Microwave synthesis of blue emissive carbon dots from 5-sulpho anthranilic acid and 1,5-diphenyl carbazide for sensing of levocetirizine and niflumic acid.

In this work, water soluble carbon dots (CDs) were synthesized by using 5- sulpho anthranilic acid (SAA) and 1,5-diphenylycarbazide (DPC) as precursors via microwave-assisted method and named as "SD-CDs". We studied the effect of SAA and DPC molar ratio (1:3, 2:2 and 3:1) for the preparation of blue fluorescent CDs, showing the best emission properties at molar 3:1 ratio of SAA and DPC. The as-prepared SD-CDs emit bright blue color under UV light at 365 nm, and exhibit emission peak at 392 nm when excited at 319 nm. The as-synthesized SD-CDs act as a fluorescent sensor for detection of levocetirizine and niflumic acid through the fluorescence "turn-on-off" mechanism. The developed probe exhibited good linearity in the concentrations (levocetirizine - 1.0-100 µM and niflumic acid - 0.5-100 µM) with detection limits of 3.92 nM and 0.19 µM for levocetirizine and niflumic acid, respectively. Importantly, the developed analytical method was successfully used for the detection of levocetirizine in tablets and niflumic acid in biofluids of human (serum, plasma and urine), showing good recoveries from 97 to 99 %. Thus, this SD-CDs-based fluorescence method has the potential for levocetirizine and niflumic acid assays in biological and pharmaceutical samples.

Nanomaterial-based electrochemical sensors for arsenic - A review.

The existence of arsenic in the environment poses severe global health threats. Considering its toxicity, the sensing of arsenic is extremely important. Due to the complexity of environmental and biological samples, many of the available detection methods for arsenic have serious limitations on selectivity and sensitivity. To improve sensitivity and selectivity and to circumvent interferences, different electrode systems have been developed based on surface modification with nanomaterials including carbonaceous nanomaterials, metallic nanoparticles (MNPs), metal nanotubes (MNTs), and even enzymes. Despite the progress made in electrochemical sensing of arsenic, some issues still need to be addressed to realize cost effective, portable, and flow-injection type sensor systems. The present review provides an in-depth evaluation of the nanoparticle-modified electrode (NME) based methods for the electrochemical sensing of arsenic. NME based sensing systems are projected to become an important option for monitoring hazardous pollutants in both environmental and biological media.

Identification of multiply charged proteins and amino acid clusters by liquid nitrogen assisted spray ionization mass spectrometry.

The development of liquid nitrogen assisted spray ionization mass spectrometry (LNASI MS) for the analysis of multiply charged proteins (insulin, ubiquitin, cytochrome c, α-lactalbumin, myoglobin and BSA), peptides (glutathione, HW6, angiotensin-II and valinomycin) and amino acid (arginine) clusters is described. The charged droplets are formed by liquid nitrogen assisted sample spray through a stainless steel nebulizer and transported into mass analyzer for the identification of multiply charged protein ions. The effects of acids and modifier volumes for the efficient ionization of the above analytes in LNASI MS were carefully investigated. Multiply charged proteins and amino acid clusters were effectively identified by LNASI MS. The present approach can effectively detect the multiply charged states of cytochrome c at 400 nM. A comparison between LNASI and ESI, CSI, SSI and V-EASI methods on instrumental conditions, applied temperature and observed charge states for the multiply charged proteins, shows that the LNASI method produces the good quality spectra of amino acid clusters at ambient conditions without applied any electric field and heat. To date, we believe that the LNASI method is the most simple, low cost and provided an alternative paradigm for production of multiply charged ions by LNASI MS, just as ESI-like ions yet no need for applying any electrical field and it could be operated at low temperature for generation of highly charged protein/peptide ions.

Facile and sensitive determination of selenium (IV) in pharmaceutical formulations by flow injection spectrophotometry.

