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Overuse of aluminum salts (a.k.a., alum) in coagulation and flocculation processes in water treatment raises concerns about increased levels of aluminum (Al) in drinking water. In this study, we present a probabilistic human health risk assessment (HRA) for non-cancerogenic risks, with Sobol sensitivity analysis, to vet the concern of increased health risk from Al in drinking water in Shiraz, Iran, for children, adolescents, and adults. The results show that the concentration of Al in the drinking water in Shiraz varies significantly between winter and summer seasons and varies considerably spatially across the city irrespective of the season. However, all concentrations are below the guideline concentration. The HRA results show that the highest health risk is for children in summer, and the lowest is for adolescents and adults during winter, with generally higher health risks for younger age groups. However, Monte Carlo results for all age groups suggest no adverse health effects due to Al exposure. The sensitivity analysis shows that the sensitive parameters vary across age groups. For example, the Al concentration and ingestion rate pose the most risk for adolescent and adult groups, and children group, respectively. More importantly, the interaction of Al concentration with ingestion rate and body weight is the controlling parameters for evaluating HRA rather than Al concentration alone. We conclude that while the HRA of Al in Shiraz drinking water did not indicate significant health risk, regular monitoring and optimal operation of the coagulation and flocculation processes are essential., (© 2023. The Author(s), under exclusive licence to Springer Nature B.V.)

Recovery of precious metals has been considered due to their limited availability and resources, and the reduction of environmental hazards. In this study, the environmentally friendly chloride leaching method was used to recover platinum (Pt) from a spent reforming catalyst. Hydrochloric acid and sodium chloride were applied as the complexing agent and ferric or cupric chloride (FeCl 3 , CuCl 2 ) was used as oxidants. Response surface methodology was implemented to investigate the influences of acid concentration (1-3 M), oxidant concentration (0.5-1.3 M), and temperature (70-90 °C) on the Pt extraction at a fixed duration of 3 h using two separate Box-Behnken experimental designs. Increasing temperature and acid concentration improved the Pt recovery from ∼52% to ∼89% in the presence of 1 M FeCl 3 , and from ∼29% to 94% in the presence of 0.75 M CuCl 2 . Generally, at low acid concentrations, ferric chloride was more efficient in Pt dissolution, while, at high acid concentrations, cupric chloride performed better. Finally, the platinum content of the pregnant leach solution was precipitated by adding a saturated ammonium chloride solution. According to the results of the X-ray diffraction analysis, the obtained precipitate was mainly composed of ammonium hexachloroplatinate, sodium chloride, and ammonium chloride. Also, the Pt assay of the powder was determined as 21%., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

A nanosensor is designed for rapid detection of the gluten content of wheat-containing samples. Gluten is a plant protein that causes allergy in individuals and leads to celiac disease. Since in a celiac diet trace amounts of gluten are able to prompt allergic reactions, a food-allergen label must be provided on foodstuffs and be seriously considered by food industries. Various analytical methods and commercial immunoassays are used for such analyses but prices per test, especially for low-income countries are high. Thus, a rapid, sensitive, simple, and inexpensive detecting tool seems essential. A solution can be designing a gluten optical nanosensor. The nanosensor is made of folic-acid-carbon dots and gluten molecularly templates embedded simultaneously in a silicate matrix. Adding gluten to the solution of this nanostructure and its adsorbing on the blank templated space on the nanostructure causes fluorescence enhancement. The concentration range of gluten detection was 0.36 to 2.20 µM., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Procedures for neurological disorders such as Parkinsons Disease (PD), Essential Tremor (ET), Obsessive Compulsive Disorder (OCD), Tourette's Syndrome (TS), and Major Depressive Disorder (MDD) tend to overlap. Common therapeutic procedures include deep brain stimulation (DBS), lesioning, and focused ultrasound (FUS). There has been significant change and innovation regarding targeting mechanisms and new advancements in this field allowing for better clinical outcomes in patients with severe cases of these conditions. In this review, we discuss advancements and recent discoveries regarding these three procedures and how they have led to changes in utilization in certain conditions. We further discuss the advantages and drawbacks of these treatments in certain conditions and the emerging advancements in brain-computer interface (BCI) and its utility as a therapeutic for neurological disorders., Competing Interests: Conflict of interest: The authors declare no conflict of interest., (© 2023 the Author(s), licensee AIMS Press.)

Construction and demolition waste (CDW) substantially contributes to environmental degradation because of its intrinsic characteristics of fast and high generation volume, low recycling rate, and low revenue margins. A systemic problem is that recycling facilities are not usually a part of a reverse supply chain (RSC) specific for CDW. This makes the recovery process costs prohibitive, especially where companies are unable to receive and process large volumes of waste continuously. This paper presents a systematic analysis of the extant literature and utilizes the results accrued to develop a conceptual RSC model for CDW. In so doing, the research seeks to provide clarity on this phenomenon, while simultaneously stimulating wider academic discourse and further research endeavours. A mixed philosophies epistemological design was adopted using both interpretavism and constructivism to undertake a qualitative systematic analysis of the literature. A process diagram was produced to represent the conceptual model (CM) and thematically group the nodes into three key swim lanes that delineate the boundaries between distribution, manufacturing, and sourcing and warehousing processes. Within each swim lane, stakeholders were incorporated as key actors. A further layer of nuanced complexity was added to illustrate the key actors involved in the process, government strategies, and activity flow paths. This novel CM offers both practical and theoretical contributions to existing knowledge and signposts a future research direction. Such work will demystify reverse logistics for managing CDW, and assist government policy-makers to develop informed policies that reduce the negative environmental impact of construction activities.

This study aimed to assess the awareness and performance of Qom citizens towards using disinfectants and compared its relationship with geographical distribution of COVID-19 outbreak in Qom, Iran. The study was conducted by a researcher-made questionnaire during April and May, 2020. COVID-19 incidence data for each district of city was obtained from health department of Qom province. Data were analyzed using Excel, SPSS and ArcView (GIS) softwares. It was found that the highest level of citizens' awareness (52%) was in the weak range while their performance (56%) was in the good range. According to Spearman's correlation analysis, there was a strong correlation (rho 0.95) between the total mean of awareness and performance ( p < 0.01). The highest incidence rate of COVID-19 was in district 7 which had the lowest mean score in both awareness and performance. In addition, the results of ANOVA (LSD-least significant difference) showed that there was a significant difference ( p < 0.05) between district 7-with lower mean scores in awareness and performance-and other districts. Overall, it is concluded that citizens' awareness level was lower than that of their performance. This conclusion not only calls for more training programs to be implemented in public places, schools, universities and governmental offices, but it also necessitates maintaining a proper and timely training about using disinfectants.

