Karl Fischer titration is an analytical method for determining small amounts of water in a test sample, such as a solid, a powder or a tissue.
It can be used to determine if the water content of a substance designed for commercial, medical or industrial purposes complies with the associated standards of those purposes.
As described in Chapter of the U. S. Pharmacopeia, Water Determination, the method may involve a commercially available apparatus with an electrical circuit, as well as a reagent, a solvent, and a base.
Steps in the process may include weighing, ascertaining volume, mixing chemical solutions, timing ice baths, and transferring solutions/chemicals to the titration vessel.
Chemicals used in the process
We looked at some of the chemicals involved from a respiratory hazard point of view. As shown in the table below, they’re a tough bunch.
ethylene glycol monomethyl ether
|Short-term and sub-chronic vapor inhalation studies have shown that overexposure to EGME results in adverse effects on testes, bone marrow and lymphoid tissues in laboratory animals|
“Methanol is toxic to humans, and is readily absorbed by ingestion and inhalation, and more slowly by skin exposure.”
Human studies have shown that “repeated exposure to low levels of SO2 (below 5 ppm) has caused permanent pulmonary impairment.“
Our customers who perform Karl Fischer titrations tend to use our Model 300 Winged Sentry, which features adjustable wings that help direct contaminated air toward the unit’s filter chamber.
The model’s open design accommodates the variety of devices, including burettes, necessary for a titration process while the horizontal laminar airflow away from the operator provides respiratory protection from fumes.
Sentry Air designs and manufactures custom hoods in a variety of dimensions and configurations.
For some titration processes, a custom DCH model that may suite your needs is a hood with a lid with two hinges, one in the middle of the lid and another at the top, as shown below.
All models capture hazardous fumes in filters designed to keep the fumes from spreading to the wider laboratory.
For a process that utilizes the chemicals noted above, a Sentry Air Applications Specialist would likely recommend a set of filters that included activated carbon, HEPA and acid gas filtration.
Activated carbon is carbon treated to increase its porosity, effectively creating additional traps for organic volatile substances within the carbon.
HEPA filters, traditionally considered a particle filter because they capture particles as small as .3 microns, can be effective when fumes are carried by airborne particles.
An acid gas filter is made up of activated carbon that has been impregnated with acid-neutralizing chemicals to reduce the concentration (greater that 99%) of acid gases after passing through the impregnated carbon filter media.
Ducted Exhaust hoods
If your process involves significant amounts of methanol, you may want to use an exhaust hood that is ducted to the exterior of the building. Sentry Air offers exhaust hoods in a variety of standard sizes. Our exhaust hoods can also be customized to accommodate titration labware.
For information on fume hood options for your Karl Fischer process, give us a call at 1.800.799.4609, email us at firstname.lastname@example.org, or fill out this online form to have a Sentry Air Systems Applications Specialist contact you to discuss your process.
U. S. Pharmacopeia, chapter 921, water determination
NIOSH Pocket Guide to Chemical Hazards
A website that sells Karl Fischer apparatus also offers a series of informative blog posts, some with video presentations, on different aspects of this method.