高纯度塔拉单宁酸含量测定方法的研究

研究了用紫外分光光度法和高效液相色谱测定高纯度塔拉单宁酸含量的方法,提出了测定实验条件.统计检验结果表明,2种方法的测定数据组均无异常值并遵从正态分布,同时进行了2种方法测值的方差检验和均数检验,结果表明二者的测量精密度无显著性差异,但2组测值的平均值却存在显著性差异.     

3,4,5-三甲氧基苯甲酸含量测定方法的研究

比较了采用高效液相色谱法和化学滴定法2种方法测定3,4,5-三甲氧基苯甲酸的含量,提出了测定操作的实验条件,并对测定结果进行统计分析,以判断和评价2种方法的准确性和实用性。经过Grubbs检验表明2种方法的测定数据均无异常值;通过偏态系数和峰态系数来检验方法的正态性分布,统计结果表明2种方法均遵从正态分布;同时进行了2种方法测定值的均数检验（t检验）,结果表明二者的测定值无显著性差异。高效液相色谱法的测定值有更高的准确度和精密度,可以作为首选,在不具备色谱仪的情况下也可使用化学滴定法。     

关于COD_(Mn)两种方法的相关性研究

长江入海口受咸淡水影响,盐度变化较大。分别通过高锰酸盐指数法和碱式高锰酸钾法对长江口不同盐度水样的CODMn进行测定,并对两种方法进行比对校正。结果表明,两组数据具有明显的正相关关系;经实际数据检验以及测量值和拟合值之间的统计检验分析得出:两组数据之间没有显著差异,两种方法显著相关。为长江口水体CODMn的监测提供了数据支撑,以解决海上和陆地COD监测之间的数据衔接问题。     

HPLC法测定没食子酸甲酯含量的研究

采用HPLC方法进行没食子酸甲酯(MG)含量测定实验,UV特征吸收波长为279 nm。试验结果表明,色谱峰面积与试样溶液浓度的关系遵从比耳定律。运用统计学方法对测定值进行了分析研究,测量值数据的分布具有正态性;测量值的标准偏差S＝0.02%,符合B级精密度水平;两个实验室的测量值数据通过了F检验和t检验,无明显差异。由此表明,测量方法具有高精密度和准确度。该方法具有操作较为简便快捷、分析成本低廉、测定值稳定等特点。     

两种分光光度法测定样品中铁含量的比较——以化学实验技术技能大赛为例

依据2021年化学实验技术赛项规程及检测标准,建立了1,10-菲啰啉分光光度法与磺基水杨酸分光光度法测定样品中铁含量的方法,分别采用两种分光光度法测定样品中铁含量。结果发现,两种方法的标准曲线相关系数R可达0.999995以上,检测方法可行;两种方法测定待测液吸光度值的|极差不大于|不大于0.5%,精密度与准确度均达到化学实验技术赛项结果性考核要求,检测结果有效;经F检验、t检验,两种方法的方差与平均值无显著性差异,检测结果是一致的。     

焦炉煤气中H2S测定方法的比较

介绍了我国焦炉煤气中H2S的几种主要测定方法,对3种方法进行了精度和方差等方面的比较,发现中小型焦化厂检验方法偏差较大,而国标方法(GB12211-90)和宝钢分析方法测定煤气中的H2S在精度和测定值上无显著差异。     

便携式溶解氧仪与碘量法测定溶解氧的置信度与精密度比较

对同一水样中溶解氧采用便携式溶解氧仪和碘量法进行比对实验,根据两种方法的测定结果进行DIXON检验和精密度检验,设定置信度为95%,对比结果显示,两方法测定结果之间无显著性差异,精密度符合水质监测质控要求.     

