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.     

Fluorimetric determination of chromium at low levels with 3-hydroxyflavone and application of the method to steels

The method is based on a 1:1 Cr(VI)/3-hydroxyflavone complex which is extracted into benzene at H_o = ?0.6. The complex has a pK^* value of 7.8 ± 0.1. Chromium is determined in the range 10–650 ng ml^?1 with excitation at 358 nm and emission measurement at 530 nm. The relative standard deviation is 6.1% for 332 ng ml^?1 chromium (n = 10). The method is applied to the determination of chromium in steels.     

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.     

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.     

The double radio-isotope derivative technique for the assay of drugs in biological material: Part II. The simultaneous determination of opipramol and its deshydroxyethyl metabolite

The neuroleptic drug opipramol and its deshydroxyethyl metabolite can be determined simultaneously in the same biological sample. Known amounts of ¹⁴C-labelled opipramol and ¹⁴C-labelled metabolite are added to the sample to serve as internal standards. After suitable extraction, both compounds are acetylated by ³H-labelled acetic anhydride. Together with μg-amounts of carrier compounds, the O-acetyl derivative of opipramol and the N-acetyl derivative of the metabolite are purified and separated by two-dimensional thin-layer chromatography. Each of the derivatives is isolated and counted for ¹⁴C-and ³H-activity. The ¹⁴C-activities recovered serve to determine the overall yield of the opipramol and metabolite, and to convert the measured ³H-activity to 100 % theoretical yield. From analyses of standard samples, the specific ³H-activities of the acetyl derivatives were calculated, and these values were used to convert the measured ³H-activities from biological samples to concentrations of original opipramol and metabolite. For both compounds the standard deviations of blank samples were ±1 ng ml^?1. For concentrations up to 100 ng ml^?1 the standard deviation was ±3 ng ml^?1.     

Determination of trace amounts of nickel by differential pulse adsorptive cathodic stripping voltammetry using calconcarboxylic acid as a chelating agent

A method for the determination of nickel(II) by stripping voltammetry is described. The method is based on the adsorptive accumulation of nickel(II) calconcarboxylic acid complex onto a hanging mercury drop electrode (HMDE), followed by the reduction of the adsorbed complex using differential pulse voltammetry. The optimum operating conditions and parameters were found to be 0.05 M NH₃/NH₄Cl buffer (pH = 9.5) as the supporting electrolyte, a ligand concentration of 1 × 10^?6 M, accumulation potential of ?0.5 V (vs. Ag/AgCl) and accumulation time of 60 s. At the optimized conditions, the peak current is proportional to the concentration of nickel in the range of 1.7 × 10^?9 to 4.7 × 10^?7 M (0.1–28 ng ml^?1) with a detection limit of 0.05 ng ml^?1. The relative standard deviation (n = 10) at nickel concentrations of 2, 10 and 15 ng ml^?1 varies in the range 0.76 to 2.1%. Possible interferences by metal ions, which are of great significance in real matrices, have been studied. The method was successfully applied to the determination of nickel content in a chocolate sample.     

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.     

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.     

Square-wave cathodic adsorptive stripping voltammetric determination of trace amounts of 2-mercaptobenzimidazole in water samples

A sensitive, simple and reproducible square-wave cathodic adsorptive stripping voltammetric method is developed for the determination of 2-mercaptobenzimidazole (MBIM) in different water samples using a static mercury drop electrode (SMDE) as a working electrode. The solution conditions and instrumental parameters were optimized for the determination of MBIM by square-wave cathodic adsorptive stripping voltammetry. This method is based on a sensitive adsorptive reduction peak of the MBIM at ?0.532 V vs. Ag/AgCl reference electrode in a Britton-Robinson buffer at pH 10.0. The linear concentration range was 20–600 ng ml^?1 when using 0.0 V as the accumulation potential. The detection limit of the method was calculated to be 8.41 ng ml^?1. The precision was excellent with relative standard deviations (n = 20) of 2.30%, 1.71%, 2.25% and 1.33% at MBIM concentrations of 40, 90, 200 and 500 ng ml^?1, respectively. The proposed voltammetric method is used for the determination of MBIM in different spiked water samples.     

