Prussian Blue Analogue of Copper-Cobalt Decorated with Multi-Walled Carbon Nanotubes Based Electrochemical Sensor for Sensitive Determination of Nitrite in Food Samples

Tuning the Fe/Co ratio towards a bimetallic Prussian blue analogue for the ultrasensitive electrochemical sensing of 5-hydroxytryptamine

Lack of highly efficient, inexpensive, and easily available catalysts severely limits the practical applicability of electrochemically sensing assay towards 5-hydroxytryptamine (5-HT). Herein, four kinds of Fe-Co bimetallic Prussian blue analogues (FeCo-PBAs) with different molar ratios of Fe to Co were prepared using a simple coprecipitation method. Interestingly, Fe(III) in K₃ [Fe(CN)₆] can be reduced to Fe(II) by adding trisodium citrate dehydrate, which could offer a new clue to synthesize PBAs with Fe(II) core ions. With the optimizational FeCo-PBA synthesized at a 0.5/1 M ratio of Fe to Co as an electrocatalyst, the constructed sensor shows excellent comprehensive performance for the 5-HT assay with a high sensitivity of 0.856 μA μM^-1 and an ultralow detection limit of 8.4 nM. Under the optimum conditions, linearity was obtained in the ranges of 0.1-10.0 μM and 10.0-200.0 μM and preferable recoveries ranged from 97.8% to 103.0% with relative standard deviation (RSD) < 4.0%. The integrated properties of FeCo-PBA can be comparable to previously reported electrocatalysts for the 5-HT assay including noble metal-based and expensive carbon (graphene and carbon nanotubes)-based electrocatalysts. The proposed sensor also exhibits outstanding selectivity, reproducibility, and practicality for real sample analyses. This work is the first report on the PBA-based sensor for the 5-HT assay, verifying the practicability of this high-performance sensor for the 5-HT assay.

Rapid detection of nitrite based on nitrite-oxidizing bacteria biosensor and its application in surface water monitoring

Timely and sensitive detection of nitrite is of great significance for human health protection and water pollution treatment. However, many biosensors can only determine the comprehensive toxicity of the water, and there are few electroactive biofilm (EAB) sensors for the specific detection of pollutants. Biofilms formed by bacteria with specific functions can improve the specificity of nitrite identification by biosensors. This study developed a novel, rapidly responding, high sensitivity (958.6 μAμM^-1cm^-2), wide detection range and anti-interference electrochemical biosensor based on electroactive nitrite-oxidizing bacteria. The biosensor could accurately detect nitrite in the range of 0.3-100 mg/L within 3 min by the cyclic voltammetry (CV) method. The bioelectrode could perform stable detection of nitrite over 200 cycles. The specificity of the biosensor for detecting nitrite was demonstrated by the presence of nitrite oxidizing bacteria (NOB) and nitrite oxidase enzyme (NXR) on the electrode biofilm. The biosensor performed well in wetlands and rivers, with an RSD <14.8% in the detection of nitrite at low concentrations, and further revealed the nitrification occurrence. Our study provided a feasible way for the development of a highly sensitive, rapidly responding and stable electrochemical biosensor, which also exhibited potential applications for long-term detection of nitrite and assessment of ecological function in surface water (rivers, lakes, wetlands, marshes, etc.).

Amperometric detection of antibiotic drug ciprofloxacin using cobalt-iron Prussian blue analogs capped on carbon nitride

Ciprofloxacin (CIP) electrochemical sensor was constructed using cobalt-iron Prussian blue analogs decorated on carbon nitride (Co-Fe-PBA@CN). Co-Fe-PBA decorated on CN was fabricated using a simple sonication-assisted hydrothermal method to prepare the composite to obtain a cube-shaped structure decorated on CN sheets. The fabricated Co-Fe-PBA@CN was physically characterized using XRD and SEM analysis. Then, the fabricated composite was electrochemically studied to sense antibiotic drug ciprofloxacin (CIP). The electrochemical behavior was investigated using tools such as cyclic voltammetry (CV) and amperometric I-t studies. The Co-Fe-PBA@CN modified electrode displays a wide linear range (0.005-300 and 325-741 μM) with a low detection limit (0.7389 and 1.0313 nM) and good sensitivity (0.3157 and 0.2263 μA.μM^-1cm^-2) toward CIP. The Co-Fe-PBA@CN modified electrode also exhibits good selectivity, reproducibility, and repeatability toward CIP. The proposed sensor was validated with real sample analysis, biological samples like urine and blood serum containing commercially available ciprofloxacin tablets were studied, and the results demonstrate good viability.

