Spectrofluorimetric determination of glutathione in human plasma by solid-phase extraction using graphene as adsorbent

Utility of 4-chloro-7-nitrobenzofurazan for the spectrofluorimetric determination of butylated hydroxyanisole and propyl gallate in foodstuffs

A spectrofluorimetric method is presented for the determination of 2 synthetic phenolic antioxidants (SPAs), butylated hydroxyanisole (BHA), and propyl gallate (PG) in foodstuffs. The proposed method is based on the derivatization of SPAs with 4-chloro-7-nitrobenzofurazan (NBD-Cl) in phosphate buffer of pH 9.0 to yield a highly fluorescent brown product. The optimum experimental conditions have been studied carefully. Linear calibration curves were obtained over the concentration range of 0.20 to 40 μg mL⁻¹ for BHA, and 0.80 to 50 μg mL⁻¹ for PG, using NBD-Cl reagent. The detection limits were 18 ng mL⁻¹ for BHA, 55 ng mL⁻¹ for PG. Intra-day and inter-day relative standard deviations at 3 different concentrations were determined. The high recovery values indicate the accuracy of the proposed methods, and low relative standard deviation values indicate good precision. The results presented in this report show that the applied spectrofluorimetric method is acceptable for the determination of the 2 SPAs in the foodstuffs. Other SPAs, tertiary butyl hydroquinone and butylated hydroxytoluene in foodstuffs do not interfere with the proposed method.

PRACTICAL APPLICATIONS

In this spectrofluorimetric method, NBD-Cl as a derivation agent is used to detect synthetic phenolic antioxidants. The method specificity has been greatly improved; there was no interference from other commonly used phenolic substances.

Gold nanocluster-based fluorescent probes for near-infrared and turn-on sensing of glutathione in living cells

In this study, a novel Au nanocluster (NC)-based fluorescent sensor has been designed for near-infrared (NIR) and turn-on sensing of glutathione (GSH) in both living cells and human blood samples. The large Stokes-shifted (140 nm) fluorescent Au NCs with NIR emission and long-wavelength excitation have been rapidly synthesized for 2 h by means of a microwave-assisted method in aqueous solution. The addition of Hg(II) leads to an almost complete emission quenching (98%) of Au NCs because of the interaction of Hg(II) and Au(I) on the surface of Au NCs. After introducing GSH to the Au NC-Hg(II) system, a more than 20 times fluorescent enhancement is obtained because of the preferable affinity of GSH with Hg(II). Under optimum conditions, the fluorescence recovery is linearly proportional to the concentration of GSH between 0.04 and 16.0 μM and the detection limit is as low as 7.0 nM. This Au NC-based sensor with high sensitivity and low spectral interference has been proven to facilitate biosensing applications.

Nanoparticle-based microextraction techniques in bioanalysis

Nanoparticles (NPs) have attracted a great deal of attention in the last decade due to their exceptional mechanical, optical and electronic properties. This article deals with the use of NPs as probes for the extraction of biomolecules from biological samples. In this context, NPs present some advantages compared with conventional sorbents. Their high surface-to-volume ratio, easy synthetic (especially for inorganic NPs) and derivatization procedures, and their biocompatibility make them a powerful alternative. In order to provide a systematic approach to the topic, NPs have been divided into two general groups attending to their chemical nature. Carbon-based (e.g., fullerene and nanotubes) and inorganic NPs (e.g., gold and magnetic NPs) are considered in depth, explaining their main properties and applications. After these critical considerations, the most important conclusions and essential trends in this field are also outlined.