Determination of picomolar concentrations of bromide with a piezoelectric detector by catalysis of the permanganate/iodide reaction

The piezoelectric quartz crystal has been utilized to detect iodine produced by the bromide- catalyzed oxidation of iodine to iodate by permanganate in acidic solution. After extraction of iodine into toluene, the resulting frequency change caused by iodine adsorption on the crystal electrode is proportional to bromide concentration over the range 0.5–5 × 10^?12 M. Only silver (I), mercury(II) and large concentrations of chloride interfere significantly. The crystal detector is also used to indicate the end-point of a chloride titration with silver.     

Simultaneous determination method of radon-222 and radon-220 by a toluene extraction-liquid scintillation counter

A new determination method for²²²Rn and²²⁰Rn in water sample was developed by extracting radon with toluene and applying the integral counting method with a liquid scintillation counter. The essential characteristics of the methods are, (1) extraction of radon with toluene from water, (2) finding absolute counts and making corrections for the quenching effect by the adoption of the integral counting method, (3) the determination of²²²Rn and²²⁰Rn was performed by counting the activity of²²⁰Rn with its descendants and of ThB (²¹²Pb) with its descendants in a radioactive equilibrium, respectively, (4) realizing high sensitivity by simultaneous counting of α, β⁻ particles emitted from the decay products formed in toluene. The lowest detection limit obtained by the present method was 5.0·10⁻¹³ Ci/l for²²²Rn and 6.8·10⁻⁸ Ci/l for²²⁰Rn in water.     

Extraction by Mixed Solvent and Spectrophotometric Determination of Sodium Dodecyl Sulfate in Sea Water

Mixed solvent was used to extract ion pairs formed from suitable cationic dye and sodium dodecyl sulfate in sea water. The extracts were used for spectrophotometric determinations. The extraction of ion pairs of various combinations is discussed. Ethyl violet and a mixture (1:1) of p-xylene and toluene are the most useful combination as the cationic dye and the extraction solvent. The extracts were determined spectrophotometrically at 611.2 nm; the molar absorptivity is 1.27 × 10⁵ M^?1 cm^?1. The detection limit is 2.0 ppb in water based on three times the standard deviation of the blank. Extraction with this mixed solvent is as rapid and sensitive as with the best single solvent.     

Rapid determination of 226Ra in drinking water samples using dispersive liquid-liquid microextraction coupled with liquid scintillation counting

A new radioanalytical method was developed for rapid determination of ²²⁶Ra in drinking water samples. The method is based on extraction and preconcentration of ²²⁶Ra from a water sample to an organic solvent using a dispersive liquid-liquid microextraction (DLLME) technique followed by radiometric measurement using liquid scintillation counting. In DLLME for ²²⁶Ra, a mixture of an organic extractant (toluene doped with dibenzo-21-crown-7 and 2-theonyltrifluoroacetone) and a disperser solvent (acetonitrile) is rapidly injected into the water sample resulting in the formation of an emulsion. Within the emulsion, ²²⁶Ra reacts with dibenzo-21-crown-7 and 2-theonyltrifluoroacetone and partitions into the fine droplets of toluene. The water/toluene phases were separated by addition of acetonitrile as a de-emulsifier solvent. The toluene phase containing ²²⁶Ra was then measured by liquid scintillation counting. Several parameters were studied to optimize the extraction efficiency of ²²⁶Ra, including water immiscible organic solvent, disperser and de-emulsifier solvent type and their volume, chelating ligands for ²²⁶Ra and their concentrations, inorganic salt additive and its concentration, and equilibrium pH. With the optimized DLLME conditions, the accuracy (expressed as relative bias, B _r ) and method repeatability (expressed as relative precision, S _B ) were determined by spiking ²²⁶Ra at the maximum acceptable concentration level (0.5 Bq L⁻¹) according to the Guidelines for Canadian Drinking Water Quality. Accuracy and repeatability were found to be less than −5% (B _r ) and less than 6% (S _B ), respectively, for both tap water and bottled natural spring water samples. The minimum detectable activity and sample turnaround time for determination of ²²⁶Ra was 33 mBq L⁻¹ and less than 3 h, respectively. The DLLME technique is selective for extraction of ²²⁶Ra from its decay progenies.     

