Cyclic voltammetry as a screening tool for the fungal degradation of 2,4,6-trinitrotoluene in aqueous media

The use of an electrochemical technique based on cyclic voltammetry (CV) that can be implemented to monitor the degradation of the important nitroaromatic explosive 2,4,6-trinitrotoluene (TNT) in aqueous media when in contact with a microorganism is presented. The microorganism used in this study was an isolated fungus belonging to the Aspergillus genus. In the degradation experiments, during the first 21 days of exposure of the fungal growth to a 68 mg L^?1 TNT aqueous stock solution, the analyte concentration decreased by 44% to 38 mg L^?1 before plateauing through the 58th day of the study. Statistical figures of merit of the technique included linearity in the 1–92 mg L^?1 range and correlation coefficients above 98% for the three reduction peaks of TNT, a limit of detection (LOD) of 3 mg L^?1, a limit of quantification of 10 mg L^?1 and a method precision of 3.8% relative standard deviation (%RSD). Day-to-day and week-to-week repeatability were low at 5.1%RSD and 5.8%RSD, respectively. The results herein exhibit first-order kinetics for the ‘ortho’ nitro group. A clear to yellow colour transition in the control solution and fungi samples suggests the appearance of a TNT metabolite. UV-Vis spectrophotometry supports the presence of a possible derivative of TNT in the fungi samples.     

Determination of Trenbolone Acetate in Cattle Feeds by a Flow Injection Chemiluminescence Method

A flow injection chemiluminescence (CL) method is described for the determination of trenbolone acetate based on the CL generated during its reaction with KMnO₄ in acidic medium. The CL intensity is greatly enhanced by alizarin yellow R. The CL intensity is linear with trenbolone acetate concentration in the range 0.1–100.0 mg L^?1 with a detection limit of 0.05 mg L^?1. The sample throughout is about 90 h^?1 and the relative standard deviation for 2.0 mg L^?1 trenbolone acetate solution is 1.5% (n = 11). The proposed method was applied to the determination of trenbolone acetate in cattle feeds.     

Synthesis of a new ionic imprinted polymer for the extraction of uranium from seawater

The ionic imprinted polymer (IIP) of uranyl ion (UO₂ ²⁺) as the template was synthesized by the formation of binary complexes of UO₂ ²⁺ with 2,4-dioxopentan-3-yl methacrylate as functional monomer followed by thermal copolymerization with ethylene glycol dimethacrylate as cross-linking monomer in the presence of 2,2′-azobisisobutyronitrile as initiator and 1,4-dioxane as porogenic solvent. 50 mmol L^?1 HCl solution was used to leach out UO₂ ²⁺ ions from the IIP. Similarly, the control polymer was prepared under identical experimental conditions without using UO₂ ²⁺ ions. The above synthesized polymers were characterized by infra-red spectroscopy, thermo-gravimetric analysis and Barrett–Emmett–Teller surface area measurement. The maximum adsorption capacities of IIP and CP in (NH₄)₄[UO₂(CO₃)₃] solution were 15.3 and 11.2 mg U g^?1, respectively. The kinetics of adsorption followed a pseudo-second-order rate equation. The prepared IIP was successfully used to extract uranium from real seawater sample.     

Removal of Lead (II) Ions by Poly(2‐octadecyl butanedioic acid): Isothermal and Kinetic Studies

Poly(2‐octadecyl‐butanedioic acid), prepared from polyanhydride PA‐18, possesses novel heavy metal adsorption characteristics. The adsorption capacity of this water insoluble polymer for lead (II) was substantially higher than other heterogeneous adsorbants and is equivalent to those obtained with homogeneous sorbants. The polymer exhibited pseudo‐second‐order kinetics and nearly complete adsorption of lead occurred in 15 min with initial lead (II) concentrations greater than 100 mg · L^?1. Adsorptive behavior was accurately predicted by the Dubinin‐Radushkevich isotherm model. The mean free energy of adsorption of lead (II) onto poly(2‐octadecyl‐butanedioic acid) was determined to be 31.6 kJ · mol^?1, suggesting an ion exchange component to the adsorption mechanism. Gibb's free energy values for this process indicate that it is spontaneous. Adsorption was relatively independent of pH in the range of 3–5, due to the utilization of the sodium carboxylate form of the chelating groups, and was not influenced by high Na⁺ concentration and moderate concentrations (up to 200 mg · L^?1) of Ca⁺². Lead (II) solutions containing 2000 mg · L^?1 Ca⁺² did reduce the adsorption of 2000 mg · L^?1 lead (II) by 28%.     

