Dispersive Liquid-liquid Microextraction Method Research Articles

Development of microwave-assisted extraction and dispersive liquid–liquid microextraction followed by gas chromatography–mass spectrometry for the determination of organic additives in biodegradable mulch films

Organic additives are extensively used as ingredients in biodegradable mulch films. They are swiftly released into the environment, which may have an ecotoxicological impact on plant growth and development, as well as on soil microbial community abundance and function. Herein, a method based on the application of microwave-assisted extraction (MAE) and dispersive liquid–liquid microextraction (DLLME) was developed to analyze eighty organic additives by gas chromatography-mass spectrometry in poly(butylene adipate terephthalate) (PBAT) biodegradable mulch films. This was a comprehensive study, including the identification of organic additives, optimization of MAE and DLLME methods, analysis of isocyanate conversion, and evaluation of the matrix effect (ME). Under the optimized experimental conditions, this method exhibited excellent detection capabilities for organic additives, except for 5 kinds of isocyanates and their reaction products, with coefficients of determination R2 > 0.999 and lack of fit P > 0.05 in linear regression parameters. A negligible ME was observed. The relative recoveries were 93.0–109.8%, and the repeatability and reproducibility varied within the ranges of 2.06–8.76% and 2.38–10.23%, respectively. The limits of detection and limits of quantitation were 0.0008–0.0586 μg g−1 and 0.003–0.195 μg g−1, respectively. The developed method was further successfully applied to the analysis of organic additives in PBAT biodegradable mulch films from four different manufacturers. Interestingly, the Venn diagram and principal component analysis showed that different manufacturing origins display obvious characteristic differences in the organic additive types and concentrations.

Evaluation and Optimization of a New Approach on Phenol Extraction from Real Water

Phenolic compounds are hazardous industrial wastes that can contaminate real water resources. Therefore, the removal of these compounds in order to reach acceptable levels before discharging becomes challenging. In this study, a combination method between dispersive liquid-liquid microextraction (DLLME) with high-performance liquid chromatography-UV detection at 280 nm with the isocratic condition was introduced as a new approach for separating phenol content in water samples. The optimized parameters that affect the extraction efficiency, such as type of solvents, the volume of extraction and dispersive, stirring speed of centrifuge and salt concentration were evaluated using response surface methodology (RSM). A central composite design (CCD) was used to investigate the effect of four independent variables parameters, as mentioned. The recovery value on the DLLME method for the water sample is in the range of 92.31 - 114.29%. Based on the recovery obtained, the DLMME-HPLC-UV is a promising method for phenol extraction because it is simple, effective and produce a high percentage of the recovery.

A miniaturized spray-assisted fine-droplet-formation-based liquid-phase microextraction method for the simultaneous determination of fenpiclonil, nitrofen and fenoxaprop-ethyl as pesticides in soil samples.

Pesticides are a group of micropollutants that persist for a long time in the environment and pose threats to life. Much effort has been devoted to developing pre-concentration methods capable of producing samples suitable for the detection of pesticides. However, better methods are still required to detect these compounds when they are present in trace concentrations in soils. Spray-assisted fine-droplet-formation-based liquid-phase microextraction was used to prepare soil samples containing three different pesticides, fenpiclonil, nitrofen and fenoxaprop-ethyl, for subsequent analysis by gas chromatography/mass spectrometry (GC/MS). A spraying apparatus was used for the dispersion of the extraction solvent into the sample/standard solution to improve the extraction efficiency. Optimization studies were performed to lower the detection limits of these analytes and the results obtained by the application of the newly developed system were compared with those obtained using the conventional GC/MS method. A calibration curve over the range 5.0-100 μg L-1 was obtained under the optimal conditions. The limits of detection and quantification were 1.56-1.80 μg L-1 and 5.21-5.98 μg L-1 , respectively. The enhancements in detection ability over the conventional method for the three tested pesticides were 188.01, 176.96 and 517.14 for fenpiclonil, nitrofen and fenoxaprop-ethyl, respectively Recovery studies performed in soil samples were satisfactory reflecting accurate applicability of the developed method. The developed microextraction method is a time-saving and simple version of the traditional dispersive liquid-liquid microextraction method that also reduces the use of dispersive solvents.

