Determination of lead at trace levels in mussel and sea water samples using vortex assisted dispersive liquid-liquid microextraction-slotted quartz tube-flame atomic absorption spectrometry

Vortex-assisted restricted access-based supramolecular solvent microextraction of trace Pb(II) ions with 4-(benzimidazolisonitrosoacetyl)biphenyl as a complexing agent before microsampling flame AAS analysis

A new oxime compound, 4-(benzimidazolisonitrosoacetyl)biphenyl (BIBP) was synthesized and used as a complexing agent in this study to preconcentrate trace amounts of Pb(II) ions with vortex-assisted restricted access-based supramolecular solvent microextraction (RA/SUPRAS-LPME) method. The new complexing agent was characterized by a combination of elemental analyses, Proton Nuclear Magnetic Resonance (¹H- NMR), Carbon-13 Nuclear Magnetic Resonance (¹³C NMR) and Fourier Transform Infrared spectroscopy (FT-IR) and techniques. Extraction of the complex which was formed at pH 8.0 was done by using a supramolecular solvent phase of tetrahydrofuran (THF) and 1-decanol. A microsampling flame atomic absorption spectrophotometer was used to measure the lead ion concentrations of the extract. The method optimized and the optimum experimental conditions were found as; pH = 8, amount of the ligand 2,25 mg, supramolecular solvent volume 50 μL, sample volume 20 mL and vortex time 3 min. The limit of detection (LOD), limit of quantification (LOQ) were calculated as 0.69 μg L^-1 and 2.29 μg L^-1, respectively. Linear range was found between 15.1 μg L^-1 and 606 μg L^-1. The developed method was applied to Pb(II) determination in real samples after evaluating the accuracy by using the TMDA-53.3 fortified environmental water sample as certified reference material.

Determination of lead ions in fish and oyster samples using a nano-adsorbent of functionalized magnetic graphene oxide nanosheets-humic acid and the flame atomic absorption technique

This study aims at the functionalization of magnetic graphene oxide nanosheets and the binding of humic acid as a lead complex ligand. Graphene oxide nanosheets possess a large surface area and various carboxylic acid groups which can be activated easily by activating agents. Therefore, they are suitable to be used for the extraction of heavy metals. To have a better process of extracting lead ions, magnetic graphene oxide was used in this research. Humic acid, as a lead metal complex agent, has an amine functional group which can be bound to modified graphene oxide from one side. The process of constructing the nano-adsorbent proposed for the preconcentration of lead ions as well as its characterization was studied by infrared spectroscopy (IR), ultraviolet-visible spectroscopy (UV-visible), field emission scanning electron microscopy (FESEM), and vibrating sample magnetometry (VSM). The designed nano-adsorbent was tested to measure lead ions in simulated and real samples of sea water, fish, and oysters. The detection limit obtained in the simulated samples was 0.07 μg/L, and the linear range was 0.2-12 μg/L. The apparatus used to measure the ions was a flame atomic absorption device. In the analysis of the real samples, the values obtained through flame atomic absorption were compared with those obtained through furnace atomic absorption. The proposed technique is advantageous due to being cheap, precise, and sensitive for the trace measurement of lead ions.

Combination of vortex assisted binary solvent microextraction and QuEChERS for the determination of prothiofos, oxadiargyl, and gamma-cyhalothrin in water and pineapple samples by gas chromatography mass spectrometry

An accurate and sensitive dispersive liquid-liquid microextraction method based on binary solvents was used to enrich prothiofos, oxadiargyl, and gamma-cyhalothrin for quantification by GC-MS. The combination of two extraction solvents (binary mixture) resulted in higher extraction efficiencies compared to the single solvent extraction systems. Parameters of the binary extraction method where optimized to enhance the extraction output of the analytes. The limits of detection calculated for the analytes ranged between 0.59 and 1.6 ng/mL. Linear calibration plots of the analytes covered wide concentration ranges with R² values greater than 0.9996 and percent relative standard deviation lower than 10%. Spiked recovery experiments were performed well and wastewater at two different concentrations and satisfactory results (89-104%) were obtained. The binary solvent microextraction method was combined with QuEChERS to quantify the analytes in pineapple matrix, using matrix matching method to enhance the accuracy of the method to almost 100%.

Sensitive determination of nickel at trace levels in surface water samples by slotted quartz tube flame atomic absorption spectrometry after switchable solvent liquid-phase microextraction

In this study, switchable solvent (SS) for liquid-phase microextraction (LPME) was used as a tool to preconcentrate nickel from aqueous samples for determination by flame atomic absorption spectrometry. The SS-LPME method was optimized thoroughly to boost the absorbance signal of nickel for trace level determination. Parameters optimized included switchable solvent volume, sodium hydroxide concentration, sodium hydroxide volume, and eluent volume. The SS-LPME method enhanced the detection power by about 32-folds, and a slotted quartz tube (SQT) was used to obtain 2.6-folds increase in detection power. The combination of LPME and SQT-FAAS produced 104-folds enhancement, correlating to a limit of detection value of 1.8 μg/L. Low relative standard deviations calculated for the lowest calibration concentration indicated good repeatability for replicate measurements. Accuracy of the optimized method and its applicability to real samples was tested on two river samples. The results (85-103%) obtained from the spike recovery experiments were satisfactory.

