Low Cyanide Research Articles

Dynamic rheological and physicochemical properties of annealed starches from two cultivars of cassava

Starch from tubers of “sweet” (low cyanide) and “bitter” (high cyanide) cassava ( Manihot esculentum Crantz) crops was isolated and subjected to annealing treatment at 50 °C for 24,96,144 and 192 h in 1:5 starch to water ratio. Annealing generally reduced the swelling power and solubility of the starches. Storage modulus ( G′) and loss modulus ( G″) increased with decrease in complex viscosity (Eta*) as a function of angular frequency ( ω). The magnitudes of G′ reported were greater than those of G″ revealing frequency dependency except sweet starch cultivar annealed at 192 h. The tan δ (ratio of G″/ G′) of annealed starches were within the ranges of 0.31–0.39 and 0.23–0.45 for sweet and bitter cultivars, respectively. The tan δ values of the starches were lower than one, indicating that the samples are elastic in nature than viscous. The X-ray patterns of the A-type starches were not altered on annealing denoting that the double helices in the amorphous region were not disrupted. Annealing as revealed by scanning electron micrographs changed the structure of the sweet cultivar, while there was no change in the size and shape of the bitter cultivar.

Co-intensification of cyanide leaching gold by mercury ions and oxidant

The effects of mercury ions on gold cyanidation were studied. The results show that under low cyanide concentration, gold cyanide process is controlled by CN − transfer, while at higher cyanide concentration, there forms passivation on gold surface. Therefore, chemical oxidation of gold in cyanide solution of higher concentration is controlled by surface reaction. Small quantity of additions of mercury ions bring about great increases in anodic gold dissolution rate, decreases the passivation and reduces the equilibrium activated energy. In addition, they also markedly change the effect pattern of cyanide concentration. Mercury ions show positive effects on cathodic reduction of oxygen and raise the rate of electrochemical step of the cathodic reduction of oxygen. Addition of a certain amount of hydrogen peroxide is confirmed to be an effective way for intensification of cathodic process on gold electrode. Active potential range and current peak on anodic dissolution are enlarged when being co-intensified with Hg 2+ and hydrogen peroxide. Co-intensifying effect may be obtained and gold leaching rate is considerably increased on cyanide leaching of gold from gold concentrates.

Simple method to reduce the cyanogen content of gari made from cassava

The lactic acid content of gari, was determined by pH titration to be about 10 g lactic acid/kg gari. As the size of the gari particles increased from 400 to >1000 μm their total cyanide content increased from 5 to 21 ppm. The acetone cyanohydrin content of gari samples exposed to ambient laboratory conditions of temperature and relative humidity gradually decreased by 58% in 38 weeks whereas linamarin in cassava flour is 100% stable for 6 months. Cyanogens could not be removed from wet gari samples at 30 or 50 °C and were only slowly removed by repeated heating at 100 °C and rewetting. By mixing equal weights of gari (pH 4.1) and low cyanide cassava flour (pH 6.5), wetting and heating at 50 °C for 5 h, the cyanide content was reduced by about one half. Wetting a gari/flour (1:1) sample with 1.5 times its weight of water and standing in a 1 cm thick layer in the sun for 4 h reduced the cyanide content by about one half. This treated mixture may be cooked to prepare stiff porridge with lowered cyanide content, and may help reduce tropical ataxic neuropathy in West Africa.

Utilization of Cassava Through Freezing

Investigations were carried out to use cassava in frozen form to increase the consumption among people. Two popular varieties MU 51 and Kirikavadi were used for the study. Heat treatments of blanching and boiling together with packing materials of Low-density polyethylene (LDPE) and Low-density polyethylene and Nylon (LDPE+N) were tested in completely randomized design. Both varieties had a minimum percentage weight loss during storage. Microbiological study showed that all samples were safe for consumption up to 3 months at freezer storage. Cyanide levels were significantly reduced by boiling before freezing. Variety Kirikavadi had significantly lower cyanide levels than variety MU 51. Quick freezing using a modification in a normal freezer showed superior quality of frozen product compared to those of stored in a normal freezer. Both varieties of cassava after boiling for 15 minutes for softening, can quick freeze and then transfer to a normal freezer to maintain the frozen condition. This method can therefore commercially be recommended to utilize cassava for up to 3 months of storage life. Keywords: Cassava; freezing; quality; storage life DOI: 10.4038/jfa.v1i2.1796 Journal of Food and Agriculture Vol.1(2) 2008 pp.17-29

