Preconcentration of inorganic antimony(III) in environmental samples by PSTH-Dowex microcolumn and determination by FI-ETAAS

A flow injection on-line sorption preconcentration system has been synchronously coupled to an electrothermal atomic absorption spectrometry (ETAAS) system for the selective determination of trace amounts of Sb(III) in water, soil and plant. The determination was achieved by selective complexation and sorption of Sb(III) with [1,5-bis(2-pyridyl)-3-sulphophenyl methylene thiocarbonohydarzide (PSTH) immobilized on an anion-exchange resin (Dowex 1× 8-200)] at a wide range of pH, quantitative elution with 50 μl of 2 M HNO₃ and subsequent ETAAS detection. ETAAS determination of the analyte was performed in parallel with the preconcentration of the next sample. Using a preconcentration time of 60 s and a sample loading flow rate of 2.8 ml min⁻¹, an enhancement factor of 12 was obtained in comparison with direct injection of 50 μl aqueous solution, resulting in a sampling frequency of 31 samples h⁻¹. The detection limit (3 s) was 2 μg l⁻¹ and the precision was 3.1% (R.S.D.) for 11 replicate determinations at 10 μg l⁻¹. The accuracy of the proposed method was demonstrated by analyzing one certified sample and different spiked samples.     

Sulphoxine immobilized onto chitosan microspheres by spray drying: application for metal ions preconcentration by flow injection analysis

A new chelating resin based on chitosan biopolymer modified with 5-sulphonic acid 8-hydroxyquinoline using the spray drying technique for immobilization is proposed. The chelating resin was characterized by thermogravimetric analysis (TGA) and X-ray diffraction (XRD) and surface area by nitrogen sorption. The efficiency of the chelating resin was evaluated by the preconcentration of metal ions Cu(II) and Cd(II) present in aqueous samples in trace amounts. The metal ions were previously enriched in a minicolumn and the concentrations of the analytes were determined on-line by flame atomic absorption spectrometry (FAAS). The maximum retention for Cu(II) occurred in the pH range 8-10, and for Cd(II) at pH 7. The optimum flow rate for sorption was found to be 7.2 ml min⁻¹ for the preconcentration of the metal ions. The analytes gave relative standard deviations (R.S.D.) of 0.7 and 0.6% for solutions containing 20 μg l⁻¹ of Cu(II) and 15 μg l⁻¹ of Cd (II), respectively (n=7). The enrichment factors for Cu(II) and Cd (II) were 19.1 and 13.9, respectively, and the limits of detection (LOD) were 0.2 μg l⁻¹ for Cd(II) and 0.3 μg l⁻¹ for Cu(II), using a preconcentration time of 90 s (n=11). The accuracy of the proposed method was evaluated by the metal ion recovery technique, in the analysis of potable water and water from a lake, with recoveries being between 97.2 and 107.3%.     

Synthesis and application of a functionalized resin for flow injection/F AAS copper determination in waters

This paper reports the development of a new strategy for low-level determination of copper in water samples by using a flow-injection system coupled to solid-phase extraction (SPE) using flame atomic absorption spectrometry (F AAS) as detector. In order to preconcentrate copper from samples, a minicolumn packed with a styrene-divinylbenzene resin functionalized with (S)-2-[hydroxy-bis-(4-vinyl-phenyl)-methyl]-pyrrolidine-1-carboxylic acid ethyl ester was used and the synthesis procedure is described. System operation is based on the on-line retention of Cu(II) ions at pH 9.0 ± 0.2 in a such minicolumn with posterior analyte elution with 2 mol l⁻¹ HCl directly to the F AAS nebulizer. The influence of several chemical (sample pH, buffer concentration, HCl eluent concentration and effect of the ionic strength) and flow (sample and eluent flow rates and preconcentration time) variables that could affect the performance of this system were investigated as well as the possible interferents. At optimized conditions, for 2 min of preconcentration time (13.2 ml of sample volume), the system achieved a detection limit of 1.1 μg l⁻¹, a R.S.D. 1% at 20 μg g l⁻¹ and an analytical throughput of 25 h⁻¹, whereas for 4 min of preconcentration time (26.4 ml of sample volume), a detection limit of 0.93 μg l⁻¹, a R.S.D. 5.3% at 5 μg l⁻¹ and a sampling frequency of 13 h⁻¹ were reported.     