Occupational Health and Safety (OHS)-related injuries are vexing problems for construction projects in developing countries, mostly due to poor managerial-, governmental-, and technical safety-related issues. Though some studies have been conducted on OHS-associated issues in developing countries, research on this topic remains scarce. A review of the literature shows that presenting a predictive assessment framework through machine learning techniques can add much to the field. As for Malaysia, despite the ongoing growth of the construction sector, there has not been any study focused on OHS assessment of workers involved in construction activities. To fill these gaps, an Ensemble Predictive Safety Risk Assessment Model (EPSRAM) is developed in this paper as an effective tool to assess the OHS risks related to workers on construction sites. The developed EPSRAM is based on the integration of neural networks with fuzzy inference systems. To show the effectiveness of the EPSRAM developed, it is applied to several Malaysian construction case projects. This paper contributes to the field in several ways, through: (1) identifying major potential safety risks, (2) determining crucial factors that affect the safety assessment for construction workers, (3) predicting the magnitude of identified safety risks accurately, and (4) predicting the evaluation strategies applicable to the identified risks. It is demonstrated how EPSRAM can provide safety professionals and inspectors concerned with well-being of workers with valuable information, leading to improving the working environment of construction crew members.

Design of experiment and hybrid genetic algorithm optimized multilayer perceptron (GA-MLP) artificial neural network have been employed to model and predict dye decomposition capacity of the biologically synthesized nano CdS diatomite composite. Impact of independent variables such as, light (UV: on-off), solution pH (5-8), composite weight (CW: 0.5-1 mg), initial dye concentration (DC: 10-20 mg/l) and contact time (0-120 min), mainly in two levels, were examined to evaluate dye removal efficiency of the composite. According to the developed response surface based on the factorial design, all independent variables shown positive interactive effect on dye removal (UV > CW > pH > DC), as well as the pH-CW mutual interaction, while both UV-DC and CW-DC had antagonistic effect. The pH-CW interaction was more influential than pH and DC. Incorporation of the intermediate measurements of dye removal between the start and final contact times in GA-MLP approach, had found to improve the accuracy and predictability of the GA-MLP model. Based on the closeness of the R 2 (0.98), root mean square error (1.03), variance accounted for (98.23%), mean absolute error (0.61) and model predictive error (9.46%) to their desirable levels, proposed GA-MLP model outperformed the factorial design model. Finally, optimal parameter choice for maximum dye removal using factorial design and GA-MLP were found as: UV (on), pH (9), CW (1 g) and DC (10 mg/l) and UV (on), pH (8.85), CW (0.92 g), DC (12.3 mg/l) and T (117 0.6 min), respectively., (Copyright © 2019 Elsevier Inc. All rights reserved.)

The construction industry consistently ranks amongst the highest contributors to global gross domestic product, as well as, amongst the most corrupt. Corruption therefore inflicts significant risk on construction activities, and overall economic development. These facts are widely known, but the various sources and nature of corruption risks endemic to the Iranian construction industry, along with the degree to which such risks manifest, and the strength of their impact, remain undescribed. To address the gap, a mixed methods approach is used; with a questionnaire, 103 responses were received, and these were followed up with semi-structured interviews. Results were processed using social network analysis. Four major corruption risks were identified: (1) procedural violations in awarding contracts, (2) misuse of contractual arrangements, (3) neglect of project management principles, and, (4) irrational decision making. While corruption risks in Iran align with those found in other countries, with funds being misappropriated for financial gain, Iran also shows a strong inclination to champion projects that serve the government's political agenda. Root cause identification of corruption risks, namely, the noticeable impact of authoritarianism on project selection in Iran, over criterion of economic benefit or social good, is a significant outcome of this study.

Corruption in the construction industry is a serious problem in China. As such, fighting this corruption has become a priority target of the Chinese government, with the main effort being to discover and prosecute its perpetrators. This study profiles the demographic characteristics of major incidences of corruption in construction. It draws on the database of the 83 complete recorded cases of construction related corruption held by the Chinese National Bureau of Corruption Prevention. Categorical variables were drawn from the database, and 'association rule mining analysis' was used to identify associations between variables as a means of profiling perpetrators. Such profiling may be used as predictors of future incidences of corruption, and consequently to inform policy makers in their fight against corruption. The results signal corruption within the Chinese construction industry to be correlated with age, with incidences rising as managers' approach retirement age. Moreover, a majority of perpetrators operate within government agencies, are department deputies in direct contact with projects, and extort the greatest amounts per case from second tier cities. The relatively lengthy average 6.4-year period before cases come to public attention corroborates the view that current efforts at fighting corruption remain inadequate.

Hydrogen cyanide (HCN) adsorption on pristine and B-N doped biphenylene nanosheets was investigated by means of density functional theory calculations. According to biphenylene geometry, all distinct possible B-N substitutions were designed. Adsorption energy and electronic structure at the level of M062X/6-31 g (d,p) theory were computed for all possible geometries. Our results reveal that pristine biphenylene nanosheet is not a suitable candidate for HCN detection. Also, for B-N doping, the sensitivity of the nanosheet depends on the B-N doped configuration. One of these derivative structures shows higher sensitivity to HCN adsorption due to the greater change in electronic properties. Moreover, atoms in molecules and natural bond orbital analysis were performed to obtain more in-depth knowledge about the adsorption mechanism. The range of energy for interaction between HCN and the nanosheets belongs to physical adsorption.

Effects of in ovo injection of Q10 on hatchability, performance (feed intake (FI), body weight gain (BWG), feed/gain ratio (F/G)) traits, and immune status of Ross × Ross 308 broiler chicks, hatched from eggs laid by a 38-week-old breeder flock, were determined through 42 days after hatch. Eggs containing live embryos were injected in the amnion with 0.1 and 0.2 mL Q10 solution on day 18 of incubation. Two controls groups were included as sham and/or as an uninjected group. At 28 and 42 days of age, performance traits, serum enzyme activity, weights of immune organs, and serum antibody titer of viral diseases were determined. Results were shown that hatchability % increased by Q10 on average of 6.54% (P≤0.025) and body weight/egg weight after hatching increased up to 4.74% (P≤0.002), compared with uninjected and sham controls. Injection of Q10 at different levels led to significant increases (P≤0.001) in performance traits all over the rearing period (P<0.05). Weight of immune organs significantly improved compared to uninjected and sham controls (P<0.05). In addition, serum antibody titers of viral diseases as well as serum enzyme activity of AST, ALT, CAT, and SOD were significantly changed by Q10 treated groups than controls (P≤0.01). In conclusion, in ovo injection of Q10 at levels of 0.1 and 0.2 mL led to significant increases in hatchability%, internal egg characteristics, and performance parameters as well as serum enzyme activity, weight of immune organs, and serum antibody titer of ND, AI, and IBD diseases.

