Forgot your password?
New user?
New Window Opens on the Secret Life of Microbes: Scientists Develop First Microbial Profiles of Ecosystems
CAS announces the release of SciFinder Scholar for Mac OS X
Press Releases
Press Releases
| Check out our New Publishers' Select for Free Articles |
Analytical and Bioanalytical Chemistry (v.373, #4-5)
No Title by Kinuko Ogawa; Daniela Stöllner; Frieder Scheller; Axel Warsinke; Fumimasa Ishimura; Wakako Tsugawa; Stefano Ferri; Koji Sode (pp. 211-214).
An enzyme-sensor system with flow-injection analysis (FIA) has been developed for the detection of fructosyl amine compounds; the sensor utilizes fructosyl amine oxidase isolated from the marine yeast Pichia sp. N1-1 strain. With this FIA system 0.2 to 10 mmol L–1 fructosyl valine can be determined. The sensor is approximately five times more sensitive to fructosyl valine, a model compound for glycated hemoglobin HbA1c, than to N ε-fructosyl lysine, a model compound for glycated albumin. This FIA system can also be used to detect fructosyl dipeptides. The operational stability of the sensor enabled more than 120 consecutive sample injections over a period of approximately 20 h.
Keywords: Enzyme sensor Glycated hemoglobin Fructosyl amine Fructosyl amine oxidase FIA system
No Title by Youan Mao; Wanzhi Wei; Shufen Zhang; Guangming Zeng (pp. 215-221).
A new method of monitoring drug binding to DNA, in real-time, by means of the piezoelectric quartz-crystal-impedance (PQCI) technique, is proposed. The method was used to monitor the binding of an anticancer drug, mitoxantrone (MX), to double-stranded calf-thymus DNA covalently immobilized on the thioglycollic acid-modified gold electrode surface of a quartz crystal. Optimum experimental conditions for the immobilization were established. The DNA-anchored piezoelectric sensor was in contact with MX solution. The time courses of the resonant frequency and the equivalent circuit characteristics of the sensor were also obtained during the study of DNA–drug binding. On the basis of the analysis of the multidimensional information provided by the PQCI technique the observed frequency decrease was mainly ascribed to the increase in the mass of the sensor surface resulting from the binding. The kinetics of the binding process were studied quantitatively by monitoring the frequency change with time and a piezoelectric response model for the binding was derived theoretically. The experimental data were fitted to the model and the binding and dissociation rate constants and the binding equilibrium constant were estimated to be 66.0±0.1 mol–1 L s–1, 1.4±0.1×10–4 s–1, and 4.71±0.07×105 mol–1 L, respectively, at 37 °C.
Keywords: Binding process Mitoxantrone Surface-immobilized DNA Piezoelectric impedance analysis
No Title by Takashi Masadome; Yasukazu Asano; Toshihiko Imato; Satoshi Ohkubo; Tatsuya Tobita; Hisao Tabei; Yuzuru Iwasaki; Osamu Niwa; Yoshito Fushinuki (pp. 222-226).
In order to simplify the procedure for assembling a surface-plasmon resonance (SPR) sensor, a refractive index matching polymer film was prepared as an alternative to the conventionally used matching oil. The refractive index matching polymer film, the refractive index of which was nearly equal to the prism and sensor chip material (a cover glass) of the SPR sensor, was prepared by casting a tetrahydrofuran solution of poly (vinyl chloride) (PVC) containing equal weights of dioctyl phthalate and tricresyl phosphate. The refractive index matching polymer film was found to have a refractive index of 1.516, which is identical to that of the prism and the cover glass used for the present SPR sensor. The utility of the matching polymer film for the SPR sensor was confirmed by the detection of anti-human albumin, based on an antigen-antibody reaction.
Keywords: Surface-plasmon resonance (SPR) Portable SPR-based chemical sensor Refractive index matching polymer film Anti-human albumin Poly (vinyl chloride) film
No Title by P. Ortega-Barrales; A. Ruiz-Medina; Fernández-de M. Córdova; A. Molina-Díaz (pp. 227-232).
