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Analytical and Bioanalytical Chemistry (v.371, #7)
No Title by Heike Holthues; Ursula Pfeifer-Fukumura; Iris Hartmann; Wolfram Baumann (pp. 897-902).
2-Aminobutylamino-4-ethylamino-6-isopropylamino-1,3,5-triazine (ABA–atrazine) has been synthesized and used as a coating hapten in an immunoassay with a monoclonal antibody against terbutryn. Coating was achieved by covalently linking ABA–atrazine to a glutaraldehyde polymer network directly bound to the polystyrene surface of a standard 96-well microtiter plate. The assay was carefully optimized. In particular, the coating hapten concentration had a strong effect on the ELISA sensitivity. By including a pre-incubation step a low test midpoint (IC50-value) of 0.130 µg L–1 was achieved. As far as we are aware this is the most sensitive ELISA for terbutryn yet reported. The coating-hapten-format presented is proposed as generally applicable, because the glutaraldehyde-modified microtiter plate surface enables stable immobilization of a broad variety of coating haptens.
No Title by J. Murillo Pulgarín; A. Alañón Molina; M. Alañón Pardo (pp. 903-908).
Non-protected fluid room temperature phosphorescence, NPRTP, has been applied to the determination of naftopidil in biological fluids. The proposed method is based on obtaining a phosphorescence signal from naftopidil using potassium iodide as heavy atom perturber and sodium sulfite as a deoxygenating reagent without a protected medium.Optimized conditions for the determination were 1.4 mol L–1 KI, 5.0×10–3 mol L–1 sodium sulfite, pH 6.5 (adjusted with sodium hydrogen phosphate–dihydrogen phosphate buffer solution, 5.0×10–2 mol L–1). The delay time, gate time, and time between flashes were 70 µs, 400 µs, and 5 ms, respectively.The maximum phosphorescence signal appeared instantly and the intensity was measured at λex=287 nm and λem=525 nm. The response obtained was linearly dependent on concentration in the range 50 to 600 ng mL–1.The detection limit, according to error-propagation theory, was 7.93 ng mL–1 and the detection limit as proposed by Clayton was 11.12 ng mL–1. The repeatability was studied by using ten solutions of 400 ng mL–1 naftopidil; if the theory of error propagation is assumed the relative error is 0.88%. The standard deviation of replicates was found to be 3.5 ng mL–1. This method was successfully applied to the analysis of naftopidil in human serum and urine with recoveries of 104.0±0.6% for serum and 106.0±1.0% for urine.
No Title by P. Oliveira; E. Oliveira (pp. 909-914).
A study was carried out on the direct determination of Cr and Mn in urine using simultaneous atomic absorption spectrometry (SIMAAS). The heating program conditions, the absorbance signal profiles, the influence of different chemical modifiers, and the urine sample volume delivery into the tube were optimized to perform the calibration with aqueous solutions. Among several chemical modifiers tested, the best recovery and repeatability results were obtained for 3 µg Mg(NO3)2. On using this modifier, the pyrolysis and atomization temperatures for simultaneous determination of Cr and Mn were 1300 °C and 2500 °C, respectively. Urine samples were diluted (1+1) with 2.0% (v/v) HNO3 + 0.05% (w/v) Triton X-100 prepared in high purity water. A 20-µL aliquot of analytical solution and 10 µL of chemical modifier solution were delivered to the graphite tube. The characteristic masses were 7.8 pg for Cr (RSD=4.0%) and 4.6 pg for Mn (RSD=2.6%). The limits of detection were 0.08 µg L–1 (n=20, 3s) for Cr and 0.16 µg L–1 (n=20, 3s) for Mn. Recovery studies for 1.0 or 2.5 µg L–1 of Cr and Mn added to different urine samples showed acceptable results for Cr (100%, RSD=14%) and Mn (88%, RSD=5.6%).
No Title by F. Vanhaecke; G. De Wannemacker; L. Moens; P. Van den haute (pp. 915-920).
