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Showing papers in "Analyst in 1987"


Journal ArticleDOI
01 Jan 1987-Analyst
TL;DR: In this article, a regression-like technique, maximum-likelihood fitting of a functional relationship (MLFR), is explained and demonstrated to work well, under some conditions weighted regression provides a good approximation to MLFR.
Abstract: Regression techniques are commonly applied to compare two analytical methods at several concentrations and to test the biases of one method relative to another. However, regression is strictly applicable only when one method is without error, for example in comparisons with reference materials. A regression-like technique, maximum-likelihood fitting of a functional relationship (MLFR), is explained and is demonstrated to work well. Under some conditions weighted regression provides a good approximation to MLFR, and so can be used if more convenient.

246 citations


Journal ArticleDOI
01 Jan 1987-Analyst
TL;DR: The method described in this study has a detection limit of about 0.07 µmol l–1(3 SD) and a precision and accuracy of ±2–5% at the 0.24–2.4 µmolL–1 concentration level and compared with the previous blood lead analytical method used in other surveys via the analysis of 435 specimens.
Abstract: Accuracy in the determination of blood lead is of primary importance in such diverse activities as screening for childhood lead poisoning, occupational exposure monitoring and population surveys. To meet the stringent requirements of the third National Health and Nutrition Examination Survey (NHANES III), a large normative population study to be held from 1988–1994, we needed a method for the determination of lead in blood that was simple, accurate, rugged and of defined accuracy for both calibration and control materials. The recent availability of the National Bureau of Standards Standard Reference Materials 2121–2 and 955, a lead standard solution (10 000 mg l–1) and a certified lead in blood reference material has made it possible to evaluate a method against definitive values and NBS reference materials.In the proposed method, sample preparation consists of a simple dilution (1 + 9) with a matrix modifier which contains 0.5%V/V Triton X-100, 0.2%V/V 16 M nitric acid and 0.2%m/V dibasic ammonium phosphate. This matrix modifier stabilises lead so that the majority of the blood matrix may be removed during the char step. Maximum accuracy in dilution is achieved with the use of autopipettes which have been shown to deliver viscous materials such as blood and serum with high accuracy. The method described in this study has a detection limit of about 0.07 µmol l–1(3 SD) and a precision and accuracy of ±2–5% at the 0.24–2.4 µmol l–1 concentration level. Linearity has been demonstrated up to about 4 µmol l–1. Comparability has been established with the previous blood lead analytical method used in other surveys via the analysis of 435 specimens by both the previous (modified Delves cup) and proposed methods. The equation of the resulting line is [ETA-AAS]= 1.0007[Delves]– 0.051, r= 0.924.

202 citations


Journal ArticleDOI
01 Jan 1987-Analyst
TL;DR: In this article, a probe configuration used in this study for pH measurement consists of fluorescein isothiocyanate (FITC) covalently bonded to a porous glass bead.
Abstract: Fibre optic sensing is a growing technology in analytical chemistry. Scattering, absorbance, reflectance and luminescence spectroscopic measurements have been made using fibre waveguides. Fluorescence is particularly suited for use in fibre sensing because of its sensitivity and versatility, and the ease with which this type of measurement may be implemented with a single fibre optic.The probe configuration used in this study for pH measurement consists of fluorescein isothiocyanate (FITC) covalently bonded to a porous glass bead. This bead is attached to a single, multi-mode optical fibre, which conducts both the excitation and emission radiations. The increase in fluorescence intensity, as the acid form of the immobilised FITC is converted to its basic form, is related to the pH. The dynamic range of this miniature probe is pH 3–7 and this can be extended by decreasing the dye loading. The response time is between 20 and 35 s, depending on the capacity.

