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Analytical and Bioanalytical Chemistry (v.377, #2)
"A Focus on Bioanalytical Chemistry in Spain" from papers presented to: "Jornadas de Análisis Instrumental (JAI)" 26–29 November 2002, Barcelona, Spain
by Alfredo Sanz-Medel (pp. 234-235).
Trace element speciation by ICP-MS in large biomolecules and its potential for proteomics by Alfredo Sanz-Medel; María Montes-Bayón; María Luisa Fernández Sánchez (pp. 236-247).
Latest studies on the chemical association of trace elements to large biomolecules and their importance on the bioinorganic and clinical fields are examined. The complexity of the speciation of metal-biomolecules associations in various biological fluids is stressed. Analytical strategies to tackle speciation analysis and the-state-of-the-art of the instrumentation employed for this purpose are critically reviewed. Hyphenated techniques based on coupling chromatographic separation techniques with ICP-MS detection are now established as the most realistic and potent analytical tools available for real-life speciation analysis. Therefore, the status and potential of metal and semimetals elemental speciation in large biocompounds using ICP-MS detection is mainly focused here by reviewing reported metallo-complexes separations using size-exclusion (SEC), ion-exchange (IE), reverse phase chromatography (RP) and capillary electrophoresis (CE). Species of interest include coordination complexes of metals with larger proteins (e.g. in serum, breat milk, etc.) and metallothioneins (e.g. in cytosols from animals and plants) as well as selenoproteins (e.g. in nutritional supplements), DNA-cisplatin adducts and metal/semimetal binding to carbohydrates. An effort is made to assess the potential of present trace elements speciation knowledge and techniques for "heteroatom-tagged" (via ICP-MS) proteomics.
Keywords: Trace element speciation ; ICP-MS ; Chromatography ; Large biomolecules ; Biological samples ; Bio-inorganic proteomics
An electronic tongue using potentiometric all-solid-state PVC-membrane sensors for the simultaneous quantification of ammonium and potassium ions in water by J. Gallardo; S. Alegret; R. Muñoz; M. De-Román; L. Leija; P. R. Hernández; M. del Valle (pp. 248-256).
The simultaneous determination of NH4 + and K+ in solution has been attempted using a potentiometric sensor array and multivariate calibration. The sensors used are rather non-specific and of all-solid-state type, employing polymeric (PVC) membranes. The subsequent data processing is based on the use of a multilayer artificial neural network (ANN). This approach is given the name "electronic tongue" because it mimics the sense of taste in animals. The sensors incorporate, as recognition elements, neutral carriers belonging to the family of the ionophoric antibiotics. In this work the ANN type is optimized by studying its topology, the training algorithm, and the transfer functions. Also, different pretreatments of the starting data are evaluated. The chosen ANN is formed by 8 input neurons, 20 neurons in the hidden layer and 2 neurons in the output layer. The transfer function selected for the hidden layer was sigmoidal and linear for the output layer. It is also recommended to scale the starting data before training. A correct fit for the test data set is obtained when it is trained with the Bayesian regularization algorithm. The viability for the determination of ammonium and potassium ions in synthetic samples was evaluated; cumulative prediction errors of approximately 1% (relative values) were obtained. These results were comparable with those obtained with a generalized regression ANN as a reference algorithm. In a final application, results close to the expected values were obtained for the two considered ions, with concentrations between 0 and 40 mmol L−1.
Keywords: Sensor array; PVC membrane; Ion-selective electrode; Artificial neural networks; Ammonium; Potassium
Voltammetric response of diclofenac-molecularly imprinted film modified carbon electrodes by M. Carmen Blanco-López; María-Jesús Lobo-Castañón; Arturo J. Miranda-Ordieres; Paulino Tuñón-Blanco (pp. 257-261).
