Search

This paper presents the removal of nine potential endocrine disruptors including pesticides, pharmaceuticals and industrial chemicals using a submerged membrane bioreactor (MBR) system. Two lab-scale submerged MBRs having ceramic membranes were operated at three different sludge retention times (SRT: 15, 45, 90 days) and two hydraulic retention times (HRT: 12, 6 h) and the effects of SRT and HRT on both micropollutant removal and membrane fouling were investigated. While the effect of SRT and HRT change was observed on the removal of atrazine, fluoxetine, penconazole, no significant change was detected for the other micropollutants studied. It was determined that physicochemical properties such as distribution coefficient (LogD) and hydrophobicity of micropollutants are also effective on the removal efficiency of micropollutants. High removal efficiencies ([Formula: see text] 97.5%) were observed for hydrophobic pollutants (logD 3.2) except for penconazole (72.1%) and for hydrophilic pollutants (logD 3.2) except for atrazine (42.5%). Membrane fouling was significantly affected by different operational parameters applied, with the slowest fouling occurring at 45 days of SRT and 12 h of HRT. However, micropollutant addition did not have a significant effect on membrane fouling. It has been shown that the simultaneous and effective treatment performance for micropollutants makes the membrane bioreactor system a promising wastewater treatment process.

This study was aimed at developing a double-monitoring detection system for measuring the TAC (total antioxidant capacity) of apple juice samples. The conventional CUPRAC (cupric ion reducing antioxidant capacity) assay was coupled to high-performance liquid chromatography–ultraviolet (HPLC–UV) and digital image-based colorimetric detection systems. In the CUPRAC assay, a chromogenic copper(II)-neocuproine (Cu(II)-Nc) reagent was used to oxidize the antioxidants, which is further reduced by the antioxidants to a yellow-colored copper(I)-neocuproine (Cu(I)-Nc) chelate having maximum absorption at 450 nm. The yellow-colored samples were measured by HPLC–UV and digital image-based colorimetric detection systems. Parameters of the HPLC–UV system were optimized to obtain a sharp and transient peak at 450 nm analytical wavelength. Under the optimum experimental conditions, the detection limits calculated for ascorbic acid using the HPLC–UV and digital image-based colorimetric detection systems were 0.28 and 0.70 mg/L, respectively. Satisfactory results (95.6–102%) were calculated for apple juice samples spiked at different concentrations for both detection systems, and very low (

Binary solvent microextraction (BSME) coupled to gas chromatography–mass spectrometry (GC-MS) was employed to determine 4-n-nonylphenol in domestic wastewater and detergent. The developed BSME meth...

This study employed two batch-type bioreactors for the treatment of twelve environmental contaminants with the potential to disrupt the normal function of the endocrine system. The contaminants included bisphenol A, two alkylphenols, two hormones, six organochlorine pesticides and one organophosphate pesticide. Synthetic domestic wastewater was prepared daily in the laboratory and fed to the bioreactors. The bioreactors were operated at two different sludge retention times and the parameters used to evaluate their performance were chemical oxygen demand, ammonium, orthophosphate, pH, temperature, dissolved oxygen and mixed liquor suspended solids. Upon reaching optimum operational conditions, the analytes were spiked into the bioreactors and the removal efficiencies were calculated with respect to the influent concentration. Satisfactory removal efficiencies (> 88%) were recorded for all twelve analytes as validated by the decline in ammonium, chemical oxygen demand and orthophosphate amounts. Sludge samples from the two bioreactors were analyzed at the end of the study, but none of the analytes was detected according to the detection limit of the method. The simple and efficient bioreactor system reported in this study was successfully used to remove twelve different endocrine disrupting compounds from wastewater, and this can be easily replicated with low financial cost.

This study presents the preconcentration of diflufenican and azaconazole from domestic wastewater samples by using dispersive solid-phase extraction (dSPE) for determination by gas chromatography-mass spectrometry (GC-MS). Stearic acid-coated magnetic nanoparticles were used as adsorbents for dSPE method. In order to maximize the efficiency of the extraction process, parameters such as magnetic nanoparticle (MNP) type and amount, eluent type and volume, mixing type, and mixing period were all optimized. The linear range obtained for azaconazole and diflufenican was 7.50-500 ng/mL and 7.50-750 ng/mL, and their limits of detection/quantification (LOD/LOQ) were calculated as 1.3/4.3 ng/mL and 1.4/4.7 ng/mL, respectively. By comparing the LOD values of direct GC-MS and the developed dSPE method, azaconazole and diflufenican recorded approximately 35 and 38 folds enhancement in detection power. Recovery experiments with domestic wastewater were carried out to certify the proposed method's accuracy and applicability. By using the matrix matching calibration strategy, the good percent recovery results between 98 and 105% were obtained.

