Extraction—spectrophotometric and fluorimetric determination of thallium with 2-(4-methoxyphenyl)-5,7-diphenyl-4h-l,3,4-thiadiazolo[3,2-α] pyridinium chloride

The synthesis, characteristics and applications of 2-(4-methoxyphenyl)-5,7-diphenyl-4H⁺-1, 3,4-thiadiazolo[3,2-α]pyridinium chloride (TDZP) as a reagent for the formation of ion-pair complexes is described. Tetrachlorothatllate(III) can be extracted into isoamyl acetate as an ion-pair with TDZP. Thallium can be determined spectrophotometrically and fluorimetrically in the range 1–25 and 0.1–2 μg of thallium per 5 ml of organic layer, respectively. The molar absorptivity is 3.9 × 10⁴ l mol^-1 cm^-1. The quantum efficiency of the reagent is 0.42. The method is applicable to the determination of thallium in sphalerites and zinc or cadmium concentrates.     

Manual and fia methods for the determination of cadmium with malachite green and iodide

A sensitive and rapid spectrophotometric method for the determination of cadmium is described, based on the formation of a blue complex at pH 4 between the anionic iodide complex of cadmium(II) and Malachite Green; the colour is stabilized with poly(vinyl alcohol). The calibration graph for measurement at 685 nm is linear over the range 1-50 mug of cadmium per 25 ml of final solution, with a relative standard deviation of +/-1.7% for 1 mug/ml cadmium. The molar absorptivity is 6.1 x 10(4) 1.mole(-1).cm(-1). The method can be successfully adapted for FIA, the peak height being proportional to the cadmium concentration over the range 0.1-3 mug/ml; a two-channel manifold is used and an improvement in selectivity is obtained. The use of a gradient tube is demonstrated to give a good calibration for Cd(II) over the range 2 x 10(-2) -2 x 10(-6)M.     

Preconcentration and flame atomic absorption spectrometry determination of cadmium in mussels by an on-line continuous precipitation-dissolution flow system

A rapid, sensitive, accurate and precise flame atomic absorption method is described for the determination of cadmium in mussels. The method is based on the continuous precipitation of cadmium as an ion pair between tetraiodocadmate and quinine and dissolution of the precipitate with ethanol. The metal can be preconcentrated 32-fold using 15 ml of sample solution by using a time-based technique at a sampling flow rate of 3.0 ml min(-1). The proposed method allows the determination of cadmium in the range 0.25-5.5 mug g(-1). The precision (relative standard deviation) obtained for different amounts of cadmium is in the range 1.5-4.7% at the 0.25-5.0 mug g(-1) level. The method demonstrates high tolerance to interferences, and the data obtained are in agreement with the certified value of a selected reference material. This procedure was applied to the determination of cadmium in mussel samples from estuaries in Galicia (Spain).     

Extraction-fluorimetric determination of microgram amounts of thallium with 2-phenylbenzo[8,9]quinolizino[4,5,6,7-fed]phenanthridinylium perchlorate

In 0.5 M hydrochloric acid medium, thallium(III) forms with 2-phenylbenzo [8,9]quinolizino[4,5,6,7-fed]phenanthridinylium perchlorate (PQPP) an ion-association compound which is extractable in isoamyl acetate. The extracted ion-pair has a mole ratio Tl/PQPP in 1:1 and has been used for the spectrofluorimetric determination of thallium in the concentration range 0.06–1.6 μg per 5 ml of organic layer. The interference of a large number of foreign ions has been investigated. The method is sensitive, accurate, precise, and specially useful for the determination of thallium in different materials with low contents of this element.     

Extraction and spectrophotometric determination of thallium(III) with thiothenoyltrifluoroacetone

A procedure is described for the extractive photometric determination of thallium(III) with thiothenoyltrifluoroacetone in carbon tetrachloride. Thallium(III) is extracted quantitatively at pH 4-5 and the bright yellow extract obeys Beer's law over the Tl(III) concentration range 2.5-17.5 mug/ml, at 440 nm. Thallium(III) can be determined in the presence of a large number of cations and anions.     