Bioaccumulation of antimony, arsenic, and mercury in the vicinities of a large antimony mine, China

To study the characteristics of antimony (Sb) bioaccumulation under high Sb background values, aquatic, amphibious and terrestrial biological samples were collected in the vicinity of the Xikuangshan (XKS) Sb mine area in China. Hydride generation-atomic fluorescence (HG-AFS) analysis showed that Sb concentrations in terrestrial invertebrates (average 30,400 μg kg^− 1 dry wt.) were higher than those in aquatic (average 5200 μg kg^− 1 dry wt.) and amphibian (average 2300 μg kg^− 1 dry wt.) biological samples. Within 1 km distance of the XKS Sb mine area, grasshoppers (Acrida chinensis) and earthworms (Pheretima aspergillum) had the highest Sb amounts of 17,300 ±3200 and 43,600 ± 47,700 μg kg^− 1 dry wt., respectively. No Sb biomagnifications were observed. The bioavailability of Sb was found to be lower than those of As and Hg. A preliminary conclusion is that antagonistic effects exist between Sb and Hg accumulation in biological samples from aquatic environments. Our study is the first to report such antagonistic effects between Sb and Hg. If this deduction proves to be correct, it should be taken into consideration in assessing human health risks, especially when Sb and Hg concentrations in the aquatic environments are high.     

Antimony determination and speciation by multisyringe flow injection analysis with hydride generation-atomic fluorescence detection

A new analytical procedure for determination of inorganic antimony and speciation of antimony(III) and antimony(V) is presented. For this purpose, a software-controlled time-based multisyringe flow injection system, which contains a multisyringe burette provided with a multi-port selection valve, was developed. Hydride generation-atomic fluorescence spectrometry was used as a detection technique. A 0.3% (w/v) reducing sodium tetrahydroborate solution, hydrochloric acid (2 M), an antimony solution and a pre-reducing solution of 10% (w/v) KI and 0.3% (w/v) ascorbic acid are dispensed simultaneously into a gas-liquid separation cell with further propulsion of the reaction product into the flame of an atomic fluorescence spectrometer using argon flow. A hydrogen flow was employed to support the flame.The linear range and the detection limit (3s_b/S) of the proposed technique were 0.2-5.6 μg l⁻¹ and 0.08 μg l⁻¹, respectively. A sample throughput of 18 samples per hour (corresponding to 80 injections per hour) was achieved. The relative standard deviation for 18 independent measurements was 4.6%. This technique was validated by means of reference solid and water materials with good agreement with the certified values. Satisfactory results for speciation of Sb(III) and Sb(V) by means of the developed technique were obtained.     

Liquid chromatography-hydride generation-atomic fluorescence spectrometry hybridation for antimony speciation in environmental samples

Atomic fluorescence spectrometry was used as an element-specific detector in hybridation with liquid chromatography (LC) and hydride generation for the speciation of Sb(III), Sb(V) and trimethylantimony dichloride (TMSbCl₂). The three species were poorly resolved in a single chromatogram but good results were obtained by anion-exchange chromatography, using a mobile phase with 20 mM EDTA and 8 mM hydrogenphthalate to separate Sb(III) and Sb(V) and 1 mM carbonate at pH 10 to separate Sb(V) and TMSbCl₂. Calibration graphs were linear between 2 and 100 μg l⁻¹. Detection limits were 0.9, 0.5 and 0.7 μg l⁻¹ for Sb(III), Sb(V) and TMSbCl₂, respectively. The method was applied to the speciation of antimony in environmental samples.     

