On-chip sample pretreatment using a porous polymer monolithic column for solid-phase microextraction and chemiluminescence determination of catechins in green tea

A porous polymer monolithic column for solid-phase microextraction and chemiluminescence detection was integrated into a simple microfluidic chip for the extraction and determination of catechins in green tea. The porous polymer was prepared by poly(glycidyl methacrylate-co-ethylene dimethacrylate) and modified with ethylenediamine. Catechins can be concentrated in the porous polymer monolithic column and react with potassium permanganate to give chemiluminescence. The microfluidic chip is reusable with high sensitivity and very low reagent consumption. The on-line preconcentration and detection can be realized without an elution step. The enrichment factor was calculated to be about 20 for catechins. The relative chemiluminescence intensity increased linearly with concentration of catechin from 5.0 × 10(-9) to 1.0 × 10(-6) M and the limit of detection was 1.0 × 10(-9) M. The proposed method was applied to determine catechin in green tea. The recoveries are from 90% to 110% which benefits the actual application for green tea samples.     

Fe3+-H2O2-二氯荧光素化学发光体系测定药物中的扑热息痛

酸性介质中,Fe3+催化H2O2分解生成羟基自由基,进而氧化扑热息痛产生微弱的化学发光,二氯荧光素对该发光强度有较强的增敏作用。研究了影响化学发光强度的各种因素,并探讨了其可能的发光机理。在最佳化学发光条件下,其化学发光强度与扑热息痛的浓度在8.0×10-8～5.0×10-5mol/L范围内呈良好的线性关系,检出限为5.0×10-9mol/L,对3.5×10-6mol/L的扑热息痛平行测定9次,其相对标准偏差为2.2%。该法用于片剂中扑热息痛含量的测定,结果满意。     

Fluorescence "Turn-On" chemosensor for the selective detection of beryllium

A new fluorogenic method for selective and sensitive determination of beryllium using 2,6-diphenyl-4-benzo-9-crown-3-pyrane (DBCP) was developed. The proposed fluorescent probe undergoes fluorescent emission intensity enhancement upon binding to beryllium ions in MeOH/H(2)O (70:30, v/v) solution. The fluorescence enhancement of DBCP is attributed to a 1:1 complex formation between DBCP and Be(2+) ion, which has been utilized as the basis for selective detection of Be(2+) ion. With the optimum condition described, the fluorescence enhancement at 531 nm was linear to the concentration of beryllium in the range of 1.6×10(-8)-1.6×10(-7) M and a detection limit of 1.5×10(-9) M. The fluorescent probe exhibits high selectivity for Be(2+) ion over the other common mono, di- and trivalent cations.     

银掺杂聚L-天冬氨酸修饰电极的制备及对肾上腺素的测定

利用循环伏安法,研究了银和L-天冬氨酸在玻碳电极表面电化学聚合的条件,制备了银掺杂聚L-天冬氨酸修饰电极。研究了肾上腺素在修饰电极上的电化学行为,建立了循环伏安法测定肾上腺素的新方法。在pH=3.5的磷酸盐缓冲溶液中,扫描速率为50mV/s时,肾上腺素在修饰电极上产生一对明显的氧化还原峰,峰电位分别为Epa=0.447V,Epc=0.387V。用循环伏安法测定时,氧化峰电流与肾上腺素浓度分别在8.00×10-8～1.00×10-5mol/L和1.00×10-5～1.00×10-4mol/L范围内呈良好的线性关系,检出限为8.0×10-9mol/L。     