Vortex-assisted ionic liquid-based dispersive liquid-liquid micro-extraction and spectrofluorometric determination of Rhodamine B in anti-freeze, lipstick, liquid soap, matches and red pencil core

A simple, centrifugeless vortex-assisted ionic liquid-based dispersive liquid-liquid micro-extraction method was developed for spectrofluorometric determination of Rhodamine B dye. Analytical extraction parameters including pH, type and amount of ionic liquid, salt concentration, vortex rate and time were examined and optimized. Matrix effects of potentially interfering ions and dyes were investigated and their tolerable concentrations were determined by applying optimum conditions. Detection limit and preconcentration factor were determined 0.01 μg L-1 and 30, respectively. Dynamic range of the method was linear at RhB concentration range between 0.025 and 1000 μg L-1. Relative standard deviations were 3.9% for the ten replicates measurements of 0.125 μg L-1 Rhodamine B. The method was successfully applied to different samples including anti-freezes, liquid soap, matches, red pencil core and lipsticks. RhB concentrations of liquid and solid samples were determined between 2.05 μg mL-1 and 10.05 μg mL-1 and 307 μg g-1 and 2.75 mg g-1, respectively.

Menthol-based deep eutectic solvent in dispersive liquid-liquid microextraction followed by solidification of floating organic droplet for the determination of three bisphenols with UPLC-MS/MS

An efficient dispersive liquid-liquid microextraction (DLLME) method based on the solidification of floating organic drop (SFO) has been developed for extraction of bisphenol S (BPS), bisphenol A (BPA) and bisphenol B (BPB) in canned fruit, in which green deep eutectic solvent (DES) was used as the extraction solvent. The analysis was determined by ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). All parameters affecting the extraction efficiency, including selection of DES, volume of DES, salt effect, extraction time, pH, and dispersion solvent type and volume, were investigated and optimized. The extraction efficiency of bisphenols was improved by a menthol-based DES. More importantly, the low melting point of DES makes the extracted bisphenols could be easily separated from sample solution with a syringe. This method showed good linearity (r > 0.9916) in the range of 10.0–200 ng g−1 with limits of detection (LODs) ranged from 1.5 to 3.0 ng g−1 and the limit of quantifications (LOQs) were ranged from 5.0 to 10.0 ng g−1. The recoveries of three spiked levels were ranged from 79.5% to 101% with relative standard deviations (RSDs) were lower than 4.6%. This developed method was successfully applied in bisphenols extraction of different canned fruit samples and exhibited a simple and green extraction procedure. This environmentally friendly method offers an important reference for the separation of bisphenols in food.

Sensitive Determination of Acetochlor, Alachlor, Metolachlor and Fenthion Utilizing Mechanical Shaking Assisted Dispersive Liquid-Liquid Microextraction Prior to Gas Chromatography-Mass Spectrometry.

A green, sensitive and accurate dispersive liquid-liquid microextraction (DLLME) method was used to preconcentrate four selected pesticides in dam lake water samples for determination by gas chromatography-mass spectrometry (GC-MS). Conditions of the DLLME method were comprehensively investigated and optimized according to type/volume of extraction solvent, type/volume of dispersive solvent, and type/period of mixing. The developed method was validated according to the limits of detection and quantitation, accuracy, precision and linearity. Under the optimum conditions, limit of detection values calculated for alachlor, acetochlor, metolachlor and fenthion were 1.7, 1.7, 0.2 and 7.8µg/kg (mass based), respectively. The method recorded 202, 104, 275 and 165 folds improvement in detection power values for acetochlor, alachlor, metolachlor and fenthion, respectively, when compared with direct GC-MS measurements. In order to evaluate the accuracy of the developed method, real sample application with spiking experiments was performed on dam lake water samples, and satisfactory percent recovery results in the range of 81%-120% were obtained.