137 citations


Journal ArticleDOI
01 Jan 1987-Analyst
TL;DR: A gas chromatographic procedure using a graphitised carbon black packing coated with Carbowax 20M has been developed for the determination of volatile fatty acids and lactic acid in silage as discussed by the authors.
Abstract: A gas chromatographic procedure using a graphitised carbon black packing coated with Carbowax 20M has been developed for the determination of volatile fatty acids and lactic acid in silage. This packing gave improved results compared with porous polymer column materials. The method was precise (relative standard deviation for each acid 0.5–5%) and gave a quantitative recovery of acids spiked into silage extracts (98–109%). The results for the determination of lactic acid in silage obtained by the GC procedure were in good agreement with results obtained by a classical distillation procedure; however, the GC method was more selective, more precise and less time consuming. The method has been shown to be of value in the determination of volatile fatty acids and lactic acid in connection with the assessment of silage quality.

111 citations


Journal ArticleDOI
01 Jan 1987-Analyst
TL;DR: The major constituents of the archaeological samples were observed to be alkyl-substituted, tricyclic diterpenoids based on the abietane and pimarane skeletons as discussed by the authors.
Abstract: Six samples of tar and pitch from the wreck of the Mary Rose (Tudor, AD 1509–45) and a sample of pitch from an Etruscan shipwreck (ca. 600 BC) have been analysed by a number of modern analytical techniques (elemental analysis, IR and NMR spectroscopy, GC and GC-MS). Similar analyses were performed on samples of contemporary tars, derived from natural sources, for comparative purposes. The major constituents of the archaeological samples were observed to be alkyl-substituted, tricyclic diterpenoids based on the abietane and pimarane skeletons. Similar molecular compositions and spectral properties were found for Stockholm tar (a good quality wood tar obtained by the destructive distillation of Pinus sylvestris), and Tudor and Etruscan pitches, thus providing conclusive evidence for the derivation of the archaeological samples from pine wood. The analytical techniques utilised are compared for their relative usefulness in chemical archaeology.

104 citations


Journal ArticleDOI
01 Jan 1987-Analyst
TL;DR: In this paper, a combination of the neo-classical nickel sulphide fire assay collection procedure with final determination by ICP-MS is considered in relation to the simplified procedure required for dissolution of the nickel sulfide “button” and the wealth of information inherent in ICPMS spectra.
Abstract: Preliminary work on the application of fire assay and inductively coupled plasma source mass spectrometry (ICP-MS) to the determination of platinum-group elements (PGEs) in geological materials is described. A combination of the neo-classical nickel sulphide fire assay collection procedure with final determination by ICP-MS is considered in relation to the simplified procedure required for dissolution of the nickel sulphide “button” and the wealth of information inherent in ICP-MS spectra. The method was applied to the determination of five PGEs and gold in the South African standard reference material PTO-1 (now known as SARM-7) and the Canadian standard reference material PTC-1. Isotope dilution analysis was applied to the determination of platinum.

102 citations


Journal ArticleDOI
01 Jan 1987-Analyst
TL;DR: In this paper, a comparison is made of the use of riboflavin and 3-cyclohexylaminopropanesulphonic acid (CAPS) to increase the sensitivity of the determination of sulphite in a flow injection procedure based on the chemiluminescence produced by permanganate oxidation in an acidic solution.
Abstract: A comparison is made of the use of riboflavin and 3-cyclohexylaminopropanesulphonic acid (CAPS) to increase the sensitivity of the determination of sulphite in a flow injection procedure based on the chemiluminescence produced by permanganate oxidation in an acidic solution. Both procedures give linear calibration graphs for 5–60 ng of sulphite, but the CAPS procedure has a lower detection limit (1.2 ng) and better relative standard deviation (RSD)(2.5% for 40 ng, n=10). Riboflavin enhancement arises from energy transfer, but the reason for the CAPS enhancement could not be identified with certainty.

