Determination of mercury in air by neutron activation analysis

A sensitive method for the determination of mercury in sea and surface waters is presented. A distinction is made between inorganic, organic and particulate mercury. In the determination of inorganic mercury, the element is isolated by reduction and volatilization, followed by absorption on a charcoal column. The total mercury content of the water with and without suspended solids is determined by absorption from the solution onto a column of charcoal. In all cases, the mercury on the absorber is determined by thermal neutron activation analysis. The limit of detection is l ng 1^-1.     

Study on the Catalytic Determination of Vanadium (V) Using the Rhodamine 6G-Periodate Redox Reaction and its Analytical Application

 A fluorescence quenching method for the determination of vanadium (V) based on the vanadium- catalyzed oxidation of rhodamine 6G (R6G) with periodate in the presence of ethylenediaminetetraacetic acid disodium salt (EDTA) in sulfuric acid medium is described. The fluorescence was measured with excitation and emission wavelengths of 525 and 555 nm, respectively. The calibration graph for vanadium (V) had linear ranges of 3.0 × 10⁻⁹–1.5 × 10⁻⁸ mol/l and 1.5 × 10⁻⁸–4.0 × 10⁻⁸ mol/l, respectively. The detection limit was 1.7 × 10⁻⁹ mol/l. The proposed method was successfully applied to the determination of vanadium (V) in river water, rain water and cast iron samples. Received June 29, 2001 Revision October 9, 2001     

Catalytic Determination of Vanadium Based on the Bromate Oxidative-C oupling Reaction of Metol with Phloroglucinol

 A selective, sensitive and simple catalytic method is developed for the determination of vanadium in natural and highly polluted waste waters. The method is based on the catalytic effect of V^V and/or V^IV on the bromate oxidative-coupling reaction of metol with phloroglucinol (PG). The reaction is followed spectrophotometrically by tracing the oxidation product at 464 nm after 10 minutes of mixing the reagents. The optimum reaction conditions are metol (8.0×10⁻³ M), PG (4.0×10⁻³ M) and bromate (2×10⁻² M) at 35°C and in presence of an activator-b uffer mixture of 5×10⁻² M of each of citric and monochloroacetic acids (pH 2.40). Following the recommended procedure, vanadium can be determined with a linear calibration graph up to 8.0 ng mL⁻¹ and a detection limit, based on the 3s_b criterion, of 0.1 ng mL⁻¹. Spectrophotometric determination of as little as 1.0 ng mL⁻¹ of V^V or V^IV in aqueous solutions gave an average recovery of 98% with relative standard deviations of ?1.8% (n = 5). The proposed method was directly applied to the determination of vanadium in Nile river water and highly polluted industrial wastes. Statistical treatments of analytical results could not detect any systematic error and showed the high accuracy and precision of the developed method. Received November 25, 1999. Revision March 10, 2000.     

Use of Imidazole 4,5-Dicarboxylic Acid Resin in Vanadium Speciation

 A new resin has been synthesized by functionalisation of polystyrene-divinylbenzene (8%) with imidazole 4,5-dicarboxylic acid through –N=N– bonding. The resulting resin has been characterised by elemental analysis, thermogravimetric analysis, infrared spectroscopy, hydrogen ion capacity and metal ion capacity. The speciation study of vanadium has been studied by using this resin and the maximum exchange capacity was found to be 0.45 mmol g⁻¹ for V⁴⁺ and that for V⁵⁺ was 1.57 mmol g⁻¹ at pH 3 for both. The eluents malonic acid and sodium hydroxide have been used for the selective separation of vanadium(IV) and vanadium(V) species respectively. The effects of diverse ions on the sorption and recovery of each species have been studied. Finally, the developed method has been applied for the speciation and determination of these two species in natural water samples. Correspondence: Department of Chemistry, The University of Burdwan, Burdwan, India. e-mail: akdas100@yahoo.com Received December 20, 2001; accepted October 11, 2002     

Flow injection spectrofluorimetric determination of iron(III) in water using salicylic acid

