Number
348-EN
Section
General Section
Use
Sector
Manufacture of food products
Scientific research and development
Function
Other
Process
Other
Product category
laboratory chemicals
Application
Copper sulphate as alternative to mercury monoxide catalyst
Abstract
The Kjeldahl reaction developed to analyse nitrogen content of organic substances has been reviewed many times to optimise it and make safer for the users. A comprehensive handbook on various Kjeldahl analyses includes a chapter on catalysts that presents alternatives to mercury monoxide.
Substituted substances
Mercury monoxide
CAS No. 21908-53-2 EC No. 244-654-7 Index No.
Chemical group
Mercury compounds; metal oxides
Alternative Substances
Copper sulfate pentahydrate
CAS No. 7758-98-7 EC No. 231-847-6 Index No. 029-004-00-0
Chemical group
Copper compounds; sulfates, hydrogen sulfates, disulfates
Classification: hazard statements
H302 Harmful if swallowed
H315 Causes skin irritation
H319 Causes serious eye irritation
H400 Very toxic to aquatic life
H410 Very toxic to aquatic life with long lasting effects
Reliability of information
Internet information: data are from an internet document and only a basic and partial evaluation could be performed
Reason substitution
CMR
skin/respiratory sensitizing
Hazard Assessment
Substance to be substituted: Mercury monoxide is not included in the EU harmonised classification mercury itself being classified in the EU as reprotoxic cat. 1B. Alternative substance: Copper sulphate is classified as harmful if swallowed, skin and eye irritant and very toxic to aquatic environment with long lasting effects.
Description of Substitution
Kjeldahl reaction, very used in studying protein content in organic matter, initially used mercury monoxide to catalyse sample digestion. Awareness on the hazards for health and environment as well as some process drawbacks lead to the substitution of mercuric monoxide (mercuric oxide). Copper and selenium compounds or their combinations and more recently titanium catalysts are considered safer alternative, with copper sulphate currently being the most commonly used. The handbook containing information on catalyst properties notes that the alternatives give good results, even if the reaction time might be slightly longer than for mercury. Other practical data on the various application of the Kjeldahl reaction and how to carry on different steps of the analysis are presented in the handbook.
Case/substitution evaluation
The substitution eliminates the use of a mercury compound. Mercury itself is a reproductive toxicant. Since the alternative is hazardous to the aquatic environment, protective measures need to be taken. Further substitution alternatives should be found.
State of implementation
In use
Availability ofAlternative
Available on the market
Type of information supplier
Producer / distributor
Contact
Other solutions
Selenium reaction mixture (see Further information) Alternative analytic methods (see Further information)
Further information
Publication source: author, company, institute, year
The description is based on the document Handbook for Kjeldahl Digestion A recent review of the classical method with improvements developed by FOSS , published by FOSS, DK-3400 Hilleroed, Denmark, on its website, in 2008.
Date, reviewed
November 26, 2021