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The first page of this article is displayed as the abstract.

The first page of this article is displayed as the abstract.

The first page of this article is displayed as the abstract.

The first page of this article is displayed as the abstract.

The first page of this article is displayed as the abstract.

In this study, a new algorithm for wavelength interval selection, known as interval variable iterative space shrinkage approach ( i VISSA), is proposed based on the VISSA algorithm. It combines global and local searches to iteratively and intelligently optimize the locations, widths and combinations of the spectral intervals. In the global search procedure, it inherits the merit of soft shrinkage from VISSA to search the locations and combinations of informative wavelengths, whereas in the local search procedure, it utilizes the information of continuity in spectroscopic data to determine the widths of wavelength intervals. The global and local search procedures are carried out alternatively to realize wavelength interval selection. This method was tested using three near infrared (NIR) datasets. Some high-performing wavelength selection methods, such as synergy interval partial least squares ( si PLS), moving window partial least squares (MW-PLS), competitive adaptive reweighted sampling (CARS), genetic algorithm PLS (GA-PLS) and interval random frog ( i RF), were used for comparison. The results show that the proposed method is very promising with good results both on prediction capability and stability. The MATLAB codes for implementing i VISSA are freely available on the website: http://www.mathworks.com/matlabcentral/fileexchange/49028-ivissa.

A simple and highly sensitive fluorometric method has been developed for inorganic pyrophosphatase (PPase) activity detection based on the disaggregation and aggregation of graphene quantum dots (GQDs). Copper ions can trigger the severe aggregation of GQDs with rich carboxyl groups, which results in effective fluorescence quenching. While, with the addition of pyrophosphate (PPi), the quenched fluorescence is effectively recovered owing to the strong interaction between PPi and Cu 2+ . Furthermore, under the catalytic hydrolysis of PPase, the complex of PPi–Cu 2+ –PPi is rapidly disassembled, and the fluorescence is re-quenched. This method is highly sensitive and selective for PPase detection, with a linear correlation between the fluorescence intensity and the PPase concentration in the range from 1 to 200 mU mL ?1 with a detection limit down to 1 mU mL ?1 (S/N = 3). Additionally, the inhibition effect of NaF on the PPase activity is also studied. Thus, the proposed method may hold a potential application in the diagnosis of PPase-related diseases and screening of PPase inhibitors, to evaluate the function and inhibition of PPase in biological systems.

A new dye , PTZ-Cy2 , based on a hybrid cyanine– phenothiazine platform, is described. Oxidation by highly reactive oxygen species (hROS) involves attack at the thiazine sulfur atom and destruction of the π conjugation of the cyanine moiety. Dual fluorescence emissions are enhanced dramatically at λ em 470 nm and 595 nm, and PTZ-Cy2 thus serves both as an absorbance ratiometric and a fluorescent “off–on” sensor for detecting hROS. Moreover PTZ-Cy2 shows selectivity for hROS over other oxidants, and gives a highly sensitive response to such endogenous species within the mitochondria of living cells.

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A new approach to the rapid determination of amoxicillin (AMO) in human plasma followed by solid phase microextraction ( SPME ) fiber coatings based on conducting polymers ( polypyrrole and polythiophene) and high performance liquid chromatography ( HPLC ) has been described. The porous structures of the electrochemically deposited polymer coatings have been characterized by scanning electron microscopy ( SEM ). The experimental parameters relating to the extraction efficiency of the SPME fibers such as pH, extraction time and desorption conditions ( solvents , time) were studied and selected. The SPME /HPLC-UV method was linear over a working range of 1–50 μg ml ?1 . The inter-day accuracy (expressed as coefficients of variations, CVs) was less than 15% and precision (expressed as the relative standard deviations, RSDs) with percentage values was less than 5.9%. Amoxicillin was found to be stable in the human plasma at room temperature (20 °C) within 8 hours. The developed method was successfully applied to the analysis of real human plasma samples. The limit of detection and limit of quantification for amoxicillin in plasma were 1.21 μg ml ?1 and 3.48 μg ml ?1 , respectively.