Piezoelectric detection of ion pairs between sulphonate and catecholamines for flow injection analysis of pharmaceutical preparations

Fundamentals of ion-pair flow injection with piezoelectric detection were investigated experimentally and theoretically for the adsorption of dodecyl phenylsulfonate and interfacial ion-pair formation with epinephrine and l-dopa on silver electrode of quartz crystal microbalance. The influences of sulfonate concentration and operating parameters on the frequency response were demonstrated and provided the possibility for the discriminating determination of mixtures. The selected system of ion-pair flow injection with piezoelectric detection was applied to the determination of epinephrine and l-dopa. Calibration curves were linear in ranges 4.00-850 and 3.50-730 mug ml(-1), with detection limits of 1.22 and 1.05 mug ml(-1) and sampling frequencies of 120 samples h(-1), for epinephrine and l-dopa, respectively. The method has been satisfactorily applied to the determination of catecholamines in pharmaceutical preparations.     

Spectrophotometric determination of isoproturon using p-aminoacetophenone and its application in environmental and biological samples

A simple and sensitive method for the determination of isoproturon, a widely used herbicide is described here which is based on alkaline hydrolysis of isoproturon to its corresponding primary amine followed by diazotization and coupling with p-aminoacetophenone in alkaline medium. The absorption maxima of the coloured compound formed is measured at 525 nm. Beer's law is obeyed over the concentration range of 0.5-5.0 mug in a final solution volume of 25 ml (0.02-0.2 ppm). The molar absorptivity and Sandell's sensitivity were found to be 8.6x10(5) l mol(-1) cm(-1) and 0.0002 mug cm(-2), respectively. The method has been satisfactorily applied to the determination of isoproturon in environmental and biological samples.     

A simple simultaneous flow injection method based on phosphomolybdenum chemistry for nitrate and nitrite determinations in water and fish samples

A direct spectrophotometric flow injection method for the simultaneous determination of nitrite and nitrate has been developed. The method is based on the oxidation of a phosphomolybdenum blue complex by the addition of nitrite and the decrease in absorbance of the blue complex is monitored at 820 nm. The injected sample is split into two segments. One of the streams was directly reacted with the above reagent and detected as nitrite. The other stream was passed through a copperised cadmium reductor column where reduction of nitrate to nitrite occurs, and the sample was then mixed with the reagent and passed through the cell of the spectrophotometer to be detected as nitrite plus nitrate. The conditions for the flow injection manifold parameters were optimised by experimental design and the concentration of nitrite and nitrate was determined in the linear range from 0.05 to 1.15 mug ml(-1) nitrite and 0.06 to 1.6 mug ml(-1) nitrate with a detection limit of 0.01 mug ml(-1) for nitrite and 0.025 mug ml(-1) for nitrate. The method is suitable for the simultaneous determination of nitrite and nitrate in fish and water samples with a sampling rate of 25+/-2 sample per hour.     

Determination of indium and thallium by hydride generation and atomic-absorption spectrometry

Hydride generation coupled with atomic-absorption spectrometry was applied to the determination of indium and thallium. The hydrides were generated in 1M HCl (In) and 1-1.5M HCl or HNO(3) (Tl) with 1% NaBH(4) solution, and were flushed with argon into an electrically heated silica tube. The characteristic mass for indium and thallium were 0.13 and 0.12 mug, respectively.     

Determination of the plant growth regulator beta-naphthoxyacetic acid by micellar-stabilized room temperature phosphorescence

This paper presents a method for the determination of the plant growth regulator beta-naphthoxyacetic acid (NOA) by micellar-stabilized room temperature phosphorescence with the surfactant Triton X-100 (TX-100) as the micellar medium, thallium nitrate as the heavy atom and sodium sulphite as the oxygen scavenger. A multivariate optimization approach using the blocked cube star design of central composite was carried out. The analytical curve of NOA gives a linear dynamic range of 0.4-3.0 mug ml(-1) and a detection limit of 0.13 mug ml(-1). A recovery of 93.6% was obtained for 1 mug ml(-1) NOA in spiked apple samples.     