Dispersive liquid-liquid microextraction (DLLME) is a useful preconcentration technique but its direct application is limited to aqueous samples. Two pretreatment methods for solid samples, QuEChERS (quick easy cheap efficient rugged and safe) and a standard method, were used to isolate four polycyclic aromatic hydrocarbons (PAHs) from the sample matrix. However, since these methods result in analyte dilution, DLLME was used to augment them by concentrating the analytes from 8.0 mL of sample into 150 ��L of 1,2-dichloroethane. Under the optimum conditions, the instrumental detection limit was enhanced by approximately 100-fold for chrysene, benzo[a]pyrene, benz[a]anthracene, and benzo[k]fluoranthene with corresponding detection limits of 29, 29, 30, and 28 ng/L, respectively. The precision of the method based on inter-analyst and inter-day analysis yielded relative standard deviations less than 9.0 and 4.0%, respectively. The optimized method was applied to snail samples spiked at 5.0, 10, 20, and 50 ng/g and the recoveries were nearly 100%. Matrix matched standards were also used to determine the recoveries; the results did not vary significantly from the direct calibration recoveries.

Atrazine is a triazine herbicide widely used for the control of weeds. Physico-chemical characteristics of atrazine such as long half-life, low vapor pressure, low pKa, and high mobility have led to its persistence in the environment. Thus, atrazine may accumulate and exceed acceptable levels in terrestrial ecosystems, groundwater, and surface water bodies. Several studies related to atrazine determination have been performed as the first step to monitor its presence in the environment. In addition, various treatment strategies have been developed for the efficient removal of atrazine from wastewater. This review summarizes the primary methods for atrazine determination, focusing upon selective and sensitive methods that achieve low detection limits (ng/L). In addition, several treatment strategies that recorded removal efficiencies from 7.0 to 99.70% for atrazine are discussed.

Pharmaceutical products are widely consumed globally and are commonly found in wastewaters as a result of constant excretion and disposal into sewers. The present study proposes an efficient binary solvent dispersive liquid-liquid microextraction (BS-DLLME) method that was developed for preconcentration of 7 nervous system drug active compounds from aqueous media for their determination at trace levels by gas chromatography-mass spectrometry. The drug analytes included 3 antidepressants, 2 antipsychotics, 1 antiepileptic, and 1 antidementia. Optimum conditions of the BS-DLLME method were acquired by univariate optimization of parameters including type of binary solvents, ratio of binary solvents, type of disperser solvent, volume of binary solvents, and volume of disperser solvent. Detection and quantification limits were calculated in the range of 0.28 to 6.5 µg/L. Municipal wastewater, medical wastewater, synthetic domestic wastewater, and lake water were utilized as real samples in spike recovery experiments; and the results (94-106%) indicated the method's applicability and accuracy at quantifying the analytes in complex matrices. Environ Toxicol Chem 2021;40:1570-1575. © 2021 SETAC.

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 a...

This study employed QuEChERS as an efficient sample clean-up and extraction method for the determination of pyridaphenthion in aqueous, fruit and vegetable samples by high performance liquid chroma...

Quorum quenching using different kinds of inhibitors is a new subject of research that is used for biofilm prevention in wastewater treatment membrane systems. In this study, three natural compounds, namely tea, coffee and vanillin, were tested in order to evaluate their possible effects on wastewater sludge characteristics in a batch type aerobic reactor. The parameters evaluated included the soluble microbial products (total soluble microbial products, protein and carbohydrate fraction of soluble microbial products), extracellular polymeric substance concentrations (total extrapolymeric substances, protein and carbohydrate fraction of the extrapolymeric substances), floc size, zeta potential, sludge volume index and capillary suction time. The effects of these plant based compounds upon the quorum sensing N-butyryl-L-homoserine lactone signal were also investigated using gas chromatography - mass spectrometry (GC-MS) under optimized conditions. The results indicated different effects for each natural compound upon the sludge characteristics. The role of these natural compounds as quorum quenchers in the batch-type aerobic reactor was inconclusive due to their effects on extraction outputs. Understanding the effect of quorum quenchers on sludge characteristics is important and recent studies have been aimed at preventing biofilm formation in membrane bioreactors.

