A novel solidified floating organic drop microextraction method for preconcentration and determination of copper ions by flow injection flame atomic absorption spectrometry

Determination of copper in rose tea samples using flame atomic absorption spectrometry after emulsification liquid-liquid microextraction

Rose tea infusion has gained popularity worldwide due to its health benefits. However, it is known that tea plants can be contaminated with heavy metals including copper. Hence, an accurate and applicable analytical method namely emulsification liquid-liquid microextraction based deep eutectic solvent - flame atomic absorption spectrometry (ELLME-DES-FAAS) was proposed to determine copper at trace levels in rose tea samples. Under the optimum experimental conditions, analytical figures of merit for the developed method were examined, and dynamic range, limit of detection (LOD) and limit of quantification (LOQ) were found to be 5.07-246.61 µg/kg (mass-based) with 0.9992 coefficient of determination, 2.50 µg/kg and 8.32 µg/kg, respectively. A matrix matching calibration strategy was employed to boost recovery results, and the acceptable recovery results were recorded between 95.9 % and 118.4 %. According to recovery results, the developed analytical method can be safely employed to determine the concentration of copper in rose tea samples accurately.

Dual techniques for trace copper determination: DES/Dithizone based liquid phase microextraction-flame atomic absorption spectrophotometry and digital image based colorimetric probe

In this study, a sample preparation procedure was developed to preconcentrate copper ions from aqueous samples for determination by flame atomic absorption spectrometry (FAAS) and digital image based colorimetry (DIC) systems. This was achieved by complexing copper ions with dithizone (Cu-DZ) and extracting the complex from aqueous solution in a single step. For the DES/DZ-FAAS system, a low detection limit of 2.3 ng mL-1 was recorded over a broad and linear working range. For the DIC system, the linear relationship between the change in red color intensity of the red-green-blue (RGB) color scale and the concentration of copper in the Cu-DZ complex was utilized for the validation of the method. The DIC system also recorded a broad and linear working range with a satisfactory detection limit of 14.7 ng mL-1. Spike recovery experiments performed with eucalyptus tea extracts yielded high recovery results in the range of 91-107%.

Development of a metal sieve-linked double syringe liquid phase microextraction method for the determination of copper in olive leaf extract samples by flame atomic absorption spectrometry

This work reports the development of a simple, sensitive and low-cost analytical method for the trace determination of copper. A metal sieve-linked double syringe liquid phase microextraction method was used to preconcentrate copper into measurable quantities for FAAS system. The pressurized mixing offered by the automated syringe system and the sieve connector enhanced surface area for analyte and extraction solvent interaction, this significantly increased the extraction efficiency for copper. There was therefore no need for auxiliary organic solvents as disperser solvents for the extractant dichloromethane. The limits of detection and quantification, linear dynamic range and percent relative standard deviation values calculated for copper under optimum conditions of the method were 1.5 and 5.1 µg L^-1, 5.0-500 µg L^-1 and 8.4%, respectively. The developed method was successfully employed to determine copper (0.75-8.06 mg kg^-1) in unspiked olive leaf samples.

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.

Synthesis of a single 1,8-naphthalimide fluorophore as a molecular logic lab for simultaneously detecting of Fe3+, Hg2+ and Cu2

A novel fluorescence sensing 1,8-naphthalimide fluorophore is synthesized and investigated. The novel probe comprising two different binding moieties is capable to detect selectively Fe³⁺ over the other representative metal ions as well as a combination of biologically important cations such as Fe³⁺, Cu²⁺ and Hg²⁺ in the physiological range without an interfering effect of the pHs. Due to the remarkable fluorescence changes in the presence of Fe³⁺, Hg²⁺ and Cu²⁺ ions, INH and AND logic gates are executed and the system is able to act as a single output combinatorial logic circuit with three chemical inputs.

Metal–organic framework based micro solid phase extraction coupled with supramolecular solvent microextraction to determine copper in water and food samples

D-μ-SPE-SUPRAS-ME followed by GFAAS was successfully used for preconcentration and determination of copper in real samples.

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.

Supramolecular solvent-based dispersive liquid–liquid microextraction of copper from water and hair samples

A supramolecular solvent based dispersive liquid–liquid microextraction (SM-DLLME) procedure has been established for the separation and preconcentration of Cu(ii) before its determination by microsampling flame atomic absorption spectrometry.

Selective electrochemical determination of trace level copper using a salicylaldehyde azine/MWCNTs/Nafion modified pyrolytic graphite electrode by the anodic stripping voltammetric method

Schematic illustration of Cu²⁺in solution detection using a SA/MWCNTs/Nafion modified PGE.

Incorporation of flow injection analysis with dual-wavelength overlapping resonance Rayleigh scattering for rapid determination of malachite green and its metabolite in fish

A flow injection analysis (FIA) system combined with dual-wavelength overlapping resonance Rayleigh scattering (DWO-RRS) has been established and validated for rapid determination of malachite green (MG) and its metabolite in fish samples. Under experimental condition, MG would react with Erythrosin (Ery) to form ion-association complexes, resulting in the occurrence of two RRS peaks and a dramatic enhancement of RRS intensity. The maximum RRS peaks were located at 286 nm and 337 nm. It is noted that the increments of both of these two peaks were proportional to the concentration of MG. The detection limit of DWO-RRS was 1.5 ng/mL, which was comparable to several reported methods. Moreover, the results of real sample analysis exhibited an acceptable recovery between 97.5% and 103.6%, indicating that the method had good reproducibility.