A continuous and simple UV-photometric flow-through optosensor has been developed for the simultaneous determination of a binary mixture of two species with different electric charges present at very different concentrations – ascorbic acid (or acetylsalicylic acid) and thiamine. The sensing device is based on the selective sorption and determination of a cationic analyte on a cation-exchange gel (Sephadex SP-C25) while the other, anionic, analyte is determined in the solution among the interstices of the cation-exchange gel in the same flow cell. The analytes arrive in sequence at the sensing zone, which detects their intrinsic absorbance at 253 nm, as a result of on-line separation by use of a minicolumn filled with the same cation-exchange gel as in the cell, and placed before the flow cell. Thiamine is retained in the minicolumn whereas ascorbic acid or acetylsalicylic acid pass through it and produce their signal as a result of absorbance in the interstitial solution among the resin beads. Thiamine is then eluted from the precolumn, transported to the flow cell, and temporarily retained in the sensing zone from this eluted solution. Calibration graphs were linear over the range 3–50, 25–400, and 300–3000 µg mL–1 (600 µL sample volume) and the relative standard deviations were 2.56, 1.85, and 1.25 % for thiamine, ascorbic acid, and acetylsalicylic acid, respectively. The proposed method was satisfactorily applied to the determination of binary mixtures of thiamine with ascorbic acid or acetylsalicylic acid in pharmaceutical preparations and semi-synthetic samples.
Keywords: Solid-phase spectrophotometry Flow-through optosensor Ascorbic acid Thiamine Acetylsalicylic acid Pharmaceuticals
No Title by M. Tibben; J. Rademaker-Lakhai; J. Rice; D. Stewart; J. Schellens; J. Beijnen (pp. 233-236).
AP5280 is an N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer to which are linked tetrapeptide side chains containing bioactive platinum complexes at their C-terminal sides. We have developed and validated a rapid and sensitive analytical assay for the determination of total platinum concentrations in plasma, and free platinum of an AP5280 origin in plasma ultrafiltrate (PUF), of subjects dosed with AP5280. The total platinum levels were determined by use of graphite-furnace atomic-absorption spectrometry (GF-AAS) with Zeeman correction after appropriate dilution of the plasma sample with plasma–hydrochloric acid 0.2 mol L–1 (1:5) as diluent. The limit of quantitation of this assay is 0.25 µmol L–1 platinum in plasma. Linear calibration curves were obtained over the concentration range 0.25–5.0 µmol L–1. Accuracy was between 87.7% and 104.2% and precision was 15.3% at the lowest concentration and less than 14% for all other levels tested. Accuracy and precision were thus in accordance with generally accepted criteria for analytical methods. Analysis of samples obtained from patients receiving AP5280 demonstrated the applicability of the described assay.Analysis of free platinum in PUF was performed by use of a previously validated and reported assay from our institute in which the same instrumental method is used.
Keywords: AP5280 GF-AAS HPMA Platinum
No Title by Dimosthenis L. Giokas; Evangelos K. Paleologos; Miltiades I. Karayannis (pp. 237-243).
A method has been developed for the simultaneous determination of traces of Fe(III) and Fe(II) in water by on-line coupling of spectrophotometry with flame atomic absorption spectrometry (FAAS). The method involves cloud-point extraction (CPE) of both species with ammonium pyrrolidinecarbodithioate (APDC) under standard conditions, which facilitates the in situ complexation and extraction of both species. Differentiation of the oxidation states of iron is achieved by using mathematical equations to overcome the interference of Fe(III) in the spectrophotometric determination of Fe(II) when they are both present in the same solution. In this manner the time-consuming and labor-intensive steps of preoxidation of Fe(II) or reduction of Fe(III) are eliminated. By preconcentrating a 10-mL sample solution detection limits as low as 7 µg L–1, were obtained after a single-step extraction procedure. The relative standard deviation (n=4, 30 µg L–1) was 2.6 % and 1.8 % for spectrophotometry and FAAS, respectively. Recoveries in the range of 96–105 % were obtained by analysis of spiked real samples. The method was further verified by analyzing a certified reference material (IMEP-9); for this the recovery was 98.5 %.
Keywords: Iron speciation Cloud-point extraction Ferrozine method Spectrophotometry Atomic absorption spectrometry
No Title by Ana Cabañero; Yolanda Madrid; Carmen Cámara (pp. 244-250).
