Anodic voltammetric determination of gemifloxacin using screen-printed carbon electrode

The electrochemical oxidation behavior and voltammetric assay of gemifloxacin were investigated using differential-pulse and cyclic voltammetry on a screen-printed carbon electrode.The effects of pH,scan rates,and concentration of the drug on the anodic peak current were studied.Voltammograms of gemifloxacin in Tris-HCl buffer（pH 7.0） exhibited a well-defined single oxidation peak.A differential-pulse voltammetric procedure for the quantitation of gemifloxacin has been developed and suitably validated with respect to linearity,limits of detection and quantification,accuracy,precision,specificity,and robustness.The calibration was linear from 0.5 to 10.0 μM,and the limits of detection and quantification were 0.15 and 5.0 μM.Recoveries ranging from 96.26% to 103.64% were obtained.The method was successfully applied to the determination of gemifloxacin in pharmaceutical tablets without any pre-treatment.Excipients present in the tablets did not interfere in the assay.

Gold Nanoparticles/Thermochromic Composite Film on Screen-Printed Electrodes for Simultaneous Detection of Protein and Temperature

In this study, gold nanoparticles and thermochromic composite films modified screen-printed carbon electrodes (TM-AuNPsSPCEs) were developed as a platform for the simultaneous detection of protein and temperature. The TM-AuNPs composited film had better sensitivity resulting from the gold nanoparticles amplification effect. A phase transition model analysis of TM-AuNPs films found that the TM-AuNPs films had three-phase transition intervals (<45℃, 45℃ to 80℃ and >80℃) which accommodated the temperature requirements for protein denaturation. When used to detect different concentrations of haemoglobin (Hb) solution, the TM-AuNPs modified SPCEs had a better sensitivity in detecting the different concentrations in comparison to TM and AuNP modified SPCEs which showed no clear sensitivity towards the different Hb concentrations. The dual detection and excellent sensitivity show a good application prospect for the study of the TM-AuNPs composite film.

Aptasensor Based on Screen-Printed Carbon Electrodes Modified with CS/AuNPs for Sensitive Detection of Okadaic Acid in Shellfish

Okadaic acid(OA),a small molecule substance derived from shellfish,is one of the most widely distributed marine toxins with acute symptoms of vomiting and diarrhea after accidental ingestion.For this,there is an urgently need for sensitive and reliable methods to detect OA in real shellfish samples.In this study,a simple aptasensor based on screen-printed carbon electrode(SPCE)with modification of chitosan(CS)and gold nanoparticles(Au NPs)was designed for electrochemical determination of OA,and the electrode surface was modified with Au NPs by potential-sweeping electrodeposition,which greatly improved the electrochemical response.The entire detection and characterization process were carried out by cyclic voltammetry(CV)with a linear correlation in the range of 0.01-100 ng/m L and a limit of detection(LOD)of 6.7 pg/m L.Furthermore,recovery rates of 92.3-116%were obtained demonstrating excellent accuracy through the recovery trial of mussel and scallop samples.

Graphene oxide/multi-walled carbon nanotubes/gold nanoparticle hybridfunctionalized disposable screen-printed carbon electrode to determine Cd(II)and Pb(II)in soil

Cadmium(Cd)and lead(Pb)in soil or water environment cause the ecological destruction and environmental deterioration when their contents exceed the natural background values.To trace the concentrations of Cd(II)and Pb(II),a sensitive and selective electrode was developed using disposable screen-printed carbon electrode(SPE)immobilized with a composite film of reduced graphene oxide/carboxylation multi-walled carbon nanotubes/gold nanoparticle hybrid(RGO-MWNT-AuNP)throughπ-πbind.This highly conductive nano-composite layer,“RGO-MWNT-AuNP,”was characterized by scanning electron microscopy,UV-visible spectrometer,cyclic voltammetry,and electrochemical impedance spectroscopy.Square wave stripping voltammetry was applied to RGO-MWNT-AuNP/SPE to electroplate bismuth film and monitor the Cd(II)and Pb(II)simultaneously.To obtain high current responses,the detecting parameters were optimized.Under optimized conditions,the current responses showed a linear relationship with the concentrations of Cd(II)and Pb(II)in the range from 1.0 to 80.0μg/L with a lower detection limit of 0.7μg/L and 0.3μg/L(S/N=3),respectively.Finally,the prepared electrode was further employed to detect Cd(II)and Pb(II)in soil samples with good results.