A simple and fast flow injection fluorescence quenching method for the determination of iron in water has been developed. Fluorimetric determination is based on the measurement of the quenching effect of iron on salicylic acid fluorescence. An emission peak of salicylic acid in aqueous solution occurs at 409 nm with excitation at 299 nm. The carrier solution used was 2 × 10⁻⁶ mol L⁻¹ salicylic acid in 0.1 mol L⁻¹ NH₄⁺/NH₃ buffer solution at pH 8.5. Linear calibration was obtained for 5–100 μg L⁻¹ iron(III) and the relative standard deviation was 1.25 % (n = 5) for a 20 μL injection volume iron(III). The limit of detection was 0.3 μg L⁻¹ and the sampling rate was 60 h⁻¹. The effect of interferences from various metals and anions commonly present in water was also studied. The method was successfully applied to the determination of low levels of iron in real samples (river, sea, and spring waters).     

Extraction-spectrophotometric study on the vanadium(V)-2,3-dihydroxynaphthalene — iodonitrotetrazolium chloride — water — chloroform system and its analytical application

The formation of a new ternary ion-associate complex of vanadium(V) with 2,3-dihydroxynaphthalene and iodonitrotetrazolium chloride with a composition ratio of 1:2:1 is reported. The complex is quantitatively extracted from water into chloroform. The molar absorptivity (ɛ) of the extract at λ _max=340 nm is 2.5 × 10⁴ dm³/mol cm, and Beer’s law is obeyed for concentrations ranging from 0.1 to 0.9 μg/cm³ V(V). The following constants are determined: the extraction constant, the association constant, the distribution constant, and the recovery factor. The effects of foreign ions and reagents are studied. A selective and sensitive method is developed for determination of vanadium in steels.     

Using bamboo charcoal as solid-phase extraction adsorbent for the ultratrace-level determination of perfluorooctanoic acid in water samples by high-performance liquid chromatography–mass spectrometry

In recent years, bamboo charcoal, a new kind of material with special microporous and biological characteristics, has attracted great attention in many application fields. In this paper, the potential of bamboo charcoal to act as a solid-phase extraction (SPE) adsorbent for the enrichment of the environmental pollutant perfluorooctanoic acid, which is one of the newest types of persistent organic pollutants in the environment, has been investigated. Important factors that may influence the enrichment efficiency—such as the eluent and its volume, the flow rate of the sample, the pH of the sample and the sample volume—were investigated and optimized in detail. Under the optimum conditions, the limit of detection for PFOA was 0.2 ng L⁻¹. The experimental results indicated that this approach gives good linearity (R ² = 0.9995) over the range 1–1000 ng L⁻¹ and good reproducibility, with a relative standard deviation of 4.0% (n = 5). The proposed method has been applied to the analysis of real water samples, and satisfactory results were obtained. The average spiked recoveries were in the range 79.5∼118.3 %. All of the results indicate that the proposed method could be used for the determination of PFOA at ultratrace levels in water samples.     

Flow-injection spectrophotometry of vanadium by catalysis of the bromate oxidation of N,N'-bis(2-hydroxyl-3-sulfopropyl)-tolidine

A highly sensitive flow-injection method is proposed for the catalytic determination of vanadium(V) at sub-nanogram per milliliter levels using a new indicator reaction. The method is based on the catalytic effect of vanadium(V) on the bromate oxidation of N,N′-bis(2-hydroxyl-3-sulfopropyl)-tolidine. 1,2-Dihydroxybenzene-3,5-disulfonate was used as an activator in the vanadium(V)-catalyzed reaction and significantly enhanced the sensitivity of the method. Vanadium(V) in the range 0.01-3.0 ng ml⁻¹ was easily determined with sampling rate of about 30 h⁻¹. Vanadium(IV) could be also determined. The limit of detection (S/N=3) was 0.008 ng ml⁻¹ and the relative standard deviations were 1.4 and 1.6% for ten determinations of 0.2 ng ml⁻¹ vanadium(IV) and vanadium(V), respectively. Interferences from metal ions could be suppressed by the addition of ethylenediamine-N,N,N′,N′-tetrakis(methylenephosphonic acid) as a masking agent. The proposed method was successfully applied to the determination of vanadium in water samples.     