Antarctica has seen an increase in scientific research and tourism, and anthropogenic activities such as incineration of waste products and fuel combustion for energy and transportation are potential contamination sources to the ecosystem. Polycyclic aromatic hydrocarbons are common products of incomplete combustion of organic compounds and could be among accumulating contaminants in Antarctica. Thus, this study sought to develop a sensitive dispersive liquid-liquid microextraction method for the determination of 15 polycyclic aromatic hydrocarbons by gas chromatography mass spectrometry. Parameters that were relevant to the extraction method were carefully optimized and validated using aqueous standard solutions. The optimum method recorded detection limits in the range of 0.20-6.1 µg/L for the analytes. Spike recovery experiments were carried out on artificial seawater, rock-soil, and moss samples, using matrix matching calibration to mitigate effects of the sample matrices. The samples analyzed included seawater, lake, rock-soil, moss, seaweed, and feces samples all collected from the Horseshoe and Faure Islands in Antarctica. The percent recovery results obtained for the samples spiked at different concentrations ranged between 86 and 115%.

Background: Epilepsy is a neurologic condition that is occurs globally and is associated with various degrees of seizures. Levetiracetam is an approved drug that is commonly used to treat seizures in juvenile epileptic patients. Accurate quantification of the drug’s active compound and determining its stability in the stomach after oral administration are important tasks that must be performed. Results & methodology: Levetiracetam was extracted from drug samples and quantified by gas chromatography mass spectrometry using calibration standards. Stability of levetiracetam was studied under various storage conditions and in simulated gastric conditions. The calibration plot determined for levetiracetam showed good linearity with a coefficient of determination value of 0.9991. The limits of detection and quantification were found to be 0.004 and 0.014 μg·ml-1, respectively. The structural integrity of levetiracetam did not change within a 4-h period under the simulated gastric conditions, and no significant degradation was observed for the different storage temperatures tested. Discussion & conclusion: An accurate and sensitive quantitative method was developed for the determination of levetiracetam in drug samples. The stability of the drug active compound was monitored under various storage and gastric conditions. The levetiracetam content determined in the drug samples were within ±10% of the value stated on the drug labels.

A sensitive, accurate and simple analytical method was developed to determine cadmium by slotted quartz tube-flame atomic absorption spectrometry after preconcentration/extraction with polystyrene coated magnetic nanoparticles based dispersive solid phase extraction. The surface of Fe

This study utilized switchable solvent liquid-phase microextraction (SS-LPME) to enrich eleven nervous system active pharmaceutical ingredients (APIs) from aqueous samples for their determination at trace levels by gas chromatography mass spectrometry. The analytes selected for the study included APIs utilized in antidepressant, antipsychotic, antiepileptic, and anti-dementia drugs. Parameters of the microextraction method including switchable solvent volume, concentration and volume of the trigger agent (sodium hydroxide), and sample agitation period were optimized univariately to boost extraction efficiency. Under the optimum conditions, the detection limits calculated for the analytes were in the range of 0.20-8.0 ng/mL, and repeatability for six replicate measurements as indicated by percent relative standard deviation values were below 10%. Matrix matching calibration strategy was used to enhance quantification accuracy for the analytes. The percent recovery results calculated for the eleven analytes ranged between 86 and 117%.

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 ...

In this study, a novel analytical method was developed for the determination of trace level bisphenol A (BPA) in bottled water and wastewater samples. Switchable solvent-based liquid phase microextraction (SSLPME) was combined with quadrupole isotope dilution (ID4) to improve the accuracy/precision and lower the detection limit. In the first step of this study, double isotope dilution (ID2), triple isotope dilution (ID3), quadrupole isotope dilution (ID4), standard addition-double isotope dilution (SA-ID2) and standard addition-triple isotope dilution (SA-ID3) were applied for the determination of BPA to check their effectiveness in terms of accuracy and precision. ID4 was selected as the best strategy to quantify the analyte. In order to improve the detection power, a microextraction strategy was adopted for the system and the developed combination called SSLPME-ID4-GC-MS was successfully applied for the trace quantification of BPA. Under the optimum conditions, percent recovery results were calculated as 99.4 ± 0.7% and 99.9 ± 0.8% for bottled water and wastewater samples spiked with BPA at 223.8 and 169.9 ng g−1, respectively.

