Number
076-EN
Section
General Section
Use
Sector
Health services
Function
Other
Process
Other
Product category
laboratory chemicals
Application
Fluorescence-in-situ-hybridisierung (FISH)
Abstract
Formamide is used to denature DNA in Fluorescent In Situ Hybridization (FISH). The specific purpose of the formamide is to make the DNA in the sample single stranded, which allows a probe to bind into the remaining strand. The FISH technique is a method used to locate the presence or absence of specific sequences of DNA in chromosomes.
For the past 15 years the department for clinical genetics at Sahlgrenska University Hospital has substituted the 70% solution of formamide with 30 ml of 1.9% solution of sodium hydroxide and 70 ml of absolute ethanol (99,5%). The substitution works well and the staff has not noticed any specific limitations with the alternative.
Substituted substances
Formamide
CAS No. 75-12-7 EC No. 200-842-0 Index No. 616-052-00-8
Chemical group
Carboxamides
Classification: hazard statements
H360D May damage the unborn child
Alternative Substances
Sodium hydroxide
CAS No. 1310-73-2 EC No. 215-185-5 Index No. 011-002-00-6
Chemical group
Sodium compounds; hydroxides
Classification: hazard statements
H314 Causes severe skin burns and eye damage
Ethanol
CAS No. 64-17-5 EC No. 200-578-6 Index No. 603-002-00-5
Chemical group
Alcohol
Classification: hazard statements
H225 Highly flammable liquid and vapour
Other adverse effects
The substance is: 1 carcinogen (IARC), as listed in the Substance Database according to SUBSPORT Screening Criteria (SDSC).
Reliability of information
Evidence of implementation: there is evidence that the solution was implemented and in use at time of publication
Reason substitution
CMR
Hazard Assessment
The alternatives holds the R-phrases 35, causes burns and 11, flammable, while formamide may cause harm to the unborn child.
Description of Substitution
Formamide has previously been used in Fluorescent In-Situ Hybridization (FISH), a technique used to locate the presence or absence of specific sequences on the DNA. The technique involves the separation of the two DNA strands so that a specifically designed probe can gain access to one of the strands and bind to the desired DNA-sequence. Formamide was previously the chemical of choice to separate the two strands of DNA from each other.
Since 15 years the department of clinical genetics at Sahlgrenska University Hospital has substituted formamide with sodium hydroxide and ethanol in all FISH-analysis's.
The method used when changing from formamide to sodium hydroxide and ethanol is as follows: The FISH-glasses are denaturated using a freshly made solution of 30ml of 1,9% sodium hydroxide solution and 70ml of absolute ethanol (99,5%) for 6 minutes. The FISH-glasses are then dehydrated using the same solution as previously, only ice-cold this time. The dehydration process is then carried out by increasing the ethanol concentration in the sodium hydroxide/ethanol mixture for each step. After the step with an ice-cold solution of 70% ethanol two more steps are carried out, the first one with 90% ethanol and the last one with 100% ethanol.
The advantage with the substitution is that the laboratory don´t need to use formamide anymore which is dangerous and restricted in several ways. The staff of the department have so far not noticed any specific disadvantages of the substitution.
Case/substitution evaluation
Formamide may cause harm to the unborn child, and is not appropriate from a workers health perspective. The alternatives are favourable, but are to be handled carefully due to flammability and the ability to cause burns.
State of implementation
Full capacity
Enterprise using the alternative
Department of clinical genetics, Sahlgrenska University Hospital. http://www.biomedicine.gu.se/ominst/avd/genetik (In Swedish)
Availability ofAlternative
Easily available.
Type of information supplier
User
Research
Contact
Environmental Coordinator at department of clinical genetics, Sahlgrenska University Hospital.
Date, reviewed
February 27, 2020