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Showing papers in "Analyst in 1985"


Journal ArticleDOI
01 Jan 1985-Analyst
TL;DR: In this article, the results of a preliminary study of the mass spectrometry of solid samples using a ruby laser to ablate the sample into an inductively coupled plasma (ICP) source mass analyzer were described.
Abstract: The results are described of a preliminary study of the mass spectrometry of solid samples using a ruby laser to ablate the sample into an inductively coupled plasma (ICP) source mass spectrometer. Standard rock samples were used, pelletted with a binder into the form of a disc. Some 200 ablation pits could be accommodated on each sample. Laser pulse energies of 0.3–1 J were used in the fixed Q mode and the ablated material transferred from the ablation cell into the plasma torch by means of the plasma injector gas flow. The mass spectrometer was used in the fixed ion mode using mean ion current detection to evaluate the reproducibility of successive pulses on major constituents and in the scanning mode at the rate of 10 scans s–1 to produce spectra using mean current detection for major elements and pulse counting detection for traces. Problems were experienced with saturation of the detection system in both the mean current and pulse counting modes owing to the transient nature of the sample pulse from the laser, when attempting to quantify major elements, but except where a major peak was saturated, reasonably uniform sensitivity for most elements across the mass range from 7 to 238 m/z was obtained. Isotope ratio measurements were made on lead at 29 µg g–1 and detection limits for the elements examined appear to be 10 ng g–1 or less.

505 citations


Journal ArticleDOI
01 Jan 1985-Analyst
TL;DR: A rapid and sensitive method for the sequential determination of Cr(III)-Cr(VI) based on flow injection analysis-inductively coupled plasma atomic-emission spectrometry (FIA-ICP-AES) has developed as discussed by the authors.
Abstract: A rapid and sensitive method for the sequential determination of Cr(III)-Cr(VI) based on flow injection analysis-inductively coupled plasma atomic-emission spectrometry (FIA-ICP-AES) has been developed. A micro-column of activated alumina was used in the FIA manifold to separate and pre-concentrate Cr(VI) from Cr(III) in synthetic aqueous solutions before ICP detection at 267.72 nm. Linear calibration for Cr(III) and Cr(VI) was established over the concentration range 0–1000 µg l–1. The relative standard deviations at the 10 µg l–1 level for a 2-ml sample injection were 2.2% for Cr(III) and 1.1% for Cr(VI) and the corresponding limits of detection were 1.4 and 0.20 µg l–1, respectively. Determinations of Cr(III) and Cr(VI) at the µg l–1 level in reference waters of the National Bureau of Standards and the British Geological Survey were demonstrated.

133 citations


Journal ArticleDOI
01 Jan 1985-Analyst
TL;DR: The analysis of a mixture containing dipyrone and paracetamol in pharmaceutical preparations is carried out after their separation, which is based on the difference in their solubilities, and the excess of potassium hexacyanoferrate(III) is determined iodimetrically.
Abstract: A method is described for the determination of dipyrone and paracetamol in pharmaceutical preparations in which aliquots containing 1–15 mg of the sample are allowed to react with a known excess of potassium hexacyanoferrate(III) in 10 ml of 8 M sulphuric acid and 5 ml of 3% zinc sulphate solution at 35 °C in a thermostatically controlled water-bath for 15 min (paracetamol) or 25 min (dipyrone). The excess of potassium hexacyanoferrate(III) is then determined iodimetrically. The analysis of a mixture containing dipyrone and paracetamol in pharmaceutical preparations is carried out after their separation, which is based on the difference in their solubilities. On treatment with distilled water, dipyrone goes into solution while paracetamol remains insoluble and is subsequently dissolved in hydrochloric acid by heating on a boiling water-bath for 30 min. Results are within a ± 1.0% error.

