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A simple preparation scheme is described for the quantitative analysis of a magnesium niobate sample using slurry introduction axially viewed inductively coupled plasma optical emission spectrometry. Relationships between the stability of slurries and the conditions, such as particle size, pH, dispersant and amount of dispersant, were investigated experimentally. The MgNb2O6 slurry sample was prepared by adding the dispersant sodium polyacrylate and agitation in an ultrasonic bath to ensure good dispersion. Under optimization of pH and amount of dispersant, an analysis of minor and trace impurities (Ba, Ca, Cr, Cu, Fe, Mn, Ni, Pb) in magnesium niobate was accomplished. Applying a paired t test, we showed that the results were in agreement at a 95% confidence level with the reference values obtained by a fusion method for a magnesium niobate sample, which verified that the calibration curves could be established by aqueous standards. Analytical results demonstrate that the factors that affected the accuracy of determination for MgNb2O6 are mainly the particle size of the sample and the stability of slurry. [ABSTRACT FROM AUTHOR]

Abstract: An ultrasensitive and highly specific electrochemical aptasensor for detection of thrombin based on gold nanoparticles and thiocyanuric acid is presented. For this proposed aptasensor, aptamerI was immobilized on the magnetic nanoparticles, aptamerII was labeled with gold nanoparticles. The magnetic nanoparticle was used for separation and collection, and gold nanoparticle offered excellent electrochemical signal transduction. Through the specific recognition for thrombin, a sandwich format of magnetic nanoparticle/thrombin/gold nanoparticle was fabricated, and the signal amplification was further implemented by forming network-like thiocyanuric acid/gold nanoparticles. A significant sensitivity enhancement had been obtained, and the detection limit was down to 7.82aM. The presence of other proteins such as BSA and lysozyme did not affect the detection of thrombin, which indicates a high specificity of thrombin detection could be achieved. This electrochemical aptasensor is expected to have wide applications in protein monitoring and disease diagnosis. [Copyright &y& Elsevier]

Abstract: A sensitive and selective aptasensor using tri(2,2′-bipyridyl)ruthenium(II)-doped silica nanoparticles (Ru(bpy)3 2+-doped SNPs) as DNA tags for detection of thrombin is developed based on the target protein-induced strand displacement of the DNA probe. For the proposed aptasensor, the aptamer was assembled on the surface of the Au electrode through Au-S binding. The hybridization event between the DNA probe labeled by the Ru(bpy)3 2+-doped SNPs and the aptamer was evaluated by electrogenerated chemiluminescence (ECL) measurements. Then, the DNA probe was displaced by thrombin and the binding event between the thrombin and the aptamer was monitored by ECL measurements again. The difference of ECL intensity (ΔI ECL) of the two events could be used to quantify the thrombin. Other proteins, such as bovine serum albumin and bovine hemoglobin, had almost negligible ΔI ECL. Under the optimal conditions, the ΔI ECL was linearly related to the concentration of the thrombin in the range of 10fM to 10pM and the detection limit was down to 1.0fM since SNPs containing a large number of Ru(bpy)3 2+ molecules were labeled on the DNA probe. [Copyright &y& Elsevier]

Abstract: In this paper, a kind of novel carbon paste electrode modified with double modifiers—polyethylene glycol (PEG) and Cu2O (PEG/Cu2O CPME) in capillary zone electrophoresis with amperometric detection (CZE-AD) was applied to simultaneously determine three sugars: glucose, sucrose, fructose and ascorbic acid (AA). The catalytic electrochemical properties of PEG/Cu2O CPME could enhance sensitivity obviously compared with carbon paste electrode modified with only PEG or Cu2O at a relatively lower detection potential (+0.3V versus SCE). Especially, the electrochemical detection response of AA increased obviously to the same level of saccharides by adding PEG into the Cu2O carbon paste modified electrode. The four analytes could be perfectly separated within 22min, the linear ranges were from 1.0×10−6 to 5.0×10−5 molL−1 and the detection limits were at 10−7 molL−1 magnitude (S/N=3). The present working electrode was successfully employed to analyse beverage samples with recoveries in the range 93–107% and RSDs less than 4%. Above results demonstrated that capillary zone electrophoresis coupled with the PEG/Cu2O carbon paste modified electrode was of convenient preparation, high sensitivity, good repeatability and could be used in the rapid determination of practical samples. [Copyright &y& Elsevier]

