Received on September 23, 2005
Accepted on December 23, 2005

Automation and Analytical Techniques

Determination of Cyanide in Blood by Isotope-Dilution Gas Chromatography-Mass Spectrometry

¹ National Institute of Standards and Technology, Gaithersburg, MD

^* To whom correspondence should be addressed. E-mail: karen.murphy{at}nist.gov.

Background: Cyanide (CN) is a lethal toxin. Quantification in blood is necessary to indicate exposure from many sources, including food, combustion byproducts, and terrorist activity. We describe an automated procedure based on isotope-dilution gas chromatography-mass spectrometry (ID GC/MS) for the accurate and rapid determination of CN in whole blood.

Methods: A known amount of isotopically labeled potassium cyanide (K¹³C¹⁵N) was added to 0.5 g of whole blood in a headspace vial. Hydrogen cyanide was generated through the addition of phosphoric acid, and after a 5-min incubation, 0.5 mL of the headspace was injected into the GC/MS at an oven temperature of -15 °C. The peak areas from the sample, ¹H¹²C¹⁴N⁺, at m/z 27 and the internal standard, ¹H¹³C¹⁵N⁺, at m/z 29, were measured, and the CN concentration quantified by ID. The analysis time was 15 min for a single injection.

Results: We demonstrated method accuracy by measuring the CN content of unfrozen whole blood samples fortified with a known amount of CN. Intermediate precision was demonstrated by periodic analyses over a 14-month span. Relative expanded uncertainties based on a 95% level of confidence with a coverage factor of 2 at CN concentrations of 0.06, 0.6, and 1.5 µg/g were 8.3%, 5.4%, and 5.3%, respectively. The mean deviation from the known value for all concentrations was <4%.

Conclusion: The automated ID GC/MS method can accurately and rapidly quantify nanogram per gram to microgram per gram concentrations of CN in blood.