Polytetrafluoroethylene physisorption-assisted emulsification microextraction as a cleanup and preconcentration step in the gas chromatography determination of aliphatic hydrocarbons in marine sediment samples.

For the first time, the application of polytetrafluoroethylene powder as an extractant phase collector or holder in liquid-phase microextraction has been developed. For this purpose, the analytical performances of two different ways of applying polytetrafluoroethylene powder in microextraction methods including polytetrafluoroethylene physisorption-assisted emulsification microextraction and dispersive liquid-phase microextraction via polytetrafluoroethylene extractant phase holders have been compared for analysis of aliphatic hydrocarbons in aqueous phases. Under the same conditions, the former showed better extraction efficiencies over the latter and as a result, it was applied as preconcentration and cleanup step in the analysis of aliphatic hydrocarbons in sediment samples followed by gas chromatography analysis. The linearity of the polytetrafluoroethylene physisorption-assisted emulsification microextraction method was obtained over a range of 3.7 and 2000 ng/g (R2 > 0.993). The relative standard deviations were less than 6.5% (n = 3). The limits of detection and quantification obtained by this method were 1.1-9.0 and 3.7-30 ng/g, respectively, indicating that satisfactory results were achieved by the procedure.

Trace determination of lead, chromium and cadmium in herbal medicines using ultrasound-assisted emulsification microextraction combined with graphite furnace atomic absorption spectrometry.

INTRODUCTION: The World Health Organization (WHO) recommends that medicinal plants should be checked for the presence of heavy metals. A preconcentration and separation technique for trace amounts of heavy metals from plant matrix is necessary in order to increase the sensitivity and precision of their determination. OBJECTIVE: Lead, chromium and cadmium contaminations in herbal medicines were monitored using ultrasound-assisted emulsification microextraction (USAEME) combined with graphite furnace atomic absorption spectrometry (GF-AAS). METHODS: In this work, the metal ions in the aqueous solution were complexed with ammonium pyrrolidine dithiocarbamate (APDC) and were extracted into 45 µL of toluene that was sonically dispersed in the aqueous phase. The emulsion formed was centrifuged and 20 µL of separated toluene was injected into a GF-AAS for analysis. Several factors including the kind of extraction solvent and its volume, sample pH, ionic strength and concentration of APDC were optimised. RESULTS: The linear dynamic range (LDR) values were in the range of 0.05 to 20 µg/L and the limit of detection values were in the range of 0.002-0.03 µg/L for target heavy metals. Enrichment factors were obtained in the range of 70-500. The precision of the proposed method was ≤ 8% (n = 5). The obtained amounts of Pb, Cr and Cd in selected herbal medicines were in the standard range, according to the WHO reports. CONCLUSION: The USAEME with GF-AAS procedure was shown to be an efficient, rapid, inexpensive and eco-friendly method for the determination of lead, chromium and cadmium in herbal medicines. Application of the USAEME method leads to an increased extraction efficiency with satisfactory precision in a short time using an extraction solvent volume at the microlitre level.

Spatial and seasonal variations in suspended particulate matter concentration and composition in the Persian Gulf: From dust deposition and sediment resuspension to biological production in the regulation of the particulate trace elements.

The present document is intended to fill the knowledge gap on spatiotemporal variation of suspended particulate matter (SPM) concentration and composition by collecting samples from 26 stations during two contrasting seasons of summer and winter. The horizontal distribution of surface SPM is characterized by hotspots (up to 4.0 mg/l) along the river estuaries which sharply declined to <1 mg/l in the offshore region. The average SPM concentration for surface, 25 m, and near-bottom decreased from summer to winter by a factor of 1.1, 1.3, and 1.7, respectively. In the offshore region, the particle composition was dominated by particulate organic matter which accounted for 66 % of bulk SPM. The concentration of opaline silica increased from summer to winter presumably from the bloom of diatoms. The concentration of particulate trace elements in winter decreased in the order of Fe â‰« Ba > Mn ≈ Zn > Ni ≈ Cr â‰« Pb > Cd. The non-crustal portion is the predominant fraction for most trace metals and shows enrichment relative to the upper continental crust, local soil background, and deposited dust that is highest for Cd and lowest for Mn.

