Edetate, disodium

The most widely used preservative remains benzalkonium chloride, which often is supplemented with disodium edetate. The benzalkonium chloride defined in the USP monograph is the quaternary ammonium compound alkylbenzyldimethylammonium chloride, in which the alkyl portion is composed of a mixture of chain lengths ranging from C8 to C16. This compound s popularity is based, despite its compatibility limitations, on its being the most effective and rapid-acting preservative with excellent chemical stability. It is stable over a wide pH range and does not... 

Lesser et al (75) used cellulose sheets with fluorescent indicator, acetic acid/0.01M aqueous disodium edetate (3 97), and observed an Rf value of O.78 for hydralazine. On silica gel with fluorescent indicator, the Rf value was less than 0.05 with (a) chloroform/n-heptane/ acetic acid (6 4 1), and (b) cyclohexane/chloroform/ acetonitrile (1 2 1). 

Procedure Dissolve 30.0 g in a mixture of 100 ml DW and 35 ml NaOH solution, add 1 ml dimethylaminobenzylidenerhodamine and titrate with 0.0 IN silver nitrate until the colour of the solution changes from yellow to orange. Repeat the operation without the disodium edetate. The difference between the titrations is not more than 1.25 ml. 

TITRABILITY OF POLYVALENT METAL IONS EMPLOYING DISODIUM EDETATE... 

Preparation of 0.05 M Disodium Ethylenediamine Tetracetate Solution (Disodium Edetate 0.05 M)... 

Procedure Weigh accurately about 0.8 g of granulated zinc, dissolve by gentle warming in 12 ml of dilute hydrochloric acid and 5 drops of bromine water. Boil to remove excess bromine, cool and add sufficient DW to produce 200 ml in a volumetric flask. Pipette 20 ml of the resulting solution into a flask and neutralize carefully with 2 N sodium hydroxide. Dilute to about 150 ml with DW, add to it sufficient ammonia buffer (pH 10.0) to dissolve the precipitate and add a further 5 ml quantity in excess. Finally add 50 mg of Mordant Black II mixture and titrate with the disodium edetate solution until the solution turns green. Each 0.003269 g of granulated zinc is equivalent to 1 ml of 0.05 M disodium ethylenediaminetetracetate. 

Materials Required Calcium chloride dihydrate 0.15 g dilute hydrochloric acid (10% w/w of HC1) 3.0 ml 0.05 M disodium edetate sodium hydroxide solution (20% w/v in water) calcon mixture (a mixture of 1 part of calcon with 99 parts of freshly ignited anhydrous Na C ) 0.1 g. 

Materials Required Magnesium sulphate heptahydrate 0.3 g strong ammonia-ammonium chloride solution (6.75 g NH4C1 in 74.0 ml strong ammonia solution add water q.s. to produce to 100 ml) 0.05 M disodium edetate Mordant Black II mixture (mixture of 0.2 part mordant black II with 100 parts of NaCl) 0.1 g. 

Calcium carbonate 0.1 g Calcon mixture Each ml of 0.05 M disodium edetate ee 0.005004 g of CaC03... 

In actual practice, an excess of the standard solution of disodium edetate is added to the sample, pH is adequately adjusted for the residual titration with a metal-ion solution e.g., ZnS04 and employing an appropriate indicator which is sensitive enough to the respective titrant. However, the metal ion under estimation remains firmly complexed with the EDTA and offers little interference with the Zn-EDTA complex formed. It has been established experimentally that bismuth readily yields a highly stable complex which may be titrated conveniently between pH 1 and 2. Bismuth forms a stable complex by reacting with EDTA quantitatively at pH 4.0 and, therefore, dithizone is employed as an indicator to detect the end-point for it has a transition state of colour at pH 4.6. 

Theory The solution of potassium alum is heated with an excess of disodium edetate to ensure complete formation of aluminium-edetate complex. Hexamine serves as a buffer thereby stabilizing the pH between 5 and 6, the ideal pH for the titration of the disodium edetate not required by the A1 with 0.05 M lead nitrate employing xylenol orange as indicator. The various reactions involved may be represented by the following equations ... 

Procedure Weigh accurately 1.7 g of potassium alum and dissolve it in sufficient DW in a flask. Heat the contents of flask over a water-bath for 10 minutes to allow completion of complexation and cool to ambient temperature. Now, add 1 g hexamine to act as buffer and titrate with 0.05 M lead nitrate employing 0.4 ml of xylenol orange solution as an indicator. The colour shall change from that of the indicator (yellow at the pH of the titration) to the corresponding reddish purple, the colour of the lead complex of the indicator. Each ml of 0.05 M disodium edetate is equivalent to 0.02372 g of KA1(S04)2, 12H20. 

Procedure Weigh accurately 0.20 g of glycobiarsol into a 250-ml conical flask and add 10.0 ml of 0.05 M disodium edetate. Warm the contents of the flask over a water-bath until glycobiarsol gets dissolved completely and then cool the contents to the room temperature (25°C). Add to it 10.0 ml of acetic acid-ammonium acetate buffer, 25.00 ml of alcohol and 2 ml of dithizone solution as an indicator. Titrate the excess of disodium edetate with 0.025 M zinc sulphate until the resulting solution turns rose pink in colour. Each millilitre of 0.05 M disodium edetate consumed is equivalent to 10.45 mg of Bi. 

Titrability of Polyvalent Metal Ions Employing Disodium Edetate..164... 

Lead Calcium disodium edetate Forms inactive complete with metal... 

Salt and chelate formation with edetate (ethylenediaminetetraacetate, EDTA). A In a solution of calcium disodium salt of EDTA, the sodium and hydrogen ions are chemically and biologically available. B In solutions of calcium disodium edetate, calcium is bound by coordinate-covalent bonds with nitrogens as well as by the usual ionic bonds. C In the lead-edetate chelate, lead is incorporated into five heterocyclic rings. 

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