Particle size dependence solvent type

Another RP-HPLC technique has been applied for the determination of synthetic food dyes in soft drinks with a minimal clean-up. Separation of dyes was obtained in an ODS column (150 x 4 mm i.d. particle size 5 pm). Solvents A and B were methanol and 40 mM aqueous ammonium acetate (pH = 5), respectively. Gradient conditions were 0-3 min, 10 per cent A 3-5 min, to 25 per cent A 5-8 min, 25 per cent A 8-18 min, to 75 per cent A 18-20 min, 75 per cent A. The flow rate was 1 ml/min and dyes were detected at 414 nm. The separation of synthetic dyes achieved by the method is shown in Fig. 3.35. The concentrations of dyes found in commercial samples are compiled in Table 3.21. The quantification limit depended markedly on the type of dye, being the highest for E-104 (4.0 mg/1) and the lowest for E-102 and E-110 (1.0 mg/1). The detection limit ranged from 0.3 mg/1 (E-102 and E-110) to 1.0 mg/ml (E-104 and E-124). It was suggested that the method can be applied for the screening of food colourants in quality control laboratories [113]. 

Supercritical fluid extraction (SFE), microwave-assisted extraction (MAE) and Soxhlet extraction under various experimental conditions were applied for spiked poly(vinyl) chloride samples. Extracted dyes were separated in an ODS column (250 X 4.6 mm i.d. particle size 5 jum) using methanol as the mobile phase. Dyes are well separated by this method as demonstrated in Fig. 3.59. The optimal parameters of the extraction methods are compiled in Table 3.23. Recoveries depended on both the type of extraction method and the chemical structure of the dye. It was found that the highest recovery can be obtained by MAE and the extraction efficacy was the lowest for Solvent red 24 [129],... 

Monolayers of micro- and nanoparticles at fluid/liquid interfaces can be described in a similar way as surfactants or polymers, easily studied via surface pressure/area isotherms. Such studies provide information on the properties of particles (dimensions, interfacial contact angles), the structure of interfacial layers, interactions between the particles as well as about relaxation processes within the layers. Such type of information is important for understanding how the particles stabilize (or destabilize) emulsions and foams. The performed analysis shows that for an adequate description of II-A dependencies for nanoparticle monolayers the significant difference in size of particles and solvent molecules has be taken into account. The corresponding equations can be obtained by using a thermodynamic model developed for two-dimensional solutions. The obtained equations provide a satisfactory agreement with experimental data of surface pressure isotherms in a wide range of particle sizes between 75 pm and 7.5 nm. Moreover, the model can predict the area per particle and per solvent molecule close to real values. Similar equations were applied also to protein monolayers at liquid interfaces. 

Properties Platelet-type crystalline structure. High porosity, high void volume to surface area ratio, low density, large range of particle size. Insoluble in water and organic solvents soluble in hot concentrated sulfuric acid. Water vapor adsorption capacity of expanded vermiculite less than 1%, liquid adsorption dependent on conditions and particle size, ranges 200-500%. Noncombustible. 

The anti-solvent type supercritical precipitation processes described earlier, e.g., GAS, are highly dependent on the solubility (or miscibility) between CO2 and solvent. In the case of CAN-BD, the particle size appears to be affected more by the CO2 to water ratio, and much less by the solubility of CO2 in the water. We plan to do further work in the future to substantiate the correlation shown in Figure 7 by vaiying other pertinent process parameters. 

Antimicrobial activity of chitosan depends on type of chitosan, degree of polymerization, molecular weight, pH and solvent -Chitosan nanoparticles could exhibit superior antimicrobial effect against various micro-organism than chitosan itself -The unique character of chitosan nanoparticles for their positive charge and small particle size is responsible for their potential antibacterial activity and acceptable biocompatibility... 

Achieving a suitable particle size with better yield is important in precipitation polymerization as many parameters affect its mechanism. We have prepared GA based MIPs by the precipitation polymerization and observed the effect of porogen on particle size and specific molecular recognition properties (Pardeshi et al, 2014], MIP, M-lOO prepared in the porogen acetonitrile and MIP, M-75 prepared in a mixture of acetonitrile-toluene (75 25 v/v), resulted in the formation of microspheres with approximately 4 pm particle size and surface area of 96.73 m g and nanoparticles (0.8-1000 nm] and a surface area of 345.9 m g" respectively. The results have shown that effect of toluene on the particle size of MIPs depends on the type of cross-linker used and its solubility parameter. Matching the solubility parameter of solvent mixture and cross-linkers is important to obtain the desired particle size in MIPs. The MIPs selectively recognized GA in presence of its structural analogues. Pure GA with percent recovery of 75 ( 1.6) and 83.4 ( 2.2) was obtained from the aqueous extract of herb Emblica officinalis by M-lOO and M-75, respectively. 

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