85 citations


Journal ArticleDOI
01 Jan 1987-Analyst
TL;DR: Solid-liquid extraction procedures for the isolation of morphine from whole blood and urine are described, as is the synthesis of the internal standard, N-ethylnormorphine, with improved selectivity and sensitivity over UV detection.
Abstract: HPLC has been used in combination with chemiluminescence detection for the determination of morphine in biological fluids. Solid-liquid extraction procedures for the isolation of morphine from whole blood and urine are described, as is the synthesis of the internal standard, N-ethylnormorphine. Improved selectivity and sensitivity over UV detection is apparent. The procedure has a detection limit of 5 ng of morphine on-column after extraction from blood or urine. The utility of the procedure has been tested on forensic case samples.

80 citations


Journal ArticleDOI
01 Jan 1987-Analyst
TL;DR: Di-and tributyltin compounds present in marine and estuarine waters at sub-parts per billion (<µg l–1) levels were determined using two different chemical speciation procedures using simultaneous hydride generation-dichloromethane extraction procedure and gas chromatographic separation and flame photometric detection.
Abstract: Di-and tributyltin compounds present in marine and estuarine waters at sub-parts per billion (<µg l–1) levels were determined using two different chemical speciation procedures. Generally, good analytical agreement was obtained from split samples independently analysed by a simultaneous hydride generation-dichloromethane extraction procedure followed by gas chromatographic separation and flame photometric detection (GC-FPD, performed at the National Bureau of Standards) and by a hydride generation procedure followed by purge and trap collection with boiling-point separation and atomic absorption detection (HG-AA, performed at the Naval Ocean Systems Center). Sea water samples containing tributyltin at sub-p.p.b. levels can be stored frozen (–20 °C) in polycarbonate containers for up to 2–3 months without any serious loss of analyte.

80 citations


Journal ArticleDOI
01 Jan 1987-Analyst
TL;DR: Silica modified by the addition of mercapto chelating groups has been developed for the pre-concentration of trace metals from natural waters as discussed by the authors, which removes cadmium, copper, lead and zinc from aqueous solution.
Abstract: Silica modified by the addition of mercapto chelating groups has been developed for the pre-concentration of trace metals from natural waters. This material removes cadmium, copper, lead and zinc from aqueous solution and can be employed for the pre-concentration of these metals by both column and batch techniques. Under column and batch conditions recoveries larger than 95% were common. For batch extractions of cadmium, zinc, copper and lead from sea water, recoveries of 91 ± 5, 98 ± 4, 97 ± 4 and 96 ± 5%, respectively, were obtained.

80 citations


Journal ArticleDOI
01 Jan 1987-Analyst
TL;DR: In this article, a surface modified silica gel was developed for the pre-concentration of arsenite from natural waters using 3-mercaptopropyl trimethoxysilane.
Abstract: A surface-modified silica gel has been developed for the pre-concentration of arsenite from natural waters. The reaction of silica gel with (3-mercaptopropyl)trimethoxysilane produces a mercapto-modified silica gel with a silver capacity of ca. 0.9 mmol g–1. This material selectively removes arsenite from samples that also contain arsenate, monomethylarsonate and dimethylarsinate, and can be employed for both the column and batch pre-concentration of arsenite. Under column and batch conditions recoveries of ca. 96 and 94% are obtained but reproducibility is better for the column technique.

Journal ArticleDOI
01 Jan 1987-Analyst
TL;DR: In this article, an optical fiber sensor is described which is sensitive to potassium ions in aqueous solution in the concentration range 10 −3 −10 −1M, where m is the number of ions in the solution.
Abstract: An optical fibre sensor is described which is sensitive to potassium ions in aqueous solution in the concentration range 10–3–10–1M.

Journal ArticleDOI
01 Jan 1987-Analyst
TL;DR: A continuous precipitation and filtration flow system coupled on-line with an atomic absorption spectrometer for the quantitative pre-concentration and determination of lead at the micrograms per litre level is described, which has been satisfactorily applied to the determination oflead in tap water.
Abstract: A continuous precipitation and filtration flow system coupled on-line with an atomic absorption spectrometer for the quantitative pre-concentration and determination of lead at the micrograms per litre level is described. PbII forms a precipitate with ammonia, which is retained on a stainless-steel filter and then dissolved by a stream of nitric acid. A concentration factor of up to 700 is achieved. Several calibration graphs suited to the degree of enrichment are proposed for the determination of lead(II) in the range 1.2–1500 ng ml–1; sampling rates of 1–15 h–1 and relative standard deviations of less than 3.6% are afforded by the proposed method, which has been satisfactorily applied to the determination of lead in tap water.

