Rapid qualitative and quantitative determination of food colorants by both Raman spectra and Surface-enhanced Raman Scattering (SERS).

Surface Enhanced Raman Scattering (SERS) spectroscopy technology is widely used in materials analysis, environmental monitoring, biomedical, food security and other fields. Flower-shaped silver nanoparticles have been successfully synthesized by a simple aqueous phase silver nitrate reduction by ascorbic acid in the presence of polyvinylpyrrolidone (PVP) surfactant. The nanoparticles diameters were adjusted from 450 to 1000nm with surface protrusions up to 10-25nm. The flower-shaped silver nanostructures obtained were used as stable SERS substrates with high SERS activity for detecting Rhodamine 6G (R6G), at a concentration of only 10-9mol/L, where the SERS signal is still clear. SERS spectroscopy of four different food colorants (e.g. food blue, tartrazine, sunset yellow, acid red) were analysed and the characteristic bands were identified. An improved principle component analysis (PCA) was used for four different food colorants detection, at concentrations down to about 10-8mol/L. Thus, the LOD of food blue, tartrazine, sunset yellow and acid red are 79.285µg/L, 5.3436µg/L, 45.238µg/L and 50.244µg/L, respectively.

Design of a silver nanoparticle for sensitive surface enhanced Raman spectroscopy detection of carmine dye.

Flower-shaped silver nanoparticles have been successfully synthesized by a simple aqueous phase silver nitrate reduction by ascorbic acid in the presence of polyvinylpyrrolidone (PVP) surfactant. The nanoparticles diameters were adjusted from 450 to 1000nm with surface protrusions up to 10-25nm. The growth direction of silver nuclei is controlled by their degree of coating by PVP. The flower-shaped silver nanostructures obtained were used as stable Surface Enhanced Raman Scattering (SERS) substrates with high SERS activity for detecting Rhodamine 6G (R6G), at a concentration of only 10-9M, where the SERS signal is still clear. SERS spectra of the dye carmine was analysed and the characteristic bands were identified. An improved principle component analysis (PCA) was used for carmine detection, at concentrations down to 10-8M. The characteristic peaks of the carmine (1019, 1360, and 1573cm-1) remained at 10-8M. This indicated that the minimum detection limit of AgNP-based substrate for carmine is about 10-8M.

Quantitative Analysis of Mg, Fe and Ca in Jade with Laser Induced Breakdown Spectroscopy.

Based on laser induced breakdown spectroscopy and X-ray fluorescence spectroscopy, The calibration curve of the main elements Mg, Cr and trace element Fe in the Jade samples is obtained based on experimental results. In the experiment, LIBS experiment conditions were 3 µs delay, 110 accumulated laser pulse, 100 mJ·pulse-1, 10 Hz pulse repetition frequency, plasma in Nanyang jade was induced using nono-second Nd∶YAG (wavelength: 1 064 nm) laser as the excitation source in the atmosphere envtronment of the laboratory. The spectral lines in the 300~1 000 nm wavelength range have been identified with the laser-induced breakdown spectroscopy. Through comparing the characteristic spectrum with the National Institute of standards and Technology Research Institute (NIST) database, the element of Mg, Ca and Fe are found in the Jade samples. Using the X-ray fluorescence spectra analyzed the metal elements Mg, Cr and Fe in Nanyang standard jade and obtained the content of elemental oxides, taking the content as standard data and selecting the high content element Al as internal standard element. According to LIBS calibration curve, we can calculate the content of 3 elements in the measured sample. The result shows that the concentration of elements locate in their corresponding standards range, for example, go(0.28%~1.73%), and Fe2O3 (0~0.8%), CaO ( 18%~20%).Because of its unique features, like the absence of sample preparation, the ability to perform real-time, and in situ analysis as well as the quasi non-destruction and micro-analysis character of the measurements, so as to verify the feasibility of LIBS application in jade.