HE 9972 1型COD测定仪专用试剂包的配制

对用作氧化及消解水样并与HE 99721型COD测定仪配套专用的混合试剂溶液的组成进行了试验,最终确定下列组成的混合试剂可适合于代替进口的HI 99955试剂包:0.05 mol·L-1重铬酸钾溶液0.75 mL,硫酸银-硫酸溶液(浓硫酸500 mL中含4 g硫酸银)1.8 mL及硫酸汞-硫酸溶液(3 mol·L-1硫酸溶液20 mL中含4 g硫酸汞)0.15 mL,用此自己配制的混合试剂代替进口的试剂包测定了有机废水样品中COD浓度(小于150 mg·L-1),结果表明:分别用两种混合试剂在同一台COD测定仪上所测得结果之间不存在显著差异.     

金属材料分析方法的选择和施行第五讲金属材料中钨的测定

2.1.2　GB 7731.1-1987 钨酸沉淀重量法测定钨铁中钨量适用范围:钨铁中钨的测定测定范围:钨量w(W)>65%方法提要:(1) 试样的溶解　称取通过 0.088 mm筛孔的试样1.000 0 g置于铂坩埚中,加入浓氢氟酸5 mL,滴加浓硝酸分解试样。加入硫酸(1+1) 15 mL,小心蒸发至冒浓三氧化硫白烟,冷却,加入浓盐酸10 mL及热水30 mL使可溶的盐类溶解。用紧密滤纸过滤,滤液接受于600 mL烧杯中,用盐酸(1+9)洗涤沉淀及滤纸。滴加适量氨水(1+1)将滤纸上的钨酸沉淀溶解,用 20 g·L-1 氯化铵溶液洗涤残渣及滤纸。以上的盐酸洗液、溶解钨酸的氨水及氯化铵洗液均与600 m…     

金属材料分析方法的选择和施行：第五讲 金属材料中钨的测定（续）

此外,尚有二硫酚、邻羟基酚类试剂、酸性三苯甲烷类试剂、偶氮类试剂以及荧光酮类试剂等也都有应用于钨的光度测定的实例。但由于共存元素的干扰以及方法的成熟程度等问题尚未完全得到解决,在金属材料分析中的应用尚不普遍。其中,苯基荧光酮类试剂对钢铁中低含量钨的测定有一定的应用前景,举两例说明:例1:邻氯苯基荧光酮(o-Cl-PF)-CTMAB光度法测定钢及合金中低含量钨[w(W)0.01%~0·50%]。称取试样0.100 0~0.200 0 g,溶于硫酸-磷酸混合酸(H2SO4+H3PO4+H2O=3+10+12)10 mL中,滴加浓硝酸约1 mL氧化,蒸发至冒白烟,冷却,加水溶解盐类后冷…     

痕量汞的气热提取应用于现场快速分析污水

为测定污水中汞含量,取约25mL水样,加入硫酸亚锡和氨基磺酸的混合物(质量比3∶1)0.40g,反应15min,使汞(Ⅱ)还原为气态单质汞,以0.3L·min~(-1)流量将汞蒸气引入由碘酸钾和硫酸氢铵的混合物(质量比1∶4)0.20g,约5 mL去离子水和1 mol·L~(-1)硫酸溶液0.100mL组成的吸收液中,使单质汞氧化成汞(Ⅱ),随即向此溶液中加入含有镉试剂的汞检测剂0.10g,使汞(Ⅱ)反应显色,2min后进行测定。显色反应时,所加入的汞检测剂中含有氢氧化钠和四硼酸钠组成的缓冲剂(相当于2mol·L~(-1)氢氧化钠溶液0.1mL和四硼酸钠0.04g),曲拉通X~(-1)00(相当于体积分数为10%的曲拉通X~(-1)00溶液30μL)和镉试剂(相当于1g·L~(-1)镉试剂乙醇溶液60μL)。按上述操作流程结合使用便携式专用仪器可在20min内完成一次测定,方法的检出限(3s/k)为2μg·L~(-1)。分别对0.050,0.500mg·L~(-1)汞标准溶液进行精密度试验,测定值的相对标准偏差(n=6)分别为3.6%,5.1%。方法用于废水样品的分析,并进行加标回收试验,测得回收率为92.0%～103%。     

