Improved Detection of Ascorbic Acid with a Bismuth-Silver Nanosensor

Bismuth-silver bimetallic nanoparticles glassy carbon electrode (Bi-AgNPs/GCE) was employed for the determination of ascorbic acid (AA) in fruit and pharmaceutical samples. In this study, the Bi-AgNPs/GCE showed excellent electrochemical catalytic activities toward AA oxidation compared with bare GCE. Ascorbic acid gave a sensitive oxidation peak at 0.23 V using differential pulse voltammetry. Under optimized experimental conditions, the limit of detection for AA was 0.16 μM (for S/N?=?3), the analytical range for AA was between 0.4 and 1.2 μM (R ²?=?0.994) and the RSD was 5.84 % (n?=?10). The proposed method showed good stability, reproducibility, and repeatability as well as good recovery in fruit and pharmaceutical samples.     

抗坏血酸在聚对苯二酚/铜复合膜修饰电极上电催化氧化行为的探究

利用电沉积法制备了聚对苯二酚/铜(PHQ/Cu)复合膜修饰电极,并采用循坏伏安法探究了抗坏血酸(AA)在该电极上的电催化氧化行为。结果表明,与裸电极、PHQ修饰电极相比,PHQ/Cu复合膜修饰电极对AA具有更好的催化作用,表明两种修饰剂对AA的电催化氧化有良好的协同催化作用;在0.1 mol/L磷酸盐缓冲溶液(pH=4.35)中,AA的氧化峰电流与其浓度在5×10-4~1.0×10-1 mol/L范围内呈良好的线性关系,线性方程为lgI=0.7364lgc+1.6932,R2=0.9959,检出限为2.0×10-5 mol/L。该复合膜修饰电极在冰箱内贮存9 h,其电化学信号基本保持不变,且共存物几乎不干扰AA的测定,表明电极具有良好的稳定性和较强的抗干扰能力,可以用于饮料中AA含量的测定,回收率在95.5%~109.1%之间。     

聚嘧啶/石墨烯复合材料修饰电极同时测定日落黄和酒石黄

采用液相剥离法制备石墨烯纳米片悬浮液,将其直接滴涂于玻碳电极表面,制备石墨烯修饰电极,再采用电沉积法制得聚嘧啶/石墨烯复合膜修饰电极。采用扫描电子显微镜对该修饰电极的表面形貌进行表征;采用循环伏安法和方波伏安法探究日落黄和酒石黄在该修饰电极上的电化学行为。结果表明,该复合膜修饰电极对两种合成色素均表现出良好的电催化性能。在优化实验条件下,日落黄和酒石黄同时被检测,线性检测范围分别为0.002~2?mol/L和0.003~6?mol/L,检测限分别为0.5 nmol/L和0.9 nmol/L。该方法可用于食品中日落黄和酒石黄的同时测定。     

纳米Cu2O-还原石墨烯复合修饰玻碳电极用于多巴胺的检测

通过电化学还原法制备纳米Cu2O/还原石墨烯复合修饰电极（Cu2O-reduced graphene oxide nanocomposite modified glass carbon electrode,Cu2O-RGO/GCE）,用于多巴胺（dopamine,DA）的检测。采用扫描电镜和X-射线粉末衍射仪对不同修饰电极进行微观形貌表征,进一步优化电化学还原条件和测定DA实验条件。此外,通过循环伏安法考察DA在裸电极及RGO或Cu2O-RGO上的电化学响应。Cu2O-RGO/GCE实现抗坏血酸（ascorbic acid,AA）、DA和尿酸（uric?acid,UA）氧化峰的有效分离,AA-DA和DA-UA的氧化峰电位差分别为204?mV和144?mV。该修饰电极检测的线性范围为1×10－8～1×10－6?mol/L和1×10－6～8×10－5?mol/L,检出限为6.0×10－9?mol/L。该修饰电极用于盐酸多巴胺注射液和血清中DA的含量测定,获得结果较好。     