Determination of fenazaquin in water and tomato matrices by GC-MS after a combined QuEChERS and switchable solvent liquid phase microextraction

This study presents the use of Quick Easy Cheap Efficient Rugged and Safe (QuEChERS) as an effective sample cleaning procedure and switchable solvent liquid phase microextraction (SS-LPME) as a preconcentration tool for the determination of fenazaquin by gas chromatography mass spectrometry (GC-MS) at ultratrace levels. After a thorough optimization process, 0.50 mL of switchable solvent, 1.5 mL of 1.0 M sodium hydroxide, and 15 s of vortexing were determined as optimum conditions of the SS-LPME method. The limit of detection (LOD) and limit of quantitation (LOQ) determined using the optimum method (SS-LPME/GC-MS) were 0.05 and 0.18 ng/mL, respectively. Compared with direct GC-MS determination of fenazaquin, the optimum method yielded about 800-fold enhancement in detection power of GC-MS. The method was applied to lake, irrigation canal, well, and wastewater samples. In order to test the method's applicability on fresh tomato samples, a QuEChERS method was used before applying the SS-LPME method. Matrix-matched calibration standards were used to enhance the accuracy of fenazaquin quantification in spiked tomato samples to obtain recovery results close to 100%.

Homogeneous liquid–liquid microextraction based on liquid nitrogen-induced phase separation followed by GFAAS for sensitive extraction and determination of lead in lead-adulterated opium and refined opium

Herein, we developed a novel homogeneous liquid–liquid microextraction based on liquid nitrogen-induced phase separation (HLLME-LNPS) for the extraction and determination of lead (Pb) in Pb-adulterated opium and refined opium by GFAAS analysis. In this procedure, first, 400 μl of acetonitrile (extractant) containing 7.0 μl of diethyl dithiophosphoric acid (DDTP) is injected into a sample solution and a homogeneous solution is formed. Subsequently, the homogeneous mixture is cooled using liquid nitrogen for 16 seconds. By this process, due to the difference in the freezing points of the organic and aqueous phases, the homogeneous state is broken and the Pb-DDTP species are extracted into the liquid organic phase collected on top of the frozen aqueous phase. The introduced method exhibited a good linearity with a coefficient of determination (r²) of 0.9988 and an acceptable linear range of 0.6–100 μg l⁻¹. Accordingly, the detection limit was 0.2 μg l⁻¹ (S/N = 3) for Pb ions, and a high enrichment factor was obtained. The proposed method was successfully utilized to determine trace levels of Pb in opium samples. The results of the sample analysis showed that 65% of the opium samples and 85% of the refined opium samples had much higher than expected levels of contaminating Pb, and this contamination poses a serious threat to drug users.

Herein, we developed a novel homogeneous liquid–liquid microextraction based on liquid nitrogen-induced phase separation (HLLME-LNPS) for the extraction and determination of lead (Pb) in Pb-adulterated opium and refined opium by GFAAS analysis.

An accurate and sensitive analytical strategy for the determination of palladium in aqueous samples: slotted quartz tube flame atomic absorption spectrometry with switchable liquid-liquid microextraction after preconcentration using a Schiff base ligand

This study presents a green analytical method for palladium determination by slotted quartz tube flame atomic absorption spectrometry (SQT-FAAS) following switchable liquid-liquid microextraction (SLLME). Efficient extraction of palladium was facilitated by complexation with a Schiff base ligand, synthesized specifically for this study. A three-stage thorough optimization procedure was carried out to boost the absorbance output of palladium. Complex formation was the first stage, and parameters evaluated included buffer solution pH and amount, concentration of ligand, and mixing period. The amount of switchable solvent and concentration and amount of sodium hydroxide and acid amount were optimized in the second stage. Optimization of sample and fuel flow rates and SQT parameters completed the third stage of optimization, and all optimum parameters were used to determine analytical performance of the method. The method had a broad linear dynamic range, and the calibration plots showed good linearity with R² values greater than 0.9991. The limits of detection and quantification of the SLLME-SQT-FAAS method were 15 and 50 μg/L, respectively. The precision of the method, expressed as percent relative standard deviation, was below 9.0% for all measurements. Spiked recovery results performed for a palladium electroplating bath solution gave poor results when quantified against aqueous calibration standards. Matrix matching was therefore used to improve recovery results which ranged between 97 and 105% for four different spike concentrations.