90 citations


Journal ArticleDOI
01 Jan 1985-Analyst
TL;DR: In this paper, a simple high-performance liquid chromatography-flame atomic-absorption spectrometry coupling using pulse nebulization and a slotted tube atom trap is described for the speciation of tin in natural waters.
Abstract: A simple yet effective high-performance liquid chromatography-flame atomic-absorption spectrometry coupling utilising pulse nebulisation and a slotted tube atom trap is described for the speciation of tin in natural waters. The effects of the various parameters on analytical performance are discussed. A detection limit of 200 ng for tin was obtained and the separation of Sn(II), Sn(IV) and tributyltin was possible within 8 min. Tributyltin compounds have been quantified in local harbour waters, and in one harbour situation were observed at levels up to 0.47 µg l–1.

87 citations


Journal ArticleDOI
01 Jan 1985-Analyst
TL;DR: In this paper, the matrix effects due to calcium in inductively coupled plasma atomic-emission spectrometry have been characterised for a representative selection of analyte lines and several effective methods of obviating the matrix problem are demonstrated and compared.
Abstract: Matrix effects due to calcium in inductively coupled plasma atomic-emission spectrometry have been characterised for a representative selection of analyte lines. Operating conditions were typical of those widely used for routine analysis. Calcium is among the most potent elements causing matrix effects and is an important geological matrix element. Most analyte sensitivities were suppressed, by as much as 30% in some instances, but lithium could be supressed or enhanced depending on small changes in the conditions. The effects are strongly related to analyte excitation potentials, and were found to be caused by changes in excitation conditions in the plasma. Several effective methods of obviating the matrix problem are demonstrated and compared.

83 citations


Journal ArticleDOI
01 Jan 1985-Analyst
TL;DR: A graphite cup inserted into a graphite tube was investigated for the direct analysis of solid samples using graphite furnace AAS as mentioned in this paper, and the reproducibility of the results is typically around 10%.
Abstract: A graphite cup inserted into a graphite tube was investigated for the direct analysis of solid samples using graphite furnace AAS. Arsenic, cadmium, chromium, copper, lead and manganese were determined in reference materials. Atomisation from the cup delays sample volatilisation untilthe tube has stabilised in temperature so that the same effect is obtained as with a L'vov platform. Background attenuation and non-spectral interferences are substantially reduced under these near-thermal equilibrium conditions, so that all determinations can be carried out against acid reference solutions. The reproducibility of the results is typically around 10%. The values obtained are not always within the recommended or certified range; the accuracy is more than acceptable, however, for a semi-quantitative determination or for screening purposes.

74 citations


Journal ArticleDOI
01 Jan 1985-Analyst
TL;DR: In this article, the effects of magic-angle rotation and cross-polarization techniques on signal intensities of high-resolution NMR spectra for dilute spin-1/2 nuclei in solids are discussed, and examples given.
Abstract: The effects of the magic-angle rotation and cross-polarisation techniques on signal intensities (particularly relative signal intensities) of high-resolution nuclear magnetic resonance (NMR) spectra for dilute spin-1/2 nuclei in solids are discussed, and examples given. The value of undertaking a range of different experiments is emphasised, particularly for discriminating between different chemical sites or physical environments.

72 citations


Journal ArticleDOI
01 Jan 1985-Analyst
TL;DR: Good agreement was achieved between results obtained by a standard additions procedure and by direct calibration with aqueous standards, and also by an alternative wet digestion procedure.
Abstract: A simple method for the determination of lead in spinach involving minimum sample preparation is described. The powdered spinach is suspended in a thixotropic thickening agent, Viscalex HV30, and the slurry is injected directly into the electrothermal atomiser. Oxygen is introduced during the ashing stage to allow the use of higher ash temperatures and to avoid the build up of carbonaceous residue in the tube. Concentrations of powdered spinach up to 10%m/V can be tolerated in the suspension. Good agreement was achieved between results obtained by a standard additions procedure and by direct calibration with aqueous standards, and also by an alternative wet digestion procedure.

