Speciation of butyl and phenyltin compounds using dispersive liquid–liquid microextraction and gas chromatography-flame photometric detection

The determination of thallium in the environment: A review of conventional and advanced techniques and applications

Thallium (Tl) is a potential toxicity element that poses significant ecological and environmental risks. Recently, a substantial amount of Tl has been released into the environment through natural and human activities, which attracts increasing attention. The determination of this hazardous and trace element is crucial for controlling its pollution. This article summarizes the advancement and progress in optimizing Tl detection techniques, including atomic absorption spectroscopy (AAS), voltammetry, inductively coupled plasma (ICP)-based methods, spectrophotometry, and X-ray-based methods. Additionally, it introduces sampling and pretreatment methods such as diffusive gradients in thin films (DGT), liquid-liquid extraction, solid phase extraction, and cloud point extraction. Among these techniques, ICP-mass spectrometry (MS) is the preferred choice for Tl detection due to its high precision in determining Tl as well as its species and isotopic composition. Meanwhile, some new materials and agents are employed in detection. The application of novel work electrode materials and chromogenic agents is discussed. Emphasis is placed on reducing solvent consumption and utilizing pretreatment techniques such as ultrasound-assisted processes and functionalized magnetic particles. Most detection is performed in aqueous matrices, while X-ray-based methods applied to solid phases are summarized which provide non-destructive analysis. This work improves the understanding of Tl determination technology while serving as a valuable resource for researchers seeking appropriate analytical techniques.

Extraction and determination of strobilurin fungicides residues in apple samples using ultrasound-assisted dispersive liquid-liquid microextraction based on a novel hydrophobic deep eutectic solvent followed by H.P.L.C-U.V

In this study, several novel and natural hydrophobic deep eutectic solvents (D.E.Ss) were prepared using methyl trioctylammonium chloride (M.T.O.A.C) as H.B.A and different types of straight chain alcohols as H.B.Ds. One of the D.E.Ss composed of M.T.O.A.C and n-butanol was advantageously used to develop an ultrasound-assisted dispersive liquid-liquid microextraction (U.A-D.L.L.M.E) method combined with high-performance liquid chromatography-ultraviolet detection (H.P.L.C-U.V) for the determination of some strobilurin fungicides in apple samples. Several important parameters influencing extraction efficiency were investigated and optimised, including the type and volume of extractant in ultrasound stage, sonication time, the type and volume of D.E.S, sample solution pH and effect of salt addition. Under optimal experimental conditions, the method showed good linearity with correlation coefficients (R²) of 0.9985 - 0.9991 in the linear range of 4-1500 μg kg^-1, low limits of detection of 1.5-2 μg kg^-1 and acceptable extraction recoveries in the range of 76-92%. Enrichment factor was in the range of 95-115. The proposed method was successfully applied for the extraction and preconcentration of trace fungicides in apple samples, and the results demonstrated the potential of the synthesised D.E.S for the extraction and determination of contaminants in aqueous samples.

Sensitive determination of methotrexate in plasma of children with acute leukemia using double-solvent supramolecular systemas a novel extractant for dispersive liquid-liquid microextraction

Methotrexate, as a folate antagonist, is one of the first anti-neoplasm drugs offered and is still used as an effective drug in the treatment of various malignancies. Methotrexate has a narrow treatment index and is associated with numerous side effects.In thisresearch, for the first time a double-solvent supramolecular system (DSS) was developed as an extractant without disperser solvent for dispersive liquid-liquid microextraction (DLLME). DSS - DLLME was applied to the extraction of methotrexate in plasma of children with acute leukemiaprior to itsdetermination by high-performance liquid chromatography-ultraviolet detection (HPLC - UV). In the present method, two long normal chain alcohols are mixed in a particular ratio, and then it is injected into the sample solution, which is on the magnetic stirrer. In this case, the mixture of the two alcohol changes to new supramolecular aggregate. This new supermolecule is used as an extractant, which has a higher extraction power than any of its components alone. Under the optimum conditions, the calibration graph was linear in the rage of 0.1-150 µg L^-1 with detection limit of 0.03 µg L^-1. Relative standard deviations (RSDs) including intra-day and inter-day of method based on7 replicate determinations of 100.0 µg L^-1of methotrexate were 2.6% and 4.8%,respectively. The results proved that DSS - DLLME is a sensitive, very simple, inexpensive, environmental friendly, rapid and efficient method for the preconcentration of trace amount of drugs in biological samples.