In this study, a binary mixture in dispersive liquid-liquid microextraction was used for the preconcentration and determination of selected pesticides, pharmaceutical and hormone by GC-MS. A Box-Behnken experimental design was used to optimize the amounts of binary mixture, dispersive solvent and salt. The optimum parameters obtained were dichloromethane/1,2-dichloroethane binary mixture (200 µL), ethanol (2.0 mL) and potassium nitrate (1.0 g). Analytical performance of each analyte was determined under the optimum conditions and the lowest and highest detection limits calculated were 0.43 and 5.9 ng/mL. Low relative standard deviations were obtained even in the lowest concentrations in linear calibration plots, signifying high precision for the sample preparation procedure and instrumental measurement. Accuracy of the developed method and applicability to real samples was tested on well, lake, hospital and municipal wastewater. The percent recoveries acquired at different spiked concentrations were satisfactory (89%-108%), validating the accuracy of the method for the quantification of the analytes in the selected matrices.

This study presents the optimisation of a dispersive liquid-liquid microextraction method for the preconcentration of etrimfos and tebuconazole before gas chromatography mass spectrometry (GC-MS) d...

In this study, an experimental design was used to optimize dispersive liquid–liquid microextraction for the extraction/preconcentration of micropollutants that have endocrine disruption potential, for the determination by gas chromatography–mass spectrometry. The analytes were selected from endocrine disrupting chemicals, such as pesticides, phthalates, hormones, alkyl phenols and pharmaceuticals. The most influential parameters of the extraction method determined in a pre-optimization step were included in the design model to determine their optimum amounts and to evaluate their interactions in a series of combinations. The design model predictor was used to obtain optimum experimental values, with which analytical performance of each analyte was determined with calibration plots. Deuterated bisphenol A (BPA D16) was added as an internal standard to all samples and calibration standards to improve the precision of the results. The limits of detection for analytes ranged between 0.10 and 16 µg/L. The developed method was applied to synthetic and municipal wastewater samples, and the results obtained from spiked recovery tests ranged between 79 and 113%. These results confirmed the applicability of the method for the selected sample matrices. The complex nature of the samples tested in this study affected the recovery of analytes. However, matrix matching calibration was employed to overcome the matrix effects and this improved the recovery results.

In this study, eight hazardous aromatic amine products of azo dyes were simultaneously determined by GC–MS in wastewater and textile samples after preconcentration with an accurate and sensitive binary solvent dispersive liquid-liquid microextraction method. A univariate optimization procedure was used to determine the most influential experimental parameters and a multivariate optimization was used to determine optimum amounts of each parameter. A model developed from experimented results was used to ascertain the effects of main parameters and their interaction effects with each other. The optimum parameters obtained from the model were chloroform (100 μL), 1,2‑dichloroethane (100 μL), ethanol (2.0 mL) and vortex (15 s). The limits of detection (LOD) and quantification (LOQ) of the analytes determined under optimum conditions ranged between 0.16–1.4 μg/L and 0.53–4.6 μg/L, respectively. The calibration plots of the analytes were linear (R2 > 0.9991) over a broad range and the %RSDs were below 10%. The method was applied to wastewater and textile samples as a test of the method's applicability and accuracy. The percent recovery obtained for wastewater by the standard calibration method was appreciable (85–109%), but procedural matrix matching was used to improve the percent recovery for the textile sample (85–103%).

This study presents a Fenton digestion method for milk samples based on UV irradiation for cadmium determination using flame atomic absorption spectrometry. The method was developed as an alternative to microwave digesters, using very basic apparatus and easy to acquire chemicals. Fenton digestion process was performed by the help of citric acid coated magnetic nanoparticles. Optimum conditions of the digestion process were applied to milk samples to evaluate analytical performance of the method. Limit of detection and limit of quantification values calculated for cadmium in milk were 0.53 and 1.8 mg/L, respectively. The method was applied to three different milk samples to validate the method's suitability and accuracy. Percent recovery values calculated for the samples spiked at two different concentrations ranged between 86 and 111%. Due to differences in the content of the spiked and control/standard milk samples, exact matrix matching calibration strategy using the same brand of milk sample in the preparation of calibration standard was employed and the accuracy of cadmium quantification was greatly enhanced (≈100%).

