Jiannong Ye

Immobilization of single-stranded deoxyribonucleic acid on gold electrode with self-assembled aminoethanethiol monolayer for DNA electrochemical sensor applications

A synthesized 24-mer single-stranded deoxyribonucleic acid (ssDNA) was covalently immobilized onto a self-assembled aminoethanethiol monolayer modified gold electrode, using water-soluble 1-ethyl-3(3-dimethylaminopropyl)-carbodiimide (EDC). The covalently immobilized ssDNAs were hybridized with complementary ssDNA (cDNA) or yAL(3) gene in solution, forming double-stranded DNAs (dsDNA). Meanwhile, daunomycin as an electrochemical active intercalator in the hybridization buffer solution was intercalated into the dsDNA to form a dsDNA/daunomycin system on the gold electrode surface, which was used for DNA electrochemical sensor. The cathodic waves of daunomycin bound to the double-stranded DNA (dsDNA) by linear sweep voltammetry were utilized to detect the cDNA. The cathodic peak current (i(pc)) of duanomycin was linearly related to the concentrations of cDNA between 0.1 mug ml(-1) and 0.1 ng ml(-1). The detection limit was about 30 pg ml(-1).

Determination of baicalein, baicalin and quercetin in Scutellariae Radix and its preparations by capillary electrophoresis with electrochemical detection

A method based on capillary electrophoresis with electrochemical detection (CE-ED) was developed for the determination of baicalein, baicalin and quercetin in Scutellariae Radix and its pharmaceutical preparations. The effects of some important factors such as the acidity and concentration of running buffer, separation voltage, injection time, and the potential of working electrode were investigated to acquire the optimum condition. The working electrode was a 300-mum diameter carbon disc electrode positioned opposite the outlet of capillary. The three analytes could be well separated within 12 min in a 40 cm length capillary at the separation voltage of 12 kV in a 100 mmol l(-1) borate buffer (pH 9.0). The response was linear over three orders of magnitude with detection limits (S/N=3) ranged from 0.224 to 0.548 mumol l(-1) for all three analytes. This proposed method demonstrated good long-term stability and reproducibility with R.S.D. of less than 5% for both migration time and peak current (n=7). It has been successfully applied to analyze the actual samples with satisfactory assay results.

Determination of active ingredients of Rhododendron dauricum L. by capillary electrophoresis with electrochemical detection

High-performance capillary electrophoresis with electrochemical detection was employed to analyse active ingredients of Rhododendron dauricum L., an important crude herb frequently used in Chinese medicines. Farrerol, quercetin, syringic acid, vanillic acid, 4-hydroxybenzoic acid, protocatechuic acid are major important active ingredients. Operated in a wall-jet configuration, a 300-microm diameter carbon-disk electrode was used as the working electrode, which exhibits a good response at +950 mV (vs. saturated calomel electrodes) for six analytes. Under the optimum conditions, the analytes were baseline separated within 16 min in a borax buffer (pH 8.7). Notably, excellent linearity was obtained over two orders of magnitude with detection limits (S/N=3) ranged from 9 x 10(-7) to 3.0 x 10(-6) M for all analytes. This method was successfully used in the analysis of Rhododendron dauricum L. with relatively simple extraction procedures, and the assay results were satisfactory.

Determination of trans-Resveratrol in wines, herbs and health food by capillary electrophoresis with electrochemical detection

Abstract A method based on capillary electrophoresis with electrochemical detection (CE–ED) was developed for the determination of trans -Resveratrol in wines, Chinese medicinal herb Polygonum cuspidatum Sied. et Zucc., and Zijin capsule. The effects of some important factors such as injection time, and applied potential to working electrode were investigated. Operated in a wall-jet configuration, a 300 μm diameter carbon-disk electrode was used as the working electrode, which exhibits good response at +0.85 V (vs. SCE) for trans -Resveratrol. Linearity was obtained in the concentration range from 1.0×10 −4 to 5.0×10 −7 g/ml. The detection limit (S/N=3) was 5.96×10 −8 g/ml. This proposed method has been successfully applied to analyze several actual samples with satisfactory assay results.

Voltammetric responsive sensors for organic compounds based on organized self-assembled lipoyl-β-cyclodextrin derivative monolayer on a gold electrode

Abstract Voltammetric responsive sensors based on organized self-assembled β-cyclodextrin derivative monolayers on a gold electrode (β-CD-SME) for electroinactive organic species were studied. Both theoretical considerations and experimental results proved that the reduction in the oxidation peak current of the electroactive marker, ferrocene caboxylic acid, at β-CD-SME was proportional to the concentration of the target molecule and the formation constant of the inclusion complexes with β-CD. The application of the sensor as a detector for ursodeoxycholic and dehydrocholic acids after capillary electrophoresis (CE) separation has been tested. This sensor provides an alternative approach for the detection of electroinactive organic species, and is expected to find application in liquid chromatography (LC) and CE detection.

Determination of the rate constants and activation energy of acetaminophen hydrolysis by capillary electrophoresis.