金属材料分析方法的选择和施行 第六讲 金属材料中稀土元素的测定（续）

镍铬合金试样的溶解:称取试样0.1000g置于125 mL锥形瓶中,溶于王水3～5 mL中,加入浓高氯酸1～1.5 mL,蒸发至冒烟并呈重铬酸盐的砖红色,随即乘热滴加浓盐酸使铬(Ⅵ)以氯化铬酰(CrO2Cl2↑)形态挥发除去.     

D_(206)阴离子交换树脂微柱富集光度法测定湖水中痕量铬(Ⅵ)

用D206阴离子交换树脂填充的微交换柱,从酸度为0.05 mol.L-1硫酸的试样溶液中分离并富集痕量铬(Ⅵ)。试液以2 mL.min-1流量通过交换柱,用0.05 mol.L-1硫酸溶液0.5 mL淋洗交换柱两次,然后用0.5 mol.L-1氢氧化钠溶液及2 mol.L-1氯化钠溶液的混合溶液3 mL分3次洗脱吸附于交换柱上的铬(Ⅵ),洗脱液接受于25 mL容量瓶中,在0.5 mol.L-1硫酸溶液中,加入1.5 mol.L-1磷酸溶液0.5 mL作掩蔽剂后,用二苯碳酰二肼试剂显色光度法测定铬(Ⅵ)含量。     

火焰原子吸收光谱法测定钒基合金中铬的含量

应用火焰原子吸收光谱法(FAAS)测定钒基合金(V-Cr-Ti三元合金)中铬的含量。取样0.100 0g,用硫酸(1+1)溶液5mL及硝酸2 mL加热溶解后蒸发至冒硫酸烟。冷却后移至100mL容量瓶中,加水定容。分取适量样品溶液(其中含Cr约为0.1～0.5mg)置于另一100mL容量瓶中,加入20g·L~(-1)硫酸钾溶液10mL(作为对共存元素V和Ti的抗干扰试剂,同时起到增敏作用明显提高信号强度),加水定容为100.0mL(溶液中含硫酸0.5%),按仪器工作条件测定溶液中铬的含量。在优化的试验条件下,铬的质量浓度在1.00～5.00mg·L~(-1)内与相应的吸光度之间呈线性关系。应用此方法测定了实际样品中铬的含量,测定值的相对标准偏差(n=6)为0.64%,以实际样品为基体,按照标准加入法在2个浓度水平上进行回收试验,测得回收率的平均值为97.1%。     

金属材料分析方法的选择和施行第四讲金属材料中钛的测定(续)

2.4　铝钛中间合金中钛的测定(此方法由上海材料研究化学分析研究室提供)测定范围:w(Ti)≥1%方法提要:试样0.5000g,置于500ml锥形瓶中,加入盐酸(1+1)20ml,作用缓慢时加热至试样全溶,滴加过氧化氢(ρ1.11g·ml-1)3～5滴,煮沸。如溶液不清,过滤至另个500ml锥形瓶中,用盐酸(5+95)洗涤沉淀及滤纸。如沉淀中有不溶性钛的化合物存在,须将沉淀及滤纸置于铂坩埚中灰化,用焦硫酸钾熔融,熔块用稀硫酸浸出后并入于主液中。加硫酸(ρ1.84g·ml-1)5ml,加热蒸发至冒硫酸烟,冷却,加盐酸(1+1)100ml,加热溶解盐类,加水至约150ml,加入碳酸氢钠2g和铝片2g,随即…     

