Determination of cadmium by suction-flow liquid-liquid extraction combined with inductively-coupled plasma atomic emission spectrometry

The flow manifold described permits suction-flow liquid-liquid extraction of cadmium in a discrete aqueous sample as its diethyldithiocarbamate into carbon tetrachloride. The organic extract is fed into the nebulizer of an inductively-coupled plasma atomic emission spectrometer by a peristatic pump. An increase in sensitivity of ca. 250-fold is achieved in comparison with direct aspiration of the aqueous solution. The sampling frequency is 20 h^?1 and the consumption of carbon tetrachloride and 5% (w/v) sodium diethyldithiocarbamate solution are each 0.6 ml min^?1. The 3σ detection limit is 0.4 ng ml^?1 cadmium, and the calibration is linear up to 300 ng ml^?1. The relative standard deviation for 10 replicate measurements is 1.5% for 50 ng ml^?1 cadmium. The flow interferences observed can be decreased or eliminated by the addition of citrate to the buffer solution. Results of analysis of some certified biological reference materials are given.     

Determination of traces of gallium in the presence of aluminium by synchronous derivative spectrofluorimetry

Gallium (2–100 ng ml^?1) is determined in the presence of ?500-fold amounts (by weight) of aluminium by using synchronous first- or second-derivative spectrofluorimetry. The fluorescence of the gallium chelate with 1-(2-pyridylazo)-2-naphthol is greatly enhanced compared to that of the aluminium chelate in micellar sodium dodecyl sulphate solutions. The limit of detection is about 0.6 ng ml^?1.     

Determination of copper in natural waters by atom-trapping atomic absorpton spectrometry after liquid/liquid extraction

Copper (1–100 ng ml^?1) is determined in natural waters by atom-trapping atomic absorption spectrometry after extraction of its 1-pyrrolidinecarbodithioate complex into isobutylmethylketone. Results are in good agreement with those obtained by conventional carbon-furnace atomic absorption spectrometry.     

Polarography of disodium pentacyanonitrosylferrate(II): Part 2. Determination at Therapeutic Levels in Serum,Plasma, and Whole Blood

Disodium pentacyanonitrosylferrat(II) (sodium nitroprusside) is determined at therapeutic (ng ml^?1) levels in plasma, serum and blood with conventional and high-performance differential pulse polarography (d.p.p. and h.p.d.p.p.) at a dropping mercury electrode or a static mercury drop electrode. Serum or plasma (3 ml) is treated with perchloric acid containing 1 mg ml^?1 potassium hexacyanoferrate(II), centrifuged for 10 min and subjected to polarography. For spiked serum, calibration graphs are linear over the range 30–1000 ng ml^?1 sodium nitroprusside, regardless of the polarographic technique; the estimated detection limit is 15 ng ml^?1 (5 × 10^?8 M). Calculated therapeutic levels range from 100 to 1000 ng ml^?1. Similar results were obtained for spiked plasma. A similar procedure is suitable for whole blood and was used to study the in-vitro degradation of sodium nitroprusside (200 ng ml^?1) on incubation at 37°C. The in-vitro loss is rapid (t_{$\text{1}\text{2}$} ≈ 6 min) but meaningful in-vivo levels can be obtained when the blood is collected in a 0.9% sodium chloride solution at 0°C. Thiocyanate, the main metabolite of nitroprusside, and thiosulphate, which is a potential antidote for cyanide, do not interfere.     

Determination of prednisolone and prednisone in plasma by liquid chromatography with fluorescence detection

After a single-step extraction from plasma (250 μl) with dichloromethane, the drugs and dexamethasone (internal standard) are oxidized by copper(II) acetate to the corresponding glyoxal and converted into the fluorescent quinoxalines by reaction with 1,2-diamino-4,5-methylenedioxybenzene. The quinoxalines are separated within 55 min by reversed-phase liquid chromatography with isocratic elution. The detection limits for prednisolone and prednisone added to plasma are 3 ng ml^?1 in plasma (signal-to-noise ratio=3).     

