Filtration and storage

Scarponi et al. [93] used anodic stripping voltammetry to investigate the contamination of seawater by cadmium, lead, and copper during filtration and storage of samples collected near an industrial area. Filtration was carried... 

In order to obtain reliable analytical values, all the items pointed out above should be carefully examined at each step throughout the overall experimental procedures. Sampling, sample collection, filtration and storage... 

In recent years the study of mobile soil and groundwater colloids has received considerable attention because of concerns that such a vector may enhance the mobility of strongly sorbing contaminants, a process that is often referred to as facilitated transport. 15-16 However, our ability to predict colloid movement and deposition is often confounded by the complexities of surface interactions in such dynamic, unstable systems. The lack of universally accepted analytical techniques and failure to realize instrumental limitations have made it difficult to compare and critically evaluate the results of different studies. Artifacts associated with ground-water sampling, filtration, and storage, and the dilute nature of most soil and ground-water suspensions further hamper characterization efforts.17-21... 

Filtration and storage behavior of beer depend strongly on its chemical composition (Table 20.1). Beer production is based on natural ingredients and therefore beer contains a wide variety of chemical compounds. Most chemical components of beer have an influence on beer filtration in general and membrane hltration in particular. Carbohydrates, such as pentosans and (3-glucans, proteins and protein-polyphenol complexes, are of particular importance in membrane hltration of beer, as they are responsible for membrane fouling [3], which has negative consequences on both the hux and quality of the hltered beer, as it will be discussed in detail later on in this chapter. 

Polymer can be delivered in liquid emulsion, water solution, or solid powders. When polymer is in liquid emulsion or water solution, it can be added to injection water using a pump. When it is in solid powder, several processes are needed to prepare the polymer solntion proration, dispersion, maturation, transportation, filtration, and storage (see Figure 5.57). 

Keemling K and Beugmann L (1999) Filtration and storage. In GrasshoffK, Kremling K and Ehrhardt M, eds. Methods of Seawater Analysis. Third edition, pp. 27-40. WUey-VCH, Wein-heim. 

Enzymes can be used to help the starch hydrolysis (typically a-amylases), solve filtration problems caused by P-glucans present in malt (P-glucanases), hydrolyze proteins (neutral proteinase), and control haze during maturation, filtration, and storage (papain, a-amylase, and P-glucanase). 

An estimate of the blank for filtration and storage on-board ship and shore laboratory analytical steps has been determined by passing replicate photo-oxidised seawater samples through the procedure. The mean overall blank was 6/tmol/L DOC with a coefficient of variation of 10 % (n=5), giving a detection limit (taken as 3cr of the blank) of 2 /analytical procedure alone (with no persulphate or blank additions) is about 2 umol/LDOC (Gershey et al., 1979). Replicate analyses of two stored seawaters gave mean DOC concentrations of 57timol/LDOC (coefficient of variation 6.0%, n=30) and 92 /imol/L DOC (coefficient of variation 2.4 %, n=30). 

This analytical approach is problematic. The measurement of DON requires the collection of the samples in duplicate. One sample is used for the analysis of the ambient concentrations of NO3, NO2, and NH4, which is usually carried out within a short time after the sampling. The second sample is used for the analysis of the TDN content after the step of oxidation. Any difference and variability in the filtration and storage procedures of the samples and in the analytical mefliods may result in errors on the determination of DON and TON. Moreover, the accuracy and precision of the result will depend by the efficiency of the oxidation of the organic nitrogen pool in the water samples, by the absence of nitrogen losses or contaminations during the analysis, and by the imcertainties on the analytical determinations. 

Purification commercial CbzCl is typically better than 95% pure and is often contaminated by benzyl chloride, benzyl alcohol, toluene, and HCl. On storage it can undergo a slow HCl-catalyzed decomposition, even at low temperature.It has been recommended that CbzCl which has been stored for long periods be purified by flushing with a stream of dry air to remove dissolved CO2 and HCl impurities. Filtration and storage over Na2S04 may be followed by distillation it is important that low temperatures (oil bath <85 °C) and high vacuum be used to minimize thermal decomposition. ... 

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