A note on the silent decline of the Caspian environment.

The Caspian Sea, the world's largest enclosed water body, experiences significant transformations in its physico-chemical properties and a decline in bioresources due to extensive anthropogenic activities. These activities include the discharge of diverse pollutants and bio-physical alterations such as over-fishing, hunting, and physical alterations to rivers. While acute manifestations such as a fall in the Caspian water levels and wetland desiccation are more overt, the pervasive impact of human activities contributes to a likely irreversible decline in environmental quality that we aim to spotlight in this discussion in order to facilitate its restoration.

Ultrasound-assisted emulsification microextraction combined with injection-port derivatization for the determination of some chlorophenoxyacetic acids in water samples.

An efficient method based on ultrasound-assisted emulsification microextraction followed by injection-port derivatization GC analysis was developed to determine 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-methylphenoxyacetic acid (MCPA) in natural water samples. In this procedure, 12.5 µL of 1-undecanol was injected slowly into a 12 mL home-designed centrifuge glass vial containing an aqueous sample of the analytes located inside an ultrasonic water bath. The resulting emulsion was centrifuged, and 1 µL of the separated organic solvent together with 1 µL of the derivatization reagent were injected into a GC equipped with a flame ionization detector. Several factors that influence the derivatization and extraction were optimized. Under the optimal conditions, the LODs were 0.33 and 1.7 µg/L for MCPA and 2,4-D, respectively. Preconcentration factors of 670 and 836 were obtained for MCPA and 2,4-D, respectively. The precision of the proposed method was evaluated in terms of repeatability, which was <5.7% (n = 5). The applicability of the proposed method was evaluated by extraction and determination of chlorophenoxyacetic acids from some natural waters, which indicated that the matrices of natural waters have no significant effect on the extraction and derivatization efficiency of this method.

Determination of abamectin in citrus fruits using SPE combined with dispersive liquid-liquid microextraction and HPLC-UV detection.

A new pretreatment method, SPE combined with dispersive liquid-liquid microextraction, was proposed for the determination of abamectin in citrus fruit samples for the first time. In this method, fruit samples were extracted by ultrasound-assisted extraction followed by SPE. Then, the SPE was used as a disperser solvent in the next dispersive liquid-liquid microextraction step for further purification and enrichment of abamectin. The effects of various parameters on the extraction efficiency of the proposed method were investigated and optimized. Good linearity of abamectin was obtained from 0.005 to 10.0 mg/kg for B1a and from 0.05 to 10.0 mg/kg for B1b with correlation coefficient (r(2)) of 0.998 for B1a and 0.991 for B1b, respectively. The LODs were 0.001 and 0.008 mg/kg (S/N = 3) for B1a and B1b, respectively. The relative recoveries at three spiked levels were ranged from 87 to 96% with the RSD less than 11% (n = 3). The method has been successfully applied to the determination of abamectin in citrus fruit samples.

Mesozooplankton communities related to water masses in the Persian Gulf and the Gulf of Oman.

The spatial and temporal variations of mesozooplankton in relation to environmental parameters were investigated in the Persian Gulf and the Gulf of Oman. For this purpose, the physicochemical parameters were measured using a CTD probe and mesozooplankton were sampled vertically using a closing net aboard the RV Persian Gulf Explorer during two expeditions. Results showed a relationship between mesozooplankton assemblages and water mass distributions. Four mesozooplankton cluster station groups divided the sampled stations into masses, which was also confirmed by the PERMANOVA test. Overall, ninety taxa were identified that were dominated by copepods and characterized by small cyclopoids. Based on the results the mesozooplankton communities of the Persian Gulf and the Gulf of Oman are mostly shaped by the combined effect of temperature, salinity, and dissolved oxygen that significantly influences mesozooplankton occurrence during summer and spring.

