Detection approaches

When using the defect-detection approach to quality control certain problems develop. Inspection does nothing to improve the process and is not very good at sorting good-from-bad. Also, sampling plans developed to support an acceptable quality level (AQL) of 5%, for example, say that a company is content to deliver or reject 5% defects. 

Gong, Y. and Yeung, E.S., An absorption detection approach for multiplexed capillary electrophoresis using a linear photodiode array, Anal. Chem. 71,4989, 1999. 

Cheung et al. [702] have evaluated various solvent evaporative high-temperature SEC-FTIR interfaces. This detection approach was initially employed only for qualitative analysis, but is recently also being used quantitatively. For that purpose the polymer film quality generated by the interface is of critical importance (thickness effects). Table 7.76 lists the main features of evaporative SEC-FITR for polymer analysis. 

Release Detection Approaches for Modern Tank Systems... 

Levels of carotenoids are much lower in the skin relative to the macula of the human eye, but higher light excitation intensities and longer acquisition times can be used in Raman detection approaches to compensate for this drawback. Since the bulk of the skin carotenoids are in the superficial layers of the dermis, and since the concentrations are relatively low, the thin-film Raman equation given above, Equation 6.1, should still be a good approximation. 

To validate the skin carotenoid RRS detection approach, we initially carried out an indirect validation experiment that compared HPLC derived carotenoid levels of fasting serum with RRS derived carotenoid levels for inner palm tissue sites. Measuring a large group of 104 healthy male and female human volunteers, we obtained a significant correlation (p < 0.001) with a correlation coefficient of 0.78 (Smidt et al. 2004). Recently, we carried out a direct validation study, in which we compared in vivo RRS carotenoid skin responses with HPLC-derived results, using the thick... 

For oxalate detection, authors proposed a similar detection approach for recognition of oxalate via an immobilized oxalate oxidase/peroxidase couple and dye precursors MBTH (3-methyl-2-benzothiazolinone hydrazone) and DMAB (3-dimethylaminobenzoic acid). The peroxide generated by oxidation of oxalate to CO2 reacted with the dye precursors in a peroxidase-catalyzed reaction to yield an indamine dye with absorption maximum at 590 nm. The concentration of oxalate was correlated with increased absoiption from dye. 

In summary, this zero-dead-volume integrated CL detection approach provides two major advantages, namely ... 

Since both the bubble cell and the Z-cell need high resolution in order to observe the sensitivity increase, test whether you can avoid the use by a clever injection procedure such as sample stacking or transient ITP (isotachophoresis) instead. Further information on detection approaches is provided in Chapters 3, 5, and 15. 

The following sections present a summary of the physics that underlies the nuclear detection technologies, a survey of neutron-based detection approaches, and an overview of non-neutron-based nuclear detection technologies. 

Signal-to-noise considerations make most neutron-based explosive detection approaches very difficult to implement. The basis for combining multiple detection approaches (FNA, along with thermal gamma detection and neutron transmission spectroscopy) in a FNAP application that preserves the small volume advantage of a APSTNG remains to be established. There are distinct advantages associated with the API approach, but the concomitant reductions in available neutron flux, issues of tube lifetime, and the intrinsic poor spatial resolution must be taken into consideration for potential applications. 

Nuclear detection approaches that use radioactive isotojjic sources (e.g., Cf for spontaneous fission and asociated neutron emission or ° Co for gamma emission) will have to obtain state and federal hcenses to field the equipment and abide by apphcable health and safety regulations. The Hcensing process takes some time to put into place and may restrict the easy movement of the detection equipment to new locations. This impacts the abffity to rapidly re-locate equipment based up inteUigence estimates of the behavior of smugglers. The use of fixed pre-licensed sites can help to some extent. 

Ion-exchange principles and applications [2-5] have recently been reviewed by Lucy [6] and Fritz [7] and a wide number of books and reviews are available on ion chromatography [8-13] and on recent developments of new kind of suppressors [14-16] or different detection approaches [17],... 

Hi. Lysine. Gamma radiolysis of aerated aqueous solution of lysine (94) has been shown, as inferred from iodometric measurements, to give rise to hydroperoxides in a similar yield to that observed for valine and leucine. However, attempts to isolate by HPLC the peroxidic derivatives using the post-column derivatization chemiluminescence detection approach were unsuccessful. This was assumed to be due to the instability of the lysine hydroperoxides under the conditions of HPLC analysis. Indirect evidence for the OH-mediated formation of hydroperoxides was provided by the isolation of four hydroxylated derivatives of lysine as 9-fluoromethyl chloroformate (FMOC) derivatives . Interestingly, NaBILj reduction of the irradiated lysine solutions before FMOC derivatization is accompanied by a notable increase in the yields of hydroxylysine isomers. Among the latter oxidized compounds, 3-hydroxy lysine was characterized by extensive H NMR and ESI-MS measurements whereas one diastereomer of 4-hydroxylysine and the two isomeric forms of 5-hydroxylysine were identified by comparison of their HPLC features as FMOC derivatives with those of authentic samples prepared by chemical synthesis. A reasonable mechanism for the formation of the four different hydroxylysines and, therefore, of related hydroperoxides 98-100, involves initial OH-mediated hydrogen abstraction followed by O2 addition to the carbon-centered radicals 95-97 thus formed and subsequent reduction of the resulting peroxyl radicals (equation 55). 

Postcolumn photochemical reactions are another approach to the detection problem. High-intensity UV light, generally provided by a Hg or Zn lamp, photolyzes the HPLC effluent, which passes through a Teflon (47) or quartz tube. The photolysis reaction determines the nature of the subsequent detection. If the compound has a UV chromophore, such as an aromatic ring, and an ionizable heteroatom, such as chlorine, then the products of the reaction can be detected conductometrically. Busch et al. (48) have examined more than 40 environmental pollutants for applicability to detection with photolysis and conductance detection. Haeberer and Scott (49) found the photoconductivity approach superior to precolumn derivatization for the determination of nitrosoamines in water and waste water. The primary limitation of this detection approach results from the inability to use mobile phases that contain ionic modifiers, that is, buffers and... 

EC detection methods have often been considered incompatible with electrophoresis because the combination of high voltages applied for electrophoretic separation and sensitive electrodes is seen as a conflict. However, traditional capillary electrophoresis takes advantage of many of them and with appropriate designs of the detector cell the separation voltage does not interfere with the EC measurement. On the other hand, there are several reports in which this interference is taken as a benefit for generating new detection approaches (see Sections 34.1.3.1 and 34.1.3.2) [52-54],... 

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