Application of differential pulse stripping voltammetry and chemometrics for the determination of three antibiotic drugs in food samples

A reliable method for simultaneous determination of three antibiotic drugs(levofloxacin,gatifloxacin and lomefloxacin) by differential pulse stripping voltammetry(DPSV) in Britton-Robinson buffer(pH 7.96) was presented.The method is based on adsorptive accumulation of the antibacterial drugs on a hanging mercury dropping electrode(HMDE),followed by the reduction of the adsorptive species by the technique of DPSV.Optimal conditions,the deposition time of 80 s,the deposition potential of—1250 mV,and the scan rate of 25 mV/s,were obtained.The linear concentration ranges of 0.010-0.080μg/mL were obtained for all these three antibiotic drugs,while the detection limits were 2.38,3.20 and 1.60ng/mL for levofloxacin,gatifloxacin and lomefloxacin,respectively.In this work,chemometrics methods,such as classical least squares(CLS),partial least squares(PLS), principle component regression(PCR) and radial basis function-artificial neural networks(RBF-ANN),were used to quantitatively resolve the overlapping signals.It was found that PCR gave the best results with total relative prediction error(RPE_T) of 7.71%.The proposed method was applied to determine these three drugs in several commercial food samples with spiked method and yielded satisfactory recoveries.     

Stannum film electrode for square wave voltammetric determination of trace copper(II)

An anodic stripping voltammetric procedure for the determination of Cu(II) at an in situ-plated stannum film electrode (SnFE) was described. The results indicated that the SnFE had an attractive electroanalytical performance, with two distinct voltammetric stripping signals for copper and stannum, and showed the superior advantage for the determination of copper compared with the bismuth film electrode. Several experimental parameters were optimized. The SnFE exhibited highly linear behavior in the concentration range from 1.0 to 100.0 μg L⁻¹ of Cu(II) (r = 0.994) with the detection limit of 0.61 μg L⁻¹ (S/N = 3), and the relative standard deviation for a solution containing 40.0 μg L⁻¹ Cu(II) was 2.2% (n = 8). The procedure has been successfully applied for the determination of Cu(II) in lake water sample.     

A label-free thrombin binding aptamer as a probe for highly sensitive and selective detection of lead(II) ions by a resonance Rayleigh scattering method

The binding of lead(II) ions with unusually high affinity to a thrombin binding aptamer resulted in an enhancement of resonance Rayleigh scattering (RRS). A simple, sensitive, and selective assay for the direct determination of trace amounts of Pb(2+) on the basis of RRS has been proposed.     

Depth and orientational dependencies of MRI T(2) and T(1ρ) sensitivities towards trypsin degradation and Gd-DTPA(2-) presence in articular cartilage at microscopic resolution

Depth and orientational dependencies of microscopic magnetic resonance imaging (MRI) T(2) and T(1ρ) sensitivities were studied in native and trypsin-degraded articular cartilage before and after being soaked in 1 mM Gd-DTPA(2-) solution. When the cartilage surface was perpendicular to B(0), a typical laminar appearance was visible in T(2)-weighted images but not in T(1ρ)-weighted images, especially when the spin-lock field was high (2 kHz). At the magic angle (55°) orientation, neither T(2)- nor T(1ρ)-weighted image had a laminar appearance. Trypsin degradation caused a depth- and orientational-dependent T(2) increase (4%-64%) and a more uniform T(1ρ) increase at a sufficiently high spin-lock field (55%-81%). The presence of the Gd ions caused both T(2) and T(1ρ) to decrease significantly in the degraded tissue (6%-38% and 44%-49%, respectively) but less notably in the native tissue (5%-10% and 16%-28%, respectively). A quantity Sensitivity was introduced that combined both the percentage change and the absolute change in the relaxation analysis. An MRI experimental protocol based on two T(1ρ) measurements (without and with the presence of the Gd ions) was proposed to be a new imaging marker for cartilage degradation.     

2维全自动亥姆霍兹线圈磁块测量方法

在波荡器和扭摆器的研制过程中,为提高磁块的测量效率和精度,提出了2维全自动亥姆霍兹线圈磁块测量方法。通过理论推导得到仅采用2维全自动旋转而不需要3维旋转就可以实现磁块的全自动测量,降低了磁块全自动测量的实现难度。根据该方法的理论,已成功研制出一台2维全自动亥姆霍兹线圈测量装备,并在上海光源的磁块测量中使用。系统地给出2维全自动亥姆霍兹线圈磁块的测量理论和方法,并对测量误差进行了分析,该系统实现了磁块剩磁测量的高效率、高精度和高重复性,可以在30 s内完成单磁块的测量,重复性和精度均好于510-4。     

Negative refraction with low absorption using EIT in a four-level left-handed atomic system

We suggest a scheme for obtaining negative refraction with low absorption in a left-handed atomic system. Under the appropriate conditions, the atomic system displays negative refraction with negative permittivity and permeability (left-handedness) in a common frequency range, simultaneously. And the imaginary parts of permittivity and permeability show transparently propagate in the same frequency range. Finally, the negative refraction show low absorption due to the EIT effect, and the figure of merit demonstrated this in this resonant atomic system.     

一种结合几何相容性分析的谱匹配算法

为了可靠地实现点模式匹配,提出了一种基于谱图理论与几何相容性分析的点模式匹配算法。利用拉普拉斯矩阵的特征向量获得待匹配点集间谱匹配代价的表示;结合以邻近关系表示的几何相容性,定义了一种混合形式的匹配目标函数;给出了基于松弛迭代的求解算法。仿真数据和真实图像上的比较实验表明所给出的方法具有较好的精度与时间性能。     

Design of a dual-output fluorescent DNA logic gate and detection of silver ions and cysteine based on graphene oxide

In the presence of graphene oxide, upon formation of cytosine-Ag-cytosine the fluorescence wavelength of FAM-labeled DNA exhibited a red shift, and its intensity significantly increased. A novel fluorescent DNA sensor for Ag(+) and cysteine detection, and a dual-output fluorescent DNA INHIBIT logic gate are designed.     

A glassy carbon electrode modified with antimony and poly(p-aminobenzene sulfonic acid) for sensing lead(II) by square wave anodic stripping voltammetry

We have developed a sensor for the square wave anodic stripping voltammetric determination of Pb(II). A glassy carbon electrode was modified with a thin film of an antimony/poly(p-aminobenzene sulfonic acid) composite in air-saturated aqueous solution of pH 2.0. Compared to a conventional antimony film electrode, the new one yields a larger stripping signal for Pb(II). The conditions of polymerization, the concentration of Sb(III), the pH value of the sample solution, the deposition potential and time, frequency, potential amplitude, and step increment potential were optimized. Under the optimum conditions, a linear response was observed for Pb(II) in the range of 0.5 to 150.0 μg?L^?1. The detection limit for Pb(II) is 0.1 μg?L^?1.

Design, synthesis and inhibitory activities of 8-(substituted styrol-formamido)phenyl-xanthine derivatives on monoamine oxidase B

The design and synthesis of two series of 8-(substituted styrol-formamido)phenyl-xanthine derivatives are described. Their in vitro monoamine oxidase B (MAO-B) inhibition were tested and the effect of substituents on the N-7, phenyl and the substituted positions are discussed. It was observed that compound 9b displayed significant MAO-B inhibition activity and selectivity, fluorine substitution plays a key role in the selectivity of MAO-B inhibition, and the styrol-formamido group at position-3' may enhance the activity and selectivity of 8-phenyl-xanthine analogues. These results suggest that such compounds may be utilized for the development of new candidate MAO-B inhibitors for treatment of Parkinson's disease.