Cloud point extraction of trace cyanide from environmental waters for indirect flame atomic absorption spectrometric determination

A method has been developed for indirect determination of cyanide in environmental waters based on cloud point extraction (CPE), preconcentration and determination by flame atomic absorption spectrometry (FAAS). The method was based on reduction of Cu(II) to Cu(I) in the presence of cyanide and complexation of the produced Cu(I)(CN)₂^? with gallocyanin (GC⁺) as an ion-pairing reagent at pH 4.0, followed by its extraction into polyethyleneglycol mono-p-nonylphenylether (Ponpe 7.5). Selectivity was improved with the use of suitable masking agents. Various factors influencing separation and preconcentration of cyanide have been investigated, and conditions were optimized, allowing determination of cyanide in the range of up to 1.2 mg L^?1 with a detection limit of 0.00045 mg L^?1. The method has been applied to the determination of cyanide in environmental waters, the results being in agreement with those obtained by a reference method.     

Isolation and characterisation of cadmium-resistant bacteria from an industrially polluted coastal ecosystem on the southeast coast of India

A total of 35 bacterial strains were isolated from the industrially polluted Cuddalore coast, on the southeast coast of India. Of these, 17 strains were cadmium resistant and the remainder were sensitive. Six strains (C-1, C-8, C-10, C-12, C-14 and N-1) were selected based on high levels of cadmium tolerance (>150 mg L^?1) and were termed highly cadmium-resistant bacteria (HCRB). These HCRB were identified on the basis of morphological, biochemical and partial sequencing of their 16S rRNA genes. The antibiotic-susceptibility patterns and minimum inhibitory concentrations (MIC) of different metals (Cu²⁺, Pb²⁺ and Zn²⁺) against each HCRB were determined. Among the isolates, C-14 showed high degrees of metal and antibiotic resistance compared with other HCRB. Growth rates of HCRB at two different Cd²⁺ concentrations (50 and 100 mg L^?1) and under different metal conditions (Cd²⁺, Cu²⁺ and Pb²⁺) were also investigated. HCRB growth rates were lower in the metal-treated condition than in the untreated condition. Isolates C-14 and N-1 removed>80% of Cd²⁺ from cadmium-treated broth. However, isolate C-14 removed 92.3% of Cd²⁺ compared with 86.5% for isolate N-1. Bacteria showing residual growth rates under metal stress conditions might be useful in metal removal applications under growing conditions.     

Ligand-less in situ surfactant-based solid phase extraction for preconcentration of silver from natural water samples prior to its determination by atomic absorption spectroscopy

A simple and rapid ligand-less in situ surfactant-based solid phase extraction method for preconcentration of silver from water samples is developed. In this method, a cationic surfactant containing a proper alkyl group (n-dodecyltrimethylammonium bromide) is dissolved in the aqueous sample and then a proper ion-pairing agent (ClO₄^?) is added. Due to the interaction between surfactant and ion-pairing agent, solid particles are formed and used for adsorption of silver carbonate. After centrifugation, the sediment is dissolved in 2.0 mL 1 M HNO₃ in ethanol and then aspirated directly into the flame atomic absorption spectrometer. Variables affecting the extraction efficiencies such as pH, concentrations of surfactant and CO₃^2?, ion pair concentration, and extraction time, are optimized. Under such conditions, the calibration curve is linear from 3 to 700 μg L^?1. Detection limit is 1.1 μg L^?1 with an enrichment factor of 37. The relative standard deviation for eight replicate measurements of 100 μg L^?1 is 2.1%. The method has been applied for the determination of silver in water samples.     

A fast and reliable method for quantitative determination of total mercury in vegetables

A cloud-point extraction (CPE) process using the nonionic surfactant, polyethylene glycol tert octylphenyl ether (Triton X-114) was employed for determination of Hg(II) ions in aqueous solutions. The method is based on the ion-pairing reaction of Hg(II) with Pyronin B (PyrB⁺) in the presence of excess iodide at pH 6.0 and extraction of the complex formed. The chemical variables affecting CPE efficiency were studied, and the analytical characteristics of the method were obtained. The calibration curves were linear in the range of 1–40 μg L^?1 with the detection limits of 0.35 and 0.30 μg L^?1 at 556 and 521 nm. Selectivity was also tested. The coefficients of variation of the method are 2.4% and 5.2% for five replicate measurements of mercury at levels of 10 and 25 μg L^?1, respectively. The results obtained for two certified reference samples were in a good agreement with the certified values. The method was applied to the determination of total mercury in vegetable samples.     

