Showing papers in "Analyst in 1991"
501 citations
305 citations
214 citations
194 citations
TL;DR: In this paper, an extraction method for the determination of metals in sediment and soil samples using aqua regia[HCl-HNO3(3 + 1)] and a microwave oven is described.
Abstract: A description is given of an extraction method for the determination of metals in sediment and soil samples using aqua regia[HCl—HNO3(3 + 1)] and a microwave oven. The elements Cd, Cr, Cu, Fe, Mn, Pb and Zn were measured in the solutions by means of atomic absorption spectrometry (flame or electrothermal) and inductively coupled plasma atomic emission spectrometry. The results for the analysis of six reference materials after microwave aqua regia extraction showed close agreement with the stated values. A comparison between microwave extraction and conventional reflux extraction for 30 samples showed that the former method gives the same or slightly higher results for the seven elements tested in sediments, soil and suspended matter.
168 citations
130 citations
TL;DR: Copper and zinc were extracted from salicylate solution into Aliquat 336 dissolved in toluene and determined in the organic phase spectrophotometrically using 1-(2-pyridylazo)-2-naphthol and the method permits the determination of copper and zinc in environmental and pharmaceutical samples.
Abstract: Copper and zinc were extracted from salicylate solution into Aliquat 336 dissolved in toluene and determined in the organic phase spectrophotometrically using 1-(2-pyridylazo)-2-naphthol. The determination of copper and zinc was also carried out titrimetrically or by atomic absorption spectrometry after stripping the metal ions from the organic phase. The method permits the determination of copper and zinc in environmental and pharmaceutical samples. The standard deviation and relative standard deviation are 0.052 µg and 0.69%, respectively, for copper and 0.041 µg and 0.60%, respectively, for zinc.
126 citations
TL;DR: In this article, it was shown that the use of a dilute (3.0 × 10−3 mol dm−3) Nc solution in weakly acidic or neutral media makes the determination of total CuI feasible at the 1 × 10 −5 mol Dm −3 level in the presence of up to 0.1 mol Dn−3 CuII, and the latter can be masked by NH3−NH4Cl buffer at pH 10, giving almost the same molar absorptivity for CuI.
Abstract: The existing spectrophotometric method for the determination of total Cu with neocuproine (Nc) does not allow the differentiation of CuI and CuII. It is shown here that the use of a dilute (3.0 × 10–3 mol dm–3) Nc solution in weakly acidic or neutral media makes the determination of CuI feasible at the 1 × 10–5 mol dm–3 level in the presence of up to 0.1 mol dm–3 CuII. For the determination of trace amounts of CuI in the presence of 1 mol dm–3 CuII, the latter can be masked by NH3—NH4Cl buffer at pH 10, giving almost the same molar absorptivity for CuI, i.e., 7.5 × 103 dm3 mol–1 cm–1. The ability to measure the absorption due to CuI in the presence of an excess of CuII was exploited as the basis of an indirect method for the determination of trace amounts of reductants. Superior to the existing individual methods of determination, which are usually specific for a given reducing agent, the proposed system consists of treating the reductant with the CuII–Nc reagent in ammonium acetate buffered media, followed by measurement of the absorbance of the CuI–Nc chelate at 450 nm. The quantification of a given reductant in the concentration range 1 × 10–6–1 × 10–4 mol dm–3 usually takes 3 min with a mean relative standard deviation of 3%. The molar absorptivity of an n-electron reductant which has reacted stoichiometrically is approximately 7.5n× 103 dm3 mol–1 cm–1, i.e., n times that of CuI–Nc. Hence, hydrogen peroxide, ascorbic acid, cysteine, hydroxylamine, hydrazine, thiosulphate, dithionite, mitoxantrone, glutathione, iron(II) and thiourea were determined with theoretical molar absorptivities; carminic acid, sulphite, tin(II) chloride, 2,4-dinitrophenylhydrazine, sodium tetrahydroborate(III) and 2,3-dimercaptopropan-1-ol were determined with the aid of empirical linear absorbance–concentration plots. The proposed spectrophotometric method is rapid and allows the quantification of biologically important reducing agents.
69 citations
TL;DR: In this paper, the effect of pH on the electrochemical behavior of the mediators incorporated in the disposable electrodes was investigated, and the most promising mediators were cobalt phthalocyanine, iron phTHC and ferrocenecarbaldehyde.