Determination of Lead and Cadmium at Silver Electrode by Subtractive Anodic Stripping Voltammetry in Plant Materials Containing Tl

Lead and cadmium have been determined by the subtractive anodic stripping voltammetry using the square‐wave mode at a silver electrode without removal of oxygen. The samples containing large amount of thallium were collected from a highly contaminated region. The presence of thallium strongly affects the peak shape of Cd. The plant material digestion was performed with HNO₃/HClO₄ mixture using pressurised microwave decomposition. The proposed method used for the lead determination was validated by the inter‐method comparison (ICP‐MS). The cadmium determination was validated using certified reference material. The results obtained, supported by statistical tests, demonstrated the usefulness of the method for the lead determination in samples containing large amounts of Cd and Tl. It is important to note that Cd can only be quantified when the thallium concentration is much lower than that of cadmium.     

A sensitive spectrophotometric method for the determination of methyl alcohol in air and water

A sensitive spectrophotometric method for the indirect determination of methyl alcohol in air and water is described. The methyl alcohol is oxidized to formaldehyde which is then determined in acidic medium with p-aminoazobenzene and sulphur dioxide. Beer's law is obeyed in the range 100-600 mug of methyl alcohol in 25 ml of final solution and the wavelength of maximum absorption is 505 nm. The lower limit of determination is 5 mug ml in the sample. Several common organic co-pollutants do not interfere. The method can be used for determination of methyl alcohol in blood.     

Column preconcentration of titanium in aluminium and zinc alloys with oxalic acid-ascorbic acid and the ion-pair of sodium 1,2-dihydroxybenzene-3,5-disulphonic acid and tetradecyldimethylbenzylammonium chloride supported on naphthalene using spectrometry

A solid ion-pair compound produced from sodium 1,2-dihydroxybenzene-3,5-disulphonic acid (Tiron) and tetradecyldimethylbenzylammonium chloride(TDBA) supported on naphthalene in a simple glass-tipped funnel tube provides a simple adsorbent system for preconcentrating titanium from some alloys. Titanium reacts with Tiron to form a water-soluble coloured chelate anion which in turn forms a water-insoluble stable titanium/Tiron/TDBA complex with the ion-pair on the surface of naphthalene packed in a column. Titanium is quantitatively retained on the naphthalene in the presence of L-ascorbic acid and oxalic acid in the pH range 3.0-4.5 and at a flow-rate of 1 mil/min. The metal complex and naphthalene were dissolved from the column with 5 ml of dimethylformamide(DMF), and the absorbance of the solution was measured at 398 nm. A calibration graph was linear over the range 1-18 mug of titanium in 5 ml of the final DMF solution. The complex has a molar absorptivity of 1.39 x 10(4) l.mole(-1).cm(-1) and a sensitivity of 3.44 x 10(-3) mug/cm(2) for 0.001 absorbance. Eight replicate determinations for a sample containing 12 mug of titanium gave a mean absorbance of 0.697 with a relative standard deviation of 0.82%. The interference of various ions was studied and optimum conditions were developed for the determination of titanium in various aluminium and zinc alloys.     

Triton X-100存在下镉试剂分光光度法测定痕量铊(III)

本文首次提出了在Triton X-100存在下, 以镉试剂作显色剂于水相直接分光光度法测定了痕量铊, 结果表明: 该体系具有很高的灵敏度, 是目前分光光度法测定铊的最灵敏方法之一.     

Determination of cadmium, lead, and nickel by simultaneous multielement flame atomic absorption spectrometry in burned and unburned Venezuelan crude oil

This work describes the use of simultaneous multielement flame atomic absorption spectrometry for the determination of cadmium, lead, and nickel in burned and unburned Venezuelan crude oil (5 ml volumes) in controlled laboratory experiments. The simultaneous detection limits were 0.010 mug ml(-1) (Cd), 0.04 mug ml(-1) (Pb), and 0.40 mug ml(-1) (Ni) with precision's of these elements at concentrations of 10x above these detections limits, and in the crude oil, of 1-2%. Loss of elemental concentrations in the crude oil in a 3-5 ml volume when burned were 4% (Cd), 50% (Pb), and 22% (Ni). These results suggest that the form of the elements and the temperature attained in the burning crude oil effect the removal of the elements. The type of surface affected the volume of oil removed. Soil gave a 15% and a smooth surface almost 50% volume reduction.     