Preparation and evaluation of thermally stable nano-structured self-doped polythiophene coating for analysis of phthalate ester trace levels.

Nano-structured self-doped polythiophene (SPT) electrodeposited in the presence of fluorinated organic acid was applied as a thermally stable conductive polymer-based solid-phase microextraction (SPME) fiber candidate. Quantitative determination of trace levels of phthalate esters including dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), and diethylhexyl phthalate (DEHP) was carried out using this novel fiber, coupling with gas chromatography-flame ionization detector (GC-FID). The SPT coating was proved to be stable at high temperatures (∼350°C) with a high extraction capacity and long lifetime (more than 60 times). Improved temperature resistance was obtained by the presence of sulfonated groups in the backbone of polymer. Thermal stability of novel SPT was superior to common polythiophene (synthesized in LiClO(4) ). The extraction procedure was optimized by means of the Taguchi orthogonal array experimental design with an OA(16) (4(5) ) matrix including extraction temperature, extraction time, salt concentration, stirring rate, and headspace volume. The good linearity was obtained for most compounds with correlation coefficients (R(2) ) of between 0.993 and 0.995. The detection limits were lower than 0.12 ng/mL for dimethyl phthalate, DEP, dibutyl phthalate, and diethylhexyl phthalate. The method was successfully applied to the analysis of water samples with the recoveries from 90±1 to 107±1%.

Mesozooplankton community in near-hypoxic and hypoxic layers of the Persian Gulf and the Gulf of Oman.

To assess the role of near-hypoxic and hypoxic conditions on the mesozooplankton community, we studied twenty stations in the Persian Gulf and the Gulf of Oman. The physicochemical parameters were measured using a CTD probe and mesozooplankton were sampled vertically using a closing net. Results showed the hypoxic conditions of 0.52 ± 0.11, 1.40 ± 0.48, and 0.84 ± 0.08 in the lower layers in stations T11S3, T0S8B, and T9S5 in the Gulf of Oman and near-hypoxic conditions in station T6S3 (2.99 ± 0.05) in the Persian Gulf. The marginal test revealed that stratification during summer and dissolved oxygen and salinity during spring in the Persian Gulf and temperature, stratification, and dissolved oxygen during spring in the Gulf of Oman significantly explained the variation of mesozooplankton composition in the study areas (p < 0.05). The present study reveals some general patterns of mesozooplankton assemblage in near-hypoxic and hypoxic conditions, but a future detailed investigation will be essential.

Electromembrane extraction of levamisole from human biological fluids.

Electromembrane extraction coupled with high-performance liquid chromatography (HPLC) and ultraviolet (UV) detection was developed for the determination of levamisole in some human biological fluids. Levamisole migrated from 4 mL of different acidized biological matrices, through a thin layer of 2-nitrophenyl octyl ether containing 5% tris-(2-ethylhexyl) phosphate immobilized in the pores of a porous hollow fiber, into a 20-µL acidic aqueous acceptor solution present inside the lumen of the fiber. The parameters influencing electromigration were investigated and optimized. Within 15 min of operation at 200 V, levamisole was extracted from different biological fluid samples with recoveries in the range of 59-65%, which corresponded to preconcentration factors in the range of 118-130. The calibration curves showed linearity in the range of 0.5-10, 0.2-10 and 0.1-10 µg/mL for plasma, urine and saliva, respectively. Limits of detection of 0.1, 0.07 and 0.05 µg/mL and limits of quantification of 0.5, 0.2 and 0.1 µg/mL were obtained for plasma, urine and saliva, respectively. The relative standard deviations of the analysis were found to be in the range of 5.6-9.7% (n = 3). Electromembrane extraction was successfully processed for determination of levamisole in plasma, urine and saliva samples.

Hypoxia in the Persian Gulf and the Strait of Hormuz.