Journal ArticleDOI
01 Jan 1987-Analyst
TL;DR: In this paper, the ion associate formed between molybdophosphate and Malachite Green was extracted into benzene-4-methylpentan-2-one (1 + 2 V/V) and the absorbance was measured at 630 nm.
Abstract: Phosphorus as orthophosphate in water was determined by a spectrophotometric method involving flow injection coupled with solvent extraction. The ion associate formed between molybdophosphate and Malachite Green was extracted into benzene-4-methylpentan-2-one (1 + 2 V/V) and the absorbance was measured at 630 nm. The carrier stream was 0.005 M sulphuric acid and the reagent stream contained ammonium molybdate, Malachite Green and sulphuric acid. A newly designed phase separator was used to separate the organic phase. The sampling rate was 40 samples per hour. Calibration graphs were linear below 30 ng ml–1 and below 1 µg ml–1 of phosphorus on injecting samples of 300 and 10 µl, respectively. The detection limit was 0.1 ng ml–1 of phosphorus. Phosphorus in river water was determined satisfactorily by the proposed method.

Journal ArticleDOI
01 Jan 1987-Analyst
TL;DR: The results obtained for fluorescence measurements of different metallic chelates in micellar media are discussed in this paper, where the general trends of surfactant action were discussed in terms of the type of reagent and surfactants, the solubilisation of the chelated in the micelles, competition and quenching reactions and the formation of new species.
Abstract: The results obtained for fluorescence measurements of different metallic chelates in micellar media are discussed. AlIII, NbV and TaV complexes with flavonols, 8-hydroxyquinoline derivatives, azo dyes and anthracene derivatives are readily solubilised and they fluoresce in aqueous micellar solutions of different surfactants. The general trends of surfactant action are discussed in terms of the type of reagent and surfactant, the solubilisation of the chelates in the micelles, competition and quenching reactions and the formation of new species. As a result of the observations reported, these fluorimetric and phosphorimetric reactions could be utilised for the determination of a wide variety of metals.

Journal ArticleDOI
01 Jan 1987-Analyst
TL;DR: In this paper, a microwave digestion technique for the dissolution of peat is described and compared with a dry ashing method and a nitric-perchloric-hydrofluoric acid wet digestion.
Abstract: A microwave digestion technique for the dissolution of peat is described and compared with a dry ashing method and a nitric-perchloric-hydrofluoric acid wet digestion. Peat samples with different organic matter contents were used and Ca, Mg, Fe, Al, Na, K, Mn, Zn, Cu and Li were determined by atomic absorption spectrometry. The results obtained using the three dissolution techniques were in good agreement. The microwave method has the advantage of digesting the samples in less than 2 h and uses less acid than the conventional wet digestion method. Keeping the volume of the acid mixture as small as possible minimises contamination and leads to lower blank values.

Journal ArticleDOI
01 Jan 1987-Analyst
TL;DR: Plasma and saliva concentration-time profiles were determined in two healthy volunteers after the administration of artemisinine and the recovery and relative standard deviation were >95% and 1.2–18%, respectively.
Abstract: A liquid chromatographic method for the determination of artemisinine in human plasma and saliva is described. Artemisinine was extracted from plasma and saliva samples with ethyl acetate and then converted to a strongly UV-absorbing compound, Q260, by a known pre-column reaction. The samples were chromatographed on a C18 column with a 0.010 M NaH2PO4-Na2HPO4 buffer solution (water-methanol = 6 + 4) as the mobile phase. The purity and identity of the peaks of interest were examined. The detection limit of artemisinine in plasma and saliva was about 2.5 ng ml–1. Over the concentration range 10–1000 ng ml–1, the recovery and relative standard deviation were >95% and 1.2–18%, respectively. Plasma and saliva concentration-time profiles were determined in two healthy volunteers after the administration of artemisinine.