A new microextraction method for trace nickel determination in green tea samples: Solventless dispersion based dispersive liquid-liquid microextraction combined with slotted quartz tube- flame atomic absorption spectrophotometry

In this study, a simple and novel analytical approach was developed in order to determine nickel at trace levels. For this purpose, a dispersive liquid-liquid microextraction (DLLME) method based on solventless dispersion of extraction solvent was developed to separate/preconcentrate nickel from aqueous solution. Combination of the DLLME method with slotted quartz tube-flame atomic absorption spectrophotometry (SQT-FAAS) lowered the analyte’s detection limit. In the DLLME method, the extraction solvent was dispersed into aqueous solution by generating fine droplets through air assisted spraying in order to reduce organic solvent consumption and avoid relative error by reducing multiple operation steps. Complexation of nickel(II) was done by using a Schiff Base synthesized from the reaction between 3,5- dibromosalicylaldehyde and 2-aminophenol. All experimental parameters were optimized comprehensively by the step-by-step approach in order to determine optimum conditions to get maximum absorbance values. Under the optimum conditions, analytical performance values were examined, and limit of detection values were obtained as 286 ng mL-1 for FAAS, 137 ng mL-1 for SQT-FAAS, 7.9 ng mL-1 for DLLME-FAAS and 3.9 ng mL-1 for DLLME-SQT-FAAS. The enhancement in detection power was obtained as 82-folds over the detection limit of the conventional FAAS system. Chinese green tea sample was used in recovery studies to check applicability and accuracy of the developed method. Recovery results were close to 100 % with low standard deviation values (n = 4) and this showed that the method appropriate for the selected matrix.

Determination of fipronil and bixafen pesticides residues using gas chromatography mass spectroscopy with matrix matching calibration strategy after binary dispersive liquid-liquid microextraction

The objective of this study was to determine bixafen and fipronil residues in domestic and industrial wastewater, soil and mint samples by binary dispersive liquid-liquid microextraction method (BDLLME) prior to gas chromatography-mass spectrometry (GC-MS). Extraction efficiency for the selected analytes was improved by optimizing the parameters such as solvent type, ratio and volume, dispersive solvent type/volume, mixing type and duration to increase overall analytical performance. Under the optimum chromatographic and extraction conditions, limits of detection values for bixafen and fipronil were determined as 7.3 and 6.1 µg L−1, respectively. Spiking experiments were performed for domestic and industrial wastewater, soil and mint samples to evaluate applicability and accuracy of the proposed method. Recovery results for the samples were calculated in the range of 89.4%–112.6% via matrix matching calibration strategy. It was determined that the detection power of GC-MS system was improved 7.8 times for bixafen and 119 times for fipronil over LOD comparisons of conventional GC-MS and B-DLLME-GC-MS systems.

Dispersive Liquid-Liquid Microextraction Based on Ionic Liquid and Spectrophotometric Determination of Bilirubin in Biological Samples

Background: An Ionic Liquid-based based Dispersive Liquid-Liquid Microextraction (IL-DLLME) method was not applied to preconcentration and determination of bilirubin. Ionic Liquids (ILs) are new chemical compounds. In recent years, Ionic Liquids (ILs) have been employed as alternative solvents to toxic organic solvents. Due to these perfect properties, ILs have already been applied in many analytical extraction processes, presenting high extraction yield and selectivity for analytes. Methods: In this study, IL-DLLME was applied to biological samples (urine and serum) for the spectrophotometric detection of bilirubin. For bilirubin analysis, the full-color development was based on the reaction with periodate in the presence of hydrochloric acid. The high affinity of bilirubin for the ionic liquid phase gave extraction percentages above 98% in 0.3 M HCl solution. Results: Several IL-extraction parameters were optimized and room temperature ionic liquid 1-butyl- 1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide and ethanol were used as extraction and disperser solution. The linear range was found in the range of 0.5-6.0 μM (0.3-3.5 μg mL-1) and the limits of detection of the proposed method was 0.5 μM (0.3 μg mL-1). The proposed method was applied for the preconcentration and separation of trace bilirubin in real urine samples. Also, the recoveries for bilirubin in spiked biological samples (urine and serum) were found to be acceptable, between 95-102%. Conclusion: The proposed IL-DLLMEapproach was employed for the enrichment and determination of trace levels of bilirubin in urine samples using NaIO4 as an oxidizing agent and Uv-vis spectrophotometric detection. The periodate oxidation of bilirubin is rapid, effective, selective, and simple to perform. The method contains only HCl, NaOI4, and an anionic surfactant. The method may be useful for economizing in the consumption of reagents in bilirubin determining. The IL-DLLMEmethod ensures a high yield and has a low toxicity no skin sensitization, no mutagenicity and no ecotoxicity in an aquatic environment since only very low quantities of an IL is required. For full-color formation, no any extra auxiliary reagents are required. Besides, the IL-DLLME technique uses a low-cost instrument such as Uv-vis which is present in most of the medical laboratories.

