Determination of copper traces in water samples by flow injection-flame atomic absorption spectrometry using a novel solidified floating organic drop microextraction method

Cu1.4Mn1.6O4 as a bifunctional transducer for potentiometric Cu2+ solid-contact ion-selective electrode

Current potentiometric Cu2+ sensors mostly rely on polymer-membrane-based solid-contact ion-selective electrodes (SC-ISEs) that constitute ion-selective membranes (ISM) and solid contact (SC) for respective ion recognition and ion-to-electron transduction. Herein, we report an ISM-free Cu2+-SC-ISE based on Cu-Mn oxide (Cu1.4Mn1.6O4) as a bifunctional SC layer. The starting point is simplifying complex multi-interfaces for Cu2+-SC-ISEs. Specifically, ion recognition and signal transduction have been achieved synchronously by an ion-coupled-electron transfer of crystal ion transport and electron transfer of Mn4+/3+ in Cu1.4Mn1.6O4. The proposed Cu1.4Mn1.6O4 electrode discloses comparable sensitivity, response time, high selectivity and stability compared with present ISM-based potentiometric Cu2+ sensors. In addition, the Cu1.4Mn1.6O4 electrode also exhibits near Nernstian responses toward Cu2+ in natural water background. This work emphasizes an ISM-free concept and presents a scheme for the development of potentiometric Cu2+ sensors.

Novel fluorescent nano-sensor based on amino-functionalization of Eu3+:SrSnO3 for copper ion detection in food and real drink water samples

Lanthanide-doped nanoparticles exhibit unique optical properties and have been widely utilized for different sensing applications. Herein, the Eu3+:SrSnO3@APTS nanosensor was synthesized and its optical properties were analyzed using UV-Vis and photoluminescence spectroscopy. The TEM images of the synthesized nanophosphor Eu3+:SrSnO3@APTS exhibited peanut-like morphology, composed of two or more spherical nanoparticles with an average diameter ∼33 nm. Effects of environmental pH values and doping concentrations as well as amino functionalization on the structure of Eu3+:SrSnO3 were investigated. The as-synthesized optical nanosensor was used for determination of copper ions based on a fluorescence quenching approach. Red emission with a long lifetime was obtained in the case of the 0.06 mol Eu3+:SrSnO3@APTS sample. Under the optimal experimental conditions, a Stern-Volmer plot exhibited a good linearity for copper ions over the concentration (0.00-10.8) × 10-11 mol L-1 with a correlation efficient of 0.996 and a limit of detection 3.4 × 10-12 mol L-1. The fluorescent sensor was dynamically quenched via a coulombic interaction mechanism between the Eu3+ (5L6) and Cu2+. The Eu3+:SrSnO3@APTS nanosensor with the optimal Eu3+ dopant concentration of 0.06 mol was applied for copper determination in food and real drink water samples with high recovery values. We believe that the developed nanosensor probe can also be used for the detection of other toxic compounds, with high selectivity and sensitivity.

A Method to Determination of Lead Ions in Aqueous Samples: Ultrasound-Assisted Dispersive Liquid-Liquid Microextraction Method Based on Solidification of Floating Organic Drop and Back-Extraction Followed by FAAS

Ultrasound-assisted dispersive liquid-liquid microextraction method based on solidification of floating organic drop and back-extraction (UA-DLLME-SFO-BE) technique was proposed for preconcentration of lead ions. In this technique, two SFODME steps are applied in sequence. The classical SFODME was applied as the first step and then the second (back-extraction) step was applied. For the classical SFODME, Pb ions were complexed with Congo red at pH 10.0 and then extracted into 1-dodecanol. After this stage, a second extraction step was performed instead of direct determination of the analyte ion in the classical method. For this purpose, the organic phase containing the extracted analyte ions is treated with 1.0 mol·L-1 HNO3 solution and then exposed to ultrasonication. So, the analyte ions were back-extracted into the aqueous phase. Finally, the analyte ions in the aqueous phase were determined by FAAS directly. Owing to the second extraction step, a clogging problem caused by 1-dodecanol during FAAS determination was avoided. Some parameters which affect the extraction efficiency such as pH, volume of extraction solvent, concentration of complexing agent, type, volume, and concentration of back-extraction solvent, effect of cationic surfactant addition, effect of temperature, and so on were examined. Performed experiments showed that optimum pH was 10.0, 1-dodecanol extraction solvent volume was 75 μL, back-extraction solvent was 500 μL, 1.0 mol·L-1 HNO3, extraction time was 4 min, and extraction temperature was 40°C. Under optimum conditions, the enhancement factor, limit of detection, limit of quantification, and relative standard deviation were calculated as 81, 1.9 μg·L-1, 6.4 μg·L-1, and 3.4% (for 25 μg·L-1 Pb2+), respectively.