Journal ArticleDOI
01 Jan 1987-Analyst
TL;DR: In this paper, the effects of temperature, pH and the presence of oxygen on the stability of arsenic(III) in interstitial water samples from Lake Ohakuri sediments have been studied.
Abstract: The effects of temperature, pH and the presence of oxygen on the stability of arsenic(III) in interstitial water samples from Lake Ohakuri sediments have been studied. The most effective means of preserving a sample with 1–4 µg ml–1 of arsenic(III) for up to 6 weeks was found to be by acidifying the sample to pH 2 and refrigerating near 0 °C. In the samples studied, deoxygenation appeared to be unnecessary. However, in the absence of refrigeration, acidified samples were safely stored for up to 2 weeks, provided that they were deoxygenated and in well sealed glass containers. Because of the likely differences in the behaviour of natural water samples, the safest method of preserving arsenic(III) samples is therefore acidification to pH 2, refrigeration and deoxygenation.

Journal ArticleDOI
01 Jan 1987-Analyst
TL;DR: In this article, an indicator dye reagent for the development of fiber optic probes for detecting ammonia vapour has been investigated and the indicator dye was immobilised on a hydrophilic polymer matrix and the concentration of ammonia in the vapour phase determined in the range 15 × 10−3−60 × 10 −3 mol l 1 by reflectance measurements.
Abstract: The immobilisation of an indicator dye reagent for the development of fibre optic probes for detecting ammonia vapour has been investigated The indicator dye reagent bromothymol blue was immobilised on a hydrophilic polymer matrix and the concentration of ammonia in the vapour phase determined in the range 15 × 10–3–60 × 10–3 mol l–1 by reflectance measurements Some possible interferences from other vapours were also investigated

Journal ArticleDOI
01 Jan 1987-Analyst
TL;DR: A procedure for the spectrophotometric determination of trace amounts of phenols in natural and waste waters is proposed, based on the reaction of the phenols with iodine monobromide, followed by extraction of the products with cyclohexane.
Abstract: A procedure for the spectrophotometric determination of trace amounts of phenols in natural and waste waters is proposed. The method is based on the reaction of the phenols with iodine monobromide, followed by extraction of the products with cyclohexane. Beer's law is obeyed in the range 8–160 p.p.b. for phenol, with a limit of detection of 1.1 p.p.b. without previous distillation. The method can also be used to determine p-substituted phenols and chlorophenols.

Journal ArticleDOI
01 Jan 1987-Analyst
TL;DR: In this article, l'echantillonnage, le choix et l'optimisation des conditions experimentales, le traitement des donnees, and l'importance des parametres analytiques are discussed.
Abstract: Article synthese a 229 references, portant sur l'echantillonnage, le choix et l'optimisation des conditions experimentales, le traitement des donnees, et l'importance des parametres analytiques


Journal ArticleDOI
01 Jan 1987-Analyst
TL;DR: In this paper, the application of ICP-MS to the determination of lead isotope ratios in geological materials is described and data presented for a series of lead mineral concentrates are compared with reference values obtained by conventional solid source thermal ionisation mass spectrometry.
Abstract: The application of ICP-MS to the determination of lead isotope ratios in geological materials is described. Data presented for a series of lead mineral concentrates are compared with reference values obtained by conventional solid source thermal ionisation mass spectrometry. The simultaneous determination of lead isotope ratios and trace elements is carried out in a rapid analysis mode. The application of an electrothermal vaporisation technique for small solution aliquots is described. Lead isotope ratio data for the United States Geological Survey standard reference silicate rock BCR-1, obtained without separation of lead from the matrix, are compared with previously published values obtained after separation.