Ultrasound-assisted emulsification/microextraction based on solidification of trace amounts of thallium prior to graphite furnace atomic absorption spectrometry determination

In the present work, determination of ultratrace amounts of thallium in water samples was performed by ultrasound-assisted emulsification microextraction based on solidification of a floating organic drop as sample preparation method prior to furnace atomic absorption spectrometry. 1-(2-Pyridylazo)-2-naphthol was used as chelating agent. The factors influencing the complex formation and extraction, such as pH of the aqueous solution, the type and the volume of extraction solvent, the volume of chelating agent solution, and the extraction time were investigated. Under optimized conditions, the enrichment factor was 200. The calibration graph was linear from 0.2 to 10.0 μg L^?1 with a correlation coefficient of 0.9966, the detection limit was 0.03 μg L^?1 and reproducibility was ±3.3% (C = 5.0 μg L^?1, n = 8). The method was successfully applied for the determination of thallium in water samples.     

Determination of Au(III) and Pd(II) ions by flame atomic absorption spectrometry in some environmental samples after solid phase extraction

A simple and sensitive solid phase extraction method was developed for simultaneous separation and preconcentration of gold and palladium ions with N-(4-methylphenyl)-2-{[(4-phenyl-5-pyridine-4-yl-4H-1,2,4-triazol-3-yl)thio]acetyl}hydrazine carbo thioamide complex on Amberlite XAD-1180 resin before their determination by flame atomic absorption spectrometry. Some analytical parameters such as HNO₃ concentration of the sample solution, amount of complexing agent, sample volume, eluent type and volume, effects of foreign ions and adsorption capacity of the resin were investigated for quantitative recovery of gold and palladium ions. The effects of some anions and cations were also examined. Under optimum conditions, the detection limits for gold and palladium ions were found to be 0.29 and 0.19 μg L^?1, respectively. The preconcentration factor for gold and palladium was 250. After being validated by standard addition and analysis of standard reference material, the procedure was successfully applied to the analysis of sea and stream water, anodic slime, gold ore, soil and electronic waste.     

Immobilized Lentinus edodes residue as absorbent for the enhancement of cadmium adsorption performance

To investigate the potential use of Lentinus edodes (L. edodes) residue for Cd²⁺ adsorption, poly alcohol Na alginate (PVA) was applied to immobilize it. The parameters including contact time, pH, adsorbent dosages, and coexisting metal ions were studied. The suitable pH for immobilized L. edodes was 4?C7 wider than that for raw L. edodes (pH 6?C7). In the presence of Pb²⁺ concentration varying from 0 to 30 mg·L^?1, the Cd²⁺ adsorption ratios declined by 6.71% and 47.45% for immobilized and raw L. edodes, respectively. While, with the coexisting ion Cu²⁺ concentration varied from 0 to 30 mg·L^?1, the Cd²⁺ adsorption ratios declined by 12.97% and 50.56% for immobilized and raw L. edodes, respectively. The Cd²⁺ adsorption isotherms in single-metal and dual-metal solutions were analyzed by using Langmuir, Freundlich, and Dubinin-Radushkevich models. The Cd²⁺ adsorption capacities (q _m) in single-metal solution were 6.448 mg·L^?1 and 2.832 mg·L^?1 for immobilized and raw L. edodes, respectively. The q _m of immobilized L. edodes were 1.850 mg Cd·g^?1 in Cd²⁺ + Pb²⁺ solution and 3.961 mg Cd·g^?1 in Cd²⁺ + Cu²⁺ solution, respectively. The Cd²⁺ adsorption processes subjected to both adsorbents follow pseudo-second-order model. Mechanism study showed the functional group of L. edodes was -OH, -NH, -CO, and PVA played an important role in metal adsorbing. Mining wastewater treatment test showed that PVA-SA-immobilized L. edodes was effective in mixed pollutant treatment even for wastewater containing metal ions in very low concentration.     