Indirect flow-injection determination of methadone by atomic absorption spectrometry

A simple continuous redox flow system coupled on-line with an atomic absorption spectrometer for the determination of methadone at the ng ml^?1 level is described. It is based on the reduction of the keto group of the analyte in a camium or zinc microcolumn and determination of the metal ions formed. The drug can be determined in the range 5–50 ng ml^?1 with a relative standard deviation between 1.8 and 2.5% at a sampling frequency of 150 h^?1. The selectivity of the method allows the analyte to be determined in the presence of other drugs.     

Inductively-coupled plasma atomic emission spectrometric determination of boron based on generation of methyl borate

Boron is converted to methyl borate, distilled and condensed, and selectively volatilized at 50°C into the plasma without interference from methanol, which quenches the plasma. The 3σ detection limit is 40 ng ml^?1 boron, the calibration graph is linear up to 10 μg ml^?1 and the r.s.d. 3.0% for 2.0 μg ml^?1 (n = 10). Boron is determined in plant-tissue and steel standards.     

2-(α-pyridyl)thioquinaldinamide: a novel fluorimetric reagent in inorganic trace analysis. : Part 2. A simple selective determination of selenium(IV) at Ultratrace Levels

The very sensitive fluorimetric determination of selenium(IV) is based on its oxidation of the non-fluorescent 2-(α-pyridyl)thioquinaldinamide in slightly acidic solution (0.05–0.15 M sulphuric acid). The excitation and emission wavelengths are 350 nm and 500 nm, respectively. Linear calibration graphs are obtained for different ranges of selenium concentration between 0.01 ng ml^?1 and 0.5 μg ml^?1. Over sixty ions either do not interfere or can be masked in the determination of 1 ng ml^?1 Se(IV). The method is applied successfully to various synthetic mixtures and to a native sulphur sample. The reaction is fast and the fluorescent system is stable for 24 hours.     

A New Generic Enzyme Immunoassay for Sulfonamides

Abstract

The study was directed to the development of generic immunoenzyme assay for sulfonamides. N‐sulfanil‐4‐aminobutyric acid which mimics the common part of sulfonamides was used as immunogenic hapten. The obtained rabbit polyclonal antibodies allowed detection of the N‐sulfanil‐4‐aminobutyric acid in indirect competitive immunoenzyme assay down to 0.03 ng ml^?1. The lowest detection limit for the sulfonamides tested, 0.1 ng ml^?1, was observed for sulfamethoxypyridazine. Eleven other sulfonamides could be determined at concentrations ranging from 1–37 ng ml^?1. Thus, the proposed technique can be used in class‐specific sulfonamides detection in products of animal origin.     

Determination of polyamines in human plasma by high‐performance liquid chromatography coupled with Q‐TOF mass spectrometry

A high‐performance liquid chromatography coupled with Q‐time of flight mass spectrometry (HPLC/Q‐TOF MS) method was developed and validated for the determination of 1, 3‐diaminopropane, putrescine, cadaverine, spermidine and spermine in human plasma. The plasma samples were first pretreated by 10% HClO₄ and then derived by benzoyl chloride with 1, 6‐diaminohexane as internal standard. The derived polyamines were separated on a C₁₈ column using a gradient program. The detection was performed on a Q‐TOF MS by positive ionization mode. Calibration curve for each polyamine was obtained in the concentration range of 0.4 ~ 200.0 ng ? ml^?1, with limit of detection of 0.02 ~ 0.1 ng ? ml^?1. The intra‐ and inter‐day RSD for all polyamines were 2.5–14.0% and 2.9 ~ 13.4%, respectively. The method was applied to determine the polyamines in human plasma from cancer patients and healthy volunteers. Results showed that the mean levels of polyamines in the plasma of cancer patients were higher than that of healthy volunteers, which suggested that the plasma polyamines could be employed as cancer diagnostic indicators in clinical testing. Copyright © 2012 John Wiley & Sons, Ltd.     