The electronic properties, adsorption energies and energy barrier of sodium ion diffusion in B-doped graphyne (BGY) are studied by density functional theory (DFT) method. If some carbon atoms in pristine graphyne (GY) are substituted by boron atoms (one substitution per unit cell in this work), BGY is obtained, and the band structure and density of state (DOS) plots indicate a transition from a semiconductive state for GY to a metallic state for BGY. The calculated adsorption energy shows an improvement in the trigonal-like pore (T site) and hexagonal ring (H site) adsorption of BGY compared to the corresponding analog sites in GY. The comparison of projected density of state (PDOS) plots before and after adsorption reveals charge transfer from sodium to nanosheets. Therefore, the interaction between adsorbed sodium atom and BGY/GY has ionic character and not covalent. This phenomenon is important for the reversible sodium adsorption in secondary batteries. Moreover, PDOS plots show that the electron transfer from sodium atom to host structure in BGY is more than in GY, which is in agreement with adsorption energies. According to diffusion energy barrier calculations, boron atoms in BGY structure provide low energy paths for sodium ions diffusion. We estimate a theoretical capacity of 751 mA h g-1 for the maximum sodium adsorption on BGY (without cluster formation). Therefore, BGY is a promising anode material for sodium ion batteries (SIBs).

Sorption is the most effective approach to the treatment of acid mine drainage (AMD) and wastewaters, but the removal of the adsorbents from water has always been a challenging problem which may be resolved by using magnetic separation. In this work, a magnetic bioadsorbent was prepared using low cost and high-performance sources and applied in Cr(VI) removal from a synthetic solution. Initially, magnetite nanoparticles were synthesized from iron boring scraps by chemical co-precipitation method. Results of dynamic light scattering (DLS) and vibrating sample magnetometry (VSM) analyses showed that the synthesized nanoparticles were around 40 nm in size and had a significant magnetization. Then, the magnetite nanoparticles were attached to the dead and alkaline activated biomass of Aspergillus niger. Central composite design (CCD) was applied to determine the optimal condition of Cr(VI) adsorption on the produced magnetic nanobiocomposite. The maximum chromium removal (~ 92%) was achieved at pH 5.8, Cr concentration 23.4 mg/l, adsorbent dose 3.72 g/l, agitation rate 300 rpm, and duration 11 min. Kinetic studies showed that regardless of temperature, the process was controlled by mass transfer and intraparticle diffusion with an equilibrium constant of 0.74 mg/g min 1/2 at 40 °C. Also, the adsorption isotherms followed the Temkin model, which indicated the physical adsorption of Cr(VI) on the produced sorbent. Therefore, the magnetic nanobiocomposite has a perfect ability to be used as the chromium adsorbent and can be collected by a low external magnetic field. Graphical abstract Synthesis of the magnetic nanobiosorbent and its application in the removal of Cr(VI) from wastewaters.

A straightforward, highly efficient, and low-cost biological route was introduced for the synthesis of magnetic nanoparticles. Three urease-positive bacteria namely, Bacillus subtilis, B. pasteurii, and B. licheniformis were used to biosynthesize ammonia and biosurfactants required for the nanoparticle production. Also, the features of the applied biological approach was compared with a chemical co-precipitation method. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), vibrating-sample magnetometer (VSM), and Fourier transform infrared spectroscopy (FTIR) were applied to characterize the synthesized nanoparticles. Results indicated that the biologically fabricated powders had a single domain structure, and their mean particle size was in the range of 37 to 97 nm. The production capacity of the biological processes was double the chemical method, and the biosynthesized superparamagnetic nanoparticles had higher saturation magnetization up to 132 emu/g. Finally, the removal of Cr(VI) from a synthetic solution was investigated using the four products. The maximum elimination of chromium (over 99%) was achieved by the particles synthesized by B. pasteurii, with the adsorption capacity of 190 mg/g., (Copyright © 2018 Elsevier B.V. All rights reserved.)

In the light of increased environmental concerns and the unsustainability of current construction practices, 'reverse logistics' (RL) has emerged as a remedial strategy, whereby decommissioned buildings are salvaged and returned back through the value chain for recovery, refurbishment and reuse. The drivers that impact the uptake of RL are known, but if sustainability outcomes are to be enhanced, the strength of those drivers must be quantified in order to ascertain where efforts should be focused. This study aims to quantify the effects of known drivers on RL, and in so doing identify action items with the greatest potential to positively improve RL outcomes. RL drivers are culled from extant research, and categorized as economic, environmental, or social forces. A conceptual model is developed and tested against questionnaire results drawn from 49 expert respondents active in the South Australian construction industry. The results are analyzed using structured equation modeling. Economic and environmental drivers, such as the continuing relative high cost of salvaged items, along with expediency of cost, time and quality objectives overshadowing regulatory demands for use of such salvaged items, are shown to predict 34% of the variations in implementing RL. Of particular interest is the finding contradicting previous studies, showing that social drivers, such as perceived benefits from 'going green' had no significant impact. Thus, the road-map to improving RL outcomes lies in reducing costs of salvaged materials, augmenting environmental policies that promoted their use, and to initiate a regulatory framework to generate compliance. This insight will be of interest to industry policymakers and environmental strategists alike., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Mining and hydrometallurgical industries produce large amounts of hazardous metal sulfate solutions as a by-product which can be recycled and exploited to produce valuable and advanced materials. Here, for the first time, extracellular polymeric substances of Bacillus licheniformis were applied as biosurfactants to synthesize quantum dots of cadmium sulfide from pure artificial and impure industrial cadmium sulfate solutions. The bacterial biopolymers stabilized the generated crystalline nuclei as colloidal dots and prevented their further growth or agglomeration. In order to discover the composition and size distribution of the produced particles, characterization was performed by X-ray diffraction (XRD), and transmission electron microscopy (TEM). Results showed that the particles biosynthesized from the pure solution were nano-sized cubic crystals of CdS with the dimensions of 2-10nm. The same product was also derived from the impure industrial solution. The outcomes of this study indicate the feasibility of cadmium or probably other metal recovery from industrial solutions and wastewaters in the form of valuable metal sulfide nanoparticles., (Copyright © 2016 Elsevier Inc. All rights reserved.)