Properties and Extraction for [Ni(NH3)6]2+ of ATPS-a Formed by Aqueous Cationic–Anionic Surfactant Mixtures

The properties and extraction for [Ni(NH₃)₆]²⁺ of anionic aqueous two-phase systems (ATPS-a) that formed in mixtures of cetyltrimethylammonium bromide (CTAB) and excess sodium dodecyl sulfate (SDS) aqueous solutions were investigated. The results showed that the properties and extraction effects were strongly affected by the surfactant concentration, the temperature of system, and the mole fraction of surfactants. The increase of temperature induces narrower phase region and larger phase volume ratio. In addition, [Ni(NH₃)₆]²⁺ was extracted into the surfactant-rich phase with higher distribution coefficient when the liquid crystal had the birefringent properties. Moreover, the distribution coefficient can be improved through reducing the concentration of surfactant from 0.15 to 0.05 mol · L^?1 or increasing mole fraction of CTAB from 21.9% to 23.1%. The results showed that ATPS of cationic–anionic surfactants was efficient for [Ni(NH₃)₆]²⁺ extraction with distribution coefficients of 13.5 when the total surfactant concentration was 0.05 mol · L^?1, mole fraction of CTAB was 21%, and temperature was 34°C.     

Determination of Vitamins A and E Exploiting Cloud Point Extraction and Micellar Liquid Chromatography

Cloud point extraction and micellar chromatographic methods were developed for determination of vitamins A and E. The stationary phase was C18 and the mobile phase was 3.00% (w/v) SDS, 15.0% (v/v) butyl alcohol and 0.02 mol L^?1 phosphate buffer solution at pH 7.0. The retention times for vitamins A and E were 9.6 and 13.0, respectively. The extraction solution was 100 mmol L^?1 Triton X-100, 650 mg NaCl and 1.0% ascorbic acid at 70°C for 30 min. The method is precise (r.s.d. < 7%), the linear range was from 5.0 up to 360.0 mg L^?1 for both vitamins. Recovery test showed recuperation between 90.2 and 99.2%, and LOD and LOQ of 0.234 and 0.108 mg L^?1, 0.780 and 0.360 mg L^?1 to vitamins A and E were found.     

A fluorescent di-zinc(II) complex of bis-calix[4]arene conjugate as chemosensing-ensemble for the selective recognition of ATP

A triethylene glycol di-imine locked triazole linked bis-calix[4]arene conjugate L has been synthesised and characterised. Conjugate L exhibits high fluorescence enhancement towards Zn²⁺ among the 13 metal ions studied down to a lower detection limit of ～12 ppb. The absorption and visual colour change experiments differentiated the Zn²⁺ from the other metal ions studied. The isolated zinc complex, [Zn₂L] has been used as a chemo-sensing ensemble for the recognition of anions based on their binding affinities towards Zn²⁺. [Zn₂L] was found to be sensitive and selective towards phosphate-bearing species and in particular to adenosine triphosphate (ATP^2 ? ) among the other 20 anions studied as observed based on the changes occurred in the fluorescence intensity. The selectivity of the ATP^2 ?  has been shown on the basis of the changes observed in the emission and absorption spectral studies. The lowest detectable concentration for ATP^2 ?  with the chemo-sensing ensemble [Zn₂L] is 348 ppb in methanol. The fluorescence quenching by the phosphate-based anions has been modelled by molecular mechanics studies and found that the anions possessing two or more phosphate moieties can only bridge between the two zinc centres, and hence those possessing only one phosphate moiety (H₂PO₄^?  and AMP^2 ? ) are ineffective.     

The role of counter-anions in photocatalytic reduction of Ni(II) with a trace amount of titania nanoparticles

The reduction of Ni(II) ion, originated from nitrate or sulfate salts, was investigated based on photo-generated electrons in UV-irradiated TiO₂ aqueous suspensions. Design of experiments, modeling, and process optimization were performed using central composite design of response surface methodology. Influence of pH, temperature, and nickel concentration was investigated based on percentage of reduction efficiency (RE). Under operating conditions of pH = 9.3, T = 40 °C, [Ni(II)]_o = 5 mg L^?1, [TiO₂] = 100 mg L^?1 and after 90 min treatments, 64.8 and 76.1 % RE were achieved for nitrate and sulfate counter-anions, respectively. The higher efficiency obtained with sulfate anion was attributed to the more ionic strength and its interaction with titania nanoparticles. Rate of Ni(II) ions reduction, originated from both of the nickel salts, obeys pseudo-first-order kinetic model. As a relevant criterion, the electrical energy consumption and other criteria were evaluated and were compared with other previously reported processes.     