纳米金掺杂石墨烯修饰玻碳电极选择性测定多巴胺

构建纳米金(Au)掺杂石墨烯(GS-Nafion)修饰玻碳电极(GCE)的电化学传感器(GCE/GS/Nafion/Au),研究多巴胺(DA)和抗坏血酸(AA)在上述电极的电化学行为,并用于DA的选择性测定。将GS-Nafion溶液涂覆于GCE表面制得GCE/GS/Nafion电极,采用化学镀方法于GCE/GS/Nafion电极表面生成Au制得GCE/GS/Nafion/Au电极,采用扫描电镜(SEM)表征GS、化学镀Au和电极的制备过程,循环伏安(CV)法和示差脉冲伏安(DPV)法研究DA的电化学性质。在优化的实验条件下,DA浓度与DPV法氧化峰电流大小在1.0×10-7～1.0×10-4mol/L之间呈线性关系,线性相关系数为0.9988,检出限为4.2×10-8mol/L。该电极制备过程简单、灵敏度高、抗干扰性强,可以用于DA的测定,结果令人满意。     

Trace analysis of bromate, chlorate, iodate, and perchlorate in natural and bottled waters

A simple and rapid method has been developed to simultaneously measure sub-microg/L quantities of the oxyhalide anions bromate, chlorate, iodate, and perchlorate in water samples. Water samples (10 mL) are passed through barium and hydronium cartridges to remove sulfate and carbonate, respectively. The method utilizes the direct injection of 10 microL volumes of water samples into a liquid chromatography-tandem triple-quadrupole mass spectrometry (LC-MS/MS) system. Ionization is accomplished using electrospray ionization in negative mode. The method detection limits were 0.021 microg/L for perchlorate, 0.045 microg/L for bromate, 0.070 microg/L for iodate, and 0.045 microg/L for chlorate anions in water. The LC-MS/MS method described here was compared to established EPA methods 300.1 and 317.1 for bromate analysis and EPA method 314.0 for perchlorate analysis. Samples collected from sites with known contamination were split and sent to certified laboratories utilizing EPA methods for bromate and perchlorate analysis. At concentrations above the reporting limits for EPA methods, the method described here was always within 20% of the established methods, and generally within 10%. Twenty-one commercially available bottled waters were analyzed for oxyhalides. The majority of bottled waters contained detectable levels of oxyhalides, with perchlorate < or = 0.74 microg/L, bromate < or = 76 microg/L, iodate < or = 25 microg/ L, and chlorate < or = 5.8 microg/L. Perchlorate, iodate, and chlorate were detectable in nearly all natural waters tested, while bromate was only detected in treated waters. Perchlorate was found in several rivers and reservoirs where itwas not found previously using EPA 314.0 (reporting limit of 4 microg/L). This method was also applied to common detergents used for cleaning laboratory glassware and equipmentto evaluate the potential for sample contamination. Only chlorate appeared as a major oxyhalide in the detergents evaluated, with concentrations up to 517 microg/g. Drinking water treatment plants were also evaluated using this method. Significant formations of chlorate and bromate are demonstrated from hypochlorite generation and ozonation. From the limited data set provided here, it appears that perchlorate is a ubiquitous contaminant of natural waters at trace levels.     

基于石墨烯构建的电化学传感器测定抗坏血酸

制备石墨烯修饰电极建立电化学方法实现对抗坏血酸的测定。采用电化学还原技术,通过一步电沉积制备石墨烯修饰玻碳电极(ERGO/GCE),并用循环伏安法研究抗坏血酸(ascorbicacid,AA)在该修饰电极上的电化学行为,结果表明,所制备的石墨烯修饰电极较裸玻碳电极对抗坏血酸有显著的电催化效果。在p H=6.5的磷酸盐缓冲溶液中,AA在-0.4 V～0.8 V扫描电位范围内有1个不可逆的氧化峰出现。在优化的实验条件下,AA的浓度在1.7×10-3 mol/L～2×10-5 mol/L范围内与其氧化峰电流值呈良好的线性关系,相关系数为0.991,最低检出限为9×10-6mol/L(S/N=3)。探究了修饰电极的稳定性、抗干扰性,结果表明电极稳定性良好,抗干扰能力较强。用此修饰电极对橙汁中的AA含量进行检测,加标回收率在97.95%～98.68%之间。用本文建立的电化学方法可用于橙汁中AA的测定,结果比较满意。     

Comparison of inductively coupled plasma-mass spectrometry and radiochemical techniques for total uranium in environmental water samples

Inductively coupled plasma-mass spectrometry (ICP-MS) method EPA 200.8 is gradually finding acceptance as an alternative to uranium analysis. A comparison of the ICP-MS with the accepted radiochemical method EPA 908.0 has been carried out based on data from laboratory control standards, national proficiency test samples, and environmental and drinking water samples from the State of Utah. The method detection limit (MDL) for ICP-MS was determined to be 0.017 microg/L or (0.011 pCi/L), and the minimum reporting limit (MRL) was 0.17 microg/L (MDL x 10) or (0.11 pCi/L). The minimum reporting limit for radiochemical 908.0 method is 1 pCi/L. Our spiked matrix recoveries, spiked blank samples, and reference materials deviate only a few percentage from the listed true values. Results demonstrate that the ICP-MS is a superior analytical tool for the determination of uranium in drinking and environmental waters at concentrations required by the United States Environmental Protection Agency.     