A sensitive method for selective determination of vanadium species by dispersive liquid–liquid microextraction (DLLME) with spectrophotometric detection

A simple, fast, and low-cost analytical procedure was developed for trace-level determination of inorganic vanadium species by dispersive liquid–liquid microextraction in combination with spectrophotometry. Vanadium in pentavalent form, V(V), was quantitatively extracted into organic phase as 4-(2-pyridylazo)-recorcinol (PAR) complex in the presence of N-cetyl-N,N,N-trimethyl ammonium bromide (CTAB) as counter-ion. Vanadium (IV) was masked with 1,2-diaminocyclohexanetetraacetic acid to allow speciation analysis. Total vanadium was determined after oxidation of V(IV) to V(V). The main factors affecting preconcentration and spectrophotometric detection of vanadium species such as pH, concentration of PAR and CTAB, the type and volume of the extraction, and disperser solvents were optimized. The limit of detection and enhancement factor obtained under optimum conditions were found to be 0.06 μg L^?1 and 98, respectively. Relative standard deviations for V(IV) and V(V) at 3.0 μg L^?1 were less than 2.4%. The presented procedure was applied to environmental water samples for selective determination of vanadium species. Moreover, the method was applied to determination of vanadium in edible salt samples, due to its applicability in high-NaCl-containing solutions. The validity of proposed method was proven by spike recovery experiments and also independent analysis by inductively coupled plasma mass spectrometry.     

Online solid phase preconcentration using EGDMA–MAA copolymer for lead determination by FAAS

A Ethylene glycol dimethacrylate (EGDMA) methacrylic acid (MAA) resin was used for preconcentration of lead at trace levels in water samples. For this purpose, a flow-injection, solid phase extraction method was developed for the determination of lead by flame atomic absorption spectrometry. Lead ions were sorbed on a EGDMA–MAA column at pH 4, followed by an elution step using 288 µL of 4.0 M nitric acid solution and determination by flame atomic absorption spectrometry. Optimum conditions for quantitative sorption involving the pH, sample volume, loading and elution flow rates, eluent type, and volume were investigated. A 868-fold enrichment factor could be reached. The detection limit for the water samples, estimated from the noise on the signal obtained for 250 mL of 10 µg L^?1 loaded at 4.9 mL min^?1 was 1.04 µg L^?1. The method was applied for lead determination in river water samples collected in Edirne, Turkey. Recoveries of spiked solutions (10 µg L^?1) to river water samples were quantitative. Finally, the method was validated by the analysis of certified reference material SRM 2704 (Buffalo River Sediment).     

Rice seedlings under cadmium stress: effect of silicon on growth,cadmium uptake,oxidative stress,antioxidant capacity and root and leaf structures

In this study, the effect of silicon (Si) addition on cadmium (Cd) toxicity in rice seedlings was investigated. After a series of screening experiments, 50 μmol·L^?1 of Cd and 10 μ mol·L^?1 of Si were selected. Treatment of rice seedlings with Cd (50 μ mol·L^?1) resulted in significant accumulation of this metal in roots and shoots. The data revealed that accumulation of Cd resulted in oxidative stress in rice seedlings as evidenced by increased accumulation of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA; a peroxidation product of lipids). However, addition of Si (10 μ mol·L^?1) together with Cd prevented accumulation of Cd, H₂O₂ and MDA. Antioxidant capacity was decreased by Cd but enhanced by Si addition. Cd decreased the length and frequency of root hairs, stomatal frequency, and distorted leaf mesophyll cells and vascular bundles. However, addition of Si together with Cd reduced these abnormalities. The results showed that addition of exogenous Si protected rice seedlings against Cd toxicity by preventing Cd accumulation and oxidative stress (H₂O₂ and MDA accumulation) by increasing Si accumulation and antioxidant capacity, which maintained the structure and integrity of leaf and root.     