The spectrophotometric determination of arsenic in sea water,potable water and effluents

Procedures are described for the determination of arsenic in sea water, potable waters and effluents. The sample is treated with sodium borohydride added at a controlled rate. The arsine evolved is absorbed in a solution of iodine and the resultant arsenate ion is determined photometrically by a molybdenum blue method. The time required for a complete analysis is about 90 min, but of this only 15 min is operator time. For sea water the range, standard deviation, and detection limit are 1–4 μgl^-1, 1.4 % and O.14 μg l^-1, respectively; for potable waters they are 0–800 μg l^-1, about 1 % (at 20μg l^-1 level) and 0.5μg l^-1, respectively. Silver and copper cause serious interference at levels of 0.5 mgl^-1, and nickel, cadmium and bismuth interfere at concentrations of a few tens of mg l^-1; however, these elements can be removed either by preliminary extraction with a solution of dithizone in chloroform or by ion exchange. Arsenic present in organo-arsenic compounds is not directly determinable, but can be rendered reactive either by photolysis with ultraviolet radiation or by oxidation with permanganate or nitric—sulphuric acid mixture. Arsenic(V) can be determined separately from total inorganic arsenic after extracting arsenic(III) as its pyrrolidine dithiocarbamate into chloroform.     

The determination of tin in biological samples

A rapid method is described for the determination of tin in biological material, using¹²³Sn (T=40 m). The chemical procedure is based on the nearly quantitative extraction of tetravalent tin into toluene from an acid 1.3M iodide solution. The recovery is determined by spiking the solution with¹¹³Sn and measuring the activity of the^113mIn daughter in the counting sample. The lower limit of the determination is ?0.01μg. Results are given for standard kale powder and dried animal blood.     

Rapid determination of131I in environmental waters using a liquid anion exchanger

A rapid and specific method for the determination of¹³¹I in environmental water samples in the presence of some of the most important fission products is described. Radioiodine is separated from acidified water using tri-n-octylamine solution in toluene with dissolved iodine by one-stage static procedure with about 90% separation efficiency and 200-fold volume concentration. After the decolorization of the organic phase with NaOH in methanol, radioactivity of¹³¹I is counted by a toluene base liquid scintillator with a counting efficiency of 70%. The method is simple and enables to determine low radioactivity¹³¹I with a detection limit less than 5 pCi/1 in about 1.5 hrs.     

Determination of Anionic Surfactant in Fresh Water and in Sea Water

Ion pairs formed from suitable cationic dye and anionic surfactant in water were separated by solvent extraction. The extracts were used subsequently for spectrophotometric determinations. The extraction of ion pairs with various combinations is described. Of the dyes and solvents examined, ethyl violet and p-xylene are the most useful combination as the cationic dye and extraction solvent. The extracts are determined spectrophotometrically at 611.5 nm; the molar absorptivity is 1, 01 × 10⁵ M^?1 cm^?1. The detection limit is 1.4 ppb in water. The method is simple, rapid and sensitive. It can also be applied to the determination of anionic surfactants in sea water.     

Extraction of pesticides in water samples using vortex-assisted liquid–liquid microextraction

A simple solvent microextraction method termed vortex-assisted liquid–liquid microextraction (VALLME) coupled with gas chromatography micro electron-capture detector (GC-μECD) has been developed and used for the pesticide residue analysis in water samples. In the VALLME method, aliquots of 30 μL toluene used as extraction solvent were directly injected into a 25 mL volumetric flask containing the water sample. The extraction solvent was dispersed into the water phase under vigorously shaking with the vortex. The parameters affecting the extraction efficiency of the proposed VALLME such as extraction solvent, vortex time, volumes of extraction solvent and salt addition were investigated. Under the optimum condition, enrichment factors (EFs) in a range of 835–1115 and limits of detection below 0.010 μg L⁻¹ were obtained for the determination of target pesticides in water. The calculated calibration curves provide high levels of linearity yielding correlation coefficients (r²) greater than 0.9958 with the concentration level ranged from 0.05 to 2.5 μg L⁻¹. Finally, the proposed method has been successfully applied to the determination of pesticides from real water samples and acceptable recoveries over the range of 72–106.3% were obtained.     