光度法测定药物中卡托普利的含量——基于对铁(Ⅲ)-钛铁试剂络合物的还原褪色反应

卡托普利分子中的巯基(-SH)能还原三价铁至二价状态,试验发现铁(Ⅲ)与钛铁试剂络合物的色泽由于卡托普利的存在而出现消褪。确定了铁(Ⅲ)与钛铁试剂的反应条件:于25mL的容量瓶中依次加入0.250 0g·L-1铁(Ⅲ)溶液2.20mL,6.25g·L-1钛铁试剂溶液0.6mL及pH 3.0Clark-Lubs缓冲溶液10.0mL,加水定容,于80℃水浴中加热20min使显色完全。在其吸收峰670nm处测量吸光度A1。在此反应体系中加入不同浓度的卡托普利标准溶液,按相同步骤操作并测得其吸光度A2,结果表明:A1与A2之差(ΔA)与卡托普利的质量浓度在0.012~0.036g·L-1范围内呈线性关系。将此方法应用于卡托普利片剂中卡托普利含量的测定,所得测定值与用药典法测定的结果相符。     

纳氏试剂分光光度法测定土壤中全氮含量

提出了纳氏试剂分光光度法测定土壤中全氮含量。以硫酸铜为加速剂,用硫酸对土壤样品进行消解。消解完毕的溶液用400g·L-1氢氧化钠溶液调节其酸度至pH 10左右,溶液与沉淀一起移入容量瓶中,定容至200mL。移取上清液10mL于50mL比色管中,加入酒石酸钾钠溶液作掩蔽剂,加入纳氏试剂显色后,加水定容,于波长420nm处测量其吸光度并计算土壤样品中全氮含量。氮的质量浓度在2mg·L-1以内与吸光度呈线性关系。方法用于土壤样品分析,测定值与滴定法测定值相符,测定值的相对标准偏差(n=10)为0.24%;回收率在92.3%~112%之间。     

Generation and detection of levuglandins and isolevuglandins in vitro and in vivo

Levuglandins (LGs) and isolevuglandins (isoLGs), formed by rearrangement of endoperoxide intermediates generated through the cyclooxygenase and free radical induced oxidation of polyunsaturated fatty acids (PUFAs), are extraordinarily reactive, forming covalent adducts incorporating protein lysyl ε-amino groups. Because they accumulate, these adducts provide a dosimeter of oxidative injury. This review provides an updated and comprehensive overview of the generation of LG/isoLG in vitro and in vivo and the detection methods for the adducts of LG/isoLG and biological molecules in vivo.     

Enthalpies of solution of purine and adenine in water and in dimethylsulfoxide

Journal of Solution Chemistry - Enthalpies of solution of purine and adenine in water and in demethylsulfoxide were measured calorimetrically in the temperature range 25–40°C. ΔH s...     

Coassembly of Nanorods and Nanospheres in Suspensions and in Stratified Films

The entropically driven coassembly of nanorods (cellulose nanocrystals, CNCs) and nanospheres (dye‐labeled spherical latex nanoparticles, NPs) was studied in aqueous suspensions and in solid films. In mixed CNC‐latex suspensions, phase separation into an isotropic latex‐NP‐rich and a chiral nematic CNC‐rich phase took place; the latter contained a significant amount of latex NPs. Drying the mixed suspension resulted in CNC‐latex films with planar disordered layers of latex NPs, which alternated with chiral nematic CNC‐rich regions. In addition, fluorescent latex NPs were embedded in the chiral nematic domains. The stratified morphology of the films, together with a random distribution of latex NPs in the anisotropic phase, led to the films having close‐to‐uniform fluorescence, birefringence, and circular dichroism properties.     

