Deionised water

In the most common production method, the semibatch process, about 10% of the preemulsified monomer is added to the deionised water in the reactor. A shot of initiator is added to the reactor to create the seed. Some manufacturers use master batches of seed to avoid variation in this step. Having set the number of particles in the pot, the remaining monomer and, in some cases, additional initiator are added over time. Typical feed times ate 1—4 h. Lengthening the feeds tempers heat generation and provides for uniform comonomer sequence distributions (67). Sometimes skewed monomer feeds are used to offset differences in monomer reactivity ratios. In some cases a second monomer charge is made to produce core—shell latices. At the end of the process pH adjustments are often made. The product is then pumped to a prefilter tank, filtered, and pumped to a post-filter tank where additional processing can occur. When the feed rate of monomer during semibatch production is very low, the reactor is said to be monomer starved. Under these... 

Because the corrosion resistance of lead and lead alloys is associated with the formation of the protective corrosion film, removal of the film in any way causes rapid attack. Thus the velocity of a solution passing over a surface can lead to significantly increased attack, particularly if the solution contains suspended particulate material. Lead is also attacked rapidly in the presence of high velocity deionised water. The lack of dissolved minerals in such water prevents the formation of an insoluble protective film. In most solutions, lead and lead alloys are resistant to galvanic corrosion because of the formation of a nonconductive corrosion film. In contact with more noble metals, however, lead can undergo galvanic attack which is accelerated by stray electrical currents. 

Cellex D and other anionic celluloses are washed with 0.25M NaCl/0.25M NaOH solution, then twice with deionised water. This is followed with 0.25M NaCl and then washed with water until chloride-free. The Cellex is then equilibrated with the desired buffer as above. 

Heavy metal contamination of pH buffers can be removed by passage of the solutions through a Chelex X-100 column. For example when a solution of 0.02M HEPES [4-(2-HydroxyEthyl)Piperazine-l-Ethanesulfonic acid] containing 0.2M KCl (IL, pH 7.5) alone or with calmodulin, is passed through a column of Chelex X-100 (60g) in the K" " form, the level of Ca ions falls to less than 2 x 10" M as shown by atomic absorption spectroscopy. Such solutions should be stored in polyethylene containers that have been washed with boiling deionised water (5min) and rinsed several times with deionised water. TES [, N,N, -Tetraethylsulfamide] and TRIS [Tris-(hydroxymethyl)aminomethane] have been similarly decontaminated from metal ions. 

Silica [7631-86-9 (colloidal)-, 112945-52-5 (fumed)]. Purification of silica for high technology applications uses isopiestic vapour distillation from cone volatile acids and is absorbed in high purity water. The impurities remain behind. Preliminary cleaning to remove surface contaminants uses dip etching in HF or a mixture of HCl, H2O2 and deionised water [Phelan and Powell Analyst 109 1299 1984],... 

Immersed aluminium and its alloys have excellent resistance to attack by distilled or pure condensate water, and are used in industry in condensing equipment and in containers for both distilled and deionised water, as well as in steam-heating systems... 

Rinse sodium hydroxide pellets rapidly with deionised water this removes the carbonate from the surface. A solution prepared from the washed pellets is satisfactory for most purposes. 

It should also be emphasised that unless otherwise stated all reagents employed in the analytical procedures should be of appropriate analytical grade or spectroscopic grade materials. Similarly, where solutions are prepared in water this automatically means distilled or deionised water from which all but very minor impurities will have been removed. 

Normal laboratory glassware must first be washed and cleaned. It has to be rinsed with deionised water. The clean glassware is sterilised in an oven set at 200 °C for 1 1 hours. It is suitable to cover glassware with aluminum foil to maintain aseptic conditions after removing the glassware from the oven. If aluminum foil is not available, special heat-resistant wrap paper can be used. The sterile glassware must be protected from the air, which has micro-flora, or any contaminants. Avoid the use of any plastic caps and papers. Detach any labelling tape or other flammable materials, as they are fire hazards. 

Selenium precursor stock solution was prepared by adding 0.32 mmol of selenium powder to 20 mL deionised water in a three-necked flask. Sodium borohydride (0.81 mmol) was carefully added to this mixture and the flask was immediately purged with nitrogen gas to create an inert environment. The mixture was then stirred for 2 h, at room temperature. The entire selenium dissolves in water giving rise to a colourless selenium solution. The cadmium solution was prepared by adding 0.32 mmol of CdCb powder in 20 mL of deionised water. The zinc solution was prepared by dissolving 0.32 mmol ZnCb in 20 mL of... 