Simultaneous radiochemical neutron activation analysis of iodine, uranium and mercury in biological and environmental samples

The determination of medium and long-lived nuclides can be combined with short-lived ones if a medium or long irradiation is made prior to the short irradiation and radiochemical processing. Thus, an RNAA method previously developed for determination of iodine based on the reaction¹²⁷I(n,)¹²⁸I (T _1/2=25 m) using oxygen flask ignition of the irradiated sample, followed by solvent extraction with an iodine-iodide redox cycle, was combined with an overnight preirradiation to induce the²³⁵U fission product¹³³I (T _1/2=20.8 h). By reactivating the sample, cooled 1–2 days after the first irradiation, for few minutes both¹²⁸I and¹³³I could be quantified in the separated iodine fraction. Non-combustible inorganic materials (e.g., sediment, soil, etc.) can be successfully ignited after mixing with excess cellulose powder. Chemical yields for iodine were determined spectrophotometrically in the organic phase, while homogeneously spiked Whatman cellulose powder was used as uranium standard. Mercury is also released on ignition and collected in the absorbing solution, from where it was separated by toluene extraction. Its chemical yield was determined for each aliquot using²⁰³Hg tracer and counting on an LEPD. Results for some suitable SRMs are presented, and the general features of the double irradiation technique discussed.     

The determination of iodide in sea water by neutron activation analysis

A simple and sensitive method for the determination of iodide in sea water by neutron activation analysis has been developed. Iodide is separated from most other anions by passing sea water through a strongly basic anion-exchange column, recovered by elution with 2 M sodium nitrate, and concentrated from the eluate by precipitation as palladium(II) iodide in the presence of excess of palladium(II) with elemental palladium as carrier; elemental palladium is generated by reduction of some of the palladium(II) with thiosulfate. The precipitate is separated from the supernatant liquid by filtration. Checks on the efficiency of separation by means of added ¹²⁵I showed recoveries of 100 ± 3 %. The filter paper containing the precipitate is pressed into a pellet for neutron activation analysis by irradiation for 5 min at a flux of 4 ·10¹² n cm^?2 s^?1 and counting the ¹²⁸I 442.7-keV photopeak.     

Determination of technetium-99 from the aspect of environmental radioactivity

A radioanalytical procedure has been developed for the determination of⁹⁹Tc in environmental samples. The procedure consists of precipitation, solvent extraction, ion exchange, electrodeposition and radiation measurement. Rhenium was used as a non-isotopic carrier of⁹⁹Tc. On the basis of 3σ counting error, the detection limits were 4.9·10^?5 Bq/l, 7.4·10^?3 Bq/kg wet and 7.4·10^?2 Bq/kg dry for water, biota and soil samples, respectively. Sea water, seaweeds (brown algae) and soils were collected to evaluate the present levels of⁹⁹Tc in Japan. The level of⁹⁹Tc in sea water was ca. 1·10^?4 Bq/l around Japan. Among the seaweeds (brown algae), Ishige okamurai showed the highest concentration of 5.8·10^?2 Bq/kg wet tissue and the highest concentration factor of 583. The level of⁹⁹Tc in the organic rich surface soil was ca. 1 Bq/kg dry soil in Fukuoka.     

Comparison of Different Extraction Techniques of Polychlorinated Biphenyls from Sediments Samples

In this work, problems that may occur during determination of trace levels of polychlorinated biphenyls in sediment samples are described. Main error sources are connected with extraction of analytes prior to final determination.

During model studies, polychlorinated biphenyls have been extracted from sediment reference material (METRANAL 2) with the use of different solvents (dichloromethane, hexsane, and toluene); the process has been enhanced by mechanical shaking or ultrasounds. Seven selected PCBs (PCB 28, 52, 101, 118, 138, 153, and 180 – according to IUPAC) were determined in extracts samples by GC–MS technique.

During the studies, two calculation methods were applied to determine the amount of analytes introduced to the chromatographic column. The first approach assumes that the recovery of PCBs that contained a small amount of chlorine atoms in the molecule is similar to the recovery of ¹³C₁₂PCB28 standard, whereas compounds with greater number of chlorine atoms in the molecule will be recovered from the sediment similarly to the recovery of ¹³C₁₂PCB180 standard. The second approach assumes that the recovery of PCB 138 and PCB 153 is similar to the average value of ¹³C₁₂PCB28 and ¹³C₁₂PCB180 standards.

