Photometric cyclic-injection determination of arsenic in aqueous solutions

A procedure for the photometric on-line determination of trace arsenic in aqueous solutions was developed. The procedure is based on the reaction gas extraction of arsenic as arsine followed by liquid-absorption separation from a gas phase into a solution of a photometric reagent (2-(p-nitrophenyl)-3,5-diphenyltetrazolium chloride). The determination limit was 10 μg/L at a sample volume of 50 mL.     

Determination of Arsenic with Michler's Thioketone

Michler's thioketone is proposed as the reagent for the spectrophotometric determination of trace arsenic(V). The molar absorptivity of the colored product of interaction between Michler's thioketone and molybdoarsenic acid is (1.02 ± 0.04) × 10⁵at 640 nm. A procedure is developed for the extraction–photometric determination of arsenic in tap and mineral waters. The added–found method is used. The determination limit of arsenic is 0.003 mg/L; in the concentration range 0.008–0.12 mg/L, the relative standard deviation varies from 20 to 8 %.     

Determination of Inorganic and Total Arsenic in Wines by Hydride Generation Atomic Absorption Spectrometry

A method is described for the determination of inorganic arsenic species and total arsenic in wines by means of hydride generation atomic absorption spectrometry (HGAAS). Simple ethanol evaporation is the only pretreatment procedure proposed for wine samples prior to direct measurement of inorganic arsenic (AsIII) and As(V) species by HGAAS. The total arsenic content is determined after microwave digestion of the wine samples. The optimal parameters for the microwave digestion procedure and the next HGAAS measurement of arsenic are established. The detection limits achieved are 0.1µgL^–1 for inorganic and total arsenic determination. The relative standard deviation for both procedures and for ten independent determinations varied between 8 and 15% for arsenic species in the range of 1–30µgL^–1. The accuracy of the procedure for total arsenic determination was proved by comparative analysis using electrothermal atomic absorption spectrometry.     

Liquid Chromatographic Determination of Glutamine in Cerebrospinal Fluid Using 2-Hydroxynaphthaldehyde Derivatizing Reagent

Summary An analytical procedure has been developed for the selective determination of glutamine from cerebrospinal fluid (CSF) using 2-hydroxynaphthaldehyde derivatizing reagent. Arginine and tyramine could also be determined simultaneously. Separation was on a Phenomenex C-18, (150 × 4.6 mm i.d.) column with methanol: water (63:38 v/v) mobile phase at 1mL min^–1 and UV detection at 330nm. Detection limits for glutamine, arginine, and tyramine were 2.8 ng, 17.4 ng and 3.45 ng injection^–1 (5 L), respectively. A large number of amines and amino acids eluted did not affect the determination of glutamine. The analysis of CSF of four patients suffering from hydrocephalus for glutamine indicated concentrations within range 37.4–11.24 g mL^–1 with coefficient of variation 3.0–6.2%.     

Radiochemical studies on the extraction of arsenic(III) by trilaurylamine oxide and benzene from aqueous iodide solutions and its determination in water samples by spectrophotometry

An extraction system consisting of trilaurylamine N-oxide and benzene has been identified as a possible extractant for tracer arsenic (<10^–3 M) from hydrochloric or sulfuric acid solutions with or without iodide. Benzene alone is less efficient as an extractant for arsenic when compared with trilaurylamine oxide dissolved in benzene. The mechanism of extraction is attributed to the formation of hydrated AsCl₃, while the iodide complex is most probably AsI ₄ ^– . The role of the solvent and the other parameters affecting the extraction have been investigated. The results have been employed to determine arsenic in water samples by spectrophotometry using the molybdenum blue method. The extraction procedure was used for the analysis of 10 ml water samples containing 0.2–0.5 g of arsenic.     

