Study of Sediment Samples Using Instrumental Photon Activiation Multi-Elemental Analysis

Abstract

Instrumental Photon Activation Analysis (IPAA) has been used in many fields including environmental geochemistry. In the analysis of soil and sediment samples, the sensitivity of IPAA is comparable to that of standard methods such as atomic absorption spectroscopy. A major advantage of IPAA is that minimal sample processing is required and multi-element analyses can be obtained. In this work, the method of Internal Standard Coupled with Standard Addition Method (ISM-SAM) was applied to IPAA analysis of sediment samples. The equation used in ISM-SAM was derived in detail and the relationship between the elemental mass and the gamma peak counts in the measured spectra was established. It was found that accurate results can be obtained even when the sample and the reference are irradiated at different photon fluxes and measured in different geometries. The ISM-SAM equation was refined to better quantify the relationship between the addition amount and the uncertainty. Applying refined ISM-SAM, a sediment sample from Hudson River was analyzed. The concentrations of Ni, Pb, Zr, Ca, Fe, Mg, Na, Ti, As, Cr, Ce, Co, Rb, and Zn were determined and compared with the results obtained from Atomic Absorption analysis of total acid digests. For elements analyzed by both methods, excellent agreement was found. Meanwhile, the detection limits of photon activation analysis for selected elements were obtained based on the present experimental conditions.     

Development and validation of LC methods with visible detection using pre-column derivatization and mass detection for the assay of voglibose

Two sensitive and selective liquid chromatographic methods were developed for the assay of voglibose (VB) and validated as per International Conference on Harmonization (ICH) guidelines. First method is based on the pre-column derivatization of VB followed by visible detection (LC-VD) and second method involves mass spectrometric detection (LC-MS). In LC-VD method, VB was derivatized with sodium metaperiodate and 3-methyl-2-benzothiazolinone hydrazone hydrochloride monohydrate (MBTH). The derivatized color product of VB (DCPVB) was run through Novapak C18 (300 × 3.9 mm, 4 μm) column using the mobile phase containing buffer (0.01 M mixture of sodium di hydrogen orthophosphate and disodium hydrogen orthophosphate, pH 6.0) and acetonitrile in 35:65 v/v ratio. The eluted DCPVB was monitored at 667 nm. The fixation of optimum conditions in LC-VD method is described. DCPVB structure was confirmed by mass spectral analysis. In LC-MS method, VB was passed through Venusil XBPPH (150 × 4.6 mm, 5 μm) column using a 95:5 v/v mixture of 0.01% formic acid and methanol as mobile phase. The assay concentrations of VB in pure form and in tablets for LC-VD and LC-MS methods are 25 and 5 ng ml⁻¹, respectively.     

基于有限元网格重合法的宏观-细观多尺度细粒化研究

主要针对有限元网格重合法的基本原理进行分析、推导了整体到局部区域里的有限元重合网格法的数学模型,以戴圆孔板的应力集中问题为例进行探讨了有限元重合网格法的计算精度和应用价值并与一般的有限元法进行了对比分析.结果表明,有限元重合网格法对工程中的多尺度分析问题有一定的应用价值.     

Numerical exploration of a system of reaction–diffusion equations with internal and transient layers

A reaction pathway for a classical two-species reaction is considered with one reaction that is several orders of magnitudes faster than the other. To sustain the fast reaction, the transport and reaction effects must balance in such a way as to give an internal layer in space. For the steady-state problem, existing singular perturbation analysis rigorously proves the correct scaling of the internal layer. This work reports the results of exploratory numerical simulations that are designed to provide guidance for the analysis to be performed for the transient problem. The full model is comprised of a system of time-dependent reaction–diffusion equations coupled through the non-linear reaction terms with mixed Dirichlet and Neumann boundary conditions. In addition to internal layers in space, the time-dependent problem possesses an initial transient layer in time. To resolve both types of layers as accurately as possible, we design a finite element method with analytic evaluation of all integrals. This avoids all errors associated with the evaluation of the non-linearities and allows us to provide an analytic Jacobian matrix to the implicit time stepping method. The numerical results show that the method resolves the localized sharp gradients accurately and can predict the scaling of the internal layers for the time-dependent problem.     

份额——偏离分析法在河北省工业产业定位分析中的应用

对河北省工业产业进行定位分析,首先对份额——偏离分析法及区位商分析法做了简单的介绍;然后利用S-S分析法和区位商分析法对河北省工业产业的相对优势进行了分析,同时分析了河北省工业在区域内的绝对优势;最后结合以上两方面分析结论对河北省工业产业进行了定位分析.     

应用迭代法求解一类非线性问题

本文应用迭代法求解一类有限维非线性问题,该方法是求解线性问题的雅可比迭代法在非线性问题上的推广,且此迭代方法具有几何收敛性质.     

关于次线性椭圆方程正解的对称性

本文利用次线性项在零点附近的凹性和可积发表和移动平面法给出一类次线性椭圆方程正解的对称性。     

A note on the prediction method of reverberation absorption coefficient of double layer micro-perforated membrane

The absorption performance of micro-perforated absorber (MPA) has been usually estimated by equivalent circuit (EC), however, it has been noted that the predicted absorption coefficient by EC does not agree completely with the experiment in some frequency range. Hence impedance transfer method (ITM) is adopted to predict the reverberation absorption coefficient of a double layer micro-perforated membrane (MPM) structure. Experimental studies show that the prediction of ITM is better than that of EC.     

海洋沉积物中汞的分析方法研究

本文介绍了冷原子荧光法测定海洋沉积物中汞的分析方法。试样用王水(1 1)在沸水浴上分解，氯化亚锡还原，冷原子荧光法测定。本法大大降低了共存元素对汞的测定干扰，不需加高锰酸钾及草酸，使操作更加简单、快速，方法精密度好、准确度高。经对海洋沉积物国家一级标准物质GBW 07314、GBW 07315、GBW 07316进行测定，其结果准确可靠。并对GBW 07315进行了12次测定，相对标准偏差为2．21％。不同实验室用本法测定海底沉积物样品中Hg，均获得了满意的结果。