The diatomaceous earth (DE) has an important ability to retain metals such as Cd, Cr, Mn and Pb, which can be used for their stabilization in the environment and for analytical purposes. In this paper a fast on-line preconcentration method for the determination of Cr and Pb in waters by flow injection flame atomic absorption spectrometry is described. Preconcentration was based on the retention of Cr and Pb on a DE immobilized in silica gel at pH 3.0 and subsequent elution with 200 µL of 3 mol L–1 HCl. The preconcentration factors were 100 and 150 for Pb and Cr respectively, for 16 mL water sample volume. The detection limits under these conditions were 3 ng mL–1 and 1 ng mL–1 for Pb and Cr, respectively. The stability of Cr and Pb retained on silica gel-DE columns was established. Silica gel-DE microcolumns with the retained analytes were stored for 2 months at two different temperatures: 4°C and room temperature. At regular time intervals, both metals were eluted and quantified. The results showed the potential of the procedure for sampling and storing water samples for subsequent metal determination, avoiding the problems associated with maintaining species integrity in aqueous solution, and the possibility to of decontaminating polluted spaces.
Keywords: Diatomaceous earth Lead Chromium Flow injection flame atomic absorption spectrometry Preconcentration
No Title by I. Durán Merás; A. Espinosa Mansilla; F. Salinas López; M. Rodríguez Gómez (pp. 251-258).
Binary mixtures of methotrexate (MTX) and leucovorin (LV) have been resolved by application of first-derivative spectrophotometry and partial least squares calibration (PLS-1). By measuring the first-derivative signals of MTX and LV at 354 and 300 nm, respectively, simultaneous determination was possible. The mean recoveries for urine samples were 91 and 96% for MTX and LV, respectively. Partial least squares (PLS-1) multivariate calibration has been applied to the determination of these compounds in serum and in urine without pretreatment of the samples. The absorption spectra of serum or urine samples spiked with methotrexate and/or leucovorin, were used to optimize the calibration matrixes by the PLS-1 method. The sensitivity and selectivity of the proposed procedures were calculated. Mean recoveries were 101 and 97% for MTX and LV, respectively, for serum samples, and 101 and 98% for MTX and LV, respectively, for urine samples.
Keywords: Methotrexate Leucovorin Derivative spectrophotometry Multivariate calibration PLS-1 Serum Urine
No Title by Victoria Ruiz-Calero; Javier Saurina; Teresa M. Galceran; Santiago Hernández-Cassou; Lluis Puignou (pp. 259-265).
A multivariate calibration method for the characterization of heparin samples based on the analysis of 1H nuclear magnetic resonance (NMR) spectral data is proposed. Heparin samples under study consisted of two-component or four-component mixtures of heparins from porcine, ovine and bovine mucosae and bovine lung. Although the 1H NMR spectra of all heparin types were highly overlapping, each origin showed some particular features that could be advantageously used for the quantification of the components. These features mainly concerned the anomeric H, which appeared in the range 5.0–5.7 ppm and the peaks of acetamidomethyl protons at 2.0–2.1 ppm. The determination of the percentage of each heparin class depended on these differences and was carried out using partial least squares regression (PLS) as a calibration method. Prior to the PLS analysis, the spectral data were standardized using the internal standard peak (sodium 4,4-dimethyl-4-silapentanoate-2,2,3,3-d 4 , TSP) as the reference. The quantification of each heparin type in the samples using PLS models built with 4 or 5 components was satisfactory, with an overall prediction error ranging from 3% to 10%.
Keywords: Heparin Nuclear magnetic resonance Partial least squares regression Principal component analysis
No Title by Christian K. Riener; Gerald Kada; Hermann J. Gruber (pp. 266-276).
Since its introduction in 1959, Ellman's reagent (5,5′-dithio-bis(2-nitrobenzoic acid)) has been the favorite reagent for spectrophotometric measurement of protein sulfhydryls. Meanwhile however, evidence has accumulated that many protein sulfhydryls give an incomplete reaction with Ellman's reagent, even during prolonged assay times. In the present study, the kinetic problem was solved by including cystamine as a "mediator" between the protein sulfhydryl and Ellman's reagent, as previously applied in an enzymatic thiol assay [9]. As an alternative, 4,4′-dithiodipyridine (DTDP) was used in place of Ellman's reagent. Due to its small size, amphiphilic nature, and lack of charge, DTDP quickly reacts with poorly accessible protein sulfhydryls, without any catalysis by cystamine. The DTDP method and the Ellman/cystamine method were both optimized for maximal sensitivity, minimal sample consumption (detection limit 0.2 nmol mL–1, determination limit 0.6 nmol mL–1), and minimal assay time (5 min). In validation experiments, both methods gave identical results and the measured sulfhydryls/protein matched the expected values. Electronic supplementary material to this paper can be obtained by using the Springer Link server located at http://dx.doi.org/10.1007/s00216-002-1347-2.
