Surfactants gravimetric

Little has been published in recent times on gravimetric determination of surfactants. Gravimetric techniques are rather more labor-intensive than other methods, and generally are susceptible to both positive and negative interference. These disadvantages are partially offset by the low cost of the apparatus and the excellent reproducibility which can be attained. They are discussed in this volume mainly because some of the precipitation methods are readily converted to qualitative methods of the go/no-go type for use by plant operators or in the field. 

Gravimetric and volumetric methods are practicable for the quantitative determination of the a-sulfo fatty acid esters. Using gravimetric methods the surfactant is precipitated with p-toluidine or barium chloride [105]. The volumetric determination method is two-phase titration. In this technique different titrants and indicators are used. For the analysis of a-sulfo fatty acid esters the quaternary ammonium surfactant hyamine 1622 (p,f-octylphenoxyethyldimethyl-ammonium chloride) is used as the titrant [106]. The indicator depends on the pH value of the titration solution. Titration with a phenol red indicator is carried out at a pH of 9, methylene blue is used in acid medium [106], and a mixed indicator of a cationic (dimidium bromide) and an anionic (disulfine blue VN150) dye can be used in an acid and basic medium [105]. 

The neutral surfactant is measured after fixing of the ionic substances on a combined anionic/cationic ion exchange column. Volatile substances in the eluate are determined by gas chromatography and nonvolatile substances are measured gravimetrically. In the bulk of the neutral compounds phosphoric acid triesters may be present. This part is additionally determined by atom emission spectroscopy. 

Solid soils are commonly encountered in hard surface cleaning and continue to become more important in home laundry conditions as wash temperatures decrease. The detergency process is complicated in the case of solid oily soils by the nature of the interfacial interactions of the surfactant solution and the solid soil. An initial soil softening or "liquefaction", due to penetration of surfactant and water molecules was proposed, based on gravimetric data (4). In our initial reports of the application of FT-IR to the study of solid soil detergency, we also found evidence of rapid surfactant penetration, which was correlated with successful detergency (5). In this chapter, we examine the detergency performance of several nonionic surfactants as a function of temperature and type of hydrocarbon "model soil". Performance characteristics are related to the interfacial phase behavior of the ternary surfactant -hydrocarbon - water system. 

The composition of surfactant or polar head solutions is expressed in moles of solute in 1 kg of solvent, i.e., molality. Such an unit has two important advantages over the molar concentration. Firstly, it does not depend on the temperature and this facilitates the comparison of experimental results obtained at different temperatures. Secondly, any solution may be prepared by weighing the solute and solvent, or the stock solution and solvent in the case of dilution. The gravimetric procedure markedly increases the precision of the chemical analysis of the bulk phase. 

In a chemical analysis, especially involving quantitative analysis, the amount of chemical used is critical and can be determined by the measurement of concentration if it is a solution, or by weight, if it is a solid. Sometimes, the concentration of a solution can be easily determined by using another known solution through titration. For acids and bases, if the concentration is sufficiently low, the pH concept is generally used to represent the concentration of the acid or base in the aqueous solution. For the analysis of common chemicals, such as caustic soda, acetic acid, soda ash, sodium dithionite, hydrogen peroxide, and so on, titrimetric analysis and gravimetric analysis are widely used. For the analysis of surfactants and other chemicals, qualitative spot tests and specialised instruments should be utilised. 

Gravimetric methods can be used for the determination of all classes of surfactants anionic, cationic, nonionic and amphoteric. 

Analysis by gravimetry is usually more labor-intensive than other methods but is still used because of high reproducibility, simplicity and low cost of the necessary equipment. The disadvantage of gravimetric analysis is its non-specificity. There are no reagents that precipitate only particular surfactants. 

