Quantitative Detection Of Melamine Research Articles

Background-free room temperature phosphorescence and digital image colorimetry detection of melamine by carbon nitride quantum dots in cellulose matrix with smartphone-based portable device

Carbon nitride quantum dots (CNQDs) were embedded in the sodium carboxymethyl cellulose (CMC) matrix to form CNQDs-CMC film to explore the room temperature phosphorescence (RTP) of CNQDs, which suppress the non-radiative relaxation process due to the internal hydrogen bonding interactions between CMC and CNQDs. Then, a simple, inexpensive, background-free miniature device integrating with CNQDs-CMC film and smartphone was fabricated for rapid and quantitative detection of melamine (MEL). In the present of MEL, the yellow RTP color of the CNQDs-CMC film was quenched and photographed by the smartphone. The Color Recognizer APP in the smartphone recognized the red (R) value for quantitative detection of MEL. Thus, digital image colorimetry (DIC) determination of MEL was achieved due to the visible RTP color change of CNQDs-CMC film. The smartphone-based miniature device provided a promising platform for the on-site monitoring analytes in the complex matrix including food safety, environmental screening, health monitoring, and disease prevention.

Quantitative Approach to Melamine Detection in Egg White with Surface-Enhanced Raman Spectroscopy

Due to the harmfulness of melamine to human, the quantitative detection of melamine in egg is very necessary. In the present study, the surface enhanced Raman spectra technology combined with chemometric analysis method was used to conduct melamine quantitative detection in egg white. Firstly, the melamine egg sample could be got by the method of artificial feeding hens usingdifferent feeding formulation. Then the surface enhanced Raman spectra of egg white was determined using portable Raman spectroscopy (Opto Trace RamTracer-200) and Raman enhancement reagents, and the melamine content within the white eggs was measured with gas chromatography mass spectrometry technology. The software of Raman Analyzer was used for baseline correction of Raman spectra. The correlation coefficient method was used to choose 320 spectral variables from the surface enhanced Raman spectroscopy as input variables to establish partial least squares quantitative calibration model . And the peaks-decomposition method was used to establish peaks-decomposition quantitative calibration model. Both models selected 90 and 44 samples respectively as calibration sets and validation sets during model establishment, and both models achieved good prediction effect. The determination coefficient between predicted values of partial least squares quantitative calibration model and measured values of gas chromatography mass spectrometry was 0.856, and root mean square error of prediction was 1.547. The determination coefficient was 0.947 and RMSEP was 0.893 for the peaks-decomposition quantitative calibration model. This study demonstrated that the method can effectively quantitatively detect melamine in eggs. Testing a sample only takes 15 minutes, which can provide a new way for the melamine egg detection.

Colorimetric detection of melamine based on methanobactin-mediated synthesis of gold nanoparticles

A simple and rapid field-portable colorimetric method for the detection of melamine in liquid milk was reported. Methanobactin (Mb) could reduce Au (III) to Au (0) and mediate the synthesis of gold nanoparticles (Au-NPs). Upon the addition of melamine, melamine interacted with oxazolone ring of Mb, which interrupted the formation of Au-NPs. Melamine could also stimulate the aggregation of formed Au-NPs. In this paper, these characteristics have been used to detect melamine in liquid milk by naked eyes observation with a detection limit of 5.56×10−6M (0.7mg/kg). Further, the plasmon absorbance of the formed Au-NPs allowed the quantitative detection of melamine by UV–vis spectrometer. A linear correlation was existed between the absorbance and the melamine concentration ranging from 3.90×10−7M to 3.97×10−6M with a correlation coefficient of 0.9685. The detection limit (3σ) obtained by UV–vis spectrum was as low as 2.38×10−7M (i.e., 0.03mg/kg).

Anodic stripping voltammetry of gold nanoparticles at boron-doped diamond electrodes and its application in immunochromatographic strip tests

Anodic stripping voltammetry (ASV) of colloidal gold-nanoparticles (AuNPs) was investigated at boron-doped diamond (BDD) electrodes in 50mM HClO4. A deposition time of 300s at−0.2V (vs. Ag/AgCl) was fixed as the condition for the ASV. The voltammograms showed oxidation peaks that could be attributed to the oxidation of gold. These oxidation peaks were then investigated for potential application in immunochromatographic strip tests for the selective and quantitative detection of melamine, in which AuNPs were used as the label for the antibody of melamine. Linear regression of the oxidation peak currents appeared in the concentration range from 0.05–0.6μg/mL melamine standard, with an estimated LOD of 0.069μg/mL and an average relative standard deviation of 8.0%. This indicated that the method could be considered as an alternative method for selective and quantitative immunochromatographic applications. The validity was examined by the measurements of melamine injected into milk samples, which showed good recovery percentages during the measurements.

