Pak. J. Pharm. Sci., Vol.24, No.2, April 2011, pp.149-153 149 MODIFIED PICRATE METHOD FOR DETERMINATION OF CYANIDE IN BLOOD MUHAMMAD AVAIS 1* , MUHAMMAD SARWAR KHAN 1 , MUHAMMAD ARIF KHAN 1 , KAMRAN ASHRAF 2 , AMAR NASIR 1 , MASOOD RABBANI 3 AND ABU SAEED HASHMI 4 1 Department of Clinical Medicine and Surgery, 2 Department of Parasitology, 3 University Diagnostic Laboratory, 4 Institute of Biochemistry and Biotechnology, University of Veterinary and Animal Sciences, Lahore, Pakistan ABSTRACT Cyanide (CN) is widely distributed in the ecosystem and has been associated with toxic effects in humans and animals. Most outbreaks of CN poisoning in animals result from ingestion of plants containing cyanogenic glycosides. Various analytical techniques for estimating cyanide in blood are available. A simple picrate method was developed to determine blood CN in goats. This assay is a modification of commonly available methods using picrate paper and those using Conway diffusion cells. Cyanide in blood was measured during and after IV administration of KCN at 0.6 mg/min for 1 h. Blood CN levels in rabbits were determined after oral administration of KCN for 10, 20, 30 and 40 days. The CN concentration in blood of goats was time-dependent and continued rising during infusion followed by gradual decline after infusion stopped. A calibration curve set by dissolving various concentrations of KCN in distilled water showed a linear relationship between CN concentration and absorbance (R=0.995) ranging from 0.3-120 mg CN/L. Blood CN levels in rabbits showed time-dependent increase with maximum concentration (1.34 mg/L) at 40 days. This is a simple and inexpensive tool for the determination of blood CN in the laboratory and under field conditions as well. Keywords: KCN; goats; rabbits; picrate paper; blood. INTRODUCTION Cyanide (CN) is widely distributed in the ecosystem and has been associated with toxic effects in humans and animals. Cyanide toxicity may be the result of intake from food sources, environmental pollution, intentional ingestion, chemical warfare, occupational exposure, homicide, and sometimes through the use of drugs such as nitroprusside and laetrile (Way, 1984; Watts, 1998). Cyanogenic glycosides are naturally present in many plants, which become a source of CN following enzymatic hydrolysis. These may include cultivated forage plants of high nutritive value for man and animal e.g., Linum sp., Manihot sp., Phaseolus lunatus, and Sorghum sp. (Poulton, 1983). Different plant species contain specific glucosides i.e. Linamarin (linseed), Dhurrin (sorghum) and Amygdaline (bitter almond). Their cyanogenic components may vary widely depending upon the season and the part of the plant, with young growing leaves having the highest concentrations. The minimum lethal dose of HCN is ~2 mg/kg BW in sheep and cattle. Plants containing 200 ppm are likely to be toxic, and highly poisonous plant samples may contain up to 6000 ppm of cyanogenic glycosides (Radostits et al., 2000). Cyanide intake has been associated with syndromes of the central nervous system. Ataxia has been observed in sheep, cattle, and horses grazing sorghum, and urinary incontinence is reported in horses (McKenzie and McMicking, 1977; Bradley et al., 1995). Cases of CN poisoning of varying degrees of severity and mortality in ruminants after ingestion of cyanogenic glycosides containing plants, especially sorghum species, are reported in Pakistan. Due to the lack of simple and economic diagnostic techniques under field conditions, field veterinarians depend upon the history of feeding and clinical signs to diagnose CN poisoning (pers. com. Nasir A). Analytical techniques available for determination of CN in plants and biological fluids include amperometery (Park et al., 1997), voltammetery (Tatsuta et al., 2001) polarography (do Nascimento et al., 1998), potentiometery (Sequeira et al., 1999), piezoelectricity (Gomes et al., 1998), gas chromatography (Cardeal et al., 1995), visible spectrophotometry (Laforge et al., 1994), mass spectrometry (Tracqui et al., 2002), HPLC (Akiyama et al., 2006) and flow injection (Recalde-Ruiz et al., 2000). The variety of analytical methods reported for CN in blood may indicate the difficulty of its analysis in that there is no universally preferred method (Hughes et al., 2003). Available methods are expensive, laborious, and require technical expertise and sophisticated equipment. *Corresponding author: e-mail: avaismuhammad@yahoo.com