Evaluation of on-line preconcentration and flow-injection amperometry for phosphate determination in fresh and marine waters

Dissolved reactive phosphorus (DRP) was determined as orthophosphate (PO₄-P) in fresh and saline water samples by flow-injection (FI) amperometry, without and with in-valve column preconcentration. Detection is based on reduction of the product formed from the reaction of DRP with acidic molybdate at a glassy carbon working electrode (GCE) at 220 mV versus the Ag/AgCl reference electrode. A 0.1 M potassium chloride solution was used as both supporting electrolyte and eluent in the preconcentration system. For the FI configuration without preconcentration, a detection limit of 3.4 μg P l⁻¹ and sample throughput of 70 samples h⁻¹ were achieved. The relative standard deviations for 50 and 500 μg P l⁻¹ orthophosphate standards were 5.2 and 5.9%, respectively. By incorporating an ion exchange preconcentration column, a detection limit of 0.18 μg P l⁻¹ was obtained for a 2-min preconcentration time (R.S.D.s for 0.1 and 1 μg P l⁻¹ standards were 22 and 1.0%, respectively). Potential interference from silicate, sulfide, organic phosphates and sodium chloride were investigated. Both the systems were applied to the analysis of certified reference materials and water samples.     

Measurement of methyl mercury (I) and mercury (II) in fish tissues and sediments by HPLC-ICPMS and HPLC-HGAAS

A procedure for the extraction and determination of methyl mercury and mercury (II) in fish muscle tissues and sediment samples is presented. The procedure involves extraction with 5% (v/v) 2-mercaptoethanol, separation and determination of mercury species by HPLC-ICPMS using a Perkin-Elmer 3 μm C8 (33 mm × 3 mm) column and a mobile phase 3 containing 0.5% (v/v) 2-mercaptoethanol and 5% (v/v) CH₃OH (pH 5.5) at a flow rate 1.5 ml min⁻¹ and a temperature of 25 °C. Calibration curves for methyl mercury (I) and mercury (II) standards were linear in the range of 0-100 μg l⁻¹ (r² = 0.9990 and r² = 0.9995 respectively). The lowest measurable mercury was 0.4 μg l⁻¹ which corresponds to 0.01 μg g⁻¹ in fish tissues and sediments. Methyl mercury concentrations measured in biological certified reference materials, NRCC DORM - 2 Dogfish muscle (4.4 ± 0.8 μg g⁻¹), NRCC Dolt - 3 Dogfish liver (1.55 ± 0.09 μg g⁻¹), NIST RM 50 Albacore Tuna (0.89 ± 0.08 μg g⁻¹) and IRMM IMEP-20 Tuna fish (3.6 ± 0.6 μg g⁻¹) were in agreement with the certified value (4.47 ± 0.32 μg g⁻¹, 1.59 ± 0.12 μg g⁻¹, 0.87 ± 0.03 μg g⁻¹, 4.24 ± 0.27 μg g⁻¹ respectively). For the sediment reference material ERM CC 580, a methyl mercury concentration of 0.070 ± 0.002 μg g⁻¹ was measured which corresponds to an extraction efficiency of 92 ± 3% of certified values (0.076 ± 0.04 μg g⁻¹) but within the range of published values (0.040-0.084 μg g⁻¹; mean ± s.d.: 0.073 ± 0.05 μg g⁻¹, n = 40) for this material. The extraction procedure for the fish tissues was also compared against an enzymatic extraction using Protease type XIV that has been previously published and similar results were obtained. The use of HPLC-HGAAS with a Phenomenox 5 μm Luna C18 (250 mm × 4.6 mm) column and a mobile phase containing 0.06 mol l⁻¹ ammonium acetate (Merck Pty Limited, Australia) in 5% (v/v) methanol and 0.1% (w/v) l-cysteine at 25 °C was evaluated as a complementary alternative to HPLC-ICPMS for the measurement of mercury species in fish tissues. The lowest measurable mercury concentration was 2 μg l⁻¹ and this corresponds to 0.1 μg g⁻¹ in fish tissues. Analysis of enzymatic extracts analysed by HPLC-HGAAS and HPLC-ICPMS gave equivalent results.     

Simultaneous determination of trace arsenic(III), antimony(III), total arsenic and antimony in Chinese medicinal herbs by hydride generation-double channel atomic fluorescence spectrometry

A new method was developed for simultaneous determination of trace arsenic and antimony in Chinese herbal medicines by hydride generation-double channel atomic fluorescence spectrometry with a Soxhlet extraction system and an n-octanol-water extraction system, respectively. The effects of analytical conditions on the fluorescence intensity were investigated and optimized. A water-dissolving and methanol-water-dissolving capability were compared. The contents of different species in five Chinese herbal medicines and their decoctions were analyzed. The concentration ratios of n-octanol-soluble As or Sb to water-soluble As or Sb were related to the kinds of medicine and the acidity of the decoction. Soxhlet extraction was found to be an effective method for plants pretreatment for determination of arsenic and antimony species in Chinese herbs; the interferences of coexisting ions were evaluated. The proposed method has the advantages of simple operation, high sensitivity and high speed, with 3σ detection limits of 0.094 μg g⁻¹ for As(III), 0.056 μg g⁻¹ for total As, 0.063 μg g⁻¹ for Sb(III) and 0.019 μg g⁻¹ for total Sb in a 1.0 g of the sample.     