Quantification of tributyltin in seawater using triple isotope dilution gas chromatography-inductively coupled plasma mass spectrometry achieving high accuracy and complying with European Water Framework Directive limits

A triple isotope dilution GC-ICPMS method for the determination of tributyltin (TBT) was developed and validated to meet the European Water Framework Directive (WFD) requirements. The validation procedure involved the evaluation of trueness, precision (repeatability, intermediate precision), limit of detection (LOD) and limit of quantification (LOQ), stability, measurement uncertainty and traceability studies. The method is one of the most sensitive methods published to date with good accuracy, 103% average recovery in the range with %RSDs of 2.8-6.7%. A LOD value of 0.015 ng L^-1 for the TBT cation was achieved with a sample volume of 12 mL seawater. TBT was derivatized using 20 µL sodium tetraethylborate solution (0.05% NaBEt₄) to make volatile for GC-ICPMS. Measurement uncertainty was in the range of 4.8-13% which was achieved through dissolution of tributyltinchloride (TBTCl) in 1-propanol, a low-volatility solvent combined with the use of a triple isotope dilution (ID) calibration technique. Isotope dilution calibration was performed by adding ¹¹⁷Sn isotopically enriched TBT to the seawater samples. The stability test results showed that TBT concentration was stable for three months in seawater samples after passing through a 0.2 µm filter and stored in amber glass bottles at 4°C. The response surface methodology (RSM) approach was successfully implemented to provide optimal conditions for large volume injection (LVI) to obtain the maximum analytical signal. The key variables selected in the experimental design were evaporation time, evaporation temperature, carrier flow, and injection speed. This method was applied to seawater samples collected from the Bay of Izmit, Kocaeli, Turkey, where TBT pollution has not been measured yet.

Sensitive determination of deferasirox in blood of patients with thalassemia using dispersive liquid-liquid microextraction based on solidification of floating organic drop followed by HPLC-UV

Deferasirox is an oral iron chelator that has been on the market since 2005 and has been a suitable replacement for injectable chelators. It is important to check the amount of this drug in the blood of patients due to side effects. In this study, a new dispersive liquid-liquid microextraction based on solidification of floating drganic drop (DLLME - SFO) was applied to the extraction of deferasirox in the blood of patients with thalassemia prior to its analysis by high-performance liquid chromatography-ultraviolet detection (HPLC - UV). In this method, two long alcohols of the normal chain are mixed in a particular ratio, and then it is injected into the sample solution, which is on the magnetic stirrer. In this case, the mixture of the two alcohol changes to new double-solvent aggregate. This new double-solvent system is used as an extractant, which has a higher extraction power than any of its components alone. Under the optimum conditions, the calibration graph was linear in the rage of 0.2-200 μg L^-1 with detection limit of 0.06 μg L^-1. Repeatability (intra-day) and reproducibility (inter-day) of method based on seven replicate measurements of 100.0 μg L^-1of deferasirox were 3.8 % and 5.7 %, respectively. The results showed that DLLME - SFO is a very simple, inexpensive, environmental friendly, sensitive and efficient analytical method for the determination of trace amount of drugs in biological samples and suitable results were obtained.

The micro-scale synthesis of (117)Sn-enriched tributyltin chloride and its characterization by GC-ICP-MS and NMR techniques

Organotin compounds (OTCs) are among the most toxic substances ever introduced to the environment by man. They are common pollutants in marine ecosystems, but are also present in the terrestrial environment, accumulated mainly in sewage sludge and landfill leachates. In investigations of the degradation and methylation processes of OTC in environmental samples, the use of enriched isotopic tracers represents a powerful analytical tool. Sn-enriched OTC are also necessary in application of the isotope dilution mass spectrometry technique for their accurate quantification. Since Sn-enriched monobutyltin (MBT), dibutyltin (DBT) and tributyltin (TBT) are not commercially available as single species, "in house" synthesis of individual butyltin-enriched species is necessary. In the present work, the preparation of the most toxic butyltin, namely TBT, was performed via a simple synthetic path, starting with bromination of metallic Sn, followed by butylation with butyl lithium. The tetrabutyltin (TeBT) formed was transformed to tributyltin chloride (TBTCl) using concentrated hydrochloric acid (HCl). The purity of the synthesized TBT was verified by speciation analysis using the techniques of gas chromatography coupled to inductively coupled plasma mass spectrometry (GC-ICP-MS) and nuclear magnetic resonance (NMR). The results showed that TBT had a purity of more than 97%. The remaining 3% corresponded to DBT. TBT was quantified by reverse isotope dilution GC-ICP-MS. The synthesis yield was around 60%. The advantage of this procedure over those previously reported lies in its possibility to be applied on a micro-scale (starting with 10mg of metallic Sn). This feature is of crucial importance, since enriched metallic Sn is extremely expensive. The procedure is simple and repeatable, and was successfully applied for the preparation of (117)Sn-enriched TBTCl from (117)Sn-enriched metal.