Rb–Sr dating, one of the most important tools in geochronology, requires determination of the Rb/Sr concentration ratios and the 87Sr/86Sr isotope ratios in co-genetic minerals or rocks and is traditionally performed by thermal ionization mass spectrometry (TIMS). In this work we investigated whether sector field inductively coupled plasma mass spectrometry (ICP–MS), which is characterized by a high sample throughput and straightforward sample introduction, could be used as an alternative to TIMS.To avoid spectral overlap of the ion signals of the isobaric nuclides 87Sr and 87Rb, Sr was separated from Rb by cation-exchange chromatography. A mathematical correction was applied to take into account the small amount of Rb that can be present in the Sr fraction. The isotope ratio accuracy and precision attainable with ICP–MS were evaluated by analysis of several reference materials from the US Geological Survey. The results of this evaluation show that excellent accuracy could be achieved; the internal precision (repeatability) of the isotope ratio (expressed as the relative standard deviation for 10 successive 1-min measurements) was 0.04–0.12%. An attempt was made to calculate the total or combined uncertainty on the isotope ratio results, by also taking into account other possible error sources (corrections for mass discrimination, detector dead time, blank signal and Rb fraction).Finally, the same procedure was used for dating two rock formations that were 2500 Ma and 350 Ma old, according to age determinations previously performed by the Rb–Sr laboratory of the University of München (Germany) using TIMS. The ICP–MS results (2520±150 Ma and 379±48 Ma) obtained for these formations compare well with the corresponding TIMS data (2509±120 Ma and 357±25 Ma).
No Title by G. Weber; J. Messerschmidt; A. von Bohlen; F. Alt (pp. 921-926).
The species patterns of nutrient and trace metals (K, Ca, Mg, Mn, Fe, Zn) obtained by extraction of plant roots have been determined as a function of extraction pH in the range 4–9. The extractable metal concentrations were subdivided into low-molecular-weight (<10 kDa) and high-molecular-weight (>10 kDa) metal species by TXRF analysis. Except for pH 9, the low-molecular-weight fraction is predominant. This fraction was further separated by HPLC with AAS detection. It was demonstrated that the nature of the metal species changes dramatically when the extraction pH is changed, especially in the range 9–7. Information about the chemical nature of chromatographically separated metal species is obtained by use of different electrochemical detectors (amperometric detection at a glassy carbon or copper electrode and pulsed amperometric detection) and diode-array UV detection.
No Title by Susanne P. Schwenzer; Caterina E. Tommaseo; Michael Kersten; Thomas Kirnbauer (pp. 927-933).
Since 1886 arsenic has been known to be present as a trace component in the Wiesbaden thermal waters at concentrations of over 100 µg L–1. In this study for the first time molecular level speciation of arsenic was measured both in the water (by HG–AAS) and in well-stone scale deposits (by XANES). Most of the arsenic in the anoxic NaCl-type waters is in the reduced arsenite form. Hydrous ferric oxide (HFO) precipitates in the scale deposits scavenge only the minor dissolved arsenate portion which is, however, accumulated up to 3% w/w. Isothermal precipitation experiments at in-situ temperatures showed a difference between the progress of both arsenic and iron oxidation and precipitation. This can be explained in terms of adsorption of the aqueous arsenite and heterogeneous oxidation on the HFO surface, but subsequently rapid release of the arsenate thereby formed back into the aqueous phase at enhanced temperature and increased pH. Such relatively rapid pseudo-homogeneous arsenite oxidation is too slow to efficiently retard the As(III) load already on the wellhead, but fast enough to prevent arsenic seepage into ground water aquifers.
No Title by Viktor Kanický; Vítězslav Otruba; Jean-Michel Mermet (pp. 934-938).
