A Light‐Induced Phase Exhibiting Slow Magnetic Relaxation in a Cyanide‐Bridged [Fe4Co2] Complex
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Einzelmolkülmagnete: Ein Cyanid-verbrückter sechskerniger Eisen(III)-Cobalt(II)-Komplex Komplex zeigt bei 220 K einen Spinübergang, der an einen thermischen Elektronentransfer gekoppelt ist. Lichteinstrahlung bei tiefer Temperatur (LT; HT=hohe Temperatur) erzeugt einen metastabilen Zustand, der beim Messen der magnetischen Suszeptibilität (χm; siehe Bild) langsame magnetische Relaxation aufwies.철결핍빈혈에서 cobalt 배설율검사의 진단적 가치를 검토할 목적으로 1974년 4월부터 1976년 4월까지 서울대학교 의과대학 부속병원 내과와 원자력병원에 입원하였던 철결핍성빈혈 22예, 재생불량성빈혈 3예, 용혈성빈혈 2예, 기타 각종질환 58예, 대조군 11예, 총계 96예를 대상으로 58CoCl2는 이용하여 cobalt 배설율검사를 시행하는 한편, 적혈구형태, 적혈구지수, 혈청철, 총철결합능, 골수철검사와 비교관찰하여 다음과 같은 결론을 얻었다. 1) 철대사와 혈액학적으로 정상이라고 생각되는 대조군의 6시간 cobalt 배설율은 평균 2.8±1.77%(1.0∼6.8%)이었으며, 24시간 cobalt 배설율은 평균 6.1±4.31%(1.9∼15.2%)였다. 2) 철결핍성빈혈의 경우에는 6시간 cobalt 배설율이 평균 18.3±5.88%(10.2∼25.0%)이었으며, 24시간 cobalt 배설율은 평균 41.8±6.83%(29.0∼54.5%)로서 대조군과 비교하여 6배이상 증가돼 있었다. 3) 골수철함량이 정상인 증례에서는 빈혈이 유무에 관계없이 6시간 및 24시간 cobalt 배설율은 모두 대조군과 유의한 차이가 없었다. 4) 6시간 cobalt 배설율과 24시간 cobalt 배설율간에는 밀접한 상관관계를 볼 수 있었으나, 실제적인 면에 있어서는 24시간 cobalt 배설율검사가 더 정확한 것으로 생각되었다. 5) 골수철함량이 정상인 증례의 24시간 cobalt 배설율은 1.2∼26.6%의 동요범위를 보인 반면, 철결핍성빈혈예의 24시간 cobalt 배설율은 29.0∼54.5%의 동요범위를 보였으며 양군간에 중복을 볼 수 없었다. 그러므로 빈혈환자에서 24시간 cobalt 배설율이 27%이상이면 철결핍성빈혈을 의심할 수 있는 것으로 생각되었다. 6) Cobalt 배설율은 골수철함량이 감소함에 따라 대체로 증가하는 경향을 보였으나 상당한 중복을 볼 수 있었고, 특히 골수철함량이 1+인 경우는 철결핍이나 골수철함량이 정상인 경우와 중복되어 통계학적으로 유의한 차이를 볼 수 없었다. 7) 골수철검사로 확인된 철결핍성빈혈의 경우, cobalt 배설율은 전예에서 증가된 반면, 적혈구형태는 40%에서, 적혈구지수는 30∼60%에서, transferrin 포화율은 70%에서 이상소견을 보였다. 이상의 성적을 종합하면 cobalt 배설율검사는 철결핍성빈혈을 진단하는데 간단하고 민감하며 정확한 검사법으로 골수철검사의 실제적인 대체검사로 이용될 수 있는 것으로 생각된다.
Cobalt extraction techniques
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Total cyanide analysis by distillation is used most commonly to assess cyanide content of water samples. This manual method is robust but slow and provides no information about cyanide speciation, a significant limitation in that cyanide species have substantially different toxicity characteristics. Seven alternative methods for the analysis of cyanide species or groups of species were evaluated in reagent water and five different contaminated water matrices, including five species-specific methods − weak acid dissociable (WAD) cyanide, free cyanide by microdiffusion, available cyanide, automated WAD cyanide by thin film distillation, metal cyanides by ion chromatography − and two automated techniques for total cyanide − total cyanide by thin film distillation and total cyanide by low-power UV digestion. The species-specific cyanide analytical techniques achieved low, ppb-level detection limits and exhibited satisfactory accuracy and precision for most contaminated waters. Analysis of low concentrations of cyanide species in raw wastewater was problematical for the available cyanide and ion chromatography methods, which experienced significant interference problems and/or low recoveries. There was recovery of significant diffusible cyanide in microdiffusion tests with nickel-cyanide-spiked samples, reflecting dissociation of this weak metal-cyanide complex during the test and demonstrating that the test can recover some fraction of WAD cyanide in addition to free cyanide. The automated total cyanide methods, which involve UV digestion, achieved low detection limits for most waters but exhibited low recoveries for some waters.