In this research, an electrochemical sensor based on molecularly imprinted polymer (MIP) nanoparticles for selective and sensitive determination of diazinon (DZN) pesticides was developed. The nanoparticles of diazinon imprinted polymer were synthesized by suspension polymerization and then used for modification of carbon paste electrode (CPE) composition in order to prepare the sensor. Cyclic voltammetry (CV) and square wave voltammetry (SWV) methods were applied for electrochemical measurements. The obtained results showed that the carbon paste electrode modified by MIP nanoparticles (nano-MIP-CP) has much higher adsorption ability for diazinon than the CPE based non-imprinted polymer nanoparticles (nano-NIP-CP). Under optimized extraction and analysis conditions, the proposed sensor exhibited excellent sensitivity (95.08 μA L μmol(-1)) for diazinon with two linear ranges of 2.5 × 10(-9) to 1.0 × 10(-7) mol L(-1) (R (2) = 0.9971) and 1.0 × 10(-7) to 2.0 × 10(-6) mol L(-1) (R (2) = 0.9832) and also a detection limit of 7.9 × 10(-10) mol.L(-1). The sensor was successfully applied for determination of diaznon in well water and apple fruit samples with recovery values in the range of 92.53-100.86 %. Graphical abstract Procedure for preparation of electrochemical sensor based on MIP nanoparticles for determination of diazinon.

Reverse logistics in construction refers to the movement of products and materials from salvaged buildings to a new construction site. While there is a plethora of studies looking at various aspects of the reverse logistics chain, there is no systematic review of literature on this important subject as applied to the construction industry. Therefore, the objective of this study is to integrate the fragmented body of knowledge on reverse logistics in construction, with the aim of promoting the concept among industry stakeholders and the wider construction community. Through a qualitative meta-analysis, the study synthesises the findings of previous studies and presents some actions needed by industry stakeholders to promote this concept within the real-life context. First, the trend of research and terminology related with reverse logistics is introduced. Second, it unearths the main advantages and barriers of reverse logistics in construction while providing some suggestions to harness the advantages and mitigate these barriers. Finally, it provides a future research direction based on the review., (© The Author(s) 2015.)

Background: Insufficient information is available on the barriers that explain low rates of thrombolytic therapy for acute ischemic stroke (AIS) in developing countries compared with rates in developed societies. By the present study, we aimed to assess the implementation of thrombolytic therapy in the northeast of Iran to explore the gaps and hurdles against thrombolysis as the generally accepted treatment for AIS., Methods: In a 1-year cohort study among AIS patients admitted to the second largest tertiary neurologic referral center in Iran, those who met the prespecified selection criteria were treated with intravenous recombinant tissue plasminogen activator (rtPA)., Results: Among 1,144 patients admitted with AIS, only 14 (1.2%) were treated with rtPA. The mean onset-to-needle and door-to-needle times were 172 and 58 minutes, respectively; 980 (85.6%) patients were initially excluded from the study because of late arrival. Additionally, 60 patients in total were omitted because of either their high age (3.7%) or passing the gold standard time limit for rtPA therapy after preliminary evaluations (1.6%), and 90 more patients (7.9%) were considered not suitable for thrombolysis because of the severity of the symptoms or the higher risk of bleeding on rtPA., Conclusions: Access to thrombolytic therapy for AIS in Iran is less than in most developed countries but comparable with other developing countries. Awareness campaigns are needed to minimize barriers and improve access to thrombolysis and specialized stroke care in Iran., (Copyright © 2015 National Stroke Association. Published by Elsevier Inc. All rights reserved.)

Continuous sample drop flow-based microextraction (CSDF-ME) is an improved version of continuous-flow microextraction (CFME) and a novel technique developed for extraction and preconcentration of benzene, toluene, ethyl benzene, m-xylene and o-xylene (BTEXs) from aqueous samples prior to gas chromatography-flame ionization detection (GC-FID). In this technique, a small amount (a few microliters) of organic solvent is transferred to the bottom of a conical bottom test tube and a few mL of aqueous solution is moved through the organic solvent at relatively slow flow rate. The aqueous solution transforms into fine droplets while passing through the organic solvent. After extraction, the enriched analyte in the extraction solvent is determined by GC-FID. The type of extraction solvent, its volume, needle diameter, and aqueous sample flow rate were investigated. The enrichment factor was 221-269 under optimum conditions and the recovery was 89-102%. The linear ranges and limits of detection for BTEXs were 2-500 and 1.4-3.1 µg L(-1), respectively. The relative standard deviations for 10 µg L(-1) of BTEXs in water were 1.8-6.2% (n=5). The advantages of CSDF-ME are its low cost, relatively short sample preparation time, low solvent consumption, high recovery, and high enrichment factor., (Copyright © 2014 Elsevier B.V. All rights reserved.)

In this study, ultrasonic assisted miniaturized matrix solid-phase dispersion (US-MMSPD) combined with homogeneous liquid-liquid extraction (HLLE) has been developed as a new method for the extraction of organochlorinated pesticides (OCPs) in fish prior to gas chromatography with electron capture detector (GC-ECD). In the proposed method, OCPs (heptachlor, aldrin, DDE, DDD, lindane and endrin) were first extracted from fish sample into acetonitrile by US-MMSPD procedure, and the extract was then used as consolute solvent in HLLE process. Optimal condition for US-MMSPD step was as follows: volume of acetonitrile, 1.5 mL; temperature of ultrasound, 40°C; time of ultrasound, 10 min. For HLLE step, optimal results were obtained at the following conditions: volume of chloroform, 35 μL; volume of aqueous phase, 1.5 mL; volume of double distilled water, 0.5 mL; time of centrifuge, 10 min. Under the optimum conditions, the enrichment factors for the studied compounds were obtained in the range of 185-240, and the overall recoveries were ranged from 39.1% to 81.5%. The limits of detection were 0.4-1.2 ng g(-1) and the relative standard deviations for 20 ng g(-1) of the OCPs, varied from 3.2% to 8% (n=4). Finally, the proposed method has been successfully applied to the analysis of the OCPs in real fish sample, and satisfactory results were obtained., (Copyright © 2011 Elsevier B.V. All rights reserved.)

