Karl Fischer Analysis

What Is Karl Fischer Analysis?

The Karl Fischer method is a titration technique based on water reacting selectively with iodine and sulfur dioxide. The amount of iodine consumed is directly related to the number of moles of water. It has two applications: volumetric and coulometric.

Purpose of Karl Fischer Analysis

The purpose is to measure water in the sample separately from other volatile components. The oven-drying method loses all volatiles together; Karl Fischer, since it measures only water, is the only correct approach for samples containing volatiles.

Which Products Is Karl Fischer Analysis Applied To?

Pharmaceutical active ingredients and excipients
Solvents and chemical raw materials
Oils and transformer oil
Plastic granules (pre-processing moisture)
Honey, dried fruit and oily foods

In Which Sectors Is Karl Fischer Analysis Used?

ChemistryPharmaceuticalsFoodCosmeticsEnvironmentPlasticsEnergyOil & Gas

Standards Related to Karl Fischer Analysis

European Pharmacopoeia 2.5.12 / 2.5.32 (semi-micro and micro determination of water)
ISO 760 (determination of water by the Karl Fischer method)
ASTM D6304 (determination of water in petroleum products)
ASTM D1533 (water in insulating liquids)

Karl Fischer Analysis Conditions

Method: Volumetric (high water content) or coulometric (trace water)
Reaktif: Pyridine-free KF reagents; The appropriate formulation is selected for the sample
Sample entry: Direct dissolution or evaporation by oven method
Yan reaksiyon: Special reagent required for samples containing aldehydes and ketones

Equipment for Karl Fischer Analysis

Volumetric and coulometric KF titrators
KF oven unit
Dry air/nitrogen supply system
Precision balance
Water standard ampoules

Sample Requirements for Karl Fischer Analysis

The sample must be sent in a sealed container without absorbing air moisture
As little headspace as possible must be left in the container
Solubility is important for solid samples; the oven method is used if insoluble
The required quantity varies with water content; more sample is needed for trace water determination
The sample's composition must be stated — aldehydes and ketones cause side reactions

Duration of Karl Fischer Analysis

A titration is generally a few minutes. With the oven method and repeat measurements, the analysis can be completed within the same day.

Karl Fischer Analysis Procedure

1The titration cell is dried and a stable baseline is awaited.
2The reagent is titrated with a water standard.
3The sample is weighed and transferred to the cell, or vaporised in the oven and carried over.
4Titration is carried out automatically.
5The amount of water is calculated from the reagent consumed.
6The result is verified with repeat measurements.

Karl Fischer Analysis Acceptance Criteria

The water content limit comes from the pharmacopoeial monograph, raw material specification, or product standard.

Evaluation of Results

Ambient moisture is the main source of error in this analysis; moisture absorbed during sample transfer raises the result. A blank titration and a stable baseline are therefore mandatory. The result is usually given as mass percent or ppm.

Karl Fischer Analysis Report

Sample description, receipt date and laboratory number
Method applied and reference standard, if any
Instrument and measurement conditions
Sample preparation steps
Measurement results and units
Measurement uncertainty (if requested)
A statement that the results relate only to the sample submitted for testing

Accreditation

EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.

Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.

Scope and authorisations

Related Regulations

European Pharmacopoeia and USP monographs
Transformer oil maintenance specifications
Turkish Food Codex product communiqués

Pages Where This Method Is Used

Analytical Methods — What Does This Group of Methods Do?

The section below describes the field that the Karl Fischer Analysis test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.

Analytical method pages are pages about a MEASUREMENT TECHNIQUE rather than about a test. The difference matters: "salt spray testing" is a test and answers one question; "ICP-MS" is a technique and is used in dozens of different tests. Sometimes the user is looking not for the test but for the technique — because the method name is what appears in their specification.

This distinction becomes decisive in choosing a laboratory. When a customer asks for "heavy metal analysis", the real question is by which technique it will be done: XRF is fast and non-destructive but does not distinguish compounds; AAS is economical for a single element; ICP-OES screens multiple elements; ICP-MS sees trace levels. The same sample gives results with different detection limits and different uncertainties across the four techniques.

Method selection is made against three criteria. DETECTION LIMIT: is the concentration sought within the range the method can see? MATRIX COMPATIBILITY: is the sample matrix (plastic, food, soil, metal) one the method can handle, and is pre-treatment required? SPECIFICATION LINK: does the product standard or legislation mandate a particular method? The third often overrides the first two — the specification binds the method.

Method pages build a CHAIN. A technique is linked to the test pages where it is used, to the standards those tests rest on, to the legislation those standards are tied to and ultimately to market access regimes. The example chain in the source document works like this: XRF → metal analysis → RoHS compliance → heavy metal restriction → coating pages. Whichever link the user enters from, they reach the others.

Sample preparation is the invisible half of the result in this family and is a greater source of error than the technique itself. The digestion method, degree of grinding, extraction solvent and dilution ratio change the result markedly. The same sample on the same instrument gives a different result with different preparation; the definition of the method therefore covers preparation too.

Calibration and verification are the third determining component. An instrument is calibrated with certified reference material, the calibration curve is verified periodically and a control sample is run in each batch. Without these steps, a number produced is not traceable even if the instrument is working correctly.

Method groups in this field

Elemental analysis
ICP-OES, ICP-MS, AAS and XRF. They differ in detection limit, matrix tolerance and multi-element capacity.
Chromatography
GC, GC-MS, HPLC, LC-MS/MS and ion chromatography. It separates a mixture into its components and measures each separately.
Spectroscopy
FTIR, Raman, UV-Vis and optical emission. For material identity, functional group identification and alloy composition.
Thermal analysis
DSC, TGA, DMA and dilatometry. Transition temperatures, composition, decomposition and dimensional behaviour.
Microscopy and imaging
Optical microscopy, SEM-EDS, radiography and tomography. Structure, defects and elemental distribution.
Classical (wet) chemistry
Titration, gravimetry and colorimetry. Used as a reference method and in confirming instrumental results.

Commonly confused in this field

XRF is a screening tool; it sees elements and does not distinguish compounds. A decision on a restricted compound requires confirmation by wet chemistry.
The phrase "not detected" is not proof of absence; it is read together with the detection limit of the method.
The specification binds the method. A technically better method is not accepted if the specification calls for another.
Sample preparation is part of the result; a report that does not state the preparation is not reproducible.
Results obtained by different techniques cannot be compared directly; their detection limits and uncertainties differ.
A method page is not a test page; which method applies to which test comes from the product standard.

Which decisions these results support

Matching the method written in the specification to the laboratory's scope
Method selection according to detection limit and matrix compatibility
Confirming an instrumental result with a reference method
Eliminating deviations arising from sample preparation

Related Tests

Frequently Asked Questions About Karl Fischer Analysis

Does it give the same result as oven drying?

Generally not. The oven counts all volatiles as loss; Karl Fischer measures only water. The oven result comes out higher for samples containing volatiles.

Volumetric or coulometric?

If water content is on the order of percent, the volumetric method is suitable; if on the order of ppm, the coulometric method is suitable.