Ping Dai

Highly selective molecular recognition and high throughput detection of melamine based on molecularly imprinted sol–gel film

Multimode reader has been generally applied in immunoassay, and in the proposed paper, the 96 well micro-plate was modified with molecularly imprinted melamine sol-gel film, based on which the highly selective and high throughput detection of melamine was achieved. Melamine was imprinted into silica sol-gel films directly using phenyltrimethoxysilane and methyltrimethoxysilane as functionalized organosilicon precursors. The binding characteristic of the imprinted film to melamine was evaluated by equilibrium binding experiments and the morphology was studied by scanning electronic microscope (SEM). Scatchard analysis was carried out to estimate the binding parameters of the imprinted film. The proposed method exhibited excellent selectivity because of specific recognition of MM by molecularly imprinted film. Under the optimum conditions, the chemiluminescence (CL) intensity had a linear relationship against the concentration of melamine over the range of 0.1-50 microg mL(-1) with a lower detection limit of 0.02 microg mL(-1).

A novel enzyme biosensor for glucose based on rhodanine derivative chemiluminescence system and mesoporous hollow silica microspheres receptor.

In this work, hollow silica microspheres (HSMs), which have hollow interiors and nanoporous shells, were used in the immobilization of enzyme to establish a novel chemiluminescence biosensor. The immobilization behavior of enzyme in HSMs with different pore sizes has been studied. The results revealed that the pore size and the surface area of HSMs play important roles in their immobilization performance. Compared with traditional methods, this immobilization method not only provides tunable and consistent pore system and restricted microspaces for enzyme immobilization, but also exhibits a larger immobilization capacity and a higher adsorption rate. A rhodanine derivative-KMnO4-HCl-H2O2 was used to replace traditional chemiluminescence system (luminol-horseradish peroxidase-H2O2) to reach the purpose of high sensitivity, simple operation and pH expansion for chemiluminescence biosensor. The linear range of this novel method is 7.72 x 10(-6) to 2.54 x 10(-2) mol L(-1) (r=0.9994). The detection limit is 8.0 x 10(-7) mol L(-1). The Michaelis-Menten constant of glucose oxidase was 0.3 mmol L(-1). With glucose oxidase as a test enzyme, the proposed method gave an accurate and satisfactory result once applied to the determination of glucose in four different human serum samples.

Facile and scalable synthesis of a novel rigid artificial superoxide dismutase based on modified hollow mesoporous silica microspheres.

A novel metallosalen complex, named Mn-(bis(salicylaldehyde)-3,4-Diaminobenzoic acid), with superoxide scavenging activity was prepared from manganese(III) acetate dehydrate and bis(salicylaldehyde)-3,4-Diaminobenzoic acid in ethanol. We found that the novel complex has a higher superoxide scavenging activity than traditional complex, named n-(bis(salicylaldehyde)ethylenediamine), without the carboxy, the catalytic process was studied and explained. Hollow silica microspheres (HSMs) that mimics superoxide dismutase activity has been developed by using the HSMs modified with the novel metallosalen complex through the esterification between the carboxy and silanol. The property and superoxide dismutase activity of the metallosalen-modified HSMs were investigated. These novel rigid metallosalen-modified HSMs possess excellent superoxide dismutase activity and it can be easily immobilized to fabricate biomimetic sensor or other catalytic unit/receptor, it solves many practical problems such as easy recovery and repeat utilization. An application test of this novel rigid artificial SOD was performed by fabricating a novel biomimetic sensor to determine superoxide based on mesoporous hollow silica microspheres receptor and rhodanine chemiluminescence detector. In addition, the metallosalen can be replaced by other active centers to mimic novel kind of enzymes and immobilized in/on other devices to establish novel biomimetic sensors.

Highly selective determination of phenolphthalein by flow injection chemiluminescence method based on a molecular imprinting polymer

The phenolphthalein-imprinted polymer was prepared with methacrylic acid as functional monomer and ethylene glycol dimethacrylate as cross-linker. Taking advantage of the quenching effect of phenolphthalein on the potassium permanganate-HCl-anhydrous alcohol chemiluminescence system, a new model was established to determine phenolphthalein by a highly selective flow injection chemiluminescence method. The traditional flow-though cell was replaced with a novel flow path using a Y-shaped polymethyl methacrylate column, through which the three reactants were injected simultaneously. The linear range of this assay was from 1.0 x 10(-8) to 1.0 x 10(-6) g/mL (r = 0.9978). The limit of detection was 8.9 x 10(-9) g/mL. The relative standard deviation for the determination of 1.0 x 10(-8) g/mL phenolphthalein solution was below 2.9% (n = 11). The proposed method was applied to the determination of phenolphthalein in real samples with satisfactory results.