Six arsenic species, namely arsenite (AsIII), arsenate (AsV), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenobetaine (AsB) and arsenocholine (AsC) were speciated using a combination of high-performance liquid chromatography and inductively coupled plasma mass spectrometry (HPLC–ICP-MS). Under optimum chromatographic conditions, six arsenic species were well separated, and the performance of the combined system (HPLC–ICP-MS) for the species was determined. The limits of detection were calculated in the range of 0.14–0.29 ng/mL, and the corresponding quantification limits ranged between 0.45 and 0.97 ng mL−1 for the species. Spike recovery experiments performed on rice samples were used to validate the method’s applicability to complex matrices. The recovery results calculated ranged between 93 and 109%, validating the method’s applicability. Triplicate measurements for all spiked samples recorded percent relative standard deviation values below 10%.

Traditional copper coffee pots are widely used in these modern times and daily consumption of coffee brewed in overused/old pots increases the risk of copper ingestion. This study employed a green switchable solvent–based liquid-phase microextraction (SS-LPME) method to isolate and preconcentrate copper from water boiled in coffee pots. Copper was determined by a flame atomic absorption spectrometry (FAAS) system coupled with a slotted quartz tube (SQT). 1,5-Diphenylcarbazone was added to aqueous samples to form a complex with copper before the extraction step. Box-Behnken experimental design was applied to select optimum conditions of the extraction method that were used to validate the analytical method. The limits of quantification and detection of the optimized SS-LPME-SQT-FAAS method were determined as 9.1 and 2.7 μg/L, respectively. Water samples boiled in traditional coffee pots were spiked at different concentrations and analyzed to ascertain the method’s accuracy and applicability to real samples. Satisfactory recovery results obtained in the range of 92–107% established good accuracy, and percent relative standard deviations lower than 8.0% also proved high precision.

Traditional copper coffee pots are widely used in these modern times and daily consumption of coffee brewed in overused/old pots increases the risk of copper ingestion. This study employed a green switchable solvent-based liquid-phase microextraction (SS-LPME) method to isolate and preconcentrate copper from water boiled in coffee pots. Copper was determined by a flame atomic absorption spectrometry (FAAS) system coupled with a slotted quartz tube (SQT). 1,5-Diphenylcarbazone was added to aqueous samples to form a complex with copper before the extraction step. Box-Behnken experimental design was applied to select optimum conditions of the extraction method that were used to validate the analytical method. The limits of quantification and detection of the optimized SS-LPME-SQT-FAAS method were determined as 9.1 and 2.7 μg/L, respectively. Water samples boiled in traditional coffee pots were spiked at different concentrations and analyzed to ascertain the method's accuracy and applicability to real samples. Satisfactory recovery results obtained in the range of 92-107% established good accuracy, and percent relative standard deviations lower than 8.0% also proved high precision.

This work presents a sensitive and rapid analytical method for the determination of oxcarbazepine in human plasma and urine samples. A vortex-assisted switchable hydrophilicity solvent-based liquid phase microextraction (VA-SHS-LPME) was used to preconcentrate oxcarbazepine from the samples before the determination by gas chromatography mass spectrometry. The switchable hydrophilicity solvent was synthesized by protonating N,N-dimethylbenzylamine with carbon dioxide to make it totally miscible with an equivalent volume of water. Parameters of the VA-SHS-LPME method including volume of switchable hydrophilicity solvent, concentration/volume of sodium hydroxide and vortex period were systematically optimized. Under the optimum conditions, good linearity ranging from 27.03 to 353.47 μg/kg was obtained for the analyte. Limit of detection and quantitation values were found to be 6.2 and 21 μg/kg (mass base), respectively. The relative standard deviation was calculated as 6.9% for six replicate measurements of the lowest concentration of the calibration plot. Satisfactory recovery results were calculated in the range of 97-100% for human plasma and urine samples spiked at five different concentrations.

Background Determination of emerging pollutants including pharmaceuticals, pesticides, industrial chemicals and hormones in different environmental samples is very important for human health. Objective Experimental design enabled parameters to be evaluated for their effects onextraction output as well as their interactive effects. Method 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. Results 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. Conclusions 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. Highlights 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.

