyrite and pyrrhotite may be... 

Taking the flotation recovery 50% as a criterion, above which the mineral is... 

An efficacy outcome measure (e.g. change from baseline in a symptom assessment instrument, response rate according to a predefined response criterion, remission rate, time to response, time to relapse according to predefined relapse criteria, etc.). For Phase III trials the primary endpoint should be a clinical event (such as full recovery) or clinical improvement relevant to the patient (e.g. disappearance of specific symptoms). 

Spencer and Dillon (S9) have discussed the problem of elastic recovery of polymeric melts and solutions at the exit of a tube. For the polystyrenes studied, a criterion was developed for the point at which such recovery was sufficient to cause buckling of the filament leaving the tube. 

As a summary of observations on sample preparation of all types, some generalizations can be reiterated. Whenever possible, blank samples spiked with standards should be employed and recovery studies should include assays of each extract, to monitor possible drug-substrate interaction. One technique effective in this regard, is to examine the aqueous phase by TLC after all the "free" drug has been extracted. Standard calibration curves should be compared to similar plots in the presence of sample matrix constituents whenever possible. GC should never be employed as the sole criterion in any analytical evaluation. 

Further considerations pertain to the recovery of the reaction products after its completion. Crystallization of the reaction product may be induced if to the reaction medium, in which it is well soluble, a co-solvent is added in which the product is insoluble. Such combinations may also be used for the recrystallization of the crude product. Since for the latter purification method the solubility should be high at high temperatures but much lower at low temperatures, the temperature coefficient of the solubility becomes an important criterion for the employment of a solvent. Little general guidance on this point can be given, in view of the temperature T appearing in the denominators of both terms of opposite signs in expressions such as (2.15). The impurities need to be retained in the solution at all temperatures. The solvent should be either well volatile, so that it is readily removed from the purified crystals, or else washable away by means of a further, volatile, solvent, in which the crystals remain insoluble. None... 

If the recovery does not meet the specified criterion, the MSA is performed on all samples of the same matrix. 

Many laboratories have a criterion of performance based on the percent chemical yield. The recovery, for example, may have to exceed 50% to meet this criterion. The radiochemical yield is the fractional recovery of the amount of added tracer. Its measurement requires that the counter efficiency (e) is known (see Experiment 6). The counting efficiency can have been determined in a previous experiment and recorded with the detector information. 

The magnitude of the effect is defined here as the difference between the average estimated concentration at the high and low levels of the variables. Two times the standard deviation of the recovery was used as the criterion of significance. to... 

The relative ion abundance criteria for PCDDs/PCDFs listed in Table 6 must be met for all PCDD/PCDF peaks, including the labeled internal and recovery standards in all solutions. The lower and upper limits of the ion abundance ratios represent a 15 percent window around the theoretical abundance ratio for each pair of selected ions. The 13Ci2-2,3,7,8-TCDD cleanup standard contains no 35C1, thus the ion abundance ratio criterion does not apply to this compound. 

These metals are considered hazardous under the Resource Recovery and Conservation Act of 1987 (RCRA) [4]. The RCRA metals occur in chemical forms that are soluble or insoluble in groundwater. The soluble species are of concern from the dispersibility viewpoint. Hence, the test criterion to evaluate whether a given waste stream needs stabilization prior to disposal is based on how much a given hazardous metal dissolves in water in a standardized test. This EPA test, called the Toxicity Characteristic Leaching Procedure (TCLP) [5], is used not only to identify which waste streams need treatment, but also to assess whether the treated waste form is suitable for disposal. This test also sets limits on how little of a hazardous metal is permitted to leach out from a given waste to pass the waste for disposal. If the test determines that the waste is not suitable for safe... 

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