Solvent Injection Method

The production of polymeric nanoparticles by dilution of polymer solutions in water has been described by De Labouret et al. [32], The particle size is critically determined by the velocity of the distribution processes. Nanoparticles were produced only with polar solvents, which distribute very rapidly into the aqueous phase (e.g., 

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Injection of a small aliquot of aqueous phase into surfactant-containing organic solvent (injection method, INJ). 

A similar technique, the so-called spontaneous emulsification solvent diffusion method, is derived from the solvent injection method to prepare liposomes [161]. Kawashima et al. [162] used a mixed-solvent system of methylene chloride and acetone to prepare PLGA nanoparticles. The addition of the water-miscible solvent acetone results in nanoparticles in the submicrometer range this is not possible with only the water-immiscible organic solvent. The addition of acetone decreases the interfacial tension between the organic and the aqueous phase and, in addition, results in the perturbation of the droplet interface because of the rapid diffusion of acetone into the aqueous phase. 

The cosolvent method, also known as solvent injection method permits vesicle formation for glassy or crystalline block copolymers. As a rule, the amphiphilic copolymer is dissolved in an appropriate organic solvent or solvent mixture, the role of which is to lower the Tg below room temperature next the solution is added dropwise to an aqueous buffer under vigorous stirring. Originally this method has been employed for PS-PAA and PS-PEO copolymers that self-assembled in vesicular structures by adding water to DMF or dioxane polymer solution [61,105] and then further applied to many other polymer systems [165],... 

FIGURE 58.4 Schematic representation of the mechanisms of liposome formation (a) film-forming method and (b) organic solvent injection method. (From Zhang, K. et al., Powder TechnoL, 190(3), 39355, 2009.)... 

Clusters of C oN and MePH were prepared by dissolving C oNand MePH in TH F-H2O (2 1) mixed solvent using first injection methods [50]. CfioNand MePH form optically transparent clusters. The formation of nanoclusters of CfioN " "-MePH (diameter about 100 nm) was verified from absorption measurements and AFM. 

Conditions apparatus, Hewlett-Packard HP5890 equipped with an HP5972 mass-selective ion detector (quadruple) column, PTE-5 (30 m x 0.25-mm i.d.) with 0.25- am film thickness column temperature, 50 °C (1 min), increased at 20 °C min to 150 °C(5 min) and then at 4 °Cmin to 280 °C (30 min) inlet and detector (GC/MS transfer line) temperature, 250 and 280 °C, respectively gas flow rate, He carrier gas ImLmin" injection method, splitless mode solvent delay, 3 min electron ionization voltage, 70eV scan rate, 1.5 scanss scanned-mass range, m/z 50-550. The retention times of benfluralin, pendimethalin and trifluralin are 15.2, 25.1 and... 

Chlornitrofen and nitrofen conditions for GC/MS column, cross-linked methyl silicone capillary (12 m x 0.22-mm i.d., 0.33- am film thickness) column temperature, 60 °C (1 min), 18 °C min to 265 °C inlet, transfer line and ion source temperature, 260, 200 and 200 °C, respectively He gas column head pressure, 7.5 psi injection method, splitless mode solvent delay, 3 min electron ionization voltage, 70 eV scan rate, 0.62 s per scan cycle scanned mass range, m/z 100-400. The retention times for chlornitrofen and nitrofen were 11.8 and 11.3 min, respectively. The main ions of the mass spectrum of chlornitrofen were at m/z 317, 319 and 236. Nitrofen presented a fragmentation pattern with the main ions at m/z 283, 202 and 285. ... 

Hot needle or solvent flush method. Rapid injection. Reproduce injection time as close as possible. 

Diffusive sampler Membrane extraction (MESI) Liquid-liquid extraction (LLE) Solid-phase extraction (SPE) SPE-PTV-GC Solid-phase microextraction (SPME) Headspace GC (SHS, DHS) Large-volume injection (LVI) Coupled HPLC-GC Membrane extraction (MESI) Difficult matrix introduction (DMI) Conventional solvent extraction methods 1 Pressurised solvent extraction methods Headspace GC (SHS, DHS) Thermal desorption (TD, DTD) Pyrolysis (Py) Photolysis Photon extraction (LD) Difficult matrix introduction (DMI)... 

