Turbidimetric titration

Precipitation and Purification. During the hydrolysis, control tests are made by turbidimetric titration of samples taken intermittently. When the desired degree of hydrolysis is reached, the ester is precipitated from the reaction solution into water. It is important for the precipitate to have the proper texture for subsequent washing to remove acid and salts for thermal stabilization. Before precipitation, the reaction solution is usually diluted with additional aqueous acetic acid to reduce the viscosity. If a flake texture is desired, the solution is poured into a vigorously stirred, 10—15% aqueous acetic acid. To precipitate the acetate in powder form, dilute acetic acid is added to the stirred reaction solution. In both cases, the precipitated ester is suspended in 25—30% aqueous acid solutions and finally washed with deionized water. The dilution, precipitation temperature, agitation, and strength of the acid media must be controlled to ensure uniform texture. 

Turbidimetric titration has also been applied to one-phase titration of alcohol sulfates and other anionic surfactants. The titration is carried out with hyamine 1622 in aqueous solution without the organic phase and indicator and the endpoint is taken as the point of maximum turbidity. The presence of nonionics and inorganic salts at high concentration interfere with the endpoint determination [243]. 

BASIS OF MANUAL TURBIDIMETRIC TITRATION. When a cationic titrant is added to an aqueous anionic surfactant solution a sparingly soluble complex is produced, Scheme 2. 

EXPERIMENTAL PROCEDURES AUTOMATED TURBIDIMETRIC TITRATION. A method for the automated aqueous turbidimetric titration of surfactants has been published (10) in which anionic surfactants are titrated against N-cetylpyridinium chloride to form a colloidal precipitate near the equivalence point. N-cetylpyridinium halides have a disadvantage in that they have the tendency to crystallise out of solution (15), consequently the strength of the solution may alter slightly without the knowledge of the operator, also the crystals suspended in solution may cause damage to the autotitrator. In view of these drawbacks hyamine was preferred as the titrant. 

A typical photometric titration of SDBS against hyamine at low salinity is shown in Figure 3. It was noted, however, that the titration curve was "V" shaped and not the anticipated step curve. The turbidimetric titration of SDBS against hyamine afforded a curve, Figure 4, very similar to that for the photometric titration. 

FIGURE 4 Typical turbidimetric titration of SDBS against Hyamine at low salinity... 

FIGURE 9 Turbidimetric titration SDBS against hyamine. 

CH-8606 Griefensee, Switzerland. Turbidimetric Titration of Anionic Tensides, Mettler... 

There were numerous attempts to apply other qualities proper to macromolecules in the SEC detection, such as turbidimetric titration [304], ebulliometry [305] and osmometry [306], The precise flow-through osmometers would certainly bring enormous progress to polymer HPLC. Their production has been repeatably announced. However, it seems that the technical problems—for example with the preparation of appropriate semi-permeable membranes—connected with the osmometric detection were not yet solved at an acceptable level and the osmometric detectors so far did not appear in the market. 

Hattori, T., Kimura, K., Seyrek, E., Dubin, P.L. (2001). Binding of bovine serum albumin to heparin determined by turbidimetric titration and frontal analysis continuous capillary electrophoresis. Analytical Biochemistry, 295, 158-167. 

The following components of solubility parameters for PPO have been obtained (177) Sd = 16.3 1, Sp = 4.7 0.5, 6h = 7.4 0.5, and So = 18.5 1.2 with units (J/mL)"/2. The determination was based on the use of three mixtures of solvents. For each mixture, the point of maximum interaction between the mixture and the polyol was obtained from the maximum value of the intrinsic viscosity. The parameter 8d measures dispersion 8p, polar bonding 5h, hydrogen bonding and 5q is the Hildebrand solubility parameter which is the radius vector of the other orthogonal solubility parameters. Water solubility of PPO has been determined using turbidimetric titration (178) (Table 7). 

Flow rate I ml/min (note specifications mentioned for the chromatogram shown in Fig. 10). x Solvent composition at precipitation points from turbidimetric titration at 20 °C with n-hexane precipitant and THF solvent. These points determine the boundary of the solubility region... 

It should be noted that the majority of the methods of synthesis of block and graft copolymers yield, in addition to the copolymer, fractions of the associated homopolymers to a greater or lesser extent. Therefore in order to determine the composition and the structure of the copolymer, it is first of all necessary to separate it from any homopolymer which may be present. This separation is usually based upon solubility differences between the different components (203). Although the turbidimetric titration may be very useful for analytical purposes (157), nevertheless it gives samples too small for further examination preparative methods, which are based on fractional precipitation, selective extraction or selective precipitation should be preferred. It is beyond the scope of this review to discuss these separation methods the reader is referred to existing literature concerning this subject (51). 

The initial distribution as determined by turbidimetric titrations of a polymer just form-... 

Fig. 8. Turbidimetric titration curves of PS, PVAc and PVAc-styrene graft copolymer (PVAc-g-PS)...

Turbidimetric titrations were conducted in three ways. In "Type 1" titrations, a mixture of PDMDAAC (0.04-4.0 g/L) and protein (0.1-10 g/L) were combined at pH 4 in distilled deionized water or dilute (0.05-0.5M) NaCl. The optical probe (2 cm path length) of a Brinkman PC600 probe colorimeter (240 nm), and a combination pH electrode connected to an expanded scale pH meter (Orion 811 or Radiometer pH M26), were both placed in the solution. Titrant (0.50 M NaOH or 0.50 M HC1) was delivered from a 2.0 mL microburet (Gilmont) with gentle stirring. Alternatively, turbidity was monitored while a protein solution was added to PDMDAAC (at constant ionic strength) or vice-versa. Turbidity was reported as 100-96T, which is linearly proportional to the absolute turbidity in the range 80<%T<100. 

Typical results for "Type 1 turbidimetric titrations are shown in Figure 1, for BSA and RNAse, in the presence of 0.04 wt. % PDMDAAC at ionic strength 0.2 M. 

Figure 1. "Type 1" turbidimetric titrations for BSA (O) and RNAse (-f-), both 1 g/L, in the presence of 0.4 g/L PDMDAAC and 0.2 M NaCl. Broken line shows evaluation of critical pH.

The interactions of proteins with polysaccharides in solution have been widely investigated using turbidimetric titration, static and dynamic light scattering, electro-... 

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