Abstract: A sensitive electrogenerated chemiluminescence (ECL) detection of DNA hybridization, based on tris(2,2′-bipyridyl)ruthenium(II)-doped silica nanoparticles (Ru(bpy)3 2+-doped SNPs) as DNA tags, is described. In this protocol, Ru(bpy)3 2+-doped SNPs was used for DNA labeling with trimethoxysilylpropydiethylenetriamine(DETA) and glutaraldehyde as linking agents. The Ru(bpy)3 2+-doped SNPs labeled DNA probe was hybridized with target DNA immobilized on the surface of polypyrrole (PPy) modified Pt electrode. The hybridization events were evaluated by ECL measurements and only the complementary sequence could form a double-stranded DNA (dsDNA) with DNA probe and give strong ECL signals. A three-base mismatch sequence and a non-complementary sequence had almost negligible responses. Due to the large number of Ru(bpy)3 2+ molecules inside SNPs, the assay allows detection at levels as low as 1.0×10−13 moll−1 of the target DNA. The intensity of ECL was linearly related to the concentration of the complementary sequence in the range of 2.0×10−13 to 2.0×10−9 moll−1. [Copyright &y& Elsevier]

Abstract: In this paper, a simple, rapid and sensitive flow-injection chemiluminescence method has been developed for the determination of metoprolol tartrate, which acts as a kind of sensitizer in the chemiluminescence emission from the redox of SO3 2− with Ce(IV) in acidic medium. Under the optimized conditions, the proposed method allows the measurement of metoprolol tartrate over the range of 1.5×10−8 to 7.3×10−6 mol/L with a detection limit of 4.7×10−9 mol/L (3σ), and the relative standard deviation for 7.3×10−7 mol/L metoprolol tartrate (n =11) is 2.20%. The utility of this method was demonstrated by determining metoprolol tartrate in tablets and human urine sample. [Copyright &y& Elsevier]

Abstract: A method based on capillary electrophoresis with electrochemical detection has been developed for the separation and determination of isovanillic acid, gentisic acid, kaempferol, quercetin, caffeic acid and protocatechuic acid in Ilex Purpurea Hassk and its medicinal preparations for the first time. The effects of working electrode potential, pH and concentration of running buffer, separation voltage and injection time on CE-ED were investigated. Under the optimum conditions, the analytes could be separated in a 50mmoll−1 borate buffer (pH 9.0) within 21min. A 300μm diameter carbon disk electrode has a good response at +0.95V (versus SCE) for all analytes. The response was linear over three orders of magnitude with detection limits (S/N =3) ranging from 3×10−8 to 2×10−7 gml−1 for the analytes. The method has been successfully applied to the analysis of real sample, with satisfactory results. [Copyright &y& Elsevier]

Abstract: A simple, reliable and reproducible method, based on capillary zone electrophoresis with amperometric detection (CZE-AD), was developed for simultaneous determination of 3-amino-3-azabicyclo[3,3,0]octane (aminoheterocycle) and 3-azabicyclo[3,3,0]octane (azabicycle) in gliclazide bulk drug. The optimal conditions of CZE-AD were 50mM borate solution (pH 9.0) as running buffer, 14kV as separation voltage and 0.95V (versus SCE) as detection potential. Under the selected optimum conditions, the two analytes could be perfectly separated within 9min. The linearity range of aminoheterocycle was from 1.0×10−6 to 1.0×10−3 M and that of azabicycle was from 2.0×10−6 to 1.0×10−3 M. Their detection limits were 5.0×10−7 and 1.0×10−6 M, respectively, (S/N=3). This proposed method demonstrated long-term stability and reproducibility with relative standard deviations of less than 2% for both migration time and peak current. It has been successively used for the determination of these two analytes in gliclazide bulk drug, and the assay results were satisfactory. [Copyright &y& Elsevier]

Abstract: Platinum nanoparticles were used in combination with multi-walled carbon nanotubes (MWCNTs) for fabricating sensitivity-enhanced electrochemical DNA biosensor. Multi-walled carbon nanotubes and platinum nanoparticles were dispersed in Nafion, which were used to fabricate the modification of the glassy carbon electrode (GCE) surface. Oligonucleotides with amino groups at the 5′ end were covalently linked onto carboxylic groups of MWCNTs on the electrode. The hybridization events were monitored by differential pulse voltammetry (DPV) measurement of the intercalated daunomycin. Due to the ability of carbon nanotubes to promote electron-transfer reactions, the high catalytic activities of platinum nanoparticles for chemical reactions, the sensitivity of presented electrochemical DNA biosensors was remarkably improved. The detection limit of the method for target DNA was 1.0×10−11 moll−1. [Copyright &y& Elsevier]

Abstract: A rapid and sensitive flow-injection chemiluminescence method is described for the determination of meloxicam based on its reaction with N-bromosuccinimide (NBS) in alkaline medium. Under the optimum conditions, the proposed method allows the measurement of meloxicam over the range of 2.2×10−7 to 2.8×10−5 mol/l with a detection limit of 7.7×10−8 mol/l. The relative standard deviation for 11 parallel measurements of 2.8×10−6 mol/l meloxicam is 2.14%. The method has been applied satisfactorily to the determination of meloxicam in pharmaceutical preparations. The results agree well with those obtained by spectrophotometry. The mechanism of the chemiluminescence reaction is briefly explained with spectroscopic evidence. [Copyright &y& Elsevier]