Spectrophotometric determination of zinc with hydrazidazol in the presence of Triton X-100 and its application in metal analysis

A new spectrophotometric method for the determination of zinc is proposed. The chromogenic agent Hydrazidazol forms a 1:1 chelate with zinc in the presence of Triton X-100 in a medium containing 20-40% ethanol. The molar absorptivity and conditional formation constant have been found to be 2.7 x 1O(4) l.mole(-1).cm(-1) (at 640 nm) and 10(5.32) respectively. Beer's law is obeyed for zinc over the range of 0.2-0.8 mug/ml with a standard deviation of 0.024 mug/ml. The method can be applied to the determination of zinc in cadmium metal and its oxide after preconcentration by selective extraction of zinc thiocyanate into ethyl acetate in the presence of EDTA and thiosulphate as masking agents.     

Spectrophotometric determination of micro amounts of cadmium in waste water with cadion and triton X-100

A spectrophotometric method for determination of micro amounts of cadmium in waste water with Cadion and Triton X-100 is described. The interference of foreign ions can be eliminated by masking with an ascorbic acid-Rochelle salt-potassium cyanide-potassium fluoride mixture. After demasking with formalin, cadmium is determined directly in aqueous solution without separation. Beer's law is obeyed for 0-8 mug of Cd in 25 ml of solution. The method is more sensitive than the dithizone method, its apparent molar absorptivity at 480 nm being 1.19 x 10(5) 1. mole(-1). cm(-1). Results obtained by using the proposed method on waste water samples agree well with those obtained by atomic-absorption spectrophotometry.     

Bioanalysis of the neuropeptide des-enkephalin-gamma-endorphin by high-performance liquid chromatography with on-line sample pretreatment using gel permeation and solid-phase isolation.

A bioanalytical method is described that allows the determination of a number of beta-endorphin-related peptides. The method is based on the application of fluorescence detection after high-performance liquid chromatography followed by post-column derivatization with o-phthaldialdehyde. Concentrations exceeding 10-25 ng/ml could be determined by using conventional fluorescence detection, whereas lower concentrations demand the use of laser-induced fluorescence detection. The sample pretreatment includes the use of on-line gel permeation, on-line solid-phase isolation and heart cutting of a peak from reversed-phase gradient elution. The sample pretreatment procedure does not discriminate between the dodecapeptide des-enkaphalin-gamma-endorphin (DE gamma E) and its metabolites in order to obtain similar recoveries for all components. The final chromatographic phase system is based on ion-pair formation, which permits the separation of DE gamma E from its metabolites and degradation products. The optimized procedure allows the determination of these peptides in plasma at concentration levels down to about 1 ng/ml, demanding a sample volume of 1 ml.     

Selective preconcentration of thallium on modified silica gel for its determination by flame emission and absorption spectrometry

Thallium (0.02-20 mug) was successfully preconcentrated on silica gel C18 from 0.1M hydrochloric acid in the presence of various cationic surfactants as ion pairs with tetrachlorothallate(III), and subsequently eluted with 96% ethanol. Of various atomic spectrometric procedures considered, emission spectrometry in a nitrous oxide-acetylene flame is suitable for the final determination of thallium in plants, this is more sensitive for thallium than flame atomic absorption spectrometry.     

Flame AAS determination of thallium in soils

The anion-exchange enrichment of TlCl(-)(4) coupled to flame AAS is applied to the determination of the total, pseudo-total (not bound in the silicate matrix) and mobile (plant available) content of thallium in soils. Ascorbic acid is used as a new efficient eluent of thallium. The limit of detection of the method is 0.04,mug/g, the relative standard deviation at the 1 mug/g level is about 3%. The method is rapid and simple.