Esters of carboxylic acids
Esters of carboxylic acids
Esters of carboxylic acid can be analysed analogously to the hydrocarbons according to standard Karl Fischer methods. Long-chain compounds require the addition of solubilisers, e.g. long-chain alcohols or chloroform. Unsaturated compounds can usually be titrated in the same way. Recommended methods are both the volumetric titration with one or two component reagents, as well as the coulometric analysis. The latter is predominantly applied for low water concentrations (< 0.1 %).
Ethyl acetate is easily soluble in alcoholic media. Water determination can be carried out without problems according to standard methods.
Reagents:
Titrant
188005 Aquastar® - CombiTitrant 5 - One component reagent for volumetric Karl Fischer titration, 1 mL = approx. 5 mg water
or
188002 Aquastar® - CombiTitrant 2 - One component reagent for volumetric Karl Fischer titration, 1 mL = approx. 2 mg water
Solvent
50 mL 188008 Aquastar® - CombiSolvent - Methanol-free solvent for volumetric Karl Fischer titration with one component reagents
or
50 mL 188009 Aquastar® - CombiMethanol - Solvent for volumetric Karl Fischer titration with one component reagents, max. 0.01 % water
Titration Parameters:
Default titration setttings, e.g.:
I(pol) = 20 - 50 µA, U(EP) = 100 - 250 mV
Stop criterion: drift < 20 µL/min
Sample size:
10 mL
Procedure:
The titration medium is first placed into the titration cell and titrated dry by means of the titrant. Then the sample is added with a syringe (exact sample weight determination by weighing of syringe before and after injection) or volumetric pipette and the titration is started.
Reagents:
Titrant
188010 Aquastar® - Titrant 5 - Titrant for volumetric titration with two component reagents, 1 mL = approx. 5 mg water
or
188011 Aquastar® - Titrant 2 - Titrant for volumetric titration with two component reagents, 1 mL = approx. 2 mg water
Solvent
null 188015 Aquastar® - Solvent - Solvent for volumetric titration with two component reagents
Titration Parameters:
Default titration settings, e.g.:
I(pol) = 20 - 50 µA, U(EP) = 100 - 250 mV
Stop criterion: drift < 20 µL/min
Sample size:
10 mL
Procedure:
The titration medium is first placed into the titration cell and titrated dry by means of the titrant. Then the sample is added with a syringe (exact sample weight determination by weighing of syringe before and after injection) or volumetric pipette and the titration is started.
Reagents:
Catholyte
5 mL 109255 Aquastar® - CombiCoulomat frit - Coulometric Karl Fischer reagent for cells with diaphragm
Anolyte
100 mL 109255 Aquastar® - CombiCoulomat frit - Coulometric Karl Fischer reagent for cells with diaphragm
Titration Parameters:
Default coulometer settings for cell with diaphragm:
For end point indication, e.g.:
I(pol) = 5 - 10 µA, U(EP) = 50 - 100 mV
Stop criterion: drift < 10 µg/min
Sample size:
1 mL
Procedure:
The Karl-Fischer reagent is placed into the cathode and anode compartment of the titration cell with diaphragm. The coulometer is started and the solvent is titrated dry. After preliminary titration and stabilisation of drift the sample is injected into the titration cell with a syringe (exact sample weight determination by weighing of syringe before and after injection) and the water determination is started.
Reagents:
Working medium
100 mL 109257 Aquastar® - CombiCoulomat fritless - Coulometric Karl Fischer reagent for cells with or without diaphragm
Titration Parameters:
Default coulometer settings for cell without diaphragm:
For end point indication, e.g.:
I(pol) = 5 - 10 µA, U(EP) = 50 - 100 mV
Stop criterion: drift < 10 µg/min
Sample size:
1 mL
Procedure:
The Karl-Fischer reagent is placed into the titration cell without diaphragm. The coulometer is started and the solvent is titrated dry. After preliminary titration and stabilisation of drift the sample is injected into the titration cell with a syringe (exact sample weight determination by weighing of syringe before and after injection) and the water determination is started.
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