Study of the interaction of Zn^(2+) with Aβ(10-21) by fluorescamine assay

Zinc may play a role as a co-factor in the pathogenesis of Alzheimer＇s disease （AD） through influencing the conformation and neurotoxicity of amyloid β-protein （Aβ）. Using the fluorescamine assay, we show for the first time that Zn^2＋ induced Aβ（10-21） aggregate in a concentration-dependent manner. These results indicate that Aβ（10-21） can be used as an in vitro model in Zn^2＋ - induced Aβ aggregation and that the region 10-21 to be the minimal fragment of zinc-binding domain of full length Aβ（1-42）.

Determination of Sulfadiazine Based on Its Derivatization with Fluorescamine by Self-Ordered Ring Fluorescence Microscopic Imaging Technique

A self-ordered ring(SOR) fluorescence microscopic imaging technique has been developed for the determination of trace amounts of sulfadiazine based on its derivatization with fluorescamine.In the presence of HAc-NaAc buffer solution(pH 3.12) and polyvinyl alcohol-124(PVA-124),the droplet containing fluorescamine derivatized sulfadiazine can form a SOR on the solid support after solvent evaporation with the diameter of 1.86mm and its ring belt width of 54.9 μ m.The quantitative analysis of sulfadiazine is achieved with the linear range of 7.8×10-14 ～1.8×10-12 mol·ring-1(3.9×10-7 ～9.0×10-6 mol·L-1) and detection limit of 7.8×10-15 mol·ring-1(3.9×10-8 mol·L-1) when 0.2 μ L droplet was spotted.The technique has been satisfactorily applied to the determination of sulfadiazine in the tablet,synthetic sample and residues in six different milk samples with the recoveries of 91.0%～105.8%,respectively,and RSDs less than 4.4%.

High Performance Liquid Chromatography for the Determina- tion of Metoclopramide in Pharmaceutical Preparations Using Pre-column Derivatization with Fluorescamine

A simple, rapid and sensitive high performance liquid chromatography （HPLC） method was developed for the determination of metoclopramide in pharmaceutical preparation. The method is based on the derivatization of metoclopramide with fluorescamine. The separation was achieved on a C18 column using methanol-water （70 ： 30, V/V） mobile phase. Fluorescence detector was used at the excitation and emission of 403 and 485 nm, respectively. The method was validated for linearity, limit of detection, limit of quantification, precision, accuracy, recovery, robust- ness and system suitability. The assay was linear over the concentration range of 100-2000 ng/mL. The mean recovery was 100.37%. The proposed method was successfully applied to the assay of metoclopramide in tablet preparation. The preparation was also analyzed with an official method and statistical comparison by t- and F-tests revealed that there was no significant difference between the results of the two methods with respect to mean values and standard deviations at the 95% confidence level.

Improved speciation of dissolved organic nitrogen in natural waters: amide hydrolysis with fluorescence derivatization

The objective of this study was to improve primary-amine nitrogen (1°-N) quantification in dissolved organic matter (DOM) originating from natural waters where inorganic forms of N, which may cause analytical interference, are commonly encountered. Efforts were targeted at elucidating organic-N structural criteria influencing the response of organic amines to known colorimetric and fluorescent reagents and exploring the use of divalent metal-assisted amide hydrolysis in combination with fluorescence analyse...

Exploring the potential of simple automation concepts for quantifying functional groups on nanomaterials with optical assays

Until now, automation in nanomaterial research has been largely focused on the automated synthesis of engineered nanoparticles (NPs) including the screening of synthesis parameters and the automation of characterization methods such as electron microscopy. Despite the rapidly increasing number of NP samples analyzed due to increasing requirements on NP quality control, increasing safety concerns, and regulatory requirements, automation has not yet been introduced into workflows of analytical methods utilized for screening, monitoring, and quantifying functional groups (FGs) on NPs. To address this gap, we studied the potential of simple automation tools for the quantification of amino surface groups on different types of aminated NPs, varying in size, chemical composition, and optical properties, with the exemplarily chosen sensitive optical fluorescamine (Fluram) assay. This broadly applied, but reportedly error-prone assay, which utilizes a chromogenic reporter, involves multiple pipetting and dilution steps and photometric or fluorometric detection. In this study, we compared the influence of automated and manual pipetting on the results of this assay, which was automatically read out with a microplate reader. Special emphasis was dedicated to parameters like accuracy, consistency, achievable uncertainties, and speed of analysis and to possible interferences from the NPs. Our results highlight the advantages of automated surface FG quantification and the huge potential of automation for nanotechnology. In the future, this will facilitate process and quality control of NP fabrication, surface modification, and stability monitoring and help to produce large data sets for nanomaterial grouping approaches for sustainable and safe-by-design, performance, and risk assessment studies.