Detection capabilities

Historically, EELS is one of the oldest spectroscopic techniques based ancillary to the transmission electron microscope. In the early 1940s the principle of atomic level excitation for light element detection capability was demonstrated by using EELS to measure C, N, and O. Unfortunately, at that time the instruments were limited by detection capabilities (film) and extremely poor vacuum levels, which caused severe contamination of the specimens. Twenty-five years later the experimental technique was revived with the advent of modern instrumentation. The basis for quantification and its development as an analytical tool followed in the mid 1970s. Recent reviews can be found in the works by Joy, Maher and Silcox " Colliex and the excellent books by Raether and Egerton. ... 

VPD-TXRF is also a facile technique for interface analysis [4.78, 4.79]. Automated VPD equipment (Fig. 4.16) improves both the detection limit (upper range 10 atoms cm ) and the reliability (by > 50%) of the VPD-TXRF measurement [4.14]. Current research focuses on sample holders [4.80, 4.81] and light-element detection capability [4.82-4.84]. 

The purpose of security lighting is to deny the criminal the cover of darkness, which he uses to conceal his activities. In addition, strategically designed lighting can considerably increase the security value of other measures, and it can also assist the detection capabilities of surveillance (manned or CCTV) systems. 

A major consideration in screening is the detection capability of the screen for both false negatives (lack of detection of an active drug) and propensity to find false positives (detection of a response to the compound not due to therapeutic activity of interest). Ostensibly, false positives might not be considered a serious problem in that secondary testing will detect these and they do not normally interfere with the drug discovery process. 

The detection limits, accuracy, and precision of any analytical methodology, as well as the composition of the sample medium, are important parameters in determining the appropriateness of a method to quantify a specific analyte at the desired level of sensitivity within a particular matrix. The lower limit of detection (LLD) has been adopted to refer to the intrinsic detection capability of a measurement procedure (sampling... 

A recent extension of the scope of SPE-GC and SPE-GC-MS concerns the use of AED detection with its multielement detection capability and unusually high selectivity. Hankemeier [67] has described on-line SPE-GC-AED with an on-column interface to transfer 100 iL of desorbing solvent to the GC. The fully on-line set-up is characterised by detection limits of 5-20 ngL because of quantitative transfer of the analytes from the SPE to the GC module. On-line coupling of SPE with GC is more delicate than SPE-LC, because of the inherent incompatibility between the aqueous part of the SPE step and the dry part of the GC system. 

Table 8.39 shows the main features of EDXRF. EDXRF is not able to detect the fine structure of the K, L, M, etc. lines. EDXRF is used for applications which require measurement of a limited number of elements, and where the resolution and ultralow detection limits of wavelength-dispersive systems are not necessary. For example, EDXRF has been used as a rapid screening technique for the determination of Br and Sb in plastic recyclate at a LOD of 5 ppm [230] the method was validated by means of NAA [231]. Conventional EDXRF systems and benchtop units have a limited detection capability for low-Z-elements and cannot directly measure fluorine in processing aids. 

The technique is referred to by several acronyms including LAMMA (Laser Microprobe Mass Analysis), LIMA (Laser Ionisation Mass Analysis), and LIMS (Laser Ionisation Mass Spectrometry). It provides a sensitive elemental and/or molecular detection capability which can be used for materials such as semiconductor devices, integrated optical components, alloys, ceramic composites as well as biological materials. The unique microanalytical capabilities that the technique provides in comparison with SIMS, AES and EPMA are that it provides a rapid, sensitive, elemental survey microanalysis, that it is able to analyse electrically insulating materials and that it has the potential for providing molecular or chemical bonding information from the analytical volume. 