植株中铜锌铁锰微量元素的测定方法研究

用湿消化法和浸提法（HCl Vc）分别对7种植株样品进行前处理，用火焰原子吸收光谱法测定其铜、锌、铁、锰的含量。通过对测定结果的分析统计检验，这两种前处理方法之间无显著性差异，浸提法完全可以替代湿消化法。     

土壤中砷测定时不同消解方式的比对分析

原子荧光光谱法测定土壤中砷含量时,常用的消解方式有水浴消解和微波消解。对土壤成分标准物质(GSS-24)分别使用水浴消解和微波消解进行了6次平行消解测定,并选用经典的Grubbs检验法进行了异常值的检验,利用SPSS软件对两组消解数据进行了显著性差异比对。结果表明,水浴消解和微波消解的测定结果无显著性差异。基于此,给出了不同消解方式的优缺点及选择建议。     

撞击法测定空气中落菌数的不确定度评估

文章使用细菌总数的对数值进行统计处理的方法评估了《公共场所空气微生物检验方法——细菌总数测定》的不确定度,从而确定了该测量方法的置信度和准确性,使测量结果更具科学性和可比性。     

Determination of Donor Gradients Within Surface Barriers Formed on Dense Cd-Doped Barium Titanates

Surface barriers were formed on dense Gd-doped barium titanates by a reduction-reoxidation process. The distribution of donors within the partially reoxidized barriers was determined from capacitance measurements using blocking contacts and from resistance measurements using ohmic contacts. The incremental barrier capacitance behaved as a depletion-layer capacitance when measured as a function of bias voltage. A donor gradient α_c was determined from the capacitance-voltage behavior of the depletion layers by using a linear-graded model to describe the donor distribution through the depletion layers. A donor gradient a_r was indirectly determined from resistance profiles of the surface barriers formed on the reduced titanates by a second reoxidation. The donor gradients a_c and a_r were in good agreement, with both gradients decreasing for the higher reoxidation temperatures and/or the longer times used in forming the barriers. This behavior is explained by assuming that the reoxidation process is diffusion-controlled and by qualitatively relating the gradients to assumed oxygen profiles within the barriers.     

Stability of Monoclinic and Orthorhombic Zirconia: Studies by High-Pressure Phase Equilibria and Calorimetry

The stability fields of two high-pressure polymorphs of ZrO₂ (ortho I and ortho II) were determined by both calorimetry and phase equilibrium experiments. Enthalpies of transition were measured by transposed temperature drop calorimetry. The entropies of transition and slopes of phase boundaries were calculated using the measured enthalpies and free energies calculated from the results of phase equilibrium experiments. From the thermodynamic measurements, it is seen that the entropy increases and the volume decreases during the monoclinic–ortho I transition, whereas both the entropy and the volume decrease during the ortho I–ortho II transition. Accordingly, the gradient of phase boundaries, dP/dT , is negative in the former and positive in the latter. These trends are consistent with those of phase equilibrium experiments.     

Determination of Dissipation Rate in Stirred Vessels Through Direct Measurement of Fluctuating Velocity Gradients

2‐D and 3‐D PIV and 4‐channel LDA techniques were employed to measure the turbulence energy dissipation rate in vessels stirred by Rushton impellers. The measurements were made in vessels of diameter T = 100 mm and 294 mm and stirred by impellers of diameter D = T/3. The impellers were rotated at speeds corresponding to Reynolds number of 40,000 to ensure fully‐turbulent flow in the vessels. ? was determined directly from measurements of the Reynolds stress gradients by analyzing the PIV images over interrogation areas down to 0.1 mm. Similar LDA data were obtained in the larger 294 mm vessel, with a resolution of around 50 μm. The fluctuating gradient results obtained with the two techniques compare well and show that direct measurement of the ? distribution is feasible with both PIV and LDA methods.     

Adhesion: Comparison Between Physico-chemical Expected and Measured Adhesion of Oxygen-plasma-treated Carbon Fibers and Polycarbonate

The adhesive interaction between oxygen-plasma-treated, polyacrylonitrile-based, high-tensile-strength carbon fibers and a polycarbonate matrix has been studied. Several models have been used to predict the impact of the plasma treatment process on the strength of adhesion between both jointing partners. These approaches have been the thermodynamic work of adhesion which was calculated from the solid surface tensions, based on the results of contact angle measurements versus test liquids, the contact angle which was directly obtained via polycarbonate melt droplets on single carbon fibers and the zeta (ς)-potential data provided by streaming potential measurements. The results have been compared with the interfacial shear strength determined from the single-fiber fragmentation test. Additionally, the single-fiber tensile strength of the oxygen-plasma-treated carbon fibers was determined.