Influence of size reduction variation and fermentation time towards cyanide acid contents and phenolic compound in faba bean (Vicia faba) tempeh

Indriyani CS, Handayani S, Rachmawati D. 2010. Influence of size reduction variation and fermentation time towards cyanide acid contents and phenolic compound in faba bean (Vicia faba) tempeh. Biofarmasi 8: 31-36. Tempeh is fermentation product wich very known by Indonesian society and has been familiar with various western society. Tempeh can be made from various ingredient, but usually, tempeh is made from soybean. Due to the increasing soybean price, it has been found another Leguminosae to substitute soybean. One of legume was faba bean, Leguminosae, that generally contains phenol as antioxidant and cyanide acid as antinutrient and toxic material. The aim of this research was to determine the effect of size reduction variation and fermentation time variation of faba beans tempeh production to cyanide acid and total phenol contents. This research used a factorial experiment that arranged in a Randomized Complete Design (RCD) with two experimental factors including size reduction (chopped and sliced) and the time of fermentation (0, 30, 36, 42 and 48 hours). The result showed that cyanide acid content in fermentation of 0, 30, 36, 42 and 48 hours on faba beans tempeh by chopped seeds were 0.060 mg/g, 0.048 mg/g, 0.036 mg/g, 0 mg/g and 0 mg/g, respectively, then on faba beans tempeh by sliced seeds were 0.072 mg/g, 0.036 mg/g, 0.036 mg/g, 0 mg/g and 0 mg/g, respectively. Meanwhile, the content of total phenol on faba beans tempeh by chopped seeds were 0.014750%, 0.149900%, 0.201825%, 0.170400% and 0.234400%, while on faba beans tempeh by sliced seeds were 0.014750%, 0.152650%, 0.178300%, 0.162750% and 0.192620%, respectively. The fermentation time and the size of faba beans seeds affected on cyanide acid and total phenol contents of faba beans tempeh. The longer fermentation time of faba beans tempeh caused lower cyanide acid content and higher total phenol content. The smaller size of faba beans seeds on tempeh caused lower cyanide acid content and higher total phenol content. The lowest cyanide acid content was contained in faba beans tempeh with chopped and sliced seeds with 42 and 48 hours fermentation reached 0 mg/g. The highest total phenol content was contained in chopped faba beans tempeh with 48 hours fermentation reached 0.234400%.

Control of Respiration by Cytochrome c Oxidase in Intact Cells

Metabolic control analysis was applied to intact HepG2 cells. The effect on the control coefficient of cytochrome c oxidase (CcOX) over cell respiration of both the electrical (Delta psi) and chemical (Delta pH) component of the mitochondrial transmembrane proton electrochemical gradient (Delta mu(H(+))) was investigated. The overall O(2) consumption and specific CcOX activity of actively phosphorylating cells were titrated with cyanide under conditions in which Delta psi and Delta pH were selectively modulated by addition of ionophores. In the absence of ionophores, CcOX displayed a high control coefficient (C(IV) = 0.73), thus representing an important site of regulation of mitochondrial oxidative phosphorylation. A high control coefficient value (C(IV) = 0.85) was also measured in the presence of nigericin, i.e. when Delta psi is maximal, and in the presence of nigericin and valinomycin (C(IV) = 0.77), when Delta mu(H(+)) is abolished. In contrast, CcOX displayed a markedly lower control coefficient (C(IV) = 0.30) upon addition of valinomycin, when Delta psi is converted into Delta pH. These results show that Delta psi is responsible for the tight control of CcOX over respiration in actively phosphorylating cells.