Dispersive liquid-phase microextraction with solidification of floating organic droplet coupled with high-performance liquid chromatography for the determination of Sudan dyes in foodstuffs and water samples

Dispersive liquid-phase microextraction with solidification of floating organic drop (SFO-DLPME) is one of the most interesting sample preparation techniques developed in recent years. In this paper, a new, rapid, and efficient SFO-DLPME coupled with high-performance liquid chromatography (HPLC) was established for the extraction and sensitive detection of banned Sudan dyes, namely, Sudan I, Sudan II, Sudan III, and Sudan IV, in foodstuff and water samples. Various factors, such as the type and volume of extractants and dispersants, pH and volume of sample solution, extraction time and temperature, ion strength, and humic acid concentration, were investigated and optimized to achieve optimal extraction of Sudan dyes in one single step. After optimization of extraction conditions using 1-dodecanol as an extractant and ethanol as a dispersant, the developed procedure was applied for extraction of the target Sudan dyes from 2 g of food samples and 10 mL of the spiked water samples. Under the optimized conditions, all Sudan dyes could be easily extracted by the proposed SFO-DLPME method. Limits of detection of the four Sudan dyes obtained were 0.10-0.20 ng g(-1) and 0.03 μg L(-1) when 2 g of foodstuff samples and 10 mL of water samples were adopted, respectively. The inter- and intraday reproducibilities were below 4.8% for analysis of Sudan dyes in foodstuffs. The method was satisfactorily used for the detection of Sudan dyes, and the recoveries of the target for the spiked foodstuff and water samples ranged from 92.6 to 106.6% and from 91.1 to 108.6%, respectively. These results indicated that the proposed method is simple, rapid, sensitive, and suitable for the pre-concentration and detection of the target dyes in foodstuff samples.

Application of principal component analysis-multivariate adaptive regression splines for the simultaneous spectrofluorimetric determination of dialkyltins in micellar media

A new multicomponent analysis method, based on principal component analysis-multivariate adaptive regression splines (PC-MARS) is proposed for the determination of dialkyltin compounds. In Tween-20 micellar media, dimethyl and dibutyltin react with morin to give fluorescent complexes with the maximum emission peaks at 527 and 520nm, respectively. The spectrofluorimetric matrix data, before building the MARS models, were subjected to principal component analysis and decomposed to PC scores as starting points for the MARS algorithm. The algorithm classifies the calibration data into several groups, in each a regression line or hyperplane is fitted. Performances of the proposed methods were tested in term of root mean square errors of prediction (RMSEP), using synthetic solutions. The results show the strong potential of PC-MARS, as a multivariate calibration method, to be applied to spectral data for multicomponent determinations. The effect of different experimental parameters on the performance of the method were studied and discussed. The prediction capability of the proposed method compared with GC-MS method for determination of dimethyltin and/or dibutyltin.

Analysis of piroxicam in pharmaceutical formulation and human urine by dispersive liquid-liquid microextraction combined with spectrophotometry

PURPOSE

Piroxicam, is non-steroidal anti-inflammatory and analgesic agent, which is widely used in the treatment of patients with rheumatologic disorders. A new analytical approach based on the dispersive liquid-liquid microextraction (DLLME) has been developed for the extraction and determination of PX in pharmaceutical preparation and human urine.

METHODS

From the PX standard solution or solutions prepared from real samples, aliquot volumes were pipetted into centrifuge tubes and mixed with acetate buffer at pH 3.0 and NaCl solution. The contents were subjected to the DLLME, so 700 µL of methanol containing 70 µL of chloroform was injected rapidly into a sample solution. A cloudy solution was rapidly produced and the PX extracted into dispersed fine droplets. The mixture was centrifuged, thus these fine droplets of chloroform were settled. The supernatant aqueous phase was readily decanted, then the remained organic phase was diluted with ethanol and the absorbance measured at 355 ± 3 nm against a reagent blank.

RESULTS

The main factors affecting the extraction efficiency such as pH, extraction and disperser solvent types and etc. were studied and optimized systematically. Under optimized conditions, the calibration graphs were linear over the range of 0.2 to 4.8 µg/mL. The limit of detection and relative standard deviation were found to be 0.058 µg/mL and 2.83%, respectively. Relative recoveries in the spiked samples ranged from 97 to 110%.

CONCLUSION

Using the developed method PX can be analyzed in pharmaceutical formulation and human urine sample in a simpler, cheaper and more rapid manner.