Journal ArticleDOI
01 Jan 1987-Analyst
TL;DR: A reduction mechanism for the nitrofuran derivatives is suggested, in which the importance of the homogeneous chemical reactions associated with the electron-transfer steps is examined.
Abstract: In pyridine-formic acid buffer and tetramethylammonium chloride solution of pH 4.5 at a dropping mercury or a glassy carbon electrode, nitrofurazone, furazolidone and nitrofurantion are reduced in a single six-electron wave, while chloramphenicol and other structurally related nitro derivatives are reduced in only one four-electron wave, the nitro group being reduced to the amine or to the hydroxylamine, respectively. The electrochemical behaviour of these compounds depends mainly on the nature and position of the substituents. Reduction to the primary amine occurs when the substituents possess available π electrons to conjugate with the nitro group of the aromatic ring, which determines the transformation of the hydroxylamine into the amine via formation of a highly reducible intermediate imine or a quinonoid structure. In contrast, if the formation of the intermediate imine is made impossible by an adverse effect of the substituent, the hydroxylamine does not undergo further reduction.Cyclic voltammograms were recorded at different pH values and at different scan rates in order to identify certain relatively unstable species. The effect of pH on the diffusion-limited current and on the E½ values of the polarographic waves was also studied and the results obtained were compared with those obtained by cyclic voltammetry.On this basis, and according to the polarographic and cyclic voltammetric data, a reduction mechanism for the nitrofuran derivatives is suggested, in which the importance of the homogeneous chemical reactions associated with the electron-transfer steps is examined.

Journal ArticleDOI
01 Jan 1987-Analyst
TL;DR: The previously optimised HPLC method described in Part 1 was applied to the analysis of some Irish-brewed beers and indicated that electrochemical detection was more suitable than UV detection with respect to sensitivity and selectivity.
Abstract: The previously optimised HPLC method described in Part 1 was applied to the analysis of some Irish-brewed beers. The results indicated that electrochemical detection was more suitable than UV detection with respect to sensitivity and selectivity.

Journal ArticleDOI
01 Jan 1987-Analyst
TL;DR: The electrochemical detector offered lower limits of detection for most of the phenolic compounds studied and, in addition, was found to offer better stability for the determination of concentrations in the 0.1–10.0 p.p.m. range.
Abstract: The cyclic voltammetric behaviour of five benzoic acid derivatives, gallic acid, protocatechuic acid, p-hydroxybenzoic acid, vanillic acid and syringic acid, four cinnamic acid derivatives, caffeic acid, p-coumaric acid, ferulic acid and sinapic acid, and two flavanols, (+)-catechin and (–)-epicatechin, commonly found in beers has been studied at a glassy carbon electrode. This study was used to optimise the conditions for the electrochemical detection of these compounds following high-performance liquid chromatographic (HPLC) separation. The HPLC method described is a modification of a previously described method and was optimised with respect to gradient profile, mobile phase composition and mobile phase flow-rate. A comparison was made between an ultraviolet detector and the electrochemical detector operated in series. In general, the electrochemical detector offered lower limits of detection for most of the phenolic compounds studied and, in addition, was found to offer better stability for the determination of concentrations in the 0.1–10.0 p.p.m. range.

Journal ArticleDOI
01 Jan 1987-Analyst
TL;DR: This improved method can more accurately distinguish NOC from most other TEA-responsive species and is found to be rapid, reproducible and sensitive.
Abstract: A procedure for the determination of total N-nitroso compounds (NOC) in human gastric juice was developed by modifying earlier methods. The gastric juice sample, treated with sulphamic acid to remove nitrite, is injected directly into refluxing ethyl acetate containing either acetic acid for determining thermo-and acetic acid labile thermal energy analyser (TEA) responsive compounds (TAC), or into hydrogen bromide for the determination of TAC and NOC. The nitric oxide (NO) levels released are measured using thermal energy analysis with chemiluminescence detection, and the difference between the two determinations represents the concentrations of NOC in gastric juice. This method is not affected by nitrate concentrations of up to 1000 µmol l–1.The method was found to be rapid, reproducible and sensitive (detection limit 0.02 µmol l–1 NOC), requiring only small volumes of gastric juice and no prior extraction. Because the difficulties arising from the system response to the denitrosating agent and variability of NO release by acetic acid from nitrite were eliminated, this improved method can more accurately distinguish NOC from most other TEA-responsive species. Suitable techniques for stabilising gastric juice samples from duodenal ulcer and atrophic gastritis patients and the influence of the time and storage conditions on NOC concentrations have been studied.