A method based on capillary electrophoresis with electrochemical detection (CE-ED) was developed for the simultaneous determination of p-aminophenol and acetaminophen in the hydrolysates of acetaminophen. Effects of several important factors such as the acidity and concentration of running buffer, separation voltage, injection time, and working potential were investigated to acquire the optimum conditions. The detection electrode was a 300 microm carbon disc electrode at a working potential of +0.80 V (versus SCE). The two analytes can be well separated within 6 min in a 50 cm length fused silica capillary at a separation voltage of 18 kV in a 25 mM phosphate buffer (pH 6.5). The rate constants of acetaminophen hydrolysis in 0.5 M HCl at different temperatures were determined by monitoring the concentration changes of acetaminophen. At 70, 80, 90 and 100 degrees C, the measured rate constants of acetaminophen hydrolysis were 5.027 x 10(-3), 8.522 x 10(-3), 18.60 x 10(-3) and 32.76 x 10(-3) min(-1), respectively. The activation energy for acetaminophen hydrolysis was calculated to be 68.13 kJ mol(-1), which is in good agreement with the value in the literature.

Sensitive determination of endogenous hexanal and heptanal in urine by hollow-fiber liquid-phase microextraction prior to capillary electrophoresis with amperometric detection.

Hexanal (Hex) and heptanal (Hep) in human blood have been regarded as potential biomarkers of lung cancer. In this work, a hollow-fiber liquid-phase microextraction (HF-LPME) method has been developed for the preconcentration of these trace aldehydes in urine samples. After derivatization with an electroactive compound 2-thiobarbituric acid, these two non-electroactive aldehydes were converted to electroactive adducts, therefore detectable by capillary zone electrophoresis with amperometric detection (CZE-AD) approach. Experimental conditions of derivatization, extraction, electrophoretic separation and detection were optimized. Under the optimum conditions, the enrichment factors for Hex and Hep could reach 320 and 355, respectively. The limits of detection for Hex and Hep were 2.7 and 0.97 nM, respectively; the average recoveries were in the range of 61-95% and relative standard deviation (RSD) values less than 8.5%. The present method has been applied to quantitative analysis of two biomarkers in human urine in lieu of blood samples, and the assay results showed that the contents of Hex (0.99-6.7 μM) and Hep (2.5-6.4 μM) found in the urine sample of the lung cancer patients were significantly higher than those in the healthy volunteers, liver cancer patients, as well as diabetics. The proposed HF-LPME/CZE-AD method may provide a potential alternative for early non-invasive diagnosis of lung cancer disease.

A novel capillary electrophoretic method for determining methylglyoxal and glyoxal in urine and water samples.

Two non-electroactive biomarkers methylglyoxal (MGo) and glyoxal (Go) in urine and environmental water samples were determined for the first time by capillary electrophoresis with amperometric detection (CE-AD) after derivatizing with an electroactive compound 2-thiobarbituric acid. Experimental conditions of derivatization and CE-AD detection were optimized. Highly linear response was obtained for these two biomarkers over three orders of magnitude with good correlation (r(2)>0.999). The limits of detection (LODs) and limits of quantitation (LOQs) of MGo and Go were 0.2microgL(-1) and 1.0microgL(-1), 0.5microgL(-1) and 2.0microgL(-1), respectively. The average recovery and relative standard deviation (RSD) were within the range of 90.9-101.3% and 0.7-2.2%, respectively. The proposed CE-AD method provides a reliable and sensitive quantitative evaluation of MGo and Go in real sample matrices by employing relatively simple and inexpensive instrument.

Electromembrane extraction of salivary polyamines followed by capillary zone electrophoresis with capacitively coupled contactless conductivity detection

Electromembrane extraction (EME) as a novel sample preparation technique was firstly applied for the purification and enrichment of four polyamines mainly present in saliva samples. These four target analytes, putrescine, cadaverine, spermidine, and spermine, were directly determined by CZE with capacitively coupled contactless conductivity detection (CZE-C(4)D) after EME procedure. Several factors affecting extraction efficiency, electrophoretic separation, and detection were investigated. Under the optimum conditions, four polyamines were baseline separated within 22 min, exhibiting a linear calibration over three orders of magnitude (r>0.999); the highest enrichment factor could reach 106-fold (for spermidine), and the LODs were in the range of 1.4-7.0 ng mL(-1). The proposed EME/CZE-C(4)D method has been successfully applied to analyze human saliva samples with recoveries in the range of 78-97%.

Hollow-fiber liquid-phase microextraction combined with capillary electrophoresis for trace analysis of sulfonamide compounds

A hollow-fiber liquid-phase microextraction (HF-LPME) method has been developed for the preconcentration of trace sulfonamides in water samples. Six commonly used sulfonamides including sulfamethazine (SMZ), sulfamerazine (SMR), sulfadiazine (SDZ), sulfadimethoxine (SDM), sulfamethoxazole (SMX), and sulfathiazole (STZ) were determined by CE with electrochemical detection (CE-ED) after microextraction. Several factors that affect extraction efficiency, separation, and detection were investigated. Under the optimum conditions, above sulfonamide compounds could achieve baseline separation within 35min, exhibiting a linear calibration over three orders of magnitude (r(2)≥0.998); the obtained enrichment factors were between 121 (for SDZ) and 996 (for SDM), and the LODs were in the range of 0.033-0.44ng/mL. The proposed HF-LPME/CE-ED method has been applied for the sensitive analyses of the real-world water samples with recoveries in the range of 75.1-109%.