Direct fluorimetric analysis

In situ quantitation The direct fluorimetric analysis was carried out under long-wavelength UV light (2e,c = 365 nm Xa > 430 nm, Fig. 1). 

Figure 4.3.1 Schematic diagram of the procedure used for direct front-face fluorimetric analysis of PAHs in fortified Maas river water after adsorption on a tab-shaped element cut from a Cig extraction disk...

In addition to direct metal analysis, indirect analysis for ligands that pull away the metal ion from the fluorescent metal chelate, is also possible. In this case, a decrease in fluorescence is observed. For example, fluoride causes the fluorescence of the alumi-num-Eriochrome Red B complex to decrease. In a similar way, nonfluorescent metal chelates can be used for the fluorimetric analysis of nonfluorescent analytes via a ligand-exchange reaction, according to the scheme shown in Figure 9. In the first step a nonfluorescent complex is formed between a fluorescent chelator and a metal ion. In the next step the addition of the pesticide induces the displacement of the fluorescent ligand and then combines with... 

Diaminopyrimidines are used for antibacterial purposes. Although many of these compounds have some fluorescence, direct analysis is not useful because of the lack of sensitivity. The enhancement of the fluorescence of 2,4-diaminopyrimidines has been accomplished by treatment of the separated components with a solution of ammonium bisulfate [133], A fluorimetric method has also been developed for trimethoprim [2.4-diamino-5-(3,4, 5 -trimethoxybenzyl)pyrimidine] and its metabolites [134] which involves leaving the developed plates to stand for several days and then examining the increase in fluorescence. Amounts of ca. 10 ng could be detected after this time. 

Methods that utilized derivatives (DNP and 7-hydroxyquinoline) combined with colorimetric or fluorimetric detection were not specific for acrolein and consistently did not correlate with those obtained from bioassays. Certain direct methods of detection (nuclear magnetic resonance (NMR), fluorescence, and differential pulse polarography) gave the best correlation to the bioassay results (see discussion of analysis of environmental samples in Section 6.2). 

Postcolumn labeling is a characteristic feature of carbohydrate analysis in which no direct physical methods are available for sensitive detection. Many labeling methods have hitherto been developed. The methods with phenol in sulfuric acid [16], orcinol in sulfuric acid [17], anthrone in sulfuric acid [18], tetrazolium blue in alkali [19], copper(II)-2-2 -bicin-chonitate [20], and 2-cyanoacetamide [21] are used for photometric detection. The methods with 2-cyanoacetamide [6], ethylenediamine [22], ethanolamine [23], taurine [24], and arginine [25] are used for fluorimetric detection. Some labeling methods for electrochemical detection were reported by Honda and Suzuki in 1984 [26,27],... 

In this method the wine sample is filtered through a 0.45 am PTFE cartridge and analysis is performed by direct injection into the HPLC column using a system equipped with a fluorimetric detector operating at excitation and emission wavelengths 225 and 320 nm, respectively... 

Jeuring et al.43 analyzed quinine in soft drinks. By using dodecylsulfonic acid as pairing-ion, a reversed-phase analysis under acidic conditions became possible. This was necessary for the fluorimetric detection of quinine. The method allowed a direct analysis of quinine in soft drinks without extraction. 

Analytical quantification of BAs may be difficult due to the complexity of some food matrices and the low concentrations of BAs generally encountered in the majority of foodstuffs. In addition, the low volatility of these compounds and the lack of chromophores for most of the BAs, does not allow the rapid direct detection by ultraviolet and visible (UV and vis) spectrometric or fluorimetric (FL) methods. In general, in order to obtain an optimal analysis, extraction, clean-up, concentration, and derivat-ization procedures are required. Extraction methods usually based on liquid-liquid or solid-phase extraction with C18 or ion-exchange cartridges can be applied to improve selectivity and sensitivity (Giannotti et al., 2008 Pena-Gallego, Hemdndez-Orte, Cacho, Ferreira, 2009). Alternative approaches, such as solid-phase microextraction... 

Alternatively, direct analysis of nonfluorescent organic ligands by adding an excess of metal ion to form florescent compounds is also possible. Although this derivatization strategy has attractive analytical potential for the analysis of nonfluorescent aromatic compounds, it has received little attention. A typical example includes the fluorimetric determination of anthracyclines and tetracyclines as metal chelates with Mg " ", Ca " ", and Eu + under neutral or alkaline solutions, and with Al + or Zr", under acidic conditions. 

A wide variety of different methods of analysis have been applied to different trace metals in seawater. All these documents are beyond the scope of this article and the reader is referred to Fmrher Reading. In general, the methods fall into two groups those that can be used without preconcentration and those that do require such a procedme. In the first group are spectrophotometric, chemilmninescence, and fluorimetric procedures, electrochemical methods, and some ICP-AES and inductively coupled plasma mass spectrometry (ICP-MS) methods. In the latter group, involving preconcentration, a variety of concentration methods have been used followed by AAS, gas chromatography, mass spectrometry, and neutron activation methods, or indeed any of the direct analysis procedures. These methods will now be briefly discussed. 

FIGURE 4. Analysis of sialic acids from human colon as DMB derivatives by fluorimetric HPLC on RP-18. (a) Sialic acids after direct derivatization with DMB (b) after treatment with influenza C virus (c) after treatment with 0.1 M NaOH (d) after treatment with aldolase. The following sialic acid peaks were identified by comparison with known standards 1, Neu5Ac 2, Neu5,9Ac2 3, higher O-acetylated sialic acids. 

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