Quantification electronic reference

The referencing can also be done by employing an artificial reference resonance. The electronic reference to access in vivo concentrations also known as the (ERETIC) method provides a reference signal, synthesized by an electronic device, which can be used for the determination of absolute concentrations. The ERETIC approach has been applied to ID NMR quantification with high accuracy the standard deviation has been reported to remain imder Michel and... 

The problem of the reference compound is inherent to most chemical concepts. By definition a suitable reference compound is a compound that possesses the same properties as the target compound with the exception of the electronic and structural features to be investigated. In most cases, such a compound cannot be found since changes in the (electronic) structure automatically lead to changes in all properties and hinder meaningful comparison. This is the reason why many chemical concepts are discussed at a qualitative rather than a quantitative level. In fact, as has been forcefully described by Binsch, attempts to quantify a concept very often lead to the collapse of the whole concept. This potential collapse-by-quantification problem exists for the concepts of homoconjugation and homoaromaticity just as it does for the concept of aromaticity. 

Various shape complementarity measures can also be determined based on shape codes. This is an important problem since molecular recognition usually depends on the complementarity of local regions of molecules, where complementarity may refer to electron distributions, polarizability properties, electrostatic potentials, or simply geometric considerations. The powerful topological techniques are suitable for the quantification of the degree of molecular complementarity and can be used as tools for the study of molecular recognition. 

Both reaction kinetics and chemical equilibria of the formation/decomposition of 1,3,5-trioxane in aqueous formaldehyde solutions were studied by quantitative H NMR spectroscopy <2006MI910> a virtual reference signal of high stability was generated electronically and employed for the quantification of the small 1,3,5-trioxane proton signal. 

With most analytical techniques for the quantification of KTB residue levels, chromatographic separations were used, most frequently electron-capture gas chromatography (GC/ECD). With early methods, selected peaks were used to estimate total PCBs. Low-resolution separations were satisfactory when packed columns that produced a pattern of peaks with measured areas were used. The patterns were compared with known amounts of Aroclor mixtures. If the Aroclor peaks in a sample closely resembled a particular Aroclor reference mixture of known weight, the total area or peak height of the sample PCBs was compared to those of the reference mixture and the weight of calculated sample PCBs. Other investigators used selected peaks to report Aroclor equivalents, but these methods are not useful when samples and Aroclor standards are dissimilar. For another procedure, response factors were used for individual Aroclor peaks as determined by GC and GC-MS procedures. The sample peaks were compared with peaks from common Aroclors obtained on packed... 

Tandem mass spectrometry (MS/MS) has attained an enviable status as an analytical tool to identify and quantify compounds in complex mixtures. MS/MS refers to the coupling of two stages of mass analysis, either in time or space. Of all the ionization techniques, only electron ionization (El) provides abundant sttuctural information. To obtain additional structure-specific information by other ionization techniques, it has become essential to perform MS/MS experiments [1,2]. MS/MS was first used in the late 1960s [3]. Since that time, its applications and popularity have continued to grow. Its major contributions are in the fields of structure elucidation of unknown compounds, identification of compounds in complex mixtures, elucidation of fragmentation pathways, and quantification of compounds in real-world samples. In recent times, several new generations of instruments have become available for tandem mass spectrometry applications. Basic concepts of tandem mass spectrometry and an account of these new developments are presented in this chapter. Additional reading material is listed at the end of the chapter. 

Melchert, H.-U. Pabel, E (2004). Reliable identification and quantification of trichothecenes and other mycotoxins by electron impact and chemical ionization-gas chromatography-mass spectrometry, using an ion-trap system in the multiple mass spectrometry mode. Candidate reference method for complex matrices. Journal of Chromatography A, Vol. 1056, No. 1-2, (November 2004), 195-199, ISSN 0021-9673. 

Raman scatter, and excitation emission fluorescence spectroscopy (EEFS). They use interaction with radiation from different regions of the electromagnetic spectrum to identify the chemical nature of molecules. For example, absorption of UV and VIS radiation causes valence electron transitions in molecules which can be used to measure species down to parts per million concentrations for fluorophores (i.e., EEFS) determination can even go down to parts per billion levels. Whereas UV, VIS, and EEFS are limited to a smaller, select group of molecules, the NIR, IR, and Raman scatter spectroscopy techniques are probing molecular vibrations present in almost any species their quantification limits are somewhat higher but can still be impressive. The reader is referred to textbooks for further details on basic principles of these spectroscopic techniques [3]. 

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