色氨酸在Nafion-聚半胱氨酸修饰电极上的电化学行为及分析测定

采用滴涂和电聚合的方法构筑Nafion-聚半胱氨酸修饰的玻碳电极(Nafion/L-cys/GCE),采用循环伏安法(CV)研究色氨酸在此修饰电极上的电化学行为,利用线性扫描伏安法(LSV)对色氨酸进行定量分析。结果表明,该修饰电极对色氨酸电化学氧化具有明显催化作用。色氨酸浓度在0.4×10-6~40.0×10-6mol/L范围内与氧化峰电流有良好线性关系,回归方程为I_pa(μA)=0.6997c(10-6mol/L)+5.3(R2=0.9844),检测限为1.0×10-7 mol/L。该方法用于香蕉中色氨酸的检测,回收率为95%~98%。     

间苯氧基苯甲酸分子印迹膜的电化学聚合制备及其应用

研究间苯氧基苯甲酸快速准确的检测方法可为环境中间苯氧基苯甲酸监测以及拟除虫菊酯农药代谢物的生态风险评价提供技术支持。本实验以邻氨基酚为功能单体,以间苯氧基苯甲酸为模板分子,采用循环伏安法在玻碳电极表面聚合形成可用于检测间苯氧基苯甲酸的分子印迹膜,结合电化学技术用于水中间苯氧基苯甲酸的检测研究,30 s可对间苯氧基苯甲酸完成响应,在2.00～11.00 mg/L质量浓度范围内,分子印迹膜的响应电流变化值与间苯氧基苯甲酸质量浓度呈线性关系,线性方程为y=0.29x＋2.16,相关系数为0.99,方法的检出限为1.47 mg/L;对加标水样进行检测,回收率在92.00%～101.00%之间。     

辣根过氧化物酶-金属有机骨架纳米纤维复合物生物传感器的制备及其用于食品中过氧化氢残留检测的研究

以金属有机骨架纳米纤维作为辣根过氧化物酶固定化材料,壳聚糖作为成膜剂,使用滴涂法制备电化学生物传感器(HRP-MONFs/Chit/GCE)用于检测食品中过氧化氢残留。实验采用交流阻抗法(EIS)和循环伏安法(CV)研究所制备传感器的电化学特性,并对其制备方法和检测条件进行优化。结果表明,HRP-MONFs/Chit/GCE在过氧化氢浓度为12.5~675 μmol/L范围内表现出较好的线性关系(R2=0.999),最低检测限为0.97 μmol/L。所制备的HRP-MONFs/Chit/GCE具有较好的储存稳定性,在4℃条件下,24 d的储藏期内保持其初始94%的电流响应值。HRP-MONFs/Chit/GCE具有较好的选择性且被成功的应用于固态与液态食品中过氧化氢残留检测。     

基于功能化多壁碳纳米管的乙酰胆碱酯酶生物传感器制备

将功能化多壁碳纳米管(FCNTs)结合壳聚糖(CHIT)和戊二醛(GTA)导电聚合物形成凝胶溶胶,将该凝胶溶胶悬滴在玻碳电极(GCE)表面制得FCNTs-CHIT-GTA/GCE电极,结合自制的乙酰胆碱酶膜生成一种反应灵敏、快速、稳定、用于检测有机磷农药的电流型生物传感器。结果表明：该传感器具有出峰电位低、峰流值高、电子传递速率高、阻抗值小等优点,在研究不同浓度敌敌畏对酶抑制率的关系时,得到的关系曲线线性良好,最低检出限为20ng/L。该传感器适用于有机磷农药残留跟踪检测。     

