Dielectric barrier discharge plasma pre-treatment to facilitate the acetylation process of corn starch under heating/cooling cycles.

The objective of the current work was to evaluate the impacts of dielectric barrier discharge plasma and repeated dry-heat treatments on the acetylation process of corn starch. The combined modification resulted in a higher substitution degree of acetate groups on starch chains compared to the acetylation treatment alone. This outcome was linked to the increase in surface area and structural organization level of granules achieved through the application of plasma and heating/cooling cycles, respectively. The successful esterification of starch structure was verified through FTIR (1710 cm-1) and 1H NMR (2 ppm). With the increase in plasma treatment duration up to 20 min, gelatinization enthalpy increased (10.81 J/g) due to the cross-linking reaction. Starch acetate produced through the combined treatment could find the application in the development of low-calorie food formulations due to its high resistant starch (70.5 g/100 g) and low viscosity (43 mPa s).

Solid state cationization reaction of microporous starch with betaine hydrochloride under repeated heating/cooling cycles: Design of a green approach for corn starch modification.

In this research, the cationization process of microporous starch with betaine hydrochloride (BHC) in the presence of H3PO4 (as a catalyst) under heating/cooling cycles was reported for the first time. Granular microporous starch was initially prepared from normal corn starch (NS) through amyloglucosidase treatment. Then, solid state cationization reaction of microporous starch (MS) with betaine hydrochloride (BHC) was performed under repeated dry-heat modification. The cationic microporous starch showed higher substitution degree (0.031) and reaction efficiency (89.1 %) in comparison with cationic starch based on NS (0.021, 60.3 %), which this can be attributed to the increased probability of effective collision between BHC molecules and starch granules after enzymatic treatment. The analysis of cationic starches by FTIR and 13C NMR confirmed the presence of cationic functional groups on starch chains. Further examinations on the modified starches by single and dual treatments were accomplished with respect to morphology, particle size distribution, X-ray powder diffraction (XRD), colour parameters, zeta potential, amylose content, viscosity, solubility, and swelling power. The greenness of the suggested dual treatment (score: 82) in this work was evaluated and compared to a conventional method reported in literature (score: 67) on the preparation of cationic starches.

Melamine in Iranian foodstuffs: A systematic review, meta-analysis, and health risk assessment of infant formula.

The presence of melamine in food is one of the most significant threats to consumer health and food safety now confronting the communities. The goal of this systematic review and meta-analysis was to determine the melamine content of different food products available on the Iranian market. The pooled melamine concentration (95% confidence interval) on 484 samples of animal-based foodstuffs was as follows: 0.22 (0.08, 0.36 mg kg-1) for milk, 0.39 (0.25, 0.53 mg kg-1) for coffee mate, 1.45 (1.36, 1.54 mg kg-1) for dairy cream, 0.90 (0.50, 1.29 mg kg-1) for yoghurt, 1.25 (1.20, 1.29 mg kg-1) for cheese, 0.81 (-0.16, 1.78 mg kg-1) for hen eggs, 1.28 (1.25, 1.31 mg kg-1) for poultry meat, 0.58 (0.35, 0.80 mg kg-1) for chocolates, and 0.98 (0.18, 1.78 mg kg-1) for infant formula. Based on the results of health risk assessment study on toddlers under 2 years old who ingested infant formula (as a melamine-sensitive group), all groups of toddlers are at an acceptable level of non-carcinogenic risk (THQ ≤ 1). Toddlers were classified according to their ILCR (carcinogenic risk) levels due to infant formula consumption as follows: under 6 months (0.0000056), 6-12 months (0.0000077), 12-18 months (0.0000102), and 18-24 months (0.0000117). The melamine carcinogenicity in infant formula for children had an ILCR value of 0.000001-0.0001 in the investigation, which was considerable risk. According to the findings, Iranian food products (notably infant formula) should be analyzed for melamine contamination on a regular basis.

Ultra-trace determination of cadmium in water and food samples by a thin-film microextraction using a supported liquid membrane combined with smartphone-based colorimetric detection.