71 citations


Journal ArticleDOI
01 Jan 1985-Analyst
TL;DR: The proposed method and the referee method gave statistically similar results for the determination of chlorpromazine and its sulphoxide in injectables, tablets and syrups, and it is suggested that similar methodology should be applicable to the analysis of other members of the phenothiazine class of compounds.
Abstract: In pharmaceutical dosage forms, interference in the UV spectra of analytes by other UV-absorbing solutes leads to a requirement for the development of procedures with greater specificity. One method used to address this problem is the technique of derivative spectroscopy, where the composite spectrum is transformed to the second or higher derivative in the wavelength domain. This paper reports the novel application of this technique to the determination of a phenothiazine (chlorpromazine) and its sulphoxide impurity in various pharmaceutical dosage forms.A systematic approach developed for optimisation of the derivative order, graphical measurement and instrumental conditions led to the adoption of third-order derivative spectroscopy as a method with suitable precision and selectivity for the determination of the phenothiazines. Both the parent compound and the sulphoxide impurity can be assayed in dosage forms by measurement of the amplitudes of, respectively, the positive peak at 259 nm with respect to the negative peak at 267 nm, and the positive peak at 350 nm with respect to the negative peak at 361 nm. A new notation for denoting these amplitude measures is proposed, viz., 3D259,267 and 3D350,361, respectively. By comparison with an independent referee method based on reversed-phase HPLC, the proposed method and the referee method gave statistically similar results for the determination of chlorpromazine and its sulphoxide in injectables, tablets and syrups. The figures of merit for the proposed assays are described in terms of response linearity, 95% confidence limits, relative standard deviation, recovery data and correlation coefficients. It is suggested that similar methodology should be applicable to the analysis of other members of the phenothiazine class of compounds.

67 citations


Journal ArticleDOI
01 Jan 1985-Analyst
TL;DR: In this paper, the effects of polishing and cleaning, chemical and electrochemical surface treatments, pH, supporting electrolyte cations and anions and time on the redox behavior of the system were systematically evaluated.
Abstract: Detailed cyclic voltammetric studies were carried out on the hexacyanoferrate(II)-hexacyanoferrate(III) redox system in H2SO4, Na2SO4, NaOH, NaCl, KCl, NaH2PO4, Na2C2O4 and trisodium citrate media on a glassy carbon electrode. The effects of polishing and cleaning, chemical and electrochemical surface treatments, pH, supporting electrolyte cations and anions and time on the redox behaviour of the system were systematically evaluated. The following conclusions were drawn: (a) surface polishing or exposure to the atmosphere does not affect the reproducibility of the results; (b) anodic polarisation activates the electrode surface, as found in earlier studies, but some additional evidence indicates that this is due to oxidation of the fresh carbon surface, and this aspect is considered in detail; (c) the rate constants calculated for the oxidation of hexacyanofer-rate(II) and the reduction of hexacyanoferrate(III) using Nicholson's method differ substantially; this is attributed to different surface states of the glassy carbon at the starting potentials; and (d) anions have a substantial effect on both the rate constants and the limiting currents; chloride ions have a special activating effect. These effects are discussed on the basis of adsorption and mediated electron transfer. Other factors that influence the electron-transfer kinetics such as time effects and heat-treatment temperature are also discussed.

59 citations


Journal ArticleDOI
01 Jan 1985-Analyst
TL;DR: High-performance liquid chromatography with dual-electrode electrochemical detection has been used to determine normal and sub-normal circulating plasma levels of phylloquinone and concentrations down to 20 pg ml–1 have been measured in plasma.
Abstract: High-performance liquid chromatography (HPLC) with dual-electrode electrochemical detection has been used, in the redox mode, to determine normal and sub-normal circulating plasma levels of phylloquinone (vitamin K1) and concentrations down to 20 pg ml–1 have been measured in plasma. The coefficient of variation, for endogenous levels, was 10%(mean 330 pg ml–1; n= 6). When compared with a single glassy carbon electrode, operated in the reductive mode, the sensitivity of the dual-electrode cell was greater by at least an order of magnitude. Thus the volume of plasma required for the assay could be reduced.