Determination of Ultra Trace Amounts of Uranium (VI) by Adsorptive Stripping Voltammetry Using L-3-(3, 4-dihydroxy phenyl) Alanine as a Selective Complexing Agent

Abstract

The spectrophotometric behavior of uranium (VI) with L-3-(3, 4-dihydroxy phenyl) alanine (LDOPA) reagent revealed that the uranium can form a ML₂ complex with LDOPA in solution. Thus a highly sensitive adsorptive stripping voltammetric protocol for measuring of trace uranium, in which the preconcentration was achieved by adsorption of the uranium-LDOPA complex at hanging mercury drop electrode (HMDE), is described. Optimal conditions were found to be a 0.02 M ammonium buffer (pH 9.5) containing 2.0 × 10^?5 M (LDOPA), an accumulation potential of ? 0.1 V (versus Ag/AgCl) and an accumulation time of 120 sec.

The peak current and concentration of uranium accorded with linear relationship in the range of 0.5–300 ng ml^?1. The relative standard deviation (at 10 ng ml^?1) is 3.6% and the detection limit is 0.27 ng ml^?1. The interference of some common ions was studied. Applicability to different real samples is illustrated. The attractive behavior of this reagent holds great promise for routine environmental and industrial monitoring of uranium.     

Alternating current polarographic determination of microgram amounts of iodide ion by means of the catalytic oxidation of 1-amino-2-naphthol-4-sulfonic acid

The catalytic oxidation of 1-amino-2-naphthol-4-sulfonic, acid proceeds quickly with microgram amounts of iodide in the presence of sodium chlorate at pH between 1.3 and 2.0. The oxidation product shows a sensitive tensammetric wave at potentials of about +0.03 V vs. SCE (pH 1.75), so that the catalytic reaction was applied for the determination of microgram amounts of iodide ion. The most suitable conditions of the pH range, the concentration of ANS and sodium chlorate, reaction temperature and standing are 1.3–2.0, 3 × 10^?4M, 0.05 M, 50° C and 1 h respectively. Using the recommended procedure, iodide ion can be determined precisely in the concentration range 0.4–6.5 ng ml^?1 with a relative error of about 3%. Interference of foreign species and the application to the determination of total iodine in river and sea water are described.     

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.     

On-line preconcentration of trace copper for flame atomic absorption spectrometry using a spherical cellulose sorbent with chemically bound quinolin-8-ol

Preconcentration was effected using a 50 mm × 2 mm i.d. minicolumn packed with a spherical cellulose sorbent with chemically bound quinolin-8-ol function groups (Ostorb Oxin). The column was connected to the nebulizer of the atomic absorption spectrometer and the sample solution and eluent (2 M hydrochloric acid) were sucked through it at a flow-rate of 2–3 ml min^?1 by utilizing the negative pressure of the nebulizer. The experimental design was tested with the determination of traces of copper. Peak-area and peak-height measurements were compared. Owing to the simple calibration, the former method was used for quantification. The dynamic range was from 0.3 ng ml^?1 (detection limit) to 5 μg ml^?1 (breakthrough). The reproducibility in the concentration range 25 ng ml^?1-5 μg ml^?1 was better than 5%. Water-soluble inorganic salts, ammonia and sodium hydroxide were analysed. The accuracy of the results was checked by anodic-stripping voltammetry and by electrothermal AAS.     

Indirect determination of fluoride in waters with lanthanum alizarin complexone and inductively-coupled plasma emission spectrometry

Fluoride is determined indirectly by measurement of the La II 333.75-nm line in the lanthanum/alizarin complexone/fluoride complex. The ternary complex is extracted into hexanol containing N,N-diethylaniline and the extract is introduced directly into the plasma. Related to water samples, the detection limit (3σ, concentration factor 5) is 0.59 ng ml^?1 fluoride, calibration is linear up to 1.2 μg ml^?1 and the relative standard deviation for 0.04 μg ml^?1 is 2.6%. Alkali, alkali elements and most anions do not interfere. The method is applied in the analysis of river water, coastal seawater and drinking water.     

Sensitivity enhancement by palladium addition in the electrothermal atomic absorption spectrometry of mercury

In graphite-furnace atomic absorption spectrometry of mercury, addition of 50 μg ml^?1 palladium improves the peak height for 5 μg Hg ml^?1 50 times. Further addition of 20 μg ml^?1 platinum doubles the enhanced peak height. The effect is due to amalgam formation. The best sensitivity is 0.3 ng (1% absorption) and the detection limit is 0.1 ng. The method allows higher ashing temperatures than for solutions without noble metal addition and can be applied to solutions containing substantial amount of organic matter.