A mixture of n-octanol and dithizone was introduced as an effective and novel extraction agent in a thin-film microextraction technique for the pre-concentration of cadmium ions. The extraction agent was immobilized on small pieces of porous polypropylene flat membrane as a supported liquid membrane. The analyte extraction was performed by immersing the modified film in the sample solution, and via a complex formation between the immobilized dithizone on the film and cadmium ions. After the thin-film microextraction process, the colored cadmium-dithizone complex was directly measured by a smartphone colorimetric analysis. Under optimized conditions, the linear dynamic range, the limit of detection, and the limit of quantification were 0.5-300.0, 0.1, and 0.4 µg L-1, respectively. The developed technique was successfully employed to quantify cadmium ions in water and food samples. The high relative recovery values (95.0-103.0%) along with relative standard deviations of less than 2.5% were obtained for the spiked samples.

Seismic structural control using magneto-rheological dampers: A decentralized interval type-2 fractional-order fuzzy PID controller optimized based on energy concepts.

In this paper, a combination of the interval type-2 fuzzy logic controller (IT2FLC) with the fractional-order proportional-integral-derivative (FOPID) controller, namely optimal interval type-2 fractional-order fuzzy proportional-integral-derivative controller (OIT2FOFPIDC), is developed for enhancing the seismic performance and robustness in seismic structural control applications. Based on the energy concepts, a decentralized framework of the OIT2FOFPIDC is proposed for easy and simple implementation in structures during earthquakes. For this purpose, a coot optimization algorithm (COA), as a powerful optimization algorithm, is also applied to adjust the membership functions (MFs), scaling factors, and the main controller parameters. Three controllers, namely optimal type-1 fuzzy proportional-integral-derivative controller (OT1FPIDC), optimal interval type-2 fuzzy proportional-integral-derivative controller (OIT2FPIDC), and optimal proportional-integral-derivative controller (OPIDC), are also proposed for comparison purposes. The seismic performances of the suggested controllers are examined with the evaluation of nine seismic performance indices and different ground accelerations in a 6-story smart structure equipped with two dampers. The robustness of the four controllers in the presence of the stiffness uncertainties is also compared in this study. On average, a reduction of 25.0%, 18.8%, and 18.5% in peak displacement, inter-story drift, and acceleration of stories is obtained for the OIT2FOFPIDC over the OT1FPIDC, respectively. Similarly, these reductions in comparison with the OIT2FPIDC are 16.3%, 13.3%, and 12.0%. Also, these reductions, in comparison with the OPIDC, are 33.3%, 27.8%, and 25.8%. Furthermore, simulation results show that the OIT2FOFPIDC is more robust than the other proposed controllers against uncertainties due to structural stiffness.

Solid state malic acid esterification on fungal α-amylase treated corn starch: Design of a green dual treatment.

For the first time, the current work applied fungal α-amylase treated corn starch in granular form to produce solid state malate-esterified starch (MES). The pores and channels created on the granules after the enzymatic modification could provide more possibilities for malic acid to esterify the starch, resulting in the increase of substitution degree (0.084) and reaction efficiency (86.6%) compared to NS. Based on the obtained results, the dual treatment significantly increased solubility, amylose content, and syneresis, but reduced transparency, viscosity, digestibility rate, and swelling power compared to those of NS. The occurrence of esterification onto starch chains was confirmed by FT-IR at 1720 cm-1. Other techniques including SEM, XRD, and DSC were employed to examine changes in the structure of starch granules after applying each treatment. Also, the greenness of the combined modification (score: 77) was proved by using a new methodology named Eco-Scale.

A review on the use of chitosan and chitosan derivatives as the bio-adsorbents for the water treatment: Removal of nitrogen-containing pollutants.