Solid-contact polyvinyl chloride membrane electrode based on the bis[(2-(hydroxyethylimino)phenolato]copper(II) complex for trace level determination of copper ions in wastewater

A miniaturized solid-contact polyvinyl chloride membrane electrode based on the bis[(2-(hydroxyethylimino)phenolato]copper(II) complex has been prepared for the determination of Cu(II) ion in real samples. The influence of coating membrane composition, pH, and possible interfering cations on the response of the ion-selective electrode was investigated. A number of membranes at different compositions were prepared and their Cu2+ sensing capabilities were investigated. The best results for Cu2+ sensing was obtained for the electrode membrane containing ionophore − 2-nitrophenyloctyl ether – polyvinyl chloride and potassium tetrakis(p-chlorophenyl)borate in a ratio of 4:65:30:1 (w/w, mg), respectively. The prepared electrode exhibited a near-Nernstian response (28.3 mV/decade) to Cu2+ in the concentration range from 1.0 × 10−6 to 1.0 × 10−1 mol/L with a limit of detection of 8.3 × 10−7 mol/L. The potentiometric response of the electrode was independent from the pH of the test solution in the pH range of 3.0–6.0. The electrode has a very short response time, about 15 s, and it can be used over a period of 3 months without any divergence in potential. The electrode has been successfully applied as an indicator electrode in potentiometric titration of Cu(II) ions with ethylenediaminetetraacetic acid and in the determination of Cu(II) in wastewater of the copper processing industry.

A new carbazole-based Schiff-base as fluorescent chemosensor for selective detection of Fe3+ and Cu2+

A new carbazole-based Schiff-base (1) as a multi-functional fluorescent chemosensor was designed, synthesized and characterized, which can selectively recognized Fe(3+) and Cu(2+) ions over a number of other metal ions. Compound 1 could detect Fe(3+) and Cu(2+) by UV-Vis method and fluorescence method. The stoichiometry ratio of 1-Fe(3+) and 1-Cu(2+) are 2:1 and 1:1, respectively, by the method of Job's plot. Moreover, the detection limits were calculated to be 4.23×10(-6) mol/L for Fe(3+) ion and 5.67×10(-6) mol/L for Cu(2+) ion. In the presence of Fe(3+)/Cu(2+) ions, the fluorescence enhancement was attributed to the inhibited C=N isomerization and the obstructed excited state intramolecular proton transfer (ESIPT) of compound 1. At the same time, the interactions of compounds 1 with other ions were also investigated and unobvious UV-Vis absorption and fluorescence spectral changes were observed. Thus a new kind of chemosensor for Fe(3+)/Cu(2+)with high sensitivity and selectivity was introduced.

Simultaneous preconcentration of copper and mercury in water samples by cloud point extraction and their determination by inductively coupled plasma atomic emission spectrometry

A cloud-point extraction process coupled to ICP-OES by using 3-nitro benzaldehyde thiosemicarbazone (3-NBT) as complexing agent was developed for the simultaneous preconcentration and determination of copper and mercury in water samples. The variables affecting the complexation and extraction steps were optimized. Under the optimum conditions (i.e. 1.5×10(-5) mol L(-1) ligand, 0.3% (v/v) Triton X-114, 55 °C equilibrium temperature, incubation time of 30 min) the calibration graphs were linear in the range of 5-120 and 10-100 ng mL(-1) with enhancement factor of 82.7 and 51.3 for Cu(2+) and Hg(2+), respectively. The preconcentration factors were 28.6 in both cases and detection limits were obtained 0.48 for Cu and 1.1 ng mL(-1) for Hg. The precisions (R.S.D.%) for five replicate determinations at 50 ng mL(-1) of copper and mercury were better than 1.8% and 3.2%, respectively. The accuracy of the proposed method is validated by analyzing a certified reference material of water (RTC-QCI-049) with satisfactory results. Finally, the proposed method was utilized successfully for the determination of copper and mercury in surface water (river), tap water and bottled mineral water samples.

Old and New Flavors of Flame (Furnace) Atomic Absorption Spectrometry

This paper presents some recent applications of Flame Atomic Absorption Spectrometry (FAAS) to different matrices and samples. The time window selected was from 2006 up to March, 2011, and several aspects related to food, biological fluids, environmental, and technological samples analyses were reported and discussed. In addition, the chemometrics application for FAAS methods development was also taken into account, as well as the use of metal tube atomizers in air/acetylene flame. Preconcentration methods coupled to FAAS were discussed, and several approaches related to speciation, flotation, ionic liquids, among others were discussed. This paper can be interesting for researchers and FAAS users in order to see the state of the art of this technique.

Speciation and determination of ultra trace amounts of chromium by solidified floating organic drop microextraction (SFODME) and graphite furnace atomic absorption spectrometry

Solidified floating organic drop microextraction (SFODME) method in combination with graphite furnace atomic absorption spectrometry (GFAAS) has been used for the determination of chromium species in water and urine samples. 1-undecanol containing 2-thenoyltrifluoroacetone (TTA) was used as a selective chelating agent for the extraction of Cr(III). The total Cr was determined after the reduction of Cr(VI) to Cr(III) with hydroxylamine. The concentration of Cr(VI) was determined from the difference between the concentration of total chromium and the Cr(III). Several variables such as the sample pH, concentration of TTA, salt concentration, extraction time and the sample volume were investigated in detail. Under the optimum conditions, the limit of detection of the proposed method was 0.006 μg l(-1) for Cr(III) and the relative standard deviation for six replicate determinations at 0.1 μg l(-1) Cr(III) was 5.1%. The proposed method was successfully applied for the determination of chromium species in tap water, well water, mineral water, and urine samples.