Trace determination of cobalt in biological fluids based on preconcentration with a new competitive ligand using dispersive liquid-liquid microextraction combined with slotted quartz tube-flame atomic absorption spectrophotometry

A new competitive ligand has been synthesized for the preconcentration to obtain lower detection limits by using dispersive liquid-liquid microextraction combined with slotted quartz tube-flame atomic absorption spectrophotometry (DLLME-SQT-FAAS). The proposed method is simple, eco-friendly and has high sensitivity. The preconcentration procedure was optimized on the basis of various parameters affecting the complex formation and extraction efficiency such as pH and volume of buffer solution, volume of ligand solution, mixing period, volume and type of extraction solvent, volume and type of dispersive solvent, and salt effect. Instrumental parameters were also optimized to get higher sensitivity. Under the optimum conditions, the calibration graph was linear in the range of 10-250 ng mL^-1and the resulted limits of detection and quantification (LOD and LOQ) for combined method were 4.7 and 15.7 ng mL^-1, respectively. The detection power was improved 48-fold using DLLME-SQT-FAAS method compared to conventional FAAS. The precision of the method was found to be high with a relative standard deviation of 2.5%. The accuracy of method was evaluated by recovery experiments using matrix matching study on spiked urine and blood samples. The recoveries for urine and blood samples ranged from 99.8 to 108.9% and 102.5 to 110.0%, respectively.

Trace determination of nickel in water samples by slotted quartz tube-flame atomic absorption spectrometry after dispersive assisted simultaneous complexation and extraction strategy

This study presents a new method for the determination of nickel in aqueous samples by slotted quartz tube-flame atomic absorption spectrometry (SQT-FAAS) after a dispersive assisted simultaneous complexation and extraction (DASCE) process. Synthesized ligand was directly dissolved in the extraction solvent to eliminate the complex formation step prior to the extraction. All parameters of the SQT-FAAS and DASCE method were systematically optimized to improve the detection power of nickel for trace determinations. Under the optimum experimental conditions, the optimized method (DASCE-SQT-FAAS) recorded 137-fold enhancement in detection power over the conventional FAAS. The limits of detection and quantification were determined to be 1.6 μg/L and 5.2 μg/L, respectively. The calibration plot was linear over a wide concentration range and the precision for replicate measurements was appreciably high. Nickel was not detected in five different water samples but spiked recovery tests for three samples yielded results that were close to 100%, confirming the method's accuracy and applicability to the matrices tested.

Development of an efficient and sensitive analytical method for the determination of copper at trace levels by slotted quartz tube atomic absorption spectrometry after vortex-assisted dispersive liquid-liquid microextraction in biota and water samples using a novel ligand

This study describes the determination of trace levels of copper by slotted quartz tube atomic absorption spectrometry after dispersive liquid-liquid microextraction. A ligand synthesized from the reaction of salicylaldehyde and 1-naphthylamine was used to form coordinate copper complex prior to extraction. All parameters that influence the output of complex formation, extraction, and instrumental measurement were optimized to enhance the absorbance signal of copper. Under the optimum conditions, about 104-fold enhancement in sensitivity was recorded over the conventional flame atomic absorption spectrometer, corresponding to a 0.51 ng/mL detection limit. The percent relative standard deviation calculated for the lowest concentration (4.8%) indicated high precision for the experimental procedure. Accuracy and applicability of the optimum method were determined by performing spiked recovery tests on urine, lake water, and mineral water samples. Satisfactory recovery results were obtained between 82.2 and 106.3% at four different concentrations. Matrix matching method was also performed to increase the accuracy of quantification, and the percent recovery calculated for 175 ng/mL was 105.14%.

Vortex-assisted switchable liquid-liquid microextraction for the preconcentration of cadmium in environmental samples prior to its determination with flame atomic absorption spectrometry

In this study, a switchable solvent was used to preconcentrate trace amounts of Cd from aqueous solution for its determination by flame atomic absorption spectrometry (FAAS). Protonation of N,N-dimethylbenzylamine by dry ice (solid CO₂) made it water soluble, and addition of sodium hydroxide converted it back to its original nonionic state for phase separation and subsequent extraction of Cd. A slotted quartz tube (SQT) was attached to the flame burner head to increase the residence time of Cd atoms in the light path. Under the optimum conditions, limits of detection and quantification were determined as 0.7 and 2.6 μg L^-1, respectively. Low relative standard deviations calculated from seven replicate measurements of the lowest concentration indicated high precision. Accuracy of the developed method was checked by using a standard reference material (SRM 1633c). Spiked recovery tests were also performed on lake water and wastewater samples at different concentrations to check the applicability of the developed method, and the results obtained (90-103%) established high recovery.