Indirect atomic absorption spectrometric determination of perchlorate by liquid-liquid extraction in a flow-injection system

The determination is based on the continuous liquid-liquid extraction of the copper(I)/6-methylpicolinealdehyde azine/perchlorate ion-pair into 4-methyl-2-pentanone in a flow-injection manifold. The organic fills a loop of an injector situated in an integrated feed system of an atomic absorption spectrometer. Measurement of the copper atomic absorption signal from the organic phase allows the indirect determination of 0.5–5 μg ml^?1 perchlorate, giving a 3-fold increase in sensitivity over the conventional spectrophotometric method. The detection limit is 70 ng ml^?1. The sampling frequency is 45 ± 5 h^?1. The method is highly selective, and has been used for the determination of perchlorate added to serum and urine samples.     

Flame atomic absorption spectrometric determination of Cd(II), Ni(II), Co(II) and Cu(II) in tea and water samples after simultaneous preconentration of dithizone loaded on naphthalene

A simultaneous preconcentration procedure for the determination of Cd(II), Ni(II), Co(II) and Cu(II) by atomic absorption spectrometry is described. The method is based on solid phase extraction of the metal ions on dithizone loaded on naphthalene in a mini-column, elution with nitric acid and determination by flame atomic absorption spectrometry. The sorption conditions including NaOH concentration, sample volume and the amount of dithizone were optimized in order to attain the highest sensitivity. The calibration graph was linear in the range of 0.5–75.0 ng ml^?1 for Cd(II), 1.0–150.0 ng ml^?1 for Ni(II), 1.0–150.0 ng ml^?1 for Co(II) and 1.0–125.0 ng ml^?1 for Cu(II) in the initial solution. The limit of detection based on 3S_b was 0.13, 0.32, 0.33 and 0.43 ng ml^?1 for Cd(II), Ni(II), Co(II) and Cu(II), respectively. The relative standard deviations (R.S.D) for ten replicate measurements of 20 ng ml^?1of Cd(II), 100 ng ml^?1 of Ni(II), Co(II) and 75 ng ml^?1 of Cu(II) were 3.46, 2.43, 2.45 and 3.26%, respectively. The method was applied to the determination of Cd(II), Ni(II), Co(II) and Cu(II) in black tea, tap and river water samples.     

Determination of trace concentrations of antimony by the introduction of stibine into an inductively-coupled plasma for atomic emission spectrometry

A simple, rapid and sensitive method is described for the determination of trace concentrations of antimony by inductively-coupled plasma atomic emission spectrometry with hydride generation. Hydrochloric acid (1 M) is the best medium for stibine generation, but antimony(III) is also effectively reduced to stibine in 1 M malic acid or 0.5 M tartaric acid, whereas antimony(V) gives no significant signal in either of these acids. This permits the differential determination of Sb(III) and Sb(V). Most of the inter-element interference effects can be minimized by thiourea, bur standard additions are recommended for accurate determinations. Thiourea is also effective in prereducing Sb(V) to Sb(III). The detection limit is 0.19 ng Sb ml^?1 and the calibration graph is linear up to 100 μg ml^?1. The r.s.d, at 1 and 100 ng Sb ml^?1 are 3.8 and 2.1%, respectively. The method is applied to copper metal and to speciation of antimony in waste water.     

Fluorimetric determination of calcium by ion-pair extraction with cryptand 2.2.1 and eosin

A fluorimetric study on the extraction of calcium into 1,2-dichloroethane as an ion-pair, formed between the cryptand 2.2.1-calcium complex and the eosinate anion, is described. Optimum conditions for extraction are established and a new fluorimetric determination of ultratraces of calcium is proposed. A linear working range from 1.5 ng ml^–1 (detection limit) to 100 ng ml^–1 of calcium and a relative standard deviation of ± 2.9% at the 70 ng ml^–1 level are obtained. The equilibrium constants involved in the extraction process have been calculated and refined by the Letagrop-DISTR program. The proposed method has been tested for the direct determination of calcium in sugars.     

Simultaneous determination of copper and lead by graphite-furnace atomic absorption spectrometry after liquid-liquid extraction of the ion pair with zephiramine

A procedure for the simultaneous determination of copper and lead by graphite-furnace atomic absorption spectrometry was investigated by means of a two-channel atomic absorption spectrometer. Both copper(II) and lead(II) are converted into their iodo complex anions and extracted quantitatively into diisobutyl ketone as their ion pairs with tetradecyldimethylbenzylammonium (zephiramine) in a 10-ml centrifuge tube. An aliquot of the organic extract is directly pipetted from the upper layer in the centrifuge tube and injected into the graphite furnace. The detection limits (S/N = 3) are 2.6 ng ml^?1 of copper and 1.0 ng ml^?1 of lead. The relative standard deviations for 10 replicate determinations are 2.9% for 20 ng ml^?1 of copper and 2.7% for 10 ng ml^?1 of lead. Results of analyses of some practical samples are given.     