A voltammetric sensor for the determination of diclofenac was developed, based on the molecular recognition of the analyte by molecularly imprinted methacrylate-ethyleneglycol dimethacrylate co-polymers. Pre-polymerisation solutions were deposited onto the surface of a glassy carbon electrode and a polymer film was obtained after spin coating control of thickness and in situ thermal polymerisation. After the template extraction from the resultant film, re-binding of diclofenac is performed from acetonitrile solutions containing the analyte. The amount of bonded diclofenac was then evaluated by differential pulse voltammetry in different electrolytes. The best results were obtained in 0.025 M citrate solution pH 6 containing 10% of acetonitrile. This medium favours the release of diclofenac from the polymer binding sites. In this way, the voltammetric transduction of the molecular recognition event is achieved. Voltammetric selectivity measurements revealed negligible interferences from diclofenac family of anti-inflammatory drugs, such as niflumic or meclofenamic acids.
Keywords: Molecularly imprinted polymers; Voltammetry; Diclofenac; Voltammetric sensor
Carbon felt electrode design: application to phenol electrochemical determination by direct oxidation by L. Hernández; P. Hernández; V. Velasco (pp. 262-266).
In this paper, electrochemical behaviour of phenol in a carbon felt electrode is studied. An adsorption process on electrode surface that inhibits polymer formation after oxidation of phenol was confirmed. In this work we propose a phenol determination method based on direct electrochemical oxidation on carbon felt electrodes after an accumulation process.
Keywords: Carbon felt electrodes; Phenol oxidation; Environmental pollution measurement
The use of gold bands for flow immunoelectrochemical devices by Eva M. Abad-Villar; M. Teresa Fernández-Abedul; Agustín Costa-García (pp. 267-272).
Gold bands sputtered over a polymeric material, Kapton, have been employed not only for electrochemical detection but also for the development of enzyme immunoassays in a flow system. The immunological interactions on bands acting as reactors are considered for a model analyte, IgM. Different formats of flow immunoassays, competitive and non-competitive, have been checked. Compared with previous results, automation gives rise to in a reduction in analysis time and in reagent consumption. Lower limits of detection are also obtained. Detection, which is also carried out in the flow system, is based on the oxidation of naphthol, the product of the enzymatic hydrolysis of naphthyl-phosphate.
Keywords: Gold bands (films); Enzyme immunoassays; Electrochemical immunoassays; Flow systems
Comparison of biosensors based on entrapment of cholesterol oxidase and cholesterol esterase in electropolymerized films of polypyrrole and diaminonaphthalene derivatives for amperometric determination of cholesterol by J. C. Vidal; E. Garcia-Ruiz; J. Espuelas; T. Aramendia; J. R. Castillo (pp. 273-280).
Cholesterol amperometric biosensors constructed with enzymes entrapped in electropolymerized layers of polypyrrole and poly-naphthalene derivative polymers are compared. The biosensors are based on entrapment of cholesterol oxidase and/or cholesterol esterase in monolayer or multilayer films electrochemically synthesised from pyrrole, 1,8-diaminonaphthalene (1,8-DAN), and 1,5-diaminonaphthalene (1,5-DAN) monomers. Seven configurations were assayed and compared, and different analytical properties were obtained depending on the kind of polymer and the arrangement of the layers. The selectivity properties were evaluated for the different monolayer and bilayer configurations proposed as a function of the film permeation factor. All the steps involved in the preparation of the biosensors and determination of cholesterol were carried out in a flow system. Sensitivity and selectivity depend greatly on hydrophobicity, permeability, compactness, thickness, and the kind of the polymer used. In some cases a protective outer layer of non-conducting poly(o-phenylenediamine) polymer improves the analytical characteristics of the biosensor. A comparative study was made of the analytical performance of each of the configurations developed. The biosensors were also applied to the flow-injection determination of cholesterol in a synthetic serum.
Keywords: Multilayer amperometric biosensor; Enzyme entrapment; Electropolymerization; Polypyrrole; Substituted naphthalene monomers; Cholesterol determination
Determination of albumin in biological fluids by flow injection analysis using the peroxyoxalate chemiluminescent system in micellar medium by L. Gámiz-Gracia; A. M. García-Campaña; F. Alés Barrero; L. Cuadros Rodríguez (pp. 281-286).