Abstract: It was found that the weak chemiluminescence produced from the reaction of dobutamine hydrochloride with luminol in alkaline solution could be strongly enhanced by potassium ferricyanide and potassium ferrocyanide. Based on this found, a new flow injection chemiluminescence method is proposed for the determination of dobutamine hydrochloride. Under the optimum conditions, the proposed method has a linear range of 1.0×10−10 to 1.0×10−7 gml−1, with a detection limit of 2.6×10−11 gml−1 for dobutamine hydrochloride (3σ). A complete analysis could be performed in 40s including washing and sampling, giving a throughout of about 90h−1. The relative standard deviation (R.S.D.) for 11 parallel measurements of 1.0×10−8 gml−1 dobutamine is 1.23%. The proposed method has been applied for the determination of dobutamine hydrochloride in its pharmaceutical formulations. The results obtained compared well with those by an official method. The possible mechanism of this chemiluminescence reaction was also proposed. [Copyright &y& Elsevier]

Abstract: In this paper, the electrochemical behavior of luminol in weakly acidic solution was studied. It is found that Co2+ remarkably enhances the electrochemiluminescence (ECL) of luminol in citric acid–sodium citrate buffer solution (pH=4.0) when a pulse potential (−1.8 to +1.0V, versus Ag/AgCl) is applied to the Pt electrode. The selectivity for Co2+ is very good because most of the other water-soluble metal ions do not interfere. A sensitive and selective ECL method for determination of Co2+ is proposed. After optimization of the reaction conditions and electrochemical parameters influencing the relative ECL intensity, the linear range responding to Co2+ is 5.0×10−12 to 1.0×10−7 mol/L, and the detection limit is 2.0×10−12 mol/L. The relative standard deviation for 5.0×10−10 mol/L cobalt(II) is 3.7% (n =11). [Copyright &y& Elsevier]

Abstract: A novel sensitive electrochemical biosensor based on magnetite nanoparticle for monitoring DNA hybridization by using MWNT–COOH/ppy-modified glassy carbon electrode is described. In this new detection system, mercapatoacetic acid (RSH)-coated magnetite nanoparticles, capped with 5′-(NH2) oligonucleotide, is used as DNA probe to complex 29-base polynucleotide target (a piece of human porphobilinogen deaminase PBGD promoter from 170 to 142). Target sequence hybridized with the probe results in the decrease of the reduction peak current of daunomycin connected with probe. The response of non-complementary sequence was almost the same as the blank, and the response of three-base mismatched sequence within 29-base polynucleotide was obviously distinguished from complementary sequence, which can easily identify point mutation of DNA. The equation of calibration plot is ip (μA)=0.8255-0.0847ctarget oligonucleotide×1013 in the range of 6.9×10-14 to 8.6×10-13mol/L, and correlation coefficient is 0.9974. The detective limit is 2.3×10-14mol/L of target oligonucleotide. This device can be optimized for the detection of complex sequence. [Copyright &y& Elsevier]

A simple, reliable and reproducible method, based on capillary zone electrophoresis with amperometric detection (CZE-AD), has been developed for simultaneous determination of five active ingredients in complicated traditional Chinese medicines including chlorogenic acid, caffeic acid, aloe-emodin, emodin and rhein. A carbon-disk electrode was used as working electrode. The optimal conditions of CZE detection were 30 mM borate solution (pH 9.5) as running buffer, 18 kV as separation voltage and 1.00 V (versus Ag/AgCl) as detection potential. There was excellent linearity between current response and analyte concentration over two orders of magnitude, while the limits of detection were 1.1×10-7, 3.0×10-7, 1.5×10-7, 2.9×10-7, 1.4×10-6 mol/l for aloe-emodin, emodin, rhein, chlorogenic acid and caffeic acid, respectively (S/N=3). The utility of this method was demonstrated by monitoring a kind of complicated Chinese medicine named Huangdan Yinchen Keli. Two samples manufactured by different companies were monitored with satisfactory results. [Copyright &y& Elsevier]

A novel electrochemical DNA biosensor based on methylene blue (MB) and zirconia (ZrO2) thin films modified gold electrode for DNA hybridization detection is presented. Zirconia thin films were electrodynamically deposited onto the bare gold electrode in an aqueous electrolyte of ZrOCl2 and KCl by cycling the potential between −1.1 and +0.7 V (versus Ag/AgCl) at a scan rate of 20 mV s−1. Oligonucleotide probes with phosphate group at the 5′ end were attached onto the zirconia thin films because zirconia is affinity for phosphoric group. The surface density of the immobilized DNA molecules at the zirconia interface was investigated by fluorescence spectroscopy method. Hybridization was induced by exposure of the ssDNA-containing Au electrode to complementary ssDNA in solution. The decreases in the peak currents of MB, an electroactive label, were observed upon hybridization of probe with the target. The cathodic peak current (ip) of MB after hybridization with the target DNA was linearly related to the logarithmic value of the target DNA concentration ranging from 2.25×10−10 to 2.25×10−8 mol l−1. A detection limit of 1.0×10−10 mol l−1 of oligonucleotides can be estimated. [Copyright &y& Elsevier]

