Fatty acids, titration

Alkylpolyglycosides acid hydrolysis and extraction of fatty alcohol. Alkanolamides and their ethoxylates acid hydrolysis, extraction of fatty acid, titration of alkanolamine or ethoxylated alkanolamine. 

Fig. 3.1. Fatty acid titration curves (according to Bild et al., 1977). Aqueous solutions (0.1 mol/1) of Na-salts of propionic (1), caprylic (2) and linoleic acids (3) were titrated with 0.1 mol/1 HCl...

Animal fats and vegetable oils are triacylglycerols, or triesters, formed from the reaction of glycerol (1,2, 3-propanetriol) with three long-chain fatty acids. One of the methods used to characterize a fat or an oil is a determination of its saponification number. When treated with boiling aqueous KOH, an ester is saponified into the parent alcohol and fatty acids (as carboxylate ions). The saponification number is the number of milligrams of KOH required to saponify 1.000 g of the fat or oil. In a typical analysis, a 2.085-g sample of butter is added to 25.00 ml of 0.5131 M KOH. After saponification is complete, the excess KOH is back titrated with 10.26 ml of0.5000 M HCl. What is the saponification number for this sample of butter ... 

Amides can be titrated direcdy by perchloric acid ia a nonaqueous solvent (60,61) and by potentiometric titration (62), which gives the sum of amide and amine salts. Infrared spectroscopy has been used to characterize fatty acid amides (63). Mass spectroscopy has been able to iadicate the position of the unsaturation ia unsaturated fatty amides (64). Typical specifications of some primary fatty acid amides and properties of bisamides are shown ia Tables 5 and 6. 

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 amount of the ester sulfonates, besides the mono- and disalt of the a-sulfo fatty acid, can be calculated by two titrations, one in the acid and one in the basic range. In the basic range both sulfonates and carbocylate functionalities are negatively charged and titrated with the cationic surfactant hyamine. In acid medium the RCOOH group is protonated and no longer available for the titration. Since hyamine-methylene blue (acid conditions) titrates only sulfonate and hyamine-phenol red (basic conditions) determines both sulfonates and carbo-cylates, substraction of the titration value with phenol red from the double value of the titration with methylene blue yields only the a-sulfo fatty acid ester. This is the only species of the three which has merely the sulfonate function [106]. 

Cherry and Crandall in 1932 (86) used olive oil as substrate with gum acacia as the emufsTfier. This method has served as the basis for a number of modifications that increased the stability of the emulsion, decreased incubation time and gave better precision. When a serum sample is incubated with a stabilized olive oil emulsion, lipase acts at the interface of substrate and water to hydrolyze olive oil into fatty acid plus diglycerides, and to a small extent to monoglycerides and glycerol. The bile salt sodium deoxycholate activates the reaction. These methods measure the liberated fatty acids by titration with a standardized NaOH solution. An indicator such as phenolphatalein, thymolphthalein or methyl red or a pH meter are used to detect the end point. 

Lippi et. al (87) and Dirstine (88) circumvented titration by converting the liberated fatty acids into copper salts, which after extraction in chloroform are reacted with diethyldithio-carbamate to form a colored complex which is measured photometrically. While the end point appears to be more sensitive than the pH end point determination, the advantages are outweighed by the additional steps of solvent extraction, centrifugation and incomplete extraction when low concentrations of copper salts are present. Other substrates used for the measurement of lipase activity have been tributyrin ( ), phenyl laurate (90), p-nit ro-pheny1-stearate and 3-naphthyl laurate (91). It has been shown that these substrates are hydrolyzed by esterases and thus lack specificity for lipase. Studies on patients with pancreatitis indicate olive oil emulsion is definitely superior to water soluble esters as substrates for measuring serum lipase activity. 

This specification is for butter oil, which is butter with the water removed. The free fatty acid limit is to detect lipolytic rancidity while peroxide value specification is to limit oxidative rancidity. The copper limit arises because copper catalyses the oxidation of fats. The absence of neutralising substances is to prevent a high titration for free fatty acids being covered up by the addition of alkali. 

Fatty acid, MRNi hydrogenation, 32 243-245 Faujasites, 34 160-183 acidic sites, 27 151-154 alkaline and rare earth forms, 27 160-165 amine titration, 27 163 infrared smdies, 27 160-163 surface acidity and catalytic activity, 27 163-165... 

In this work, halogens were added across the double bonds of unsaturated fatty acids (commercial available sunflower oil) to form addition compounds and the degree of uptake was measured. A measured excess of iodine monobrontide (IBr) was allowed to react with the oil in the dark. At the end of a timed period, an excess of K1 was added to convert the remaining IBr to The 1 formed was then titrated with standard thiosulfate. This was a back-titration method. A back-titration blank was also required, where the sample was omitted. The uptake of iodine was calculated... 

The ACV is defined as the number of acid equivalents expressed as mg KOH per g of sample. It may be also expressed as percentage (m/m) of a particular fatty acid in a fat or oil. This parameter usually indicates alterations undergone by hydrolysis, and can be determined by direct titration " . The ACV is used as a standard, for example, ISO 660 or lUPAC 2.201 . The acidity of refined oils is always below 1%, whereas that of virgin oils is higher and variable. In cases of extreme oxidation, free carboxylic acids are produced (Scheme 1, Section ll.A.2.c) that contribute to the ACV. This is the operational principle on which the Rancimat equipment for POV determination is based. 

Long-chain fatty acids are insoluble in water, and their titration curves are concentration-dependent because of the formation of organized aggregates (acid soaps, soap micelles, fatty acid precipitates) which concentrate protons at the surface. At concentrations above the critical micellar concentration, solutions of long-chain fatty acid soaps manifest a diprotic curve when they are titrated from pH 10 to 4 (23). The first... 

Composition. Crystals deposited from ethanol solution as well-formed thin plates. The fatty acid content of the crystals is given in Table I. For all chain lengths the acid content approximates closely that required for 1 to 1 stoichiometry. This is also the case for most of the acid-soaps prepared by the petroleum ether route the low values of titratable acid in some instances are ascribable to the presence of free soap. 

A number of methods are available for following lipase activity. Although numerous modifications and variations have been introduced, the basic methods are (1) titration of the liberated fatty acids, (2) changes in surface tension, (3) colorimetric determination of the fatty acids, (4) use of gas-liquid chromatography, and (5) use of radioactive substrates. Kuzdzal-Savoie (1980) has reviewed the subject. 

Titration. Titration of the fatty acids formed by the action of the milk lipase system has been the most widely used procedure. Titration has... 

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