Reproducibility parameter selection

The advantages associated with the MAP technology as compared to conventional and automatic Soxhlet methods are considerable (Table 3.33). In MAP high sensitivity and selectivity by fractionation are achieved using different extraction media with similar, or better, linearity and reproducibility parameters. One of the principle features of the process is the lower temperatures observed in the microwave-extracted materials in contrast to volumetric heating usually experienced in traditional solvent procedures. These lower temperatures... 

This study focused on determination of a scale-up factor that is, determining which process parameter must be held constant or changed in a prescribed way to reproduce the selectivity upon scale-up. Published results of investigations of the Bourne III system related to concentration effects and addition times were implemented in the experimental protocol. Operationally, the experiments were conducted as follows ... 

This is not always so in the case of thermal methods. The results obtained depend upon the conditions used to prepare the sample, the instrumental parameters selected for the run and the chemical reactions involved. That is not to say that results are not reproducible provided similar conditions are selected. For example, it is possible to compare samples of a polymer to see if their behaviour is good or bad according to their potential use, but the experimental parameters used for running each sample must be the same. 

A + A3. AlJ was formed in collisions of A with internally cold A3 for a thermal distribution of relative translational energies at 200 K and impact parameters selected from a distribution over the range 0 < b < 10 A. An ensemble of 256 collisions was calculated. Reproduced with permission of copyright holder. 

A third parameter to consider is the column construction. Thus the sample applicator should provide optimal sample application to give the most performance possible out of the packed bed. Constructions should also allow simple, fast, and reproducible packing of the column. Because costs for repacking of columns are a substantial operating cost item in industrial chromatography, the selection of column construction from this point of view is also important. Some novel column constructions allow very simple procedures both for laboratory and for industrial scale (e.g., INdEX columns, see Section V). 

Regarding current ab initio calculations it is probably fair to say that they are not really ab initio in every respect since they incorporate many empirical parameters. For example, a standard HF/6-31G calculation would generally be called "ab initio", but all the exponents and contraction coefficients in the basis set are selected by fitting to experimental data. Some say that this feature is one of the main reasons for the success of the Pople basis sets. Because they have been fit to real data these basis sets, not surprisingly, are good at reproducing real data. This is said to occur because the basis set incorporates systematical errors that to a large extent cancel the systematical errors in the Hartree-Fock approach. These features are of course not limited to the Pople sets. Any basis set with fixed exponent and/or contraction coefficients have at some point been adjusted to fit some data. Clearly it becomes rather difficult to demarcate sharply between so-called ab initio and semi-empirical methods.4... 

A parameter that is convenient for said purpose is the electrode potential E it must not be confused with the concept of a potential difference between the electrode and the electrolyte. By convention the term electrode potential E is used to denote the OCV of a galvanic cell that consists of the given electrode (the one that is studied) and a reference electrode selected arbitrarily. Thus, the potential of this electrode is compared with that of a reference electrode that is identical for all electrodes being studied. In accordance with this dehnition, the electrode potential of the reference electrode itself is (conventionally) regarded as zero. Any electrode system for which the equilibrium Galvani potential is established sufficiently rapidly and reproducibly can be used as a reference electrode. We shall write the electrode system to be used as the reference electrode, generally, as M /E ... 

Selected Activation Parameters for Cyclophosphazene Aminolysis Reactions (Reproduced with permission from Ref. 14). Copyright American Chemical... 

Trying to determine which column is ideal for a specific analysis can be difficult with over 1000 different columns on the market [74]. A proper choice implies a definition of parameters such as column material, stationary phase (polarity), i.d., film thickness and column length. Guides to column selection are available [74,75]. The most important consideration is the stationary phase. When selecting an i.d., sample concentration and instrumentation must be considered. If the concentration of the sample exceeds the column s capacity, then loss of resolution, poor reproducibility and peak distortion will result. Film thickness has a direct effect on retention and the elution temperature for each sample compound. Longer columns provide more resolving probe, increase analysis times and cost. 

Packed column SFC and CE are both able to make inroads into the application area served by HPLC, but from opposite extremes of polarity and with little overlap. CE is likely to be more efficient and faster, but mostly applicable to very polar molecules and ions. SFC qualifies as a more reproducible, trace technique, with greater selectivity and multiple detection options. HPLC and CE have been compared [365], Owing to their orthogonality, CZE and SFC are worth developing, not in competition or as an alternative to HPLC, but as an additional method in order to augment the information obtained from the analysis. With the broad scope of possible eluents and stationary phases, HPLC has fewer constraints than SFC and CZE. The parameters influencing selectivity may be used as a guide to optimisation (Table 4.44). 

Alemu et al. [35] developed a very sensitive and selective procedure for the determination of niclosamide based on square-wave voltammetry at a glassy carbon electrode. Cyclic voltammetry was used to investigate the electrochemical reduction of niclosamide at a glassy carbon electrode. Niclosamide was first irreversibly reduced from N02 to NHOH at —0.659 V in aqueous buffer solution of pH 8.5. Following optimization of the voltammetric parameters, pH and reproducibility, a linear calibration curve over the range 5 x 10 x to 1 x 10-6 mol/dm3 was achieved, with a detection limit of 2.05 x 10-8 mol/dm3 niclosamide. The results of the analysis suggested that the proposed method has promise for the routine determination of niclosamide in the products examined [35]. 

The properties of a pH electrode are characterized by parameters like linear response slope, response time, sensitivity, selectivity, reproducibility/accuracy, stability and biocompatibility. Most of these properties are related to each other, and an optimization process of sensor properties often leads to a compromised result. For the development of pH sensors for in-vivo measurements or implantable applications, both reproducibility and biocompatibility are crucial. Recommendations about using ion-selective electrodes for blood electrolyte analysis have been made by the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) [37], IUPAC working party on pH has published IUPAC s recommendations on the definition, standards, and procedures... 

The electronics of CUORICEMO (see Section 16.6) consists of a complex anticoincidence system. One would hope that signals from all detectors had the same amplitude and shape for the same input. For this reason, all the components for the 56 detectors were carefully selected to be equal. Also the mounting of the components was made with the most reproducible technique. Nevertheless, there are some parameters such as the contact resistances between the thermistors and the absorbers and especially those between the absorbers and the frame which show a wide spread in their values. 

A parameter defined as the relative retention, or selectivity, is often reported for a given instrumental chromatography system as a number that ought to be able to be reproduced from instrument to instrument and laboratory to laboratory regardless of slight differences that might exist in the systems (column lengths, temperature, etc.). This parameter compares the retention of one component (1) with another... 

With regard to quantitative measurements of APG surfactants in, e.g. environmental samples, the authors stressed that it was of crucial importance to promote the formation of the desired molecular (or adduct) ion in order to obtain reproducible mass spectra. If tuning of the ESI interface parameters did not suffice to yield abundant ions of the selected species, acquisitions of the mass spectrometric detector after negative ionisation in conjunction with appropriate selection of the mobile phase composition were used as an alternative despite the lower sensitivity in this mode [1,2],... 

Therefore, the development and validation of a scientifically sound dissolution method requires the selection of key method parameters that provide accurate, reproducible data that are appropriate for the intended application of the methodology. It is important to note that while more extensive dissolution methodologies may be required for bioequivalency evaluations or biowaivers (i.e., multiple media, more complex dissolution media additives, and multiple sampling time points), it is also essential for the simplified, routine quality control dissolution method to discriminate batch-to-batch differences that might affect the product s in vivo performance. 

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