In this article dissolved oxygen results of research cruises through the Persian Gulf during 2018-2019 are discussed. The results showed that summer to autumn hypoxia occurred mainly at depths ≥ 50 m to the bottom. This seasonal hypoxia started in late summer reaching its greatest severity in mid-autumn with an area of 50,000 km2 in the Persian Gulf. The minimum oxygen measured at the near-bottom layer of the western basin in autumn (25.8 µmol/kg) was lower than any previous measurement in the open waters of the Persian Gulf. In the Strait of Hormuz, the seasonal hypoxia appeared in summer in the near bottom of the most eastern part at the Iranian side. pHT values recorded in hypoxic waters were as low as what is predicted for surface ocean under ocean acidification in 2100. Considering the results, we suggest evaluating the effects of hypoxia and acidification on the Persian Gulf ecosystems.

The carbonate system on the coral patches and rocky intertidal habitats of the northern Persian Gulf: Implications for ocean acidification studies.

This research characterizes the temporal and spatial variability of the seawater carbonate chemistry on the near-shore waters of the northern Persian Gulf and Makran Sea. In general, normalized total alkalinity (nAT) showed a westward decrease along the coasts of Makran Sea and the Persian Gulf. Intertidal seawater was always supersaturated in terms of calcium carbonate minerals during the daytime. Rocky shore waters in the Persian Gulf were sinks for CO2 in the winter during the daytime. The nAT decreased from Larak to Khargu Island by 81 µmol/kg. As expected, the two hypothetical drivers of bio-calcification, i.e., Ω and the [HCO3-]/[H+] ratio, were significantly related at a narrow range of ambient temperature. However, as data were pooled over seasons and study sites, in contrast to ΩAr, the [HCO3-]/[H+] ratio showed a slight dependence on temperature, suggesting that the ratio should be investigated as a more reliable factor in future biocalcification researches.

Concentration of polycyclic aromatic hydrocarbons in zooplanktons of Bushehr coastal waters (north of the Persian Gulf).

In this study, polycyclic aromatic hydrocarbon contents in zooplanktons of coastal waters of Bushehr Province at the north of the Persian Gulf were evaluated. Zooplankton samples were collected from 18 stations in both summer and winter (2017), and their polycyclic aromatic hydrocarbon contents were measured by gas chromatography-mass spectrometry after ultrasound-assisted extraction. Results revealed that among 16 compounds that were analyzed, only 7 compounds were recognizable at both seasons. Pyrene was the most common individual compound of polycyclic aromatic hydrocarbons, whereas acenaphthene was the least individual compound found at both seasons. Additionally, the highest content of the measured compounds in both summer and winter was 16.4-75.9 ng/g and 17.3-93.7 ng/g, respectively. On the basis of the obtained results, the total concentration of polycyclic aromatic hydrocarbons was significantly higher in winter than in summer (P < 0.05).

Hydrochemistry and nutrient distribution in southern deep-water basin of the Caspian Sea.

In this work, the results of hydrochemical studies aboard the R/V Iran Behshahr in southern Caspian Sea in late-winter 2014 were presented. Salinity, temperature, dissolved oxygen, pH, total dissolved inorganic carbon, total alkalinity, nitrate, phosphate and silicate concentrations in water column of Neka-Amir Kabir oil platform section in the southern Caspian Sea were measured to study the status of hydrochemistry of this area. Results showed that the hypoxia continues to intensify in the deep-water basin of the South Caspian Sea. Near-zero concentration of dissolved oxygen and accumulation of phosphate, silicate and total dissolved inorganic carbon in near-bottom layers in the study area showed that vertical winter mixing of water column did not reach the near-bottom layers at the time of this survey. Nitrate showed its maximum concentration at the intermediate maximum depth of 300m.

Antifouling paint booster biocides (Irgarol 1051 and diuron) in marinas and ports of Bushehr, Persian Gulf.