Journal ArticleDOI
01 Jan 1985-Analyst
TL;DR: A flow injection analysis procedure using this detector has been constructed and some interferences assessed as discussed by the authors, and one of the interfering species was found to be ascorbic acid, and the analysis of an extract of a cooked meat was given satisfactory results when ion-interaction chromatography, with amperometric detection, was used.
Abstract: Nitrite ion has been determined amperometrically by oxidation at a glassy carbon electrode. A flow injection analysis procedure using this detector has been constructed and some interferences assessed. One of the interfering species was found to be ascorbic acid, and the analysis of an extract of a cooked meat was found to give satisfactory results when ion-interaction chromatography, with amperometric detection, was used.

Journal ArticleDOI
01 Jan 1985-Analyst
TL;DR: In this article, the authors describe the automated interface between a nitrogen analyser and an isotope ratio mass spectrometer, which can be used for unattended analysis of up to 50 samples for total nitrogen and nitrogen isotope ratios at the rate of 12 per hour.
Abstract: The computerised automation of an interface between a nitrogen analyser and an isotope ratio mass spectrometer is described. Unattended analysis of up to 50 samples for total nitrogen and nitrogen isotope ratio can be carried out at the rate of 12 per hour.


Journal ArticleDOI
01 Jan 1985-Analyst
TL;DR: Revue de 174 references sur l'analyse des isocyanates organiques atmospheriques par colorimetrie, spectrometrie IR, chromatographie en phase gazeuse, sur couche mince, HPLC.
Abstract: Revue de 174 references sur l'analyse des isocyanates organiques atmospheriques par colorimetrie, spectrometrie IR, chromatographie en phase gazeuse, sur couche mince, HPLC

Journal ArticleDOI
01 Jan 1985-Analyst
TL;DR: A flow injection analysis method for determining cyanide amperometrically by oxidation at an electrochemically pre-treated glassy carbon electrode has been developed in this paper, where the determination was made in an eluent consisting of pH 9 Britton-Robinson buffer using a measurement potential of + 1.00 V versus SCE.
Abstract: A flow injection analysis method for determining cyanide amperometrically by oxidation at an electrochemically pre-treated glassy carbon electrode has been developed. The determination was made in an eluent consisting of pH 9 Britton-Robinson buffer using a measurement potential of + 1.00 V versus SCE. The glassy carbon electrode was pre-treated on-line in the same eluent before use by holding it at +1.50 V versus SCE for 15 min and then at –1.00 V for 1 min. Calibration graphs were rectilinear from 1 × 10–5 to 1 × 10–3M cyanide and coefficients of variation (10 determinations) were typically less than 1% except at the lower end of this range.

Journal ArticleDOI
01 Jan 1985-Analyst
TL;DR: In this article, the authors used principal components analysis (PCA) to show that more than 90% of the total variance in routine analysis by ICP-AES is not random but multi-element correlated and therefore potentially correctable.
Abstract: For practical purposes the precision of inductively coupled plasma atomic-emission spectrometry (ICP-AES) is limited by medium-term changes of sensitivity, i.e., those occurring on a time scale shorter than the period between calibration adjustments. For any ICP-AES it is this longer term lack of reproducibility that limits its capacity to match other multi-element methods (such as X-ray fluorecence) for high precision analysis.This paper describes the application of principal components analysis to show that more than 90% of the total variance in routine analysis by ICP-AES is not random but multi-element correlated and therefore potentially correctable. Ten possible causes of this variation are quantified in terms of their particular multi-element respose “signatures”. Comparison of the ten signatures suggests that only two signatures predominate, despite being produced by seven apparently independent instrumental parameters.A new method of improving the medium-term precision of ICP-AES is described in which the variation from the two predominating signatures on all analytes is removed by use of the parameter-related internal standard method (PRISM). Two internal standard elements are chosen each of which responds significantly to only one of the two predominating signatures. Two instrumental parameters, forward power and nebuliser uptake rate, are varied separately. In each instance the response of each analyte is related to corresponding variation of the appropriate internal standard. For subsequent routine analysis a straightforward mathematical correction is then applied to each analyte using the measured function relating that analyte with both internal standards.