Storage stability studies for tributyltin determination in human urine samples using headspace solid-phase microextraction and gas chromatography mass spectrometry

A headspace solid-phase micro-extraction (HS-SPME) method was employed in order to study the effect of storage conditions of human urine samples spiked with tributyltin (TBT) using gas chromatography and mass spectrometry. To render the analyte more volatile, the derivatization (ethylation) was made in situ by sodium tetraethylborate (NaBEt(4) ), which was added directly to dilute unpreserved urine samples and in buffers of similar acidity. The stability of TBT in human urine matrix was compared with the stability of TBT in buffer solutions of similar pH value. Critical parameters of storage conditions such as temperature and time, which affect the stability of TBT in this kind of matrix, were examined extensively. The tests showed that the stability of TBT remains practically satisfactory for a maximum of 2 days of storage either at +4 or 20°C. Greater variations were observed in the concentration of TBT in human urine samples at +4°C and lower ones at -20°C over a month's storage. The freeze-thaw cycles have negative effect on the stability and should be kept to a minimum. The results from spiked urine samples are also discussed in comparison to those acquired from buffer solutions of equal TBT concentration.

Dispersive Liquid-Liquid Microextraction Based on Solidification of Floating Organic Drop Followed by Gas Chromatography-Electron Capture Detector for Determination of Some Pesticides in Water Samples

In this study dispersive liquid-liquid microextraction based on solidification of floating organic drop (DLLME-SFO) followed by gas chromatography-electron capture detection (GC-ECD) was developed for determination of some pesticides in the water samples. Some important parameters, such as type and volumes of extraction and disperser solvent and salt effect on the extraction recovery of analytes from aqueous solution were investigated. Under the optimum conditions (extraction solvent: 1-undecanol, 15.0 μL; disperser solvent: acetone, 1.0 mL, and without salt addition), the preconcentration factors were obtained ranged from 802 to 915 for analytes. The linear ranges were from 0.05 to 100 μg L−1, and detection limits ranged from 0.05 to 0.008 μg L−1. The relative standard deviations (RSDs%, ) were between 3.2% and 6.7%. The proposed method was successfully applied to the determination of target analytes in the tap, sea, and river water samples, and satisfactory recoveries were obtained.

Determination of lead in environmental waters with dispersive liquid-liquid microextraction prior to atomic fluorescence spectrometry

This paper established a new, rapid and sensitive method for the determination of lead in water samples preconcentrated by dispersive liquid-liquid microextraction (DLLME) prior to atomic fluorescence spectrometry. Dithizone was used as the chelating agent. In the DLLME procedure, lead formed lead-dithizone complex and migrated into the carbon tetrachloride micro-droplets. Important factors that would affect the extraction efficiency had been investigated including the kind and volume of extraction solvent and dispersive solvent, sample pH, the amount of chelating agent, extraction time and centrifugation time. The results showed that the coexisting ions containing in water samples had no obvious negative effect on the determination of lead. The experimental results indicated that the proposed method had a good linear range of 0.01-100 ng mL(-1) (r(2) = 0.9990). The precision was 2.12% (RSD, n = 7) and the detection limit was 0.95 ng L(-1). Proposed method was validated with four real environmental samples and the results indicated that the proposed method was excellent for the future use and satisfied spiked recoveries were in the range of 92.9-97.4%.

Quantitation of valproic acid in pharmaceutical preparations using dispersive liquid-liquid microextraction followed by gas chromatography-flame ionization detection without prior derivatization

Dispersive liquid-liquid microextraction (DLLME), coupled with gas chromatography-flame ionization detection (GC-FID), has been successfully used for the extraction and determination of valproic acid (VPA) in pharmaceutical preparations. In the developed method, an appropriate mixture of extracting and disperser solvents was rapidly injected into an aqueous sample. Having formed a cloudy solution, the mixture was centrifuged and then the extracting solvent was sedimented at the bottom of a conical test tube. The extract was then injected into a GC system directly, without any further pretreatment. Initially, microextraction efficiency factors were optimized and the optimum experimental conditions found were as follows: tetrachloroethylene (9.0 µL) as extracting solvent; acetone (1.0 mL) as disperser solvent; 5 mL acidic aqueous sample (pH 1) without salt addition. Under the selected conditions, the calibration curve showed linearity in the range of 0.1-5.0 mg/L with regression coefficient corresponding to 0.9998. The limit of detection was found to be 0.05 mg/L. Finally, the method was applied for the determination of VPA in two different pharmaceutical preparations. A reasonable intra-assay (3.9-10.8%, n = 3) and inter-assay (5.6-11.4%, n = 3) precision illustrated the good performance of the analytical procedure. The protocol proved to be rapid and cost-effective for screening purposes.