A very simple and economic method for organophosphorus pesticides (OPPs) residues analysis in tomato by means of gas chromatography-flame photometric detection (GC-FPD) has been developed. The method involves a rapid and small-scale extraction. The sample was homogenised and extraction of the OPPs with acetone was carried out assisted by sonication. No clean-up or evaporation were required after extraction. Pre-concentration of the OPPs from the acetone extract was done by using dispersive liquid-liquid microextraction (DLLME) technique. Chlorobenzene was added in micro-level volume as extraction solvent and triphenylphosphate as internal standard in DLLME procedure. The method showed good linearity over the range assayed (0.5-1000μgkg(-1)) and the detection limits for the pesticides studied varied from 0.1 to 0.5μgkg(-1). Repeatability studies resulted a relative standard deviation lower than 10% in all cases. The proposed method was used to determine pesticides levels in tomatoes grown in open field., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Background: Migraine Induced Stroke (MIS) is an important cause of brain infarction in the young people., Methods: Consecutive patients with MIS admitted in Ghaem hospital, Mashhad during 2006-2010 enrolled a prospective clinical study. All of the patients suspected to MIS had brain MRI with a 0.5 Tesla generation, Philips NT Intra, Netherland. All of the MIS patients underwent a standard battery of diagnostic investigations for detecting etiology of stroke. Disability of MIS patients was detected based on the modified Rankin scale at 90 days post stroke., Results: 32 MIS patients (18 females, 14 males) with mean age 37.2 ± 3.8 years ranged 15-58 years were evaluated. Hypodense area of infarction corresponding to clinical manifestations was detected in MRI in 32% of our MIS patients. The mean disability score in our MIS patients was 1.09 ± 0.32, which is significantly lower than other stroke patients (z = 2.55, P = 0.007), Conclusion: MIS is an important cause of stroke in Persian young adults which have good prognosis.

Electrochemical oxidation of glucose on a glassy carbon disc electrode modified with multi-walled carbon nanotubes and nickel(II) oxide (GC/MWCNT/NiO) was examined by cyclic voltammetry and chronoamperometry in alkaline aqueous solutions. The results were compared with those obtained on a nickel(II) oxide modified glassy carbon electrode (GC/NiO). Both electrodes conditioned by potential cycling in a limited potential range (0.1-0.6 V vs. Ag/AgCl) in 0.10 M NaOH solution. It was found that the multi-walled carbon nanotubes improve remarkably the reactivity of nickel(II) oxide for glucose oxidation. The GC/MWCNT/NiO electrode exhibited good linear behavior in the concentration range from 2.0x10(-4) mol/L to 1.2x10(-2) mol/L for the quantitative analysis of glucose with a limit of detection of 1.6x10(-4) mol/L (3sigma). The prepared electrode exhibits satisfactory stability and long life if stored at ambient conditions. Finally, it has been demonstrated that the proposed modified electrode can be successfully used for the assay of glucose in serum samples., (2009 Elsevier B.V. All rights reserved.)

In this article, a new method for the determination of organophosphorus pesticides (OPPs) in tea was developed by using dispersive liquid-liquid microextraction (DLLME) and gas chromatography-flame photometric detection (GC-FPD). A mixture of acetonitrile and n-hexane was used as an extraction solvent for the extraction of OPPs from tea samples. When the extraction process was finished, the mixture of solvents was rapidly dispersed in water; target analyte was extracted to a small volume of n-hexane, using DLLME. Recovery tests were performed for concentration 5.0 microg/kg. The recovery for each target analyte was in the range between 83.3 and 117.4%. The repeatability of the proposed method, expressed as relative standard deviation, varied between 3 and 7.8% (n=3). The detection limit of the method for tea was found ranging from 0.030 to 1 microg/kg for all the target pesticides. Compared with the conventional sample preparation method, the proposed method has the advantage of being quick and easy to operate, and has high-enrichment factors and low consumption of organic solvent.

Background: Hepatitis B virus infection is a very common cause of chronic liver disease worldwide. It is estimated that 3% of Iranians are chronically infected with hepatitis B virus. Current population-based studies on both rural and urban prevalence of hepatitis B virus infection in Iran are sparse with results that do not always agree. We performed this study to find the prevalence of hepatitis B surface antigen, anti-hepatitis B core antibody, and associated factors in the general population of three provinces of Iran., Methods: We randomly selected 6,583 subjects from three provinces in Iran, namely Tehran, Golestan, and Hormozgan. The subjects were aged between 18 and 65 years. Serum samples were tested for hepatitis B surface antigen and anti-hepatitis B core antibody. Various risk factors were recorded and multivariate analysis was performed., Results: The prevalence of hepatitis B surface antigen and anti-hepatitis B core antibody in Iran was 2.6% and 16.4%, respectively. Predictors of hepatitis B surface antigen or anti-hepatitis B core antibody in multivariate analysis included older age, not having high-school diploma, living in a rural area, and liver disease in a family member. We did not find any significant differences between males and females., Conclusion: In spite of nationwide vaccination of newborns against hepatitis B virus since 1992, hepatitis B virus infection remains a very common cause of chronic liver disease in Iran which should be dealt with for at least the next 30-50 years.

Background: The control of leishmaniasis, a tropical neglected disease, has been concern of Iranian health authorities due to the increasing number of cases during the last two decades. The objective of this study was to determine deltamethrine residue on the impregnated bed nets using HPTLC technique in a leishmaniasis control program in Iran., Methods: During this experimental study, a total of 130 small pieces of polyester netting were sewn to top, upper, and lower sides of some bed nets and then were impregnated with deltamethrin. The treated bed nets were distributed in Isfahan and Mashhad areas in April 2003. The samples were cut randomly after impregnation intervals. Deltamethrin was extracted using acetone from samples and the extract was applied for spotting onto plates. The plates were developed with n-hexane: ethyl acetate, 90+10(v/v), as a mobile phase in a Camage chamber. The qualifying of residue was observed in UV cabinet with λ=254 nm wavelength. Data were analyzed using SPSS version 11.5. and Stata Version 8. A three way ANOVA was used to compare the means of deltamethrin residue in each area, group and measuring time. The Kruskal-Wallis test was used to compare the means of residue for each of these factors with the control separately., Results: The retardation factor of deltamethrin was calculated 0.50±0.02. The residues of deltamethrin persisted well on impregnated nets at least for 15 weeks after impregnation. No significant difference could be detected in the loss of residue of insecticide in comparison to measuring times and positions of sampling pieces on the bed nets in these areas., Conclusion: Based on the results of the present study the use of HPTLC technique is recommended instead of other chromatographic methods for analysis of insecticide residue on the impregnated bed nets.

