Turbidimetric measurements

Phase diagrams of a polyacrylate-phosphonate system with temperature and calcium ion concentration can be established with turbidimetric measurements [1830]. Conductometric titrations also are suitable to characterize the phase behavior of scale inhibitors [514] (Table 7-2). 

Nephelometric and turbidimetric measurements may be made with a fairly reasonable accuracy and precision by using either standard instruments available commercially or by improvising other similar devices. A brief description of such available means shall be discussed below ... 

Other teehniques used for studying molecular interactions between polymers and mueus inelude ultracentrifugation, surface plasmon resonance, and electromagnetic transduction [4,34]. Ilium and co-workers [35] investigated the interaction of chitosan microspheres using turbidimetric measurements and adsorption studies of mucin to the mierospheres. 

Polyacrylonitrile was ground under a constant pressure of one atm with vinyl chloride and with butadiene to give graft and block copolymers as well as minor amounts of homopolymer in the first system (27). The products were characterized by chemical and infrared analysis, viscometric and turbidimetric measurements, and solubility. The results are reported in Table 4. 

A number of composition analyzers used for process monitoring and control require chemical conversion of one or more sample components preceding quantitative measurement. These reactions include formation of suspended solids for turbidimetric measurement, formation of colored materials for colorimetric detection, selective oxidation or reduction for electrochemical measurement, and formation of electrolytes for measurement by electrical conductance. Some nonvolatile materials may be separated and measured by gas chromatography after conversion to volatile derivatives. 

Rossi, S., Ferrari, F. Bonferoni, M.C. and Caramella, C. (2000) Characterization of chitosan hydrochloride-mucin interactions by means of viscosimetric and turbidimetric measurements. Eur. J. Pharm. Sci. 10 251-257. 

A short report demonstrated the absence of a reliable correlation between kiUing kinetics and normal laboratory tests for pristinamycin susceptibility testing of some pneumococci (42). Eight selected multiresistant clinical isolates and two reference pristinamycin-resistant Streptococcus pneumoniae strains were studied. Disk diffusion susceptibility and MICs were determined by the agar dilution method, and all clinical isolates appeared to be susceptible to pristinamycin, whereas the two reference strains were not. In contrast, time-kill experiments identified a limited bactericidal effect of pristinamycin in three clinical and both reference strains. These three strains had been classified as pristinamycin-resistant by the Vitek-II system, which uses a kinetic turbidimetric measurement of bacterial growth. Epidemiological information is hindered by the use of highly selected strains for the study. 

The analysis of growth kinetics allows calculations of mutation frequencies and assessment of overall toxicity of tested compounds. Although this assay provides streamlined protocol and can be fully automated, the turbidimetric measurements of cell density are not highly sensitive or accurate. 

Turbidimetric measurements are easily performed on photometers or spectrophotometers and require little optimization. The principal concern of turbidimetric measurements is signal-to-noise ratio. Photometric systems with electro-optical noise in the range of 0.0002 absorbance unit or less are useful for turbidity measurements. ... 

The first reported method of analysis for halo-thane in blood was by turbidimetric measurement. Halo-thane was extracted from blood with petroleum ether. 

Brun, E., F. Lingaas, and H. J. Larsen. 1989. Turbidimetric measurement of immunoglobulin G in serum using an automatic centrifugal analyzer. Research in Veterinary Science 46 168-171. 

The formazine turbidity unit is defined as the concentration of a standard suspension of formazine. Formazine is a polymeric reaction product of hydrazine sulphate and hexamethylenetetramine. The suspension formed by a reaction of 1.25 mg 1 of hydrazine sulphate and 12.5 mg 1 of hexamethylenetetramine has a turbidity of one formazine unit. Calibration by nephelometric or turbidimetric measurement is carried out so that the relation 1 FT = 1 mg 1 Si02 is valid. 

Stackman and Hurley (49) used turbidimetric measurements and dissolution experiments to characterize the aqueous solubility characteristics of various acrylate-acrylic acid copolymers prepared by solution polymerization in methanol. When phase diagrams of percent neutralization versus percent acrylic acid were generated, the phase boundaries for solubility fell on nearly the same line. This result allowed approximation of the neutralization requirement for other acrylate ester-AA copolymers. 

Transition temperatures were determined Irom turbidimetric measurements or dillerential scanning calorimetry. 

Fig. 5.4 Analysis of the kinetics of the dispersion polymerization by turbidimetric measurements. The turbidimetry measured at different wavelengths given in the insets is plotted against time [10].

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