Turbidity measuring

Numerous methods for the deterrnination of monomer purity, including procedures for the deterrnination of saponification equivalent and bromine number, specific gravity, refractive index, and color, are available from manufacturers (68—70). Concentrations of minor components are deterrnined by iodimetry or colorimetry for HQ or MEHQ, by the Kad-Eisher method for water, and by turbidity measurements for trace amounts of polymer. 

The solubiHty of phosphoms in water is about 3 ppm. However, process water used in phosphoms manufacture or handling often catties larger amounts of phosphoms as particulates or small droplets, depending on the water temperature. Phosphoms-contaminated water is commonly called phossy water. Phosphoms has low solubiHty in most common solvents, but is quite soluble in carbon disulfide and some other special solvents. The solubiHty in CS2 and benzene was formerly used in phosphoms analyses, but toxicity and increasing waste disposal costs have led to mote use of toluene and xylene, and mote tecentiy to the use of nonchemical turbidity measurements. 

The microbial assay is based on the growth of l ctobacillus casei in the natural (72) or modified form. The lactic acid formed is titrated or, preferably, the turbidity measured photometrically. In a more sensitive assay, l euconostoc mesenteroides is employed as the assay organism (73). It is 50 times more sensitive than T. casei for assaying riboflavin and its analogues (0.1 ng/mL vs 20 ng/mL for T. casei). A very useful method for measuring total riboflavin in body fluids and tissues is based on the riboflavin requirement of the proto2oan cHate Tetrahjmenapyriformis which is sensitive and specific for riboflavin. 

Brown, C.M., Ackemiann, D.K., Puricli, D.L. and Finlayson, B., 1991. Nucleation of calcium oxalate monoliydrate use of turbidity measurements and computer-assisted simulations in characterising early events in crystal formation. Journal of Crystal Growth, 108, 455 64. 

Flocculation values achieved from turbidity measurements using the light scattering technique showed improvement with nonylphenol ether carboxylic acid (4 mol EO) in particular. The oil solubilization rate has been found to be proportional to the surfactant micellar size [190]. 

Turbidity measurements were determined using the dipping probe colorimeter. The light frequency was 650 nm. Deionized water transmittance was set at 90. The surfactant test solutions were stirred ( — 3500 rpm) and maintained at 75°C. Active surfactant concentration was 0.1% wt. Solution volume was 100 cm1. A 26.5% CaCU (95,699 ppm CaJ+) solution was added via syringe in 0,10 ml increments to the lower portion of the surfactant solution. 

Figure 8a shows the turbidity measurements for different guest residues in ELP [VgX2l. Lower transition temperatures (Tt) correlate with increased hydrophobicity of the guest residue [24, 25]. This data was extrapolated to other ratios of VahXaa (Fig. 8b). The transition temperature could also be influenced by the molecular weight of the ELP. The Tt was shown to increase with decreasing polymer length (Fig. 8c) [23, 26].

Heller and Tabibian (13) noted that errors, due to laterally scattered light and the corona effect, as large as to cause a 30 reduction in measured turbidity, may result if instruments which are perfectly suitable for ordinary absorption measurements are used for turbidity measurements without proper modifications. To evaluate the performance of our turbidity detector, particle suspensions of various concentrations of several polystyrene latex standards were prepared. Their extinction coefficients were measured using both a bench-top UV spectrophotometer (Beckman, Model 25) and the online detector (Pharmacia). 

GC Jeffrey, RH Ottewill. Reversible aggregation Part reversible flocculation monitored by turbidity measurements. Colloids Polymer Sci 266 173-179, 1988. 

It is now well known that the addition of Ca2+ in aqueous solutions of these copolymers induces phase separation with precipitation of a phase constituted by a polymer-Ca complex. From turbidity measurements, it is possible to define a critical concentration ca above which this phenomenon occurs(23-25). 

Figure 2. Effect of pH and time on turbidity measurements for polymer concentration...

The great stability of polymerized vesicles can be demonstrated by several experiments (9) dilution of polymer vesicle solutions with 50% of ethanol does not result in a precipitation. Turbidity measured at 300 nm remains the same (28), whereas monomer vesiclesare destroyed under these conditions followed by a considerable decrease of turbidity. A precipitation of stabilized vesicles can, however, be achieved by the addition of salts (KC1), but again it has to be pointed out that the polymeric vesicles... 

The instrument used in the turbidity measurement was Hatch Model 2100 A Turbidimeter. A Hotech Shaker Bath, Model 901 (Hotech Instruments Corp.) was used in mixing the oil and surfactant solution. The nonionic surfactants, Newcol 1102, 1103 and 1105 were produced by Sino-Japan Chemical Co., Ltd. The active ingredient is dodecanol ethoxylate. Sodium dodecyl sulfate (SDS, No. L. 5750, Sigma Chemical Co. 95% active, containing 65% Cj 2>... 