Rapid detection of organophosphorus pesticide residue on Prussian blue modified dual-channel screen-printed electrodes combing with portable potentiostat

A novel electrochemical method for the rapid detection of organophosphorus pesticide residues was realized on a dual-channel screen-printed electrode （DSPE） that was integrated with a portable smartphone-controlled potentiostat. The two carbon working channels of DSPE were first modified by electrodepositing of Prussian blue. The channels were then modified with acetylcholinesterase （ACHE） via Nation. The inhibition ratio of AChE was detected by comparing the electrical current of acetylthiocholine （ATCh） that was catalyzed by the enzyme electrodes with （channel 1） and without （channel 2） organophosphorus pesticide. Inhibition ratios were related with the negative logarithm of the organophosphorus pesticide （trichlorfon, oxamyl, and isocarbophos） concentrations at optimum experimental conditions （pH 6.9 of electrolyte, 0.2V working potential, 2.5μL AChE modification amount, and 15 min inhibition time）. The linear equations were 1%=32.301gC＋ 253.3 （R=0.9750） for isocarbophos, I% = 35.991gC＋ 270.1 （R = 0.9668） for chlorpyrifos, and 1% = 33.701gC＋ 250.5 （R = 0.9606） for trichlorfon. The detection limits were calculated as 10-7 g/mL. Given that the inhibition ratios were only related with pesticide concentration and not with pesticide species, the proposed electrodes and electrometer can rapidly detect universal organophosphorus pesticides and assess pesticide pollution.

DPSV法快速测定茶叶中Pb的SPCE传感器的研究

为探究出一种食品（茶）中Pb的快速检测新技术，研究以丝网印刷碳电极为支持电极，选用差分脉冲溶出伏安法和电极同位镀汞膜法，以多种绿茶作为固体有机物食物代表的检测对象，进行痕量Ph的快速检测研究。优化同位镀汞膜浓度、时间、最佳底液、沉积电位等6项最佳条件参数。在优化条件下，溶出峰电流与Pb浓度在10-300μg／L范围内呈现良好的线性关系，检出限为2．208μg/L。茶样检测结果其标准偏差小于8％，回收率达到85．2％～109．3％。实验结果表明：研究出的丝网印刷传感器差分脉冲伏安法测定茶叶中的Pb离子具有快速、灵敏、准确、经济等优点，所用丝网印刷传感器可实现一次性使用和批量生产。

Electrochemical Detection of the Different Species of Levofloxacin Using PVC,Carbon Paste and Screen‑Printed Electrodes:Effect of pH

The zwitterionic compound,levofloxacin,was determined for the first time at different pH values in pure samples,pharmaceutical preparations and spiked serum and urine samples.Different types of potentiometric sensors including poly(vinyl chloride)membrane electrode,carbon paste electrode and screen printed electrode,containing the ion pair levofloxaciniumphosphomolybdate as the electroactaive species,were used for this purpose.The effect of pH is the key factor in determining the ratio of the different species that can exist in the medium(zwitterionic,monocationic,dicationic,anionic and neutral),and so it is the controller of the electrochemical performance.The different sensors were fully characterized and optimized in terms of composition,pH effect,selectivity,response and lifetimes.The different sensors showed reliable reversibility and could be utilized for the determination of the drug in real spiked physiological fluids with reliable recovery values.

去甲肾上腺素在印刷碳电极上的电催化行为研究

考察了自制的印刷碳电极活化后对去甲肾上腺素的电化学催化氧化作用研究,结果表明,在3×10-7～1.0×10-4mol/L的浓度范围内,响应电流与去甲肾上腺素的浓度呈线性关系,检出限为1×10-7mol/L.该修饰电极可直接应用于重酒石酸去甲肾上腺素的样品分析检测,结果令人满意.

直接电化学法检测烟酰胺腺嘌呤二核苷酸

本实验所用丝网印刷电极（SPCE）对烟酰胺腺嘌呤二核苷酸（NADH）具有极好的直接电化学响应性能，在低电位（＋O．200V）无需任何修饰的情况下，NADH在SPCE电极表面被氧化，据此可测定其含量。在最优实验条件下，NADH的氧化峰电流与其浓度在2．5×10-6～2．0×10-4mol／L范围内呈线性关系，相关系数r=0．9992，检测限可达1．0×10-6mol／L。该方法检测快速、灵敏度高、重现性好，具有良好的应用前景。

基于纳米金/聚赖氨酸修饰的丝网印刷电极免疫传感器对双酚A的灵敏检测

该文采用一次性丝网印刷碳电极为基底,利用电沉积法制备了聚L-赖氨酸/纳米金修饰电极,构建了双酚A(BPA)电化学免疫传感器。结果表明,当抗原和第一抗体的稀释倍数为1000倍,第一抗体的孵育时间为60 min,电化学检测环境的pH值为7.4时,BPA浓度在1~250 ng/mL范围内与还原峰电流值呈线性关系,其相关系数(r2)为0.993,检出限为0.85 ng/mL。该方法具有良好的特异性、重现性、稳定性,加标回收率为98.3%~104%,说明BPA免疫传感器对实际水样中双酚A的检测具有潜在的应用价值。