Detection Capability Has been shown to detect advanced stages of microscopic HTHA in base metal, away from welds. Can distinguish HTHA from plate laminations. Has been shown to detect microscopic HTHA in base metal away from welds. Has been shown to detect microscopic HTHA in base metal away from welds. Has been shown to detect microscopic HTHA in base metal away from welds. Has been shown to detect microscopic HTHA in base metal and weld metal. Has been shown to detect microscopic HTHA in base metal and weld metal. Has been shown to detect microscopic HTHA in base metal and weld metal. Has been shown to detect microscopic HTHA in base metal and weld metal. Con reliably detect HTHA only after cracks have formed. Cannot detect microscopic HTHA. e i m z tr> r t- a -0 1 a -j. UJ ai ru o, a a Ln tr UJ UJ Ln -U UJ tr -u 1... 

Detection Capability Can detect HTHA only after cracks have formed. Cannot detect microscopic damage. Can detect and distinguish microfissuring and micro voids due to HTHA from other indications very reliably. Can detect HTHA only after macro size cracks have formed. Cannot detect microscopic damage. Blisters are readily apparent when present. However, HTHA may frequently occur without the formation of surface blisters. Reported to be capable of detecting cracks. Currently not known whether microscopic damage can be detected. 

One of the major advantages of this design is the multimass ion detection capability, i.e., the translational energy distributions of many different masses can be detected simultaneously. In order to detect different masses simultaneously, good mass resolution is necessary. It depends on the distance between the images of adjacent masses and the image width of each mass in the mass axis. 

It should be noted that the term sensitivity sometimes may alternatively be used, namely in analytical chemistry and other disciplines. Frequently the term sensitivity is associated with detection limit or detection capability. This and other misuses are not recommended by IUPAC (Orange Book [1997, 2000]). In clinical chemistry and medicine another matter is denoted by sensitivity , namely the ability of a method to detect truly positive samples as positive (O Rangers and Condon [2000], cited according to Trullols et al. [2004]). However, this seems to be more a problem of trueness than of sensitivity. 

By multisignal evaluation, detection capability can be improved as has been shown for OES and MS by Danzer and Venth [1994] and Venth et al. [1996]. 

Limits characterize the detection capability of analytical methods and can be related to both analytical domains, sample domain as well as signal domain. Although there are several limits, namely lower and upper limits3 as well as thresholds, the most important problem in analytical chemistry is the distinction between real measurement values and zero values or blanks, respectively. 

The term detection capability (detection power) represents a generic term of the performance of analytical methods at the lower limit of applicability. Mostly it is used descriptively (detection capability of a method is high , good or sufficient ) or for giving order of magnitudes (detection capability is in the ppm-range or ppb-range ). 

Figure 7.21 Dendrimers that are fluorescently labeled as well as biotinylated create enhanced detection reagents for use in (strept)avidin-biotin-based assays. Large complexes containing multiple fluorescent dendrimers can bind to antigens and form a highly sensitive detection system that exceeds the detection capability of fluorescently labeled antibodies.

Lanthanide chelates also can be used in FRET applications with other fluorescent probes and labels (Figure 9.51). In this application, the time-resolved (TR) nature of lanthanide luminescent measurements can be combined with the ability to tune the emission characteristics through energy transfer to an organic fluor (Comley, 2006). TR-FRET, as it is called, is a powerful method to develop rapid assays with low background fluorescence and high sensitivity, which can equal the detection capability of enzyme assays (Selvin, 2000). 

Inorganic particles are used extensively in various bioapplications, too. Gold nanoparticles long have been used as detection labels for immunohistochemical (IHC) staining and lateral flow diagnostic testing. These dark, dense particles provide single particle detection capability... 

The feasibility was explored of measuring the lead content in bones of live patients by XRF, using a 99m Tc-labelled radiopharmaceutical as internal standard. The method requires improvement of the detection capabilities of extant instrumentation, since the... 

The conclusion of the section deals with an application of the engineered HRI-coated LPG to chemical sensing. In particular, 8 form sPS layers will be used on the LPG to detect trace amounts of chloroform in water revealing a sub-ppm detection capability. 

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