A very simple and powerful microextraction procedure, the dispersive liquid-liquid microextraction (DLLME), was used for the determination of the content of 10 polychlorinated biphenyls (PCBs) in water samples, using gas chromatography coupled with electron-capture detection (GC-ECD). The appropriate amount of acetone (disperser solvent) and chlorobenzene (extraction solvent) at the microlevel volume was used for this procedure. The conditions for the microextraction performance were investigated and optimized. The optimized method exhibited a good linearity (R(2)>0.996) over the studied range (0.005-2 microg L(-1)), illustrating a satisfactory precision level with R.S.D. values between 4.1% and 11.0%. The values of the detection limit (S/N=3) were found to be lower than 0.002 microg L(-1). Furthermore, a large enrichment factor for the analytes (up to a 540-fold) was achieved in a very short time for only a 5.00-mL water sample. The effectiveness of the method towards real samples was tested by analyzing well, river and seawater samples. The relative recoveries of the well, river and seawater samples, which had been spiked with different levels of PCBs were equal to 92.0-114.0%, 97.0-102.0% and 96.0-103.0%, respectively. The attained results demonstrated that DLLME combined with GC-ECD was a fast and inexpensive technique for the PCBs determination in water samples.

Dispersive liquid-liquid microextraction and gas chromatography-flame photometric detection (DLLME-GC-FPD) were performed for the speciation of butyl and phenyltin compounds in water samples after derivatization with sodium tetraethylborate (NaBEt4). Some important parameters, such as pH, amount of NaBEt4, derivatization time, kind and volume of extraction and disperser solvents, extraction time and salt effect were investigated and optimized. High enrichment factors (825-1036) and low detection limits (0.2-1 ng L(-1)) were obtained under the optimum conditions. The calibration graphs were linear in the range of 0.5-1000 ng L(-1) (as Sn) for the target analytes. The relative standard deviations (RSDs) for the extraction of 20 ng L(-1) (as Sn) of butyl and phenyltin compounds varied from 2.3 to 5.9% (n=7) and from 4.1 to 8.8% (n=7) with and without using internal standard, respectively. Seawater and river water samples were successfully analyzed using the proposed method and the relative recoveries of the studied compounds in the water samples, at spiking levels of 10.0 and 100 ng L(-1) (as Sn) were obtained to be 82.5-104.7%.

The need for highly reliable methods for the determination of trace and ultratrace elements has been recognized in analytical chemistry and environmental science. A simple and powerful microextraction technique was used for the detection of the lead ultratrace amounts in water samples using the dispersive liquid-liquid microextraction (DLLME), followed by the electrothermal atomic absorption spectrometry (ET AAS). In this microextraction technique, a mixture of 0.50 mL acetone (disperser solvent), containing 35 microL carbon tetrachloride (extraction solvent) and 5 microL diethyldithiophosphoric acid (chelating agent), was rapidly injected by syringe into the 5.00 mL water sample, spiked with lead. In this process, the lead ions reacted with the chelating agent and were extracted into the fine droplets of CCl(4). After centrifugation (2 min at 5000 rpm), the fine CCl4 droplets were sedimented at the bottom of the conical test tube (25+/-1 microL). Then, 20 microL from the sedimented phase, containing the enriched analyte, was determined by ET AAS. The next step was the optimization of various experimental conditions, affecting DLLME, such as the type and the volume of the extraction solvent, the type and the volume of the disperser solvent, the extraction time, the salt effect, pH and the chelating agent amount. Moreover, the effect of the interfering ions on the analytes recovery was also investigated. Under the optimum conditions, the enrichment factor of 150 was obtained from only a 5.00 mL water sample. The calibration graph was linear in the range of 0.05-1 microg L(-1) with the detection limit of 0.02 microg L(-1). The relative standard deviation (R.S.D.) for seven replicate measurements of 0.50 microg L(-1) of lead was 2.5%. The relative lead recoveries in mineral, tap, well and sea water samples at the spiking level of 0.20 and 0.40 microg L(-1) varied from 93.5 to 105.0. The characteristics of the proposed method were compared with the cloud point extraction (CPE), the liquid-liquid extraction, the solid phase extraction (SPE), the on-line solid phase extraction (SPE) and the co-precipitation, based on bibliographic data. The main DLLME advantages combined with ET AAS were simplicity of operation, rapidity, low cost, high-enrichment factor, good repeatability, low consumption of extraction solvent, requiring a low sample volume (5.00 mL).

The dispersive liquid-liquid microextraction (DLLME) was combined with the flame atomic absorption spectrometry (FAAS) for determination of lead in the water samples. Diethyldithiophosphoric acid (DDTP), carbon tetrachloride and methanol were used as chelating agent, extraction solvent and disperser solvent, respectively. A new FAAS sample introduction system was employed for the microvolume nebulization of the non-flammable chlorinated organic extracts. Injection of 20 microL volumes of the organic extract into an air-acetylene flame provided very sensitive spike-like and reproducible signals. Some effective parameters on the microextraction and the complex formation were selected and optimized. These parameters include extraction and disperser solvent type as well as their volume, extraction time, salt effect, pH and amount of the chelating agent. Under the optimized conditions, the enrichment factor of 450 was obtained from a sample volume of 25.0 mL. The enhancement factor, calculated as the ratio of the slopes of the calibration graphs with and without preconcentration, which was about 1000. The calibration graph was linear in the range of 1-70 microgL(-1) with a detection limit of 0.5 microgL(-1). The relative standard deviation (R.S.D.) for seven replicate measurements of 5.0 and 50 microgL(-1) of lead were 3.8 and 2.0%, respectively. The relative recoveries of lead in tap, well, river and seawater samples at the spiking level of 20 microgL(-1) ranged from 93.8 to 106.2%. The characteristics of the proposed method were compared with those of the liquid-liquid extraction (LLE), cloud point extraction (CPE), on-line and off-line solid-phase extraction (SPE) as well as co-precipitation, based on bibliographic data. Operation simplicity, rapidity, low cost, high enrichment factor, good repeatability, and low consumption of the extraction solvent at a microliter level are the main advantages of the proposed method.