Journal ArticleDOI
01 Jan 1987-Analyst
TL;DR: Thiosulphate, a reducing agent for arsenate, was added to water samples, and the absorbance of the solution, A(P), was measured as described above.
Abstract: A simple and rapid method for the determination of trace amounts of phosphate and arsenate in water is proposed. Molybdophosphate-and molybdoarsenate-Malachite Green aggregates, formed by reaction of a reagent consisting of a mixed solution of ammonium molybdate and Malachite Green, were selectively collected on a nitrocellulose membrane filter (pore size 3 µm) and dissolved in methylcellosolve together with the membrane filter. The absorbance (λ= 627 nm), denoted A(P + As), was proportional to the sum of the concentrations of phosphate and arsenate with a molar absorptivity of 2.7 × 105 l mol–1 cm–1. Thiosulphate, a reducing agent for arsenate, was added to water samples, and the absorbance of the solution, A(P), was measured as described above. The absorbance A(P) corresponds to the concentration of phosphate alone. The difference, A(P + As)–A(P), then corresponds to the arsenate concentration. The proposed method makes it possible to determine phosphate and arsenate at levels ranging from 0.3 to 150 p.p.b.

Journal ArticleDOI
01 Jan 1987-Analyst
TL;DR: The proposed HPLC method is suitable for the determination of these active ingredients in pharmaceutical preparations such as multivitamin capsules and has a coefficient of variation between 1.1 and 3.2%.
Abstract: An ion-pair reversed-phase high-performance liquid chromatographic (HPLC) method for the separation and simultaneous determination of thiamine HCl (vitamin B1), riboflavin (vitamin B2), nicotinamide, pyridoxine HCl (vitamin B6), cyanocobalamin (vitamin B12), ascorbic acid (vitamin C) and folic acid in capsule preparations is described. The above seven active substances were extracted from the preparations within 5 min using an electronically controlled extraction apparatus. Ion-pair reversed-phase HPLC was carried out on LiChrosorb RP-18 using methanol-water-concentrated phosphoric acid-octanesulphonic acid as the eluent. All seven active ingredients were separated in less than 4 min. The detection limits were 1–2 ng for all vitamins; however, amounts of 5–10 ng were required for the quantitative HPLC determination of the vitamins. The proposed HPLC method is suitable for the determination of these active ingredients in pharmaceutical preparations such as multivitamin capsules and has a coefficient of variation between 1.1 and 3.2%. The ease of extraction, accuracy and sensitivity of the method and the time required for analysis are emphasised.

Journal ArticleDOI
01 Jan 1987-Analyst
TL;DR: In this paper, a procedure for the determination of tributyltin ions (TBT) in estuarine waters is described, where TBT was quantitatively retained from 100-500 ml of sample on a 4 cm long ODS column.
Abstract: A procedure is described for the determination of tributyltin ions (TBT) in estuarine waters. TBT was quantitatively retained from 100–500 ml of sample on a 4 cm long ODS column. After washing off the salts with 20 ml of distilled water the ODS column was back-flushed with methanol-water (80 + 20) containing 0.15 M ammonium acetate, on to a 25 cm long Partisil SCX analytical column. The eluent from the column (1 ml min–1) was mixed with a fluorimetric reagent (acetic acid, 0.01 M; morin, 0.0025%m/V; Triton X-100, 0.7%m/V)(2.5 ml min–1) for detection at 534 nm with excitation at 408 nm. The detection limit (2σ) is 16 ng of TBT (as Sn). The method has been applied to some local estuarine samples.