Determination of trace amounts of phosphate by flow-injection photometry

This paper describes a simple and rapid procedure for determination of traces of phosphate by means of molybdenum blue chemistry. The use of a cost-effective home-made flow cell with a long path length in combination with a light emitting diode (LED) and a photodiode (PD) is demonstrated as a simple absorbance detector for flow-injection analysis. In this method, a sample is injected into the carrier stream through an injection valve and mixed online with mixed reagent (a mixture of molybdate, bismuth, and ascorbic acid in sulfuric acid). The color intensity of the resulting association complex, molybdenum blue, is measured photometrically (_max 875 nm). The proposed method can be used to detect phosphate in the range 0.02–4.0 mg L^–1 and the precision of the proposed procedure is less than 5% at 0.1 mg L^–1 phosphorus as phosphate. The method has been successfully applied to a variety of natural water samples.     

Extract-photometric determination of vanadium(V) with 3-indole-acetohydroxamic acid

Summary A spectrophotometric study has been carried out of the violet complex 3-indole-acetohydroxamic acid-vanadium extracted into a solution of trioctylmethyl-ammonium chloride in toluene [_max 525 nm; =5381 l mol^–1 cm^–1; stoichiometry 1:3 (metal:reagent)]. A new method for the extract-spectrophotometric determination of V⁵⁺ in the range of 2–7 g/g is proposed and interferences by foreign ions were investigated. The method has been satisfactorily applied to the determination of vanadium(V) in fuel oil. The relative error is ±2.9%.     

On-line sample preparation and determination of phenols with a Flow-Analysis method

Summary A Flow-Analysis system has been developed to automate the phenol determination according to the German standard method DIN 38409-H16-2. The automation leads to a significant acceleration of the procedure. One analysis only lasts 3 min while the complete manual determination requires 3 h. Also the sample, solvent and reagent volumes are reduced to a tenth of the volumes demanded by the standard method. The described phenol determination is based on the integration of an airsegmented (Airsegmented-Flow-Analysis SFA) part in a Flow-Injection-Analysis (FIA) system. The main steps of the analytical procedure are: Reproducible inserting of the sample in a carrierstream, sample pretreatment and sample measuring. In the first step the sample is injected into the carrierstream. It transports the sample in the reactioncoil and than through the distillation unit. The steam distillation represents the sample preparation step; therefore an airsegmented stream is necessary. Afterwards the different phases (liquid and gas) were singled again and the distilled solution is fed into the FIA manifold. The determination itself takes place inside the FIA system. The limit of determination amounts to 0.01 mg l^–1 with a standard deviation of 1.5%. Different waste, surface and drinking water samples have been analyzed without any problems. The results correspond very well to those obtained by manual procedure.     

Indirect determination of arsenic by flotation spectrophotometry

An indirect method of arsenic determination in the submicrogram range via the determination of molybdenum is presented here. High sensitivity is achieved by combination of the chemical amplification during formation of dodecamolybdoarsenic acid (arsenic: molybdenum ratio 1 12) with multiplication due to the formation of ion-association complexes during flotation-spectrophotometric molybdenum determination with crystal violet (molar ratio 1 2). Thus, the amplification factor relating to arsenic is 24.Dodecamolybdoarsenic acid is formed in a weakly acidic medium and is quantitatively extracted byn-butanol. Back extraction of the heteropoly acid to the aqueous phase and its simultaneous destruction provides the basis for the reaction of released molybdate ions with thiocyanate ions. The molybdenum-thiocyanate complex forms a sparingly soluble ion-association complex with crystal violet which can be floated with toluene on the phase boundary (film flotation). After separation of the aqueous phase the floated molybdenum compound is dissolved in acetone and the resulting free crystal violet ions are subjected to photometric determination at 590 nm as equivalent of the concentration of arsenic. The molar absorptivity of crystal violet is 3.2 · 10⁵1 · mol^–1 · cm^–1. Beer's law is obeyed in a concentration range from 0.01 to 1 g Mo · ml^–1 (0.001–0.1 g As · ml^–1). The resulting detection limit for arsenic is 1 ng · ml^–1.     

