Complexometry

Metal-Chelate Complexes

ComplexometryMetal-Chelate Complexes

                                                              

                                                             

                                                             

                                                              

                                                             

                                                            

                                                              

                                                              

                                                             

                                                             

                                                              

                                                              

                                                              

                                                             

                                                             

                                                             

                                                             

C: unidentatni ligand

B: bidentatni ligand

A: tetradentatni ligand

EDTA: Acid-Base properties

K1=1.02x10-2

K2=2.14x10-3

K3=6.92x10-7

K4=5.5x10-11

                                                              

                                                              

                                                              

Y-4 = [Y-4]

[H6y+2]+[H5Y+]+[H4Y]+[H3Y-]+[H2Y-2]+ [HY-3]+[Y-4]

Y-4 = [Y-4]

[EDTA]

موالر محلول -Y4 غلظت در تا M EDTA 02/0 را pHکه.0/10برابر کنید محاسبه را است شده بافری

[Y4-]=α4CT=(0.35)(0.02) = 7.0x10-3 M

K1=1.02x10-2

K2=2.14x10-3

K3=6.92x10-7

K4=5.5x10-11

pH=6

Indicators

Eriochrome Black T is blue, but turns red in the presence of metals

کاربرد در داروسازی

Ph.Eu.Ph.Eu.0.1 M Sodium edetate.

Dissolve 37.5 g of sodium edetate R in 500 ml of water R, add 100 ml of 1 M sodium hydroxide and dilute to 1000.0 ml with water R.

Standardisation. Dissolve 0.120 g of zinc RV in 4 ml of hydrochloric acid R1 and add 0.1 ml of bromine water R. Drive off the excess of bromine by boiling, add dilute sodium hydroxide solution R until the solution is weakly acid or neutral and carry out the assay of zinc by complexometry (2.5.11).

1 ml of 0.1 M sodium edetate is equivalent to 6.54 mg of Zn.

Storage: in a polyethylene container.

Ph.Eu.Ph.Eu.2. Methods of Analysis

2.5. Assays2.5.11. Complexometric titrations

ZINC

Introduce the prescribed solution into a 500 ml conical flask and dilute to 200 ml with water R. Add about 50 mg of xylenol orange triturate R and hexamethylenetetramine R until the solution becomes violet-pink. Add 2 g of hexamethylenetetramine R in excess. Titrate with 0.1M sodium edetate until the violet-pink colour changes to yellow.

1 ml of 0.1M sodium edetate is equivalent to 6.54 mg of Zn.

CALCIUMIntroduce the prescribed solution into a 500 ml conical flask, and dilute to 300 ml with water R. Add 6.0 ml of strong sodium hydroxide solution R and about 15 mg of calconecarboxylic acid triturate R. Titrate with 0.1M sodium edetate until the colour changes from violet to full blue. 1 ml of 0.1M sodium edetate is equivalent to 2.431 mg of Mg.

MAGNESIUM

Introduce the prescribed solution into a 500 ml conical flask and dilute to 300 ml with water R. Add 10 ml of ammonium chloride buffer solution pH 10.0 R and about 50 mg of mordant black 11 triturate R. Heat to about 40° then titrate at this temperature with 0.1M sodium edetate until the colour changes from violet to full blue.

1 ml of 0.1M sodium edetate is equivalent to 2.431 mg of Mg.

2. Methods of Analysis2.5. Assays

2.5.11. Complexometric titrations

Analiza in nadzor zdravil- vaje 2006/2007

ALUMINIUM

Introduce 20 ml of the prescribed solution into a 500 ml conical flask, add 25.0 ml of 0.1M sodium edetate VS and 10 ml of a mixture of equal volumes of a 155 g/l solution of ammonium acetate R and dilute acetic acid R. Boil for 2 min, then cool. Add 50 ml of ethanol R and 3 ml of a freshly prepared 0.25 g/l solution of dithizone R in ethanol R. Titrate the excess of sodium edetate with 0.1M zinc sulphate until the colour changes from greenish-blue to reddish-violet.

1 ml of 0.1M sodium edetate is equivalent to 2.698 mg of Al.

2. Methods of Analysis2.5. Assays

2.5.11. Complexometric titrations

CALCIUM GLUCONATE

C12H22CaO14,H2O Mr 448.4

Assay

Dissolve 0.8000 g in 20 ml of hot water R, allow to cool and dilute to 300 ml with water R. Carry out the complexometric titration of calcium (2.5.11).

1 ml of 0.1M sodium edetate is equivalent to 44.84 mg of C12H22CaO14,H2O.

MAGNESIUM STEARATE

Definition

Magnesium stearate is a mixture of magnesium salts of different fatty acids consisting mainly of stearic acid [(C17H35COO)2Mg; Mr 591.3] and palmitic acid [(C15H31COO)2 Mg; Mr 535.1] with minor proportions of other fatty acids. It contains not less than 4.0 per cent and not more than 5.0 per cent of Mg (Ar 24.30), calculated with reference to the dried substance. The fatty acid fraction contains not less than 40.0 per cent of stearic acid and the sum of stearic acid and palmitic acid is not less than 90.0 per cent.

Assay

Magnesium. To 0.500 g in a 250 ml conical flask add 50 ml of a mixture of equal

volumes of butanol R and ethanol R, 5 ml of concentrated ammonia R, 3 ml of

ammonium chloride buffer solution pH 10.0 R, 30.0 ml of 0.1M sodium edetate and 15

mg of mordant black 11 triturate R. Heat to 45-50°C until the solution is clear and titrate

with 0.1M zinc sulphate until the colour changes from blue to violet. Carry out a blank

titration.

1 ml of 0.1M sodium edetate is equivalent to 2.431 mg of Mg.

KANAMYCIN MONOSULPHATE

C18H38N4O15S,H2O Mr 601

TESTS

Sulphate 15.0 per cent to 17.0 per cent of sulphate (SO4), calculated with reference to the dried substance. Dissolve 0.250 g in 100 ml of water R and adjust the solution to pH 11 using concentrated ammonia R. Add 10.0 ml of 0.1M barium chloride and about 0.5 mg of phthalein purple R. Titrate with 0.1M sodium edetate adding 50 ml of alcohol R when the colour of the solution begins to change and continue the titration until the violet-blue colour disappears.

1 ml of 0.1M barium chloride is equivalent to 9.606 mg of sulphate (SO4).

Definition

Compound Zinc Paste contains 25% w/w each of Zinc Oxide and Starch in a suitable hydrophobic basis.

Extemporaneous preparation

The following formula and directions apply.

Zinc Oxide, 250 g

Starch, 250 g

White Soft Paraffin 500 g

Melt the White Soft Paraffin, incorporate the Zinc Oxide and the Starch and stir until cold.

The paste complies with the requirements stated under Topical Semi-solid Preparations and with the following requirements.

Content of zinc oxide, ZnO

23.5 to 26.5% w/w.

Identification

The residue obtained in the Assay is yellow when hot and white when cool.

Compound Zinc Paste BP2003

Assay

Heat 0.5 g of the paste gently in a porcelain dish over a small flame until the basis is completely volatilised or charred. Increase the heat until all the carbon is removed. Dissolve the residue in 10 ml of 2M acetic acid and add sufficient water to produce 50 ml. To the resulting solution add 50 mg of xylenol orange triturate and sufficient hexamine to produce a violet-pink colour. Add a further 2 g of hexamine and titrate with 0.1M disodium edetate VS until the solution becomes yellow. Each ml of 0.1M disodium edetate VS is equivalent to 8.138 mg of ZnO.

Compound Zinc Paste BP2003