Abstract: The evaluation of screen-printed carbon electrodes, chemically modified with selected ferrocene, phthalocyanine and hexacyanoferrate(III) derivative mediators for the determination of reduced glutathione (GSH), is described. Cyclic voltammetry was used to investigate the effect of pH on the electrochemical behaviour of these mediators incorporated in the disposable electrodes. Values of the electron-transfer coefficient (αna) were calculated for the oxidation of the mediators in phosphate buffer solution and solutions containing 0.48 mmol dm–3 GSH. Amperometry in stirred solutions was used to construct hydrodynamic voltammograms for each of the modified electrodes; these voltammograms were used to elucidate their steady-state behaviour. Both electrochemical techniques were used to calculate the reduction in overpotential for the oxidation of GSH; these calculations were performed for all of the chemically modified electrodes. Amperometry in stirred solutions was used as the technique for quantitative measurements, to determine the calibration response factors (µA mmol–1 dm3) and limits of detection for selected mediators towards GSH. The appropriate applied potentials were selected by reference to the hydrodynamic waves; a range of values were investigated to find the potential that gave the maximum sensitivity. The most promising mediators were cobalt phthalocyanine, iron phthalocyanine and ferrocenecarbaldehyde.
67 citations
TL;DR: A range of sensing systems are described which use electrochemical techniques for the measurement of various analytes and which have been demonstrated to be applicable to the manufacturing methods required for single-use disposable tests.
Abstract: The market for decentralized clinical testing is undergoing expansion. Electrochemical biosensors represent one approach to the different demands of this market. A range of sensing systems are described which use electrochemical techniques for the measurement of various analytes and which have been demonstrated to be applicable to the manufacturing methods required for single-use disposable tests.
64 citations
TL;DR: An analytical method based on a liquid-solid extraction (LSE) procedure followed by gas chromatography (splitless ‘hot’ injection mode) with electron-capture detection (GC-ECD) was developed and evaluated for tributyltin (TBT) chloride in fresh and marine waters.
Abstract: An analytical method based on a liquid–solid extraction (LSE) procedure followed by gas chromatography (splitless ‘hot’ injection mode) with electron-capture detection (GC-ECD) has been developed and evaluated for tributyltin (TBT) chloride in fresh and marine waters. Splitless ‘hot’ injection GC requires the rigorous exclusion of water from the eluting solvent and the sample extract solutions. Tributyltin chloride is thermally sensitive and tends to degrade in the injection liner. This thermal degradation, possibly a debutylation reaction, is enhanced in the presence of trace amounts of water. Electron capture detection, although offering adequate sensitivity, has insufficient specificity for TBT chloride at trace level concentrations. Also, the solvent, ethyl acetate, can extract compounds from the LSE column or cartridge housings. These compounds, phthalates, cresols, adipates, etc., may interfere with the measurement and detection of the analyte. Chromatograms of extracts of LSE discs and procedural blanks have ‘clean’ backgrounds in contrast to many of the LSE columns and cartridges. Extraction discs mounted in a tandem arrangement show no breakthrough of analyte from the front to the rear disc for sample volumes which ranged from 100 to 500 ml. Liquid–solid extraction appears to meet the need for sample collection (on-site), preservation/storage (column or disc) and convenient and inexpensive sample shipment. The TBT chloride can be preserved on column(s) or disc(s) for at least 1 month. Recoveries of the tin analyte at the 0.1 ng ml–1 level range between 91 and 104%.
TL;DR: By the use of Fourier transform infrared spectrometry, it was found that palladium chloride decreased the temperature of the reduction of PbO and Ga2O3 with graphite.
Abstract: By the use of Fourier transform infrared spectrometry it was found that palladium chloride decreased the temperature of the reduction of PbO and Ga2O3 with graphite; nickel chloride only catalysed the reduction of Ga2O3 A hypothesis is proposed that nickel and palladium salts promote the reduction of compounds (in atomic absorption measurements) at relatively low ashing temperatures The resultant free elements form intermetallic compounds or solid solutions with metallic Pd and Ni, thus reducing or almost eliminating loss of analyte due to sublimation of halides, oxides, dimers and other compounds The high efficiency and universal action of Pd modifiers are because the Pd metal can be easily formed from its compounds and also by the unique catalytic properties of metallic Pd
TL;DR: In this article, the authors investigated the relationship between NIR reflectance and particle size using data from ground wheat samples and found that the sensitivity of reflectance to particle size is dependent on the absorption properties of the material at the sampling wavelength.