Removal of starch impurities About lOOmg of the extracted pectic fractions were dissolved in 30ml of NaOH 0.05M and stirred for 20h at 0°C. The solutions were neutralised by the addition of 0.18ml glacial acetic acid and the pH was adjusted to 4.6. After the addition of I ml of an amyloglucosidase solution (60U/ml) without any detectable side activities, the samples were incubated at 60°C for 3h. Finally, the samples were cooled to room temperature, dialysed (cut-off 12000D) against deionised water (4 C) for 72h and freeze-dried. 

Distilled or deionised water contains small amounts of organic impurities which can cause problems in long term use with bonded phase columns in the reverse phase mode. The non-polar stationary phase will collect these organics, which can alter the nature of the stationary phase or sometimes produce spurious peaks (Fig. 4.3c is an example of this). Water purification can be done by distillation from permanganate, by passage of the water through bonded phase columns, or by means of commercial systems, eg the Milli-... 

To examine the oxidation of Fe2+ to Fe3+, in the second experiment, 10 ml solution of 0.1 M ferrous ammonium sulphate was taken separately in four different beakers and sonicated for 15, 30, 45 and 60 min, before transferring the solution to a 25 ml volumetric flask and adding to it 10 ml of 0.01 M KSCN and making upto the mark with deionised water. The absorbance of these solutions was measured at 4-,iax 451 nm. Sonication of ferrous ammonium sulphate solutions oxidised ferrous ions to ferric ions, which in the presence of thiocyanate ions, produced an intense red coloured complex Fe(SCN)63, in proportions to the oxidation of ferrous ions to ferric ions, as could be seen in Fig. 10.1. 

Prebiotic chemistry must cope with many problems a particularly difficult one is contamination. Prebiotic experiments often lead to the formation of important molecular species in extremely low concentrations. The successes of the synthesis may sometimes appear sensational, but there is always the danger that artefacts may be involved. Control experiments carried out with ultrapure deionised water showed that, at higher temperatures (>373 K), synthetic polymers in components of the apparatus could provide a source of organic contaminants such as formate, acetate or propionate ions. Stainless steel had a catalytic effect on the decomposition of formate, so that the use of titanium alloys in the apparatus is recommended. 

In a second experiment, Cy5-labelled antiBSA antibodies were immobilised on a silanised glass slide precoated with metallic nanoislands using a polydimethylsiloxane (PDMS) flow-cell. The antibody solution was left for 1 hour to attach and then the cell was flushed with deionised water. The slide was then dried with N2. For this experiment, a portion of the slide was not coated with metallic nanoislands, in order to act as a reference. Figure 20 shows the image recorded using the fluorescence laser scanner mentioned previously. The enhancement in fluorescence emission between those areas with and without nanoislands (B and A, respectively) is again evident. For both chips, an enhancement factor of approximately 8 was recorded. There is considerable interest in the elucidation and exploitation of plasmonic effects for fluorescence-based biosensors and other applications. 

Table 1. Air/water/surface contact angles measured using the Wilhelmy plate method on surfaces incubated with deionised water for 10 minutes.

Spencer and Brewer [144] have reviewed methods for the determination of nitrite in seawater. Workers at WRc, UK [ 145] have described an automated procedure for the determination of oxidised nitrogen and nitrite in estuarine waters. The procedure determines nitrite by reaction with N-1 naphthyl-ethylene diamine hydrochloride under acidic conditions to form an azo dye which is measured spectrophotometrically. The reliability and precision of the procedure were tested and found to be satisfactory for routine analyses, provided that standards are prepared using water of an appropriate salinity. Samples taken at the mouth of an estuary require standards prepared in synthetic seawater, while samples taken at the tidal limit of the estuary require standards prepared using deionised water. At sampling points between these two extremes there will be an error of up to 10% unless the salinity of the standards is adjusted accordingly. In a modification of the method, nitrate is reduced to nitrite in a micro cadmium/copper reduction column and total nitrite estimated. The nitrate content is then obtained by difference. 

Halliday et al. [396] have described a simple rapid graphite furnace method for the determination of lead in amounts down to 1 xg/l in polluted seawater. The filtered seawater is diluted with an equal volume of deionised water, ammonium nitrate added as a matrix modifier, and aliquots of the solution injected into a tantalum-coated graphite tube in an HGA-2200 furnace atomiser. The method eliminates the interference normally attributable to the ions commonly present in seawater. The results obtained on samples from the Firth of Forth (Scotland, UK) were in good agreement with values determined by anodic stripping voltammetry. 

Campbell and Ottaway [672] have described a simple and rapid method for the determination of cadmium and zinc in seawater, using atomic absorption spectrometry with carbon furnace atomisation. Samples, diluted 1 + 1 with deionised water, are injected into the carbon furnace and atomised in an HGA-72 furnace atomiser under gas-stop conditions. A low atomisation temperature... 