Speciation of arsenic compounds by coupling high-performance liquid chromatography with inductively coupled plasma mass spectrometry

There is considerable evidence that toxicity and physiological behavior of arsenic depends on its chemical forms. Arsenic speciation became therefore the subject of increasing interest in recent years. A sensitive method for the determination of arsenic species has been developed. The proposed procedure involves the use of high-performance liquid chromatography and inductively coupled plasma mass spectrometry (HPLC-ICP-MS). Six arsenic compounds were separated by anion-exchange chromatography with isocratic elution using tartaric acid as mobile phase with an elution order: arsenocholine, arsenobetaine, dimethylarsinic acid, methylarsonic acid, arsenous acid and arsenic acid. The chromatographic parameters affecting the separation of the arsenic species were optimized. Analytical characterization of the method has been realized with standard solutions. The detection limits for six arsenic compounds were from 0.04 to 0.6 g/L as As element. The repeatability (expressed by R.S.D) was better than 7% for all investigated compounds. The HPLC-ICP-MS system was successfully applied to the determination of arsenic compounds in environmental and biological samples in g/L level.     

Flow-Injection Determination of Trace Antimony in Natural Waters with Extraction–Chromatographic Preconcentration

A procedure was developed for the flow-injection spectrophotometric determination of trace antimony in natural waters. The flow extraction preconcentration step involved the extraction of antimony(V) complex associates with basic dyes in an extraction–chromatographic column and the chromatomembrane separation of the extract from the aqueous phase. The detection limit was 1 g/L for a 20-mL sample using a (1 : 5) methyl isobutyl ketone–carbon tetrachloride mixture as an extractant.     

Inductively coupled plasma atomic emission spectrometric determination of arsenic in mussel products

Summary A precise, accurate procedure is proposed for the determination of arsenic in mussel products by inductively coupled plasma atomic emission spectrometry. Organic matter is destroyed by dry ashing. Experimental conditions for the determination of arsenic were selected and an interference study was carried out. The methodology developed has a detection limit of 0.1 g g^–1, a relative standard deviation of 3%, and a recovery percentage of 98±2%. The accuracy of the method was checked by analysis of a certified sample of NIST oyster tissue (certified 14.0±1.2 g g^–1; found 14.1±1.1 g g^–1). The proposed procedure was used to analyze real samples of mussel products.     

Studies on the equilibrium uptake of some metal ions on a mixed and doped hydrous oxide using radiotracers

A highly sensitive and rapid method has been developed for the extraction-spectrophotometric determination of ultra trace amounts of americium. Americium(III) is selectively extracted from 1–10M HNO₃ medium with a mixture of (0.3M HDEHP+0.1M P₂O₅), both dissolved in xylene, and finally estimated in the organic phase itself absorptiometrically employing Arsenazo-III as the chromogenic reagent. A 60% dioxaneethanol mixture was used for optium colour development. Beer's law is obeyed in the concentration range 0.1–0.7 g Am cm^–3 and as little as 0.11 g Am cm^–3 could be determined with a precision better than ±2%. The molar absorptivity based on Am content is (3.599±0.049)·10⁵ dm³·mol^–1·cm^–1 at 648 nm which is incidentally the highest value reported as yet for its determination. The optimum concentration range, evaluated by Ringbom's method is 0.1–0.6 ppm Am. Common contaminants such as Al³⁺, Co²⁺, Cr³⁺, Fe³⁺, Ni²⁺, Zr⁴⁺, F^–, NO₃ ^–, and SO ₄ ^2- in fairly large quantities and moderate amounts of Pu⁴⁺, Th⁴⁺ and UO ₂ ²⁺ cause no interference in the final assay. Colour development is almost instantaneous and its intensity remains virtually constant for at least 48 hours.     