A permeation liquid membrane system for determination of nickel in seawater

The use of a permeation liquid membrane system for the preconcentration and separation of nickel in natural and sea waters and subsequent determination by atomic absorption spectroscopy is presented. 2-Hydroxybenzaldehyde N-ethylthiosemi-carbazone (2-HBET) in toluene is used as the active component of the liquid membrane. A study strategy based on a simplex design has been followed. Several chemical and physical parameters were optimized. Maximum permeation coefficient was obtained at a feed solution pH of 9.4, 0.3 mol l⁻¹ of HNO₃ in the stripping solution and 1.66 mmol l⁻¹ of 2-HBTE in toluene as carrier. The precision of the method was 4.7% at 95% significance level and a detection limit of 0.012 μg l⁻¹ of nickel was achieved. The preconcentration procedure showed a linear response within the studied concentration range from 3 to 500 μg l⁻¹ of Ni in the feed solution. The method was validated with different spiked synthetic seawater and certified reference water samples: TMDA-62 and LGC 6016, without matrix interferences and showing good concordance with the certified values, being the relative errors −5.9% and −2.2%, respectively. Under optimal conditions, the average preconcentration yield for real seawater samples was 98 ± 5%, with a nickel preconcentration factor of 20.83 and metal concentrations ranging between 2.8 and 5.4 μg l⁻¹.     

Speciation analysis of antimony in marine biota by HPLC-(UV)-HG-AFS: Extraction procedures and stability of antimony species

Speciation analysis of antimony in marine biota is not well documented, and no specific extraction procedure of antimony species from algae and mollusk samples can be found in the literature. This work presents a suitable methodology for the speciation of antimony in marine biota (algae and mollusk samples). The extraction efficiency of total antimony and the stability of Sb(III), Sb(V) and trimethylantimony(V) in different extraction media (water at 25 and 90 °C, methanol, EDTA and citric acid) were evaluated by analyzing the algae Macrosystis integrifolia (0.55 ± 0.04 μg Sb g⁻¹) and the mollusk Mytilus edulis (0.23 ± 0.01 μg Sb g⁻¹). The speciation analysis was performed by anion exchange liquid chromatography (post-column photo-oxidation) and hydride generation atomic fluorescence spectrometry as detection system (HPLC-(UV)-HG-AFS). Results demonstrated that, based on the extraction yield and the stability, EDTA proved to be the best extracting solution for the speciation analysis of antimony in these matrices. The selected procedure was applied to antimony speciation in different algae samples collected from the Chilean coast. Only the inorganic Sb(V) and Sb(III) species were detected in the extracts. In all analyzed algae the sum of total antimony extracted (determined in the extracts after digestion) and the antimony present in the residue was in good agreement with the total antimony concentration determined by HG-AFS. However, in some extracts the sum of antimony species detected was lower than the total extracted, revealing the presence of unknown antimony species, possibly retained on the column or not detected by HPLC-(UV)-HG-AFS. Further work must be carried out to elucidate the identity of these unknown species of antimony.     

Determination of traces of palladium in stream sediment and auto catalyst by FI-ICP-OES using on-line separation and preconcentration with QuadraSil TA

