Free Hydrogen Cyanide Research Articles

Total and Free Hydrogen Cyanide Content and Profile of Bioactive Amines in Commercial Tucupi, a Traditionally Derived Cassava Product Widely Consumed in Northern Brazil.

Tucupi is a broth derived from cassava roots which is produced after the spontaneous fermentation of manipueira (the liquid portion obtained by pressing cassava roots), followed by cooking. This product is widely consumed along with traditional dishes in the Brazilian Amazonia and is already used in different places worldwide. In this study, tucupi obtained from the markets of Belém (Pará, Brazil) and produced using agroindustrial (11 samples) and non-agroindustrial (11 samples) units were investigated to determine their physicochemical characteristics, total and free HCN contents, and free bioactive amine profiles. Most of the samples showed significant variations (p ≤ 0.05) in pH (2.82-4.67), total acidity (0.14-1.36 g lactic acid/100 mL), reducing sugars (up to 2.33 g/100 mL), and total sugars (up to 4.35 g/100 mL). Regarding the amines, four biogenic amines (0.5-4.2 mg/L tyramine, 1.0-23.1 mg/L putrescine, 0.5-66.8 mg/L histamine, and 0.6-2.9 mg/L tryptamine) and one polyamine (0.4-1.7 mg/L spermidine) were identified in the tucupi samples. Even in the tucupi produced using the agroindustrial units, which had quality seals provided by the local regulatory agency, high levels of biogenic amines (4.4-78.2 mg/L) were observed, as well as high dosages of total (8.87-114.66 mg/L) and free (0.80-38.38 mg/L) HCN. These facts highlight the need for better knowledge regarding the product manufacturing process to establish standardization and high-quality conditions for tucupi processing since high contents of biogenic amines and HCN are commonly associated with adverse health effects.

Potential of Soaking and Sun-Drying in Detoxifying Toxic Cassava Root Tubers

Root tubers of cassava (Manihot esculenta Crantz) have cyanogenic glucosides which liberate hydrogen cyanide (HCN) on hydrolysis in quantities that can be toxic to humans. As a result, several techniques have been used to detoxify the tubers including among others, soaking, sun-drying and fermentation which has been found to be the most effective. However, fermentation is associated with the growth of potentially mycotoxigenic moulds (fungi) which compromise the quality of the processed product hence suggesting the use of alternative mould free processing techniques like soaking and sun-drying. Therefore, this study investigated the potential of soaking and sun-drying in detoxifying root tubers of a toxic cassava variety, “Rutuga”, (interpreted as “strangler”) of cyanogens (total HCN, free HCN and bound HCN) in South Western Uganda. The cyanogens were determined by a standard titration method. The results indicated that soaking peeled cassava root tubers in cold distilled water for 4 days removed about 78% of bound HCN while sun-drying of peeled cassava chips for 5 days removed about 74% of free HCN. However, both methods are less effective in removing total HCN (soaking, 47%; sun-drying, 43%) due to the ineffectiveness of soaking and sun-drying in removing free HCN (21%) and bound HCN (3%) respectively. Hence a mixed approach employing both methods would be more appropriate in detoxifying cassava of total HCN.

Hydrogen Cyanide Accumulation and Transformations in Non-polluted Salt Marsh Sediments

While cyanide is known to be produced by many organisms, including plants, bacteria, algae, fungi and some animals, it is generally thought that high levels of cyanide in aquatic systems require anthropogenic sources. Here, we report accumulation of relatively high levels of cyanide in non-polluted salt marsh sediments (up to 230 μmol kg−1). Concentrations of free cyanide up to 1.92 μmol L−1, which are toxic to aquatic life, were detected in the pore-waters. Concentration of total (free and complexed) cyanide in the pore-waters was up to 6.94 μmol L−1. Free cyanide, which is released to the marsh sediments, is attributed to processes associated with decomposition of cord grass, Spartina alterniflora, roots and possibly from other sources. This cyanide is rapidly complexed with iron and adsorbed on sedimentary organic matter. The ultimate cyanide sink is, however, associated with formation of thiocyanate by reaction with products of sulfide oxidation by Fe(III) minerals, especially polysulfides. The formation of thiocyanate by this pathway detoxifies two poisonous compounds, polysulfides and hydrogen cyanide, preventing release of free hydrogen cyanide from salt marsh sediments into overlying water or air.

