盐酸和氯化钙混合溶液中滴加碳酸钠溶液pH变化的实验探究*

盐酸、氯化钙混合溶液中滴加碳酸钠溶液,当碳酸钙沉淀出现后,混合溶液pH是否基本不变？此时的pH是否为7？为此用数字化实验对盐酸、氯化钙混合溶液中滴加碳酸钠溶液pH的变化进行了探讨,对平台段的出现及平台段溶液pH进行了实验探究和理论分析。     

硫酸亚铁及氯化铁与硫酸亚铁混合溶液与氢氧化钠溶液反应的沉淀pH曲线的测定及分析

应用手持技术pH传感器,测定了NaOH溶液滴定FeSO4溶液的t-pH曲线,应用origin 9.0分析实验数据,探讨了空气对Fe2+沉淀pH的影响;通过测定并分析FeSO4溶液滴定NaOH溶液的pH曲线,发现了溶液最终pH受金属离子水解程度的影响;通过测定并分析NaOH溶液滴定FeCl3和FeSO4混合溶液的pH曲线,探讨了Fe2+和Fe3+的互相影响,使其沉淀pH范围发生变化;通过测定并分析FeCl3和FeSO4混合溶液滴定NaOH溶液的pH曲线,验证了Fe2+和Fe3+的水解程度不同,Fe （OH）3和Fe （OH）2的存在条件也不一样。     

电感耦合等离子体质谱测定高纯金属钐中25种杂质元素

研究建立了电感耦合等离子体质谱(ICP—MS)测定高纯金属钐中14种稀土及11种非稀土杂质的测定方法。考察了钐基体对杂质元素测定的各种干扰影响。对无干扰的杂质元素,采取了直接测量的方式;对有干扰的元素(Nd、Eu、Dy、Ho、Er、Tm),采用标准加入法的方式进行测定。选择内标元素Sc和Cs,有效补偿了由于基体效应带来的测量偏差。方法的检出限为0．012～83μg／L．加标回收率为88．6％～108．0％．测定精密度(RSD)为0．55％～2．53％,方法可满足99．9％纯度的金属钐中朵质元素的分析测定。     

超高效液相色谱-高分辨质谱法测定蜂蜜中的苯甲酸、山梨酸、安赛蜜与糖精钠

建立了蜂蜜中苯甲酸、山梨酸、安赛蜜、糖精钠的超高效液相色谱-高分辨质谱分离测定方法。样品采用甲醇-水溶液(10∶90)提取,Diamonsil Plus C18色谱柱进行色谱分离,以0.5 mmol/L乙酸铵溶液和甲醇为流动相梯度洗脱,通过高分辨负离子扫描模式进行定性,外标法定量。结果表明,4种物质在0.02~2.0mg/L范围内均具有良好的线性关系,相关系数为0.998 7~0.999 7。苯甲酸、山梨酸的方法定量下限为0.5mg/kg,安赛蜜、糖精钠为0.3 mg/kg。在低、中、高3个加标浓度下,方法的回收率为89.0%~104.0%,相对标准偏差(RSD)为2.0%~7.9%。该方法灵敏、简单、快速,定性准确可靠,适用于大批量蜂蜜中苯甲酸、山梨酸、安赛蜜、糖精钠的检测。     

高纯金属镱中杂质元素的电感耦合等离子体质谱法测定

利用电感耦合等离子体质谱仪(ICP—MS)直接测定了金属镱中除Tm、Lu外其他稀土及非稀土杂质元素;通过P507萃淋树脂色层柱,分离绝大部分Yb基体,避免了基体元素对Tm、Lu的测定干扰?定量加入内标元素Sc、Cs,有效克服了基体效应所带来的偏差。稀土杂质元素的检出限0．010～0．032μg／g,非稀土杂质元素的检出限为0.12～5．0μg／g。加标回收率为83％～105％。方法适用于纯度为99．99％～99．999％的高纯金属镱产品中杂质元素的测定。     

冷冻升华制备的超高分子量聚乙烯寡链、多链晶体的凝聚态

在10^-3～10^-5g/mL浓度范围内,用冷冻升华法制备了超高分子量聚乙烯(UHPE)单链、寡链、多链的折叠链晶聚集体.长达几万纳米的UHPE分子链可以以不同的片晶参与结晶,或自身形成数个晶粒,即形成单链多晶.DSC研究结果表明,随着溶液浓度的降低,冷冻升华样品的熔点和结晶度均降低.由熔点估算了晶粒的体积和晶粒中包含的链数,它们亦随溶液浓度降低而降低.冷冻升华得到的小晶粒中链的缠结少,晶体具有较高的完善性.用WAXD测试晶粒的(110)和(200)面的法向尺寸,由此计算晶粒的平均体积,与熔点计算得到的数值一致.     