Mean percent total method recoveries and relative standard deviations (n — 3) of benzalkonium homologues obtained after the percolation of 50 mL of deionised water, tap water and wastewater samples spiked at 0.1625 p.gL 1 with benzalkonium chloride through Hysphere and PLRP-s cartridges... 

Soak in filtered deionised water Develop (1 3 D19b to deionised water)... 

Dilute poly-L-lysine 1 10 with sterile deionised or double deionised water. 

In an experiment to determine the percentage by mass of manganese in a steel paper clip, it is necessary to prepare various concentrations of standard potassium permanganate solutions. You will learn more about this experiment on p. 88. A standard 0 0010 mol h solution of potassium permanganate is often used as a stock solution in this experiment. Dilutions of the stock solution are prepared by accurately transferring a known volume of the stock solution, using a pipette or a burette, into a volumetric flask (standard flask). The flask is then carefully filled to the graduation mark with deionised water. 

Table 16.7 shows the depletion of alkylphenols from crude oil, by dissolution in water, after equilibration of the crude oil with deionised water at a pressure of... 

Bennett and Larter (1997) also studied the solvation of alkylphenols in crude oil-water systems at equilibrium to obtain partitioning coefficients under variable temperature, pressure, and water salinity concentration. Alkylphenol depletion from crude oil, expressed by phenol, cresols, and 3,5 dimethyl phenol, versus temperature in a range of 25-125°C, is given in terms of partition coefficient (P) values (Fig. 16.22). Partition coefficient values increase with addition of alkyl groups to the phenol nucleus. Note that the alkylphenol partition coefficient curves for different isomers tend to converge at higher temperatures and, as a consequence, differences between phenol and p-cresol decrease with increases in temperature. Similar results for oil-deionised water and oil-brine experiments show that increasing temperature leads to a decrease in partition coefficient values. 

Fig. 16.22 Plot of partition coefBcient, P, vs. temperature for alkylphenol (O), m- (A). p-(0), o- ( ) cresols, and 3,5-DMP ( ) after 1 1 equilibration of Miller oil and (deionised) water at 25 bars. Reprinted from Bennett B, Barter SR (1997) Partition behaviour of alkylphenols in crude oil brine systems under subsurface conditions. Geochim Cosmochim Acta 61 4393-4402. Copyright 1997 with permission of Elsevier...

Recently, it has been shown that Au in soil can be dissolved using deionised water, the most benign of lixiviants (Gray et al. 1999). The reason for this is not clear either (i) Au occurs in a soluble form within the soil, and/or (ii) deionised water is dissolving an adsorbed ligand in the soil such as cyanide that subsequently dissolves metallic Au. Notwithstanding these uncertainties, use has been made of this previously recognised soluble Au characteristic in soil by mineral exploration and analytical companies, to provide a possible vector towards mineral deposits. 

Samples from the entire profile were analysed for soluble Au using deionised water, iodide (0.1 M Kl) and cyanide (2000 ppm KCN) in a sequential digest using activated carbon to precipitate the Au (details of method found in Lintern Butt (1992)). 

Practical considerations and implementation. Most investigations involve the use of distilled/deionised water with KNO3 as the nitrate ion source thereby avoiding any potential impact of water hardness and dissolved salts on the catalytic removal of nitrates. It has been pointed out that in the presence of anions such as S04 and bicarbonates, which may be present in tap-water at concentrations of above 90 ppm, reduced nitrate reduction rates are to be expected as a result of competitive anion adsorption. Pintar and co-workers have indicated that nitrate removal rates are reduced when using drinking water as opposed to distilled water. Chloride ion is known to reduce the rate of nitrate removal while the choice of cation as counter ion influences the rate in the order, < Na < Ca < Mg + <... 

Analysis of antioxidant activity by performing a FRAP assay was proposed by Benzie and Strain [23]. It involves colorimetric determination of the reaction mixture in which the oxidants contained in the sample reduce Fe ions to Fe. At low pH, Fe(in)-TPTZ (ferric-tripyridltria-zine) complex is reduced to the ferrous (Fe ) form and intense blue colour at 593 nm can be observed. The FRAP reagent is prepared by mixing 2.5 ml of TPTZ (2,4,6-tris (l-pyridyl)-5-triazine) solution (10 mM in 40mM HCl), 25 ml acetate buffer, pH 3.6, and 2.5 ml FeCl3 H20 (20 mM). The colour of Fe(II)(TPTZ)2 which appears in the solution is measured colorimetri-cally after incubation at 37°C. The measurement results are compared to those of a blank sample, which contains deionised water instead of the analysed sample. The duration of the assay differs from one study to another 4 min [23, 24], 10 min [25] to 15 min [26]. The analysis results are converted and expressed with reference to a standard substance, which can be ascorbic acid [26], FeS04 [23, 25], Trolox [27,18]. 

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