Determination of Propylene Glycol in Low Volume Plasma and Urine Samples of Neonates by LC with Photodiode Array Detection

In order to enhance the sensitivity and to develop a method suitable for quantification of propylene glycol (PG) in low volume neonate plasma and urine samples, several steps in earlier described high performance liquid chromatographic methods were optimised. Chromatographic separation on a reversed-phase column and ultraviolet detection resulted in cleaner chromatograms without interfering compounds. Linearity of the standard curves was validated in the concentration range 0.25?C50 mg L^?1. The lower limit of quantification was 20 times lower than in earlier described methods. Presented method was suitable for quantification of PG concentrations in low volume neonate plasma (15?C46 mg L^?1) and urine samples (20?C175 mg L^?1) enabling us to document very low renal versus non-renal contribution of PG clearance in neonates.     

Fast Determination of Phenolic Compounds in Brazilian Wines from Vale do São Francisco Region by CE

Six phenolic compounds were separated and determined by capillary zone electrophoresis in red wine from Brazil’s region Vale do São Francisco with total analysis time of 12 min. The limit of detections varied from 1.59 to 2.24 mg L^?1. The relative standard deviations (for n = 6) varied from 0.28 to 3.50 %. The red wine samples analyzed were bought in the local market and the phenolic compound recoveries were in the range of 98–101 %. The concentrations of gallic acid in the samples of wines varied from 16.0 to 42.0 mg L^?1, caffeic acid (3.16–5.18 mg L^?1), syringic acid (5.73–13.0 mg L^?1), kaempferol (2.32–4.33 mg L^?1), quercetin (1.68–4.03 mg L^?1), myricetin (7.52–25.1 mg L^?1). The concentrations found agree with data reported in the literature.     

In Vitro Propagation and Assessment of the Genetic Fidelity of Musa acuminata (AAA) cv. Vaibalhla Derived from Immature Male Flowers

An efficient in vitro propagation method has been developed for the first time for Musa acuminata (AAA) cv. Vaibalhla, an economically important banana cultivar of Mizoram, India. Immature male flowers were used as explants. Murashige and Skoog’s (MS) medium supplemented with plant growth regulators (PGRs) were used for the regeneration process. Out of different PGR combinations, MS medium supplemented with 2 mg L^?1 6-benzylaminopurine (BAP) + 0.5 mg L^?1 α-naphthalene acetic acid (NAA) was optimal for production of white bud-like structures (WBLS). On this medium, explants produced the highest number of buds per explant (4.30). The highest percentage (77.77) and number (3.51) of shoot formation from each explants was observed in MS medium supplemented with 2 mg L^?1 kinetin + 0.5 mg L^?1 NAA. While MS medium supplemented with a combination of 2 mg L^?1 BAP + 0.5 mg L^?1 NAA showed the maximum shoot length (14.44 cm). Rooting efficiency of the shoots was highest in the MS basal medium without any PGRs. The plantlets were hardened successfully in the greenhouse with 96 % survival rate. Random amplified polymorphic DNA (RAPD) and inter-simple sequence repeat (ISSR) markers were employed to assess the genetic stability of in vitro regenerated plantlets of M. acuminata (AAA) cv. Vaibalhla. Eight RAPD and 8 ISSR primers were successfully used for the analysis from the 40 RAPD and 30 ISSR primers screened initially. The amplified products were monomorphic across all the regenerated plants and were similar to the mother plant. The present standardised protocol will find application in mass production, conservation and genetic transformation studies of this commercially important banana.     