In the case of shaking assisted extraction, 55–90% PCB recoveries were achieved when toluene was used as a solvent, while 71–86% recovery was achieved when dichloromethane was used. When hexsane was used as solvent, recovery ranged 43–107%. In the case of ultrasounds assisted extraction, PCB recoveries of 50–108% were achieved when toluene was used as solvent, while 44–101% recovery was achieved when dichloromethane was applied. When hexsane was used as solvent, recovery reached 57–95%.

Studies have also shown that, when applying different isolation techniques and different solvents, the recovery of applied ¹³C₁₂PCB28 and ¹³C₁₂PCB180 standards is different. Recovery of ¹³C₁₂PCB28 standard was from 5% (for hexane tenfold extraction assisted by shaking) to 57% (for toluene tenfold extraction assisted by shaking). However, recovery of ¹³C₁₂PCB180 standard was from 9% (for hexane tenfold extraction assisted by shaking) to 82% (for toluene tenfold extraction assisted by shaking). This is due to the differences of their binding to the sludge matrix. Standard with a greater number of chlorine atoms in the molecule (¹³C₁₂PCB180) is more weakly associated with sediment than ¹³C₁₂PCB28 standard. In order to improve the accuracy of the results obtained, it is necessary to use labeled PCB compounds.     

A sensitive method based on HDEHP extraction and LSS for the determination of 90Sr in solid samples

An improved and rapid method is described for the determination of ⁹⁰Sr in environmental samples, through the separation of the daughter ⁹⁰Y at equilibrium. The procedure is based on the HDEHP solvent extraction in combination with liquid scintillation spectrometry (LSS). A low background QuantulusÔ has been optimized for low level counting of Cerenkov radiation emitted by the hard b-emitter ⁹⁰Y. The counting efficiency was 60% and the background 0.53 cpm. The reliability and reproducibility of the method have been checked using IAEA reference materials. The chemical recovery for ⁹⁰Y extraction ranges from 83 to 90%.     

Field determination of iodide in water

A simple, fast and sensitive spectrophotometric method for the quantification of iodine and iodide in waters is described. Firstly iodide has been oxidised by sodium nitrite to iodine in HCl medium and the resulting I₂Cl^– has been preconcentrated into toluene. This can be subsequently determined in the extract with brilliant green. A ten-fold preconcentration is obtained, the molar absorptivity is (4.2×10⁴) I mol^–1 cm^–1 at 635 nm. A detection limit of 4 ng/ml iodide in water can be reached. The effect of common anions and cations have been investigated. The method has been applied to the determination fo free iodine, total iodine and iodide in river, pond and well water.     

Simultaneous Derivatization and Dispersive Liquid–Liquid Microextraction for Fatty Acid GC Determination in Water

Simultaneous derivatization and dispersive liquid–liquid microextraction technique for gas chromatographic determination of fatty acids in water samples is presented. One hundred microlitre of ethanol:pyridine (4:1) were added to 4 mL aqueous sample. Then a solution containing 0.960 mL of acetone (disperser solvent), 10 μL of carbon tetrachloride (extraction solvent) and 30 μL of ethyl chloroformate (derivatization reagent) were rapidly injected into the aqueous sample. After centrifugation, 1 μL sedimented phase with the analytes was analyzed by gas chromatography. The effects of extraction solvent type, derivatization, extraction, and disperser solvents volume, extraction time were investigated. The calibration graphs were linear up to 10 mg L^?1 for azelaic acid (R ² = 0.998) and up to 1 mg L^?1 for palmitic and stearic acids (R ² = 0.997). The detection limits were 14.5, 0.67 and 1.06 μg L^?1 for azelaic, palmitic, and stearic acids, respectively. Repeatabilities of the results were acceptable with relative standard deviations (RSD) up to 13%. A possibility to apply the proposed method for fatty acids determination in tap, lake, sea, and river water was demonstrated.     

Liquid scintillation method for determination of solvent-extracted phosphorus-32 in foods

A method for solvent extraction of radioactive phosphorus as phospho-molybdic acid in foods is described. The use of a carrier can be eliminated due to the quantity of the stable element present in foods. The use of a liquid scintillation technique for counting is discussed, showing the effective elimination of color and chemical quench. The efficiency resulting from the liquid scintillation method of counting makes possible the detection of 10^-5 μc levels of activity in the original sample.     