A flow injection analysis (FIA) method using on-line separation and preconcentration with a novel metal scavenger beads, QuadraSil™ TA, has been developed for the ICP-OES determination of traces of palladium. QuadraSil TA contains diethylenetriamine as a functional group on spherical silica beads and shows the highest selectivity for Pd(II) at pH 1 (0.1 mol l⁻¹ hydrochloric acid) solution. An aliquot of the sample solution prepared as 0.1 mol l⁻¹ in hydrochloric acid was passed through the QuadraSil TA column. After washing the column with the carrier solution, the Pd(II) retained on the column was eluted with 0.05 mol l⁻¹ thiourea solution and the eluate was directly introduced into an ICP-OES. The proposed method was successfully applied to the determination of traces of palladium in JSd-2 stream sediment certified reference material [0.019 ± 0.001 μg g⁻¹ (n = 3); provisional value: 0.0212 μg g⁻¹] and SRM 2556 used auto catalyst certified reference material [315 ± 4 μg g⁻¹ (n = 4); certified value: 326 μg g⁻¹]. The detection limit (3σ) of 0.28 ng ml⁻¹ was obtained for 5 ml of sample solution. The sample throughputs for 5 ml and 100 μl of the sample solutions were 10 and 15 h⁻¹, respectively.     

Speciation of dissolved inorganic antimony in natural waters using liquid phase semi-microextraction combined with electrothermal atomic absorption spectrometry

Liquid-liquid extraction preconcentration technique which allows the achievement of extremely high ratio between the aqueous and organic phase was specified as semi-microextraction. A modified highly effective liquid phase semi-microextraction (LSME) procedure was developed for preconcentration and determination of ultra trace levels of inorganic antimony species in environmental waters using electrothermal atomic absorption spectrometry (ETAAS) for quantification. Antimony(III) species were selectively extracted as dithiocarbamate complexes from 100 mL aqueous phase into 250 μL xylene at pH range of 5-8. Total Sb was determined using the same extraction system over a sample acidity range of pH 0-1.2 without the need for pre-reduction of Sb(V) to Sb(III). The concentration of Sb(V) was obtained as the difference between that of total antimony and Sb(III). With an 8 min extraction an enrichment factor of 400 was achieved. The limit of detection (3 s) was 2 ng L⁻¹ Sb. The method was not affected by the presence of up to 0.01% humic acid, 0.025 mol L⁻¹ EDTA, 0.01 mol L⁻¹ tartaric acid and 0.001 mol L⁻¹ F⁻. Recoveries of spiked Sb(III) and Sb(V) in river, tap, and sea water samples ranged from 93 to 108%. The results for total antimony concentration in the river water reference material SLRS-5 were in good agreement with the information value. The procedure was applied to the determination and quantification of dissolved antimony species in natural waters.     

Optimization and comparison of chemical and electrochemical hydride generation for optical emission spectrometric determination of arsenic and antimony using a novel miniaturized microwave induced argon plasma exiting the microstrip wafer

Continuous flow (CF) chemical hydride generation (CHG) and electrochemical hydride generation (ECHG) directly coupled to a novel 40 W, atmospheric pressure, 2.45 GHz microwave microstrip Ar plasma exiting a microstrip wafer has been developed for the emission spectrometric determination of As and Sb using a miniaturized optical fiber spectrometer and a CCD-array detector. The experimental conditions for both procedures were optimized with respect to the relative net intensities of the As I 228.8 nm and Sb I 252.8 nm lines and their signal-to-background intensity ratios. Additionally, the susceptibility to interferences from Cd, Co, Cr, Cu, Fe, Ni, Pb and Zn and other hydride-forming elements in the determination of As and Sb using the CHG and ECHG techniques was investigated in detail. Under the optimized conditions, it was found that ECHG is more prone to interferences compared to CHG. The detection limits (3σ) of As (6 ng mL⁻¹) and Sb (7 ng mL⁻¹) obtained for the ECHG-MSP-OES method are about three times lower than in the case of the CHG-MSP-OES method due to a two-fold lower amount of H₂ introduced into the MSP in case of the ECHG, resulting in a better plasma stability and reduced background level. The linearity ranges for both calibration curves to a concentration of up to 5 μg mL⁻¹ and a precision between 2% and 7% (2 μg mL⁻¹ and 0.050 μg mL⁻¹ of As and Sb, respectively) were found for both methods. The developed ECHG-MSP-OES method was validated for As through the analysis of a certified coal fly ash standard reference material (NIST SRM 1633a) after sample dissolution. The derived concentration (140 ± 8 μg g⁻¹) was found to agree well with the certified data (145 ± 15 μg g⁻¹). The method was also successfully applied to the analysis of both a galvanic bath sample, which contained Sb and was spiked with As, and a tap water sample spiked with both analytes. Recovery rates of 99-101% and a Sb concentration of 6.6 μg mL⁻¹ in the galvanic bath sample were revealed. The latter value showed a good agreement with the data obtained from ICP-OES analysis, which was also used for validation purpose.     