Organic solvent-soluble membrane filters for the preconcentration and spectrophotometric determination of iron(II) traces in water with Ferrozine

An organic solvent-soluble membrane filter (MF) is proposed for the simple and rapid reconcentration with subsequent spectrophotometric determination of trace levels of iron (II) in water. Iron (II) is collected on a nitrocellulose membrane filter as ion associate of an anionic complex, which is formed by iron (II) and Ferrozine and a cation-surfactant. The ion-pair compound and the MF can be dissolved in small volumes of 2-ethoxyethanol and the absorbance of the resulting solution is measured at 560 nm against a reagent blank with molar absorptivity of 4.01 × 10⁴ L mol^–1 cm^–1. Beer’s law is obeyed over the concentration range 0–10 μg L^–1 of iron (II) in water and the detection limit is 0.03 μg L^–1 with a 50-fold enrichment factor. The proposed method can satisfactorily be applied to the determination of iron (II) in natural water and sea water. Received: 23 June 1998 / Revised: 21 July 1998 / Accepted: 25 August 1998     

Extraction-spectrophotometric determination of trace iron (II) in sea water with 2-[2-(3,5-dibromopyridyl)azo]-5-diethylaminobenzoic acid

An extraction-spectrophotometric method is described for the determination of traces of iron(II) with 2-[2-(3,5-dibromopyridyl)azo]-5-diethyl-aminobenzoic acid. The reagent forms a stable and blue 12 iron/reagent complex that can be extracted into chloroform. The apparent molar absorptivity of the iron(II) complex is 1.09 × 10⁵ 1 mol^–1 cm^–1 at 624 nm in chloroform. The reagent is relatively selective; interferences from cobalt, copper, nickel and vanadium can be removed by using dimethylglyoxime and EDTA. The method is applied to the determination of iron (II) in sea water and aluminium alloys with good precision and accuracy.     

Determination of vanadium content in soils by slurry sampling electrothermal atomic absorption spectrometry using KO300G as the stabilizing agent

A direct and sensitive method for the determination of vanadium concentrations in soil is developed using ultrasonic slurry sampling electrothermal atomic absorption spectrometry (USSSETAAS). The surfactant, KO300G, is used as the stabilizing agent. The precision and accuracy of the method are investigated. The detection limits are 0.6 and 0.7 μg 1⁻¹ for SRM Montana Soil 2711 and SRM Soil — S, respectively. The method is applied to determine the vanadium content in 10 soil samples from the Wielkopolska region.     

Sensitive spectrophotometric determination of vanadium with hydrogen peroxide and 2-(5-chloro-2-pyridylazo)-5-dimethylaminophenol after extraction with N-benzoyl-N-phenylhydroxylamine

A selective and precise spectrophotometric determination of vanadium(V) is performed after preceding extraction with N-benzoyl-N-phenylhydroxylamine (BPHA). The color is developed in a water-ethanol solution with hydrogen peroxide and 2-(5-chloro-2-pyridylazo)-5-dimethylaminophenol (5-Cl-DMPAP). The molar absorptivity at 588 nm is (6.57 ± 0.05) × 10⁴ L mol^–1 cm^–1 at pH 2.1. The method permits the determination of vanadium (V) at trace levels in the presence of large amounts of other ions. It is applied to the determination of vanadium in aluminium (analytical reagent grade) and in human hair. High accuracy and precision is obtained. Received: 18 April 1997 / Revised: 20 June 1997 / Accepted: 25 June 1997     

Solid-phase extraction-liquid chromatography-fluorimetry for organotin speciation in natural waters

Summary A method is reported for the determination of dibutyltin (DBT), diphenyltin (DPhT), tributyltin (TBT), and triphenyltin (TPhT) species at the nanogram per litre concentration level in natural water samples. Analytes were isolated from samples by solid-phase extraction and analysed both off-line and on-line by reversed-phase high-performance liquid chromatography with post-column derivatization and fluorimetric detection. Several SPE cartridges and eluents were evaluated; C₁₈ enrichment and elution with a mixture of methanol, acetic acid, and water was found most suitable. Preconcentration factors up to 250 can be achieved when a 500-mL sample is processed. Detection limits, recovery rates, and the precision of the whole process have been determined. The method has been applied to the determination of organotin species in spiked natural water samples collected on the NW Mediterranean coast. Recovery rates range from 75 to 110% and detection limits are at the low ng L⁻¹ level (1–3 ng Sn L⁻¹ for DPhT, DBT, and PhT and 40 ng Sn L⁻¹ for TBT when 250 mL spiked sea water is processed.)     