Infrared laser ablation (IR–LA) has been studied as a sample introduction technique for the analysis of sintered cobalt-cemented tungsten carbide materials by inductively coupled plasma atomic emission spectrometry (ICP–AES). Fractionation of cobalt was observed. Linearity of calibration plots was verified at least up to 15% Ti, 8% Ta, and 3% Nb. Above 1% (m/m) Ti, Ta, and Nb, the repeatability of results was better than 3% R.S.D. The relative uncertainty at the centroid of the calibration line was in the range from ±3% to ±4% for Ti, Ta, and Nb with internal standardization by tungsten and up to ±5% without internal standardization. The limits of detection were 0.004% Ti, 0.001% Ta, and 0.004% Nb. Elimination of the cemented hardmetal dissolution procedure is the main advantage of this method.
No Title by Renate Bastl-Borrmann; Lothar W. Kroh (pp. 939-943).
An enzymatic assay has been developed for the quantitative detection of alkyl polyglycosides after enzymatic hydrolysis with different carbohydrolases. A three-step enzymatic method was used for the quantification of alkyl polyglycosides. In the first step the enzymatic hydrolysis of alkyl polyglycosides was performed with different carbohydrolases, or an acid hydrolysis was used. The second step was quantification of free glucose with an enzyme electrode, which was covered with an immobilized glucose oxidase membrane; glucose was used as standard. The last step was the enzymatic quantification of fatty alcohols, which are the second substrate after enzymatic hydrolysis of alkyl polyglycosides. Surprisingly, the enzyme alcohol dehydrogenase ADH (E.C. 1.1.1.1) from bakers' yeast could efficiently oxidize a wide variety of aliphatic alcohols and had the highest catalytic specificity with short and medium fatty alcohol substrates, including octanol and decanol.
No Title by Michael Krachler (pp. 944-950).
Two electronic moisture analyzers were critically evaluated with regard to their suitability for determining moisture in small amounts (≤200 mg) of various environmental matrices such as leaves, needles, soil, peat, sediments, and sewage sludge, as well as various biological reference materials. To this end, several homogeneous bulk materials were prepared which were subsequently employed for the development and optimization of all analytical procedures. The key features of the moisture analyzers included a halogen or ceramic heater and an integrated balance with a resolution of 0.1 mg, which is an essential prerequisite for obtaining precise results. Oven drying of the bulk materials in a conventional oven at 105 °C until constant mass served as reference method. A heating temperature of 65 °C was found to provide accurate and precise results for almost all matrices investigated. To further improve the accuracy and precision, other critical parameters such as handling of sample pans, standby temperature, and measurement delay were optimized. Because of its ponderous heating behavior, the performance of the ceramic radiator was inferior to that of the halogen heater, which produced moisture results comparable to those obtained by oven drying. The developed drying procedures were successfully applied to the fast moisture analysis (1.4–6.3 min) of certified biological reference materials of similar provenance to the investigated the bulk materials. Moisture results for 200 mg aliquots ranged from 1.4 to 7.8% and good agreement was obtained between the recommended drying procedure for the reference materials and the electronic moisture analyzers with absolute uncertainties amounting to 0.1% and 0.2–0.3%, respectively.
No Title by Noel E. Palmer; Ray von Wandruszka (pp. 951-954).
Dynamic light scattering (DLS) has been used to monitor changes in aggregate sizes of aqueous humic materials as a function of solution properties. Humic and fulvic acids were dissolved at relatively low concentrations (15–30 mg L–1) in solutions of different temperature, cation and ethanol content, and pH. The results could be explained in terms of intramolecular contraction and intermolecular aggregation of humic polymers. The former were prevalent in soil humic acids, and less so in aquatic humic acids and fulvic acids. Increasing the temperature of humic solutions generally led to an increase in particle sizes, which was ascribed to an effect akin to surfactant clouding. The addition of cations led to either contraction or expansion, depending on the charge and concentration of the ion, and the nature of the humic material. Reducing the pH initially caused contraction, followed by growth and precipitation in more highly acidic media.
No Title by I. Arambarri; R. Garcia; E. Millán (pp. 955-960).