Determination of urinary chromium levels for healthy men and diabetic patients by electrothermal atomic absorption spectrometry

Urinary chromium levels for healthy and diabetic men were determined by direct graphite-furnance atomic absorption spectrometry. The average values were 0.72 ± 0.31 ng ml^?1 for 23 healthy men aged 23 to 35, 0.39 ± 0.19 ng ml^?1 for 19 healthy men aged 47 to 69, and 1.0 ± 0.9 ng ml^?1 for 23 diabetic patients aged 13 to 79. Some urines of diabetic patients exhibit values > 1.3 ng ml^?1, which are never found in healthy men. The proposed method involves direct injection of 20 μl of urine inot a pyrolytically-coated graphite tube, and a standard addition calibration procedure involving a pooled urine sample. The results are compared with those obtained by a liquid-liquid extraction method.     

Sensitive spectrophotometric kinetic determination of osmium by catalysis of the pyrogallol red-bromate reaction

Osmium(VIII) is determined by means of its catalytic effect on the oxidation of pyrogallol red (PGR) by potassium bromate at pH 6.0, 30°C and 545 nm. The decrease in absorbance of PGR (2.5 × 10^?5 M) in the presence of KBrO₃ (0.20 M) over a period of 0–150 s is proportional to the concentration of osmium(VIII) over the range 0–1400 ng ml^?1. The limit of detection of osmium was 0.65 ng ml^?1. The precision and accuracy of the method are described. The effects of the presence of 45 cations and anions on osmium determination were studied. The effects of probable interferences were completely removed by a single extraction of osmium as osmium tetraoxide into isobutyl methyl ketone and back-extraction into sodium hydroxide solution.     

Direct determination of biacetyl in fats by sensitized room temperature phosphorescence

A direct method for the determination of biacetyl in butter and margarine by sensitized room temperature phosphorescence (SRTP) is described. After dissolution of the sample in hexane, biacetyl is isolated by distillation, and its native phosphorescence is sensitized by a non-polar linear furocoumarin, 4′5′-dihydro-3-carbethoxypsoralen. The limit of detection is 0.05 ng ml^?1 biacetyl, with a linear response from 1 × 10^?4 to 1 μg ml^?1 (r = 0.999). The RSD is 3.5% at 100 ng ml^?1.     

A modified method for the determination of lead in zircons by differential-pulse anodic stripping voltammetry

Zircons (20–100 mg) are decomposed within 1 h by fusion with potassium hydrogenfluoride followed by fuming with sulphuric acid. With differential-pulse anodic stripping voltammetry, after deposition for 1 min, the limit of detection for lead is 2 ng ml^?1 and the limit of quantitation is 6.6 ng ml^?1. Results (7–247 mg kg^?1 lead) are reported for nine zircons.     

Fluorogenic reaction between adenine derivatives and chloroacetaldehyde and its application to the determination of 9-(2-chloro-6-fluorobenzyl)adenine in human plasma

A sensitive (1 ng ml^?1) liquid chromatographic method with fluorescence detection is described for the determination of arprinocid and analogous compounds in human plasma. The method is based on chemical derivatization with chloroacetaldehyde to form highly fluorescent derivatives. Extraction of the drug from plasma and separation of the derivative from the reaction mixture are accomplished by solid-phase extraction with two silica cartridges. The effects of pH, solvent, and concentration of the reagents on the efficiency of derivatization were studied. The assay in plasma was validated in the 1–50 ng ml^?1 range. The fluorescent derivatives were synthesized and fully characterized. The derivatives were also found to be efficient as energy acceptors in the oxalate ester/hydrogen peroxide chemiluminescent system.     