Hydroxyl radical (OH⋅) can cause severe damage to cells and tissues. However, its analysis is very difficult for its high reactivity and very short half-life. In this paper, a simple and highly sensitive method, capillary zone electrophoresis with amperometric detection (CZE-AD) was introduced indirectly to determine OH⋅ by determining its reaction products with salicylic acid (SAL), 2,3-dihydroxybenzoic acid (2,3-DHBA) and 2,5-dihydroxybenzoic acid (2,5-DHBA). The optimum conditions of CZE-AD for the determination of 2,3-DHBA and 2,5-DHBA were explored. Under the optimum conditions, SAL, 2,3-DHBA and 2,5-DHBA could be perfectly separated within 15 min, and the linearity ranges of 2,3-DHBA and 2,5-DHBA were between 1.0×10−7 and 1.0×10−4 mol l−1. Their detection limits were as low as 2×10−8 mol l−1, which were much lower than that in CE-UV method. The method was also applied to study the free OH⋅ scavenging activity of angelica polysaccharide. The experimental results showed that this CZE-AD method was very sensitive and practical in both the determination of free OH⋅ and the evaluation of free OH⋅ scavenging activities of antioxidants. [Copyright &y& Elsevier]

A new and sensitive electrochemical DNA hybridization detection assay, using tris(2,2′-bipyridyl)cobalt(III) [Co(bpy)33+]-doped silica nanoparticles as the oligonucleotide (ODN) labeling tag, and based on voltammetric detection of Co(bpy)33+ inside silica nanoparticles, is described. Electro-active Co(bpy)33+ is not possible for directly linking with DNA, it is doped into the silica nanoparticles in the process of nanoparticles synthesis for DNA labeling with trimethoxysilylpropydiethylenetriamine (DETA) and glutaraldehyde as linking agents. The Co(bpy)33+ labeled DNA probe is used to hybridize with target DNA immobilized on the surface of glassy carbon electrode. Only the complementary sequence DNA (cDNA) could form a double-stranded DNA (dsDNA) with the DNA probe labeled with Co(bpy)33+ and give an obvious electrochemical response. A three-base mismatch sequence and non-complementary sequence had negligible response. Due to the large number of Co(bpy)33+ molecules inside silica nanoparticles linked to oligonucleotide DNA probe, the assay showed a high sensitivity. It allows the detection at levels as low as 2.0×10−10 mol l−1 of the target oligonucleotides. [Copyright &y& Elsevier]

Although daunorubicin, pharmorubicin and idarubicin are important drugs in medical and in pharmaceutical research, the dissociation constants (Ka) of these substances are frequently not known. A method based on a non-linear model enabling the efficient determination of the Ka of the three drugs by capillary zone electrophoresis with amperometric detection (CZE-AD) has been demonstrated. The pKa values obtained through the method were in agreement with the values by typical spectrophotometric method. [Copyright &y& Elsevier]

In this paper, capillary zone electrophoresis with amperometric detection was firstly applied to indirectly determine the composition of Chinese ligustrum lucidum polysaccharide (LLPS) by analyzing its hydrolyzates: fucose, glucose, arabinose and rhamnose. Under the selected optimum conditions, the four monosaccharides could be perfectly separated within 30 min and showed significant current responses at the copper electrode. The linear ranges of fucose, glucose and arabinose were all from 5.0×10−6 to 1.0×10−4 mol l−1 and that of rhamnose was from 1.0×10−5 to 1.0×10−4 mol l−1, and their detection limits were lower or near 1.0×10−6 mol l−1 (S/N=3). Experiments showed that the mole ratio of fucose, glucose, arabinose and rhamnose in Chinese LLPS was 1.80:4.58:2.55:1.91, and the purity of this polysaccharide leached by the introduced leaching method was 93.3%. Analyzing polysaccharide by this method has some merits of quickness, low-volume sampling, simple instrument, high sensitivity and high reproducibility. [Copyright &y& Elsevier]

In this paper, capillary zone electrophoresis with amperometric detection (CZE-AD) was firstly applied to the simultaneous determination of rutin (RT) and hydrochlorothiazide (HCT) in compound Chinese herb medicines and human urine samples. The two analytes could be perfectly analyzed within 12 min and showed significant current responses at carbon electrode under the optimum conditions. It was found that the linear range of HCT was from 2.0×10−6 to 1.0×10−4 mol l−1 and that of RT was from 1.0×10−6 to 1.0×10−4 mol l−1. Their sensitivity was determined by linear regression and calculated as 7.02×104 and 2.17×105 nA l mol−1, respectively, and their detection limits were 5.0×10−7 and 2.0×10−7 mol l−1, respectively (S/N=3). Above results demonstrated that this method was of high sensitivity, good repeatability, high selectivity and could be used in metabolic kinetics studies of medicines. Satisfactory results were obtained when this method was used to simultaneously analyze the amounts of RT and HCT in one general compound Chinese herb medicine—Zhen Ju jiang Ya Pian and human urine samples. [Copyright &y& Elsevier]