Amberlite XAD-2 functionalized with 2-aminothiophenol as a new sorbent for on-line preconcentration of cadmium and copper

A new functionalized resin has been applied in an on-line preconcentration system for copper and cadmium determination. Amberlite XAD-2 was functionalized by coupling it to 2-aminothiophenol (AT-XAD) by means of an NN spacer. This resin was packed in a minicolumn and used as sorbent in the on-line system. Metal ions were sorbed in the minicolumn, from which it could be eluted directly to the nebulizer-burner system of the flame atomic absorption spectrometer (FAAS). Elution of Cd(II) and Cu(II) from minicolumn can be made with 0.50 mol l⁻¹ HCl or HNO₃. The enrichment factors obtained were 28 (Cd) and 14 (Cu), for 60 s preconcentration time, and 74 (Cd) and 35 (Cu), if used 180 s preconcentration time. The proposed procedure allowed the determination of cadmium and copper with detection limits of 0.14 and 0.54 μg l⁻¹, respectively, when used preconcentration periods of 180 s. The effects of foreign ions on the adsorption of these metal ions are reported. The validation of the procedure was carried out by analysis of certified reference material. This procedure was applied to cadmium and copper determination in natural, drink and tap water samples.     

Electrochemical studies and square wave stripping voltammetry of five common pesticides on poly 3,4-ethylenedioxythiophene modified wall-jet electrode

The cyclic voltammetric behavior of five common pesticides such as dicofol (DCF), cypermethrin (CYP), monocrotophos (MCP), chlorpyrifos (CPF) and phosalone (PAS) was investigated at a poly 3,4-ethylenedioxythiophene modified glassy carbon electrode (PEDOT/GCE). A method was developed for the detection and determination of these pesticides in trace level flowing stream, based on their redox behavior. The square wave stripping voltammetric principle was used to analyze the selected pesticides on PEDOT/GCE. Varying the accumulation potential and accumulation time, the best accumulation conditions were found out. Effects of initial scan potential, square wave pulse amplitude, step potential and frequency were examined for the optimization of stripping conditions. The peak current responses of analyte under optimum conditions were correlated over flow rate by using wall-jet PEDOT/GCE assembly. The calibration plots were linear over the pesticide's concentration range 0.10-72.60 μg l⁻¹ for DCF, 0.41-198.24 μg l⁻¹ for CYP, 0.22-220.95 μg l⁻¹ for MCP, 0.35-259.69 μg l⁻¹ for CPF and 1.07-141.46 μg l⁻¹ for PAS. The limit of detection was obtained between <0.09 and <1.0 μg l⁻¹ for five pesticides. It is low enough for trace pesticide determination in real samples. This method is applied for the determination of the five pesticides in soil samples. The recovery values obtained in spiked soil samples are 95.4 ± 5.4% for DCF, 93.7 ± 4.2% for CYP, 85.3 ± 8.4% for MCP, 94.6 ± 6.6% for CPF and 93.5 ± 4.9% for PAS.     

A new functionalized resin and its application in preconcentration system with multivariate optimization for nickel determination in food samples

In this work, Amberlite XAD-2 resin functionalized with 4,5-dihydroxy-1,3-benzenedisulfonic acid was synthesized, characterized and applied as a new packing material for an on-line system to nickel preconcentration. The method is based on the sorption of Ni(II) ions in a minicolumn containing the synthesized resin, posterior desorption using an acid solution and measurement of the nickel by spectrophotometry (PAR method). The optimization of the system was performed using factorial design and Doehlert matrix considering five variables: eluent concentration, PAR solution pH, sample flow rate, PAR solution concentration and sample pH. Signals were measured as peak height by using an instrument software. Using the experimental conditions defined in the optimization, the method allowed nickel determination with achieved sampling rate of 25 samples per hour, detection limit (3 s) of 2 μg l⁻¹ and precision (assessed as the relative standard deviation) of 8.2-2.6%, for nickel solutions of 10.0-200.0 μg l⁻¹ concentration, respectively. The experimental enrichment factor of the proposed system was 46, for 120 s preconcentration time. The proposed procedure was applied for nickel determination in food samples. Recoveries of spike additions (5 or 10 μg g⁻¹) to food samples were quantitative (94-110%).     

