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排序方式: 共有290条查询结果,搜索用时 15 毫秒
1.
Fungisai Matemadombo 《Electrochimica acta》2007,52(24):6856-6864
Cobalt and iron phenylthiosubstituted phthalocyanines have been deposited on Au electrode surfaces through the self-assembled monolayer (SAM) technique. The so formed layers were studied using voltammetric and impedance techniques. These SAMs blocked a number of Faradic processes and electrocatalyzed the oxidation of nitrite. The electrocatalytic parameters of the cobalt and iron phenylthiosubstituted phthalocyanines deposited on Au electrodes in nitrite solution were studied. Nitrite overpotentials which are lower than ever reported were obtained in this work for the iron phenylthiosubstituted phthalocyanines with very high stability. 相似文献
2.
目的 建立柱后衍生-离子色谱-紫外检测法测定食品中亚硝酸盐含量的分析方法。方法 样品用水进行超声提取,采用亚铁氰化钾-乙酸锌溶液沉淀后离心过滤,样品溶液中的亚硝酸盐经离子色谱分离后在酸性条件下与对氨基苯磺酸及N-(1-萘基)-乙二胺二盐酸盐偶合生成紫红色染料,紫外检测器在538 nm波长下检测,外标法定量。结果 以KOH溶液为流动相,亚硝酸盐在0.001~0.100 mg/L质量浓度范围内线性良好,检出限低至0.05mg/kg,食品样品中亚硝酸盐的加标回收率在90.4%~109.0%之间,6次重复测量的相对标准偏差均小于10%。结论 本方法具有灵敏度高、特异性强、前处理简便等优点,适合于各种类型样品中亚硝酸盐的检测。 相似文献
3.
Johanna Suomi Jukka Ranta Pirkko Tuominen Tiina Putkonen Christina Bäckman Marja-Leena Ovaskainen 《Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment》2016,33(1):41-53
Nitrite intake from the consumption of cured meat and tap water was estimated for Finnish children of 1, 3 and 6 years as well as Finnish adults of 25–74 years. Nitrite content in the foods was measured by capillary electrophoresis, and was then used together with individual food consumption data from the FINDIET 2007 and DIPP studies in a stochastic exposure assessment by a Monte Carlo Risk Assessment (MCRA) program. Nitrite intake from additive sources and tap water was assessed, and more than every 10th child between the ages 3 and 6 years was estimated to have a nitrite intake exceeding the acceptable daily intake (ADI) of nitrite. The high exposure levels were caused by frequent consumption of large portions of sausages, up to 350 g day–1 or 750 g in 3 days, among the children. Median nitrite intake from cured meat was 0.016, 0.040, 0.033 and 0.005 mg kg–1 body weight day–1 for children of 1, 3 and 6 years and adults, respectively. Bayesian estimation was employed to determine safe consumption levels of sausages and cold cuts for children, and these results gave rise to new national food consumption advice. 相似文献
4.
Zinc protoporphyrin is formed in pork homogenates in both enzymatic and non-enzymatic reactions. Ferrochelatase is active in formation of the highly fluorescent pigment known from Parma ham as demonstrated by inhibition with N-methylmesoporphyrin and by thermal inactivation. A non-enzymatic transmetallisation reaction, exchange of iron in myoglobin by zinc(II), is demonstrated by Pb(II) inhibition of zinc protoporphyrin formation at low Pb(II) concentrations, but promoted at higher Pb(II) concentrations. The non-enzymatic reaction is characterised as a slow bimolecular reaction between protoporphyrin IX and zinc(II) with a second-order rate constant of 0.63 l mol−1 s−1 at 35 °C and a high energy of activation of 98 kJ mol−1 for acetone:water (3:1, v/v) as solvent. Zinc protoporphyrin formation is concluded to be thermodynamically controlled with a formation constant of 4 × 105 M (35 °C, acetone:water (3:1)). An efficient inhibition of formation of zinc protoporphyrin by nitrite is related to myoglobin as substrate and involves both enzymatic and non-enzymatic reactions. 相似文献
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Nitrite tolerance and nitrite reduction in lactic acid bacteria associated with cured meat products 总被引:1,自引:0,他引:1
Karen L. Dodds David L. Collins-Thompson 《International journal of food microbiology》1984,1(3):163-170
The effect of 0, 50, 100 and 200 μg/ml of nitrite on the growth of isolated and reference strains of lactic acid bacteria associated with cured meat products was studied in broth cultures and the presence of an active nitrite reductase enzyme system in these strains was determined. Half of the 10 reference strains and 16 of 25 isolated strains were resistant to all levels of nitrite tested Strains which did not show a significant decrease in growth rate or cell yield in the presence of 200 μg/ml of nitrite under anaerobic conditions were homofermentative. All heterofermentative strains showed a decrease in growth rate or cell yield or both. Inhibition due to nitrite increased as the concentration increased and was greatest under anaerobic conditions. Enzymatic ability to reduce nitrite was detected in 5 homofermentative and 1 heterofermentative strains. The presence of an active nitrite reductase enzyme system in lactic acid bacteria was not related to their resistance to nitrite. 相似文献
8.
9.
Wei-Hsiang Chen 《Water research》2009,43(12):3047-87
N-Nitrosodimethylamine (NDMA) is formed during chlorination of water containing the herbicide diuron (N′-(3,4-dichlorophenyl)-N,N-dimethylurea) but formation is greatly enhanced in the presence of ammonia (chloramination). Groundwater impacted by agricultural runoff may contain diuron and relatively high total nitrogen concentrations; this study examines the impact of the nitrogen form (ammonium, nitrite or nitrate) on NDMA formation during chlorination of such waters. NDMA formation during chlorination of diuron increased in the order nitrite < nitrate < ammonium for a given chlorine, nitrogen, and diuron dose. Formation of dichloramine seemed to fully explain enhanced NDMA formation in the presence of ammonium. Nitrate unexpectedly enhanced nitrosation of diuron derivatives to form NDMA compared to the cases of no added nitrogen or nitrite addition. Nitrite addition is less effective because it consumes more chlorine and produces intermediates that react rapidly with diuron and its aromatic byproducts. Differences between surface water and groundwater in nitrogen forms and concentrations and disinfection approaches suggest strategies to reduce NDMA formation should vary with drinking water source. 相似文献
10.
Incubation of curing brines for the production of ready-to-eat, uncured, no-nitrite-or-nitrate-added, ground, cooked and sliced ham 总被引:1,自引:0,他引:1
Salt concentration, vegetable juice powder (VJP) concentration and temperature were investigated to determine necessary conditions for incubation of curing brines including VJP and a starter culture containing Staphylococcus carnosus prior to production of naturally cured, no-nitrate/nitrite-added meat products. Subsequently, incubated brines were utilized to produce no-nitrate/nitrite-added sliced ham in which quality characteristics and residual nitrite concentrations were measured to determine feasibility of brine incubation for nitrate conversion prior to injection. Two ham treatments (one with VJP and starter culture; one with pre-converted VJP) and a nitrite-added control were used. No differences (P>0.05) were found for color in the VJP treatments. Control sliced ham was redder after 42 days of storage, retaining significantly (P<0.05) greater a* (redness) than either of the VJP treatments. Residual nitrite concentration was greater (P<0.05) in the control hams during the first week of storage. While the nitrite-added control retained greater red color and initially had more residual nitrite than the VJP treatments, the two VJP treatments did not differ from each other. 相似文献