The Concentration of Ethyl Carbamate in CommercialUme(Prunus mume) Liqueur Products and a Method of Reducing It

The ethyl carbamate concentration of commercial ume liqueur products was studied, and a method of reducing it was examined from the viewpoint of antioxidation. The average ethyl carbamate concentration across 38 ume liqueur products was 0.12 mg/l (0.02-0.33 mg/l). When potassium metabisulfite was added to a concentration of 0-1,000 ppm during production, the generation of ethyl carbamate was reduced in a concentration-dependent manner, but when the amount of potassium metabisulfite added was below the maximum level allowed under the Japanese Food Sanitation Act, the reduction was only 27%. When ume liqueurs were produced under deoxygenated conditions created using an oxygen absorber, the ethyl carbamate concentration was reduced by up to 47% as compared with the control group, probably due mainly to a reduction in free hydrogen cyanide. When ume liqueur was produced in an oxygen atmosphere, the ethyl carbamate concentration increased by up to 50% as compared with the control group. Thus, oxygen may be involved in the generation of ethyl carbamate in ume liqueur production.

<b>STUDIES ON SOLVENT EXTRACTION OF FREE HYDROGEN CYANIDE FROM RIVER WATER</b>

A method for free and strongly complexed cyanide measurement in river water was developed. Recovery tests from solution with and without river water, using various solvent combinations and background control were investigated to obtain an accurate and precise extraction method for the measurement of hydrogen cyanide in Kaduna River, Nigeria. The method enhanced the determination of undissociated hydrogen cyanide and the equilibria between hydrogen cyanide, cyanide ion and complex cyanides. A small portion of the hydrogen cyanide was extracted by equilibrating the sample with methylchloroform (1,1,1-trichloroethane), methanol, hexane and 2-octanol inclusions, respectively, in the solvent matrix with 2.5 M NaOH. The extracted hydrogen cyanide is transferred into tetrasodium pyrophosphate solution and determined colorimetrically. A total cyanide concentration of 0.03 mg/L in the river water and 0.40 mg/L in an effluent water sample, respectively, were obtained by the proposed method compared to 0.020 and 0.45 mg/L from the established diffusion method. The proposed method was sensitive and reproducible in the range of 0 to 5 mgL -1 of hydrogen cyanide with detectable limit of about 0.01 mgL -1 . KEY WORDS : Solvent extraction; Free hydrogen cyanide; River water Bull. Chem. Soc. Ethiop. 2007 , 21(3), 305-313.

Asymmetric synthesis of cyanohydrin derived from pyridine aldehyde with cross-linked aggregates of hydroxynitrile lyases

Enantiocomplementary R- and S-cyanohydrins with >93% ee were synthesized through the hydrocyanation of 3-pyridinecarboxaldehyde in >65% yield. Hydroxynitrile lyases (HNLs) from cassava and almond were used in commercially available cross-linked enzyme aggregate (CLEA) forms to catalyze the reactions and produce material with optical purities significantly greater than has been reported previously. The use of a dichloromethane reaction system with enzyme aggregates and free hydrogen cyanide was crucial in improving cyanohydrin stereoselectivity through minimizing background racemic cyanide addition and enzyme-catalyzed racemization of the product.

Long-term trends of tropospheric carbon monoxide and hydrogen cyanide from analysis of high resolution infrared solar spectra

Long-term trend and seasonal variation of the mean free tropospheric volume mixing ratios of carbon monoxide (CO) and hydrogen cyanide (HCN) have been derived from analysis of a time series of solar absorption spectra recorded from the US National Solar Observatory on Kitt Peak (31.9°N, 111.6°W, 2.09 km altitude) spanning almost three decades. The results of a fit to the CO 258 daily averages from May 1977 to April 2005 as a function of time with a model that assumes a sinusoidal seasonal cycle and a linear long-term trend with time yield a mean volume mixing ratio of 102 ± 3 ) parts per billion ( 10 - 9 per unit volume) below 10 km altitude, 1 sigma. The CO measurements show a seasonal cycle with a maximum in March and a minimum in September with an amplitude of ( 22.3 ± 1.5 ) % relative to the mean. The best-fit corresponds to a long-term CO trend of ( 0.15 ± 0.14 ) % yr - 1 , 1 sigma, relative to the mean. To quantify the possible impact of periods of intense fires, the CO measurements have been compared with the measurements of HCN, a well-documented emission product of biomass burning with a lifetime of ∼ 5 months. The best fit to the full HCN time series of 208 daily averages from May 1978 to April 2005 results in a mean volume mixing ratio of ( 0.219 ± 0.007 ) ppbv below 10 km altitude with a similar seasonal cycle, though with a lower relative amplitude than for CO. Although same-day enhancements up to a factor of 1.87 for HCN and 1.24 for CO were measured relative to values predicted by a fit to the time series that accounts for the seasonal cycles and trends of both molecules, excluding time periods of elevated fire emissions has no significant impact on the best-fit long-term free tropospheric CO and HCN trends. Our result of no long-term CO trend since the late 1970s suggests that the global average long-term decline reported from 1990 through 1995 measurements has not continued in the free troposphere. Similarly, a fit to the full time series of 208 HCN free tropospheric daily averages with the same model yields an average 2.09–10 km mixing ratio of 0.219 ppbv and a long-term trend of ( - 0.12 ± 0.14 ) % yr - 1 , 1 sigma, relative to the mean since 1978, also indicating no significant long-term trend above the lower mid-latitude continental US Kitt Peak station. The results for both molecules suggest the site was not significantly impacted by summer boreal fires during the time span of the measurements that in some years cause widespread pollution above northern higher latitude sites.