Chitosan and its derivatives have been widely used as the adsorbents for different types of water pollutants. This review paper lists various physically and chemically modified chitosan-based adsorbents such as chitosan beads, cross-linked chitosan, chitosan-polymer composites, chitosan-inorganic material composites, and chitosan-metal complexes for the removal of nitrogen-containing pollutants (nitrate, nitrite, ammonia, and ammonium ions) from aqueous solutions. It covers preparation strategies, the effect of modification on adsorbent structure, and the impact of adsorption variables using batch and fixed-bed column studies. In addition to demonstrating the applications of chitosan and its derivatives in the removal of nitrogenous pollutants from water, it helps researchers understand the influence of modification of chitosan on its adsorption capacity as well as physical and chemical properties.

The effects of non-stabilised and Na-carboxymethylcellulose-stabilised iron oxide nanoparticles on remediation of Co-contaminated soils.

A pot experiment was carried out to evaluate the efficiency of six types of non-stabilised and Na-carboxymethylcellulose (CMC)-stabilised iron oxide nanoparticles (α-FeOOH, α-Fe2O3, and Fe3O4) on the immobilisation of cobalt (Co) in a soil spiked with different concentrations of it (5, 25, 65, 125, 185 mg kg-1). Amendments were added to soil samples at the rate of 0.5%, and the samples incubated for 60-days. The addition of amendments significantly decreased the concentrations of DTPA-Co and MgCl2-Co, compared with the unamended control. The highest decrease in concentration of DTPA-Co and MgCl2-Co was obtained by the application of CMC-stabilised Fe3O4 (MC) when the concentration of soil total Co was low (5 and 25 mg kg-1) and by the use of CMC-stabilised α-FeOOH (GC) when the concentration of soil total Co was high (65, 125, and 185 mg kg-1), as compared to the control. CMC-stabilised iron oxide nanoparticles were more effective than non-stabilised nanoparticles in the immobilisation of Co. To investigate the effectiveness of iron oxide amendments on the chemical species of Co in the soil spiked with 65 mg kg-1 of this metal, sequential extraction was performed. The concentration of EXCH (exchangeable) and CARB (carbonate) bound fractions decreased significantly after treatment by different amendments. In particular, GC reduced the concentration of EXCH and CARB bound fractions by 20.87, and 17.52%, respectively, compared with the control. Also amendments significantly increased the concentration of FeMn-OX (Fe-Mn oxides), and OM (organic matter) bound, and RES (residual) fractions.

Exploiting agarose gel modified with glucose-fructose syrup as a green sorbent in rotating-disk sorptive extraction technique for the determination of trace malondialdehyde in biological and food samples.

This research reports for the first time on the application of agarose gel impregnated with high fructose corn syrup (AG/HFCS) as a biodegradable and eco-friendly extraction phase in rotating-disk sorptive extraction (RDSE). The gel disk is driven by a rotary rod attached to an electric stirrer during extraction. Malondialdehyde (MDA) was chosen as a model analyte, and was extracted from biological and food samples using the proposed technique after derivatization with 2-thiobarbituric acid (TBA). Due to the hydrophilic nature of the sorbent phase, MDA was concentrated efficiently. After extraction, MDA was quantified directly in the gel disk by solid phase visible spectrophotometry and smartphone-based Red-Green-Blue (RGB) detection. The procedure used no organic solvents, showed clear advantages in terms of simplicity and short analysis time (5 min), and showed potential as a green analytical method. The extraction procedure was studied and optimized to maximize the partition of MDA into the gel. Under optimized conditions, the method provided linear dynamic ranges of 5.5-1000 ng mL-1 for biological samples and 62.5-12500 ng g-1 for food samples with correlation coefficients (R2) higher than 0.9975, relative recoveries between 88.3 and 103.3% along with relative standard deviation (RSD) values less than 3.5%. Accordingly, the proposed method can be employed by analytical laboratories for the rapid determination of MDA in complex matrix of body fluids and food samples under the principles of green chemistry.

An analytical strategy based on the combination of ultrasound assisted flat membrane liquid phase microextraction and a smartphone reader for trace determination of malondialdehyde.