Abstract: The interpretation of near infrared (NIR) reflectance in terms of material composition is complicated by particle size variation. An investigation is reported into the relationship between NIR reflectance and particle size using data from ground wheat samples. It is shown that the sensitivity of reflectance to particle size is dependent on the absorption properties of the material at the sampling wavelength. A theory relating a function of reflectance, known as the Kubelka–Munk function, to particle size suggests that the effects due to changing wheat composition can be isolated from the particle size effects using normalized Kubelka–Munk functions. Analysis of the spectral data from the ground wheat samples supports this theory. The ratio of Kubelka–Munk functions at appropriate absorption and reference wavelengths is subsequently manipulated to yield single term calibration equations for the protein and water in the wheat samples. Comments are made on the implication of the reported findings for various calibration techniques.
TL;DR: In this paper, a method for determining nitrate amperometrically by direct reduction at a freshly deposited copper electrode surface in a capillary-fill device (CFD) was developed.
Abstract: A method has been developed for determining nitrate amperometrically by direct reduction at a freshly deposited copper electrode surface in a capillary-fill device (CFD). Copper(II) is added to the nitrate sample which is then taken up into the device. The potential of the screen-printed carbon electrode is held at –0.75 V versus the screen-printed silver reference electrode. At this potential, copper is plated onto the carbon electrode forming a freshly prepared copper electrode. At the same time dissolved oxygen is reduced. The potential is then scanned to more negative potentials and the signal at –0.90 V, due to the reduction of the nitrate, is measured. The method for determining nitrate given here is preliminary to the production of CFDs in which chemical reagents, copper sulphate and potassium hydrogen sulphate (used to produce the acidity), are screen-printed or otherwise coated onto the upper plate within the device.
TL;DR: A sensitive spectrophotometric method using ascorbic acid (an easily available reducing agent) was applied successfully to the determination of paraquat in water, grain and plant materials.
Abstract: A sensitive spectrophotometric method for the determination of paraquat using ascorbic acid (an easily available reducing agent) is described. Paraquat is reduced with ascorbic acid in alkaline solution to give a blue radical ion with an absorbance maximum at 600 nm. Beer's law is obeyed in the range 12–96 µg of paraquat in 10 ml of the final solution (1.2–9.6 ppm). The important analytical parameters and the optimum reaction conditions were evaluated. The method was applied successfully to the determination of paraquat in water, grain and plant materials.
TL;DR: In this paper, the properties of ultraviolet radiation were exploited to obtain fluorescent products from three phenothiazine compounds (chlorpromazine, promethazine and perphenazine) and compared with chemical oxidation processes.
Abstract: The properties of ultraviolet radiation were exploited to obtain fluorescent products from three phenothiazine compounds (chlorpromazine, promethazine and perphenazine) Photochemical reactions were studied and compared with chemical oxidation processes After optimizing the working conditions, these reactions were applied to the determination of the analytes by stopped-flow injection methods (irradiation of the flow cell) and normal flow injection methods (irradiation of the reaction coil) The determination limits thereby achieved were 20 ng ml–1(chlorpromazine and perphenazine) and 50 ng ml–1(promethazine) with relative standard deviations of less than 2% in all instances (n= 11) Analyses for these compounds in pharmaceutical preparations were also carried out
TL;DR: The method is highly specific for the determination of ascorbic acid in the presence of dehydroascorbic acid and all other vitamins normally encountered with it in pharmaceutical dosage forms and can also be applied to the determination in some fresh fruit juices without interference from coloured and other substances present in the fruit extracts.
Abstract: A simple and selective method for the determination of ascorbic acid in pharmaceutical preparations and fresh fruit juices is described. The procedure is based on the reaction of ascorbic acid with the zinc chloride salt of diazotized 1-aminoanthraquinone (Fast Red AL salt) in an acidic medium, followed by development of a blue colour (λmax 630 nm) in alkaline solution. Different variables affecting the colour development were studied and optimized. The method was used to determine between 5 and 25 µg ml–1 of ascorbic acid in the final measured solution. The simplicity of the method permits rapid analysis, suitable for routine control. The method is highly specific for the determination of ascorbic acid in the presence of dehydroascorbic acid and all other vitamins normally encountered with it in pharmaceutical dosage forms. Moreover, the proposed method can also be applied to the determination of ascorbic acid in some fresh fruit juices without interference from coloured and other substances present in the fruit extracts. The reliability of the method was established by parallel determinations against the official British pharmacopoeial method.