电感耦合等离子体质谱法测定高纯镓中痕量杂质

采用电感耦合等离子体质谱（ICP-MS）测定高纯镓中痕量杂质元素,以Rh作为内标补偿校正镓基体的抑制效应,采用异丙醚萃取分离镓与ICP-MS技术联用,拓展分析方法应用范围,可满足99.9999%-99.99999%超高纯镓分析方法要求。方法检出限为0.006-0.062μg/L;加标回收率为86.8%-121.4%之间;RSD为1.1%-8.6%。     

Chloride Binding Modulated by Anion Receptors Bearing Tetrazine and Urea

Modulation and fine-tuning of the strength of weak interactions to bind anions are described in a series of synthetic receptors. The general design of the receptors includes both a urea motif and a tetrazine motif. The synthetic sequence towards three receptors is detailed. Impacts of H-bond strength and linker length between urea and tetrazine on chloride complexation are studied. Binding properties of the chloride anion are examined in both the ground and excited states using a panel of analytical methods (NMR spectroscopy, mass spectrometry, UV/Visible spectroscopies, and fluorescence). A ranking of the receptors by complexation strength has been determined, allowing a better understanding of the structure-properties relationship on these compounds.     

氯化钠增敏光度法测定微量碘

1　引　　言碘是人体必需元素 ,对大脑的发育起着决定性的作用。碘的测定方法很多 ,我们在对经典的碘 淀粉显色反应研究时 ,观察到ＮａＣｌ能显著地提高显色灵敏度 ,并使可见光区的最大吸收波长明显蓝移的现象。在高浓度氯化钠溶液中 ,碘 淀粉溶液的最大吸收波长λｍａｘ=4 83ｎｍ ,较无ＮａＣｌ时蓝移 72ｎｍ ,最大摩尔吸光系数εｍａｘ=2 .7× 10 5Ｌ·ｍｏｌ- 1 ·ｃｍ- 1 ,灵敏度提高 5倍。碘含量在 0～ 1.6ｍｇ Ｌ内符合比耳定律 ;检出限为 0 .0 12ｍｇ Ｌ ;ＲＳＤ为 0 .3%。拟定了在高浓度ＮａＣｌ体系中测定碘的新方法 ,该法用于食…     

电感耦合等离子体质谱法测定高纯金属铋中痕量杂质元素

采用电感耦合等离子体质谱法测定了高纯金属铋中14种痕量杂质元素。考察了基体效应对测定元素的干扰影响,通过铋基体元素的分离和以Sc、In、Eu作为内标,有效克服了干扰现象。方法的检出限在0．1～4．7ng/mL;精密度在1．4％～5．0％;加标回收率在89％～114％范围。本法可满足99．999％以上金属铋中痕量杂质测定的要求。     

Non‐Stoichiometric Polycondensations and the Synthesis of High Molar Mass Polycondensates

This report presents a general overview of non‐stoichiometric step‐growth polymerizations (polycondensations). Three kinds of non‐stoichiometric polycondensations are defined and discussed for a₂ + b₂ monomer combinations. Depending on the kinetic scenario and on the experimental conditions, the excess of one monomer either strongly reduces or strongly enhances the average degree of polymerization (DP) relative to a stoichiometric polycondensation under identical conditions. As a result, telechelic oligomers or extremely high molar mass polymers (DPs > 1000) may be formed. Stoichiometric imbalance has in all cases the consequence that cyclization is largely suppressed in early stages of a polycondensation. Finally, non‐ stoichiometric “ a₂ + b_n ” polycondensations are discussed.     

Quantification of Trace Amounts of Impurities in High Purity Cobalt by High Resolution Inductively Coupled Plasma Mass Spectrometry

Cobalt metal has been used in the production of magnetic alloys, cobalt and nickel based superalloys and sputtering targets in the field of advanced electronic devices1. The determination of trace impurities in high purity cobalt is extremely important be…     

电感耦合等离子体质谱测定高纯仲钨酸铵中磷及其它微量元素

本研究采用带碰撞反应池的电感耦合等离子体质谱(ICP-ORS-MS)建立了快速、直接测定高纯仲钨酸铵样品中的磷及其它20种痕量元素杂质的方法.分别采用2种不同的样品制备方法,结果表明,使用4%H2O2进行消解操作简单、基体干扰小.通过高基体进样系统与电感耦合等离子体质谱联用,每个样品的固体总溶解度达到1%,连续测定样品2 h,结果表明,能够克服高钨基体对ICP-MS信号稳定性的影响.方法检出限可达到ng/g, 甚至亚μg/g,完全满足实际样品的分析,可实现仲钨酸铵生产现场的实时质量监测.     