In the present work, a new cleanup process entitled ultrasonic assisted flat membrane liquid phase microextraction (UA-FM-LPME) was introduced. The UA-FM-LPME procedure in two phase format was applied for the extraction-preconcentration of malondialdehyde (MDA) as an analyte model from the biological samples after a derivatization reaction. In the designed extraction setup, the simultaneous use of two flat sheet membranes and the application of ultrasonic radiation provided the efficient mass transfer of MDA into the acceptor phase in a short extraction time (2 min). The collected organic phase was then analyzed through Red-Green-Blue (RGB) image analysis and high-performance liquid chromatography coupled with ultraviolet-visible spectroscopy (HPLC-UV/Vis) as detection methods. The key parameters affecting the extraction process were studied and optimized in detail. The effect of the sugaring out on the partition of MDA into the extraction phase was examined for the first time. Under optimal conditions, linearity was observed in the concentration range of 8-1000 ng mL-1 for HPLC, and 10-1000 ng mL-1 for RGB analysis, with the coefficient of determination (R2) values higher than 0.9973. The introduced method also offered satisfactory relative standard deviations (RSDs) less than 4.0%. In order to examine the reliability of the technique in complicated matrices, three different biological samples (urine, saliva and blood plasma) were analyzed and the acceptable results in terms of relative recoveries (89.7-102.4%) were obtained. The designed setup in combination with RGB analysis will provide a low-cost alternative technique for rapid determination of MDA in clinical diagnosis or biochemical analysis without the need to complex, time consuming and expensive analytical instruments.

A simple magnetic solid-phase extraction method based on magnetite/graphene oxide nanocomposite for pre-concentration and determination of melamine by high-performance liquid chromatography.

In this study, a clean and simple magnetic solid-phase extraction (MSPE) procedure using magnetite/graphene oxide nanocomposite as an adsorbent was developed for melamine separation and preconcentration from water and dairy products. After synthesis and characterization of the adsorbent, adsorption isotherms and kinetic studies of the adsorption were carried out. The analyte quantification was performed by reversed phase high-performance liquid chromatography after elution of the preconcentrated analytes from the adsorbent surface. Several factors affecting the extraction/preconcentration procedure such as pH, adsorbent amount, extraction time, sample volume, type, and volume of eluent were investigated. The optimizing of some important parameters was assessed by employing a response surface method. The constructed calibration curve in the optimized conditions is linear in the working range of 0.10-100 µg L-1 with a correlation coefficient of 0.9999. The detection limit, limit of quantification, and enrichment factor are 0.03 µg L-1, 0.10 µg L-1, and 500, respectively. The melamine relative recoveries from different real samples are between 97.20 and 103.10% with relative standard deviations of 1.07-4.98%.

Homogenizer assisted dispersive liquid-phase microextraction for the extraction-enrichment of phenols from aqueous samples and determination by gas chromatography.

In this research, dispersive liquid-phase microextraction has been used for the extraction of some phenols including phenol, 3-methylphenol, 4-nitrophenol, 2-chlorophenol, tert-buthylphenol from aqueous samples, and then the analysis was done by the gas chromatography-flame ionization detector technique. For the first time, a laboratory homogenizer has been applied for dispersing of extracting organic solvent. To improve the chromatographic behavior, acetic anhydride was used as a derivatization reagent of the analytes. The effective parameters on the extraction and derivation process such as extraction solvent type and volume, amount and time of derivatization, sample pH and ionic strength, homogenization time and speed were investigated and optimized. The analytical performances of the method, such as linear dynamic range, repeatability, and detection limit were evaluated under the optimum condition. Under the optimal experimental conditions, the calibration plots were linear the range of 1-500 µg L-1 with the detection limits between 0.1-0.9 µg L-1, and the repeatability in the range of 2.6 to 10.0%. These values vary depend on the compounds. The proposed method was evaluated for the determination of the studied phenolic compounds in different real samples such as river water, tap water and industrial wastewater. The relative recoveries were between 90 and 111%.

Hollow fiber liquid-phase microextraction based on the use of a rotating extraction cell: A green approach for trace determination of rhodamine 6G and methylene blue dyes.