Preconcentration of Pb2+ by iron oxide/amino-functionalized silica core–shell magnetic nanoparticles as a novel solid-phase extraction adsorbent and its determination by flame atomic absorption spectrometry

The use of iron oxide/amino-functionalized silica core–shell magnetic nanoparticles for preconcentration of Pb²⁺ followed by its consecutive atomic absorption spectrometry determination is described. Effects of various operating variables, namely, solution pH, initial Pb²⁺ concentration, contact time, adsorbent dosage, sample volume, concentration and volume of desorbing solution, and co-existing ions on solid-phase extraction (SPE) of Pb²⁺ were studied by batch equilibrium technique. The experimental adsorption data were well fitted to the Langmuir isotherm model. The Langmuir adsorption capacity and equilibrium time were found to be 100 mg g^?1 and 20 min, respectively. The adsorption data were also fitted to kinetic pseudo-first-order and pseudo-second-order models. Kinetic studies showed that the adsorption followed pseudo-second-order model. Under the optimal SPE conditions, the enrichment factor, detection limit and relative standard deviation for determination of Pb²⁺ were found to be 211, 1 μg L^?1, and 3.7 % for 50 μg L^?1, respectively. The proposed method was successfully applied to the determination of lead in a real sample with satisfactory results.     

Electrocatalytic Oxidation and Voltammetric Determination of Hydrazine in Industrial Boiler Feed Water Using a Cobalt Phthalocyanine-modified Electrode

Abstract

A carbon paste electrode modified with cobalt phthalocyanine (CPECoPc) was developed and applied to the determination of hydrazine [N₂H₄] in industrial boiler feed water. The CPECoPc exhibited good electrocatalytical activity for hydrazine oxidation at pH 13. A linear correlation was obtained between anodic peak current (I_ap) and hydrazine concentration in the range of 1.25 × 10^?4 to 9.80 × 10^?4 mol L^?1, fit by the equation I_ap = 1.47 + 4.90 × 10⁵ [N₂H₄] with a correlation coefficient of 0.9967. A detection limit of 7.35 × 10^?5 mol L^?1 was obtained. Recovery of hydrazine from three samples ranged between 99.0% and 102.9%. The modified electrode showed no interference by cations commonly present in boiler water, such as K⁺, Na⁺, Ca²⁺, Mg²⁺, Al³⁺, Pb²⁺, and Zn²⁺. The results obtained for hydrazine in boiler water using the proposed modified electrode are in agreement with the data obtained by a standard spectrophotometric method, at the 95% confidence level.     

Removal of lead from aqueous solutions by adsorption with surface precipitation

An activated carbon from Coconut (Cocos nucifera) shells was prepared by physical activation with carbon dioxide and water vapor. The activated carbon obtained has a surface area of 1058 m² g^?1 and such a high micropore volume of 0.49 cm³ g^?1. This carbon was studied for the removal of lead from water. Sorption studies were performed at 30 °C, at different pH and adsorbent doses, in batch mode. Lead precipitation was observed on the surface of the activated carbon. Maximum adsorption occurred at pH 9 for an adsorbent dose of 2 g L^?1. Kinetic studies, at the initial concentration of 150 mg L^?1 of lead, pH 5 and an adsorbent dose of 1 g L^?1, yielded an equilibrium time of 50 h for this activated carbon. The kinetic data were modeled with the pseudo first order, the pseudo second order and the Bangham models. The pseudo second order model fitted the data well. The sorption rate constant (7 × 10^?4 mol^?1 Kg s^?1) and the maximum amount of lead adsorbed (0.23 mol kg^?1) are quite good compared to the data found in literature. Sorption equilibrium studies were conducted in a concentration range of lead from 0 to 150 mg L^?1. In an aqueous lead solution with an initial concentration of 30 mg L^?1, at pH 5, adsorbent dose 1 g L^?1, activated Coconut shell carbon removed at equilibrium 100 % of the heavy metal. The equilibrium data were modeled with the Langmuir and Freundlich equations, of which the former gave the best fit. The Langmuir constants Q_{max eq} (0.23 mol kg^?1) and K_L (487667 L mol^?1) are in good agreement with literature. XPS studies identified adsorbed species as lead carbonates and/or lead oxalates and precipitates as lead oxide and/or lead hydroxide on the activated carbon surface. The Coconut shell activated carbon is a very efficient carbon due to its high surface area, to the presence of many micropores on its surface and to the presence surface groups like hydroxyls promoting adsorption in the porous system and lead crystal precipitation on the activated carbon surface.     