Indirect spectrophotometric methods are in most cases based on the formation of ion pairs that are extractable into organic solvents. These methods are often used in combination with volumetric and gravimetric methods, as many precipitated surfactant complexes can be dissolved in the appropriate solvents and analyzed colorimetrically. The spectrophotometric determination of the end-point in two-phase titration is often carried out. 

When conversion is determined gravimetrically. Interval I may be completed before the first sample is taken. When rates of emulsion polymerization are discussed it is the constant rate fi-equently observed during Interval II which is meant. Most commonly, practically all the emulsifier is adsorbed on the surface of the latex particles at the end of Interval I then the surface concentration of adsorbed emulsifier decreases as the latex particles grow. Soap titration [67], in which the volume of a standard emulsifier solution required to reduce the surface tension of the latex to the value characterizing the presence of micellar soap is determined can be used to determine the final surface concentration of emulsifier. The surface-average particle size can be calculated from a knowledge of the amount of surfactant adsorbed at this point and the area occupied at the interface by a surfactant molecule in a saturated monolayer. This area should... 

Combustion-infrared, persulfate-ultraviolet oxidation, wet oxidation Adsorption-pyrolysis-titrimetric method Partition-gravimetric, partition-infrared, extraction Extraction (total phenols), distillation (volatiles), colorimetry Separation by sublation, methylene blue active substances (MBAS), anionics and cobalt thiocyanate active susbstances (CTAS), nonionic surfactants Chromatographic, distillation... 

At this point, the water-to-oil ratio (WOR) was found to be equal to about 50. Then, tertiary recovery fluid was slowly poured onto the top surface of the sandpack. Once again, the oil recovered from the collector container was measured. Recovered Fuel Oil 2 was measured gravimetrically or volumeflically. For small amounts recovered, an ethylene-propylene-diene monomer (EPDM) absorbent foam was used, which was found to preferentially absorb the Fuel Oil 2 completely from water or water-surfactant within the margin of error of the weighing device of 0.1 g. 

Conversion versus dose curves have been determined for a number of diyne surfactants in the bulk crystalline state, after exposing the crystals to penetrating °Co- y-irradiation. Conversion data were obtained gravimetrically by weighing the amount of insoluble polymer subsequently to solvent extraction of residual monomer from the crystals. 

Transfer the hydrolysed solution after extraction of the fatty alcohol or ethoxylate to a 500 ml volumetric flask, dilute to volume and mix. Use water for this dilution if the gravimetric procedure is to be followed, or acetone for the volumetric procedure. Continue as follows. The volumetric procedure is preferred if other surfactants are present. 

It was demonstrated for system A that although pentanol enhances water solubilization and is present at the interface, its interaction with water or surfactant is not revealed by SZT-DSC. This point has been investigated in the same way as the water-surfactant interaction [10]. We determined the concentrations of pentanol from the measured enthalpy change associated with the pentanol peak and the enthalpy change associated with pure pentanol. The derived concentrations were compared with the actual concentrations determined gravimetrically (see Table 2) [45]. These results suggest that no evidence for interaction of pentanol with water or surfactant can be found in SZT-DSC measurements [10]. 

In parallel, Grossiord et al. demonstrated that three other methods based on Thermo Gravimetric Analysis (TGA), surface tension measurements, and a modified version of the Maron s titration could be used to determine the surface coverage of the CNTs by the SDS surfactant molecules. These methods, as well as... 

Procedure Gravimetric Method for Determination of Total Inorganic Salts in Anionic Surfactants (Alcohol Insoluble Matter)... 

Sodium sulfate is the main inorganic salt expected in sulfonated surfactants. It may also be deliberately added to formulations as a filler or processing aid. Classical methods for sulfate determination are gravimetric or based on BaCl2 titration. It has been found that non-aqueous acid-base titration permits sulfate to be differentiated from sulfonates (18). Sulfate ion has been titrated with lead chloride solution using dithizone as indicator and acetone/water as solvent (19). Alternatively, it may be titrated with barium perchlorate with Sulfonazo III as indicator (9). 

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