In this study, a switchable solvent-based liquid-phase microextraction method was developed to preconcentrate selected pesticides from tap water and wastewater matrices for determination by gas chromatography-mass spectrometry. A thorough optimization process was performed for prominent extraction parameters such as switchable solvent amount, concentration/amount of sodium hydroxide, salt type and mixing period. Optimum parameters obtained at the end of the optimization process were applied to aqueous standard solutions to validate the method. The linear dynamic ranges of all four analytes were appreciably wide with coefficient of determination values greater than 0.9997. The limits of detection and quantification (LOD and LOQ) were calculated for the analytes in the ranges of 0.38-2.0 ng/mL and 1.3-6.5 ng/mL, respectively. Spiked recovery experiments were used to validate the accuracy of the developed method and to determine the performance of the method in different sample matrices. Tap water, municipal wastewater and medical wastewater were spiked at three different concentrations and analyzed under the method's optimum conditions. The percent recovery results calculated for the samples were in the range of 79-107%, and this validated the method's accuracy and applicability to complex matrices such as municipal and medical wastewater samples.

This study describes the development of a sensitive and accurate dispersive liquid–liquid microextraction strategy for the preconcentration and determination of selected pesticides in wastewater and lake water samples by gas chromatography–mass spectrometry. Determination of these pesticides at high accuracy and precision is important because they can be still be found in environmental samples. The type of extraction solvent and type of disperser solvent were optimized using the univariate approach. Furthermore, a Box–Behnken experimental design was used to set up a working model made up of 18 combinations of three variables, tested at three levels. The parameters fitted into the design model were volume of extraction solvent, disperser solvent volume, and mixing period. Analysis of variance was used to evaluate the experimental data to determine the significance of extraction variables and their interactions, before selecting optimum extraction conditions. The method was then applied to aqueous standard solutions between 2.0 and 500 μg L−1, and the limit of detection (LOD) and quantification (LOQ) values obtained for the analytes were between 0.37–2.8 and 1.2–9.4 μg L−1, respectively. The percent recoveries were calculated in the range of 92–114 and 96–110% for wastewater and lake water, respectively. These results validated the accuracy and applicability of the method to the selected matrices.

This study presents the coupling of slotted quartz tube with flame atomic absorption spectrometry for the determination of cadmium after preconcentration with dispersive liquid–liquid microextraction. A bipyridine ligand was used to form covalent cadmium complex, and the formation yield was increased by optimizing parameters such as pH/amount of buffer solution and ligand concentration. Parameters that influence the extraction output and slotted quartz tube efficiency were also optimized to increase the sensitivity. The optimization steps added up to give about 135 times increased sensitivity in comparison to the conventional flame atomic absorption spectrometry. The limits of detection and quantification obtained under optimum experimental conditions were 0.31 and 1.04 µg L−1, respectively. Applicability of the method was tested on lake water, municipal wastewater and onion samples spiked at different concentrations. Percentage recoveries were found to be between 84 and 105% for the samples, and matrix matching was used to obtain 98.6% recovery for onion spiked at 20 µg L−1.

Quantitative determination of contaminants in environmental samples is usually hampered by low analyte recovery which results from the complex nature of the sample matrix. This study presents the application of a developed dispersive liquid–liquid microextraction method for the determination of 12 analytes in environmental samples including sea water, fresh water (lake, well and tap water), brackish water and soil samples. Matrix matched standards were used to compensate for the low analyte recovery recorded by the conventional calibration method. The effect of matrix dilution on analyte recovery was also tested. All matrix matched and matrix diluted spiked recoveries were done concurrently with calibration standards prepared in deionized water. Percent recoveries recorded for the analytes according to deionized water calibration standards ranged between 66 and 137%. Matrix matching and matrix dilution yielded close to 100% recovery results, but the later lowered the detection limit according to the dilution factor.

In this study, an effective Fenton digestion procedure based on UV irradiation was used to facilitate copper determination in human blood serum by flame atomic absorption spectrometry. The method was based on the degradation of blood serum samples using free hydroxyl radicals that were generated from the mixture of iron magnetic nanoparticles and hydrogen peroxide under UV irradiation. The digestion procedure was carried out using a simple, multi-functional lab-made UV irradiation reactor. Under the optimal experimental conditions, detection and quantification limits (LOD and LOQ) of the digestion system for copper were found to be 0.15 and 0.51 mg/L, respectively. Different blood serum samples were taken through the optimum procedure to validate the digestion method. Satisfactory percent recoveries (93–107%) were obtained with high repeatability for replicate digestions. This promising digestion method is simple, uses very low sample and reagent volumes, and can therefore be considered as an alternative procedure to microwave digestion.