A new sensitive analytical procedure for the determination of albumin is presented, based on the participation of a fluorescent derivative of the protein in the peroxyoxalate chemiluminescent system using imidazole as a catalyst. The chemiluminescent emission is detected in a flow injection analysis (FIA) system, employing micellar medium as carrier, whereas the derivatisation reaction is carried out off-line using fluorescamine as a label. The optimisation of the operational and chemical variables of the method such as concentration of reagents, flow-rates, injection volume, etc., involves the use of experimental designs, including Draper–Lin small composite design, scarcely used in analytical chemistry. The performance characteristics were established and a detection limit of about 0.1 fmol of albumin was obtained. The method has been validated and satisfactorily applied to the determination of albumin in human serum and urine.
Keywords: Peroxyoxalate; Chemiluminescence; Flow injection analysis; Albumin; Experimental design
Automated method for the determination of vitamin D3 hydroxymetabolites in serum by J. M. Mata-Granados; A. Caballo-López; M. D. Luque de Castro; J. M. Quesada (pp. 287-292).
An almost automated method for the determination of hydroxymetabolites of vitamin D3 (cholecalciferol) in human serum is reported. The method consists of three steps: 1) a batch liquid–liquid extraction step with 2-propanol and hexane, and drying of the extract and reconstitution with phosphate buffer. 2) A cleanup and preconcentration step based on solid-phase extraction using Prospekt equipment, with CN group cartridges and elution with the chromatographic mobile phase. 3) A chromatographic step for individual separation of the target analytes starting with a 90:10 methanol–water mixture, then a linear gradient to obtain 100% methanol; followed by photometric detection. The method provides a linear range between 1.0 and 100 ng mL−1 for 24,25-(OH)2 vitamin D3 and for 25-(OH)2 vitamin D3, and between 1.5 and 100 ng mL−1 for 1,25-(OH) vitamin D3, with correlation coefficients ranging between 0.993 and 0.987, repeatability between 1.9% and 4.8% and within-laboratory reproducibility between 2.8% and 8.8%.
Keywords: Serum; Prospekt; HPLC; Solid-phase extraction; Hydroxyvitamin D3 metabolites
Partition and location of nimesulide in EPC liposomes: a spectrophotometric and fluorescence study by Helena Ferreira; Marlene Lúcio; Baltazar de Castro; Paula Gameiro; José L. F. C. Lima; Salette Reis (pp. 293-298).
Study of the mechanism of action of anti-inflammatory drugs (NSAIDs) and their side-effects may fall in the domain of membranology. In this work the extent of the interaction between an NSAID (nimesulide) and membrane phospholipids was quantified by the partition coefficient, K p , using egg phosphatidylcholine (EPC) liposomes as cell membrane models. The liposome/aqueous phase partition coefficients were determined under physiological conditions, by derivative spectrophotometry and fluorescence quenching. Derivative spectrophotometry allows elimination of background signal effects (light scattering) due to the presence of liposomes. Theoretical models, accounting for simple partition of the NSAID between two different media, were used to fit the experimental data, allowing the determination of K p in multilamellar vesicles (MLVs) and large unilamellar vesicles (LUVs). The location of nimesulide in MLVs and LUVs was evaluated by fluorescence quenching using spectroscopic probes located at different sites on the membrane. All n-AS probes were quenched and the relative quenching efficiencies were ordered as 2-AS<6-AS≈9-AS<12-AS; this suggests the drug is deeply buried in the membrane. Fluorescence quenching using the 12-AS probe was also used to determine the partition coefficient of the drug in MLVs and LUVs. The two techniques yield similar results. Finally, measurement of zeta-potential in the presence of different concentrations of nimesulide was performed to investigate possible changes in the zwitterionic phosphatidylcholine membranes. The membrane surface potential was not altered, which seems to be an indication that nimesulide binds to lipid bilayer mostly by hydrophobic interactions.
Keywords: Partition coefficient; Nimesulide; Liposomes; Derivative spectrophotometry; Fluorescence quenching
Determination of total homocysteine in human serum by capillary gas chromatography with sulfur-specific detection by double focusing ICP–MS by R. R. de la Flor St. Rèmy; M. Montes-Bayón; A. Sanz-Medel (pp. 299-305).