Synthesis and Applications of Prussian Blue and Its Analogues as Electrochemical Sensors

Prussian blue (PB) and its analogue (PBA) are a kind of representative cyanide-based coordination polymer. They have received enormous research interest and have shown promising applications in the electrochemical sensing field due to their excellent electrochemical activity and unique structural characteristics including open framework structure, high specific surface area, and adjustable metal active sites. In this review, we summarize the latest research progress of PB/PBA as an electrochemical sensor in detail from three aspects: fabrication strategy, synthesis method and electrochemical sensor application. For the fabrication strategy, we discussed different fabrication methods containing the combination of PBA and carbon materials, metal nanoparticles, polymers, etc., respectively, as well as their corresponding sensing mechanism for improving performance. We also presented the synthesis methods of PB/PBA materials in detail, such as: coprecipitation, hydrothermal and electrodeposition. In addition, the effects of different methods on the morphology, particle size and productivity of PB/PBA materials are also concluded. For the application of electrochemical sensors, the latest progress of such materials as electrochemical sensors for glucose, H2 O2 , toxic compounds, and biomolecules have been summarized. Finally, we conclude remaining challenges of PB/PBA-based materials as electrochemical sensors, and provide personal perspectives for future research in this field.

[Determination of nine N-nitrosamines in animal derived foods by QuEChERS-isotope dilution combined with gas chromatography-tandem mass spectrometry]

建立了同时测定动物源性食品中9种N-亚硝胺类化合物的气相色谱-串联质谱分析方法。当下动物源性食品中N-亚硝胺类化合物污染种类较多,对人体危害较大,但国标GB 5009.26-2016仅针对N-二甲基亚硝胺的检测,且存在样品前处理复杂、标准方法回收率低、再现性差等问题,因此建立同时快速检测多种N-亚硝胺类化合物的方法有一定现实意义。称取10.0 g样品,置于50 mL离心管中,加入200 μL内标工作液和10 mL乙腈,冷冻30 min后,加入4 g硫酸镁和1 g氯化钠进行脱水,以9000 r/min离心5 min。取5 mL上清液使用150 mg聚苯乙烯二乙烯苯(PLS-A)粉末净化,再使用1.6 g MgSO₄和0.4 g NaCl脱水,过0.22 μm滤膜,上机分析。在初始温度为50 ℃时采用程序升温模式,0.16 min后,以900 ℃/min的速率将温度升至220 ℃。采用毛细管气相色谱柱HP-Innowax(30 m×0.25 mm×0.25 μm)分离,使用电子轰击电离(EI)源检测,在多反应监测模式下,以保留时间和特征离子对信息进行定性和定量分析,使用内标法定量N-亚硝胺类化合物。结果表明,N-亚硝胺类化合物在0.1~50.0 μg/L范围内具有良好的线性关系,方法的检出限(S/N=3)和定量限(S/N=10)分别为0.03~0.30 μg/kg和0.10~1.00 μg/kg。对不同样品基质进行0.5、1.0、3.0 μg/kg3个水平的加标回收试验,9种N-亚硝胺类化合物的回收率为80.4%~98.5%, RSD(n=6)为2.41%~12.50%。应用建立的方法检测市面上常见的动物源性食品,除N-亚硝基乙胺、N-亚硝基吗啡胆碱外,其他7种N-亚硝胺类化合物均有不同程度检出。检测结果表明,腌制水产品中N-亚硝胺类化合物含量普遍高于其他样品。研究建立的方法操作简单,不需要长时间蒸馏提取,可快速对动物源性食品中N-亚硝胺类化合物进行定性和定量分析,且样品和试剂的消耗量更少,节省成本,对环境污染小。该法的建立对我国动物源性食品中N-亚硝胺类化合物残留水平的控制、检测标准的制定和采取相应的管理措施具有一定的理论和现实意义。