利用紫外光离子源高场不对称波形离子迁移谱快速、现场检测水中氨的含量

氨是水体主要的污染物之一,其含量是水质评估的重要参数。本研究采用真空紫外光离子源-高场不对称波形离子迁移谱(Ultraviolet photoionization high field asymmetric waveform ion mobility spectrometry, UVFAIMS)技术,发展一种的水中氨含量的现场快速检测方法。通过对比标准氨样品和水中微量氨UV-FAIMS 谱图峰的特征补偿电压(Compensation voltage, CV)值,确定了水中HN+4的特征离子峰位置;研究了不同分离电压(Dispersion voltages, DV)下HN+4谱图峰位置的关系,获得了HN+4的特征识别系数α2和α4分别为2.21×10-5 Td-2和-1.45323×10-9 Td-4;通过不同浓度样品的信号响应,研究了UV-FAIMS 对水中氨的检出限,在信噪比为3的情况下达到了9.2 μg/ L。本研究为水中氨现场检测提供了一种快速、无需前处理的技术手段。     

Mechanism of H(2) evolution from a photogenerated hydridocobaloxime

Proton transfer from the triplet excited state of brominated naphthol to a difluoroboryl bridged Co(I)-diglyoxime complex, forming Co(III)H, was monitored via transient absorption. The second-order rate constant for Co(III)H formation is in the range (3.5-4.7) × 10(9) M(-1) s(-1), with proton transfer coupled to excited-state deactivation of the photoacid. Co(III)H is subsequently reduced by excess Co(I)-diglyoxime in solution to produce Co(II)H (k(red) = 9.2 × 10(6) M(-1) s(-1)), which is then protonated to yield Co(II)-diglyoxime and H(2).     

顺序注射在线稀释测定人体液中尿酸

基于酸性条件下甲醛对尿酸-KMnO4发光反应的增敏作用,建立了在线稀释顺序注射化学发光联用技术测定人体液中尿酸的新方法。在选定的实验条件下的7个浓度梯度范围内,尿酸浓度在5.0×10-6mol/L~1.0×10-3mol/L范围内与发光强度呈良好线性关系,相关系数0.9942~0.9998,RSD在2.0%~3.5%之间,回收率为98.0%~103.0%。每小时可分析80个样品,在线稀释测定结果与手工稀释法一致。     

A simple fluorescent receptor selective for Mg2+

A structurally simple fluorescent receptor (receptor 1) has been synthesized and was found to show a dramatic enhancement in its fluorescence emission upon complexation with Mg(2+). This was maybe contributed to by the inhibition of the C=N isomerization in the excited state. The experimental results show that the receptor was selective and sensitive towards Mg(2+) in the presence of competing ions, with a low detection limit of 3.5 × 10(-9) mol L(-1) (3σ).     

Amperometric biosensors based on alumina nanoparticles-chitosan-horseradish peroxidase nanobiocomposites for the determination of phenolic compounds

A horseradish peroxidase (HRP) biosensor based on alumina (Al(2)O(3)) nanoparticles-chitosan (CHIT) nanocomposites was developed for the detection of phenolic compounds. UV-Vis spectra and Fourier transform infrared spectra showed that HRP retained its original structure on the Al(2)O(3)/CHIT film. The surface morphologies of the composite films were characterized by scanning electron microscopy. Cyclic voltammetry and amperometry were used to study the proposed electrochemical biosensor. Optimization of the experimental parameters was performed with regard to pH, applied electrode potential and the concentration of hydrogen peroxide. The linear range, sensitivity and detection limit of the biosensor were investigated for eight phenolic compounds. In particular, the linearity of the biosensor for the detection of hydroquinone was obtained from 5 × 10(-9) M to 7 × 10(-5) M with a detection limit of 1 nM (based on the S/N = 3). The optimized biosensor for hydroquinone determination displayed a high sensitivity of 518.4 nA μM(-1) with a response time of ～5 s.     

