·       Quinine Is An Important Alkaloid Of Cinchona Offcinalis L. And Is Permitted In Soft Drinks And Tonic Waters. Quinine Is Determined Usually By Fluorimetry But Can Also Be Determined Spectrophotometrically.

Fluorometric Determination Of Quinine In Soft Drinks And Tonic Waters.

Principle

·       Quinine Is Determined By Direct Fluorescence Spectrophotometry After Dilution Of The Sample With Sulphuric Acid.

Apparatus

·       Volumetric Flasks;

·       Beakers;

·       Fluorimeter With 365  Nm Excitation  Filter   And  415  Nm Emission  Filter   Or Spectro Fluorimeter.

Reagents

·       Sulphuric Acid (0.05M): Dilute 2.78 Ml To 1000 Ml With Water.

·       Sulphuric Acid (1M): Dilute 55.6 Ml To 1000 Ml With Water.

·       Standard Solution Of Quinine

Stock Solution

·       Weigh Accurately 50 Mg Of Quinine Or 60.4 Mg Of Quinine Sulphate Dihydrate. Transfer Into A 500 Ml Volumetric Flask, Add 25 Ml Of 1M H2SO4 And Dilute To Volume With Water. Prepare Working Standard Solution By Dilution With 0.05M H2SO4.

Preparation Of Sample:

·       Remove Carbonation By Stirring And Weigh Accurately 5 Gm Of Sample And Dilute To 250 Ml In A Volumetric Flask With 0.05M H2SO4. Pipette 5 Ml Of This Solution And Dilute To 25 Ml Using 0.05M H2SO4.

Procedure

·       Using 365 Nm Excitation Filter And 415 Nm Emission Filter, Adjust The Fluorimeter To Zero With 0.05 H2SO4. Measure The Emission Intensity Of Concentration (µg) VS Emission Intensity. Read The Fluorescence Of The Sample Solution And Calculate The Amount Of Quinine Present In The Sample From The Calibration Curve.

Spectrophotometric Determination Of Quinine In Soft Drinks

·       Principle: Quinine Is Extracted From Soft Drinks Using Chloroform After Making It Alkaline With Sodium Hydroxide. It Is Re – Extracted From Organic Layer With 1N H2SO4. An Aliquot Of Acid Extract Is Adjusted To Ph 1.0, Alizarin Brilliant Violet R Solution Is Added And The Complex Is Extracted Into Chloroform. The Absorbance Of Chloroform Layer Is Measured At 578 Nm. Amount Of Quinine Present In The Sample Is Computed From The Calibration Graph.

Reagents

·       Buffer (Ph 1): Add 0 Ml Of 1.0N Hcl To 50 Ml Of 1.0M Potassium Chloride And Make Upto 1000 Ml.

·       Alizarin Brilliant Violet R (ABVR): 1 × 10-3 M: Prepare In Distilled

·       Quinine Standard Solution: Prepare 1 Mg/Ml By Dissolving Quinine Sulphate In 1N H2SO4. Dilute To A Working Standard Containing 40 µg/Ml.

Procedure

·       Preparation Of Standard Curve: To A 30 Ml Buffer Solution In A 100 Ml Separatory Funnel, Add Aliquot Of Quinine Working Standard Solution, Ranging From 10-200 µg And 5 Ml Of Dye Solution. Adjust The Volume To 50 Ml With Distilled Water. Extract With 10 Ml Of Chloroform. Read The Absorbance Of Chloroform Layer At 578 Nm And Plot The Calibration Graph.

·       Determination In Soft Drinks: Accurately Weigh 50 Gm Of Soft Drink And Transfer To 250 Ml Separatory Funnel. Add 10 Ml Of 10% Naoh And Extract With 3 × 20 L Portions Of Chcl3. Shake The Combined Extract With 3 × 30 Ml Of 1N H2SO4 In Another Separator And Make Up The Acid Solution To 100 Ml In A Volumetric Flask. Taking An Aliquot Of This Solution Proceed As Given Under Preparation Of Standard Curve.