Lipid and fatty acids in naturally occurring particulate matter during spring and summer in a high arctic fjord (Kongsfjorden, Svalbard)

The total lipids and fatty acid composition of natural particulate matter and nutritional quality for zooplankton grazers was studied on a seasonal basis in the Arctic fjord Kongsfjorden (Svalbard) during the spring, summer of 2007 and during the early summer of 2006. Both years were abnormally warm, and the study attempted to evaluate the potential impact of the intrusion of North Atlantic waters. Samples were collected in surface layers and at deep chlorophyll maximum (DCM when present). Both years, chlorophyll concentrations were low (<2 μg L^?1) even during bloom periods. Species determination indicated Phaeocystis spp. as main constituent of the May bloom while ciliates and flagellates dominated the rest of the survey period. Total lipids showed similar changes at both depths with maximum values in mid-summer of 2007, while it showed reverse patterns between surface and DCM in 2006. Total fatty acid composition was dominated by saturates and monoenoic acids at both depths with significant percentages of pentaenoic acids and 22:6n-3 (DHA) recorded at all times. The 2007 fatty acid dynamics identified four main successions in term of particulate assemblage related mainly to the succession of living cells versus detrital material and to a lesser extent to phytoplankton community changes (diatoms versus non-diatoms). Redundancy analysis confirmed that live phytoplankton is one of the main drivers in the fatty acid changes. Temperature and density of the surface water are also influential in relation to water mass dynamics. Concentrations of fatty acids available to consumers showed n-3 PUFA ranging from 2 to 15 μg L^?1 and n-6 PUFA ranging from 0.3 to 2 μg L^?1. Concentration of EPA (20:5) and DHA are potentially limiting, suggesting a negative impact of Phaeocystis pouchetti-type phytoplankton linked to advection of Atlantic waters in relation to global warming of Arctic waters.     

Ultrastructural responses and oxidative stress induced by cypermethrin in the liver of Labeo rohita

The present study was conducted to establish the relationship between selected oxidative stress parameters and ultrastructural responses in liver tissue of Labeo rohita fingerlings exposed to cypermethrin. Fish were exposed to lethal (4.0 μg L^?1) and sublethal (0.4 μg L^?1) concentrations of cypermethrin for a period of 24, 48, 72 and 96 h for acute studies and 1, 5, 10 and 15 days for subacute studies, respectively. Results showed increased catalase (CAT) and protease activity, hydrogen peroxide (H₂O₂), malondialdehyde (MDA), protein carbonyls and free amino acid (FAA) levels at both concentrations. This suggests participation of free-radical-induced oxidative cell injury in mediating the hepatotoxicity of cypermethrin. In corroboration of this, ultrastructural lesions witnessed a reduction in the number of cell organelles, swollen, vacuolated and condensed mitochondria, dilated rough endoplasmic reticulum, and reduced numbers of smooth enodplasmic reticulum, peroxisomes and lysosomes at the lethal (4.0 μg L^?1) concentration. At the sublethal (0.4 μg L^?1) concentration, cytoplasmic vacuolation, condensed, vacuolated and swollen mitochondria, dilated rough endoplasmic reticulum and an absence of hepatocyte microvilli were prominent. Ultrastructural changes were exhibited as subcellular responses due to the imbalance in cellular oxidative status by means of oxidative damage.     

Preconcentration of some trace metal ions on coated alumina modified by 1-((6-(-(2-hydroxynaphthalen-1-yl)methyleneamino) hexylimino) methyl) naphthalen-2-ol

A sensitive and efficient method for preconcentration of trace amounts of some metal ions such as Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Pb²⁺, Cd²⁺, Cr³⁺, and Fe³⁺ ions based on modification of sodium-dodecyl-sulphate (SDS) coated alumina with 1-(6-(-(2-hydroxynaphthalen-1-yl) methyleneamino) hexylimino) methyl) naphthalen-2-ol (HNMAHN) is reported. The method is based on the uptake of these ions following their chelation with HNMAHN and their recovery using a suitable eluent. The influence of parameters such as pH, concentration of ligand and amount of coated alumina, SDS concentration, eluent (type and concentrations), and elution volume on metal ion recoveries are investigated. The preconcentration factor is 150 (10?mL elution volume) for a 1500?mL sample volume. The method has been successfully applied for extraction and determination of these ions content in some real samples. Extraction efficiency is generally >95% with low relative standard deviations between 1.8% and 2.4 %.     