Application of an agitation-assisted dispersed solvent microextraction for analysis of naphthalene and its derivatives from aqueous matrices.

Agitation-assisted dispersive liquid-liquid extraction without a dispersing solvent is lately receiving considerable attention owing to the low to no solvent loss relative to its predecessor, which suffers severe extracting solvent loss. Herein, we report the application of a simple agitation-assisted dispersive liquid-liquid microextraction method, without a disperser solvent, for the extraction of naphthalene and its derivatives from aqueous solutions. Under the optimised conditions, namely, 25 μL 3:1 mixture of dichloroethane and ethylacetate with 20 s agitation, in 2-mL aqueous solutions containing 10% NaCl, the method demonstrated acceptable figures of merit: linearity-R2 ≥ 0.9914 in the concentration range 0.5-50 ng/mL, repeatability (%RSD ≤ 12.9 for n = 15) and limits of detection (0.034-0.081 ng/mL). The recoveries obtained from the spiked dam water sample were also satisfactory (94-103%). These parameters are comparable with those reported in literature, especially for dispersive liquid-liquid microextraction techniques albeit for different analytes. Despite only naphthol being detected in one of the three sampled sites, the method shows considerable promise for routine monitoring of river and dam water quality subject to accuracy validation using certified reference materials.

GREEN VORTEX-ASSISTED IONIC LIQUID-BASED DISPERSIVE LIQUID-LIQUID MICROEXTRACTION FOR ENRICHMENT AND DETERMINATION OF CADMIUM AND LEAD IN WATER, VEGETABLES AND TOBACCO SAMPLES

Objective: An eco-friendly, simple and sensitive vortex-assisted ionic liquid-based dispersive liquid-liquid microextraction method (VA-IL-DLLµE) has been proposed to enrich and determine trace levels of cadmium (Cd2+ ) and lead (Pb2+ ) ions in water, vegetables and tobacco samples, prior to its FAAS determination.
 Methods: The proposed method based on utilization of ionic liquid (IL) (1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate [HMIM][FAP]) as an extraction solvent for both ions after the complexation with 4,5-dihydroxy-3-phenylazo-2,7-naphthalenedisulfonic acid, disodium salt (Chromotrope 2R) at pH 6.5. The impact of different analytical parameters on microextraction efficiency was optimized.
 Results: In the ranges of 1.0–300 and 2.0-400 μg/ml, the calibration graphs were linear. The limits of detection were 0.3 and 0.6 μg/ml for Cd2+ and Pb2+ ions, respectively. The preconcentration factor was 100. The relative standard deviation (RSD %)<3.0%, which indicates the proposed method has high precision.
 Conclusion: The proposed VA-IL-DLLµE method was developed and applied for the estimation of Cd2+ and Pb2+ ion content in various water, vegetables and tobacco samples, and satisfactory results were obtained. The obtained recovery values showed good agreement with the certified values.

Combination of Slotted Quartz Tube Flame Atomic Absorption Spectrometry and Dispersive Liquid–Liquid Microextraction for the Trace Determination of Silver in Electroplating Rinse Bath

Although flame atomic absorption spectrometry (FAAS) is hindered by its low sensitivity for most elements, it remains a widely used analytical technique in most laboratories. This study was aimed at mitigating the low sensitivity of an FAAS system by using dispersive liquid-liquid microextraction (DLLME) to enrich silver from aqueous solution, and enhance absorbance signals with the help of a slotted quartz tube (SQT). Three major optimization steps were carried for parameters of complexation (silver-dithizone), DLLME method and SQT apparatus. The optimum parameters/variables obtained were applied to aqueous standard solutions, and the developed calibration plots were used to validate the different systems studied. The optimized method (DLLME-SQT-FAAS) recorded an enhancement factor of 98, which correlates to detection and quantification limits of 0.60 µg/L and 2.0 µg/L, respectively. The optimized method was applied to an electroplating rinse solution, and close to 100% recovery results were obtained for different spiked concentrations. These results establish that the developed method can be applied to complex samples for accurate quantification of silver.

Determination of fluoroquinolones in milk, honey and water samples by salting out-assisted dispersive liquid-liquid microextraction based on deep eutectic solvent combined with MECC.