Keywords: Thiol Mercaptan Assay Ellman's reagent 4,4′-Dithiodipyridine
No Title by Manuel Chicharro; Antonio Zapardiel; Esperanza Bermejo; Mónica Moreno; Elena Madrid (pp. 277-283).
Cobalt-phthalocyanine-modified carbon paste electrodes are shown to be excellent indicators for electrocatalytic amperometric measurements of triazolic herbicides such as amitrole, at low oxidation potentials (+0.40 V). The detection and determination of amitrole in flow injection analysis with a modified carbon paste electrode with Co-phthalocyanine is described. The concentrations of amitrole in 0.1 M NaOH solutions were determined using the electrocatalytic oxidation signal corresponding to the Co(II)/Co(III) redox process. A detection limit of 0.04 µg mL–1 (4 ng amitrole) was obtained for a sample loop of 100 µL at a fixed potential of +0.55 V (vs. Ag/AgCl) in 0.1 M NaOH and a flow rate of 4.0 mL min–1. Furthermore, the modified carbon paste electrodes offers reproducible responses in such a system, and the relative standard deviation was 3.3% using the same surface, 5.1% using different surface, and 6.9% using different pastes. The performance of the cobalt-phthalocyanine-modified carbon paste electrodes is illustrated here for the determination of amitrole in commercial formulations. The response of the electrodes is stable, with more than 80% of the initial retained activity after 50 min of continuous use.
Keywords: Modified carbon paste electrodes Cobalt-phthalocyanine Amitrole Aminotriazole Flow injection analysis
No Title by Cuiling Xu; Kangbing Wu; Shengshui Hu; Dafu Cui (pp. 284-288).
A modified electrode, based on a hexadecane (C16)-coated glassy-carbon electrode (GCE) has been developed for the determination of parathion. The electrochemical behavior of parathion was investigated by cyclic voltammetry (CV). The peak potential and peak current were found to depend on the supporting electrolyte and the pH of the buffer solution. The reduction currents for parathion were proportional to parathion concentration over the range 8×10–8–2×10–5 mol L–1. The detection limit was 2×10–8 mol L–1 parathion for an accumulation time of 30 s. The effects of organic and inorganic species on the determination of parathion were also studied. A procedure was developed to extract parathion from spiked soil samples using a mixture of dichloromethane and acetone as the extraction solvent. The complete extraction and analytical procedure are simple, inexpensive and rapid. Parathion was determined in a soil sample by use of linear scan voltammetry (LSV).
Keywords: Parathion Hexadecane Electrochemical Determination Chemically modified electrode
No Title by L. Capitán-Vallvey; R. Avidad; M. Fernández-Ramos; A. Ariza-Avidad; E. Arroyo (pp. 289-294).
A disposable test strip is proposed for the determination of nitrite in waters. The strip is an inert rectangular strip of polyester with a 6 mm o.d. circular, transparent and colorless film attached to its surface. This film contains the chemicals required for reaction and fixation of the dye formed, sulfanilamide, N-(1-naphthyl)ethylenediamine on Nafion. When the test strip is placed in an acidified (pH 2.0) sample solution containing nitrite a red–violet color develops; the absorbance of this is measured at 536 nm. The linear range of the method depends on the time of equilibration of the test strip with the sample solution. When the equilibration time was 45 min, the linear range was 8.9–500 µg L–1 whereas for an equilibration time of 60 min it was 4.7–200 µg L–1. The detection limit was 1.4 µg L–1 for an equilibration time of 60 min. The precision of the method, expressed as RSD, was 8.8 % at 100.0 µg L–1. The method was applied, and validated chemometrically, for the determination of nitrite in different types of water (spring, mineral, tap, well, and sea).
Keywords: Nitrite determination Test strip Water analysis
No Title by Rodrigo P. Cerejeira; Cristina Delerue-Matos; Carmo M. Vaz (pp. 295-298).
On the basis of its electrochemical behaviour a new flow-injection analysis (FIA) method with amperometric detection has been developed for quantification of the herbicide bentazone (BTZ) in estuarine waters. Standard solutions and samples (200 µL) were injected into a water carrier stream and both pH and ionic strength were automatically adjusted inside the manifold. Optimization of critical FIA conditions indicated that the best analytical results were obtained at an oxidation potential of 1.10 V, pH 4.5, and an overall flow-rate of 2.4 mL min–1. Analysis of real samples was performed by means of calibration curves over the concentration range 2.5×10–6 to 5.0×10–5 mol L–1, and results were compared with those obtained by use of an independent method (HPLC). The accuracy of the amperometric determinations was ascertained; errors relative to the comparison method were below 4% and sampling rates were approximately 100 samples h–1. The repeatability of the proposed method was calculated by assessing the relative standard deviation (%) of ten consecutive determinations of one sample; the value obtained was 2.1%.