Hydrogen cyanide
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This paper reviewed the physical and chemical properties of cyanide species - free cyanide and iron-cyanide complexes, and the potential of cyanide phytoremediation with reference to the phytotoxicity of free cyanide and iron-cyanide complexes in plants. There are three possible pathways, which are β-cyanoalanine synthase, sulfur transferase and formamide hydrolase pathways, for transforming and assimilating endogenous free cyanide in plants. Iron-cyanide complexes are generally resistant to microbial and fungal degradation. It is suggested that there may be undiscovered degradation pathways involved in assimilating iron-cyanide complexes in plants; however the detailed pathways of assimilation of iron-cyanides are still unknown. While uptake of free cyanide is mainly by simple diffusion, as iron-cyanide complexes are membrane-impermeable, it is suggested that the complexes may be transported into the plants through the mode of protein mediated uptake. Upon uptake, biological fates of cyanide species vary with different species of cyanide, depending on their chemical properties and concentrations. Phytotoxicity of free cyanide in plants is much higher than that of iron-cyanide complexes as plants could generally withstand a higher concentration of iron-cyanide complexes comparing with free cyanide. However, it is still unsure if the iron-cyanide complexes are toxic themselves or if they disrupt the metabolism of plants indirectly. It is known that endogenous cyanogenic compounds play a role in providing sources of nitrogen and acting as precursors in some biochemical processes in plants. Studies suggested that exogenous cyanide species, to a certain extent, could benefit the plants through providing nutrition to them. However, there is still no study conclusively indicates that there is a direct acquisition of exogenous cyanide species by plants as their alternative source of nitrogen. Further investigations on the degradation pathways of iron-cyanide complexes and the essential enzymes involved in phyto-assimilation of iron-cyanide complexes are required for better understanding of the degradation and assimilation pathways of cyanogenic compounds in plants.
Hydrogen cyanide
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SUMMARY Cobalt, as cobalt sulphate and cobalt-EDTA, was applied to pastures at 15 sites in south-east Scotland. Herbage cobalt and extractable soil cobalt concentrations were monitored at these sites over the period 1978–81. Although the sites were located in a generally cobalt-deficient area, considerable variation between sites was observed both in the concentration of cobalt present in untreated pasture and in the response to cobalt additions. There was no significant correlation between herbage cobalt concentrations and soil cobalt status as determined by acetic acid extraction. Application of cobalt sulphate (6 kg/ha) increased herbage cobalt concentrations at all sites but at several sites the response was short-lived. In general, cobalt-EDTA was less effective than cobalt sulphate in increasing herbage cobalt concentrations. Extractable soil cobalt concentrations of the control areas showed some variability between samplings, but the variability was much greater for the cobalt-treated plots. Cobalt applied to pastures was found to accumulate in the top 0–4 cm layer of soil and penetrated deeper only in soils of low pH. Overall, only a third of the cobalt applied to pastures as cobalt sulphate was recovered by acetic acid extraction of the soil and less than 20% of the cobalt applied as cobalt-EDTA.
Cobalt extraction techniques
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Methemoglobin
Absorbance
Spectrophotometry
Cyanide Poisoning
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It is well known that cyanide is an extremely toxic lethal poison with human death within minutes after exposure to only 300 ppm cyanide. On the other hand, cyanide is released into the environment (mainly through waste water) every day from various human activities. Therefore, rapid, sensitive and cost-effective cyanide trace detection is an urgent need. Surface-enhanced Raman scattering (SERS) is a method that meets these requirements. It should be noted, however, that in this technique SERS substrates, which are usually made of gold or silver, will be leached with aqueous cyanide by the formation of complexes between gold or silver with cyanide. This will cause the SERS spectrum of cyanide to be modified. When determining cyanide concentrations by SERS analysis, this spectral modification should be taken into account. This report presents the SERS spectral modification of aqueous cyanide traces (in ppm and lower concentration range) when the SERS substrates used are flower-like silver micro-structures.
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Pillar
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Cyanide, an EPA priority pollutant and target analyte, is typically measured as total. However, cyanide complexation, information which is not acquired through total cyanide analysis, is often a driver of cyanide toxicity and treatability. A case study of a former manufacture gas plant (MGP) is used to demonstrate the usability of various cyanide analytical methods for risk and treatability assessments. Several analytical methods, including cyanide amenable to chlorination and weak acid dissociable cyanide help test the degree of cyanide complexation. Generally, free or uncomplexed cyanide is more biologically available, toxic, and reactive than complexed cyanide. Extensive site testing has shown that free and weakly dissociable cyanide composes only a small fraction of total cyanide as would be expected from the literature, and that risk assessment will be more realistic considering cyanide form. Likewise, aqueous treatment for cyanide can be properly tested if cyanide form is accounted for. Weak acid dissociable cyanide analyses proved to be the most reliable (and potentially acceptable) cyanide method, as well as represent the most toxic and reactive cyanide forms.
Cyanide Poisoning
Hydrogen cyanide
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