Simultaneous colorimetric determination of morphine and ibuprofen based on the aggregation of gold nanoparticles using partial least square

In this work a new method is presented for simultaneous colorimetric determination of morphine （MOR） and ibuprofen （IBU） based on the aggregation of citrate-capped gold nanoparticles （AuNPs）. Citrate-capped AuNPs were aggregated in the presence of MOR and IBU. The difference in kinetics of AuNPs aggregation in the presence of MOR/IBU was used for simultaneous analysis of MOR and IBU. The formation and size of synthesized AuNPs and the aggregated forms were monitored by infra-red （IR） spectroscopy and transmission electron microscopy （TEM）, respectively. By adding MOR or IBU the absorbance was decreased at 520 nm and increased at 620 nm. The difference in kinetic profiles of aggregation was applied for simultaneous analysis of MOR and IBU using partial least square （PLS） regression as an efficient multivariate calibration method. The number of PLS latent variables was optimized by leave-one-out cross-validation method using predicted residual error sum of square. The proposed model exhibited a high capability in simultaneous prediction of MOR and IBU concentrations in real samples. The results showed linear ranges of 1.33-33.29 μg/mL （R2=0.9904） and 0.28-6.9 μg/mL （R2=0.9902） for MOR and IBU respectively with low detection limits of 0.15 and 0.03 μg/mL（S/N=5）.

Synthesis and Determination of Stability Constants of a New Bis-1,2,4-triazole Ligand for Complexation with Zinc(II), Copper(II) and Nickel(II) in Acetonitrile

In this work, the synthesis and complexation properties of a new compound, 1,3-bis[5-(2-hydroxyphenyl)-4-phenyl- 1,2,4-triazole-3-yl-thio]propane (BTP), towards certain transition metal ions, (M(II) where M = Zn, Cu, Ni) in acetonitrile is reported. A hard-modeling strategy was applied to UV-Visible spectroscopy data obtained from monitoring the reaction between BTP and the selected metal ions to determine the concentration profiles of each species and the corresponding stability constant(s) of the complex(es). The stability constants of complexes are always defined in terms of their free metal, free ligand and complexed forms. These constants are influenced by parameters such as the type of metal, ligand, counterion or solvent. In this study, the formation constants of the complexes were determined for the synthesized ligand with several metallic cations in acetonitrile solvent by UV-Vis spectrophotometry.

A selective, sensitive and label-free visual assay of fructose using anti-aggregation of gold nanoparticles as a colorimetric probe

A new convenient colorimetric sensor for fructose based on anti-aggregation of citrate-capped gold nanoparticles（Au NPs） is presented. 4-Mercaptophenylboronic acid（MPBA） induces the aggregation of Au NPs, leading to a color change from red to blue. Fructose as a potent competitor has strong affinity for MPBA and a borate ester is formed between MPBA and fructose. There is an obvious color change from blue to red with increasing the concentration of fructose. The anti-aggregation effect of fructose on Au NPs was seen by the naked eye and monitored by UV–vis spectra. Our results showed that the absorbance ratio（A（519）/A（640）） was linear with fructose concentration in the range of 0.032–0.96 μmol/L（R^2= 0.996）, with a low detection limit of 0.01 μmol/L（S/N = 3）. Notably, a highly selective recognition of fructose was shown against other monosaccharide and disaccharide（glucose, mannose, galactose,lactose and saccharose）. With anti-aggregation assays higher selectivity is achievable. The results of this work provide a rapid method for evaluating the quantitative analysis of fructose in human plasma at physiologically meaningful concentrations and at neutral pH. The proposed procedure can be used as an efficient method for the precise and accurate determination of fructose.