Determination of diazepam and nordazepam in milk and plasma in the presence of oxazepam and temazepam

For studies on the excretion of drugs into milk a sensitive high-performance liquid chromatographic assay was developed to quantitate diazepam and nordazepam in the milk and plasma of humans and rabbits in the presence of their major metabolites, oxazepam and temazepam. Flurazepam was used as an internal standard. The assay involves extractions with diethyl ether and an additional acid clean-up step. Chromatographic separation was achieved by a LiChrospher 60 RP-select B (5 microns) column and KH2PO4- acetonitrile (69:31, v/v) adjusted to pH 2.80 as a mobile phase. The same extraction and chromatographic conditions were suited to both types of samples, milk and plasma. The limits of determination using ultraviolet detection at 241 nm was for diazepam 20 ng/ml and for nordazepam 15 ng/ml. The absolute recoveries of diazepam, nordazepam and flurazepam in human milk were 84, 86 and 92% and in human plasma 97, 89 and 94%, respectively. The within- and between-day accuracy and precision for diazepam and nordazepam in milk and plasma at all concentrations tested (20-1500 ng/ml) were better than 8%. The high fat content which occurs in rabbit milk presented no limitation for the extraction of lipophilic diazepam: the method was successfully used to monitor milk and plasma concentrations of diazepam and nordazepam in lactating New Zealand White rabbits during 26-h infusions of diazepam (1.4 mg/h).     

Comparison and correlation of in vitro, in vivo and in silico evaluations of alpha, beta and gamma cyclodextrin complexes of curcumin

In the present study investigated the effect of curcumin (CUR) alpha (α), beta (β) and gamma (γ) cyclodextrin (CD) complexes on its solubility and bioavailability. CUR the active principle of turmeric is a natural antioxidant agent with potent anti-inflammatory activity along with chemotherapeutic and chemopreventive properties. Poor solubility and poor oral bioavailability are the main reasons which preclude CUR use in therapy. Extent of complexation was β-CD complex (82 %) > γ-CD (71 %) > α-CD (65 %). Pulverization method resulted in significant enhancement of CUR (0.002 mg/ml) solubility with CUR α-CD complex (0.364 mg/ml) > CUR β-CD complex (0.186 mg/ml) > CUR γ-CD complex (0.068 mg/ml). Gibbs-free energy and in silico molecular docking studies favour formation of α-CD complex > β-CD complex > γ-CD complex. With reference to CUR, relative bioavailability of CUR α-CD, CUR β-CD and CUR γ-CD complexes were 460, 365 and 99 % respectively. CUR–CD complexes exhibited increased bioavailability with an increase in t_½, tmax, Cmax, AUC, Ka, and MRT; and a decrease in Ke, clearance and Vd values. AUC increase was CUR α-CD complex > CUR β-CD complex > CUR γ-CD complex. Significant difference (p < 0.05) was observed between CUR α-CD complex and CUR γ-CD complex by one-way ANOVA and Dunnett’s post hoc test for multiple comparison analysis. Correlation observed between in vitro, in vivo and in silico methods indicates potential of in silico and in vitro methods in CD selection.     

Electrochemical Fluorination of Benzamide and Acetanilide in Anhydrous HF and in Acetonitrile

Electrochemical fluorination of benzamide in anhydrous hydrogen fluoride does not involve the amide group but occurs exclusively at the aromatic ring, yielding isomeric fluoro- and difluorobenzamides and 3,3,6,6-tetrafluoro-1,4-cyclohexadienecarboxamide. Electrochemical fluorination of benzamide in acetonitrile as solvent gives the same products, as well as benzonitrile and its fluorinated derivatives and products of hydrolysis and fluorination of acetonitrile. Electrochemical fluorination of acetanilide in anhydrous HF leads to complete tarring of the reaction mixture, while its fluorination in acetonitrile results in selective formation of m-fluoroacetanilide.     

Structure of dimethoxyamine in the crystalline and gaseous phases and in solution

Conclusions It has been established by the methods of x-ray diffraction analysis and electron diffraction analysis and measurements of the dipole moments and the birefringence that in the crystalline and gaseous phases, as well as in solution, N,N-dimethoxyamine has a gauche-gauche conformation, which is stipulated by a stabilizing nO-N-O* orbital interaction. The geometric parameters of the molecule have been determined.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2235–2242, October, 1986.