Electrochemical behavior of o-sec-butylphenol at glassy carbon electrode modified with multiwalled carbon nanotubes and 1-butyl-3-methylimidazolium hexafluorophosphate

A sensitive electrochemical sensor based on immobilized multiwalled carbon nanotubes (MWCNTs) and 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM·PF(6)) on a glassy carbon electrode (GCE) for o-sec-butylphenol (osBP) was proposed. The electro-oxidation behavior was studied, the experimental conditions were optimized and kinetic parameters were calculated. The results indicated that this electrochemical sensor has the advantages of fast electron-transfer rate, minimal fouling of electrodes, high sensitivity and stability for o-sec-butylphenol. Upon comparison with a glassy carbon electrode, this senor would effectively minimize the over-potential and increase the electrochemical response to o-sec-butylphenol. Under the optimum conditions, the peak current was linear to the osBP concentration range from 1 × 10(-7) to 2.5 × 10(-5) M with the detection limit of 8.65 × 10(-9) M (S/N = 3). The proposed method was applied to the determination of spiked water samples with satisfactory results.     

A novel urea amperometric biosensor based on secretion of carnation petal cells modified on a graphite-epoxy composite electrode

A new kind of biosensor for the detection of urea with a high selectivity, sensitivity and wide detection range was designed based on the secretion of carnation petals cells paste covered over a graphite-epoxy composite basic electrode surface. The carnation petal paste from mashed fresh carnation petals was tightly fixed on the basic electrode surface with Teflon thin film to keep it in contact with the electrode surface. Urea in aqueous solution was detected by differential pulse voltammetry based on the oxidation peak current at 0.316 V (vs. SCE) of the secreted species of carnation petal cells during the mashing process, which interacts with urea molecules and results in the decrease of the oxidation peak current. The oxidation peak current decreases linearly with the logarithm of urea concentration in the range of 1.3 × 10(-16)-4.57 × 10(-8) M and 3.4 × 10(-7)-1.3 × 10(-1) M with a detection limit of 7.5 × 10(-16) M. The biosensor was characterized by electrochemistry and fluorescent spectrometry, and applied to the determination of urea in waste water from a river around Shenyang Normal University campus with a recovery of 104.5% (RSD is 5.00%). The presence of larger amounts of ammonium ion and nitrate ion up to the molar ratio of 10(4) do not interfere with the urea detection.     

Potentiometric flow injection system for determination of reductants using a polymeric membrane permanganate ion-selective electrode based on current-controlled reagent delivery

A polymeric membrane permanganate-selective electrode has been developed as a current-controlled reagent release system for potentiometric detection of reductants in flow injection analysis. By applying an external current, diffusion of permanganate ions across the polymeric membrane can be controlled precisely. The permanganate ions released at the sample-membrane interface from the inner filling solution of the electrode are consumed by reaction with a reductant in the sample solution thus changing the measured membrane potential, by which the reductant can be sensed potentiometrically. Ascorbate, dopamine and norepinephrine have been employed as the model reductants. Under the optimized conditions, the potential peak heights are proportional to the reductant concentrations in the ranges of 1.0×10(-5) to 2.5×10(-7)M for ascorbate, of 1.0×10(-5) to 5.0×10(-7)M for dopamine, and of 1.0×10(-5) to 5.0×10(-7)M for norepinephrine, respectively with the corresponding detection limits of 7.8×10(-8), 1.0×10(-7) and 1.0×10(-7)M. The proposed system has been successfully applied to the determination of reductants in pharmaceutical preparations and vegetables, and the results agree well with those of iodimetric analysis.     

A novel ion selective sensor for promethium determination

This is a first promethium(145) ion-selective sensor based on the comparative study of two Schiff base ligands (X(1) and X(2)) as neutral ionophores. Effect of various plasticizers: 2-nitrophenyloctylether (o-NPOE), dibutyl phosphonate (DBP), dioctylphthalate (DOP), tri-(2-ethylhexyl) phosphate (TEHP), dibutyl butylphosphonate (DBBP), chloronaphthalene (CN) and anion excluders: potassium tetrakis (p-chloropheny1) borate (KTpClPB), sodiumtetraphenylborate (NaTPB) and oleic acid (OA) have been studied. The membrane with a composition of ionophore (X(1)/X(2)):KTpClPB:PVC:o-NPOE (w/w, %) in the ratio of 5:5:30:60 exhibited best performance. The best responsive membrane sensors (8 and 21) exhibited working concentration range of 4.5×10(-7)-1.0×10(-2) M and 3.5×10(-6)-1.0×10(-2) M with a detection limits of 3.2×10(-7) M and 2.3×10(-6) M and Nernstian slopes of 20.0±0.5, 19.5±0.5 mV decade(-1) of activity, respectively. The sensor no. 8 works satisfactorily in partially non-aqueous media up to 10% (v/v) content of methanol, ethanol and acetonitrile. Analytical application of the proposed sensor has been demonstrated in determination of promethium (III) ions in spiked water samples.     