The solid-phase extraction (SPE) joined with the dispersive liquid-liquid microextraction (DLLME) has been developed as an ultra preconcentration technique for the determination of chlorophenols in water samples. Chlorophenols (CPs) were employed as model compounds to assess the extraction procedure and were determined by gas chromatography-electron-capture detection (GC-ECD). In solid-phase extraction-dispersive liquid-liquid microextraction (SPE-DLLME), CPs were adsorbed from a large volume of aqueous samples (100 mL) into 100 mg functionalized styrene-divinylbenzene polymer (PPL) sorbent. After the elution of the desired compounds from the sorbent by using acetone, DLLME technique was performed on the obtained solution. Some important extraction parameters, such as sample solution flow rate, breakthrough volume, sample pH, type and volume of the elution solvent as well as the salt addition, were studied and optimized. The new method (SPE-DLLME) provided an ultra enrichment factor (4390-17,870) for 19 CPs. The calibration graphs were linear in the range of 0.001-20 microg L(-1) and the limits of detection (LODs) ranged from 0.0005 to 0.1 microg L(-1). The relative standard deviations (RSDs, for 10.0 microg L(-1) of MCPs, 5.00 microg L(-1) of DCPs, 0.200 microg L(-1) of TCPs, 0.100 microg L(-1) of TeCPs and PCP) with and without the internal standard varied from 1.1 to 6.4% (n=7) and 2.5-9.7% (n=7), respectively. The relative recoveries of the well, tap and river water samples, spiked with different levels of CPs, were 71-110%, 73-115% and 88-121%, respectively.

Simultaneous dispersive liquid-liquid microextraction (DLLME) and derivatization combined with gas chromatography-electron-capture detection (GC-ECD) was used to determine chlorophenols (CPs) in water sample. In this derivatization/extraction method, 500 microL acetone (disperser solvent) containing 10.0 microL chlorobenzene (extraction solvent) and 50 microL acetic anhydride (derivatization reagent) was rapidly injected by syringe in 5.00 mL aqueous sample containing CPs (analytes) and K(2)CO(3) (0.5%, w/v). Within a few seconds the analytes derivatized and extracted at the same time. After centrifugation, 0.50 microL of sedimented phase containing enriched analytes was determined by GC-ECD. Some effective parameters on derivatization and extraction, such as extraction and disperser solvent type and their volume, amount of derivatization reagent, derivatization and extraction time, salt addition and amount of K(2)CO(3) were studied and optimized. Under the optimum conditions, enrichment factors and recoveries are in the range of 287-906 and 28.7-90.6%, respectively. The calibration graphs are linear in the range of 0.02-400 microg L(-1) and limit of detections (LODs) are in the range of 0.010-2.0 microg L(-1). The relative standard deviations (RSDs, for 200 microg L(-1) of MCPs, 100 microg L(-1) of DCPs, 4.00 microg L(-1) of TCPs, 2.00 microg L(-1) of TeCPs and PCP in water) with and without using internal standard are in the range of 0.6-4.7% (n=7) and 1.7-7.1% (n=7), respectively. The relative recoveries of well, tap and river water samples which have been spiked with different levels of CPs are 91.6-104.7, 80.8-117.9 and 83.3-101.3%, respectively. The obtained results show that simultaneous DLLME and derivatization combined with GC-ECD is a fast simple method for the determination of CPs in water samples.

In this study, a simple, rapid and efficient method, dispersive liquid-liquid microextraction (DLLME) combined gas chromatography-electron capture detection (GC-ECD), for the determination of chlorobenzenes (CBs) in water samples, has been described. This method involves the use of an appropriate mixture of extraction solvent (9.5 microl chlorobenzene) and disperser solvent (0.50 ml acetone) for the formation of cloudy solution in 5.00 ml aqueous sample containing analytes. After extraction, phase separation was performed by centrifugation and the enriched analytes in sedimented phase were determined by gas chromatography-electron capture detection (GC-ECD). Our simple conditions were conducted at room temperature with no stiring and no salt addition in order to minimize sample preparation steps. Parameters such as the kind and volume of extraction solvent, the kind and volume of disperser solvent, extraction time and salt effect, were studied and optimized. The method exhibited enrichment factors and recoveries ranging from 711 to 813 and 71.1 to 81.3%, respectively, within very short extraction time. The linearity of the method ranged from 0.05 to 100 microgl(-1) for dichlorobenzene isomers (DCB), 0.002-20 microgl(-1) for trichlorobenzene (TCB) and tetrachlorobenzene (TeCB) isomers and from 0.001 to 4 microgl(-1) for pentachlorobenzene (PeCB) and hexachlorobenzene (HCB). The limit of detection was in the low microgl(-1) level, ranging between 0.0005 and 0.05 microgl(-1). The relative standard deviations (R.S.D.s) for the concentration of DCB isomers, 5.00 microgl(-1), TCB and TeCB isomers, 0.500 microgl(-1), PeCB and HCB 0.100 microgl(-1) in water by using the internal standard were in the range of 0.52-2.8% (n=5) and without the internal standard were in the range of 4.6-6.0% (n=5). The relative recoveries of spiked CBs at different levels of chlorobenzene isomers in tap, well and river water samples were 109-121%, 105-113% and 87-120%, respectively. It is concluded that this method can be successfully applied for the determination of CBs in tap, river and well water samples.

Dispersive liquid-liquid microextraction (DLLME) technique was successfully used as a sample preparation method for graphite furnace atomic absorption spectrometry (GF AAS). In this extraction method, 500 microL methanol (disperser solvent) containing 34 microL carbon tetrachloride (extraction solvent) and 0.00010 g ammonium pyrrolidine dithiocarbamate (chelating agent) was rapidly injected by syringe into the water sample containing cadmium ions (interest analyte). Thereby, a cloudy solution formed. The cloudy state resulted from the formation of fine droplets of carbon tetrachloride, which have been dispersed, in bulk aqueous sample. At this stage, cadmium reacts with ammonium pyrrolidine dithiocarbamate, and therefore, hydrophobic complex forms which is extracted into the fine droplets of carbon tetrachloride. After centrifugation (2 min at 5000 rpm), these droplets were sedimented at the bottom of the conical test tube (25+/-1 microL). Then a 20 microL of sedimented phase containing enriched analyte was determined by GF AAS. Some effective parameters on extraction and complex formation, such as extraction and disperser solvent type and their volume, extraction time, salt effect, pH and concentration of the chelating agent have been optimized. Under the optimum conditions, the enrichment factor 125 was obtained from only 5.00 mL of water sample. The calibration graph was linear in the rage of 2-20 ng L(-1) with detection limit of 0.6 ng L(-1). The relative standard deviation (R.S.D.s) for ten replicate measurements of 20 ng L(-1) of cadmium was 3.5%. The relative recoveries of cadmium in tap, sea and rivers water samples at spiking level of 5 and 10 ng L(-1) are 108, 95, 87 and 98%, respectively. The characteristics of the proposed method have been compared with cloud point extraction (CPE), on-line liquid-liquid extraction, single drop microextraction (SDME), on-line solid phase extraction (SPE) and co-precipitation based on bibliographic data. Therefore, DLLME combined with GF AAS is a very simple, rapid and sensitive method, which requires low volume of sample (5.00 mL).