Analysis of low-level 129I in brine using accelerator mass spectrometry

An improved solvent extraction procedure for iodine separation from brine samples has been applied at Xi’an Accelerator Mass Spectrometry (AMS) center. Oil in the brine sample has to be removed to avoid appearance of the third phase during solvent extraction and to improve the chemical yield of iodine. The small amount of oil remained in the water phase was first removed by phase separation through settling down sufficiently based on their immiscibility, and then by filtration through a cellulose filter, on which oil was absorbed and removed. After oil removed, extraction recovery of iodine could achieve more than 90 %. The sodium bisulfite as an effective reductant should be added before acidification to avoid loss of iodine by formation of I₂ in sample via reaction of iodate and iodide at pH 1–2, and then pH was adjusted to 1–2 to reduce the iodate to iodide followed by oxidation of iodide to I₂ and solvent extraction to separate all inorganic iodine. As a pre-nuclear era sample, ¹²⁹I/¹²⁷I ratio in brine is normally more than two orders of magnitude lower than that in present surface environmental samples, so prevention of cross-contamination and memory effect in apparatus during processing procedure are very critical for obtaining reliable results, and monitoring the procedure blank is very important for analytical quality of ¹²⁹I. The ¹²⁹I/¹²⁷I isotopic ratio in the brine samples and procedure blank of iodine reagents were measured to be (1.9–2.7) × 10^?13 and 2.08 × 10^?13, respectively, 3–4 orders of magnitudes lower than that in environmental samples in Xi’an, and the result of procedure blank is in the same level as the previous experiments in past 3 years, indicating contamination is not observed in our method.     

A novel approach in dispersive liquid-liquid microextraction based on the use of an auxiliary solvent for adjustment of density: UV-VIS spectrophotometric and graphite furnace atomic absorption spectrometric determination of gold based on ion pair formation

This paper presents a novel approach to dispersive liquid-liquid microextraction (DLLME), based on the use of an auxiliary solvent for the adjustment of density. The procedure utilises a solvent system consisting of a dispersive solvent, an extraction solvent and an auxiliary solvent, which allows for the use of solvents having a density lower than that of water as an extraction solvent while preserving simple phase separation by centrifugation. The suggested approach could be an alternative to procedures described in the literature in recent months and which have been devoted to solving the same problem. The efficiency of the suggested approach is demonstrated through the determination of gold based on the formation of the ion pair [Au(CN)₂]⁻ anion with Astra Phloxine (R) reagent and its extraction using the DLLME procedure with subsequent UV-VIS spectrophotometric and graphite furnace atomic absorption spectrometric detection. The optimum conditions were found to be: pH 3; 0.8 mmol L⁻¹ K₄[Fe(CN)₆]; 0.12 mmol L⁻¹ R; dispersive solvent, methanol; extraction solvent, toluene; auxiliary solvent, tetrachloromethane. The calibration plots were linear in the ranges 0.39-4.7 mg L⁻¹ and 0.5-39.4 μg L⁻¹ for UV-VIS and GFAAS detection, respectively; thus enables the application of the developed method in two ranges differing from one from another by three orders of magnitude. The presented approach can be applied to the development of DLLME procedures for the determination of other compounds extractable by organic solvents with a density lower than that of water.     

The determination of organic and inorganic lead compounds in urban air by atomic-absorption spectrometry with electrothermal atomization

A method for the simultaneous determination of inorganic and organic lead compounds in air is described, together with some results from its application at different sampling sites. Air-borne particulate lead is collected on a cellulose filter. Organic lead vapours are trapped in an iodine monochloride solution, placed behind the filter. A fraction of the cellulose filter is subjected to low-temperature ashing, after which the lead content in the residue is measured by electrothermal atomic-absorption spectrometry. The organolead material absorbed in the iodine monochloride solution, is determined by solvent extraction and electrothermal atomic-absorption spectrometry. For a 6-h sampling period, detection limits of the order of 10 ng m^-3 for inorganic and 8 ng m^-3 for organic lead materials may be obtained.