应用电化学免疫传感器快速检测甲型H1N1流感病毒

目的以甲型H1N1流感病毒为检测对象,建立一种基于电化学传感技术的流感病毒的检测方法,用于流感病毒的现场快速检测和临床初步筛查。方法将甲型H1N1流感病毒的捕获抗体修饰于丝网印刷电极（SPCE）表面,与抗原结合后,通过辣根过氧化物酶（HRP）标记的检测抗体与其形成免疫夹心复合物,进行信号放大并测定其电化学参数变化以检测目标抗原含量。结果所建立的电化学免疫传感检测器能特异识别甲型H1N1流感病毒,与甲型H3N2和甲型H7N9的HA蛋白、乙型流感病毒、腺病毒和EV71病毒等无交叉反应,检测线性范围为4～64 HA Unit,检测下限为0.41 HA Unit,批内重复性结果 RSD值均〈10%,回收率均＞90%,整个检测过程可在3 h内完成。结论该电化学免疫传感器可实现对甲型H1N1流感病毒的准确和快速检测,且检测设备易携带,有望用于流感病毒的现场快速筛查。

Electrochemical Detection of Salicylic Acid in Pickled Fruit/Vegetable and Juice

Salicylic acid(SA)is used as a preservative in food and a biocide in some consumer products.However,in some countries its use is prohibited.The main problem in the electroanalytical determination of SA is the formation of a passive film during the electro-oxidation of SA.To alleviate the passivation during SA measurement,the experiment was conducted by screen-printed carbon electrode(SPCE).While,differential pulse voltammetry(DPV)was essential for oxidation process to provide better sensitivity.Under conditions of optimized pH and electrolyte concentration,we have calibrated SA in the range of 0.001-0.2 mM,with and LOD of 1.6μM.The relative standard deviation of the sensor responses to 40μM and 100μM SA(n=20)was<3%.SA recoveries in samples such as pickled green mustard,pickled bamboo shoots,pickled mango,pickled lime,pickle ginger and apple juice were found to be in the range of 84-113%.

Handheld Aptasensor for Sandwiched Detection of Chloramphenicol

Chloramphenicol(CAP)is an antifungal agent approved for use in aquarium.However,CAP residue imparts serious adverse effect on human health as well as the ecology.Thus,keeping track of CAP in aquatic products and its environmental metabolites are of great importance.Herein,we developed a novel and neat electrochemical aptasensor for the detection of simulated CAP residual in a sandwich fashion.The screen-printed carbon electrode was employed as the sensing platform and electrodeposited with peculiar nanogolds to enhance the electrochemical performance.For the specific recognition of such small target,a pair of chloramphenicol-binding aptamers,the primary Aptl and the secondary Apt2,were tailored as an artificial single-chained antibody couple,of which the thi-olated Aptl stood on the coated working substrate to capture the analyte,while the biotinylated Apt2 rallied the signal output.In the presence of CAP,Aptl at the lower place cooperated with the upper Apt2 pinched CAP together.After that,the reporter avidin-conjugated horseradish peroxidase associated atop the mounted biotin labels,resulting in an electrocatalytic amplification.In whole,this modular biosensing construction would set a paradigm not just for practicable checkpoint quarantine or point-of-care testing,but potentially adaptable for technological fusion with“Internet Plus”and“Internet of Things”.

Rapid method for on-site determination of phenolic contaminants in water using a disposable biosensor

A disposable biosensor was fabricated using single-walled carbon nanotubes, gold nanoparticles and tyrosinase （SWCNTs-AuNPs-Tyr） modified screen-printed electrodes. The prepared biosensor was applied to the rapid determination of phenolic contaminants within 15 minutes. The SWCNTs-AuNPs-Tyr bionanocomposite sensing layer was characterized with scanning electron micro- scopy, electrochemical impedance spectroscopy and cyclic voltammetry methods. The characterization results revealed that SWCNTs could lead to a high loading of tyrosinase （Tyr） with the large surface area and the porous morphology, while AuNPs could retain the bioactivity of Tyr and enhance the sensitivity. The detection conditions, including working potential, pH of supporting electrolyte and the amount of Tyr were optimumed. As an example, the biosensor for catechol determination displayed a linear range of 8.0 × 10^-8 to 2.0 × 10^- 5 mol.L-1 with a detection limit of 4.5 × 10^-8 mol.L-1 （S/N= 3）. This method has a rapid response time within 10 s, and shows excellent repeatability and stability. Moreover, the resulting biosen- sor could be disposable, low-cost, reliable and easy to carry. This kind of new Tyr biosensor provides great potential for rapid, on-site and cost-effective analysis of phenolic contaminants in environmental water samples.