TL;DR: It is demonstrated that FI constitutes an ideal method in order to monitor reproducibly and repeatedly the kinetically transient signal that is obtained, and the detection limit of the analytical procedure allows the samples to be diluted 100-fold, so that centrifugation for 5 min is the only preliminary sample preparation that is necessary.
Abstract: A simple and very sensitive spectrophotometric flow injection (FI) procedure for the determination of trace amounts of thiocyanate is described. The proposed method is based on the reaction between thiocyanate and 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol, which, in 2 mol dm–3 acidic media in the presence of a strong oxidizing agent, produces an intensely coloured product. Several oxidants are potentially applicable, but it is shown that dichromate is preferable. As the reaction product formed is unstable and the signal inherently is recorded on a high background level, it is demonstrated that FI constitutes an ideal method in order to monitor reproducibly and repeatedly the kinetically transient signal that is obtained. Based on optimization by a factorial experimental design, the detection limit of the procedure was found to be 3.5 µmol dm–3, and the standard deviation between samples was 0.16 µmol dm–3. No significant interferences were observed; a 1000-fold excess of cyanide could readily be tolerated within the experimental error. With a sample volume of 50 µl being injected, the sampling frequency was 60 samples h–1. The system was tested with saliva samples from non-smokers and smokers, and the results show that it is possible to distinguish between these two categories of individuals. As an added benefit, the detection limit of the analytical procedure allows the samples to be diluted 100-fold, so that centrifugation for 5 min is the only preliminary sample preparation that is necessary.
TL;DR: In this article, a two-step method for the determination of CrVI and CrIII in natural waters was developed, which is based on the variation of the coprecipitation yields with Pb(PDC)2 (PDC = pyrrolidine dithiocarbamate) as a function of pH.
Abstract: A two-step method for the determination of CrVI and CrIII in natural waters was developed. The method is based on the variation of the coprecipitation yields with Pb(PDC)2(PDC = pyrrolidine dithiocarbamate) as a function of pH. By using two different pH values both species can be determined separately. Firstly, CrVI was coprecipitated at pH 4.0 and then CrIII was separated at pH 9. Total chromium was determined by reduction of CrVI followed by coprecipitation at pH 9. The validity of the procedure was checked with the National Institute of Standards and Technology Standard Reference Material 1643b Trace Elements in Water and the result was found to be in good agreement with the certified value.
TL;DR: In this article, three 4-(aminosulphonyl)-2,1,3-benzoxadiazole amine derivatives (ABD-amines) were synthesized as fluorogenic reagents for carboxylic acids and all three reacted with fatty acids at room temperature (20-30 °C) in the presence of diethyl phosphorocyanidate (DEPC) to produce fluorescent adducts.
Abstract: Three 4-(aminosulphonyl)-2,1,3-benzoxadiazole amine derivatives (ABD-amines), 4-(aminosulphonyl)-7-(1-piperazinyl)-2,1,3-benzoxadiazole (ABD-PZ), 4-(aminosulphonyl)-7-(5-aminopentylamino)-2,1,3-benzoxadiazole (ABD-AP) and 4-(aminosulphonyl)-7-N-(2-aminoethylamino)-2,1,3-benzoxadiazole (ABD-AE), have been synthesized as fluorogenic reagents for carboxylic acids. All three reacted with fatty acids at room temperature (20–30 °C) in the presence of diethyl phosphorocyanidate (DEPC) to produce fluorescent adducts. The maximum wavelengths of arachidic acid labelled with ABD-PZ, ABD-AP and ABD-AE were 580 nm (excitation, 440 nm), 570 nm (excitation, 438 nm) and 573 nm (excitation, 429 nm), respectively. The rate of derivatization of ABD-PZ with arachidic acid was the slowest compared with those of ABD-AP and ABD-AE. However, the fluorescence intensity with ABD-PZ after a reaction time of 75 min was the highest among the three benzoxadiazoles. The ABD-amine reagents are applicable to the determination of carboxylic acids. Eight saturated free fatty acids derivatized with ABD-amines were completely separated with a linear elution gradient by use of a reversed-phase high-performance liquid chromatography column. The detection limits (signal-to-noise ratio = 3) that could be obtained for eight fatty acids were in the 10–50 fmol range.
TL;DR: In this article, two simple and sensitive spectrophotometric methods are described for the determination of six penicillin derivatives, based on the reaction of these drugs as n-electron donors with either 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) or 7,7,8,8-tetracyanoquinodimethane (TCNQ) as pi-acceptors, to give a highly coloured radical anion.