Keywords: Amperometry Bentazone FIA system Herbicides Estuarine waters
No Title by B. Nagabhushana; G. Chandrappa; B. Nagappa; N. Nagaraj (pp. 299-303).
The bidentate ligand diformylhydrazine (OHC–HN–NH–CHO), DFH, combines with iron(II) and iron(III) in alkaline media in the pH range 7.3–9.3 to form an intensely colored red–purple iron(III) complex with an absorption maximum at 470 nm. Beer's law is obeyed for iron concentrations from 0.25 to 13 µg mL–1. The molar absorptivity was in the range 0.3258×104–0.3351×104 L mol–1 cm–1 and Sandell's sensitivity was found to be 0.0168 µg cm–2. The method has been applied to the determination of iron in industrial waste, ground water, and pharmaceutical samples.
Keywords: Diformylhydrazine reagent Iron(III)–diformylhydrazine complexes Iron(II) determination Iron(III) determination Spectrophotometry.
No Title by Digambara Patra; A. Mishra (pp. 304-309).
Extending the two-dimensional synchronous fluorescence scan to a three-dimensional total synchronous fluorescence scan (TSFS) spectral measurement gives the total synchronous fluorescence characteristics of a multifluorophoric sample at various possible wavelength intervals (Δλ), which could help to characterize multifluorophoric systems better. TSFS spectra of petroleum products such as diesel, kerosene, petrol, engine oil etc., available in the Indian market, are reported. Fluorescence in these samples is due to the presence of polycyclic aromatic hydrocarbons (PAHs) of various ring sizes. The TSFS contour plot profiles of the neat samples measured at right-angle geometry is a result of various energy-degrading photophysical processes such as inner filter effect, light attenuation, resonance energy transfer, collisional quenching etc. TSFS plots make it easy to obtain the optimized Δλ of an unknown sample of analytical interest. TSFS and the excitation-emission matrix (EEM) techniques are similar, but the contour profiles generated are different. The response of the TSFS contour profiles to dilution is different from that in the EEM contour profiles. Thus, TSFS can provide an alternative way of presenting the fluorescence response of concentrated multifluorophoric samples.
Keywords: Total synchronous fluorescence scan TSFS EEM Petroleum products Fluorescence
No Title by Nadica Todorovska; Irina Karadjova; Trajče Stafilov (pp. 310-313).
Methods for the direct determination of Ni in human blood serum and urine by electrothermal atomic absorption spectrometry (ETAAS) are described. Hydrogen peroxide was proposed as matrix modifier, assisting thermal decomposition of proteins during the ashing step. A pyrolysis temperature of 1,200 °C was found to be optimal while 2,100 °C and 2,200 °C were found to be optimal atomizing temperatures for Ni in serum and urine respectively. Calibration was performed by using a calibration curve prepared with aqueous standard solutions of Ni (glycine must be used as modifier for Ni in aqueous solutions). The limits of detection, defined as the blank values plus 3 times the standard deviation of the blank values, were 0.2 µg/L for both serum and urine samples. Relative standard deviations for serum samples with concentrations of Ni in the range 0.5–2 µg/L were 10–15% and for urine samples with Ni concentrations in the range 0.5–2.5 µg/L were 8–10%.
Keywords: Nickel Serum Urine Electrothermal atomic absorption spectrometry Determination
No Title by Hong Chen; Yong Zeng; Bi-Feng Liu; Dai-Wen Pang; Jie-Ke Cheng (pp. 314-317).
In microchip-based capillary electrophoresis, the resolution and separation efficiency of small peptides and amino acids can be noticeably improved by adding a low molecular weight (30,000) soluble polymer additive, polyvinypyrrolidone in the separation medium. Several separation conditions such as injection time and electrophoretic buffer have been investigated and optimized. Using an electro-stacking scheme, the resolution and separation efficiency of small peptides and amino acids can be enhanced significantly. Under the optimal conditions, the separation of fluorescein isothiocyanate Isomer I-labeled small peptides and amino acids was successfully achieved within 100 s.
Keywords: Microchip-based capillary electrophoresis Small peptides and amino acids Polymer additive