An experimental design was developed to obtain a simple procedure for global determination of organic tin compounds in sediment. Sediment was extracted by a two-phase method and tin was determined in the organic extract by electrothermal atomic absorption spectrometry (ETAAS), with palladium as chemical modifier. A Plackett–Burman design for screening and a fractional central composite design (CCD) for optimizing were used for evaluation of the effects of several variables. The results showed that sediment mass, volume and concentration of extracting acid, pyrolysis and atomization temperatures, and modifier concentration affect the determination. Reference material PACS-2 was analyzed to evaluate the procedure. It was possible to extract 82% of the organotin content certified in the reference sediment. The limit of detection (LOD) was 0.08 µg g–1 and the relative standard deviation was 4%. The method was applied to the analysis of estuarine superficial sediments from Gipuzkoa (Spain). The organotin content of these samples ranged from 0.7 to 7.7 µg g–1, as tin, on a dry-weight basis.
No Title by Jianguo Hong; Jürgen Maguhn; Dieter Freitag; Antonius Kettrup (pp. 961-965).
A supercritical fluid extraction cell filled with adsorbent (Carbotrap and Carbotrap C) was used directly as a sampling tube to enrich volatile organic compounds in air. After sampling, the analytes were extracted by supercritical fluid CO2 with methanol as modifier. Collected organic peroxides were then determined by a RP-HPLC method developed and validated previously using post-column derivatization and fluorescence detection. Some volatile organic peroxides were found in indoor air in a new car and a newly decorated kitchen in the lower µg m–3 range. tert-Butyl perbenzoate, di-tert-butyl peroxide, and tert-butylcumyl peroxide could be identified.
No Title by J.-J. Sauvain; Vu T. Duc; C. Huynh (pp. 966-974).
A new method enabling the determination of 15 priority carcinogenic polyaromatic compounds (PAC) proposed by the US National Toxicology Program (NTP) has been developed and applied to diesel exhaust particulates (DEP). The clean-up procedure consists of solid-phase extraction (SPE) and HPLC fractionation on silica phases followed by liquid–liquid extraction and chromatography on a polyvinylbenzene copolymer column. The method gives good recoveries for all PAC studied except dibenzo[a,j]acridine and dibenzo[a,h]pyrene, for which recovery values are below 80%. The use of GC–MS ion trap and its capacity to achieve single-ion storage enhanced the sensitivity of the method, enabling the detection of high-molecular-weight PAH in the low ng g–1 concentration range. Intermediate polarity GC columns, e.g. BPX-50 or equivalent, enabled better separation, when applied to DEP analysis, than the generally used DB-5 apolar phase. This is observed mainly for separation of isomeric compounds belonging to the benzofluoranthene and dibenzopyrene families.The application of this method to DEP sampled from the exhaust of a diesel engine and in confined locations such as a tunnel has shown that all PAH of the NTP list could be detected, except dibenzo[a,h]pyrene. No dibenzacridine or dibenzocarbazole could be detected in such matrices. The method is sufficiently sensitive to be applicable to environmental exposure measurements in occupational health surveys.
No Title by M. Zimpl; M. Kotouček; K. Lemr; J. Veselá; J. Skopalová (pp. 975-982).
The electrochemical behavior of the herbicide chloridazon, I (pyrazon), at different pH is described. The electrode reaction (one wave in acidic media and another in alkaline media), investigated using direct current and pulse voltammetry, controlled–potential coulometry, and HPLC–MS, is a combination of the electroreduction (two-electron in the first step) and a kinetic process as a result of which simple compounds (HCl, NH3) are released and, moreover, a five-membered pyrrole cycle is formed in strongly acid media. Products of the kinetic reaction are further reducible. The dissociation constant of I, pKa=2.96, was found spectrophotometrically. Fast-scan differential pulse voltammetry (FSDPV) was used for determination of I; the detection limit was 2.7×10–8 mol L–1 (0.006 µg L–1) at pH 2.3. Chloridazon was determined in spiked drinking and river water.