Determination of toxic and non-toxic arsenic species in urine by microwave assisted mineralization and hydride generation atomic absorption spectrometry

Flow injection — microwave oven — hydride generation — atomic absorption spectroscopy (FI-MO-HG-AAS) has been optimized for the determination of the total and toxic arsenic in urine with and without persulfate, respectively. With microwave oven assisted digestion of urine with 5% (w/v) K₂S₂O₈ and 5% (w/v) NaOH all arsenicals completely can be converted to arsenate, which is determined by HG-AAS to give the total concentration of the six species present in urine. The detection limits of 4–6 g l^–1, the relative standard deviation of 3–7% and the high sample throughput make the methods suitable for rapid routine on-line determination. Application of the proposed procedures to the analysis of urine from people on a diet rich in seafood revealed a significant increase in total urinary arsenic due to the rapid excretion of organoarsenicals. Efficient decomposition and quantitative recovery of all arsenic species in spiked urine is achieved by using 5% K₂S₂O₈ in 5% NaOH at 4.6 ml min^–1, microwave power of 700 W and a 1.5 m coil.     

Rapid electrothermal atomic absorption method for arsenic and selenium in geological materials via hydride evolution

Summary A rapid semi-automated hydride evolution-electrothermal atomic absorption spectrophotometric method has been developed for the determination of arsenic and selenium in geological materials. A representative sample of a rock, soil or sediment is digested with a mixture of HNO₃-HClO₄. The nearly dry digestate is taken up in HCl. The arsenic (or selenium) in the hydrochloric acid solution is converted to its hydride with sodium borohydride. The hydride is decomposed and atomized in an electrically heated quartz furnace, and the atomic absorption signal is measured at the appropriate resonance wavelengths of arsenic and selenium. Both the elements can be reliably determined in geochemical samples in the range of 0.05–2.00 g/g. The method has wide tolerance for variation in reagent concentrations and possible interferences, and when tested on some certified rocks having a wide range of arsenic and selenium values is found to be satisfactorily accurate and precise. The procedure is now routinely used in our laboratories. At least 10 samples can be analyzed per hour.

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Schnelles elektrothermisches AAS-Verfahren zur Bestimmung von Arsen und Selen in geologischem Material über die Hydridbildung

Zusammenfassung Bei dem beschriebenen Verfahren wird die Probe mit einem Salpetersäure-Perchlorsäure-Gemisch aufgeschlossen, der Rückstand in Salzsäure aufgenommen und Se bzw. As mit Hilfe von Natriumborhydrid in Hydrid übergeführt. Die Atomisierung zur Messung erfolgt in einem elektrisch beheizten Quarzofen. Beide Elemente können im Bereich von 0,05–2,00 g/g zuverlässig in geologischem Material bestimmt werden. Die Methode hat einen weiten Toleranzbereich für Änderungen der Reagenskonzentration sowie für mögliche Begleitelemente und zeigte bei Referenz-Gesteinsproben zufriedenstellende Ergebnisse. Sie wird in den Laboratorien des Autors routinemäßig eingesetzt. Wenigstens 10 Proben können innerhalb von 1 h analysiert werden.

     

Investigation of 2-[(<Emphasis Type="Italic">E</Emphasis>)-2-(4-diethylaminophenyl)-1-ethenyl]-1,3,3-trimethyl-3H-indolium as a new highly sensitive reagent for the spectrophotometric determination of nitrophenols

A new, simple, rapid, and sensitive spectrophotometric method has been developed for the determination of nitrophenols [picric acid (PA); dinitrophenols (DNP)] in wastewater samples. The method is based on the reaction of nitrophenols with 2-[(E)-2-(4-diethylaminophenyl)-1-ethenyl]-1,3,3-trimethyl-3 H-indolium chloride reagent to form the colored ion associates, which are extracted by organic solvents. The molar absorptivity of the ion associates of PA with the investigated reagent ranges from 8.3×10⁴ to 11.3×10⁴ L mol^–1 cm^–1, depending on the extractant. Because only PA is extracted in an acidic medium with the investigated reagent, but both PA and DNP are extracted in an alkaline medium, it is possible to determine both substances in a mixture. Appropriate reaction conditions have been established. The absorbance of the colored extracts obeys Beers law in the range of 0.04–4.58 mg L^–1 PA, 1.0–18.4 mg L^–1 2,4-DNP and 1.2–14.7 mg L^–1 2,6-DNP, respectively. The limit of detections, calculated from a blank test (n=10; P=0.95), are 0.05 mg L^–1 PA, 0.9 mg L^–1 (2,4-DNP), and 1.1 mg L^–1 (2,6-DNP), respectively.     