In the present study, antifouling paint booster biocides, Irgarol 1051 and diuron were measured in ports and marinas of Bushehr, Iran. Results showed that in seawater samples taken from ports and marinas, Irgarol was found at the range of less than LOD to 63.4ngL(-1) and diuron was found to be at the range of less than LOD to 29.1ngL(-1) (in Jalali marina). 3,4-dichloroaniline (3,4-DCA), as a degradation product of diuron, was also analyzed and its maximum concentration was 390ngL(-1). Results for analysis of Irgarol 1051 in sediments showed a maximum concentration of 35.4ngg(-1) dry weight in Bandargah marina. A comparison between the results of this study and those of other published works showed that Irgarol and diuron pollutions in ports and marinas of Bushehr located in the Persian Gulf were less than the average of reports from other parts of the world.

Ecological risk, source and preliminary assessment of metals in the surface sediments of Chabahar Bay, Oman Sea.

In this study, concentrations of Aluminum (Al), Iron (Fe), Chromium (Cr), Copper (Cu), Nickel (Ni), Vanadium (V), Zinc (Zn), Arsenic (As), Cobalt (Co) and lead (Pb) in the surface sediments from Chabahar Bay were studied to assess the degree of heavy metal pollution as a consequence of natural and anthropogenic sources. Metal contents in the sediments were observed in the order of: Al>Fe>Cr>V>Ni>Zn>Cu>>As>Pb>Co. According to enrichment factor (EF), Arsenic was higher than 1.5 at some sites, indicating anthropogenic inputs. Contents of Ni, As and Cr in the some sampling sites were higher than sediment quality guideline implying adverse impacts of these metals. Based on potential ecological risk (PER), the Chabahar Bay had low ecological risk.

Dissolved carbon dioxide flotation: an effective way for phase separation in emulsification microextraction method.

Dissolved carbon dioxide flotation after emulsification microextraction (DCF-EME) technique coupled with gas chromatography-electron capture detection (GC-ECD) was introduced for preconcentration and determination of six organochlorine pesticides (OCPs) in seawater samples. DCF-EME method is based on the rapid and simple phase separation of low density organic solvent from the aqueous phase via introducing of a saturated NaHCO3 solution (9.6% w/v) into the acidified sample solution (0.1M of HCl) containing analytes. Thanks to the in situ generation of carbon dioxide (CO2) bobbles intensified by ultrasound radiation, the dispersed extraction solvent was collected to the surface of the aqueous sample and then was narrowed to the capillary part of a special home-made extraction cell for facile retrieving. Under the optimal conditions, the limits of detection were at the range of 2.6-9.2 ng L(-1) and preconcentration factors were varied between 271 and 307 for different OCPs. The applicability of the developed method was evaluated by the extraction and determination of the target analytes from Caspian seawater samples.

Photosynthetic response of Persian Gulf acroporid corals to summer versus winter temperature deviations.

With on-going climate change, coral susceptibility to thermal stress constitutes a central concern in reefconservation. In the Persian Gulf, coral reefs are confronted with a high seasonal variability in water temperature, and both hot and cold extremes have been associated with episodes of coral bleaching and mortality. Using physiological performance as a measure of coral health, we investigated the thermal susceptibility of the common acroporid, Acropora downingi, near Hengam Island where the temperature oscillates seasonally in the range 20.2-34.2 °C. In a series of two short-term experiments comparing coral response in summer versus winter conditions, we exposed corals during each season (1) to the corresponding seasonal average and extreme temperature levels in a static thermal environment, and (2) to a progressive temperature deviation from the annual mean toward the corresponding extreme seasonal value and beyond in a dynamic thermal environment. We monitored four indictors of coral physiological performance: net photosynthesis (Pn), dark respiration (R), autotrophic capability (Pn/R), and survival. Corals exposed to warming during summer showed a decrease in net photosynthesis and ultimately died, while corals exposed to cooling during winter were not affected in their photosynthetic performance and survival. Coral autotrophic capability Pn/R was lower at the warmer thermal level within eachseason, and during summer compared to winter. Corals exposed to the maximum temperature of summer displayed Pn/R < 1, inferring that photosynthetic performance could not support basal metabolic needs under this environment. Our results suggest that the autotrophic performance of the Persian Gulf A. downingi is sensitive to the extreme temperatures endured in summer, and therefore its populations may be impacted by future increases in water temperature.

