Dissolved carbohydrates, analytical

Although the investigations of both Raunkjaer et al. (1995) and Almeida (1999) showed that removal of COD — measured as a dissolved fraction — took place in aerobic sewers, a total COD removal was more difficult to identify. From a process point of view, it is clear that total COD is a parameter with fundamental limitations, because it does not reflect the transformation of dissolved organic fractions of substrates into particulate biomass. The dissolved organic fractions (i.e., VFAs and part of the carbohydrates and proteins) are, from an analytical point of view and under aerobic conditions, considered to be useful indicators of microbial activity and substrate removal in a sewer. The kinetics of the removal or transformations of these components can, however, not clearly be expressed. Removal of dissolved carbohydrates can be empirically described in terms of 1 -order kinetics, but a conceptual formulation of a theory of the microbial activity in a sewer in this way is not possible. The conclusion is that theoretical limitations and methodological problems are major obstacles for characterization of microbial processes in sewers based on bulk parameters like COD, even when these parameters are determined as specific chemical or physical fractions. 

Benzoyl chlorides, like other acyl chlorides, react readily with alcohols to form the corresponding esters (259). The reaction requires 19 h to be completed, and it has been studied in the analysis of carbohydrates, aminosugars, and glycosides (260). Because the preparation of acyl derivatives of monosaccharides is difficult, phenyldimethylsilyl chloride has been also investigated as an alternative label (261). After dissolving the analytes in dimethylformamide and addition of... 

Biodegradation - Enzymes present in the sample can hydrolyze conjugated material and release extra material for analysis or alter the analyte reducing the amount available for assay. Microbial contamination can have a similar effect and can metabolize components of the sample and produce others. This activity can affect dissolved oxygen and carbon dioxide through to nitrogenous compound and carbohydrates. 

On the other hand, DHB is the most common matrix for carbohydrates and classified as "cool" matrix compared with CHCA. For example, DHB solution is paejjared by dissolving DHB in 50% aqueous acetonitrile at 10 mg/mL. 0.5 pL of the DHB solution was mixed on the plate with 0.5 pL of carbohydrate solution dissolved in water. After volatilization of the solvent, solid crystals containing the analytes and DHB are formed. DHB is known to make needle-shaped crystals. Analyte ions are detected from only a few small areas called "sweet spot" or "hot spot". This has made the application of DHB difficult because of long measurement time to find the "sweet spot" and poor reproducibility of the results. 

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