A sensitive fluorimetric biosensor for detection of DNA hybridization based on Fe/Au core/shell nanoparticles

In this study, we reported a sensitive fluorescent biosensor for detection of DNA hybridization based on Fe/Au core/shell (Fe@Au) nanoparticles (NPs). First, Fe@Au NPs were synthesized using a reverse micelle method, with gold as the shell and iron as the core. The nanoparticle size was confirmed by transmission electron microscopy (TEM). Scanning electron microscopy (SEM) was performed in order to elucidate the morphology of the Fe@Au NPs. Then probe DNA with -SH at the 5'-phosphate end was covalently immobilized onto the surface of the Fe@Au NPs. The DNA hybridization event can be detected by a fluorescent method and methylene blue (MB) as the fluorescent probe. The decline of the fluorescence intensity of MB (ΔF) was linear with the concentration of the complementary DNA from 3.0 × 10(-13) to 1.0 × 10(-9) M with a detection limit of 1.0 × 10(-13) M (S/N = 3). In addition, this approach of DNA detection exhibited excellent selectivity, even for single-mismatched DNA detection.     

壳聚糖/Nafion膜固定氯化血红素制备过氧化氢生物传感器

以壳聚糖/Nafion复合膜为载体在玻碳电极上固定氯化血红素制备过氧化氢生物传感器。研究了血红素电极制备过程中的影响因素及其电化学性质,在1.0 mol/L pH 9.8的NH3-NH4Cl缓冲溶液中,血红素电极对H2O2的催化还原峰电流与H2O2浓度在7.5×10-5~1.45×10-3mol/L范围内成良好的线性关系,检测灵敏度为35.28μA/mM,检测限为3.5×10-5mol/L(S/N=3),同时研究了血红素电极的重现性、稳定性和选择性。     

流动注射阻抑化学发光法测定环境水中的酚

A new flow injection chemiluminesenet method was presented for the determination of phenol based on the inhibition effect of trace phenol on the chemiluminescence reaction between luminol and N-chlorosuccinimide system.The linear range for the determination of phenol is 1.5×10~(-5)~3.5×10~(-4)mg/mL,the detection limit is 2.36×10~(-6)mg/mL.This method has been used for the determination of phenol in water samples with satisfactory results.The mechanism of the inhibitory reaction was also discussed.     

Ferric ion immobilized on three-dimensional nanoporous gold films modified with self-assembled monolayers for electrochemical detection of hydrogen peroxide

A fast, simple square wave potential method is developed for the fabrication of a three-dimensional (3D) nanoporous gold (NPG) film. The nanostructures are characterized and confirmed by scanning electronic microscopy (SEM) and cyclic voltammetry (CV). The nanostructures modified with self-assembled monolayers (SAMs) are employed as an electrode substrate to immobilize inorganic iron(III) ion. After immobilization, iron(III) ion undergoes an effective direct electron transfer reaction with a pair of well-defined redox peak at -256 ± 10 mV (pH 7.0). The iron(III) ion modified electrode displays the excellent electrocatalytic performance for reduction of hydrogen peroxide, and thus can be used as an electrochemical sensor for detecting hydrogen peroxide with a low detection limit (1.0 × 10(-9) M), a wide linear range (9.0 × 10(-7)~5.0 × 10(-4) M), as well as good stability, selectivity and reproducibility.     