Journal ArticleDOI
01 Jan 1985-Analyst
TL;DR: Lithium-selective electrodes were prepared with polymeric membranes containing dodecyl-methyl-14-crown-4 as a neutral carrier and addition of trioctylphosphine oxide to the membrane enhanced the lithium selectivity over sodium in the electrode, although it had adverse effects on the lithiumSelectivity over hydronium ion and the detection limit.
Abstract: Lithium-selective electrodes were prepared with polymeric membranes containing dodecyl-methyl-14-crown-4 as a neutral carrier. The effects of the crown ether content in the membrane and the type of membrane solvent on the electrode properties were investigated. Typical Li+-selective electrodes showed a linear Nernstian response in the activity range 1 × 10–5–1 M LiCl, preferring lithium to sodium and hydronium ions by factors of 150 and 6800, respectively. Addition of trioctylphosphine oxide to the membrane enhanced the lithium selectivity over sodium in the electrode, although it had adverse effects on the lithium selectivity over hydronium ion and the detection limit. The determination of lithium in artificial serum samples was also attempted with these lithium-selective electrodes.

Journal ArticleDOI
01 Jan 1985-Analyst
TL;DR: High-performance liquid chromatographic methods have been developed for the determination of ampicillin (ABPC), amoxicillin (AMPC) and ciclacillin (ACPC) in serum and urine and are specific to intact penicillins without interference from the corresponding penicilloates.
Abstract: High-performance liquid chromatographic methods have been developed for the determination of ampicillin (ABPC), amoxicillin (AMPC) and ciclacillin (ACPC) in serum and urine. The methods involve acetylation of these aminopenicillins with acetic anhydride in aqueous solutions (pH 9.0) at ambient temperature for 3 min followed by reaction with 2 M 1,2,4-triazole and 10–3M mercury(II) chloride in solution (pH 9.0) at 60 °C for 10 min. The resulting products were separated on a C18 column following stabilisation in an eluent containing sodium thiosulphate. They were detected at 328 nm for ABPC and AMPC and 327 nm for ACPC.The methods have been applied to assays of these aminopenicillins in serum and urine. The procedures, which permit the accurate determination of aminopenicillin concentrations in serum down to 0.05 µg ml–1 for AMPC and 0.1 µg ml–1 for ABPC and ACPC, are specific to intact penicillins without interference from the corresponding penicilloates. At an aminopenicillin concentration of 1 µg ml–1 in serum, the within- and between-run precisions were 0.97–3.51% and 2.07–3.55%, respectively.

Journal ArticleDOI
01 Jan 1985-Analyst
TL;DR: A thin-layer chromatographic procedure utilising fluorescamine detection is described for the quantitation of cephradine, cefaclor, cephalexin and cefadroxil and the applicability of the method to the determination of these cephalosporins in serum, urine and pharmaceutical formulations is discussed.
Abstract: A thin-layer chromatographic procedure utilising fluorescamine detection is described for the quantitation of cephradine, cefaclor, cephalexin and cefadroxil. The repeatability, sensitivity and detectability of the method are compared with those for o-phthalaldehyde fluorescence emission and UV absorption measurements on the plate. The applicability of the fluorescamine method to the determination of these cephalosporins in serum, urine and pharmaceutical formulations is discussed.