Evaluation of leaching parameters for a refractory gold ore containing aurostibite and antimony minerals: Part I – Central zone

A cyanidation study was conducted on a mild refractory gold ore sample from the Central zone of Clarence Stream Property, owned by Freewest Resources Canada, to develop a leaching strategy to extract gold. Gold, at a grade of 8.00 g/t, is present as native gold, electrum and aurostibite. The ore also contains 2.8% pyrrhotite, together with several antimony minerals (0.8% berthierite and gudmundite, 0.18% native antimony and stibnite). It also exhibits weak preg-robbing properties with 0.16% organic carbon. Aurostibite, a gold antimony compound, is particularly known to be insoluble in cyanide solution. The antimony dissolves in cyanide solution to form antimonates, which retards gold dissolution. Industrial practice of extracting gold from aurostibite generally consists of producing a flotation concentrate, which is leached in a pipe reactor at low alkalinity and high oxygen pressure with about 20 g/L cyanide. The proposed new approach is efficient and allows the extraction of gold directly from an ore at atmospheric pressure and a low cyanide concentration at pH 10.5. The effects of grinding, pre-treatment, lead nitrate, kerosene and cyanide concentrations have been investigated. The maximum gold extraction obtained on the ore was 87.9% using 800 ppm NaCN, 500 g/t lead nitrate, 30 g/t kerosene, DO (dissolved oxygen) 10 ppm and pH 10.5 in 168 h. The associated cyanide consumption was 1.3 kg/t. The additions of lead nitrate and kerosene increased gold extraction. In comparison to a P 80 of 74 μm, a P 80 of 30 μm significantly increased gold extraction. Gold in solid solution in gudmundite and arsenopyrite was believed to be responsible for the un-leached fraction until mineralogical analysis of hydroseparation concentrates of leach residues showed that most of the un-leached gold occurs as aurostibite, either as locked grains in sulphides/sulpharsenides or as grains with passivation rims of an Au–Sb–O phase. Coarse gold was also found. Gold extraction was not sensitive to cyanide concentration from 250 to 1200 ppm NaCN and high pH was detrimental. Decreasing the cyanide concentration reduced the cyanide consumption from 1.39 to 0.85 kg/t. The removal of coarse gold using a Knelson concentrator and a Mosley table prior to leaching increased the gold extraction to 90.4% (leach residue at 0.77 g/t).

Nutritive Value and Antioxidant Properties of Cereal Gruels Produced from Fermented Maize and Sorghum

Cereal gruels prepared from fermented maize (yellow and white) and sorghum seeds are the forms in which cereal are popularly consumed in tropical Africa, mostly as weaning food for children. The present study sought to determine the nutritional and antioxidant properties of cereal gruels produced from maize (yellow and white) and sorghum seeds. Seeds of maize (yellow and white) and sorghum were fermented (in water) for 3 d before milling and sieving. The filtrate obtained was allowed to sediment and pressed in a sack to obtain the cereal gruels. The nutrients (proximate and mineral composition), anti-nutrients (phytate, cyanide, and tannin), and antioxidant activity (total phenolic content, reducing power, free radical scavenging ability and Fe2 + chelating ability) of the gruels were subsequently determined. The results of the study revealed that there was no significant difference (P > 0.05) in the protein (7.0–7.6%), crude fiber (0.1%), ash (0.5–0.8%), carbohydrate (90.2–90.4%), and anti-nutrient [cyanide (0.3mg/kg), phytate (280.5–282.3mg/100g), tannin (0.2–0.3%)] contents of the gruels produced from maize (yellow and white) and sorghum. However, fat and Zn content of yellow-maize gruel was significantly (P < 0.05) higher than others, while sorghum had a significantly (P < 0.05) higher Fe, Mg, Ca, and Na content than the other gruels. White-maize gruel had a significantly higher K than others. The calculated [Ca][phytate]/[Zn molar ratio of the cereal gruels were above 0.5mol./Kg, an indication of reduced Zn content. The results of the antioxidant properties revealed that there was no significant difference (P > 0.05) in the total water extractable phenolics in the cereal gruels. However, white-maize gruel had a significantly higher (P < 0.05) free radical scavenging ability, reducing power and Fe (II) chelating ability than yellow-maize and sorghum gruels, while sorghum gruel had the least antioxidant activity (except in Fe (II) chelation ability). It is obvious from the study that the maize (white and yellow) and sorghum gruel had low nutrient (proximate and mineral), cyanide and tannin content; the phytate present in the gruels reduced the estimated bioavailability of Zn to a critical level. Nevertheless, the cereal gruels had relatively high antioxidant activity, with white-maize gruel having the highest antioxidant potentials.