高纯金属的快速分析-强激光溅射电离飞行时间质谱法

随着现代材料行业的发展,高纯金属纯度分析日趋重要。本研究建立了一种基于强激光溅射电离飞行时间质谱（LAI-TOFMS）检测高纯金属纯度新方法。为消除高价离子和多原子离子等干扰峰的影响,在离子源内引入了氦气。通过分析高纯阴极铜的系列标准样品,建立了其中16种痕量元素的固体直接定量分析方法,在4个动态范围内（10-7 – 10-3 μg/g）的线性相关度优于0.97,检出限低至0.1 μg/g。该方法几乎无需样品处理、分析时间短、操作简便、灵敏度高、谱峰干扰小,可用于高纯金属材料纯度及其痕量杂质的快速分析。     

自动电位滴定法测定工业碳酸钠中氯化钠含量

采用自动电位滴定法,用硝酸银标准溶液作为滴定剂,测定工业碳酸钠中氯化钠含量。方法检出限为0.13mg/L,不同含量氯化钠样品加标回收率为99.7%~100.3%,相对标准偏差(n=5)为0.17%~2.0%,方法简单、快速,精密度和准确度高,适合大批量快速分析样品。     

Barium and Radium Complexation with Ethylenediaminetetraacetic Acid in Aqueous Alkaline Sodium Chloride Media

The speciation of Ra²⁺ and Ba²⁺ with EDTA was investigated at 25 °C in aqueous alkaline NaCl media as a function of ionic strength (0.2–2.5 mol·L^?1) in two pH regions where the EDTA^4? and HEDTA^3? species dominate. The stability constants for the formation of the [BaEDTA]^2? and [RaEDTA]^2? complexes were determined using an ion exchange method. Barium-133 and radium-226 were used as radiotracers and their concentrations in the aqueous phase were measured using liquid scintillation counting and gamma spectrometry, respectively. The specific ion interaction theory (SIT) was used to account for [NaEDTA]^3? and [NaHEDTA]^2? complex formation, and used to extrapolate the logarithms of the apparent stability constants (log₁₀ K) to zero ionic strength (BaEDTA^2?: 9.86 ± 0.09; RaEDTA^2?: 9.13 ± 0.07) and obtain the Ba²⁺ and Ra²⁺ ion interaction parameters: [ε(Na⁺, BaEDTA^2?) = ? (0.03 ± 0.11); ε(Na⁺, RaEDTA^2?) = ? (0.10 ± 0.11)]. It was found that in the pH region where HEDTA^3? dominates, the reaction of Ba²⁺ or Ra²⁺ with the HEDTA^3? ligand also results in the formation of the BaEDTA^2? and RaEDTA^2? complexes (as it does in the region where the EDTA^4? ligand dominates) with the release of a proton. Comparison of the ion interaction parameters of Ba²⁺ and Ra²⁺ strongly indicates that both metal ions and their EDTA complexes have similar activity coefficients and undergo similar short-range interactions in aqueous NaCl media.     

高效液相色谱-串联质谱法测定调味料中的痕量苯甲酸与山梨酸

建立了调味料中痕量苯甲酸、山梨酸的高效液相色谱-串联质谱检测方法.调味料样品经盐酸酸化后用乙醚多次提取,酸性氯化钠洗涤提取液,挥干后用1 mL90% 0.2 mmol/L NH4OAc(pH 5.0)的乙腈溶液溶解,过膜备用.采用电喷雾负离子电离(ESI-)模式和单反应监控(SRM)模式检测,外标法定量.该方法在0.5...     

Limiting Partial Molar Volume of Sodium Chloride in 2-Methyl-2,4-pentandiol-Water Mixed Solvents at 25 °C

Herein we report density measurements for the binary system 2-methyl-2,4-pentanediol(MPD,1)-water(0), and for the ternary system MPD(1)-NaCl(2)-water(0), at several fixed MPD/water ratios and at varying NaCl concentrations. The partial molar volume of MPD in the binary system has been discussed according to the McMillan-Meyer theory. At low MPD concentrations, the non-bonding MPD-MPD interactions are related to the overlapping of the hydrophobic parts of the hydration cospheres, whereas at higher concentrations the hydrophilic moieties are also involved in the solute-solute interactions. The ternary density data allowed us to determine the salt partial molar volume at infinite dilution. The trend of this quantity as a function of the MPD content in the MPD-water “mixed solvent” has been interpreted on the basis of the water partial molar volume in the binary MPD-water system.     

应用手持技术测定氯化铁溶液与氢氧化钠溶液反应的pH曲线

应用手持技术pH传感器,探讨NaOH溶液滴定FeCl3溶液的t-pH曲线,考察了实验的最佳条件,测定了最佳浓度下FeCl3溶液与NaOH溶液互相滴定的pH变化曲线。应用origin 9.0分析实验数据,结合理论值与宏观现象分析确定了Fe3+初始沉淀的pH及沉淀完全的pH,并通过四重表征详细分析了pH曲线及实验现象。同时在实验过程中发现了制备氢氧化铁胶体的新方法。