No Title by E. Eljarrat; J. Sauló; A. Monjonell; J. Caixach; J. Rivera (pp. 983-988).
An automated clean-up system was evaluated for the simultaneous analysis of polychlorinated dibenzo-p-dioxins (PCDD), dibenzofurans (PCDF), and biphenyls (PCB) in different foods. In addition to the seventeen 2,3,7,8-substituted PCDD/PCDF and four non-ortho PCB, by use of the clean-up system studied, it was possible to collect the eight mono-ortho and two di-ortho PCB and the seven indicator PCB in two separate fractions during the same clean-up run. The study was first performed using standard mixtures containing PCDD, PCDF and PCB, and a certified reference material. The recoveries of the 13C-labeled compounds ranged from 51 to 90%, indicating that the PCDD, PCDF, and PCB clean-up worked satisfactorily. Next, the automated system for PCDD, PCDF, and PCB analysis was evaluated for foods such as milk, egg, meat (beef, chicken, and pork), mussel, and olive oil. The recoveries of the 13C-labeled compounds ranged from 40 to 120% for PCB and from 57 to 113% for PCDD/PCDF, meeting the requirements of well accepted methods. Thus, the automated clean-up system studied is a suitable alternative to conventional clean-up methods.
No Title by R. Lara; R. Wuilloud; J. Salonia; R. Olsina; L. Martinez (pp. 989-993).
An on-line cadmium preconcentration and determination system implemented with inductively coupled plasma optical emission spectrometry (ICP-OES) associated to flow injection (FI) with ultrasonic nebulization system (USN) was studied. The cadmium was retained as the cadmium-2-(5-bromo-2-pyridylazo)-5-diethylaminophenol, Cd-(5-Br-PADAP), complex, at pH 9.5. The cadmium complex was removed from the knotted reactor (KR) with 3.0 mol/L nitric acid. A total enhancement factor of 216 was obtained with respect to ICP-OES using pneumatic nebulization (12 for USN and 18 for KR) with a preconcentration time of 60 s. The value of the detection limit for the preconcentration of 5 mL of sample solution was 5 ng/L. The precision for 10 replicate determinations at the 5 µg/L Cd level was 2.9% relative standard deviation (RSD), calculated from the peak heights obtained. The calibration graph using the preconcentration system for cadmium was linear with a correlation coefficient of 0.9998 at levels near the detection limits up to at least 1000 µg/L. The method was successfully applied to the determination of cadmium in wine samples.
No Title by Christoph von Holst; Anne Müller (pp. 994-1000).
Analytical methodology currently employed for the determination of seven indicator PCBs in three compound feeds and fish meal has been evaluated in a collaborative study. The majority of the obtained relative standard deviations of the PCBs varied from 20 to 30%. On assuming a target relative standard deviation of 22% for the analytical results, statistical evaluation showed that about 80% of the participating laboratories delivered data within an acceptable range of ±44% of the assigned concentration in the test materials. However, between 10 and 20% of the participating laboratories reported unacceptable results. Major problems seemed to arise from insufficient separation of PCB congeners, low extraction efficiency, and calculation errors. Correct identification of the target PCB congeners was a prevalent problem if only one capillary column in combination with an electron capture detector (ECD) was employed. The correct preparation of the calibration solution by the laboratories turned out to be only a minor problem. The laboratories participating in this study employed quite different techniques at all stages of the analytical procedure. Principal component analysis indicated that laboratories using an internal standard tended to report higher values for the target analytes. If the PCB concentrations were related to the fat content of the sample, the variability of the reported results decreased for compound feed but increased for fish meal. These inconsistent results are probably due to the fact that fat is not an objective parameter but is defined by the analytical technique employed. It is assumed that harmonizing analytical methods for the determination of this parameter could improve the precision of the PCB results.
No Title by N. García-Villar; J. Saurina; S. Hernández-Cassou (pp. 1001-1008).