Analysis of Cyanide in Blood by Headspace-Isotope-Dilution-GC-MS

An uncomplicated, rapid, automated procedure for the analysis of low cyanide concentrations in whole blood is reported. The analysis was performed by headspace gas chromatography and mass spectrometry in the (1H12C14N) and m/z 29 (1H13C15N). Carryover from cyanide adsorption onto the surface of the needle was prevented by developing a new method that enabled automated flushing of the needle in between each cyanide analysis. Results were compared of ordinary calibrations and those of isotope dilutions. The total time of analysis was 18 min for a single cyanide analysis.

Evaluation of Moisture, Total Cyanide and Fiber Contents of Garri Produced from Cassava (Manihot utilissima) Varieties Obtained from Awassa in Southern Ethiopia

3 Abstract: Cassava (Manihot esculent crantz) as one of the most important root crops in Sub-Saharan Africa plays a vital role in the diet of many African countries especially the grass root people, being the major source of daily carbohydrate intake. Traditionally processed staple foods from cassava are available in Western and some Eastern African countries, such as garri , foofoo, boiled cassava meal, etc. Several varieties of M. Utilissima obtained from Awassa, Ethiopia, were processed, fermented and converted into garri. The moisture, total cyanide and fibre contents of the processed garri were analyzed. The results showed that the moisture, total cyanide and fiber contents varied from 26.12-40.02 %, 1.51-2.81 mg HCN/100 g and 1.80- 2.40% respectively. The largest reduction in cyanide content (41%) between the third and fourth day fermentation was found in the MM 96/5280 variety which had an increase of 32% fiber content when compared with other varieties. These results compared favorably with similar garri products obtained from Ghana and Nigeria. The ease of preparation and potential nutritional value resulting from fermentation, the low moisture, cyanide and improved fiber contents found, indicate the suitability of the garri products as nutritional food items. The Kello44/72 and MM96/5280 varieties with the lowest cyanide and comparable fiber contents are most suitable. In order to enrich the nutritional contents of the garri product, fortification with leguminous plants or fish is recommended so as to make it more suitable as an alternative food product to injera in Ethiopia.

Electrolytic recovery of silver from low concentrated silver cyanide spent plating solutions

Cyanide silver solution containing 200 to 1000 mg L−1 silver ions were used for recovery studies. The nature of the silver deposit was studied using a Hull cell, and the current density range was selected for electrolysis to recover silver. A batch electrochemical reactor, consisting of a planar stainless steel cathode and platinum anode was used and silver was recovered at 0˙04 to 0˙2 A dm−2. The effect of different initial silver concentrations on the electrochemical recovery of the metal was investigated as a function of electrolysis duration at various current densities. The cathode current efficiency and the energy consumption were determined for the solutions for various experimental conditions. Surface morphology and structure of the silver deposit was also studied using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results show that irrespective of the initial silver concentration, higher current efficiency and lower energy consumption can be achieved at a low current density. For a given current density, the energy consumption to recover silver is lower from relatively concentrated than from dilute solutions.