A simple, fast and reliable method, based on capillary zone electrophoresis with amperometric detection, for the separation and determination of sucrose, glucose, and fructose in Chinese traditional drugs, namely Astragalus Membranceus (Fish.) Bge, Angelica and Codonopsis pilosula (Franch.) Nannf. was described in this paper. A copper disk electrode was used as working electrode. The optimal conditions of separation and detection were 0.05 mol/l sodium hydroxide buffer (pH 12.7), 5 kV for the separation voltage and +0.65 V (vs. Ag/AgCl) for the detection potential. The linear ranges were from 5.0×10−6 to 5.0×10−4 mol/l for all three sugars. The all regression coefficients were more than 0.999. The detection limits were 1.0×10−6 mol/l for glucose and fructose, and 4.0×10−6 mol/l for sucrose. The method built in this paper was directly applied to the separation and determination of the three sugars in three Chinese traditional drugs without prior derivatization, and the content for every sugar in the drugs was first assayed. The assay results were satisfactory. [Copyright &y& Elsevier]

An electrochemical detection method for analyzing sequence-specific DNA using gold nanoparticle DNA probes and subsequent signal amplification step by silver enhancement is described. The assay relies on the electrostatic adsorption of target oligonucleotides onto the sensing surface of the glassy carbon electrode (GCE) and its hybridization to the gold nanoparticle-labeled oligonucleotides DNA probe. After silver deposition onto gold nanoparticles, binding events between probe and target were monitored by the differential pulse voltammetry (DPV) signal of the large number of silver atoms anchored on the hybrids at the electrode surface. The signal intensity difference permits to distinguish between the match of two perfectly matched DNA strands and the near-perfect match where just one base pair was wrong. Coupled with this ‘nanoparticle-promoted’ reduction of silver signal amplification method, the sensitivity of this electrochemical DNA biosensor has been increased by approximately two orders of magnitude and a detection limit of 50 pM of complementary oligonucleotides was obtained. [Copyright &y& Elsevier]

The amperometric detection of codeine and its metabolite, morphine following capillary zone electrophoretic separation is described. A carbon-disk electrode used as working electrode for two analytes exhibited a good response at 0.90 V (vs. Ag/AgCl). The optimal conditions of separation and detection were pH 8.4 phosphate buffer solution (0.06 mol l−1), 12 kV for the separation voltage, sample injection at 12 kV for 10 s. The linear ranges were from 3.1×10−7 to 2.5×10−5 mol l−1 for codeine and 1.9×10−7 to 1.5×10−5 mol l−1 for morphine with a correlation coefficient of 0.9996 and 0.9999, respectively. The detection limits for codeine and morphine were 1.6×10−7 and 6.8×10−8 mol l−1. The method developed was successfully applied to the determination of codeine and its metabolite, morphine in the human urine without any other sample pretreatment except filtration, and the results were satisfactory. [Copyright &y& Elsevier]

An electrochemiluminescence (ECL)-based method for rapid and sensitive detection of acridinium ester in neutral solution was described. Strong ECL emission was observed when a positive voltage over 2.0 V (versus Ag/AgCl) was applied to the working electrode (Pt) immersed in the acridinium ester solution of 2.0 mol l−1 KNO3 (pH 7.0). The possible ECL mechanism was discussed. It was proposed that the ECL emission came out of N-methylacridone, the oxidization product of acridinium ester by the nascent oxygen generated on the surface of working electrode in the course of oxidization of water. Other influenced factors including the electrochemical parameters, the ECL reaction medium and pH value, were investigated in detail. Under the optimal conditions, ECL intensity has a linear relationship with the concentration of acridinium ester in the range of 0.24–96 ng ml−1 (r=0.9999). The relative standard deviation for 24 ng ml−1 acridinium ester was 4.6% (n=11). The limit of detection was 0.16 ng ml−1. [Copyright &y& Elsevier]

The use of micellar electrokinetic capillary chromatography (MECC) with electrochemical detection is described for the determination of puerarin and daidzein in Puerariae radix and its medicinal preparations. Operated in a wall-jet configuration, a 300 μm diameter carbon-disk electrode was used as the working electrode, which exhibits good responses at +900 mV (versus SCE) for the two analytes. Under the optimum conditions, the analytes were base-line separated within 11 min in a sodium dodecyl sulphate—borax (pH 7.8) running buffer, and excellent linearity was obtained in the concentration range from 5.0×10−4 to 5.0×10−6 mol/l. The detection limit (S/N=3) was 6×10−7 and 1.1×10−6 mol/l for puerarin and daidzein, respectively. This work provides a useful method for the analysis of traditional Chinese medicines. [Copyright &y& Elsevier]