Biosorption behaviors of uranium (VI) from aqueous solution by sunflower straw and insights of binding mechanism

Uranium (VI)-containing water has been recognized as a potential longer-term radiological health hazard. In this work, the sorptive potential of sunflower straw for U (VI) from aqueous solution was investigated in detail, including the effect of initial solution pH, adsorbent dosage, temperature, contact time and initial U (VI) concentration. A dose of 2.0 g L^?1 of sunflower straw in an initial U (VI) concentration of 20 mg L^?1 with an initial pH of 5.0 and a contact time of 10 h resulted in the maximum U (VI) uptake (about 6.96 mg g^?1) at 298 K. The isotherm adsorption data was modeled best by the nonlinear Langmuir–Freundlich equation. The equilibrium sorption capacity of sunflower straw was observed to be approximately seven times higher than that of coconut-shell activated carbon as 251.52 and 32.37 mg g^?1 under optimal conditions, respectively. The positive enthalpy and negative free energy suggested the endothermic and spontaneous nature of sorption, respectively. The kinetic data conformed successfully to the pseudo-second-order equation. Furthermore, energy dispersive X-ray, fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy demonstrated that U (VI) adsorption onto sunflower straw was predominantly controlled by ion exchange as well as complexation mechanism. The study revealed that sunflower straw could be exploited for uranium remediation of aqueous streams as a promising adsorbent.     

Detection of Aryloxyphenoxypropionate Herbicides by Enzyme-Linked Immunosorbent Assay

In this study, we developed a general and broad class-selective indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) for detecting aryloxyphenoxypropionate herbicides. A multideterminant artificial antigen was prepared from haptens of two herbicides (fenoxaprop-p-ethyl and cyhalofop-butyl) conjugated to the carrier protein Bovine serum albumin (BSA). The polyclonal antibodies (PAbs) were obtained by immunizing New Zealand white rabbits. Characterization studies of the PAbs showed that they had high affinity and specificity for the two herbicides. The 50% inhibitory concentration (IC₅₀) values for fenoxaprop-p-ethyl and cyhalofop-butyl were 0.185 mg L^?1 and 0.045 mg L^?1 with a limit of detection (LOD, IC₁₀) of 0.004 mg L^?1 and 0.002 mg L^?1, respectively. There were no obvious cross-reactivities with most of the aryloxyphenoxypropionates tested, except for metamifop (CR% = 55.56%). The recoveries of fenoxaprop-p-ethyl, cyhalofop-butyl and metamifop in environmental and agricultural samples (tap water, paddy water, soil, rice and soybean) ranged from 86.86–114.52%, 82.07–119.11% and 82.51–114.46%, respectively. These results demonstrate that the established ELISA could be used as a tool for detecting aryloxyphenoxypropionate multiresidues.     

Determination of Sb(III) and Total Sb in Antileishmanial Drugs by Spectrophotometric Flow‐Injection Hydride Generation

Abstract

A spectrophotometric procedure based on hydride generation and flow analysis is proposed for determination of antimony (III) [Sb(III)] and total antimony (Sb) in pharmaceutical samples. Firstly, Sb(III) reacts with hydrogen species generated in the system, forming antimony hydride. The reaction leads to a decrease in the permanganate concentration and, hence, in the intensity of the color of this specie, which is spectrophotometrically measured at 528 nm. Total Sb is determined as Sb(III) after Sb(V) reduction using 0.02% (m/v) KI. Some parameters, such as the number of channels of the gas phase separator, injection volume, coil length, and KBH₄ concentration, are investigated. The system presents a frequency of ca. 100 h^?1 and precision <3.0% [expressed as relative standard deviation (RSD) of 30 measurements using a 3.0 mg L^?1 Sb(III) solution]. The analytical curve ranging from 0.5 mg L^?1 to 5.0 mg L^?1 (r>0.998; n=5) permits limit of detection (LOD) and limit of quantification (LOQ) of 83 and 250 µg L^?1. For total Sb, the accuracy is checked by atomic absorption spectrometry applying the t test and the results are in accordance at the 95% confidence level. Recovery tests are used to check the accuracy for Sb(III) determination, and the recoveries are between 95% and 105%.     