Abstract: Two simple and sensitive spectrophotometric methods are described for the determination of six penicillin derivatives. The methods are based on the reaction of these drugs as n-electron donors with either 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) or 7,7,8,8-tetracyanoquinodimethane (TCNQ) as pi-acceptors, to give a highly coloured radical anion. The coloured products are quantified spectrophotometrically at 460 and 842 nm for DDQ and TCNQ, respectively. The optimization of the different experimental conditions is described. The interference from streptomycin sulphate and common degradation products was also studied. The proposed methods were applied successfully to the determination of the different penicillins investigated, either in pure or dosage forms, with good accuracy and precision. The results were compared with those given by the official United States Pharmacopeial XXI method.
TL;DR: The conducting polymer poly(pyrrole, electrochemically prepared and doped with anions, has been found to be a responsive coating for a piezoelectric gas detection system.
Abstract: The conducting polymer poly(pyrrole), electrochemically prepared and doped with anions, has been found to be a responsive coating for a piezoelectric gas detection system. Polymers doped with bromide, nitrate and sulphate ions were tested. It was found that samples of ammonia gas cause a measurable frequency decrease, interpreted as adsorption by the polymer coating of the quartz crystal; the linear range was 0.05–1% for mixtures of the gas in nitrogen. These signals were found to correspond to simultaneous conductivity changes of a similarly prepared poly(pyrrole) sample, showing analogies in the two sensing mechanisms. The duality of the poly(pyrrole) response increases the possibilities of using it as a gas sensor.
TL;DR: A sensitive method for the accurate determination of Se in agricultural products at sub-ppm levels is described, and the accuracy of the method with which a detection limit of 0.002 micrograms g-1 of Se can be achieved is confirmed.
Abstract: A sensitive method for the accurate determination of Se in agricultural products at sub-ppm levels is described. The proposed procedure involves the wet oxidation of samples by using a mixture of nitric, sulphuric and perchloric acids, co-extraction of Se and added Pd with diethylammonium N,N-diethyldithiocarbamate in chloroform, and electrothermal atomic absorption spectrometric determination of Se in the organic extract. Atomization and extraction conditions are discussed. Special attention is given to the wet oxidation step, and its advantages in speed and simplicity over conventional heating have been evaluated using an automated microwave digestion system. The results reported, obtained from several reference materials, confirm the accuracy of the method with which a detection limit of 0.002 µg g–1 of Se can be achieved.
TL;DR: In this article, the authors used an aqua regia[HCl + HNO3(3 + 1)] leach followed by inductively coupled plasma mass spectrometry.
Abstract: Results are described for optimizing the rapid determination of precious metals in geological samples (principally of ophiolitic origin, including chromitites) using an aqua regia[HCl + HNO3(3 + 1)] leach followed by inductively coupled plasma mass spectrometry. Little improvement in extraction efficiency is afforded by aqua regia attack for longer than 30 min and heating the extraction mixture appears to have a detrimental effect on the extraction efficiency of the precious metals. The procedure was evaluated by analysis of a suite of standard reference materials and some independently analysed ophiolitic rock samples. Generally, Au and Pd are quantitatively extracted, Pt, Rh, Ru and Os are extracted to a lower but significant extent (20–40% recovery) and lr is poorly extracted (typically 1–10% recovery). The insolubility of selected platinum group element minerals in aqua regia is considered to be the dominant effect for the non-quantitative recoveries.
TL;DR: In this article, an amperometric sensor for the determination of sulphur dioxide in both gaseous atmospheres and solutions of low conductivity is described, which consists of a porous Pt electrode (facing the sample) supported on one face of an ion-exchange membrane (Nafion 417) which serves as a solid polymer electrolyte.
Abstract: An amperometric sensor is described for the determination of sulphur dioxide in both gaseous atmospheres and solutions of low conductivity. It consists of a porous Pt electrode (facing the sample) supported on one face of an ion-exchange membrane (Nafion 417) which serves as a solid polymer electrolyte. The other side of the membrane faces an internal electrolyte solution (1 mol dm–3 aqueous perchloric acid) containing the counter and reference electrodes. This sensor is inserted into a flow cell in which gaseous or electrolyte-free aqueous samples are fed by a peristaltic pump placed in a closed-loop path and SO2 is oxidized at an applied potential of 0.65 V versus Ag–AgCl. The device is found to be characterized by a high current sensitivity and a short response time, 24 A cm–2 mol–1 dm3 and 1 s respectively for gaseous samples; (0.4 A cm–2 mol–1 dm–3 and 4 s, respectively, for water solutions), and by good stability and low background noise. The dynamic range extends up to 2 × 10–4 mol dm–3(gaseous samples) and 1 × 10–3 mol dm–3(water samples) with good linearity, and detection limits of 8 × 10–9 mol dm–3(gaseous samples) and 4 × 10–7 mol dm–3(water samples) are predicted for a signal-to-noise ratio of 3. The advantages offered by this type of sensor over conventional gas-permeation membrane electrodes are discussed.
