Multiple sensitive-point method

Multiple-point fluorescent deteclion has been proposed to enhance detection sensitivity. This method is based on the use of a detector function, such as the Shah function. The time-domain signals were first detected, and they were converted into a frequency-domain plot by Fourier transformation. Therefore, this technique was dubbed Shah convolution Fourier transform detection (SCOFT). As a comparison, the single-detection point time-domain response is commonly known as the electropherogram [698,699,701]. 

There has never been a more exciting time in Toxicology. Never before have we had such a wealth of new ideas and concepts pumped in by the basic sciences, such a multiplicity of new methods and approaches, such sophisticated and sensitive analytical procedures. Our problem is to assimilate and apply all these opportunities, which bid fair to revolutionize the classical approaches to safety evaluation. Hence an even greater source of concern may be expressed thus will we be afforded a breathing-space to develop the new tests to a satisfactory point, before they become a part of government regulation ... 

The traditional acute, subchronic, and chronic toxicity studies performed in rodents and other species also can be considered to constitute multiple end point screens. Although the numerically measured continuous variables (body weight, food consumption, hematology values) generally can be statistically evaluated individually by traditional means, the same concerns of loss of information present in the interrelationship of such variables apply. Generally, traditional multivariate methods are not available, efficient, sensitive, or practical [25]. 

Since the analytical point of view most of current analytical methods are based on LC-MS/MS, but for some classes of pesticides GC-MS continues being the technique of choice. The use of quadrupole ion trap (QIT) to analyze multiple pesticide residues is limited to several multiclass pesticides in fruit [162], because of the limited number of ions that can be isolated at the same time. For this reason, the use of several time windows is required and this is indeed a strong limitation in practice. The use of hybrid triple quadrupole linear ion trap (QqLlT) mass spectrometer has provided significant contribution to the development of high-sensitive multiresidue analytical methods for pesticide control. An example of application is the method reported by Hernando et al. for the analysis of pesticide residues in olive oil [65]. 

The most characteristic abnormality in patients with multiple sclerosis is certainly the intrathecal synthesis of IgG. It can be demonstrated—with different sensitivity— by various methods, which can be divided into qualitative and quantitative methods. The gold standard for the demonstration of intrathecal synthesis of IgG is the detection of oligoclonal bands, which are not present in CSF, in the appropriately diluted serum (i.e., to the same concentration of IgG) by isoelectric focusing. This is a qualitative method and the description of its different modifications and interpretations goes beyond the scope of this chapter. This method is by far the most sensitive, and its sensitivity is reported between 90 and 100%. Here it is suitable to repeat that the detection of plasmocytic forms in cerebrospinal fluid may also be regarded as qualitative proof of intrathecal synthesis of immunoglobulins— although in this case the proof is obviously not specific for IgG from the theoretical point of view. 

Another method, cross-correlation chromatography, was also reported for detection sensitivity enhancement (see Figure 7.12). Multiple injections were performed in a continuous but random sequence. A single point detection output was recorded. This output was correlated with the injection profile. This correlation enhanced the detection sensitivity due to the multiplex advantage [705]. 

A final point of some importance concerns the use of single-reference methods. Density fiinctional theory is often the method of choice in computational transition metal chemistry, simply because it is often the only affordable method that yields a qualitatively accurate description of the PESs. However, it is in some respects a single-reference, method in that it constructs a wavefunc-tion from a single Slater determinant and cannot therefore describe systems that inherently require a representation in terms of multiple determinants, such as low-spin open-shell systems. This makes it inappropriate for treating some regions on PESs, although experience shows that DFT is somewhat less sensitive to this effect than other single-determinant systems. 

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