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331.
通过对比实验,选用柠檬酸钠做络合剂,实现了在碱性介质中用原子吸收光谱测定铅的方法。应用该方法测定实际样品的结果与其他方法相符,对于2.19mg/L Pb浓度的试液10次测定的RSD为1.8%。 相似文献
332.
T. H. Papenbrock F. Stuhl K. P. Müller J. Rudolph 《Journal of Atmospheric Chemistry》1992,15(3-4):369-379
A latitudinal profile (30° W, from 30° N to 30° S) of mixing ratios of nitric acid and particulate nitrate was determined on the Atlantic Ocean during the Polarstern cruise ANT VII/1 from Bremerhaven, Germany, to Rio Grande, Brazil. The detection of HNO3 was performed simultaneously by laser-photolysis fragment-fluorescence (LPFF) and by nylon filter packs. The detection limit was about 30 pptv for a signal accumulation time of 1 h for LPFF and about 5 pptv for the filters at a collection time of 4 h. In general, the mixing ratios of HNO3 in the Northern Hemisphere were found to be significantly higher than those in the Southern Hemisphere. The Atlantic background concentrations frequently varied between 80 pptv and the detection limit. Larger deviations from this trend were found for the more northern latitudes and for episodes like crossings of exhaust plumes from ships or from continental pollutions sources. 相似文献
333.
W. R. Hartmann M. Santana M. Hermoso M. O. Andreae E. Sanhueza 《Journal of Atmospheric Chemistry》1991,13(1):63-72
Formic and acetic acids were measured in a scrub-grass savanna and in a nearby semideciduous forest. Gaseous HCOOH and CH3COOH were collected using the mist-scrubber technique, and were determined using ion chromatography. A strong diurnal cycle was observed at both sites, with higher mixing ratios during daytime. Concentrations in the savanna were always higher than in the forest. Most of the time HCOOH/CH3COOH ratios greater than one were recorded at the savanna site, and ratios less than one at the forest site. Boundary-layer mixing ratios in the savanna region, derived from measurements during midday, are 1.3±0.4 ppbv and 0.7±0.3 ppbv for HCOOH and CH3COOH. Dry depositions velocities between 0.5 and 1 cm s-1 were estimated for the savanna region. Atmospheric residence times of <3 days and >5 days were estimated for the rainy and dry season, respectively. 相似文献
334.
钽钼酸—丁基罗丹明B—PVA体系光度法测定痕量钽 总被引:1,自引:0,他引:1
Ta(V)与钼酸盐在pH3.7形成钽钼酸,并在0.29mol/L的H_2SO_4介质中,与丁基罗丹明B(BRHB)形成离子缔合物,其组成比为Ta:Mo:BRHB=1:6:3。有聚乙烯醇(PVA)存在时,该缔合物能稳定存在于水溶液中。缔合物的最大吸收在588nm,ε_(588)=3.62×10~5L·mol~(-1)·cm~(-1),Ta在0—5μg/25ml范围符合比尔定律。方法应用于硅酸盐岩石中痕量Ta的测定,结果满意。 相似文献
335.
T. Huthwelker Th. Peter B. P. Luo S. L. Clegg K. S. Carslaw P. Brimblecombe 《Journal of Atmospheric Chemistry》1995,21(1):81-95
Henry's law constants KH (mol kg–1 atm–1) for the reaction HOCl(g)=HOCl(aq) near room temperature, literature data for the associated enthalpy change, and solubilities of HOCl in aqueous H2SO4 (46 to 60 wt%) at temperatures relevant to the stratosphere (200 KT230 K) are shown to be thermodynamically consistent. Effective Henry's law constants [H*=mHOCl/pHOCl, in mol kg–1 atm–1] of HOCl in aqueous H2SO4 are given by: ln(H*)=6.4946–mH2SO4(–0.04107+54.56/T)–5862 (1/To–1/T) where T(K) is temperature and To=298.15K. The activity coefficient of HOCl in aqueous H2SO4 has a simple Setchenow-type dependence upon H2SO4 molality. 相似文献
336.