TL;DR: The di-n-butylamide-oNPOE based electrode functioned satisfactorily in serum, exhibiting a fast response time (10-15 s), an acceptable lifetime of 50 d and minimal protein interference.
Abstract: A series of neutral ionophore-based lithium-selective liquid-membrane electrodes have been prepared and the electrode performance compared with similar electrodes based on the lithium ionophores ETH 1810-ortho-nitrophenyl octyl ether (oNPOE) and ETH 2137-bis(1-butylpentyl) adipate (BBPA). By using a diamide substituted 14-crown-4 macrocycle, selectivities for Li+ in the presence of Na+ of log kpotLi,Na=–3.25 and –2.92 were obtained for diisobutylamide–oNPOE and di-n-butylamide–oNPOE derivatives. The di-n-butylamide–oNPOE based electrode functioned satisfactorily in serum, exhibiting a fast response time (10–15 s), an acceptable lifetime of 50 d and minimal protein interference.
TL;DR: The results provide further evidence for the suggestion that mucus is acting more than simply as a gel support for an unstirred water layer and is perhaps a more potent diffusion barrier to specific solutes.
Abstract: A diffusion chamber technique based on spectrophotometric analysis to determine effective diffusion coefficients for solutes with various relative molecular mass (Mr) values and properties, passing through native mucus gel, is reported. For all solutes studied, a reduction in effective diffusion coefficients is observed with a retardation of solute flux by a factor of at least two. For the solutes investigated (with Mr values ranging from 126–14 400 u), no consistent effect of solutes of low Mr was evident with regard to the retarding effect of mucus; however, at high Mr values (>4000 u) the retardation was greatly enhanced. A possible relationship between charged solutes of low Mr and the degree of retardation was observed, which possibly suggests the presence of ionic interactions of the solutes with the largely negatively charged mucus gel. The results provide further evidence for the suggestion that mucus is acting more than simply as a gel support for an unstirred water layer and is perhaps a more potent diffusion barrier to specific solutes.
TL;DR: In this article, a simple flow injection method for the determination of chlorpromazine, promethazine, trimeprazine and perphenazine over wide ranges of concentrations is described.
Abstract: A simple flow injection method for the determination of chlorpromazine, promethazine, trimeprazine and perphenazine over wide ranges of concentrations is described. The method is based on the oxidation of phenothiazine with ammonium metavanadate in sulphuric acid media and subsequent measurement of the coloured, oxidized form of the product at the corresponding wavelength. A sampling rate of up to 160 h–1 was attained. Relative standard deviations for the standard samples were usually less than 0.5%. The method was applied to the determination of phenothiazines in proprietary drugs and the results were comparable to those obtained by the official methods in the British Pharmacopoeia.
TL;DR: In this article, the drying and nitric acid digestion of fish tissue using a microwave oven for the determination of Hg and Se were studied, and the results showed that the efficiency of dissolution of dissolved HG and Se from dried muscle of tilapia, using concentrated HNO3 in the closed vessel microwave digestion method was found to be much greater than that of traditional open vessel digestion.
Abstract: The drying and nitric acid digestion of fish tissue using a microwave oven for the determination of Hg and Se were studied. For the drying process, the method was compared with the freeze-drying method. The water content found in the muscle of tilapia, Oreochromis mossanicus, by using a freeze dryer at –40 °C and a pressure of ⩽10 µmHg for 24 h, and a microwave oven (convection mode) at 70 °C for 3 h was 78.16 and 78.09% m/m, respectively. The Hg and Se levels found in fish tissues dried by the two methods were consistent with a 95% confidence level. The efficiency of dissolution of Hg and Se from dried muscle of tilapia, using concentrated HNO3 in the closed vessel microwave digestion method was found to be much greater than that of traditional open vessel digestion. The microwave heating digestion method was tested satisfactorily using two certified reference materials. The recovery of added standards of Hg and Se was found to be 84.8 and 96.6%, respectively.