Analytical techniques for cyanide in blood and published blood cyanide concentrations from healthy subjects and fire victims

Cobinamide-based cyanide analysis by multiwavelength spectrometry in a liquid core waveguide

A novel cyanide analyzer based on sensitive cobinamide chemistry relies on simultaneous reagent and sample injection and detection in a 50 cm liquid core waveguide (LCW) flow cell illuminated by a white light emitting diode. The transmitted light is read by a fiber-optic charge coupled device (CCD) spectrometer. Alkaline cobinamide (orange, lambda(max) = 510 nm) changes to violet (lambda(max) = 583 nm) upon reaction with cyanide. Multiwavelength detection permits built-in correction for artifact responses intrinsic to a single-line flow injection system and corrects for drift. With optimum choice of the reaction medium, flow rate, and mixing coil length, the limit of detection (LOD, S/N = 3) is 30 nM and the linear dynamic range extends to 10 microM. The response base width for 1% carryover is <95 s, permitting a throughput of 38 samples/h. The relative standard deviations (rsd) for repetitive determinations at 0.15, 0.5, and 1 microM were 7.6% (n = 5), 3.2% (n = 7), and 1.7% (n = 6), respectively. Common ions at 250-80,000x concentrations do not interfere except for sulfide. For the determination of 2 microM CN(-), the presence of 2, 5, 10, 20, 100, and 1000 microM HS(-) results in 22, 27, 48, 58, 88, and 154% overestimation of cyanide. The sulfide product actually has a different characteristic absorption, and in those samples where significant presence is likely, this can be corrected for. We demonstrate applicability by analyzing the hydrolytic cyanide extract of apple and pear seeds with orange seeds as control and also measure HCN in breath air samples. Spike recoveries in these sample extracts ranged from 91 to 108%.

Turn-on fluorescent cyanide sensor based on copper ion-modified CdTe quantum dots

A new fluorescent sensor for the sensitive and selective detection of cyanide (CN(-)) in aqueous media was developed herein. The sensing approach is based on CN(-)-modulated quenching behavior of Cu(2+) toward the photoluminescence (PL) of CdTe quantum dots (QDs). In the presence of CN(-), the PL of QDs that have been quenched by Cu(2+) was found to be efficiently recovered, which then allows the detection of CN(-) in a very simple approach. Experimental results showed that the pH of the buffer solution, concentration of copper ions, and size of CdTe QDs all influenced the response of the sensor to CN(-). Under the optimal conditions, a good linear relationship between the PL intensity and the concentration of CN(-) can be obtained in the range of 3.0 x 10(-7) to 1.2 x 10(-5) M, with a detection limit as low as 1.5 x 10(-7) M. In addition, the present fluorescent sensor possesses remarkable selectivity for cyanide over other anions, and negligible influences were observed on the cyanide detection by the coexistence of other anions or biological species (such as albumin and typical blood constituents). Therefore, we expect the proposed copper ion-modified QDs to be an efficient and reliable sensing system to monitor cyanide concentration in environmental or clinical applications.

Headspace single-drop microextraction with in-drop derivatization and capillary electrophoretic determination for free cyanide analysis

A new method involving headspace single-drop microextraction (SDME) with in-drop derivatization and CE is developed for the preconcentration and determination of free cyanide. An aqueous microdrop (5 microL) containing Ni(II)-NH(3) (as derivatization agent), sodium carbonate and ammonium pyromellitate (as internal standard) was used as the acceptor phase. The extracted cyanide forms a stable Ni(CN)(4) (2-) complex which is then determined by CE. Common experimental parameters (sample and acceptor phase pH, extraction temperature, extraction time and sample ionic strength) affecting the extraction efficiency were investigated. Using headspace SDME, free cyanide can be effectively extracted from the neutral solutions, i.e. without the acidification of the sample which often is prone to errors due to incomplete liberation and artefactual cyanide production. Proposed SDME-CE method provided about 58-fold enrichment in 20 min. The calibration curve was linear for concentrations of CN(-) in the range from 0.25 to 20 micromol/L (R(2) = 0.997). The LOD (S/N = 3) was estimated to be 0.08 micromol/L of CN(-). Such a detection sensitivity is high enough for free cyanide determination in common environmental and physiological samples. Finally, headspace SDME was applied to determine free cyanide in human saliva and urine samples with spiked recoveries in the range of 91.7-105.6%. The main advantage of this method is that sample clean-up, preconcentration and derivatization procedures can be completed in a single step. In addition, the proposed technique does not require any sample pretreatment and thus is much less susceptible to interferences compared to existing methods.

Determination of cyanide in blood by isotope-dilution gas chromatography-mass spectrometry

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 degrees 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 was 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 microg/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.

An improved method for cyanide determination in blood using solid-phase microextraction and gas chromatography/mass spectrometry

A new method is described for the qualitative and quantitative analysis of cyanide, a very short-acting and powerful toxic agent, in human whole blood. It involves the conversion of cyanide into hydrogen cyanide and its subsequent headspace solid-phase microextraction (HS-SPME) and detection by gas chromatography/mass spectrometry (GC/MS) in selected ion monitoring (SIM) mode. Optimizing the conditions for the GC/MS (type of column, injection conditions, temperature program) and SPME (choice of SPME fiber, effect of salts, adsorption and desorption times, adsorption temperature) led to the choice of a 75-microm carboxen/polydimethylsiloxane SPME fiber, with D3-acetonitrile as internal standard, and a capillary GC column with a polar stationary phase. Method validation was carried out in terms of linearity, precision and accuracy in both aqueous solutions and blood. The limit of detection (LOD) and limit of quantitation (LOQ) were determined only in aqueous solutions. The assay is linear over three orders of magnitude (water 0.01-10, blood 0.05-10 microg/mL); and the LOD and LOQ in water were 0.006 and 0.01 microg/mL, respectively. Good intra- and inter-assay precision was obtained, always <8%. The method is simple, fast and sensitive enough for the rapid diagnosis of cyanide intoxication in clinical and forensic toxicology.