Sorption of cadmium(II) and copper(II) by soil humic acids: temperature effects and sorption heterogeneity

Sorption by humic acids is known to modify the bioavailability and toxicity of metals in soils and aquatic systems. The sorption of cadmium(II) and copper(II) to two soil humic acids was measured at pH 6.0 using ion-selective electrode potentiometric titration at different temperatures. Sorption reactions were studied with all components in aqueous solution, or with the humates in suspension. Adsorption reactions were described using a multiple site-binding model, and a model assuming a continuous log-normal distribution of adsorption constants. Adsorption of Cu²⁺ was more favourable than adsorption of Cd²⁺. The log-normal distribution model provided the closest fit to observations and allowed parameterisation of adsorption data using a mean adsorption constant (log K _μ). Sorption of Cd²⁺ to dissolved humic acids increased slightly in extent and sorption affinity with increasing temperature, but the effect was small (log K _μ 2.96–3.15). A slightly greater temperature effect occurred for sorption of Cd²⁺ to solid-phase humic acids (log K _μ 1.30–2.08). Sorption of copper(II) to both aqueous- and colloidal-phase humates showed more pronounced temperature dependence, with extent of sorption, and sorption affinity, increasing with increasing temperature (log K _μ 3.4–4.9 in solution and 1.4–4.5 in suspension). The weaker adsorption of Cd²⁺ than Cu²⁺, and smaller temperature effects for dissolved humates than suspended humates, suggested that the observed temperature effects had a kinetic, rather than thermodynamic, origin. For any metal-to-ligand ratio, free metal ion concentration, and by inference metal bioavailability, decreased with increasing temperature. The consistency of the data with kinetic rather than thermodynamic control of metal bioavailability suggests that equilibrium modelling approaches to estimating bioavailability may be insufficient.     

Oxidized multiwalled carbon nanotubes modified with 2-(2-hydroxy-5-nitrophenyl)-4,5-diphenyl imidazole for solid phase extraction and preconcentration of some metal ions

In this work, a new procedure for the enrichment of the trace amount of Cu²⁺, Ni²⁺, Co²⁺, Pb²⁺, Fe²⁺, and Zn²⁺ ions based on the utilization of multiwalled carbon nanotubes (MWCNT) modified with 2-(2-hydroxy-5-nitrophenyl)-4,5-diphenyl imidazole as chelating agent prior to their determination by flame atomic absorption spectrometry has been described. The influence of effective parameters including pH, amount of ligand and MWCNT, composition of eluent, and coexisting ions on recoveries of understudy metal ions was examined. At the optimum pH of 5.0, all metal ions were quantitatively sorbed onto the proposed solid phase and completely desorbed with 8?mL of 5.0?mol?L^?1 HNO₃. The detection limit of Cu²⁺, Co²⁺, Ni²⁺, Pb²⁺, Fe²⁺, and Zn²⁺ ions was 1.7, 2.4, 2.3, 2.9, 2.8, and 1.4?µg?L^?1, while the preconcentration factor was 63 for Cu²⁺ and 94 for the other metal ions and relative standard deviations between 1.8 less than 3.0%. The proposed procedure was applied for the analysis of various samples.     

Solar-induced generation of singlet oxygen and hydroxyl radical in sewage wastewaters

Singlet oxygen (¹O₂) and hydroxyl radical (·OH) play an important role in the degradation of pollutants in surface waters. However, the mechanism underlying the photochemical generation of ¹O₂ and ·OH in wastewaters is poorly known. Here we studied the photo-induced generation of ¹O₂ and ·OH in different sewage treatment plant units. The correlation between the generation of ¹O₂ and ·OH and the water constituents was discussed. Our results show that in sewage units the ¹O₂ formation rate ranges from 2.19 × 10^?8 to 6.74 × 10^?8 mol L^?1 s^?1, and the ·OH formation rate ranges from 1.7 × 10^?11 to 3.06 × 10^?10 mol L^?1 s^?1. The average ¹O₂ formation rates in the various sewage units are similar to those in wetland and estuarine waters containing rich dissolved organic matter and 2–4 times higher than those in lake and seawater samples. The average ·OH formation rates of the sewage units are 5–50 times higher than for other water samples reported. The ·OH generation rate increased with the iron content with a correlation coefficient of 0.85, which indicates that the photo-Fenton reaction plays a dominant role in ·OH generation in sewage wastewater.     