Visual Detection and Determination of Melamine Using Synthetic Dyes

We have used spectroscopic technique for the detection of melamine. The effect of melamine on the colour as well as the pH of bromophenol, methyl red and alizarin red dye solutions was examined at different mole ratios. It is found that we observe color transition and the absorption maxima for bromophenol were at 598 nm, while for methyl red, and alizarin red-S dye they are at 520 nm and 423 nm, respectively. We observe an increase in the absorption intensities at 598 nm with increase in the concentration of melamine in bromophenol blue dye. The absorption intensities at 520 nm decreases and new peak at 420 nm emerges in methyl red dye-melamine mixture. While the absorption intensities at 420 nm decreases and 520 nm peak emerges in alizarin red S dye-melamine at higher mole ratios. The results indicate that we can choose the appropriate dye of suitable range to detect the concentration of melamine from 3 to 206 mg dm−3. The results demonstrate possible use of the simple method for the qualitative and quantitative detection of melamine in adulterated food samples.

Development of Immunochromatographic Strip Tests for Selective and Quantitative Detection of Melamine

An immunochromatographic strip test based on the complex reaction of antigen-antibody (melamine-antimelamine) was developed for quantitative detection of melamine. Gold nanoparticles (AuNP) were used to form AuNP-labeled antibody, which then acted as a biosensor. Melamine q uantification was performed by the determination of AuNP using anodic stripping voltammetry technique with a boron-doped diamond as the working electrode. With sample volume of 100 µL and immunoreaction time of 7 min, the developed immunochromatographic strip test produced a linear calibration curve for melamine concentration range of 0–0.6 mg/L, with detection limit of 0.1 mg/L and RSD of ~5%. Furthermore, negative results were obtained for samples containing cyanuric acid and urea, indicating that the developed immunochromatographi c strip test has potential for selective and quantitative detection of melamine.

Electrochemical Immunochromatographic Strip Test for Melamine Biosensor in Milk Products Using Silver Nanoparticles as Probe

A quantitative and sensitive immunochromatographic strip test is developed to detect of melamine in milk products. The strip test based on antigen-antibody (melamine-anti melamine) complex reaction. As label to antibody is used silver nanoparticles to form antibody-silver nanoparticles (AgNP-Ab). The strip test consists of sample pad, conjugated pad (AgNP-Ab), nitrocelloluse membrane, test zone (Ab), and absorbant pad. When melamine is found in the sample, then antibody-melamine-antibody-silver nanoparticles complex was made. Silver nanoparticles have good electrochemical properties. Electrochemical measurement of silver nanoparticles is using anodic stripping voltammetry method. The strip test electrode device is using Ag/AgCl as reference electrode, glassy carbon (GC) as working electrode and platinum (Pt) wire as counter electrode. The quantity of silver nanoparticles is involved in the system is equivalent to the concentration of melamine. Therefore, quantitative detection of melamine could be done using the immunochromatographic strip test.

Fabrication and Calibration of an Ag Nanoparticles Sensor for Detecting the Melamine and NaCl Levels in Raw Milk

ABSTRACT A colorimetric, label-free, and aggregation-based Ag nanoparticles (AgNPs) probe was developed for the detection of melamine and NaCl. A color change from yellow to blue with increasing melamine concentration was observed. The plasmon absorbance of the formed AgNPs allowed quantitative detection of melamine. A sensitive nonlinear correlation existed between the absorbance and the logarithm of melamine concentration, ranging from 1000 to 0.25 ppm. Detection of NaCl at a concentration of 10 ppm in raw milk was also observed.

Hydrogen-bonding-induced colorimetric detection of melamine by nonaggregation-based Au-NPs as a probe

A colorimetric, label-free, and nonaggregation-based gold nanoparticles probe has been developed for the detection of melamine. Gold nanoparticles were generated using 3,5-dihydroxybenzoic acid as a reducer without adding gold nanoparticle seeds at room temperature. Upon the addition of melamine, the reducer 3,5-dihydroxybenzoic acid can interact with melamine through strong hydrogen-bonding interaction. Consequently, the formation of gold nanoparticles was interrupted by melamine since there was not enough reducer for the reduction of Au 3+ ion. And the color change from purple to yellowgreen with increasing melamine concentration was observed. The plasmon absorbance of the formed Au-NPs allows the quantitative detection of melamine. A sensitive linear correlation existed between the absorbance and the logarithm of melamine concentration ranging from 1 × 10 −9 M to 1 × 10 −5 M with a linear coefficiency of 0.993. The system has a high selectivity to melamine with a low detection limit of 8 × 10 −10 M.