Abstract: The simultaneous determination of four active ingredients in Nao Xue Shuan Tablets, including ferulic acid, protocatechuic aldehyde, caffeic acid and protocatechuic acid was performed by capillary zone electrophoresis with amperometric detection (CZE-AD). The effects of working electrode potential, pH and concentration of running buffer, separation voltage and injection time on CZE-AD were investigated. Under the optimum conditions, the four analytes could be perfectly separated within 18min. A 300μm diameter carbon-disc electrode had a good response at +0.95V (vs. SCE) for the four analytes. The response was linear over three orders of magnitude with detection limits (S/N=3) as low as 10−8 or 10−9 g/mL for the analytes. The assay results were satisfactory with recoveries in the range of 85.2–93.0% and RSDs less than 3.3%. [Copyright &y& Elsevier]

Simultaneous detection of various intracellular biomarkers is promising for early diagnosis and treatment of cancer. Herein, a split primer ligation-triggered catalyzed hairpin assembly-based on dual-signal electrochemical biosensor was constructed for the determination of two pairs of cancer mRNAs: TK1 and c-myc, survivin and GalNAc-T by using ferrocene molecular beacon and hemin molecular beacon as detection signal sources. Each pair of targets exists simultaneously, can release the split primers and ligated as the integral primers, hybridization occurred between the integral primers and part of MBs, causing a double-stranded DNA formed. The probes hybridized with the unfolded MBs and displaced integral primers. Finally, the displaced integral primers again hybridized with the MBs and initiated cycle amplification. Under the optimal conditions, the detection limit of TK1 and c-myc mRNA is as low as 0.022 nM, and that of survivin and GalNAc-T mRNA is 0.029 nM. In addition, two pairs of cancer mRNAs could act as outputs to activate an AND logic gate. Image 1 • We designed a dual-signal electrochemical biosensor for determination of two pairs of cancer mRNAs. • A split primer ligation-triggered catalyzed hairpin assembly method could improve the accuracy and sensitivity. • Our findings can also accurately and rapidly analyze the distinguish cancer cells from their normal cells. [ABSTRACT FROM AUTHOR]

In this work, an on-line preconcentration method of field-enhanced sample injection (FESI) was implemented in the determination of four β 2 -agoinsts terbutaline (TER), procaterol (PRO), formoterol (FOR) and bambuterol (BAM) by capillary electrophoresis coupled with capacitively coupled contactless conductivity detection (CE-C 4 D). Under optimized conditions the background electrolyte (BGE) was 5mM Tris(hydroxymethyl)aminomethane (Tris) and 10mM citric acid (Cit) at a pH of 3.2 while the sample dilution solution was obtained by methanol. The detection limits (defined as S/N=3) of this method were 0.02mg/L for TER, PRO, FOR, BAM, which were much lower than that of the conventional CE-C 4 D method without preconcentration procedure, the enhancement factors were greatly improved to be 30-40-fold. The linearity ranges of four β 2 -agoinsts were 0.1-15mg/L, with good linear correlation coefficients (r 2 >0.9900). In order to evaluate the application potential of the developed method, real sample from pig feed was analyzed with recoveries of 91.4-106.2%., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Based on the catalytic activity of hemin, an efficient biocatalyst, an indirect capillary electrophoresis-chemiluminescence (CE-CL) detection method for phenols using a hemin-luminol-hydrogen peroxide system was developed. Through a series of static injection experiments, hemin was found to perform best in a neutral solution rather than an acidic or alkaline medium. Although halide ions such as Br(-) and F(-) could further enhance the CL signal catalyzed by hemin, it is difficult to apply these conditions to this CE-CL detection system because of the self-polymerization of hemin, as it hinders the CE process. The addition of concentrated ammonium hydroxide to an aqueous/dimethyl sulfoxide solution of hemin-luminol afforded a stable CE-CL baseline. The indirect CE-CL detection of five phenols using this method gave the following limits of detections: 4.8 × 10(-8) mol/L (o-sec-butylphenol), 4.9 × 10(-8) mol/L (o-cresol), 5.4 × 10(-8) mol/L (m-cresol), 5.3 × 10(-8) mol/L (2,4-dichlorophenol) and 7.1 × 10(-8) mol/L (phenol)., (Copyright © 2013 John Wiley & Sons, Ltd.)

