加速溶剂萃取-液相色谱-原子荧光法同时测定动物源性食品中阿散酸、硝苯砷酸与洛克沙砷的残留量

研究建立了加速溶剂萃取-液相色谱-原子荧光(ASE-LC-AFS)测定动物源性食品中阿散酸(ASA)、硝苯砷酸(NIT)与洛克沙砷(ROX)的残留量的方法。比较了超声离心提取和加速溶剂萃取技术,并优化了加速溶剂萃取技术的提取溶剂比例、提取温度、提取时间和提取次数。优化了液相色谱流动相和原子荧光的工作条件。在0～2.0 mg·L-1范围内内阿散酸、硝苯砷酸和洛克沙砷的线性关系良好,线性相关系数大于0.999,阿散酸、硝苯砷酸、洛克沙砷检出限(S/N=3)分别为2.4,7.4,4.1 μg·L-1。2种样品在0.5,2,5 mg·kg-13个加标水平下的平均回收率为阿散酸87.1%～93.2%, 硝苯砷酸85.2%～93.9%, 洛克沙砷84.2%～93.7%,相对标准偏差(RSD)分别为1.3%～4.6%,1.2%～4.2%,1.1%～4.5%。本方法操作简便,重现性好,适用于动物源性食品中ASA,NIT和ROX的分析。     

石墨炉原子吸收光谱法测定海藻制品中的砷

应用石墨炉原子吸收光谱技术建立了在海藻制品中测定总砷和三价无机砷的方法,为开展海藻制品中无机砷的监测和食品安全风险评估提供准确的检测方法。采用湿法消解和微波消解为测定总砷的前处理方式,9m ol/L盐酸浸泡后乙酸丁酯萃取和纯水反萃取作为海藻制品中三价无机砷的提取方式,分别利用塞曼扣背景和氘灯扣背景的石墨炉原子吸收光谱法测定总砷和三价无机砷。塞曼扣背景测定砷的线性范围为3.0—60μg/L,定量限(LOQ)为2.9μg/L,精密度为3.6%,回收率为90%—102%;氘灯扣背景测定砷的线性范围为4.0—80μg/L,定量限(LOQ)为3.6μg/L,精密度为4.1%,回收率为88%—109%。本法对三价无机砷的提取方法简便实用、提取效率高。原子吸收光谱法的两种背景校正方式测定总砷及三价无机砷的结果准确可靠。为基层实验室开展食品中总砷以及三价无机砷的测定提供实用、可靠的分析方法。     

不同产地几种中药材中重金属含量测定及砷的形态分析

通过对不同产地几种中药材中砷、铅、镉、铜以及无机砷、三价砷含量的分析测定,得出样品中砷、铅、镉、铜以及无机砷、无机三价砷的测定RSD〈3%,加标回收率在91.32%—109.7%之间。11个样品的总砷含量在0.047—1.681μg/g之间,均低于2μg/g;无机砷含量为0.023—1.294μg/g;无机三价砷含量为0.019—0.918μg/g;铅含量两份样品未检出,其余样品为0.007—0.786μg/g,均低于5μg/g;镉的测定,两份样品未检出,其余样品含量为0.007—2.129μg/g,其中两份样品大于0.3μg/g;铜含量为4.441—14.07μg/g,均低于20μg/g。研究发现同种药材不同产地的重金属含量差异较大,部分产地金银花中镉含量超标严重,无机砷和三价砷含量相对较高,需引起重视。     

云南出口三七中总砷及无机砷的测定

三七中总砷及无机砷按GB/T5009.11-2003进行了大量的测试。三七试样经湿消解,加入硫脲使五价砷还原为三价砷,再加入硼氢化钾使其还原生成砷化氢,和氩气一起进入石英原子化器中分解为原子态砷,测其荧光强度,得总砷。未经消解的三七试样在6mol/L盐酸和水浴条件下,无机砷以氢化物形式被提取,实现无机砷和有机砷的分离,在2mol/L盐酸条件下测定,同总砷原理。通过对大量测试数据的分析,讨论了其无机砷在总砷中所占含量的百分比及毒性。     

原子荧光光谱法测定海藻肥中总砷与无机砷

原子荧光光谱法测定海藻肥中总砷和无机砷。硝酸-硫酸-高氯酸体系进行消解测定总砷,5%HCl提取测定无机砷,仪器的检出限为0.05μg/L,相对标准偏差为3.2%(n=11),样品中总砷和与无机砷的加标回收率分别为89.8%和86.8%。     