Evaluation of the toxicity of tetrabromobisphenol A and some of its oxidation products using a micro-scale algal growth inhibition test

A micro-scale algal growth inhibition (μ-AGI) test using a common micro-plate based fluorometric detection was used to demonstrate the effects of humic substances (HSs) on the toxicity of tetrabromobisphenol A (TBBPA) and its oxidative decomposition products 2,5-dibromo-1,4-benzoquinone (2,5-DBBQ), 2,5-dibromohydroquinone (2,5-DBHQ), 2,6-dibromobenzoquinone (2,6-DBBQ), and 2,6-dibromophenol (2,6-DBP) to Pseudokirchneriella subcapitata. The EC₅₀ values were: EC_50(TBBPA) = 7 mg L^?1, EC_50(2,5-DBHQ) = 7 mg L^?1, EC_50(2,5-DBBQ) = 19 mg L^?1, EC_50(2,6-DBP) = 49 mg L^?1, and EC_50(2,6-DBBQ) = 13 mg L^?1. The toxicity of the chemicals was slightly lower in the presence of HA. The toxicity of TBBPA decomposed by a biomimetic catalytic system consisting of iron (III) 5,10,15,20-tetrakis (p-sulfonatophenyl) porphyrin (Fe(III)-TPPS) and KHSO₅ was also evaluated using P. subcapitata and Chlamydomonas reinhardtii.     

Concentrations of uranium in drinking water and cumulative,age-dependent radiation doses in four districts of Uttar Pradesh,India

The present work deals with the determination of uranium concentrations in drinking and ground water samples by laser fluorimetry and calculation of cumulative, age-dependent radiation doses to humans. The concentrations were found to be between 0.20 ± 0.03 and 64.0 ± 3.6 μg L^?1, with an average of 11.1 ± 1.5 μg L^?1, well within the drinking water limit of regulatory bodies. The concentrations of uranium increase with depth of water samples collection. The estimated annual ingestion dose due to the intake of uranium through drinking water for all age groups varied between 0.2 and 137 μSv a^?1, with an average of 17.3 μSv a^?1. The mean annual ingestion dose is 5% of the global average ingestion dose, for infants, marginally higher than for other age group. Most effective dose values were less than 20 μSv a^?1.     

Spectrophotometric and HPLC method for quantification of Loratadine on swabs for cleaning validation

Cleaning validation is a major challenge in multi-product pharmaceutical industries. UV spectrophotometric and HPLC methods have been developed and validated for determination of residual amount of Loratadine. Both methods were validated for linearity, range, accuracy, precision, and robustness. The limit of quantification was 1 mg L^?1 by UV spectrophotometric method and 0.5 mg L^?1 by HPLC method. A spike recovery study was done on a stainless steel (316 grade) plate and specific residual cleaning level (SRCL) was down to 6 μg 25.8 cm^?2. Recovery was found to be more than 70%. Both methods were simple, highly sensitive, precise, and accurate, and have potential of being useful for routine quality control.     

Solid phase extraction of trace metals from environmental samples using Amberlite XAD-7 loaded with 2-hydroxy-propiophenone-4-phenyl-3-thiosemicarbazone and determination by inductively coupled plasma–atomic emission spectrometry

A method for the solid phase extraction of trace metals, namely Co, Cu, Pb, Ni and Zn, from environmental and biological samples using column Amberlite XAD-7 loaded with 2-hydroxy-propiophenone-4-phenyl-3-thiosemicarbazone (HPPPTSC) and determination by inductively coupled spectrometry (ICP–AES) has been developed. The reagent has the capacity to form chelate complexes with the metals because of three binding sites in the reagent molecule. The optimum experimental conditions for the quantitative sorption of five metals, pH, effect of flow rate, concentration of eluent, sorption capacity and the effect of diverse ions on the preconcentration of analytes have been investigated. The sorption capacity of the resin has 83, 127, 35, 88 and 85?µmol?g^?1 for Co²⁺, Cu²⁺, Pb²⁺, Ni²⁺ and Zn²⁺, respectively. The preconcentration factors for Co²⁺, Cu²⁺, Pb²⁺, Ni²⁺ and Zn²⁺ were 100, 110, 120, 140 and 150, respectively. The accuracy of the proposed procedure was evaluated by standard reference materials. The achieved results were in good agreement with certified values. The proposed method was applied for the determination of trace metals in river water and plant leaves.