Journal ArticleDOI
01 Jan 1985-Analyst
TL;DR: In this paper, the vapour phase chromatographic analysis of the ethanol extract of leaves of Eucalyptus species has been investigated in order to develop a more accurate determination of the terpene content.
Abstract: The vapour-phase chromatographic analysis of the ethanol extract of leaves of Eucalyptus species has been investigated in order to develop a more accurate determination of the terpene content. Conventional techniques based on steam distillation have been shown to have serious faults when compared with solvent extraction procedures. The convenience of the method during both the field sampling and the laboratory analysis stages is a major advantage. The procedure is suitable for large numbers of samples and requires only small amounts of leaf material.

Journal ArticleDOI
01 Jan 1985-Analyst
TL;DR: In this paper, the analyte element in a molecular form during volatilisation of the matrix or, in general, during pre-atomisation treatment steps are found to be dominant when antimony and nickel chloride are mixed.
Abstract: Analyte and interferent are volatilised from separated spots of a L'vov platform with two cavities. The results obtained give a deeper insight into the mechanisms of interferences observed in a graphite tube furnace. Losses of the analyte element in a molecular form during volatilisation of the matrix or, in general, during pre-atomisation treatment steps are found to be dominant when antimony and nickel chloride are mixed. Pronounced interactions between the gas phase and the condensed phase are observed, however, when the analyte and interferent are separated on the dual cavity platform. Essentially, all interferences disappear when nickel in nitric acid is used as a matrix modifier and proper conditions are selected. The absence of any gas-phase interactions allows the conclusion that near thermal equilibrium is obtained under these conditions. The characteristic mass found for antimony was typically between 25 and 30 pg per 0.0044 A s.

Journal ArticleDOI
01 Jan 1985-Analyst
TL;DR: A slotted quartz tube used with an air-acetylene flame increases the residence time of atoms in the light path of an atomic-absorption spectrometer, thus increasing the analytical sensitivity, and the measurement of metals in urine was investigated.
Abstract: A slotted quartz tube used with an air-acetylene flame increases the residence time of atoms in the light path of an atomic-absorption spectrometer, thus increasing the analytical sensitivity. With this technique lead and cadmium were determined in whole blood following precipitation of cells and protein with trichloroacetic acid, copper and zinc were determined in serum diluted 1 + 20 and the measurement of metals in urine was investigated. Rapid, accurate analyses can be achieved using continuous aspiration or, when there is limited volume of sample, by discrete nebulisation. Long-term performance was assessed during a period of 3 months.

Journal ArticleDOI
01 Jan 1985-Analyst
TL;DR: In this paper, a modification of the HPLC procedure enabling lead, cadmium and mercury(II) ions to be determined is suggested, and a method for the multi-element identification of metals in pollution studies is presented.
Abstract: The combination of HPLC with direct injection and on-column derivatisation provides a method for the multi-element identification of metals in pollution studies. However, problems have occurred when this technique has been applied to the determination of heavy metal ions. In this work the reasons for these difficulties has been studied and a modification of the procedure enabling lead, cadmium and mercury(II) ions to be determined is suggested.

Journal ArticleDOI
01 Jan 1985-Analyst
TL;DR: Whole blood glucose measurements were correlated with a spectrophotometric method based on glucose oxidase and the derivatised signal allowed temporal of the enzyme-mediated signal from electrochemical interference.
Abstract: Glucose dehydrogenase (E.C. 1.1.99.17) has been used to produce an amperometric enzyme electrode for glucose. With phenazine ethosulphate as the electron mediator, a linear response for up to 0.8 mM glucose was obtained with response times of 3–5 min. 2,6-Dichlorophenolindophenol as mediator gave long (> 30 min) response times, but the measurement time was reduced to 30 s by monitoring the first-order differential of the response; the derivatised signal allowed temporal separation of the enzyme-mediated signal from electrochemical interference. Whole blood glucose measurements were correlated with a spectrophotometric method based on glucose oxidase (y= 0.84x + 0.67, r= 0.963, n= 36).