A simple and sensitive salting out-assisted dispersive liquid-liquid microextraction method using deep eutectic solvent combined with back extraction and micellar electrokinetic capillary chromatography (SO-DLLME-DES-BE-MECC) was developed for the determination of fluoroquinolones in milk, honey and water samples. Several parameters affecting the extraction efficiency including DES volume, vortex time, centrifugation time, salt type and amount, sample pH and volume, etc. were investigated. Good linearity were obtained for fluoroquinolones in a range of 0.020-3.200μgmL-1 and 0.030-4.800μgmL-1 with LODs less than 0.010μgmL-1. The recoveries were in the ranges of 95.0-104.9%, 90.1-110.2% and 87.8-114.1% for water, honey and milk samples, respectively. The relative standard deviations for reproducibility were all below 7.6%. Under the optimized conditions, the enrichment factors for analytes were achieved in the range from 531 to 858 folds. The presented method was successfully applied for the determination of fluoroquinolones in milk, honey and water samples.

Dispersive liquid-liquid microextraction based preconcentration of selected pesticides and escitalopram oxalate, haloperidol and olanzapine from wastewater samples prior to determination by GC-MS.

A multivariate experimental design was used to attain optimum conditions of a dispersive liquid-liquid microextraction (DLLME) method for preconcentration of pesticides and pharmaceuticals for determination by gas chromatography mass spectrometry (GC-MS). Experimental design enabled parameters to be evaluated for their effects on extraction output as well as their interactive effects. The optimum parameters suggested by the design model were 200 µL of chloroform, 1.96 mL of ethanol and 40 s vortexing period. Limits of detection and quantification (LOD and LOQ) were calculated using linear calibration plots of the analytes developed in the standard concentration range of 2.0 µg/L-2.0 mg/L. Enhancement in detection power of the analytes recorded by the optimized method with respect to direct GC-MS determination (based on LOD values) was in the range of 3.6 and 539 folds. Spiked recovery experiments for municipal, medical and synthetic wastewater samples yielded low recovery results when calculated against aqueous standard solutions. Matrix matched calibration standards were used to mitigate interferences from the waste samples, and the percent recoveries obtained were close to 100%. This established accuracy and applicability of the developed method.

Dispersive Liquid-Liquid Microextraction Based Preconcentration of Selected Pesticides and Escitalopram Oxalate, Haloperidol, and Olanzapine from Wastewater Samples Prior to Determination by GC-MS.

Determination of emerging pollutants including pharmaceuticals, pesticides, industrial chemicals and hormones in different environmental samples is very important for human health. Experimental design enabled parameters to be evaluated for their effects onextraction output as well as their interactive effects. A multivariate experimental design was used to attain optimum conditions of a dispersive liquid-liquid microextraction method for preconcentration of pesticides and pharmaceuticals for determination by GC-MS. The optimum parameters suggested by the design model were 200 µL of chloroform, 1.96 mL of ethanol, and 40 s vortexing period. LOD and LOQ were calculated using linear calibration plots of the analytes developed in the standard concentration range of 2.0 μg/L-2.0 mg/L. Enhancement in detection power of the analytes recorded by the optimized method with respect to direct GC-MS determination (based on LOD values) was in the range of 3.6 and 539 folds. Spiked recovery experiments for municipal, medical, and synthetic wastewater samples yielded low recovery results when calculated against aqueous standard solutions. Matrix matched calibration standards were used to mitigate interferences from the waste samples and the percent recoveries obtained were close to 100%. This established accuracy and applicability of the developed method. The detection limits were found between 0.50 ng/mL and 37 ng/mL. An accurate, simple and sensitive analytical method was developed for the analytes.

Switchable-hydrophilicity solvent liquid-liquid microextraction versus dispersive liquid-liquid microextraction prior to HPLC-UV for the determination and isolation of piperine from Piper nigrum L.