Of course, to be able to use the direct injection method of sample introduction, the analyte or the polymer system must be soluble in a solvent. Other methods of sample introduction need to be considered in order to eliminate the involatile material from the chromatographic separation. These have become extremely effective in the analysis of matrices such as polymers. 

Perhaps the simplest solvent dispersion method is that developed by Batzri and Korn (1973). Phospholipids and other lipids to be a part of the liposomal membrane are first dissolved in ethanol. This ethanolic solution then is rapidly injected into an aqueous solution of 0.16M KC1 using a syringe, resulting in a maximum concentration of no more than 7.5 percent ethanol. Using this method, single bilayer liposomes of about 25 nm diameter can be created that are... 

Kaiser [3U used on-line sample preparation to determine trace anions in solvents, including isopropanol, acetone and Af-methylpyrrolidone. A large solvent injection can interfere with both the ion exchange separation and the conductivity detection by causing large disturbances in the baseline. In this application the anions were concentrated on a AG9-HC guard column and then the solvent was sent to waste before it could enter the analytical column. After the solvent was cleared from the AG9-HC concentrator column, the AG9-HC concentrator was switched in line with the AS9-HC analytical column for the separation. The method detection limits for chloride, sulfate, phosphate and nitrate are reported in the sub pg/1 range. 

One of the major drawbacks of liposomes is related to their preparation methods [3,4]. Liposomes for topical delivery are prepared by the same classic methods widely described in the literature for preparation of these vesicles. The majority of the liposome preparation methods are complicated multistep processes. These methods include hydration of a dry lipid film, emulsification, reverse phase evaporation, freeze thaw processes, and solvent injection. Liposome preparation is followed by homogenization and separation of unentrapped drug by centrifugation, gel filtration, or dialysis. These techniques suffer from one or more drawbacks such as the use of solvents (sometimes pharmaceutically unacceptable), an additional sizing process to control the size distribution of final products (sonication, extrusion), multiple-step entrapment procedure for preparing drug-containing liposomes, and the need for special equipment. 

Figure 21-6. Experimental setup of ECP (a), MDM (b), and ADM (c) method for the determination of adsorption isotherms. The concentration-time relation of the dispersed taU in the ECP approach (a) is completely defined by the course of the adsorption isotherm, as can be visuahzed by the injection of increasing samples amounts. Solvent injections at defined concentrations will result in pulses in the MDM approach (b) which are linked to the adsorption isotherms. Although very precise during application of the ADM method, the data points of the adsorption isotherms (c) have to be measnred individually.

Finally, it should be noted that calorimetric measurements can also be used to monitor adsorption phenomena at the solid-liquid interface (in a solvent). This method has been used to measure the adsorption heats evolved upon injection of dilute solutions of pyridine in alkanes ( -hexane, cyclohexane) onto an acidic solid itself in a slurry with -hexane. The amount of free base in solution is measured separately with a UV-Vis spectrometer, leading to an adsorption isotherm that is measured over the range of base addition used in the calorimetric titrations. The combined data from the calorimetric titration and adsorption measurements are analyzed simultaneously to determine equihbrium constants, quantities of sites per gram and acid site strengths for different acid sites on the solid. 

Figure 5 shows an example of the way in which the individual isotherm points were determined Ten minutes after the solvent has been injected into the loop, concentration is determined in the gaseous phase by a flame ionisation detector (FID) or process chromatograph. The gas phase concentration was measured for a maximum of 2 minutes so that equilibrium was disturbed as little as possible. Each individual loading process can be determined after a re-balancing, which takes into accormt the operating conditions, is conducted. Thus, each measurement point is expressed as one point on the adsorption isotherm. The number of measurement points and the distance between them can be influenced by the quantity of the solvent injected. Adsorption isotherms were measured on ACC using the laboratory adsorption unit for concentrations ranging from 10 to 100000 mg/m and in a temperature range of 60°C to 240°C as well as for toluene at 35°C and 45°C (Fig. 6). The new measurement method allows measurements to be performed for a...

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