In this work, a novel mode of hollow fiber liquid-phase microextraction (HF-LPME) technique namely rotating extraction cell solvent bar microextraction (REC-SBME) was introduced. The proposed method was applied for the preconcentration of methylene blue (MB) and rhodamine 6G (RG) in some real samples, including soft drink, lipstick, environmental water, and wastewater samples. In the extraction setup, two pieces of hollow fibers were fixed on a mechanical support and immersed in a rotating extraction cell containing the sample solution during the extraction process. The rotation of the extraction cell by using an electric motor led to an enhancement in the mass transfer of the dyes from the sample solution into the organic acceptor phase. In the developed procedure, the UV-Vis spectrophotometry and HPLC-UV/Vis were employed as detection methods for the analysis of the acceptor phase and the obtained results were compared. Optimization of the extraction factors affecting the method, including organic solvent type, sample solution pH, extraction time, rotational rate, the volume of sample and acceptor solutions, salt addition, and temperature was performed in order to obtain the best preconcentration factor. Linear dynamic range obtained by HPLC-UV/Vis and spectrophotometry was observed in the ranges of 2.5-1200 ng mL-1 for RG and 1.6-600 ng mL-1 for MB with R2 more than 0.9971. Also, relative standard deviation (RSD) values (n = 3) less than 3.8% were obtained. The good conformity of the obtained results makes UV-Vis spectrophotometric method an ideal tool for routine analysis of trace dyes in the complex matrices after REC-SBME.

Solvent stir bar microextraction technique with three-hollow fiber configuration for trace determination of nitrite in river water samples.

In this work, trace determination of nitrite in river water samples was studied using solvent stir bar microextraction system with three-hollow fiber configuration (3HF-SSBME) as a preconcentration step prior to UV-Vis spectrophotometry. The obtained results showed that the increase in the number of solvent bars can improve the extraction performance by increasing the contact area between acceptor and sample solutions. The extraction process relies on the well-known oxidation-reduction reaction of nitrite with iodide excess in acidic donor phase to form triiodide, and then its extraction into organic acceptor phase using a cationic surfactant. Various extraction parameters affecting the method were optimized and examined in detail. Detection limit of 1.6 µg L-1 and preconcentration factor of 282 can be attained after an extraction time of 8 min under the optimum conditions of this technique. The proposed method showed a linear response up to 1000 µg L-1 (r2 = 0.996) with relative standard deviation values less than 4.0%. The accuracy of the developed method was assessed using the Griess technique. Finally, the proposed method was successfully employed for quantification of nitrite in river water samples (Ghezelozan, Zanjan, Iran).

Removal of sulfamethoxazole antibiotic from aqueous solutions by silver@reduced graphene oxide nanocomposite.

In the present study, the synthesizing of silver@reduced graphene oxide nanocomposite, through a facile precipitation method, is reported. In this method, in the synthesizing step, reduced graphene oxide was applied as a support, silver acetate as a precursor of Ag0, and sodium hydroxide as a medium for reducing procedure. Then synthesized particles were characterized by using transmission electron microscopy analysis, Fourier-transform infrared spectroscopy, field emission scanning microscopy/energy dispersive X-ray, and X-ray diffraction. Adsorbent potentials of the prepared nanocomposite were evaluated for sulfamethoxazole removal from polluted aqueous solutions via two different experimental methods, namely, "one-at-a-time" and "central composite design". The given results from the one-at-a-time method confirms that 0.007 g of silver@reduced graphene oxide nanocomposite can remove 88% (188.57 mg/g) of sulfamethoxazole from a 0.05 dm3 solution (initial concentration 30 mg/dm3) at pH = 5 after 3600 s' contact time. However, in the central composite design method, the optimum condition was 95% (79.17 mg/g) uptake of this drug from 0.05 dm3 of polluted solution with initial concentration of 30 mg/dm3 and pH = 7.5, using 0.018 g of the adsorbent in 3600 s. The main mechanism for sulfamethoxazole removal can be suggested as a suitable interaction between S atoms in functional groups in the drug and Ag atoms on the surface of nanoparticles. The pseudo-second-order patterns and Freundlich model described the empirical data isotherm and kinetics for the adsorption processes, respectively. The maximum adsorption capacity by experimental and theoretical isotherm methods (Langmuir) obtained 250 and 357 mg/g, respectively. Efficiency of the adsorbent in treatment of SMX from real samples displayed less hardness and electrical conductance samples have the maximum uptake percent while existence of nitrate ions in the solutions did not induce any negative effect on the removal of the SMX. All obtained results indicated loading of Ag nanoparticles on rGO nanosheets is an effective strategy for SMX uptake with high proficiency and shows great promise as pollutant adsorbent for environmental applications.