Flow injection analysis of aromatic sulphonyl haloamines

Summary Flow-injection determination of chloramine-T, dichloramine-T, dibromamine-T, bromamine-T, chloramine-B, dichloramine-B, dibromamine-B, bromamine-B and dichloramine-N in solution, through a spectrophotometric procedure is described. A simplified flow-injection apparatus with a two-channel system is employed. The carrier streams are starch-KI mixture (0.55.0%) and 1 M H₂SO₄ and are merged before injection of haloamine. A sampling frequency of 280h^–1 has been achieved. The effect of reagent concentrations, flow parameters and interferents on the analysis has been investigated. Concentrations of haloamines were in the range of 1–60 ppm.

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Fließinjektions-Analyse von aromatischen Sulfonylhalogenaminen

Zusammenfassung Die spektralphotometrische FIA-Analyse folgender Verbindungen wird beschrieben: Chloramin-T, Dichloramin-T, Dibromamin-T, Bromamin-T, Chloramin-B, Dichloramin-B, Dibroamin-B, Bromamin-B und Dichloramin-N. Ein vereinfachtes 2-Kanal-FIA-Gerät wird benutzt. Trägerlösungen sind KI-Stärke (5.00.5%) und 1 M Schwefelsäure, die vor der Injektion gemischt werden. Ein Probendurchsatz von 280h^–1 wurde erreicht. Einflüsse von Reagenskonzentrationen, Fließparametern und Störsubstanzen wurden untersucht. Die untersuchten Konzentrationen lagen im Bereich von 1–60 ppm.

     

2-[2′-(6′-Methyl-benzothiazolyl)azo]-5-dimethylaminobenzoic acid as a new reagent for rapid spectrophotometric determination of copper

2-[2-(6-methyl-benzothiazolyl)azo]-5-dimethylaminobenzoic acid (MBTAMB) has been synthesized and employed as a new reagent for the spectrophotometric determination of copper(II). A blue complex is formed from MBTAMB and Cu(II) in the range of pH 2.0–5.0 in aqueous ethanol. The composition of the complex is Cu(II) MBTAMB=1 1. The maximum absorption of the complex is at 660 nm, its apparent molar absorptivity is 7.0 × 10⁴ 1· mole^–1 · cm^–1. Beer's law is obeyed for copper in the range of 0–0.72 g/ml. The method has been used for the determination of micro amounts of copper in aluminium alloy. The proposed method is simple, rapid and accurate.     

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.     

Gas Chromatographic Determination of Sulfur Mustard and Lewisite in Community Air

A gas chromatographic procedure is developed for the determination of ,-dichlorodiethylsulfide (yperite, sulfur mustard) and -chlorovinyldichloroarsine (lewisite) in the working area and community air at a level defined by the hygienic regulations for community air (2 × 10^–6 and 4 × 10^–6 mg/m³ for sulfur mustard and lewisite, respectively) and at the maximum permissible level for a working area (2 × 10^–4 mg/m³). The procedure for the determination of sulfur mustard is based on the trapping of the analyte from air with Silochrom S-120 impregnated with Apiezon L with further extraction by a 1 : 1 acetone–hexane mixture, the evaporation of the extract to a small residual volume, and chromatography with an electron capture detector. The procedure for the determination of -chlorovinyldichloroarsine (lewisite) involves the absorption of the analyte with a 2.2% solution of triethanolamine in 0.1 M hydrochloric acid, the conversion of lewisite to acetylene by treating the trap contents with 30% alkali solution, and the chromatography of the vapor phase using a flame ionization detector. The error of the determination is no more than ±23 rel %. The analysis takes 1.5 h.