Hydride generation atomic absorption spectrometry was used as a simple, sensitive, and economical method for the determination of cadmium at trace levels. This study includes a stepwise optimization of all parameters that have an impact on the production, transport, and atomization of cadmium hydride for rapid determination due to the unstable nature of the hydride produced. The cell temperature for atomization, pump period, and flow rate of carrier gas were varied, and the best conditions were defined to obtain lower detection limits. In addition, the acid and sodium borohydride concentrations were optimized since they directly affect the production of the cadmium hydride. Under optimum experimental conditions, the hydride generation efficiency was greatly enhanced to record optimized analytical signals. The accuracy of the method was determined by the analysis of a certified reference material, and the results were in good agreement with the certified value. A linear dynamic range for cadmium wa...

In this study, dispersive liquid–liquid microextraction was systematically optimized for the preconcentration of nickel after forming a complex with diphenylcarbazone. The measurement output of the flame atomic absorption spectrometer was further enhanced by fitting a custom-cut slotted quartz tube to the flame burner head. The extraction method increased the amount of nickel reaching the flame and the slotted quartz tube increased the residence time of nickel atoms in the flame to record higher absorbance. Two methods combined to give about 90 fold enhancement in sensitivity over the conventional flame atomic absorption spectrometry. The optimized method was applicable over a wide linear concentration range, and it gave a detection limit of 2.1 µg L−1. Low relative standard deviations at the lowest concentration in the linear calibration plot indicated high precision for both extraction process and instrumental measurements. A coal fly ash standard reference material (SRM 1633c) was used to determine the accuracy of the method, and experimented results were compatible with the certified value. Spiked recovery tests were also used to validate the applicability of the method.

Dispersive liquid–liquid microextraction was coupled with quadruple isotope dilution mass spectrometry for the sensitive and accurate determination of parathion methyl in water. The two methods were complementary to each other, with DLLME preconcentrating the analyte for trace determination, and ID4MS maintaining the integrity of the method's accuracy and precision. An experimental design was used to optimize the extraction process. The results from the design were evaluated with the analysis of variance to determine the statistical significance of the main factors of extraction and interaction effects of these factors. A three-point calibration blend and sample blend were prepared gravimetrically by spiking with isotopically labelled parathion methyl. All four blends were left to equilibrate for three hours, after which they were preconcentrated under the optimum extraction conditions. The percent recovery recorded by this method was 99.9%, and the percent relative standard deviation was 0.32%. These results validated the accuracy and precision of the combined method.

This study presents a switchable solvent liquid phase extraction (SS-LPE) method for the enrichment of four pesticides, and their subsequent determination by gas chromatography mass spectrometry (GC–MS). Box-Behnken experimental design was utilized to attain optimum conditions of the SS-LPE method by navigating a design model developed according to parameter effects and their interactions. Significant parameters were evaluated using analysis of variance (ANOVA), and the optimum variables were selected from a list of combinations presented by the model predictor. The detection limits calculated for chlorthiamid, ethyl parathion, penconazole and fludioxonil were 0.58, 0.73, 0.33 and 0.28 ng/mL. These detection limits correlated to enhancement factors in the range of 60–150 folds. Repeatability based on intra-day and inter-day analysis produced percent relative standard deviations below 10%, a good indicator of high precision. Well water, tap water and lake water samples were employed as real sample matrices to test the trueness of the method and its applicability. The recovery results calculated for the samples spiked at different concentrations were satisfactory (90–105%), and this validated the method for real sample applications.

A new analytical method based on dispersive liquid–liquid microextraction with gas chromatography and mass spectrometry has been optimized for the simultaneous determination of paclobutrazol and triflumizole in tap water and wastewater samples. A two-level, full-factorial design that allowed the study of main effects and factor interactions was applied to analyze the influence on microextraction process by chloroform, ethanol, potassium iodide and hand shaking. The extraction conditions selected were 200 μL of chloroform, 3.0 ml of ethanol, 2.0 g of potassium iodide and 15 s of hand shaking. The limits of detection obtained for triflumizole and paclobutrazol under optimum conditions were 0.97 and 0.29 ng mL−1, respectively. Calibration plots of both analytes were linear over a wide concentration range, and good precision was observed for replicate measurements. Applicability and accuracy of the method were determined by performing spiked recovery tests. Appreciable recovery results were obtained for municipal wastewater and matrix matching was used to obtain close to 100% recovery for tap water. This article is protected by copyright. All rights reserved