On-line enrichment system for manganese determination in water samples using FAAS

An on-line preconcentration procedure for the determination of manganese using flow-injection approach with flame atomic absorption spectrometry as a detection method is described. The proposed method is based on the complexation between Mn(II) and 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (TCPP). Two approaches were investigated for enrichment of manganese; the formation of Mn-TCPP complex in a solution followed by its retention on a sorbent and the sorption of manganese ions onto the TCPP-modified resin. The best results was obtained for the first approach when 10⁻⁵ M reagent was on-line mixed with an aqueous sample solution and passed through the microcolumn packed with anion-exchange resin Amberlite IRA-904 for 5 min. The sorbed complexes were then eluted with 0.5 ml of 2 M HNO₃. A good precision (2.2-3.1% R.S.D. for 50 μg l⁻¹ manganese) and the enrichment factor of 30 were obtained with the detection limit of 12 μg l⁻¹ for 5 min loading time. The interference of anions and cations has been studied to optimize the conditions and the method was applied for determination of manganese in natural water samples. The results obtained by FI-FAAS and ETAAS (as a reference method) were not statistically different for a significance level of 0.05.     

Synthesis of cross-linked chitosan possessing N-methyl-d-glucamine moiety (CCTS-NMDG) for adsorption/concentration of boron in water samples and its accurate measurement by ICP-MS and ICP-AES

A chitosan resin derivatized with N-methyl-d-glucamine (CCTS-NMDG) was synthesized by using a cross-linked chitosan (CCTS) as base material. The N-methyl-d-glucamine (NMDG) moiety was attached to the amino group of CCTS through the arm of chloromethyloxirane. The adsorption behavior of 59 elements on the synthesized resin was systematically examined by using the resin packed in a mini-column, passing water samples through it and measuring the adsorbed elements in eluates by ICP-MS. The CCTS-NMDG resin shows high ability in boron sorption with the capacity of 0.61 mmol ml⁻¹ (= 2.1 mmol g⁻¹). The sorption kinetics of this resin was faster than that of the commercially available resins. Other advantages of the synthesized resin are: (1) quantitative collection of boron at neutral pH regions; (2) complete removal of large amounts of matrices; (3) no loss of efficiency over prolonged usage; (4) effective collection of boron in wide range concentration using a mini column containing 1 ml resin; (5) complete elution of boron with 1 mol l⁻¹ nitric acid. The resin was applied to the collection/concentration of boron in water samples. Boron in tap water and river water was found to be in the range of 6-8 μg l⁻¹. The limit of detection (LOD) of boron after pretreatment with CCTS-NMDG resin and measurement by ICP-MS was 0.07 μg l⁻¹ and the limit of quantification (LOQ) was 0.14 μg l⁻¹ when the volume of each sample and eluent was 10 ml.     

Monitoring inorganic mercury and methylmercury species with liquid chromatography-piezoelectric detection

A piezoelectric detection system coupled with a liquid chromatographic system is developed for the speciation of inorganic mercury(II) and methylmercury. Piezoelectric detection has been demonstrated to be a very sensitive detection system for total mercury determination when a gold-coated piezoelectric quartz crystal was used. The analytical features of this detection unit make it very suitable to be used as a detector coupled with a liquid chromatographic system for monitoring mercury species. After separation by a chromatography column (Spherisorb ODS-2, 5 μm,  mm i.d.), mercury species are liberated and reduced, by using stannous chloride, and are detected as an amalgam on the gold-coated piezoelectric quartz crystal, the sensor subsequently was regenerated by passing a peroxydisulfate solution. This detector exhibits good sensitivity, it allows the determination of mercury at sub-ppb concentration levels (0.30-1.20 μg l⁻¹). The precision, expressed as relative standard deviation, was ±2.7% (n=11) for a 0.5 μg l⁻¹ total mercury concentration. The proposed method is free of interferences and it allowed the determination of inorganic mercury and methylmercury species in natural waters.