Journal ArticleDOI
01 Jan 1985-Analyst
TL;DR: The combination of the platform, integrated absorbance, new coated tubes and oxygen addition to the charring step, provided better precision and smaller variation during the life of the tube, and good results were achieved by standardising the procedure against a calibration graph.
Abstract: The method previously described by Casetta et al. for the determination of aluminium in dilute (1 + 1) human serum using matrix modification and a stabilised temperature platform furnace has been considered. The combination of the platform, integrated absorbance, new coated tubes and oxygen addition to the charring step, provided better precision and smaller variation during the life of the tube. Good results were achieved by standardising the procedure against a calibration graph if integrated absorbance signals were used for quantitation. The calibration was linear up to at least 150 µg l–1 of aluminium; the within-run and between-run precision was 5.5 and 6.5%, respectively (at 14.3 µg l–1 of aluminium); and the recovery of aluminium added to pooled serum ranged between 97 and 102%. Furnace lifetimes in excess of 200–250 firings using oxygen ashing were routinely achieved.

Journal ArticleDOI
01 Jan 1985-Analyst
TL;DR: The carbon fibre array electrode is demonstrated as a useful detector for flow injection analysis in the amperometric mode of detection for oxidations of three pharmaceutically important phenothiazine drugs.
Abstract: The carbon fibre array electrode is demonstrated as a useful detector for flow injection analysis in the amperometric mode of detection.A liquid chromatographic internal sampling valve was used to inject the sample into the supporting electrolyte stream and sampling rates as high as 200 samples per hour were feasible using a flow-rate of 1 ml min–1. The oxidations of three pharmaceutically important phenothiazine drugs, namely perphenazine, triflupromazine. HCI and fluphenazine.2HCI, were investigated and an assay procedure was developed for these compounds and their formulations. Detection limits for the analytes were a few tenths of ananogram.

Journal ArticleDOI
01 Jan 1985-Analyst
TL;DR: An automated anion-exchange high-performance liquid chromatographic technique has been adapted to accommodate the interferences caused by organic matter present in the samples and has been found to be accurate, rapid and precise.
Abstract: A method is described for the determination of nitrate-nitrogen in vegetables in which an automated anion-exchange high-performance liquid chromatographic technique has been adapted to accommodate the interferences caused by organic matter present in the samples. The described method has been found to be accurate, rapid and precise.

Journal ArticleDOI
01 Jan 1985-Analyst
TL;DR: The alkaline treatment method was found to be the best for the concentrations normally encountered in commercial drinks, and its working parameters have been optimised and their effects on the analysis are discussed.
Abstract: For the determination of ascorbic acid in soft drinks and fruit juices, spectrophotometry is the most commonly used instrumental method. Although UV spectrophotometry is a fast and simple method, matrix interference has been shown in this work to be a problem that can be solved by correcting the background absorption.Background correction methods such as thermal decomposition, catalytic conversion, UV light decomposition and alkaline treatment have therefore been investigated and evaluated. The alkaline treatment method was found to be the best for the concentrations normally encountered in commercial drinks. Hence, its working parameters have been optimised and their effects on the analysis are discussed.

Journal ArticleDOI
01 Jan 1985-Analyst
TL;DR: A simple and rapid spectrophotometric method based on the complexation of salicylic acid with copper(II) acetate to form a stable yellowish green complex based on Beer's law is obeyed over the range 0.2–4.0 mg ml–1 of salcylic acid and the complex is stable for 30 h.
Abstract: A simple and rapid spectrophotometric method for the determination of salicylic acid alone or in pharmaceutical preparations has been developed based on the complexation of salicylic acid with copper(II) acetate to form a stable yellowish green complex at pH 5.5–6. The yellowish green species has an absorption maximum at 730 nm with a molar absorptivity of 0.02 × 103 l mol–1 cm–1. Beer's law is obeyed over the range 0.2–4.0 mg ml–1 of salicylic acid and the complex is stable for 30 h. The precision of the method is 1.42%. Benzoic acid and boric acid interfere in the normal procedure but interference from boric acid can be removed by extraction with diethyl ether.