This study describes the development of a dispersive liquid-liquid microextraction method for the extraction of cadmium and its determination by hydride generation atomic absorption spectrometry. The extraction method served as a clean-up of analyte from its matrix and also concentrated it to get lower detection limits. The hydride generation system was optimized to obtain high cadmium hydride generation efficiency and its transport to the quartz tube atomizer for atomization. Under the optimum experimental conditions, the limits of detection and quantification were 4.2 ng L− 1 and 14.1 ng L− 1, respectively. Sensitivity was enhanced about 10,000 folds if compared with conventional FAAS system. The calibration showed good linearity over a wide range and the low relative standard deviations indicated high precision for the extraction process and instrumental readings. The accuracy of the method was validated by the agreement of experimented results to the value of a wastewater certified reference material (EU-L-2). Appreciable recovery results were obtained for wastewater spiked at different concentrations.

The bacterial communication through signaling molecules termed quorum sensing has gained a lot of attention due to its applicability to different fields of study. Quorum sensing regulates several bacterial activities such as biofilm formation, antibiotic resistance, bioluminescence and bacterial virulence. These coordinated activities are only realized when the bacterial population reaches a high population density. The signaling molecules used in quorum sensing occur at very low concentrations which call for very sensitive methods for their identification and characterization. Many studies have been performed on the use of inhibitors in attempt to disrupt quorum sensing and consequently alleviate its negative effects. This article gives a description of the types of auto-inducers involved in quorum sensing and the fields of study they greatly affect especially the environmental one. It also covers types of analytical sample preparation and detection methods, and different types of inhibitors used for quorum quenching.

A sensitive, reliable, simple and rapid analytical method was developed for the determination of arsenite [As(III)], arsenate [As(V)] and arsenobetaine (AsB) species using ion chromatography combined with inductively coupled plasma-mass spectrometry (IC-ICP-MS). Inorganic and organic arsenic species were separated with an anion exchange column (Dionex AS9) and a 50 mM sodium bicarbonate mobile phase (pH 10) at a flow rate of 1.0 mL min−1. %RSD values were found to be lower than 5.1% for all arsenic species. The limits of detection (LOD) obtained for As(III), As(V) and AsB were 16.5 ng L−1, 14.1 ng L−1 and 6.2 ng L−1, respectively. The developed analytical method was tested using AsB certified reference material (NMIJ CRM 7901-a), and spring water certified reference material (UME CRM 1201) for accuracy check. This method was applied for the quantitative determination of arsenic species in different water samples and chicken samples as a solid matrix.

Determination of trace amount of copper in environmental samples is necessary due to its toxic properties and dangers to living organisms. Dispersive liquid-liquid microextraction (DLLME) was coupled with slotted quartz tube (SQT) to lower the detection limit for copper using flame atomic absorption spectrometry (FAAS). Parameters affecting the formation of copper-ligand complex, DLLME efficiency and SQT output were systematically optimized to improve copper detection signal. The SQT-FAAS, DLLME-FAAS and DLLME-SQT-FAAS systems were 2, 42 and 79 times, respectively, more sensitive than the conventional FAAS system. The limit of detection (LOD) and quantitation (LOQ) values obtained for the combined methods (DLLME-SQT-FAAS) were calculated as 0.7 and 2.2 μg L − 1 , respectively. The method recorded appreciable recoveries for all samples tested (78%–99%), and experimental results of a certificated references material (EU-L-2) agreed with the certified value.

A photochemical vapor generation system with sonication assisted batch type gas-liquid separator was optimized to improve the sensitivity, precision and accuracy of nickel determination by atomic absorbance spectrometry. The inefficient nebulizer sample introduction unit of the flame unit was replaced by a UV assisted vapor generator, and atomization of the generated volatile species was achieved with a quartz tube atomizer. Parameters optimized included organic acid type and concentration, UV irradiation period, sonication period, carrier gas flow rate and atomizer temperature. Recovery studies were performed to determine the method's applicability to real samples, and interference studies were done to ascertain possible effects of the matrix on the analyte. The limits of detection and quantification were found to be 9.5 μg L− 1 and 31.7 μg L− 1, respectively. The low relative standard deviation indicated high precision, and experimented results of a certified reference material conformed to the certified value, validating the method's accuracy. Percent recoveries recorded were between 95% and 104% and the interferents tested showed different effects on the absorbance signals of nickel.