Filtration phase analysis

With known, the extent of the filtration phase is defined and the corresponding value of interpolated from the t vs. V dataset. L is calculated from equation (4.45) which allows (V )t=t and to be calculated from equa- 

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Following variant II, after treating by the modifier, the solid phase was separated by filtration and additionally washed off with 0.2 liters of water under vacuum of the water-jet pump. Further, as in variant I, one part of the product was dried at 105°C for two hours (product C), while the other was dried at 20°C until a sample mass became constant (product D). The products were investigated by the powder X-ray phase analysis (PXRD) using nickel-filtered CoKa radiation. 

The principal objective of an expression test is to determine the compression deliquoring characteristics of a cake. However, the nature of the test allows both filtration and compression characteristics to be determined when the starting mixture is a suspension (i.e. where the solids are not networked or they are interacting to a significant extent). Cake formation rate, specific resistance and solids volume fraction data can be determined for the filtration phase while analysis of a subsequent consolidation phase allows the calculation of parameters such as consolidation coefficient, consolidation index and ultimate solids concentration in the cake. Repeated use of the expression test over a range of constant pressures allows the evaluation of scale-up coefficients for filter sizing and simulation as described in Section 4.7. 

Two main categories of the wet process exist, depending on whether the calcium sulfate is precipitated as the dihydrate or the hemihydrate. Operation at 70—80°C and 30% P20 in the Hquid phase results in the precipitation of CaSO 2 filterable form 80—90°C and 40% P20 provide a filterable CaSO O.5H2O. Operation outside these conditions generally results in poor filtration rates. A typical analysis of wet-process acid is given in Table 4. For more detailed discussion of the wet-process acid, see Fertilizers. 

A powerful tool now employed is that of diode array detection (DAD). This function allows peaks detected by UV to be scanned, and provides a spectral profile for each suspected microcystin. Microcystins have characteristic absorption profiles in the wavelength range 200-300 nm, and these can be used as an indication of identity without the concomitant use of purified microcystin standards for all variants. A HPLC-DAD analytical method has also been devised for measurement of intracellular and extracellular microcystins in water samples containing cyanobacteria. This method involves filtration of the cyanobacteria from the water sample. The cyanobacterial cells present on the filter are extracted with methanol and analysed by HPLC. The filtered water is subjected to solid-phase clean-up using C g cartridges, before elution with methanol and then HPLC analysis. 

In SEC analysis of additive extracts from polymers, the effect of the extraction solvent on the mobile phase is less critical than in HPLC analysis. The extraction solvents typically employed generally do not interfere with the SEC mobile phases. Moreover, the same solvents are often used both as extraction solvent and as mobile phase. Therefore, there is no need to evaporate the extract to dryness prior to analysis and then to redissolve it in a suitable solvent. Typical extraction procedures often produce extracts that generally contain a small amount of wax. Frequently, removal of such oligomers from an extract is necessary, e.g. by means of precipitation, centrifuging, precolumn filtration or protection (use of a reversed-phase guard column). In SEC separations the presence of polyolefin wax does not usually disturb provided that the MW of the wax is higher than that of the analysed compounds. 

HPLC allows a quantitative determination with relatively simple extractions. In many cases, extraction only involves a heating of the commodity with water, followed by filtration and injection onto an HPLC column. In the determination of caffeine, theobromine, and theophylline in cocoa, coffee, or tea, as well as in other foods, there is scarcely a month that passes without a new paper on this assay. Kreiser and Martin provide typical conditions for analysis.28 In their studies, samples were extracted in boiling water and filtered prior to injection onto the HPLC column. The HPLC conditions used a Bondapak reversed phase column and a mobile phase of water methanol acetic acid (74 25 1) with detection at 280 nm. This method is accurate, precise, and conserves time. It has also been adopted by the AOAC as an official method for the determination of theobromine and caffeine in cocoa beans and chocolate products.29... 

The reaction mixture was stirred for 2h at room temperature until TLC analysis indicated that the reaction was complete. The solution was filtered through Celite and washed with dichloromethane. The filtrate was washed with saturated aqueous NaHC03 and H20. The organic phase was dried (MgS04), filtered and the filtrate was concentrated to dryness. Purification of the crude product by column chromatography over silica gel afforded the target compound. 

In systems where the liquid phase interaction between the solute and solvent is close to ideal, then Eq. 2 can be used successfully on it s own to fit and extrapolate solubility data with respect to temperature. The technique is valuable in an industrial setting, where time pressures are always present. Solubility data points are often available without any additional effort, from initial work on the process chemistiy. The relative volume of solvent that is required to dissolve a solute at the highest process temperature in the ciystallization is often known, together with the low temperature solubility by analysis of the filtrates. If these data points fit reasonably well to the ideal solubility equation then it can be used to extrapolate the data and predict the available crystallization yield and productivity. This quickly identifies if the process will be acceptable for long term manufacture, and if further solvent selection is necessary. 

A separation step is sometimes an essential part of an analytical method and may be as diverse as distillation, filtration, digestion, extraction, phase-separation or dialysis. These can all be performed by continuous flow analysers either by adding a specially designed glass fitting to the manifold or analytical cartridge or by the addition of a separate module to the analyser. Many biological samples contain protein and dialysis is often used to remove this protein, which would otherwise affect the analysis. 

Because of the diaphoretic and laxative effects, the composition of Sambuci flos (Sambucus negra L., black elder) has been extensively investigated by TLC. Samples for TLC analysis were preparated by refluxing 1.0 g of air-dried, powdered flowers of Sambucus negra with 10 ml of methanol for 30 min. The suspension was filtered, and the filtrate was concentrated and redissolved in 5 ml of methanol. Separation was performed on silica layers using 10 different mobile phases 1 = ethyl acetate-formic acid-acetic acid-water (100 11 11 27, v/v) 2 = ethyl acetate-formic acid-water (8 1 1, v/v) 3 = ethyl acetate-formic acid-water (88 6 6, v/v) 4 = ethyl acetate-methyl-ethyl ketone-formic acid-water (50 30 10 10, v/v) 5 = ethyl acetate-methyl-ethyl ketone-formic acid-water (60 15 3 2, v/v) 6 = ethyl acetate-formic acid-acetic acid-methyl-ethyl... 

Gel filtration chromatography carried out on a Sephadex stationary phase has also been employed for pigment analysis. The decolourization of molasses spent wash (MSW) by the white-rot fungus Flavodon flavus was followed with this technique. Untreated and treated MSW samples were diluted up 10 per cent and were loaded into a Sephadex G-50... 

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