Preconcentration and Separation of Gold(III) from Ore Samples by Solid-Phase Extraction Prior to Its Catalytic Fluorescent Determination

ABSTRACT A new catalytic kinetic fluorescent quenching method for the determination of trace gold(III) was investigated. The method was based on the catalytic effect of gold on oxidation of 3-(3′-methylphenyl)-5- (2′-arsenoxylphenylazo) rhodanine by hydrogen peroxide in potassium hydrogen phthalate–hydrochloric acid (pH = 3.4). Under the optimum conditions, the great decrease of fluorescence intensity has a linear relationship against the concentration of gold in the range of 0 to 12.0 µg·L−1 with a detection limit of 6.0 × 10−10g·L−1. The coexistent metal ions can be separated, and gold can be enriched by TBP resin of solid-phase extraction, which greatly improves the selectivity and sensitivity of the system. The method can be used to determine trace amounts of gold in ore samples successfully with satisfactory results.

High selectivity chemiluminescence sensor for determination of puerarin in diet foods /weight loss promoters based on novel rhodanine and monodisperse molecularly imprinted microspheres

Puerarin-monodisperse molecularly imprinted microspheres were prepared by suspension polymerization. The binding property was investigated by calculating imprinting-induced binding promotion. Using monodisperse microspheres as the recognition material, rhodanine as the chemiluminescence probe, a novel chemiluminescence sensor was developed for the determination of puerarin in diet foods/weight loss promoters. The flow path was designed to obtain a continuous chemiluminescence signal. Due to the combination of special morphology of the monodisperse microspheres and excellent properties of the novel chemiluminescence system, this sensor displayed good selectivity and sensitivity. Under optimum conditions, the CL intensity has a linear relationship versus the concentration of puerarin, the linear range is 1 × 10−7 – 3 × 10−5 g mL−1 with a low detection limit of 3.4 × 10−8 g mL−1. The proposed method showed satisfactory application in the determination of puerarin in diet foods/weight loss promoters.

Determination of thallium(III) with novel arsenoxylphenylazo rhodanine after pre-concentration and separation

A new catalytic kinetic fluorescent method for determination of trace thallium(III) was investigated. The method was based on the catalytic effect of thallium on oxidation of 3-p-chlorophenyl-5-(2′-arsenoxylphenylazo) rhodanine (4ClRAAP) by hydrogen peroxide in potassium hydrogen phthalate-hydrochloric acid (pH = 5.2). Under the optimum conditions the great increase of fluorescence intensity had a linear relationship against the concentration of thallium in the range of 0.43 to 10.0 µg L−1 with a detection limit of 2.6 × 10−10 g L−1. The coexistent metal ions can be separated, and thallium can be enriched by polyamide, which greatly improved the selectivity and sensitivity of the system. The method was applied to determine trace amount of thallium in wine, water and mineral samples, with satisfactory results.

Determination of BSA by Its Enhancement Effect on Second Order Scattering of Chrome Azurol S

Second order scattering (SOS) used to be regarded as a kind of interfere of spectrofluorometry. The characteristic and principle of SOS have not been studied deeply. In this paper SOS was found to be a new method to determine trace substance with good potential of analysis. The reaction between Chrome Azurol S (CAS) and bovine serum albumin (BSA) was investigated by the method of second order scattering. It was found the SOS intensity of CAS and that of BSA is weak respectively in the BR (Britton-Robinson) buffer solution at PH 4.10 with the presence of SDS micelle, but sharply enhanced when the two compounded, based on which a new method for determination of BSA was established, which has high sensitivity and calls for simple operation. The concentration of BSA is linear with CAS in the range of 1.0~2.0 mugldrmL-1. The new method was applied to determination of BSA in real samples with satisfactory results.

Determination of Trace Copper in Natural Waters Using Flow Injection Chemiluminescence System with On-Line Solid-Phase Extraction

A novel flow injection chemiluminescence (FI-CL) system combined with on-line solid phase extraction (SPE) has been developed for the determination of trace copper in natural waters. The chemiluminescence (CL) is obtained by oxidation of novel rhodanine derivative by potassium permanganate in hydrochloric acid in the presence of copper. C 18 -modified silica gel was packed into the glass tube to serve as SPE device. Extraction and preconcentration of the analytes were carried out using on-line SPE system and the selectivity of CL detection was improved. Under the optimum conditions, the calibration graph obtained by injecting copper solutions into the carrier stream is linear with CL intensity over the range of 1.0times10 -3 -2.5 mugldrmL -1 and the detection limit was 0.02 ngldrmL -1 (s/n=3). The method was successfully applied to the determination of copper in natural waters. Compared with most of the other methods reported, the rapid and simple procedure proposed in the text offers higher sensitivity, wider linear range, and better stability.