Possible reaction mechanisms of hydrogen cyanide formation from oxime blocked isocyanates and related organic compounds during total cyanide analysis

Frequent reports by paint manufactures of hydrogen cyanide detection in waste contaminated with oxime blocked isocyanates lead to an investigation of possible hydrogen cyanide generating reaction pathways. GC‐MS is empolyed to analyze traces of byproducts of the total cyanide analysis. A Beckmann Rearrangement of oxime blocked isocyanates has been detected. The formation of α‐ketocyanides and their hydrolysis to free hydrogen cyanide is reported as the key compound that leads to hydrogen cyanide generation. Hydrogen cyanide yields from the reaction of NOx or hydroxylamine with ketones, alcohols, amines, peptides, EDTA, ascorbic acid and cyanides. The presence of an organic phase improves hydrogen cyanide yields. A sample pretreatment for oxime blocked isocyanate samples is described.

Utilization of Amygdalin during Seedling Development of Prunus serotina.

Cotyledons of mature black cherry (Prunus serotina Ehrh.) seeds contain the cyanogenic diglucoside (R)-amygdalin. The levels of amygdalin, its corresponding monoglucoside (R)-prunasin, and the enzymes that metabolize these cyanoglycosides were measured during the course of seedling development. During the first 3 weeks following imbibition, cotyledonary amygdalin levels declined by more than 80%, but free hydrogen cyanide was not released to the atmosphere. Concomitantly, prunasin, which was not present in mature, ungerminated seeds, accumulated in the seedling epicotyls, hypocotyls, and cotyledons to levels approaching 4 [mu]mol per seedling. Whether this prunasin resulted from amygdalin hydrolysis remains unclear, however, because these organs also possess UDPG:mandelonitrile glucosyltransferase, which catalyzes de novo prunasin biosynthesis. The reduction in amygdalin levels was paralleled by declines in the levels of amygdalin hydrolase (AH), prunasin hydrolase (PH), mandelonitrile lyase (MDL), and [beta]-cyanoalanine synthase. At all stages of seedling development, AH and PH were localized by immunocytochemistry within the vascular tissues. In contrast, MDL occurred mostly in the cotyledonary parenchyma cells but was also present in the vascular tissues. Soon after imbibition, AH, PH, and MDL were found within protein bodies but were later detected in vacuoles derived from these organelles.

Determination of free hydrogen cyanide in river water by a solvent-extraction method.

The method described for the determination of undissociated hydrogen cyanide in river waters is designed to avoid disturbance of the equilibria between hydrogen cyanide, cyanide ion and complex cyanides during the determination. A small proportion of the hydrogen cyanide present is extracted by equilibrating the sample with 1,1,1-trichloroethane. The extracted hydrogen cyanide is then transferred into sodium pyrophosphate solution, and the determination is completed colorimetrically by a modification of the method of Bark and Higson. The effect of temperature on the extraction has been studied. Extractions can be carried out in the field, and conditions have been established for bringing extracted samples back to the laboratory for colorimetric analysis. The method can be used in the range 0 to 2 mg of hydrogen cyanide l–1 and less than 0·01 mg l–1 is detectable. Satisfactory tests have been carried out on solutions of known hydrogen cyanide content, on solutions of metallic complex cyanides and on river waters containing added cyanide.

ON THE SOURCE OF HYDROGEN CYANIDE IN CULTURES OF A SNOW MOLD FUNGUS

An unidentified basidiomycete, which produces hydrogen cyanide in culture, was shown to accumulate a cyanogenic compound in growing mycelium before free hydrogen cyanide could be detected. At all phases of growth the hydrogen cyanide present in the free state was a relatively small fraction of that in the combined form. Crude preparations of the cyanogenic compound were obtained by methanol extraction of dried mycelium. It is soluble in water and methanol and moderately soluble in ethanol. In solution it is heat labile and, in contrast to cyanogenic glycosides isolated from higher plants, decomposes rapidly at pH values above 6.0. No evidence of enzymic breakdown either in vivo or in vitro was obtained.