Detection challenges

Fire prevention may include providing degassing boots/vent stacks to the top of risers where flammable combustible vapors can be entrained in the water system, i.e. water pressure lower than process pressure. Combustible gas detection at the top ofthe vent stacks can be used to detect flammable material presence in cooling tower. However, the hostile environment and difficult to access location makes the detection challenging to maintain. 

The explosives mentioned here are only a few selected from a long list of materials that can be used as explosives. This presents an unusual detection challenge. The chemical and physical properties of explosives vary widely, so it is a challenge to design a sensor that can detect all explosives equally well. One such property is the equilibrium vapor pressure of explosives. From Figure 7.1, which is a plot of the equilibrium vapor pressures of selected explosives at 25°C,... 

In summary, LC-MS offers excellent sensitivity for many classes of pharmaceutical compounds. Due to the fact that MS is becoming more routine (i.e., it is essentially another detector), LC-MS should be the first consideration for all cleaning verification assays that are less than 0.1 pg/swab. In the citations outlined above, LC-MS has been shown to offer excellent sensitivity and specificity for the analytes of interest. The mass spectrometric conditions can be optimized in a flow injection mode to allow for rapid method development. All LC-MS analytical methods were validated in a way consistent with the requirements outlined in Table 15.3. The applications cited utilized LC-MS because of the sensitivity requirements of the safety acceptance limits however, if the molecule of interest poses unique detection challenges such as a poor chromophote, LC-MS should be considered for assays at the level of 1.0 ig/unit area, or less. Above 1.0 xg/unit area there may be more attractive options for these swab determinations. 

As a result of their low vapour pressures, explosives detection in realtime using sniffer technologies presents significant detection challenges. A breakthrough that has enabled a paradigm shift toward explosive vapour detection came in 1998 when our group developed a sensory material with extraordinary sensitivity to TNT and DNT (trinitrotoluene and di-... 

Frost, M.C., Wolf, A.K., Meyerhoff, M.E., 2013. In vivo sensors for continuous monitoring of blood gases, glucose, and lactate biocompatibihty challenges and potential solutions. Detection Challenges in Clinical Diagnostics 2, 129. 

Complex objects such as meat slices are made up of several parts or may have mixed composition compartments, when confronted with this detection challenge an ROI may be chosen to focus spectral analysis on one specific part or compartment. 

The most challenging of these applications has been the location and characterisation of anomalies in thick concrete structures using seismic methods and the detection of reinforcing steel and pre-stressing cables in congested structures using radar. 

Thus we are challenged by the problem of measuring a small signal against the background of one much stronger. The problem is usually solved by one of two means (a) lock-in-amplifier detection and (b) a boxcar type of detection (to some extent we can include double-input optical multichannel detection in this category). 

In chemoinformatics, chirality is taken into account by many structural representation schemes, in order that a specific enantiomer can be imambiguously specified. A challenging task is the automatic detection of chirality in a molecular structure, which was solved for the case of chiral atoms, but not for chirality arising from other stereogenic units. Beyond labeling, quantitative descriptors of molecular chirahty are required for the prediction of chiral properties such as biological activity or enantioselectivity in chemical reactions) from the molecular structure. These descriptors, and how chemoinformatics can be used to automatically detect, specify, and represent molecular chirality, are described in more detail in Chapter 8. 

Methods to Detect and Quantitate Viral Agents in Fluids. In order to assess the effectiveness of membrane filtration the abihty to quantitate the amount of vims present pre- and post-filtration is critical. There are a number of techniques used. The method of choice for filter challenge studies is the plaque assay which utilizes the formation of plaques, localized areas in the cell monolayer where cell death caused by viral infection in the cell has occurred on the cell monolayer. Each plaque represents the presence of a single infectious vims. Vims quantity in a sample can be determined by serial dilution until the number of plaques can be accurately counted. The effectiveness of viral removal may be determined, as in the case of bacterial removal, by comparing the vims concentration in the input suspension to the concentration of vims in the effluent. 

The iaterpretation of forensic toxicology (18) results is often challenging. Courts frequently ask if an amount of dmg detected ia a specimen could cause a specific type of behavior, ie, would someone be under the influence of a dmg at a specific concentration, would a particular dmg concentration cause diminished capacity, or was the dmg the cause of death In a random employee dmg testing case, a worker screened positive for opiates by EMIT and gc/ms analysis of the urine specimen showed low levels of morphine. Although one possibiUty was that the iadividual was a heroia user, a review of foods eaten ia the prior 24 hours suggested a more innocent cause a poppy-seed bagel. 

Since the avermectins exhibit unprecedented potency, they are used at unusually low doses of 6 —300 )-lg/kg, which makes the detection and isolation of residues and metaboUtes from animal tissue a new challenge. For this reason a sensitive analytical assay requires a derivative suitable for detection at concentrations down to 1/10 or 1/100 of one ppm. Ivermectin and avermectin B are therefore converted into an aromatic derivative which allows detection by fluorescence absorbance. To achieve this derivatization, avermectin B, ivermectin, or their derivatives are heated with acetic anhydride in pyridine at 100°C for 24 h (30). The reaction time can be reduced to 1 h by using /V-methylimidazole as a catalyst (31). The resultant... 

Benzodifuranone Dyes. These (BDF) dyes are challenging anthraquiaone dyes. The BDF chromogen is one of the very few novel chromogens to have been discovered ia this ceatury. As with many other discoveries (10) the BDF chromogen was detected by accideat. The... 

Covert Fault Faults that can be classified as hidden, concealed, unannounced, undetected, unrevealed, latent, etc. In the case of safety instrumented systems covert faults impair the intended safeguarding function without being apparent to the operator. Covert faults can only be detected by testing or challenging the system. 

Sample concentration, and hence enrichment, is certainly a key issue in this area of analysis, since complementary information obtained from NMR or IR spectroscopic detection is often desirable in conjunction with mass spectrometry. Detection methods such as these have far higher concentration thresholds than MS and obtaining adequate quantities of material for detection becomes a significant challenge. 

The recent rise in the use of expolosives in terrorist activity poses new challenges to industry and law enforcement. This challenge is being met by the use of sophisticated chemical detection devices to screen for bombs and more rigorous explosive inventory safeguards and controls. Plans have also been proposed to tag explosives with isotopes to make them easier to trace if misused. 

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