Determination of melamine based on electrochemiluminescence of Ru(bpy)3(2+) at bare and single-wall carbon nanotube modified glassy carbon electrodes

The electrochemiluminescence (ECL) of Ru(bpy)(3)(2+) at bare and single-wall carbon nanotube (SWNT) modified glassy carbon (GC) electrodes has been employed for the determination of melamine for the first time, giving a linear response (R(2) = 0.99682) for melamine concentration from 1.0 × 10(-10) to 1.0 × 10(-5) M at a bare GC electrode in pH 10 borate buffer, and the detection limit is 1.0 × 10(-10) M. However, the detection limit can be reduced further to 1.0 × 10(-13) M after modification of the GC electrode by SWNTs. This is much lower compared to other detection methods. The proposed method was applied to the determination of melamine added to a commercial milk sample; the recovery is quite satisfactory with good reproducibility and stability. All of these results provide the possibility of developing a novel ECL detection method for melamine.     

Determination of azide in gastric fluid and urine by flow-injection electrospray ionization tandem mass spectrometry

A rapid method was developed to identify and quantify the azide ion (N(3)(-)) in gastric fluid and urine. N(3)(-) in diluted biological fluids was reacted with NaAuCl(4) to produce Au(N(3))(2)(-), which was extracted with octanol. Five microliters of the extract were flow-injected into an electrospray ionization tandem mass spectrometric instrument. Quantification of N(3)(-) was performed by selected reaction monitoring of the product ion Au(N)(N(3))(-) at m/z 253, which was derived from the precursor ion Au(N(3))(2)(-) at m/z 281, using 50 μL of aqueous solution within 10 min. This method was found to be linear up to 10(-5) M, to have a limit of quantification of 10(-7) M, a limit of detection of 3.0?×?10(-8) M, and a coefficient of variation of ≦10% at 10(-7) M. In the case of urine, 50 μL of urine were spiked with N(3)(-), this was diluted 10-fold and passed through 1 mL of a resin, and finally diluted to 100-fold of the original. This method was linear up to 10(-3) M, had a limit of quantification of 10(-5) M, a limit of detection of 3.0?×?10(-6) M, and coefficient of variation of ≦8.8% for an original urine concentration of 10(-5) M. The practical applicability of this method was checked by diluting 1 μL of a suspected suicide victim's gastric fluid 20,000-fold and 1 μL of the victim's urine 5,000-fold and then measuring the N(3)(-) levels. These levels were found to be (7.5?±?1.0)?×?10(-2) M and (3.2?±?0.4)?×?10(-3) M, respectively.     

Highly sensitive and selective dopamine biosensor based on a phenylethynyl ferrocene/graphene nanocomposite modified electrode

A new ferrocene derivative (1-[(4-amino) phenylethynyl]ferrocene, Fc-NH(2)) was synthesized for the first time. The ferrocene derivative molecule contained the phenylethynyl skeleton, ferrocene and amino groups with excellent electrochemical properties. The graphene/Fc-NH(2) nanocomposite was prepared by mixing graphene solution and Fc-NH(2) solution in one pot and the nanocomposite was utilized to construct a Nafion/graphene/Fc-NH(2) modified glassy carbon electrode (GCE). The ferrocene derivative immobilized on the graphene can enhance the charge-transport ability of the nanocomposite, stabilize the graphene and prevent the leakage of ferrocene. The detection signal of dopamine (DA) was significantly amplified on the Nafion/graphene/Fc-NH(2)/GCE. It was experimentally demonstrated that the signal enhancement results from the synergy amplification effect of graphene and the Fc-NH(2). The oxidation peak currents of DA were linearly related to the concentrations in the range of 5 × 10(-8) to 2 × 10(-4) M with the detection limit of 20 nM in the absence of uric acid (UA) and ascorbic acid (AA). In the presence of 10(-3) M AA and 10(-4) M UA, the linear response range was 1 × 10(-7) to 4 × 10(-4) M, and the detection limit was 50 nM at S/N = 3. Using the proposed Nafion/Fc-NH(2)/graphene/GCE, DA was successfully determined in real samples with the standard addition method.