A four-hollow fibers geometry of revolving solvent bar microextraction setup for the enrichment of trace ammonia.

In this work, for the first time, a revolving solvent bar microextraction (RSBME) system was introduced as an efficient alternative method to conventional SBME. The setup proposed for RSBME provides a stable and repeatable method to increase the preconcentration factor. In order to provide the maximum extraction capacity of the organic acceptor phase, four-hollow fibers were applied. In this setup, an electrical motor driving rotator was employed as mechanical support for the hollow fibers and also to stir the donor phase during extraction time. The applicability of this technique was assessed by preconcentration-determination of ammonia in the environmental water samples. The effective factors on the RSBME efficiency were examined and optimized. Under the optimized RSBME conditions, ammonia was quantified by microcell UV-Vis spectrophotometry, with extensive linearity ranging from 15 to 1000 µg L-1 (R2 = 0.9972), and RSD values less than 3.5%. A preconcentration of 372-fold with the detection limit of 4.5 µg L-1 was achieved. The green character of this technique was evaluated based on the analytical Eco-Scale tool and compared with a reference method. The setup proposed can be applied for the simultaneous extraction of acidic and basic compounds from biological and environmental samples in the near future.

Distribution pattern and pollution status by analysis of selected heavy metal amounts in coastal sediments from the southern Caspian Sea.

Amounts of heavy metal elements (Zn, Cd, Pb, Cu, Ni, Co, Mn, and Fe) in surficial sediments at four regions (coastline, estuaries, rivers discharging into the sea, and Gorgan Bay) along the southern coastline of the Caspian Sea were investigated in summer 2015. Collected data was applied to appraise the sediment contamination degree and the origin of pollutants based on the Geo-accumulation Index. Pollution status was assessed via the Enrichment Factor (EF) and the Potential Ecological Risk Index (PERI, the Hakanson index). Heavy metal contents in sediments in mg g-1 dw varied from 3000 to 39,500 for Fe, 166.66 to 2000 for Mn, 11 to 4198 for Zn, not detected (ND) to 822.83 for Pb, ND to 40.66 for Cd, 6.16 to 37.16 for Cu, 11.66 to 69 for Ni, and 6.33 to 33.00 for Co. Higher amounts of Cd, Pb, Cu, Mn, and Fe were determined in rivers discharging sediments into the sea. In Gorgan Bay, Zn, Ni, and Co were highest. Greater potential ecological risk levels were detected along the coastline as well as rivers discharging into the sea. Among heavy metals considered, Zn and Cd had the highest enrichment factors. The Geo-accumulation Index proved that the investigated region could be classified as Zn- and Cd-polluted area.

Preconcentration of morphine and codeine using a magnetite/reduced graphene oxide/silver nano-composite and their determination by high-performance liquid chromatography.