Qualitative and quantitative detection of DNA was achieved by a "sandwich" DNA sensor through SG/TC (substrate generation and tip collection) mode of scanning electrochemical microscopy (SECM). The "sandwich" DNA structure was formed by the hybridization of thiol-tethered oligodeoxynucleotide probes (capture probe), assembled on the gold substrate surface, with target DNA and biotinylated indicator probe. HRP (horseradish peroxidase)-wrapped SiO2 nanoparticles were linked to the sandwich structure through biotin-streptavidin interaction. Hydroquinone (H2Q) was oxidized to benzoquinone (BQ) at the modified substrate surface where sequence-specific hybridization had occurred through the HRP-catalyzed reaction in the presence of H2O2. The detection was based on the reduction of BQ generated on the modified substrate by SECM tip. For SECM imaging experiment, we structured the microsensor platform through localized desorption of 1-dodecanethiol monolayer. Approach curves were employed for quantitative detection of DNA concentration. The detection limit of complementary DNA was as low as 0.8pM. This technique is promising for the application on electrochemical DNA chip., (Copyright © 2013 Elsevier B.V. All rights reserved.)

A simple and effective capillary electrophoresis-chemiluminescence (CE-CL) detection system was developed based on an ultra-fast bis(2,4,6-trichlorophenyl)oxalate (TCPO) chemiluminescence (CL) reaction (0.6 s duration) that avoided overlapping peaks and peak tailing. Through a series of static injection experiments, this unusually rapid CL reaction was ascribed to the catalytic effect of imidazole in the tetrahydrofuran solvent, which has been rarely utilized in such investigations. A possible mechanism is given to explain the results. Under the optimized conditions, rhodamine 6 G (R6G) and its hydrolysis product (R6G-COOH) could be efficiently separated through electrophoresis in 7 min, with sensitive CL detection in the proposed CE-CL system. In this way, the alkaline hydrolysis of R6G was monitored, followed by estimation of relative rate constants and activation energy. This finding and application should be helpful in further study for the TCPO CL reaction, and revealed an attractive opportunity for simplifying the CE-CL system, such as in a microchip device., (Copyright © 2011 John Wiley & Sons, Ltd.)

A simple, fast, and reliable method based on capillary electrophoresis with electrochemical detection (CE-ED) was developed for the separation and determination of rutin, ferulic acid, vanillic acid, chlorogenic acid, quercetin and caffeic acid in Radix Astragali and its medicinal preparations. The effects of several important factors, such as detection potential, pH, running buffer concentration, separation voltage and injection time, were investigated to acquire the optimum conditions. Under the optimum conditions, the analytes could be separated within 17 min in a 75 cm length capillary at a separation voltage of 18 kV in a 10 mmol/L borate buffer (pH 8.2). A 300 microm diameter carbon disk electrode generated a good response at +0.95 V (vs. saturated calomel electrode (SCE)) for all analytes. The relationship between peak currents and analyte concentrations was linear over about three orders of magnitude with detection limits (S/N = 3) ranging from 78 microg/L to 110 microg/L for all analytes. The average recoveries were 96.0%-103.0% with the relative standard deviations of 1.9%-3.6% (n=3). This method has been successfully used for the determination of these analytes in real samples, and the assay results were satisfactory.

A new method has been developed for the simultaneous determination of diflubenzuron and triflumuron residues in greasy wool by reversed-phase high performance liquid chromatography (HPLC). The pesticides were extracted by hexane-ether from greasy wool and cleaned up with gel permeation chromatography (GPC) and solid phase extraction (SPE). The pesticides were analyzed by HPLC-diode array detector (DAD) and quantified by external standard method. The linear ranges of diflubenzuron and triflumuron were 0.41 -41 mg/L and 0.38 - 38 mg/L, and the correlation coefficients were 0.999 6 and 0.999 9, respectively. The limits of detection were 0.22 mg/kg for diflubenzuron and 0.18 mg/kg for triflumuron; the limits of quantification were 0.73 mg/kg for diflubenzuron and 0.60 mg/kg for triflumuron. The average recoveries of pesticides spiked levels from 0.76 to 10.25 mg/kg in greasy wool samples were in the range of 86.3% - 96.7%, and the relative standard deviations were 4.2% - 8.7%. The method developed shows little interferences, good recovery and repeatability. It is suitable for the simultaneous determination of diflubenzuron and triflumuron in greasy wool samples.

The simultaneous determination of three isomers of phenylenediamines (o, m, and p-phenylenediamine) and two isomers of dihydroxybenzenes (catechol and resorcinol) in hair dyes was performed by capillary zone electrophoresis coupled with amperometric detection (CZE-AD). The effects of working electrode potential, pH and concentration of running buffer, separation voltage, and injection time on CZE-AD were investigated. Under the optimum conditions the five analytes could be perfectly separated in 0.30 mol L(-1) borate-0.40 mol L(-1) phosphate buffer (pH 5.8) within 15 min. A 300 μm diameter platinum electrode had good responses at +0.85 V (versus SCE) for the five analytes. Their linear ranges were from 1.0 × 10(-6) to 1.0 × 10(-4) mol L(-1) and the detection limits were as low as 10(-7) mol L(-1) (S/N = 3). This working electrode was successfully used to analyze eight kinds of hair dye sample with recoveries in the range 91.0-108.0% and RSDs less than 5.0%. These results demonstrated that capillary zone electrophoresis coupled with electrochemical detection using a platinum working electrode as detector was convenient, highly sensitive, highly repeatable and could be used in the rapid determination of practical samples.

