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"Toxic Fumes from Guanidine Thiocyanate"


Hi ,

We commonly use a Guanidine Thiocyanate (C2H6N4S) solution (48%w/v) to lyse or inactivate virus and bacteria.

When this solution is poured into Bleach a yellow/brown gas is released. One of my customers inhaled this and was none too pleased. The amounts are small enough that no serious harm was done. We also recommend not to do this and to use a safety hood.

Any idea what gas is released when mixing bleach with Guanidine Thiocyanate? The pH is (6-8) for the Guanidine. Also DTT (dithiothreitol) may be present in very small amounts.


Stuart Geiger
biosystems - San Mateo, California


I'll take a stab at a response. When oxidizing cyanide ion with bleach at pH lower than 11 or so, cyanogen chloride is produced - a nasty gas. I imagine that you're either getting thiocyanogen chloride or chlorine gas at the pH of your solution. I'm glad the quantities were small or the customer would be as dead as the germs!

Debbie Mansperger
- Chandler, Arizona, USA


I wanted to know the answer to this as well, and found it on another website: www.aiha.org/abs04/ps403.htm

Generation of Toxic Gases From Reaction of Guanidine Isothiocyanate-Containing Reagents With Bleach.

S. Paik, X. Wu, Abbott Laboratories, North Chicago, IL; J. Park, Seoul National University, Seoul, Republic of Korea.

Guanidine isothiocyanate (GITC) is commonly used in nucleic acid testing (NAT) applications in clinical laboratories as an agent for denaturing proteins and lysing cells or microorganisms. Bleach, with 5% sodium hypochlorite (NaClO) in solution, is often used as a disinfectant and decontamination agent in such laboratories. During cleanup procedures for spilled GITC-containing reagents or treatment of GITC-containing wastes, if bleach is applied, workers in the vicinity of the area may potentially be exposed to toxic gases. This study examined several gases released from the reaction between NaClO and GITC and addressed concerns regarding the safe handling of GITC-containing reagents. A test chamber was constructed to collect the gases with selected adsorbent tubes, using OSHA- and NIOSH-validated methods. To sample the air as completely as possible, the glass chamber was sealed air-tight with three outlets on the top, one for adding bleach into the reagent solution, one for collecting the resultant gases, and the third one for introducing diluent air. By attaching a Tedlar bag at the tip of the diluent air tubing inside the chamber, the resulting air from the reaction between NaClO and various GITC-containing solutions was collected without suffering makeup gas dilution or significant internal pressure reduction. Results show that while the concentrations of all other gases tested (NO, NO2, CO, and Cl2) were either non-detectable or below the applicable occupational exposure limits (OELs), hydrogen chloride (HCl) and hydrogen cyanide (HCN) were surprisingly found in excess levels, possibly exceeding the OELs in the working environment under certain, worst-case scenarios. The concentrations of HCl and HCN were not significantly affected by a nonionic surfactant, present in some of the reagents. The discovery of HCl and HCN in the reaction gases of GITC and NaClO should contribute to the future safe handling of GITC-containing reagents in NAT laboratories.

Jamie Caffrey
- Minneapolis, Minnesota, USA

November 3, 2008

I came across this thread while searching for possible causes of the toxic fumes that have forced me and my coworkers to abandon our lab for the last four weeks. We are a small biotech company and have very little in the way of hazardous chemicals (EtOH, Isopropanol, typical acids and bases, DMSO, bleach, wescodyne, bacterial media components). We do, however use a Machery-Nagle 96-well PCR purification kit with guanidine thiocyanate in it for gel extractions. We carry out up to 20 96-well plates of gel extractions in any one day, so we use more than the typical lab.

We have experienced dizziness, weakness, shakiness, burning tongue and lips, burning in the lungs and headaches. We seem to have become more sensitive over time, and now simply entering the lab for 30 seconds can set off symptoms. Outsiders coming through the lab may notice an bitter taste or a scratchy throat, but are otherwise unaffected. Our CSO is very skeptical that HCN gas or a guanidine thiocyanate spill could be to blame because of the severity and duration of our problem. However, we can't think of anything else WE could be doing to cause this problem. Does anyone have any experience that might shed light on our problem, or evidence that the guanidine thiocyanate could have such a large and long-lasting effect?

Thanks in advance! Liz

Elizabeth Reczek
- Cambridge, Massachusetts

September 10, 2013

Q. Can anyone demonstrate the reaction mechanism for guanidine thiocyanate and sodium hypochlorite (bleach)? I need to understand the chemical reaction (e.g., arriving at a balanced equation with HCl and HCN as the products). I'm sure this will put me on a watch list somewhere :-(


Michael Riviere
- San Diego, California, USA

May 22, 2014

A. SCN+(aq) + OCl-(aq) + H2O(l) --> HCN(g) + HCl(g) + S + O2(g)

P.S. You forgot to do your maintenance this week. :)

Lauren Westfall Katie Domingue
- San Diego, California

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