A novel magnetic solid-phase extraction technique based on a ternary nano-composite, magnetite/reduced graphene oxide/silver, as a nano-sorbent was developed for simultaneous extraction/preconcentration and measurement of morphine and codeine in biological samples by high-performance liquid chromatography. The magnetic ternary nano-composite was synthesized and its functional groups, morphological structure, and magnetic properties were characterized by field emission scanning electron microscopy, vibrating sample magnetometer, powder X-ray diffraction, energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy. The optimizing of the significant variables affecting the extraction process was evaluated by a response surface methodology. In the optimized conditions, the constructed calibration curves for morphine and codeine are linear in the range of 0.01-10 µg L-1 with correlation coefficients of 0.9983 and 0.9976, respectively. The detection limit and enrichment factor for morphine and codeine are 1.8 ng L-1, 1000 and 2.1 ng L-1, 1000, respectively. The presented technique was employed for the monitoring of morphine and codeine in numerous blood and urine samples with relative recoveries between 97.0 and 102.5%, and relative standard deviations of 1.02-5.10% for the spiked samples.

Heavy metals and arsenic content in water along the southern Caspian coasts in Iran.

Due to the importance of pollution monitoring in marine ecosystems and lack of a coherent and systematic investigation of heavy metal ions along the southern shores of the Caspian Sea, in the present study, the amount of these metals and As ions in coastal waters along its 780-km-long coast in Iran have been studied. Heavy metals (cobalt, nickel, copper, zinc, cadmium, mercury, lead) and a poisonous metalloid (arsenic) were selected in 59 sampling stations and determined using differential pulse polarography method. The multivariate statistical tools were applied to describe and interpret the experimental data. The overall mean concentrations of studied metals (in microgram per liter; µg L-1) in the samples were found in the order Zn (10.9) > Ni (7.4) > Cu (5.5) > Pb (1.9) > Hg (1.4) > As (1.3) > Co (1.1) > Cd (0.2). The results when compared with reported international standards confirmed that the sampled waters do contain some of these elements above the suggested maximum permissible limits. Hg and Cu were detected in 54.2 and 72.9% of the samples, almost all above the permissible limits. Ni, Zn, Pb, and Co were detected in 100, 96.6, 93.2, and 88.1%, respectively, while 8.5, 22.0, 3.4, and 1.7% were above the permissible limits. Cd and As were present in 61 and 93% of the samples, and their concentrations were higher than the rate presented by Russian System of Management Chemicals (RSMC). In addition, spatial distribution of heavy metal concentrations showed that Gorgan Bay is an ecosystem serving as a filter, trapping natural and anthropogenic materials that are brought from industrial, commercial, and urbanized areas. The multivariate data analysis reveals that Caspian Sea is contaminated by both anthropogenic as well as pedo-geochemical sources.

Solvent-stir bar microextraction system using pure tris-(2-ethylhexyl) phosphate as supported liquid membrane: A new and efficient design for the extraction of malondialdehyde from biological fluids.

A novel and efficient device of solvent stir-bar microextraction (SSBME) system coupled with GC-FID detection was introduced for the pre-concentration and determination of malondialdehyde (MDA) in different biological matrices. In the proposed device, a piece of porous hollow fiber was located on a magnetic rotor by using a stainless steel-wire (as a mechanical support) and the whole device could stir with the magnetic rotor in sample solution cell. The device provided higher pre-concentration factor and better precision in comparison with conventional SBME due to the reproducible, stable and high contact area between the stirred sample and the hollow fiber. Organic solvent type, donor and acceptor phase pH, temperature, electrolyte concentration, agitation speed, extraction time, and sample volume as the effective factors on the SSBME efficiency, were examined and optimized. Pure tris-(2-ethylhexyl) phosphate (TEHP) was examined for the first time as supported liquid membrane (SLM) for the determination of MDA by SSBME method. In contrast to the conventional SLMs of SBME in the literature, the SLM of TEHP was highly stable in contact with biological fluids and provided the highest extraction efficiency. Under optimized extraction conditions, the method provided satisfactory linearity in the range 1-500 ng mL-1, low LODs (0.3-0.7 ng mL-1), good repeatability and reproducibility (RSD% (n = 5) < 4.5) with the pre-concentration factors higher than 130-fold. To verify the accuracy of the proposed method, the traditional spectrophotometric TBA (2-thiobarbituric acid) test was used as a reference method. Finally, the proposed method was successfully applied for the determination and quantification of MDA in biological fluids.