An automated flow injection spectrophotometric method has been developed for the rapid, simple, selective, and sensitive determination of selenium (IV) from various pharmaceutical multivitamin and mineral formulations. The method was based on the oxidation of 4-aminoantipyrine (4-amino-l,2-dihydro-1,5-dimethyl-2-phenyl-3H-pyrazole-3-one; 4-AAP) by selenium in presence of acidic medium and the coupling with N-(naphthalen-l-yl)ethane-1,2-diamine dihydrochloride (NEDA) to give a violet color derivative. Gilson P2 mini pulse peristaltic pump has been used for introducing the selenium (IV), dilute HCl, 4-AAP and NEDA solutions into reaction coil by an automatic system. The absorbance of the 4-AAP-NEDA color derivative was measured at 563 nm after a reaction time of 3 min in stop flow of 4-AAP-NEDA. Beer's law was obeyed for selenium in the concentration range 0.05-5.0 microg mL(-1) and Sandell's sensitivity was found to be 0.00286 microg cm2. The performance of the present method was compared with the official method in terms of Student's F- and t-tests, and no significant difference was observed. This method was found to be suitable for estimating the selenium (IV) concentration in various pharmaceutical multivitamin and mineral formulations such as tablets and capsules.

Ultra-fast simultaneous analysis of genetically modified organisms in maize by microchip electrophoresis with LIF detector.

This study examined the potential of microchip electrophoresis (ME) with a LIF detector using a programmed field strength gradient (PFSG) in a conventional glass double-T microchip for the ultra-fast detection and simultaneous analysis of genetically modified (GM) maize. The separation efficiency and sensitivity at various sieving gels (poly(ethylene oxide) (PEO, M(r) 8,000,000) and 2-hydroxyethylcellulose (HEC) (M(r) 250,000)) and fluorescent dye concentrations were investigated. The PCR products of both the GM and non-GM maize were analyzed within 30 s under the PFSG (470.6 V/cm for 20 s, 117.6 V/cm for 12 s, and 470.6 V/cm for 30 s) with a 2.5% HEC sieving matrix in the running buffer, 1 x Tris-borate EDTA (TBE) (pH 8.30) and 0.5 ppm ethidium bromide. The five transgenic maize varieties (Event176, MON810, Bt11, GA21, and T25) examined in this study were also clearly differentiated by ME-PFSG within 30 s in a single run without any loss of resolution. The ME-PFSG technique is a powerful tool for the ultra-fast detection and simultaneous analysis of GMOs in a variety of foods including maize.

Spectrophotometric determination with a chromogenic reagent of lead in vegetables.

A method was developed for the simple, selective, and sensitive spectrophotometric determination of lead in vegetables with synthesized chromogenic reagent 3-[(2,6-dibromo-4-methylphenyl)diazenyl]-4,5-dihydroxy-6-[(2,4,6-tribromophenyl)diazenyl]naphthalene-2,7-disulfonic acid (DBMTBA; 1). In 0.25 M phosphoric acid medium, which greatly increases the selectivity, lead reacts with DBMTBA to form a 1:2 blue complex, which shows maximum absorption at 646 nm. Under optimal conditions, Beer's law is obeyed over the range from 0.09 to 0.8 microg ml(-1) Pb2+, and the apparent molar absorptivity is 1.024x10(5) l mol(-1) cm(-1). The detection limit and the variation coefficient were found to be 2.09 microg ml(-1) and 1.0%, resp. The proposed method has been applied successfully for the determination of lead in vegetables (Solanum melongena fruits, tomato fruits, Ablemoschus esculentus leaves, and Daucous carota leaves) with satisfactory results.

Inductively coupled plasma-optical emission spectrometry for on-line determination of multi trace elements in environmental samples after preconcentration by using Borassus flabellifer inflorescence loaded with 2-propylpiperidine-1-carbodithioate.

A procedure was developed for the determination of Cu, Mn, Pb, Cd, Co, Cr, and Zn in water samples by Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) after preconcentration on synthesized 2-propylpiperidine-1-carbodithioate supported by Borassus flabellifer Inflorescence (BFI). The sorbed element was subsequently eluted with 0.4 M HNO3, and the acid eluates were analyzed by ICP-OES. The influence of various parameters such as pH, flow rate of sample, eluent concentration, volume of the sample, and volume of eluent were investigated. Under the optimal conditions, Cu, Mn, Pb, Cd, Co, Cr, and Zn in aqueous samples were concentrated ca. 100-fold. Recoveries were obtained by the proposed method in the range of 97.8-99.9%. This method was also applied for the analysis of spiked, natural waters and soil samples. The results provide strong evidence to support the hypothesis of an adsorption mechanism.