Cloud point extraction and spectrophotometric determination of amaranth in food samples using nonionic surfactant Triton X-100 and tetrabutylammonium hydrogen sulfate

Cloud point extraction methodology was successfully employed for preconcentration of trace amounts of amaranth prior to its determination by spectrophotometry. The method was based on the extraction of amaranth as an ion pair with tetrabutylammonium ion from aqueous solution using Triton X-100 as non-ionic surfactant. The extracted surfactant rich phase was diluted with ethanol and its absorbance was measured at 518 nm by a spectophotometer. An optimum set of surfactant concentration, pH, equilibration temperature and time, tetrabutylammonium hydrogen sulfate and salt concentration were obtained. The calibration graph was linear in the range of 20–1600 ng ml^?1 of amaranth in the initial solution with r = 0.9993 (n = 12). Detection limit based on three times the standard deviation of the blank (3S_b) was 13.0 ng ml^?1 (n = 10), and the relative standard deviation (R.S.D) for 100 and 1000 ng ml^?1 of amaranth was 4.2 and 1.4% (n = 10), respectively. The proposed procedure was applied to the determination of amaranth in different food samples.     

Kinetic-Spectrophotometric Determination of Traces of Osmium by Its Catalytic Effect on the Oxidation of Pyrogallol Red by Hydrogen Peroxide

Abstract

A Kinetic-spectrophotometric method for the determination of ultra-trace amounts of osmium(VIII) is described. It is based on the catalytic action of osmium(VIII) on the oxidation of pyrogallol red with hydrogen peroxide, yielding a colorless product in neutral medium. The reaction is followed spectrophotometrically by measuring the rate of change in absorbance at 540 nm and 30°C. Os(VIII) in the range 0.005 -100 ng.ml^?1 can be determined. The proposed method is hardly subject to interferences. The relative standard deviation is 1.5% for 1 ng.ml^?1 of Os(VIII). The kinetic parameters of the catalyzed and uncatalyzed reactions are reported. The detection limit is 1 pg.ml^?1.     

Cloud point extraction and spectrophotometric determination of codeine in pharmaceutical and biological samples

Cloud point extraction process using non-ionic surfactant, Triton X-114, to extract codeine from aqueous solution was investigated. The method was based on the extraction of codeine and bromothymol blue from acetate buffer media to surfactantrich phase and formed a charge transfer-ion pair complex. The extracted surfactant-rich phase was diluted with ethanol and its absorbance was measured at 430 nm. The effect of different variables such as pH, Triton X-114 concentration, cloud point temperature and time was established. The calibration graph was linear in a wide range of 100–700 ng ml^?1 of codeine with r = 0.998 (n = 7). The detection limit based on three times standard deviation of the blank (3s) was 4.6 ng ml^?1 and relative standard deviation (R.S.D) is 2.15% for 500 ng ml^?1 codeine (n = 5). The proposed method was applied to the determination of codeine in acetaminophen codeine tablets and blood samples.     

Determination of vanadium and titanium in steel by inductively coupled plasma atomic emission spectrometry with modified use of a tungsten boat furnace atomizer for atomic absorption spectrometry

For electrothermal sample introduction, a commercially available tungsten boat atomizer for atomic absorption spectrometry (AAS) was transferred to a vaporizer for inductively coupled plasma atomic emission spectrometry (ICP-AES). The modification retained as much of the original design of the atomizer as possible, so that the apparatus could be switched easily between conventional tungsten boat furnace (TBF)-AAS and TBF-ICP-AES. By using this system, a procedure for the determination of vanadium and titanium in steel was investigated. The detection limits (S/N=3) of vanadium and titanium were 3.9 and 1.5 ng ml^?1, respectively. The relative standard deviations for five replicate determinations were ca. 3% for both elements. The calibration graphs were linear up to 100 μg ml^?1 vanadium(V) and 10 μg ml^?1 titanium(IV). Results of analyses of some low-alloy steel samples are given.     

Determination of tin in the ng g−1 range differential pulse polarography

A sensitive determination method of tin by differential pulse polarography is described. Addition of tropolone to acetate supporting electrolyte at about pH 4.7 provides a 30-fold signal enhancement, giving a sensitivity comparable to that obtained in anodic stripping voltammetry, but without the need for enrichment by pre-electrolysis. The response is linear over more than three orders of magnitude (1 ng ml^?1?5 μg ml^?1 Sn), allowing measurements within a wide concentration range without changes in sample preparation or measuring conditions. Large amuonts of Ti, W, Cr or Mo interfere, but can be removed completely by pre-separation of tin based on extraction with tropolone/toluene and back-extraction into the supporting electrolyte. Results for tin in water and fruit juice are consistent with those obtained by other techniques.