Extraction-visible spectrophotometric method for determination of nitrate : Application to water analysis

An extraction-visible spectrophotometric method for determination of nitrate is described. The method is based on the extraction of nitrate with tetraphenylphosphonium chloride and the exchange of the nitrate in the colorless Ph₄P-NO₃ extract by intensely colored vanadium(V)-4-(2-pyridylazo)resorcinol complex. The color intensity of this extract is very stable and reproducible. Absorption maximum appears at 560 nm with molar absorptivity 3.6 · 10⁴ 1 mol⁻¹cm⁻¹. The application of the method to water analysis was investigated and the procedure for determination of nitrate in drinking water is developed.     

2-(5-Nitro-2-Pyridylazo)-5-(N-Propyl-N-Sulfopropylamino)Phenol as a new analytical reagent for flow-injection spectrophotometric determination of trace vanadium(V)

A flow injection method using 2-(5-nitro-2-pyridylazo)-5-(N-propyl-N-sulfopropylamino)phenol-(Nitro-PAPS) as a new chromogenic reagent is presented for sensitive and rapid determination of vanadium. Nitro-PAPS reacts with vanadium(V) in weakly acidic medium to form a water soluble complex of molar absorptivity of 8.0 × 10⁴L mol^–1 cm^–1 at 592 nm (maximum absorption wavelength), which permits the straightforward application of a flow injection system to the sensitive determination of vanadium. Under the optimum conditions established, a linear calibration graph was obtained in the range 1–120 ng mL^–1. The relative standard deviation for 60 ng mL^–1 vanadium was 2.2% (n = 5) and the limit of detection was 1 ng mL^–1. The sample throughput is about 40 h^–1. Most inorganic and organic anions examined did not interfere even at concentrations of 3000–6000 times of vanadium. Interference from cobalt(II), copper(II) and nickel(II) at 200ng mL^–1 levels can be overcome by the addition of N-(dithio-carboxy)sarcosine. The recoveries for each 20 and 10 ng mL^–1 vanadium added to the river water were 98 and 97%, respectively.The authors express their thanks to Miss Miho Suzuki and Miss Hiroyo Yamada for their experimental assistance in part.     

Rapid determination method of radiocesium in sea water by cesium-selective resin

A rapid and precise method of determining radiocesium corresponding to 5 mrem/y, the Japan AEC's guideline, was proposed. The development and practical performance of cesium-selective resin and the determination method was described in this paper. The resin was prepared by the formation of ammonium molybdophosphate in the structure of Amberlite XAD-7 resin. It took only 3 hours to carry out all the procedures the authors proposed. This value represents 1/10∼1/2 of the time of conventional method. The concentration of¹³⁷Cs and¹³⁴Cs in sea water was determined to be 0.13∼0.16 pCi/1 and less than 7.1·10⁻² pCi/1, respectively.     

Separation/preconcentration and determination of vanadium with dispersive liquid-liquid microextraction based on solidification of floating organic drop (DLLME-SFO) and electrothermal atomic absorption spectrometry

A novel dispersive liquid-liquid microextraction based on solidification of floating organic drop (DLLME-SFO) for separation/preconcentration of ultra trace amount of vanadium and its determination with the electrothermal atomic absorption spectrometry (ETAAS) was developed. The DLLME-SFO behavior of vanadium (V) using N-benzoyl-N-phenylhydroxylamine (BPHA) as complexing agent was systematically investigated. The factors influencing the complex formation and extraction by DLLME-SFO method were optimized. Under the optimized conditions: 100 μL, 200 μL and 25 mL of extraction solvent (1-undecanol), disperser solvent (acetone) and sample volume, respectively, an enrichment factor of 184, a detection limit (based on 3S_b/m) of 7 ng L⁻¹ and a relative standard deviation of 4.6% (at 500 ng L⁻¹) were obtained. The calibration graph using the preconcentration system for vanadium was linear from 20 to 1000 ng L⁻¹ with a correlation coefficient of 0.9996. The method was successfully applied for the determination of vanadium in water and parsley.     