EPR and kinetic investigation of free cyanide oxidation by photocatalysis and ozonation

Oxidation of free cyanide in aqueous suspensions of three commercial TiO2 specimens, with different anatase crystal size, has been carried out in a batch photoreactor by simultaneously applying ozonation and photocatalysis. Dissolved ozone participates both in homogeneous and catalytic reactions with cyanide; the extents of these two processes are comparable to that of the photodegradation with oxygen. The reactivity results are well described by the Langmuir-Hinshelwood kinetic model, providing the values of the kinetic and equilibrium adsorption constants for the catalytic and photocatalytic reactions contributing to cyanide oxidation. The cyanide concentration decreases faster with time for catalysts with increasing anatase crystal size, being more marked under UV irradiation. EPR studies on gaseous ozone adsorption on the three samples in the dark have shown stronger ozone interactions with Ti4+ and O2− ions of the samples with largest anatase crystal size, leading to the formation of significant signals of Ti3+ and s O−−O2 radicals than with the anatase with the lowest crystal size, where ozone was mainly adsorbed on water molecular arrangements covering its surface. The hampering of the ozone and/or cyanide adsorption by the water molecular arrangements covering the surface of the catalyst with the lowest crystal size would justify the low cyanide degradation rate observed for this sample.

Effects of sub-chronic oral cyanide on endothelial function in rabbit aortic rings

We have investigated how the endothelium affects vascular responses following sub-chronic low dose cyanide administration. Cyanide exists in low levels in cassava foods, which are widely consumed in tropical Africa. Adult rabbits were administered 0.38 mg/kg per day KCN po for 25 days, and responses of the isolated aortic rings to noradrenaline (NA), calcium chloride (Ca2+) and acetylcholine (ACh) were measured in vitro in the presence and absence of the endothelium. In order to establish that the dose was not toxic, animal weight, some haematological indices, plasma alanine aminotransferase (ALT), and aspartate aminotransferase (AST) were measured. Results show that endothelium denudation significantly (P <0.05) attenuates NA-induced contraction in rings from cyanide-treated rabbits. There was a similar reduction in response in Ca2+-depleted NA-precontracted endothelium-denuded aortic rings from cyanide-treated rabbits. Endothelium-denuded rings from cyanide-treated rabbits showed significantly (P <0.05) enhanced relaxation to ACh. In rings from control animals, the responses to NA and Ca2+ were not significantly altered, whether in the presence or absence of the endothelium. There were no significant changes in the studied toxicological indices. We conclude that endothelial compromise is necessary for low-dose sub-chronic cyanide-induced to alter vascular reactivity to NA and ACh.

De novo Synthesis vs. Sequestration: Negatively Correlated Metabolic Traits and the Evolution of Host Plant Specialization in Cyanogenic Butterflies

Larvae of Heliconius butterflies (Nymphalidae: Heliconiinae) feed exclusively on cyanogenic leaves of Passiflora (passion vine). Most Heliconius manufacture cyanogenic glycosides (cyanogens) and some species sequester cyanogens from host plants. We compare ability to sequester simple monoglycoside cyclopentenyl (SMC) cyanogens and manufacture aliphatic cyanogens in 12 Heliconius species, including larvae that are specialized (single host species) and generalized (many host species). All butterflies tested higher for cyanide concentrations when reared on plants that larvae can sequester from (SMC plants) than when reared on plants that larvae do not sequester from (non-SMC plants). Specialists in the sara-sapho clade sequestered SMC cyanogens from specific host plants at seven times that of Passiflora generalists fed the same hosts. In contrast, sara-sapho clade species reared on non-SMC plants had significantly lower cyanide concentrations from de novo synthesis than generalists fed the same plants. Furthermore, cyanogen analyses indicated that Heliconius sara butterflies reared on an SMC host had a greater proportion of sequestered SMC cyanogens (95.0%) than de novo-synthesized aliphatic cyanogens (5.0%). Thus, sequestration and de novo synthesis are negatively correlated traits. Results suggest that losing the ability to synthesize cyanogens has restricted sara-sapho clade species to specific hosts containing SMC cyanogens and explains dietary restriction in this clade.