基于碳纳米管组装电化学传感器测定金丝桃苷的含量

目的:采用单壁碳纳米管(SWCNTs)修饰玻碳电极(GCE),制作电化学传感器,研究金丝桃苷在传感器表面的电化学行为,建立一种简单的、高灵敏的金丝桃苷的电化学检测新方法。方法:将羧基化SWCNTs滴在GCE表面,采用循环伏安法(CV)研究了金丝桃苷在传感器表面的电化学行为,并对测量条件进行了优化。结果:和裸GCE电极相比较,金丝桃苷在GCE/SWCNTs电极表面的氧化峰电流和还原峰电流均急剧增加,氧化峰电流和还原峰电流与扫描速度的平方根成正比,说明金丝桃苷在修饰电极表面的反应是受扩散控制的过程。在缓冲液的pH为6.0、碳纳米管的用量为10 μL、检测电位为0.34 V的优化条件下时,金丝桃苷浓度在3.0×10-9~1.0×10-7范围内与氧化电流呈现良好的线性关系,检出限为2.41×10-9 mol/L(S/N=3)。结论:该方法灵敏度高,简单易行,具有较好的重现性及稳定性,可用于金丝桃苷的检测。     

石墨烯/四氧化三钴电化学传感器的建立及饼干中香兰素检测分析

本文将石墨烯（GR）滴涂在玻碳电极（GCE）后,再通过循环伏安法电聚合氧化Co（COOH）₂制得Co₃O₄/GR/GCE修饰电极作为食品中检测香兰素的新型电化学传感器。通过扫描电镜技术对Co₃O₄/GR复合纳米材料进行了表征并优化了实验条件。结果表明,当1 mg/mL GR滴涂量为8 μL,Co（COOH）₂聚合圈数为20圈,0.1 mol/L pH 4.5磷酸缓冲溶液中,香兰素在该传感器下线性关系良好（0.1～80 μmol/L）,线性方程为:I_p （μmol/L）=0.1518C+0.5103 （R2=0.997）,检测限为0.033 μmol/L （S/N=3）。将此方法应用于饼干样品中香兰素检测,回收率良好,相对标准偏差仅1.47%。综上,该电化学传感器灵敏度较高、稳定性良好,在实际样品检测中具有可行性,拥有广阔的应用前景。     

团聚状纳米AuPd修饰的H2O2生物传感器研究

采用微胶束法室温条件下制备团聚状的AuPd合金纳米粒子,使用紫外可见光谱(UV-vis),透射电镜(TEM),X-射线粉末衍射(XRD)和X-射线能量色散谱(EDS)表征团聚结构AuPd合金纳米粒子的形貌、尺寸、结构和组成。用制备的AuPd纳米粒子修饰辣根过氧化物酶玻碳电极,制备无电子媒介的过氧化氢生物传感器HRP/AuPd/GCE。使用循环伏安法和计时电流法表征了HRP/AuPd/GCE对H2O2的检测性能。实验结果表明:该传感器对H2O2具有良好的检测性能和稳定性,在H2O2浓度为1×10-7mol/L～5×10-3mol/L范围内检测电流与H2O2浓度有线性关系,线性相关系数R2=0.995 01,检出限为7.6×10-7mol/L。     

MnO2/ZnO/GCE电化学传感器的构建及对蜂蜜中磺胺甲恶唑的检测

为快速检测蜂蜜中磺胺甲恶唑(sulfamethoxazole,SMZ)的残留，将水热法制备的氧化锌(ZnO)及共沉淀法制备的二氧化锰(MnO₂)材料复合于玻碳电极(GCE)上，构建了MnO₂/ZnO/GCE电化学传感器用于检测SMZ。采用扫描电镜(SEM)及红外光谱(FT-IR)对复合材料的形貌、结构进行表征。利用差分脉冲伏安法(DPV)对复合材料的比例、修饰量进行探究，从而对传感器的构建条件进行优化。并采用差分脉冲伏安法(DPV)及循环伏安法(CV)对缓冲溶液pH、扫描速率等检测条件进行考察。结果表明，当m(ZnO):m(MnO₂)质量比为1:0.6、MnO₂/ZnO复合材料修饰量为1.7×10-3 mg/mm2、缓冲溶液pH为8、扫描速率为30 mV/s时，该传感器对SMZ具有良好的检测效果。在0.3～100μmol/L范围内，峰电流与SMZ浓度呈良好的线性关系，其线性方程为Ip=0.0843 c+4.5168(R2=0.9916)，检测限为0.39μmol/L，定量限为1.30μmol/L。将...     