Differential pulse polarographic determination of Co(II) using moxifloxacine

The polarographic reduction of Co(II) in the presence of moxifloxacin (1-cyclopropyl-7-[(S,S)-2.8-diazabicyclo[4.3.0]non-8-yl]-6-fluoro-8-methoxy-1.4-dihydro-4-oxo-3-quinolinecarboxylic acid) gives rise to an additional adsorption peak corresponding to the reduction of Co(II)-moxifloxacin complex on the mercury drop electrode at −1.17 V. This new peak is applicable to Co(II) determination with the linearity proportional to the Co(II) concentration in the range of 4.93 × 10⁻⁷−6.90 × 10⁻⁵ M and can be attributed to an adsorption-controlled process with an irreversible reduction. Without using moxifloxacin, the polarographic determination of 2.50 × 10⁻⁶ M Co(II) is impossible under the given conditions due to very poor sensitivity at −1.38 V. The proposed method showed good precision and accuracy with a relative standard deviation of 3.01% and relative error of +6.40% for the determination of 2.50 × 10⁻⁶ M Co(II) next to 5.0 × 10⁻⁶ M of Zn(II), Ni(II), and Cd(II). The accuracy of the method was also checked by the determination of Co(II) spiked with tap water and certified sea water, and the percentage recoveries were 97.5 and 96.7%, respectively (n = 4 at 95% confidence interval). The text was submitted by the authors in English.     

Speciation analysis of vanadium in natural water samples by electrothermal vaporization inductively coupled plasma optical emission spectrometry after separation/preconcentration with thenoyltrifluoroacetone immobilized on microcrystalline naphthalene

A sensitive and simple method for low temperature electrothermal vaporization inductively coupled plasma optical emission spectrometry (ETV-ICP-OES) determination of V(IV) and V(V) after separation/preconcentration by a micro-column packed with immobilized thenoyltrifluoroacetone (TTA) on microcrystalline naphthalene has been developed. Thenoyltrifluoroacetone was used as both a chelating agent for micro-column separation/preconcentration and a chemical modifier for ETV-ICP-OES determination of vanadium. Both vanadium species could be trapped by micro-column at pH 4.0, and the vanadate (VO₂⁺) ion could be collected selectively at pH 2.4. Solid material loaded with analyte in the micro-column was dissolved with 100 μL of acetone containing 2.0 mmol L⁻¹ TTA and the vanadium was determined subsequently by ETV-ICP-OES. The concentration of vanadyl (VO²⁺) ion was calculated by subtracting the vanadate concentration from the total concentration of vanadium. Under the optimized experimental conditions, the detection limit (3σ) for the preconcentration of 5 mL of aqueous solution is 0.068 μg L⁻¹ for both species and the relative standard deviations were 4.3% for vanadium(V) and 4.8% for vanadium(IV) (c=10 μg L⁻¹, n=7), respectively. The method was applied successfully to the determination of vanadium(IV) and vanadium(V) in natural water samples.     

Titrimetric and Spectrophotometric Determination of Some Phenothiazine Psychotropics in Pure Form and in Pharmaceutical Formulations with Metavanadate

 Two simple, fast, accurate and precise methods for the determination of six phenothiazines and a number of their pharmaceutical formulations are described. The titrimetric method involves the oxidation of the drugs by metavanadate in sulphuric acid medium and titration of vanadium(IV) formed, with cerium(IV) using ferroin indicator and acetone as catalyst. In spectrophotometry, vanadium(IV) formed was reacted with ferriin and the resulting ferroin measured at 510 nm. Phenothiazines in the ranges 5–100 mg and 2.5–25.0 μg mL⁻¹ can be determined by titrimetry and spectrophotometry, respectively, with detection limits of 0.96–2.05 mg and 0.0359–0.0565 μg mL⁻¹, respectively. Both methods were applied successfully to the determination of the studied drugs in pharmaceutical preparations. The reliability of the assays was established by parallel determination by the official methods of British Pharmacopoeia and the results being statistically evaluated. Received September 26, 2000. Revision March 25, 2001.