A simple and rapid capillary electrophoresis (CE) with electrcochemical detection (ED) method has been established for the simultaneous determination of seven active ingredients in the stems and roots of Gaultheria leucocarpa var. yunnanensis and its medicinal preparation, including (+)-catechin, rutin, gentisic acid, vallinic acid, salicylic acid, quercetin, and protocatechuic acid. The effects of working potential, pH, and concentration of running buffer, separation voltage, and injection time on CE-ED are systematically investigated. Under the optimum conditions, the seven analytes could be completely separated within 23 min in a borax running buffer (pH 8.7). A good linear relationship is obtained over three orders of magnitude with detection limits (signal-to-noise ratio=3) ranging from 5x10(-8) g/mL to 3x10(-7) g/mL for the analytes. The proposed method is successfully used in the analysis of real samples after a relatively simple extraction procedure, and the assay results are satisfactory.

In this paper, a kind of novel carbon paste electrode modified with double modifiers-polyethylene glycol (PEG) and Cu(2)O (PEG/Cu(2)O CPME) in capillary zone electrophoresis with amperometric detection (CZE-AD) was applied to simultaneously determine three sugars: glucose, sucrose, fructose and ascorbic acid (AA). The catalytic electrochemical properties of PEG/Cu(2)O CPME could enhance sensitivity obviously compared with carbon paste electrode modified with only PEG or Cu(2)O at a relatively lower detection potential (+0.3 V versus SCE). Especially, the electrochemical detection response of AA increased obviously to the same level of saccharides by adding PEG into the Cu(2)O carbon paste modified electrode. The four analytes could be perfectly separated within 22 min, the linear ranges were from 1.0 x 10 (-6) to 5.0 x 10(-5) mol L(-1) and the detection limits were at 10(-7) mol L(-1) magnitude (S/N=3). The present working electrode was successfully employed to analyse beverage samples with recoveries in the range 93-107% and RSDs less than 4%. Above results demonstrated that capillary zone electrophoresis coupled with the PEG/Cu(2)O carbon paste modified electrode was of convenient preparation, high sensitivity, good repeatability and could be used in the rapid determination of practical samples.

For its high reactivity and very short half-life, the hydroxyl radical (OH.) in vivo is very difficult to be detected. Usually, it is indirectly quantified by determining 2,3-dihydroxybenzoic acid (2,3-DHBA) and 2,5-dihydroxybenzoic acid (2,5-DHBA), which are the reaction products of salicylic acid (SA) and OH.. Because 2,5-DHBA could be directly formed by the P(450) enzyme, only 2,3-DHBA is regarded as the real biomarker of OH.in biological studies. But the very low concentration of OH* in human bodies makes its determination very difficult and complicated. In this paper, a simple online stacking capillary zone electrophoresis coupled with amperometric detection (CZE-AD) method was explored to improve the detection sensitivity of 2,3-DHBA to reach the requirements in biological analysis. A mixture solution of 12.5 mmol/L Na(2)B(4)O(7)-25 mmol/L NaH(2)PO(4) (pH 7.9) was used as the running buffer and p-methyl benzoate was selected as a suitable stacker. The effects of the concentration, pH value, and injection time of p-methyl benzoate on stacking efficiency were carefully studied. Under the optimum stacking CZE-AD conditions, the detection sensitivity of 2,3-DHBA was improved about 20-fold and its detection limit reached the 10(-9) mol/L level. The experimental results showed that this was a potential method to determine OH* in vivo.

A high-performance capillary electrophoretic (CE) method with electrochemical detection (ED) has been developed for determination of the pharmacologically active flavonoids in Ginkgo biloba L. and phytopharmaceuticals containing its extract. Epicatechin, catechin, rutin, apigenin, luteolin, and quercetin are important flavonoids in this plant. Operated in a wall-jet configuration, a 300 micro m diameter carbon-disk electrode was used as working electrode with good response to the six analytes at +1000 mV (relative to the SCE). Under the optimum conditions, the analytes were separated within 22 min in a borax buffer (pH 9.0). Excellent linearity was obtained over two orders of magnitude and detection limits (S/N=3) ranged from 1.4 x 10(-7) to 5.0 x 10(-7) g mL(-1) for all six analytes. The method was successfully used for assay of Ginkgo biloba L. and its phytopharmaceuticals after a relatively simple extraction procedure; the results obtained were satisfactory.