Microfunnel-supported liquid-phase microextraction: application to extraction and determination of Irgarol 1051 and diuron in the Persian Gulf seawater samples.

In the present work, microfunnel-supported liquid-phase microextraction method (MF-LPME) based on applying low density organic solvent was developed for the determination of antifoulings (Irgarol 1051, diuron and 3,4-dichloroaniline) from seawater samples. In this method, home-designed MF device was used for facile loading and retrieving of organic solvent during the extraction procedure. The extraction was carried out with introduction of 400 µL of toluene via syringe into the MF device placed on the surface of sample solution (300 mL) containing analytes. After the extraction, extractant layer was narrowed into the capillary part of MF by pushing the device inside the sample and withdrawn by using a syringe to evaporate by nitrogen purging. The residual redissolved into 50 µL methanol, diluted to 100 µL with deionized water and injected into the high performance liquid chromatography with UV detection (HPLC-UV). Several factors influencing the extraction such as the type and volume of extraction solvent, sample pH, extraction time and ionic strength were investigated and optimized. Under the optimized conditions, the limits of detection in seawater were 1.4, 4.8 and 1.0 ng L(-1) for 3,4-dichloroaniline (DCA), diuron and Irgarol 1051, respectively. Enrichment factors were obtained 333, 150 and 373 for DCA, diuron and Irgarol 1051, respectively. The precision of the technique was evaluated in terms of repeatability which was less than 12.0% (n=5). The applicability of the proposed method was evaluated by the extraction and determination of antifoulings from seawater samples collected from harbors of Bushehr located in northern Persian Gulf coast.

Hollow fiber liquid phase microextraction as a preconcentration and clean-up step after pressurized hot water extraction for the determination of non-steroidal anti-inflammatory drugs in sewage sludge.

A method for the quantitative determination of non-steroidal anti-inflammatory drugs (NSAIDs) in sewage sludge was developed and validated. The target compounds were extracted using pressurized hot water extraction (PHWE) and then purified and preconcentrated by three-phase hollow fiber liquid phase microextraction (HF-LPME) followed by LC-ESI-MS analysis. The PHWE was optimized with regard to the pH of solvent as well as other operational parameters. The optimum conditions were 0.01 M NaOH as the extraction solvent, temperature of 120 °C, pressure of 100 bar, static time 5 min, 5 cycles, flush volume 90% and purge time 60s. Spike recoveries for sludge samples spiked at 200 ng g⁻¹ were in the range of 101-109% but for the native drugs in non-spiked sludge samples, recoveries were 38.9%, 59.8%, 90.3% and 47.8% for ketoprofen, naproxen, diclofenac and ibuprofen, respectively. Donor phase pH, ionic strength and extraction time were optimized for HF-LPME after PHWE. The optimum conditions were 2h extraction at pH 1.5 without salt addition. Enrichment factors in the range of 947-1213 times were achieved (extraction recoveries were 23.6-30.3%) for HF-LPME after PHWE. The matrix effect on the ionization of drugs in LC-ESI-MS was also investigated. The results show that there is a smaller matrix effect (-8.9% to +14.6%) in comparison with other published values obtained using solid phase extraction (SPE) for clean-up after pressurized liquid extraction (PLE). Method detection limits (MDLs) and method quantification limits (MQLs) for different drugs were in the range of 0.4-3.7 ng g⁻¹ and 1.5-12.2 ng g⁻¹ in dried sludge samples, respectively. The characteristics of the proposed method were compared with those of other published works. The considerably lower ion suppression/enhancement and minimum use of organic solvents (a few microliters of di-n-hexyl ether) in the sample preparation step are two highlighted advantages of the proposed method in comparison with previously published works. The method was applied to determine NSAIDs in sewage sludge from Källby wastewater treatment plant (Lund, Sweden) in April, June, August and October 2010. The highest concentration level was recorded for ibuprofen in the April sewage sludge sample (588 ng g⁻¹) and all of the selected NSAIDs were detected in all the samples analyzed.