A potentiometric sensor array has been developed for the determination of lysine in feed samples. The sensor array consists of a lysine biosensor and seven ion-selective electrodes for NH4 +, K+, Na+, Ca2+, Mg2+, Li+, and H+, all based on all-solid-state technology. The potentiometric lysine biosensor comprises a lysine oxidase membrane assembled on an NH4 + electrode. Because the selectivity of the lysine biosensor towards other cation species is not sufficient, there is severe interference with the potentiometric response. This poor selectivity can be circumvented mathematically by analysis of the richer information contained in the multi-sensor data. The sensor array takes advantage of the cross-selectivity of lysine for each electrode, which differs from the other species and quantification of lysine in complex feed sample extracts is accomplished with multivariate calibration methods, such as partial least-squares regression. The results obtained are in a reasonable agreement with those given by the standard method for amino acid analysis.
No Title by G. Andreev; B. Schrader; H. Schulz; R. Fuchs; S. Popov; N. Handjieva (pp. 1009-1017).
Non-destructive analysis of natural substances in plants as well as of old dyed textiles by Raman spectroscopy has not been possible using conventional techniques. Exciting lines from the visible part of the spectrum produced photochemical and thermal decomposition of the objects as well as strong fluorescence. Using Nd:YAG laser excitation at 1064 nm together with a special sample arrangement and interferometric recording, various polyacetylenes in Aethusa cynapium and in chamomile (Chamomilla recutita) and the main valuable substances in gentian species (Gentiana lutea and G. punctata), curcuma roots (Curcuma longa), cinnamon (Cinnamomum zeylanicum), fennel (Foeniculum vulgare), clove (Caryophyllus aromaticus), and ginger (Zingiber officinale) were analyzed non-destructively and discussed in comparison with the corresponding pure standard compounds. We further analyzed non-destructively the FT Raman spectra of collections of historical textiles and lakes used for dyeing. It is possible to distinguish the main dye component non-destructively by using Raman bands.
Keywords: FT Raman spectroscopy Raman spectra of plants Polyacetylenes in plants Historical textiles Lake dyes
No Title by G. Andreev; B. Schrader; R. Boese; P. Rademacher; L. von Cranach (pp. 1018-1022).
Using an improved sampling arrangement we observed the FT Raman spectra of the different phases of a 'jumping crystal', an inositol derivative. The phase transition produced – as consequences of large changes of the unit cell constants – changes in frequency and intensity mainly of CH deformation vibrations. Photochemical reactions, usually produced with light quanta in the visible range, are not activated with the quanta from the Nd:YAG laser at 1064 nm. The Raman spectra of the 'dark' form of a dinitrobenzyl pyridine and afterwards the 'light' form, the product of its illumination in the visible range, were recorded. We could not observe changes of most bands, especially not of the NO2-vibrations; however, a new strong band appeared at 1253 cm–1, which may be due to the expected NH-photo-isomer. Genuine gemstones and fakes can be unambiguously identified by FT Raman spectroscopy. This is especially useful for the stones whose physical properties are quite similar to those of diamonds – moissanite and zirconia. The quality of diamonds can be estimated from relative band intensities; however, this is not in complete agreement with the internationally accepted visual qualification. Synthetic diamonds produced by CVD (chemical vapor deposition) show remarkable differences from natural ones in their FT-Raman spectra.
Keywords: NIR FT Raman spectroscopy Jumping crystals Photosensitive crystals Diamonds Grading of diamonds
No Title by N. Blagojević; V. Kastratović; R. Zejnilović; Ž. Blečić (pp. 1023-1027).