We confirmed that any physico-chemical method on its own fails to describe exactly the measured adhesion. However, for the investigated system, the conscientious interpretation of the data obtained from wetting measurements, in conjunction with the thermodynamic approach, is sufficient to predict the success of a modification technique which has been applied to one component in order to improve adhesion.     

On the pH dependence of electroactivity of poly(methylene blue) films

The electrochemical behavior of poly(methylene blue) on different electrodes has been investigated by electrochemical quartz crystal microbalance and in situ spectrophotometric measurements coupled to cyclic voltammetry. Polymeric films were obtained potentiodynamically and the charge transport mechanism was analyzed. The electrochemical results show that polymer electroactivity depends not only on pH but also on the substrate. Charge compensation changes with both pH and the size of the anions showing a transition in the pH range of polymer pKa. It was demonstrated by spectroelectrochemical experiments that the electroactivity of the film depends on the radical/radical cation equilibrium. The potentials where the most electroactive species are formed have been determined.     

The influence of fluoride ions on the passive dissolution of titanium

Steady state, potential step and impedance measurements were used to investigate the influence of fluoride ions on the passive dissolution of Ti in 4.5 M H₂SO₄ solution. The results indicated that metal dissolution occurs via a surface film, the presence of which was confirmed by a SEM study. Electron diffraction and SIMS measurements have shown this film to be polycrystalline TiO₂. A mechanism involving simultaneous formation and dissolution of surface oxide is suggested to explain the results. The ionic current through the film is field-dependent. The dissolution rate of the oxide is determined mainly by the fluoride concentration of the solution.     

Interpretation of mass transfer measurements in bubble columns considering dispersion of both phases

Mass transfer measurements in two bubble columns with an inner diameter of 100 resp. 140 mm with the systems air/water/carbon dioxide and nitrogen/n-propanol/carbon dioxide have been evaluated with the axial dispersion model. The dispersion coefficients of both phases have been determined in separate investigations. As the results revealed a strong influence of the liquid viscosity, additional dispersion coefficient measurements have been carried out with the system air/glycol. It could be shown that the liquid phase dispersion coefficient decreases with increasing viscosity while the gas phase dispersion coefficient increases with increasing liquid viscosity. Both coefficients are strongly dependent on the gas throughput and the column diameter. Using these coefficients, the mass transfer coefficients have been calculated by fitting the calculated concentration profile to the measured values and by splitting the volumetric mass transfer coefficient with the experimental value of the interfacial are a. The results agree best with a correlation of Calderbank and Moo-Young.     

圆柱定程干涉法确定工质的第二维里系数

通过圆柱定程干涉法测量了Ar在270~333.15 K,压力至1000 kPa的声学共振频率,修正了热边界层、黏性边界层、声波导管、壳体振动等非理想因素对共振频率测量的影响。通过拟合声学共振频率获得了Ar的第二声速维里系数,实验结果与文献中圆球定程干涉法的测量结果具有较好的一致性。通过第二声速维里系数回归了方阱势能模型的参数,根据回归结果计算了Ar的第二维里系数,在150~450 K范围与标准状态方程的计算偏差小于0.4 cm³·mol^-1。通过圆柱定程干涉法确定的第二维里系数与圆球定程干涉法的精度相当。     

Si MAS-NMR Study of Hydrated Cement Paste and Mortar Made with and without Silica Fume

This paper presents ²⁹Si MAS-NMR measurements that trace the hydration process in both cement paste and mortar specimens made from ordinary portland cement, Type I, when the cement content is replaced by 0, 10, 15, and 20 wt% of silica fume. The specimens were moist-cured for 3, 7, 14, 28, 90, and 180 days at a laboratory temperature of 21°C (69.8°F). Compressive strength for all tested specimens was also determined. The results show that the degree of hydration (Q¹+ Q²)/(Q°+ Q¹+ Q²) increased with increasing content of silica fume, especially at the early ages of 3 to 28 days. In the same manner, compressive strength results were markedly increased up to 14 days and were lowered at later ages, compared to the control mix (0 wt% silica fume).