Introduction: An important consideration in endodontic treatment is the elimination of microorganisms, including fungi, from the complex three- dimensional root canal system. Candida Albicans (CA) has a major role in endodontic treatment failure as the most important fungus isolated from the root canal system. The present study was carried out to evaluate the presence of CA in the teeth requiring endodontic retreatment, with or without periapical lesions., Materials and Methods: This study was carried out on 60 root canals from human molars requiring endodontic retreatment. The root canals were randomly divided into two equal groups of 30 canals with versus without periapical lesions. Samples were collected from the root canals and cultured on MacConkey and blood agar culture media. The samples suspected of having CA were streaked on Sabouraud's Dextrose Agar (SDA) and evaluated under a light microscope. Data was analyzed and compared using Chi- square and Kappa tests., Results: CA was found in 11 patients (36.7%) with periapical lesions. In the patients without periapical lesions only 4 samples demonstrated CA in the root canal systems (13.3%). The difference between the two groups as to the presence of CA was statistically significant (p<0.037). In addition, evaluation of salivary samples revealed 15 cases (50%) of CA presence in the patients with periapical lesions and 16 cases (53.3%) of CA in the patients without periapical lesions, demonstrating no statistically significant difference between the two groups., Conclusion: Considering the fact that the presence of CA in the root canal systems of teeth with periapical lesions was more noticeable and statistically significant compared to the teeth without periapical lesions, the elimination of this microorganism from the root canal system, using appropriate intracanal solutions and medications is of utmost importance.

A new functionalized mesoporous silica (MCM-41) using salicylaldehyde was utilized for the separation, preconcentration and determination of uranium in natural water by inductively coupled plasma atomic emission spectrometry (ICP-AES). Experimental conditions for effective adsorption of trace levels of U(VI) were optimized. The preconcentration factor was 100 (1.0 mL of elution for a 100 mL sample volume). The analytical curve was linear in the range 2-1000 microg L(-1) and the detection limit was 0.5 ng mL(-1). The relative standard deviation (R.S.D.) under optimum conditions was 2.5% (n=10). Common coexisting ions did not interfere with the separation and determination of uranium at pH 5. The sorbent exhibited excellent stability and its sorption capacity under optimum conditions has been found to be 10mg of uranium per gram of sorbent. The method was applied for the recovery and determination of uranium in different water samples.

A new method was used for the extraction of organophosphorus pesticides (OPPs) from water samples: dispersive liquid-liquid microextraction (DLLME) coupled with gas chromatography-flame photometric detection (GC-FPD). In this extraction method, a mixture of 12.0 microL chlorobenzene (extraction solvent) and 1.00 mL acetone (disperser solvent) is rapidly injected into the 5.00 mL water sample by syringe. Thereby, a cloudy solution is formed. In fact, the cloudy state is because of the formation of fine droplets of chlorobenzene, which has been dispersed among the sample solution. In this step, the OPPs in water sample are extracted into the fine droplets of chlorobenzene. After centrifuging (2 min at 5000 rpm), the fine droplets of chlorobenzene are sedimented in the bottom of the conical test tube (5.0+/-0.3 microL). Sedimented phase (0.50 microl) is injected into the GC for separation and determination of OPPs. Some important parameters, such as kind of extraction and disperser solvent and volume of them, extraction time, temperature and salt effect were investigated. Under the optimum conditions, the enrichment factors and extraction recoveries were high and ranged between 789-1070 and 78.9-107%, respectively. The linear range was wide (10-100,000 pg/mL, four orders of magnitude) and limit of detections were very low and were between 3 to 20 pg/mL for most of the analytes. The relative standard deviations (RSDs) for 2.00 microg/L of OPPs in water with internal standard were in the range of 1.2-5.6% (n=5) and without internal standard were in the range of 4.6-6.5%. The relative recoveries of OPPs from river, well and farm water at spiking levels of 50, 500 and 5000 pg/mL were 84-125, 88-123 and 93-118%, respectively. The performance of proposed method was compared with solid-phase microextraction (SPME) and single drop microextraction. DLLME is a very simple and rapid (less than 3 min) method, which requires low volume of sample (5 mL). It also has high enrichment factor and recoveries for extraction of OPPs from water.

A new microextraction technique termed dispersive liquid-liquid microextraction (DLLME) was developed. DLLME is a very simple and rapid method for extraction and preconcentration of organic compounds from water samples. In this method, the appropriate mixture of extraction solvent (8.0 microL C2Cl4) and disperser solvent (1.00 mL acetone) are injected into the aqueous sample (5.00 mL) by syringe, rapidly. Therefore, cloudy solution is formed. In fact, it is consisted of fine particles of extraction solvent which is dispersed entirely into aqueous phase. After centrifuging, the fine particles of extraction solvent are sedimented in the bottom of the conical test tube (5.0 +/- 0.2 microL). The performance of DLLME is illustrated with the determination of polycyclic aromatic hydrocarbons (PAHs) in water samples by using gas chromatography-flame ionization detection (GC-FID). Some important parameters, such as kind of extraction and disperser solvent and volume of them, and extraction time were investigated. Under the optimum conditions the enrichment factor ranged from 603 to 1113 and the recovery ranged from 60.3 to 111.3%. The linear range was 0.02-200 microg/L (four orders of magnitude) and limit of detection was 0.007-0.030 microg/L for most of analytes. The relative standard deviations (RSDs) for 2 microg/L of PAHs in water by using internal standard were in the range 1.4-10.2% (n = 5). The recoveries of PAHs from surface water at spiking level of 5.0 microg/L were 82.0-111.0%. The ability of DLLME technique in the extraction of other organic compounds such as organochlorine pesticides, organophosphorus pesticides and substituted benzene compounds (benzene, toluene, ethyl benzene, and xylenes) from water samples were studied. The advantages of DLLME method are simplicity of operation, rapidity, low cost, high recovery, and enrichment factor.