Switchable-hydrophilicity solvent liquid-liquid microextraction and dispersive liquid-liquid microextraction were compared for the extraction of piperine from Piper nigrum L. prior to its analysis by using high-performance liquid chromatography with UV detection. Under optimum conditions, limits of detection and quantitation were found as 0.2-0.6 and 0.7-2.0μg/mg with the two methods, respectively. Calibration graphs showed good linearity with coefficients of determination (R2 ) higher than 0.9962 and percentage relative standard deviations lower than 6.8%. Both methods were efficiently used for the extraction of piperine from black and white pepper samples from different origins and percentage relative recoveries ranged between 90.0 and 106.0%. The results showed that switchable-hydrophilicity solvent liquid-liquid microextraction is a better alternative to dispersive liquid-liquid microextraction for the routine analysis of piperine in food samples. A novel scaled-up dispersive liquid-liquid microextraction method was also proposed for the isolation of piperine providing a yield of 102.9±4.9% and purity higher than 98.0% as revealed by NMR spectroscopy.

Comparison of Directly Suspended Drop Microextraction with Dispersive Liquid-liquid Microextraction Method for Extraction of Doxepin in Water and Biological Samples Prior to UV-Vis Spectrophotometer

The present research describes the use of directly suspended drop microextraction and air-assisted dispersive liquid-liquid microextraction method coupled with UV-Vis spectrophotometer for the analysis of doxepin in water and biological samples. Several important parameters which influence the extraction efficiencies of these two microextraction methods, such as the kind of extracting solvent, volume of the aqueous sample solution (donor phase), the volume of the organic extraction solvent (acceptor phase), pH of the donor phase, salt effect, extraction time, stirring rate and number of the air injection were investigated. Under the optimal conditions, the enrichment factors were above 30. The linearity of the methods has been investigated between the ranges of 0.005-1.5 and 0.003-1 µg/mL. The precisions of two methods which are based on the average relative standard deviations are lower than 6, for three different concentrations of the analyte. Finally, the proposed methods were applied for the determination of doxepin in real samples including environmental water, urine and human plasma samples under the optimal conditions and the reasonable relative recoveries were obtained.

Ultrasonic assisted dispersive liquid-liquid microextraction combined with flame atomic absorption spectrometry for determination of trace gallium in vanadium titanium magnetite

A new method of ultrasonic assisted dispersive liquid-liquid microextraction (USADLLME) combined with flame atomic absorption spectrometry (FAAS) was developed to determinate trace gallium in vanadium titanium magnetite. In the proposed approach, 1-(2-pyridineazo)-2-naphthol was selected as a complexant of gallium and chlorobenzene was chosen as extractant. The processes of complex formation and microextraction were influenced by the following factors: dosage of complexant, complex pH, extractant and its dosage, extraction temperature and time, etc. Under optimal conditions, the linear range of working curve was 0.1–1 μg/mL with detection limit of 0.07 μg/mL, and the enrichment factor of gallium was 124. 0.5 μg/mL gallium standard solution was parallelly extracted using USADLLME and determined by FAAS for 7 times and the relative standard deviation (RSD) was 13.54%. The presented method was simple, fast, sensitive and low cost, which had been successfully applied to the quantitative determination of gallium in vanadium titanium magnetite with complex matrix.

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 1.6ng/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%.

Determination of Trace Amounts of Gold in Electroplating Rinsing Bath by Slotted Quartz Tube Flame Atomic Absorption Spectrometry with Matrix Matching Calibration Strategy after Preconcentration with Vortex Assisted Dispersive Liquid–Liquid Microextraction

With the aim of mitigating the low sensitivity of the conventional flame atomic absorption spectrometer (FAAS) for gold determination, a dispersive liquid–liquid microextraction (DLLME) method was used to preconcentrate gold from the sample solution and a slotted quartz tube (SQT) was attached to the FAAS burner head to boost the residence time of the atoms in the flame. Three main optimization studies were performed to enhance the absorbance signal of gold by the FAAS system. The SQT-FAAS system was optimized based on the fuel and sample flow rates and the position of SQT on the burner head. Parameters including the pH and volume of buffer solution, volume of ligand solution, and mixing period were optimized for the efficient complexation of gold with diethyldithiocarbamate. The DLLME method was optimized based on the type and volume of dispersive and extraction solvents, type of ionic salt and mass of ionic salt. With the optimized values obtained, 1.7 and 5.6 µg/L were determined to be the method limit of detection (LOD) and limit of quantification (LOQ), respectively. The method applicability and accuracy in quantifying gold in a real sample matrix were determined by the use of spike recovery tests of electroplating rinse bath solution. Close to 100% recovery results were obtained using a matrix matching calibration method.