Karl Fischer ReagentsAQUAMICRON™

There are two types of coulometric reagents: the anolyte (generating solution),which is placed in the anode chamber of the electrolysis cell, and the catholyte (counter electrolyte), which is placed in the cathode chamber. There are also special anolyte for use with ketones, lower carboxylic acids and silicone oils. AQUAMICRON™ can be used in coulometric moisture measurement systems sold by various companies, and it has a worldwide reputation for excellent performance.

AQUAMICRON™ AXI/CXU or AX/CXU

Use

General samples

Characteristics

• Minimal environmental contamination
  Does not include carbon tetrachloride or chloroform
• Wide range of applications
  Suitable for petroleum products
  Can be used with moisture vaporization method
  (When using AQUAMICRON™ AX or AXI in a moisture vaporization method, replenish the vaporized portion with methanol.)
• High quality, high performance
  Excellent reputation for accurate moisture measurement and end-point stability
  Approximately 800mg of moisture can be measured per 100mL of AQUAMICRON™ AX or AXI, and approximately 150mg per 5mL of AQUAMICRON™ CXU
• Easy to use
  These products can be used in the existing coulometric moisture measurement system.

AQUAMICRON™ AS/CXU

Use

General samples

Characteristics

• Wide range of applications
  Especially suitable for oils, petroleum products
• High quality, high performance
  Excellent reputation for accurate moisture measurement and end-point stability.
  Approximately 800mg of moisture can be measured per 100mL of AQUAMICRON™ AS, and approximately 150mg per 5mL of AQUAMICRON™ CXU.
• Easy to use
  These products can be used in the existing coulometric moisture measurement system.

AQUAMICRON™ AKX/CXU

Use

Ketones, lower carboxylic acids, some aldehydes (aromatics)

Characteristics

• Minimal environmental contamination
  Does not include chloroform or methyl cellosolve
• Wide range of applications
  Suitable for ketones, lower carboxylic acids and some aldehydes
• High quality, high performance
  Accurate moisture measurement, good end-point stability
  Approximately 300mg of moisture can be measured per 100ml of AQUAMICRON™ AKX, and approximately 100mg per 5mL of AQUAMICRON™ CXU (when used with AQUAMICRON™ AKX).
• Easy to use
  These products can be used in the existing coulometric moisture measurement system.

AQUAMICRON™ AXI or FLS

Use

Suitable for alcohols, esters, benzene, toluene, inorganic gases, etc.

Characteristics

• Easy to use
  AQUAMICRON™ AXI or FLS is a single-solution type reagent. It should be used in single-solution electrolytic cells without diaphragm, fritless type cell.
  Can be used with moisture vaporizati on method(When using AQUAMICRON™ AXI or FLS in a moisture vaporization method, replenish the vaporized portion with methanol.)
• Easy maintenance
  Ceramic diaphragm is not used, therefore it is easy to maintain electrolytic cell in good condition.

The items required for volumetric titration are a Karl Fischer titrant and methanol or a dehydrated solvent (used to dissolve or disperse the sample). AQUAMICRON offers a wide range of products suitable for measuring the moisture content of various samples at every levels. Users can select a solvent that is suitable for the samples based on the following tables.

When using a moisture vaporization method, mix Solvent GEX with propylene glycol(PG) in a 3:1 ratio (e.g. 90mL of GEX + 30mL of PG).
When using Solvent KTX, it will be needed to make proper adjustments to the parameters. Please contact a manufacturer of the instruments.
An addition of 3g of salicylic acid enables the time for dehydration to get shorter at the first measurment in combined use of 50mL of Solvent SU.

When using a moisture vaporization method, mix Solvent MS with propylene glycol(PG) in a 3:1 ratio (e.g. 90mL of MS + 30mL of PG).
An addition of 3g of salicylic acid enables the time for dehydration to get shorter at the first measurment in combined use of 50mL of Solvent FM.

• Manufactured at Mitsubishi Chemical Co. which have ISO9001 accreditation.
• According to ISO, GMP, GLP, and FDA guidelines. Traceable to NIST SRM2890.
• Consist of a solvent with specific composition, and exactly confirmed water content. Supplied with Certificate of Analysis.
• Packaged in single-use glass ampoules.
• Long shelf life.

As shown in Formula (1) below, the Karl Fischer method uses Karl Fischer reagent, which reacts quantitatively and selectively with water, to measure moisture content. Karl Fischer reagent consists of iodine, sulfur dioxide, a base and a solvent, such as alcohol.

I2 + SO2 + 3Base + ROH + H2O　⇒　2Base・HI + Base + HSO4R ・・・・・・・ (1)

As described below, this method can be used in both volumetric and coulometric titration systems.

Coulometric Titration
With coulometric titration, the sample is added to an electrolytic solution, the main constituents of which are iodide ions, sulfur dioxide, a base, and a solvent (such as alcohol). Electrolytic oxidation causes the production of iodine, as shown inFormula (2), resulting in an immediate Karl Fischer reaction. 

2I"  -  2e　⇒　I2 ・・・・・　(2)

According to Faraday's laws, the iodine is produced in proportion to the quantity of electricity. This means that the water content can be determined immediately from the coulombs required for electrolytic oxidation.

 1mg of water = 10.71 Coulombs

As shown in Figure 1, two types of coulometric reagents are required: an anolyte, which is placed in the anode chamber of the electrolysis cell, and a catholyte, which is placed in the cathode chamber. Coulometric reagents do not need assessment. Another advantage is that they can be used repeatedly.

Figure1:Electrolysis cell of Coulometric Moisture Meter

Volumetric Titration
A dehydrating solvent suitable for the sample is placed in a flask. Titrant is used to remove all moisture from the solvent. The sample is then added.
Titration is carried out using a titrant, the titer (mgH2O/mL) of which has previously been determined. The moisture content of the sample is determined from the titration volume (mL).
The end point is detected using the constant-current polarization voltage method. Figure 2 shows the components of typical commercially available automatic volumetric titration system.

Figure2:Volumetric Moiture Meter