原子荧光光谱法测定食品添加剂磷酸中的砷

建立了原子荧光光谱法测定食品添加剂磷酸中砷的方法.并对负高压、灯电流、载气流量、屏蔽气流量、硫脲与抗坏血酸浓度、载流介质浓度、硼氢化钠浓度等作了研究并予以优化.方法的线性范围为0.0-40.0ng/mL,相关系数为1.0000,检出限为0.02ng/mL,相对标准偏差在0.82％-1.86％之间,试样加标回收率在95.10％-102.20％之间.方法操作简便、灵敏度高、检出限低、重复性和再现性好,完全适用于食品添加剂磷酸中砷的检测.     

表面增强拉曼光谱技术在动物源性食品兽药残留检测中的应用

动物源性食品是人类营养摄入必不可少的食品之一,兽药被广泛用于动物饲养和疾病防治,但兽药残留超标等问题对消费者的健康安全构成了严重威胁。为防止受污染的食品对消费者造成危害,研发快速有效的兽药残留分析方法非常必要。表面增强拉曼光谱法(SERS)作为一种痕量的检测方法,有望能够满足目前动物源性食品高效、快速、灵敏的检测需求。综述了SERS方法在动物源性食品兽药残留检测中的研究进展,包括肉类(猪肉、鸡肉、鸭肉、鱼肉)、乳和乳制品及蜂蜜中兽药残留的SERS分析研究。概述了SERS技术在肉类食品中主要兽药残留的检测应用进展。家禽肉中的兽药分析包括四环素类药物、磺胺类药物、恩诺沙星和激素类等药物;猪肉中的兽药主要分析了β-受体激动剂、氯霉素、左旋咪唑等药物;鱼肉中的兽药分析了染料类、磺胺类和氯霉素等药物。对乳和乳制品中的四环素类、氨基糖苷类、青霉素类、酰胺醇类药物的SERS检测进行了总结讨论。简述了SERS在蜂蜜中氯霉素类、四环素类等药物的分析。对SERS在动物源性食品的研究发展方向和应用前景进行了总结和展望。虽然SERS作为一种快速、超灵敏的检测方法,在分析复杂食品体系中的微量或痕量化合物方面,尤...     

在线捕集分离联用技术对食品调料中砷形态分析方法研究

成功建立了冷捕集-气相色谱-氢化物发生-原子荧光光谱分析测定食品调料(酱油和醋)中砷形态的方法。以脱脂棉为分离介质,用液氮对样品中生成的气态砷化合物进行冷捕集,常温下不同砷形态化合物即可以实现基线分离,随后被原子荧光光谱检测。实验考查了酸介质的种类和酸度、KBH₄溶液的浓度、反应时间以及载气(He)的流量等实验条件对测定结果的影响。结果表明,在优化后的实验条件下,方法对As(Ⅲ),As(Ⅴ),MMA(Ⅴ)和DMA(Ⅴ)的检出限分别为0.2,0.2,0.3,0.8 ng·mL-1,对酱油和醋As(Ⅲ),As(Ⅴ),MMA(Ⅴ)和DMA(Ⅴ)的回收率为93.07%～103.54%。与传统的液相色谱分离方法相比,该方法不用对样品进行特殊前处理,分析速度快,灵敏度高,适合于对食品调料中砷形态尤其是无机砷形态的准确、快速分析测定。     

土壤中无机砷测定的三种前处理方法比较

对土壤无机砷分析的样品前处理技术-微波辅助提取、超声波提取、水浴提取进行了对比研究.结合氢化物发生-原子荧光光谱(HG-AFS)测定技术比较了3种方法对国家土壤标准物质中无机砷的提取效果,并对溶剂类型、提取时间和提取剂用量等影响因素进行了考察.与超声波提取法和水浴提取法相比,微波辅助提取法具有快速、高效的优势.     

ICP-AES测定高砷铁矿中砷和钒

建立了用硝酸-氢氟酸-高氯酸消解,ICP-AES测定铁矿中砷和钒的方法.该方法检出限砷为50mg/kg,钒为8mg/kg;相对标准偏差(RSD)砷为4.92%以下,钒为4.37%以下;加标回收率砷在95.3%-105.0%之间,钒在96.5%-102.1%之间.本法可以对铁矿中的砷和钒进行较为理想测定.     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Hybrid Wavelength and Code Division Multiple Access in Optical Networks

A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.