A highly selective fluorescent chemosensor based on naphthalimide and Schiff base units for Cu2+ detection in aqueous medium

A new Schiff base, 4-allylamine-N-(N-5-methylsalicylidene)-1,8-naphthalimide (1), has been designed and synthesized by combining a 1,8-naphthalimide moiety as a fluorophore and a Schiff base as a recognition group. Its photophysical properties were investigated by absorption and fluorescence spectroscopy, and this sensor exhibits a high fluorescence quantum yield of 0.75–0.91 inorganic solvents of different polarity. It also shows high selectivity for Cu2+ over other ions with fluorescence quenching in aqueous medium (pH=7.2). The reason for this phenomenon (fluorescence quenching) is attributed to the formation of a 1:1 complex between 1 and Cu2+ according to the Job plot and fluorescence titration. The sensor can be applied to the quantification of Cu2+ in a linear fashion from 0.5 to 5 μM with a detection limit of 0.23 μM. Additionally, the association constant (K a) between Cu2+ and 1 is 1.328×106 M− 1 in aqueous media.

Dispersive liquid-liquid microextraction based on solidification of floating organic drop for preconcentration and determination of trace amounts of copper by flame atomic absorption spectrometry

A novel, simple, rapid, sensitive, inexpensive and environmentally friendly dispersive liquid-liquid microextraction method based on the solidification of a floating organic drop (DLLME-SFO) was developed for the determination of copper by flame atomic absorption spectrometry (FAAS). N-o-Vanillidine-2-amino-p-cresol was used as a chelating ligand and 1-undecanol was selected as an extraction solvent. The main parameters affecting the performance of DLLME-SFO, such as sample pH, volume of extraction solvent, extraction time, concentration of the chelating ligand, salt effect, centrifugation time and sample volume were investigated and optimized. The effect of interfering ions on the recovery of copper was also examined. Under the optimum conditions, the detection limit (3σ) was 0.93μgL^-1 for Cu using a sample volume of 20mL, yielding a preconcentration factor of 20. The proposed method was successfully applied to the determination of Cu in tap, river and seawater, rice flour and black tea samples as well as certified reference materials.

Simultaneous column preconcentration of ultra trace amounts of heavy metals with nano-adsorbent in some environmental and biological samples

In the present investigation, multi-walled carbon nanotubes impregnated by 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane were prepared and applied as adsorbent for the simultaneous separation of Bi(III), Cu(II), Cd(II) and Pb(II) ions prior to their determination by electrothermal atomic absorption spectrometry. The following analytical figures of merit were determined for bismuth, copper, cadmium and lead, respectively: enrichment factors of 168, 134, 111 and 146, assay precisions of ±4.6%, ±4.8%, ±5.3% and ±5.0% and detection limits of 11.3, 3.7, 0.5 and 0.3 ng L(-1). The method was successfully applied for the determination of heavy metals in environmental, biological and certified reference materials.

Solidified floating organic drop microextraction for speciation of selenium and its distribution in selenium-rich tea leaves and tea infusion by electrothermal vapourisation inductively coupled plasma mass spectrometry

Solidified floating organic drop microextraction was combined with electrothermal vapourisation inductively coupled plasma mass spectrometry for Se species in Se-rich tea leaves and tea infusion, including total, suspended, soluble, organic and inorganic Se as well as Se(IV) and Se(VI). Ammonium pyrrolidinedithiocarbamate was used as both chelating reagent and chemical modifier in this study. Se(IV) and Se(VI) were separated at pH range of 2.0-5.0. An enrichment factor of 500 was obtained for Se(IV) from this method. Under the optimum conditions, the detection limits for Se(IV) and Se(VI) were 0.19 and 0.26pgmL(-1), respectively. The relative standard deviations were less than 5.5% (c=0.1ngmL(-1), n=9). This method was applied for Se species, its content and distribution in Se-rich tea leaves and tea infusion with satisfactory results. The recoveries of spike experiments are in the range of 92.2-106%. A certified reference material of tea leaves was analyzed by this method, and the results were in agreement with certified values.

A solid-contact ion selective electrode for copper(II) using a succinimide derivative as ionophore

All-solid-state sensors with polyvinyl chloride (PVC)-based membranes using off-the-shelf N-hydroxysuccinimide (NHS) and succinimide (Succ) ionophores were prepared using DOP (dioctyl phthalate) and NPOE (ortho-nitrophenyloctyl ether) as plasticizers. Good responses were obtained when NHS was used. The potentiometric response of the proposed electrode is independent of pH over the range 2-6. The electrode shows a fast response time of 0.25 s. The electrode exhibits a Super-Nernstian response, with 37.5 mV/decade, with a potentiometric detection limit of 4.4 µM. The proposed sensor revealed good selectivity towards a group of transition metal ions.

Heavy metal contents of organically produced, harvested, and dried fruit samples from Kayseri, Turkey

Organically produced, harvested, and dried fruit samples bought at organic markets in Kayseri, Turkey have been analyzed for their trace element contents. In the determinations, flame atomic absorption spectrometer (FAAS) was used. This pilot study is the first to be performed for organically produced, harvested, and dried fruit samples from Kayseri, Turkey. The copper, iron, manganese, and zinc concentrations were found to be 1.6-15.5, 10.3-144, 23.0-211, and 23.3-91.6 μg/g, respectively. The cobalt, lead, cadmium, chromium, and nickel concentrations in all analyzed organic fruit samples were below the quantification limits of FAAS. SRM 1570A spinach leaves and SRM 1515 apple leaves were used to check the accuracy of the procedure. The results for the dried fruit samples found in this work were compared with the values from some studies from the world. The results found in the presented work may also be useful for future studies about organically produced, harvested, and dried fruit samples.