Simulation study of the optimal distribution of cyanide in a gold leaching circuit

The mineral industry has been using cyanidation to recover gold from ores for more than a century; however, a systematic study of the best reactant addition strategy in a cascade of agitated leaching tanks is not available in the open literature. A phenomenological mathematical model of the gold cyanidation process, calibrated with a set of industrial data from an Australian plant, together with an economic performance index is used to analyze this problem. The simulated results show that the best compromise between the two antagonistic effects, cyanide consumption and gold recovery, which are both function of cyanide concentrations, leads to a reagent distribution that depends on the leaching and cyanide consumption kinetics, pulp feed characteristics, and economic factors such as the gold market value. For the specific studied plant, in the operating range of low cyanide consumption and fast gold dissolution, all the cyanide must be added in the first tank; however, in the operating conditions of high cyanide consumption, cyanide has to be distributed in the first, second and third tanks.

Nutritive Value and Haemolytic Properties (in vitro) of the Leaves of Vernonia amygdalina on Human Erythrocyte

Vernonia amygdalina (Bitter leaf) is popularly consumed in many homes in Nigeria as a vegetable in soup preparation, while the infusion is used in folk medicine in the treatment of malaria fever. In this study, fresh leaves of Vernonia amygdalina were subjected to abrasion (to remove the bitter taste) as is normally done in soup preparation, subsequently the nutrient, anti-nutrient and zinc bioavailability of the processed and unprocessed leaf were determined. The heamolytic effect of the leaf infusion on human erythrocytes (Genotype-SS, AS, AA) was also determined. The study revealed that Vernonia amygdalina leaf has high protein (33.3%), fat (10.1%), crude fibre (29.2%), ash (11.7%), mineral (Na, K, Ca, Mg, Zn & Fe), phytate (1015.4mg/100g) and tannin (0.6%) content, while it contain low cyanide (1.1mg/kg). Abrasion of the leaf caused a significant decrease (P<0.05) in both the nutrient and antinutrient content of the leaf except in carbohydrate where there was a significant increase (P<0.05) and Mg where there was no significant change (P>0.05). The result of the calculated [Ca][phytate]/ [Zn] molar ratio (the best index for the prediction of Zn bioavailability) indicated that the phytate content of both the processed and unprocessed Vernonia amygdalina leaf will not reduce the Zn content to a critical level (0.5mol./kg). Further studies on the leaf revealed that the infusion induced the haemolysis of human erythrocyte (In vitro). Human genotype-SS (1024) were highly susceptible to haemolysis induced by Vernonia amygdalina infusion, genotype-AS moderately susceptible (512) while genotype-AA (256) is highly resistant to haemolysis induced by the same infusion. Bitter leaf has high nutrient and antinutrient content, however, abrasion will bring about a significant decrease (P<0.05) in both. The infusion of the Vernonia amygdalina leaf induces the haemolysis of mammalian erythrocyte in vitro, with Human-SS having the highest susceptibility.

Some remarks on the reactor network synthesis for gold cyanidation

Gold cyanidation in most of the plants occurs in a cascade of large tanks because this configuration offers the longest residence time and consequently the highest gold recovery. However, the long contact between the ore and the leaching solution can increases the reactants consumption by side reactions, and in some cases this conventional reactor configuration will not be the most suitable. In this paper, several configurations for a gold leaching circuit with five equal-sized reactors are investigated and the effect of different network configurations on the process performance addressed. It is showed that, for high gold content and low cyanide concentration the conventional in-series configuration is the most recommended; however, for high cyanide concentration and low gold content the in-parallel configuration is the best one. For intermediate values of gold content and cyanide concentration, hybrid configurations with parallel sections at the beginning of the circuit are the best choice. It is also showed that the optimal circuit configuration strongly depends on the gold price and cyanide cost, and for low values of cyanide price the conventional in-series configuration is the most recommended, while for high cyanide prices the hybrid and parallel configurations must be taken into account.