Some experiments concerning the solubilization of triolein in SDS solutions were done by adding triolein dropwise to the surfactant solution. 15.0 g of 0.5% SDS solution was used. One drop of triolein (0.006 0.001 g) was added to the surfactant solution. The oil was dispersed, shaken and turbidity measured as it was mentioned above. When turbidity reached a constant value, another drop of triolein was added and the process repeated until the turbidity value did not change with the addition of triolein. 

S. Barnes, J. Gillian, A. Diederich, D. Burton and D. Ertl, In process monitoring of polymorphic form conversion by Raman spectroscopy and turbidity measurements. Am. Pharm. Rev., 11, 80, 82-85 (2008). 

Figure 1. Top Turbidity, measured at 350 nm, as a function of microtubule polymer mass concentration (expressed as mg/mL polymerized tubulin). Tubulin solutions of varying concentrations were polymerized until they reached stable plateau values in a Cary 118C spectrophotometer. Each sample was then transferred to an ultracentrifuge tube, and microtubules were pelleted, separated from the unpolymerized tubulin in the supernatant fraction, and then resuspended for protein concentration determination. The corresponding turbidity and polymer mass concentrations are plotted here. Bottom Time-course of tubulin polymerization assayed by turbidity.Repro-duced from MacNeal and Purich with permission from the American Society for Biochemistry and Molecular Biology.

APPL is determined by acid precipitation (12M HC1) using either turbidity measurements (nephelometry abs. at 600 nm) or gravimetry according to Crawford et al. (4). All experiments reported in this paper were carried out with uninoculated controls whose values were always substracted. 

Gales, P. W. (2000). A comparison of visual turbidity with turbidity measured by commercially available instruments. J. Am. Soc. Brew. Chem. 58,101-107. 

Figure 10.19 Effect of pre-added vesicles on the formation of oleic acid/oleate vesicles. Turbidity measured at 500 nm (1 cm path length) is plotted as a function of time, T=2°C. (a) 62 p,l of 80 mM aqueous sodium oleate was added to 2.438 ml of0.2Mbicine buffer, pH 8.8 ([oleic acid/oleate] = 2 mM). (b)62 p,l of 80mM aqueous sodium oleate was added to 2.438 ml of a 2 mM oleic acid/oleate 100 nm vesicle suspension (0.2 M bicine buffer, pH 8.8 ([oleic acid/oleate] = 4 mM). (c) Turbidity of 2 mM oleic acid/oleate 100 nm vesicles , (d) the same as (b), but using a 50 nm vesicle suspension, (e) Turbidity of 2 mM oleic acid/oleate 50 nm vesicles . (Modified from Blochiger etal, 1998.)...

The total concentration of complex formed during the complexation is proportional to X. During template polymerization of acrylic acid, a stable colloidal precipitate resulted in the systems under investigation, and turbidity measurements could be used, assuming that direct reading from the turbidimeter (in logarithmic scale) is proportional to the amount of polymeric product. The assumption was checked by calibration procedure. The light absorption (%) is proportional to the concentration of poly(acrylic acid)-poly(vinyl pyrrolidone) mixture.100% conversion was assumed when no increase in turbidity was detected by the recorder. In the case when copolymers were used as templates, the apparatus was calibrated for each copolymers separately. 

Turbidity measurements, static and dynamic light scattering, and a brief introduction to x-ray and neutron scattering (Chapter 5)... 

In the preceding section we saw how turbidity measurements are made and how they may be analyzed to yield numerical values for some of the parameters of interest in colloid chemistry. Figure 5.7 shows a plot of Hc/t versus c for three different fractions of polystyrene in methylethyl ketone. The measurements shown in the figure were made at 25°C and at a wavelength of 436 nm. The molecular weights for the three fractions may be determined from the intercepts of the lines as illustrated in Example 5.2. 

The first data on polymer systems were collected via (laser-) light-scattering techniques [1] and turbidity measurements, further developed by Derham et al. [2,3]. Techniques based on the glass-transition of the polymer-blend constituents were also tested, such as DSC, Dynamic Mechanical Spectroscopy, and Dielectric relaxation [4]. Films made from solutions of... 

Parker, T. G. and Dalgleish, D. G. 1977A. The use of light-scattering and turbidity measurements to study the kinetics of extensively aggregating protein as-Casein. Biopolymers 16, 2533-2547. 

Lex, D Turbidity Measurement, iu Process/lndustrial Instruments Controls Handbook, D.M. Considine, Editor, 4th Edition, McGraw-Hill, New York, NY,... 

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