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141.
《Electroanalysis》2006,18(10):971-975
The highly sensitive voltammetric detection of the 2,3‐dimethyl‐2,3‐dinitrobutane (DMNB), a required additive to commercial plastic explosives, is described. The protocol relies on a fast square‐wave voltammetric measurement of the DMNB explosive taggant at an unmodified carbon fiber electrode using a phosphate buffer (pH 7.0) solution. Different solutions and working electrodes were evaluated. Under the optimal conditions, a linear response is observed over the 300–3000 μg/L DMNB concentration range examined, with a detection limit of 60 μg/L. A highly stable response, with a relative standard deviation (RSD) of 2.6%, is observed for 30 repetitive measurements. Such electrochemical approach offers great promise for a simple, rapid, sensitive and inexpensive field screening of plastic explosives. Preliminary data illustrate the utility of electrochemical detection for electrophoretic microchips for the simultaneous measurements of DMNB, cyclotrimethylenetrinitramine (RDX) and pentaerythritoltetranitrate (PETN). 相似文献
142.
143.
New uniform algorithm to predict reversed phase retention values under different gradient conditions
Wang Longxing 《Analytica chimica acta》2003,476(1):123-129
A new numerical emulation algorithm was established to calculate retention parameters in RP-HPLC with several retention times under different linear or nonlinear binary gradient elution conditions and further predict the retention time under any other binary gradient conditions. A program was written according to this algorithm and nine solutes were used to test the program. The prediction results were excellent. The maximum relative error of predicted retention time was less than 0.45%. 相似文献
144.
定标粒子理论预测乙醇-水体系汽液平衡盐效应 总被引:6,自引:0,他引:6
测定了70℃下3个1-1型电解质(NaCl、NaBr、KCl)在各种不同浓度的乙醇-水体系中的汽液平衡盐效应参数,并给出用定标粒子理论计算盐效应参数的方法。硬球作用项采用Masterton-Lee方程,软球作用项采用胡英的径向分布函数。分子间力在Lennard-Jones位能函数基础上计入偶极-偶极、偶极-诱导偶极、电荷-偶极、电荷-诱导偶极的贡献,其中离子-分子间的静电作用项仅限于规则排列的第一配位圈之内。将混合溶剂的局部介电常数视为液相浓度的函数,函数关系由实验拟合。在乙醇浓度变化的很大范围内,3个体系的预测与实验结果基本相符。 相似文献
145.
以计量置换吸附理论(SDT A)为基础,从理论上推导出计量吸附模型中表征溶质对固定相亲合势大小的参数βa值与流动相中强置换剂浓度的对数呈线性关系。计量置换模型中的参数n和q(n和q分别代表1摩尔溶剂化溶质被吸附时,从吸附剂表面和从溶质分子表面所释放出的溶剂的物质的量)是计量置换参数Z值的分量,是两个非常有用的参数,可以从这个定量关系中直接获得。推导出的方程用苯的衍生物进行了实验验证,获得了较满意的结果。将这种方法计算得到的分量值与SDT A与计量置换保留模型(SDT R)相结合的方法得到的分量值进行了比较。 相似文献
146.
An attempt has been made to apply Green’s function and partitioning technique to the case of XY2Z (ClO2F) pyramidal type molecule belonging toC, point group. The isotopic rules have been formulated. The force constants, rotation distortion constants and mean amplitude
of vibration have been computed and compared with other observed and calculated values whichever is available. 相似文献
147.
Attila R. Imre W. Alexander Van Hook Bong Ho Chang Young Chan Bae 《Monatshefte für Chemie / Chemical Monthly》2003,134(12):1529-1539
Summary. Upper critical solution temperatures (UCSTs) for liquid–liquid demixing in a set of mixtures of linear alkanes (pentane (N
1=5) to pentacontane (N
1=50)) with an oligostyrene (1241amu, N
2=12) are reported. We find strong correlation between the Hildebrand solubility parameters of the alkanes and the UCST. Correlations are developed which enable predictions concerning the miscibility of mixtures of compounds with longer chains. 相似文献
148.
Xing-Zhi Liu Da-Wei Fang Jia-Zhen Yang Jun Li Shu-Liang Zang 《The Journal of chemical thermodynamics》2004,36(12):1061-1065
The equilibrium molalities In3+ in {In2(SO4)3 + Na2SO4 + HDEHMTPCA + n-C8H18 + water} were measured at ionic strength from (0.1 to 2.0) mol · kg−1 containing Na2SO4 as supporting electrolyte in aqueous phase and at constant molality extractant at temperatures from (278.15 to 303.15) K in organic phase. The standard extraction constants K0 at various temperatures were obtained by methods of extrapolation and polynomial approximation. Thermodynamic quantities for the extraction process were calculated. 相似文献
149.
Summary The behaviour of codeine reineckate and codeine tetraphenylborate membrane electrodes has been observed with a respectiveNernstian response of 58 and 56 mV/decade for 9.3×10–5–1.3×10–3
M codeine sulfate solutions. The workingpH ranges were 5–8 and 4–8, respectively. The selectivity towards sugars, amines, amino acids, cations, and some pharmaceutical compounds was found to be satisfactory. The isothermal temperature coefficient was 0.0014 V/°C. The electrodes were applied successfully for the determination of codeine in some pharmaceutical dosage forms with a relative standard deviation range of 0.16–0.30% and an average recovery of 98.6±0.6%.
Herstellung und Charakterisierung einer codeinselektiven Elektrode
Zusammenfassung Das Verhalten von Codeinreineckat- und Codeintetraphenylboratmembranelektroden in 9.3×10–5–1.3×10–3 M Codeinsulfatlösungen wurde untersucht (Nernstscher Response: 58 bzw. 56 mV/Dekade). Der verwendetepH-Bereich für die beiden Elektroden war 5–8 bzw. 4–8. Ihre Selektivität gegenüber Zuckern, Aminen, Aminosäuren, Kationen und einigen pharmazeutisch aktiven Verbindungen ist zufriedenstellend. Der isotherme Temperaturkoeffizient beträgt 0.0014V/°C. Die Elektroden wurden erfolgreich zur Bestimmung von Codein in einigen pharmazeutischen Präparaten eingesetzt (relative Standardabweichung: 0.16–0.30%).相似文献
150.
This paper is concerned with optimal control problems of Mayer and Bolza type for systems governed by a semilinear state equationx(t)=Ax(t) + f(t, x(t), u(t)), u(t) U, whereA is the infinitesimal generator of a strongly continuous semigroup in a Banach spaceX. We prove necessary and sufficient conditions for optimality and then use these conditions to investigate properties of the value function related to superdifferentials. Conversely, we use the value function to obtain criteria for optimality and feedback systems.Work (partially) supported by the Research Project Equazioni di evoluzione e applicazioni fisicomatematiche (M.U.R.S.T.-Italy). 相似文献