Avoiding hydrolysis of fuel ether oxygenates during static headspace analysis

The determination of fuel ether oxygenates in groundwater was found to be problematic when samples are preserved at pH < 2 and then analyzed using heated headspace sampling. Acid catalyzed the hydrolysis of tert-amyl methyl ether, ethyl tert-butyl ether, and methyl tert-butyl ether during headspace sampling when aqueous samples were heated at 80 degrees C, a typical temperature used for heated headspace sampling. Hydrochloric acid at pH 2 did not cause hydrolysis of oxygenate ethers in samples stored for 28 d at 4 degrees C. When trisodium phosphate was used to preserve the sample or to adjust the pH of samples preserved with acid before headspace sampling, the recovery of spiked ethers was excellent. The heated headspace method was also applicable for the determination of other fuel oxygenates including ethanol, tert-butyl alcohol (TBA), tert-amyl alcohol (TAA), isopropyl alcohol (IPA), acetone, and monoaromatic compounds found in gasoline including benzene, toluene, ethylbenzene, xylenes, and trimethylbenzenes. The method detection limits range from 0.1 to 0.2 microg/L for the ethers and aromatics. For alcohols and acetone, the method detection limits were 0.8 microg/L for TBA, 18 microg/L for ethanol, 1.2 microg/L for TAA, 5.5 microg/L for IPA, and 3.3 microg/L for acetone. The heated headspace method yielded accurate results for ether oxygenates in samples containing a wide range of gasoline concentrations (2500-100000 microg/L).     

Nafion-碳纳米管修饰电极溶出伏安法测定大米中痕量铅

用Nafion和碳纳米管联合修饰玻碳电极,探讨铅离子在修饰电极上的溶出伏安行为。建立了基于化学修饰电极检测大米中铅的溶出伏安电化学传感方法。实验结果表明,在pH值4.0、0.1mol/L醋酸-醋酸盐溶液的缓冲体系,富集电位-0.6V,富集时间180s,铅离子浓度在0.01～1mg/L范围内与溶出峰电流呈现良好的线性关系,检测限可达5μg/L,达到大米卫生标准。该方法操作简便,检测时间不超过5min,适合大批量大米样品检测,具有很好的准确性、灵敏度和稳定性。为进一步研究重金属现场快速检测奠定良好的实验基础。     

基于多壁碳纳米管修饰四氧化三钴传感器检测白菜中杀螟硫磷

目的 基于多壁碳纳米管修饰四氧化三钴(Co3O4@MWCNTs)纳米复合物,成功构建了一种用于白菜样品中快速检测杀螟硫磷的电化学传感器。方法 将以醋酸钴水合物为钴源,而采用简便水热法制备的四氧化三钴纳米颗粒与多壁碳纳米管复合成Co3O4@MWCNTs纳米材料,以Co3O4@MWCNTs纳米复合物修饰的玻碳电极(GCE)为工作电极,利用循环伏安法(CV)研究了杀螟硫磷在修饰电极界面的电化学行为;并通过逐步优化支持电解质的PH值、复合材料质量比等检测条件。结果 实验结果表明,Co3O4@MWCNTs/GCE改性电极能够实现对杀螟硫磷的灵敏检测。在最优条件下,该传感器的线性浓度范围为1.0×10-5~1.4×10-4 mol/L,R2=0.991,检出限为7.8×10-8 mol/L(S/N=3);并成功用于实际白菜样品中杀螟硫磷的加标回收实验,回收率为93.7%~97.6%。结论 Co3O4和MWCNTs复合后制备的传感器不仅可以选择性识别杀螟硫磷,达到快速检测目标物的需求。而且,其电化学性能也得到了明显的提升,展现出较高的灵敏度,表明该传感器在现场检测中具有非常大的应用潜力。     

基于CoOOH纳米片氧化酶活性的比率荧光传感器检测抗坏血酸

研究建立一种基于羟基氧化钴纳米片(CoOOH)类氧化酶活性的比率荧光传感器,可快速、灵敏、准确地测定抗坏血酸(Ascorbic acid,AA).在氢氧化钠溶液中,以氯化钴为原料、次氯酸钠为氧化剂,在超声条件下制备具有类氧化酶活性的CoOOH纳米片,并采用透射电子显微镜(TEM)、紫外可见吸收光谱(UV-vis)、X射...