Anodic linear scan voltammetry (ALSV) has been used to determine the content of Pb (up to 3.5 wt%) in a eutectic type of binary Sb-Pb alloy. The effect of type of electrolyte and as well as the rate of the potential change on the dissolution of Pb from this alloy were investigated by ALSV. The method can be used for the determination of low concentrations of Pb in the investigated alloy and well-defined current peaks of Pb dissolution can be detected on the voltammograms. Well-defined linear dependencies between the quantities of electricity under the current peak of Pb dissolution (Q Pb) and the respective contents of Pb (w) in the alloy, so-called "check curves", were found. The smallest ratio of Pb in Sb-Pb alloy which could be detected by ALSV was 0.45 wt%.The dissolution involves only ten atomic layers of the less precious metal (Pb) from the surface of the alloy samples.
No Title by A. Prado; C. Airoldi (pp. 1028-1030).
The herbicide 2,4-dichlorophenoxyacetic acid (2,4-D), chemically anchored to a silica gel surface, was used to adsorb and preconcentrate the same herbicide from aqueous solutions at room temperature. From a series of adsorption isotherms adjusted to a modified Langmuir equation, the maximum number of moles adsorbed was calculated as 4.67×10–5 mol g–1, with the highest retention capacity at pH 5. This modified silica gel was used in a column for preconcentrating trace levels of 2,4-D. The preconcentrated herbicide can be directly eluted with methanol with a recovery efficiency higher than 97%. The concentration factor was 8.33.
No Title by N. Furusawa; K. Kishida (pp. 1031-1033).
A simplified method for routine monitoring of 7 residual sulfonamides (SAs) (sulfadiazine (SDZ), sulfamerazine (SMR), sulfadimidine (SDD), sulfamonomethoxine (SMM), sulfamethoxazole (SMX), sulfadimethoxine (SDM), and sulfaquinoxaline (SQ)) in milk using high-performance liquid chromatography (HPLC) with a photodiode array detector is described. The spiked and blank samples were cleaned up by using an Ultrafree®-MC/PL centrifugal ultrafiltration unit. For determination/identification, a Mightysil® RP-4 GP column and a mobile phase of 25% (v/v) ethanol in water with a photodiode array detector were used. Average recoveries from milk samples spiked with 0.05, 0.1, 0.2, and 0.5 µg mL–1 of each drug were >82%. The inter- and intra-assay variabilities were 2.0–3.1%. The practical detection limits for 7 SAs were 0.005–0.02 µg mL–1. The total time and amount of solvent required for the analysis of one sample were <40 min and <6 mL of ethanol, respectively. No toxic solvents were used.
Determination of proteins by their enhancement of resonance light scattering by fuchsine acid by Cheng Huang; Yuan Li; Ping Feng; Ming Li (pp. 1034-1036).
Based on the measurement of the enhancement of resonance light scattering (RLS) of fuchsine acid (FSA) by proteins, a novel sensitive assay of proteins in body fluid samples has been developed. Proteins, including bovine serum albumin (BSA), human serum albumin (HSA), pepsin (Pep), α-chymotrypsin (Chy), lysozyme (Lys), and cellulase (Cel), can bind to fuchsine acid (FSA), resulting in enhanced RLS signals at 277.0 nm. Linear relationships between the enhanced RLS intensity and the protein concentration were measured at different concentration of FSA, and the limits of detection for BSA, HSA, and Lys were found to lie in the nanogram range.
No Title by Farzaneh Shemirani; Maryam Rajabi (pp. 1037-1040).
A simple and sensitive method has been developed for species selective determination of chromium(III) and chromium(VI) in water by electrothermal atomic absorption spectrometry. The procedure is based on selective absorption of Cr(III) on a cellulose micro column (pH 11, 0.5 mol L–1 NaCl). Total chromium was subsequently determined after appropriate reduction of Cr(VI) to Cr(III). Recoveries of more than 97% were found. A concentration factor of 100 was achieved. The relative standard deviations (n=10) at the 40 ng L–1 level for chromium(III) and chromium(VI) were 2.3% and 1.8% and corresponding limits of detection (based on 3σ) were 1.8 ng L–1 and 5.1 ng L–1, respectively. No interference effects have been observed from other investigated species and the method has been successfully applied to natural water samples.