C. Hill 《Environmental Geology》1995,25(1):16-23
Hydrocarbons, native sulfur, Mississippi Valley-type (MVT) deposits, and sulfuric acid karst in the Delaware Basin, southeastern New Mexico, and west Texas, USA, are all genetically related through a series of sulfur redox reactions. The relationship began with hydrocarbons in the basin that reacted with sulfate ions from evaporite rock to produce isotopically light (
34S = -22 to -12) H2S and bioepigenetic limestone (castiles). This light H2S was then oxidized at the redox interface to produce economic native sulfur deposits (
34S = -15 to +9) in the castiles, paleokarst, and along graben-boundary faults. This isotopically light H2S also migrated from the basin into its margins to accumulate in structural (anticlinal) and stratigraphic (Yates siltstone) traps, where it formed MVT deposits within the zone of reduction (
34S = -15 to +7). Later in time, in th zone of oxidation, this H2S reacted with oxygenated water to produce sulfuric acid, which dissolved the caves (e.g., Carlsbad Cavern and Lechuguilla Cave, Guadalupe Mountains). Massive gypsum blocks on the floors of the caves (
34S = -25 to +4) were formed as a result of this reaction. The H2S also produced istopically light cave sulfur (
34S = -24 to -15), which is now slowly oxidizing to gypsum in the presence of vadose drip water. 相似文献
337.
本研究将交叉引物恒温扩增技术(cross priming amplification,CPA)与核酸试纸条相结合建立一种副溶血性弧菌(Vibrio parahaemolyticus)快速可视化检测方法。针对副溶血性弧菌特有的不耐热溶血素基因tlh的六个不同区域设计两对特异性引物和一对检测探针,通过优化反应条件确定了最佳反应体系。CPA-核酸试纸条方法对副溶血性弧菌的检测具有较强的特异性,对纯培养物的检测灵敏度达到58 cfu/m L,对污染牡蛎中副溶血性弧菌的检测灵敏度为5.2 cfu/g,比传统的PCR技术灵敏度提高了10倍,且具有较高的稳定性。交叉引物恒温扩增技术与核酸试纸条相结合的方法操作简便、特异性强、灵敏度高且能有效防止污染,可用于现场及基层单位副溶血性弧菌的快速检测。 相似文献
338.
This study aims to quantify the effects of different pretreatment methods on the stable carbon isotope values of fatty acids in marine microalgae(Isochrysis zhanjiangenisis).To identify the effects of sample preparation on theδ~(13)C value and the fatty acid composition,we examined eight types of pretreatment methods including:(a) drying the sample followed by direct methyl esterification using HCl-CH_3OH;(b) drying the sample followed by direct methyl esterification using H_2SO_4-CH_3OH;(c) drying the sample by ultrasonic extraction and methylesterification using HCl-CH_3OH;(d) drying the sample by ultrasonic extraction and methyl-esterification using H_2SO_4-CH_3OH;(e) fresh sample followed by direct methyl-esterification using HCl-CH_3OH;(f) fresh sample followed by direct methyl-esterification using H_2SO_4-CH_3OH;(g) fresh sample with ultrasonic extraction followed by methyl-esterification using HCl-CH_3OH,and(h) fresh sample with ultrasonic extraction followed by methylesterification using H_2SO_4-CH_3 OH.The results show that the δ~(13)C values from Groups a–e,g and h fluctuated within 0.3‰,and the δ~(13)C values of Group f were approximately 0.7‰ lower than the other seven groups.Therefore,the different sample pretreatment methods used towards the extraction of fatty acids from marine microalgae may result in different results regarding the stable carbon isotope ratios,and if necessary a correction should be applied. 相似文献
339.
340.
由邻羟基苯甲酸、1,4—苯二酚和溴素起始,经溴代、氧化—溴代、形成酰氯和酰化等步骤,合成了三种新的多溴代邻羟基苯甲酸—2,3,5,6—四溴—1,4—苯二酯。通过对产物溴含量、IR和1HNMR的分析,验证了产物的结构 相似文献