Cyanide-resistant respiration in Taenia crassiceps metacestode (cysticerci) is explained by the H 2O 2-producing side-reaction of respiratory complex I with O 2

The nature of the cyanide-resistant respiration of Taenia crassiceps metacestode was studied. Mitochondrial respiration with NADH as substrate was partially inhibited by rotenone, cyanide and antimycin in decreasing order of effectiveness. In contrast, respiration with succinate or ascorbate plus N, N, N′, N′-tetramethyl- p-phenylenediamine (TMPD) was more sensitive to antimycin and cyanide. The saturation kinetics for O 2 with NADH as substrate showed two components, which exhibited different oxygen affinities. The high-O 2-affinity system ( K m app = 1.5 μM) was abolished by low cyanide concentration; it corresponded to cytochrome aa 3. The low-O 2-affinity system ( K m app = 120 μM) was resistant to cyanide. Similar O 2 saturation kinetics, using succinate or ascorbate–TMPD as electron donor, showed only the high-O 2-affinity cyanide-sensitive component. Horse cytochrome c increased 2–3 times the rate of electron flow across the cyanide-sensitive pathway and the contribution of the cyanide-resistant route became negligible. Mitochondrial NADH respiration produced significant amounts of H 2O 2 (at least 10% of the total O 2 uptake). Bovine catalase and horse heart cytochrome c prevented the production and/or accumulation of H 2O 2. Production of H 2O 2 by endogenous respiration was detected in whole cysticerci using rhodamine as fluorescent sensor. Thus, the CN-resistant and low-O 2-affinity respiration results mainly from a spurious reaction of the respiratory complex I with O 2, producing H 2O 2. The meaning of this reaction in the microaerobic habitat of the parasite is discussed.

Electrochemical treatment of diluted cyanide aqueous wastes

AbstractThe electrochemical oxidation of diluted cyanide aqueous wastes has been studied in a single compartment electrochemical flow cell. It has been determined that the anode material influences greatly the process's performance. Boron doped diamond and PbO2 anodes can oxidize these wastes in the presence of both sulfate or chloride anions. On the contrary, dimensional stable anodes cannot oxidize cyanide in sulfate‐containing wastewaters, and require the presence of chloride ions. The oxidation of cyanides leads to the formation of cyanate in a first step, and later to the formation of carbon dioxide and nitrogen. There is a net consumption of hydroxyl ions during the process. Energy consumptions in the range 20–70 kWh m−3 are required to decrease the initial pollutant load by 70–80%. Global current efficiencies in the range 3–8% are obtained. These low current efficiencies are justified by the low cyanide concentrations that the wastes used in this work contain. Copyright © 2005 Society of Chemical Industry

Cyanide Distribution in Human Tissue, Determined by GC/ECD/HS

Cyanide is an important acute poison in forensic sciences. Cyanide determination is in general performed in a blood sample. We have developed a gas chromatography procedure with electron capture detector and headspace equipment (GC/ECD/HS) for the detection of cyanide and studied cyanide distribution in various tissues in the human body, such as blood, liver, kidney, brain, urine, and stomach content. Furthermore, in a rabbit animal model, cyanide tissue distribution is determined using the developed method. A calibration curve is constructed between 0.2–3 µg/mL, R2 = 0.9958. Linearity is lost above 3 µg/mL. The average recovery is 84.6% (n = 8, RSD 6.39%), calculated from standard addition. The limit of detection is 0.5 ng/mL, calculated from 3 times the signal/noise signal. In humans, low cyanide concentrations (<1 µg/mL) are observed in liver and urine, making these tissues less interesting for cyanide determination. In the rabbit animal model, tissue cyanide concentrations increase with increasing cyanide administration. A large intertissue variation is observed, with high cyanide concentration in blood, spleen, and stomach content. Spleen tissue can offer a valuable alternative for diagnosing cyanide intoxication in the absence of blood due to comparable spleen tissue concentration to blood concentration. We gratefully acknowledge the support from the National Nature Science Foundation of China (20375005).