HPLC Method for the Determination of the Purity of K[Pt(NH3)Cl3], a Precursor of the Platinum Complexes with Cytostatic Activity

K[Pt(NH₃)Cl₃], a valuable precursor for the preparation of platinum complexes with cytostatic activity, e.g. satraplatin, picoplatin, LA-12 and cycloplatam, is currently prepared from cis-[Pt(NH₃)₂Cl₂] or K₂[PtCl₄] and these are the usual impurities in the final product. A simple, selective and sensitive HPLC-UV analytical method for the determination of the purity of K[Pt(NH₃)Cl₃] and the quantification of the impurities has been developed and validated. The platinum complexes present in the final product were separated on a strong base ion exchange column by the gradient elution with detection at 213 nm. Intra-assay precisions for the platinum complexes respective to their ions ([PtCl₄]^2?, [Pt(NH₃)Cl₃]^? and cis-[Pt(NH₃)₂Cl₂]) were between 0.1 and 2.0% (relative standard deviation); intermediate precisions were between 1.4 and 2.0% and accuracies were between 98.6 and 101.4%. Limits of detection of [PtCl₄]^2?, [Pt(NH₃)Cl₃]^? and cis-[Pt(NH₃)₂Cl₂] were 6 µg · ml^?1, 13 mg · ml^?1 and 5 µg · ml^?1 respectively, limits of quantification of [PtCl₄]^2?, [Pt(NH₃)Cl₃]^? and cis-[Pt(NH₃)₂Cl₂] were 51 µg · ml^?1, 55 mg · ml^?1 and 20 µg · ml^?1 respectively.     

Anatomical and Biochemical Characteristics of Achnatherum splendens (Trin.) Nevski Seedlings Stressed on Pb2+

Lead is a heavy metal that usually accumulates in the environment as a hazardous pollutant. Achnatherum splendens (Trin.) Nevski seedlings facilitate the purification and disposal of urban and industrial sewage; however, the detailed mechanism of this phytoremediation is still unknown. In the present study, we investigated the effect of lead (Pb²⁺) stress on the anatomical and biochemical characteristics in A. splendens seedlings using microscopy and proteomic analysis. Our results showed that starch grains accumulate in the cell as the concentration of Pb²⁺ increases. Several organelles such as the nucleus, mitochondria, and chloroplasts were found to be damaged as a result of Pb²⁺ stress. However, the cell wall and the vacuole compartmentalization could reduce the heavy metal poison. The number of total proteins decreased as Pb²⁺ concentration increased. Furthermore, the low molecular weight protein played an important role in resistance to heavy metal Pb²⁺ stress. Peroxidase (POD) and amylase activities were still high at concentrations of 200 and 160 mg L^?1 Pb²⁺, respectively. The ATPase activity was in the top peak at a concentration of 80–160 mg L^?1 Pb²⁺. Thus, these three enzymes were involved in resistance against Pb²⁺ stress. The content of proline increased with the increased concentration of Pb²⁺. Malondialdehyde (MDA) and soluble sugar peaked at concentrations of 160 and 80 mg L^?1 Pb²⁺, respectively. Our results indicated that the last three organic compounds were involved in resistance against Pb²⁺ stress.     

Assessing effects of pH,metal ion and natural organic matter on identification and determination of reduced glutathione by cathodic stripping voltammetry

The effects of pH, metal ions (i.e. Cu²⁺, Cd²⁺, Pb²⁺ and Zn²⁺) and natural organic matter (i.e. Suwannee River natural organic matter standard [SRNOM]) on determination of thiol (i.e. reduced glutathione [GSH]) by cathodic stripping voltammetry were evaluated. pH was the most critical parameter to influence GSH voltammogram (i.e. peak shape, position and height). In presence of Cu and Cd, secondary peaks were found at [metal]/GSH > 1 due to formation of GSH complexes at pH = 8.0 (Cu and Cd) and 2.5 (Cu only). On the other hand, Pb showed negligible influence on GSH voltammogram at pH 8.0 and 2.5 within [Pb]/[GSH] = 0.01–2.0. Zn significantly reduced GSH peak height at pH 2.5 at [Zn]/[GSH] = 0.01–2.0. SRNOM peak significantly overlapped with GSH peak at pH 8.0 and [SRNOM] > 1 mg L^?1 but was clearly separated from the GSH peak at pH 2.5. However, at pH 2.5, the presence of metal ions and/or SRNOM significantly underestimated GSH concentration (recovery = 21–69%), likely due to metal complexation with GSH and/or SRNOM adsorption onto Hg electrode. The effects of metal ions were minimised by the addition of EDTA. The interference induced by SRNOM adsorption was reduced as the [SRNOM] was reduced to 1 mg L^?1 and the recovery was improved to 98%.