A selective and sensitive method for determination of total homocysteine (Hcy) in human serum, by gas chromatography coupled to ICP–MS(HR), has been developed. After reduction of the sample with sodium borohydride the liberated Hcy and other aminothiols, such as cysteine (Cys) and methionine (Met), were converted to their N-trifluoroacetyl (TFA)-O-isopropyl derivatives and these were injected into a gas chromatograph equipped with an HP-5 capillary column. Detection was carried out by means of a double-focusing inductively coupled plasma mass spectrometer (DF-ICP–MS) monitoring 32S at m/Δm (resolving power)=3000. The transfer line used to transport the analytes from the GC column to the ICP–MS had previously been developed in our laboratory. The different parameters affecting the derivatisation process were optimised, as were the instrumental operating conditions. This optimised GC–ICP–MS(HR) method was successfully applied to the determination of total homocysteine in human serum—values obtained were in agreement with data reported in the literature. Quantitative recoveries and good precision were obtained for spiked human serum, demonstrating the suitability of the method for quantitative determination of total homocysteine in serum.
Keywords: Homocysteine; Biological thiols; Human serum; Gas chromatography; Double focusing
Liquid chromatography–mass spectrometry approach for the characterization and purification of crude synthetic peptide hormones by Victoria Sanz-Nebot; Fernando Benavente; Isabel Toro; José Barbosa (pp. 306-315).
In this study, conditions for the optimal separation by LC-UV and characterisation by LC-ES-MS of crude mixtures generated during SPPS of several peptide hormones are compiled. The linear solvation energy relationship (LSER) methodology has been used to predict the retention of the target peptides and their side products and then to develop a separation LC methodology with applicability on both the analytical and preparative scale. Identification of these side products by LC-ES-MS analysis has been made on the basis of their calculated molecular masses. This method may be regarded as a key tool for the optimisation of the synthetic procedures and for complying with regulatory agencies' requirements before commercialisation of a safe and effective peptide-based pharmaceutical drug.
Keywords: Linear solvation energy relationship; Liquid chromatography–mass spectrometry; SPPS; Peptides
New methods for acceleration of meat sample preparation prior to determination of the metal content by atomic absorption spectrometry by R. M. García-Rey; R. Quiles-Zafra; M. D. Luque de Castro (pp. 316-321).
Focused microwave-assisted digestion and ultrasound leaching have been applied for the extraction of Pb, Cd, Cr, Cu, Fe, Zn, Ca, and Mg from raw meat. Semimembranous muscle (SM) of raw pig ham was used for optimizing both the digestion and extraction steps by multivariate approaches. The detection and quantification limits were 0.5 and 0.9 μg kg−1 for Pb, 0.06 and 0.1 μg kg−1 for Cd, 0.2 and 1.2 μg kg−1 for Cr, 0.4 and 3 μg kg−1 for Cu, 0.04 and 0.1 mg kg−1 for Fe, 0.012 and 0.017 mg kg−1 for Zn, 0.3 and 0.4 mg kg−1 for Ca, and 0.01 and 0.03 mg kg−1 for Mg. The precision, expressed as relative standard deviation (RSD), ranged between 2.5 and 9.6% for focused microwave-assisted digestion and between 3.5 and 10.6% for ultrasound leaching. The methods were then compared with a reference method and applied to a certified reference material (bovine muscle 184, from the BCR). The t-test, applied to the results obtained from focused microwave-assisted digestion, revealed that they are in agreement (p>0.01) with the certified and estimated values in the case of Pb, Cd, Cr, Cu, Fe, Ca, Mg, and Zn but not in that of Fe. In the case of ultrasound leaching, only the extraction of Pb, Cu, and Ca was quantitative. The method based on microwave digestion provides more accurate and precise results than ultrasound leaching. These new procedures have many advantages with regards to conventional methods, namely, reduction of the extraction time, simplification of the process, avoidance of chemical emissions to the atmosphere, and no losses of metals by volatilization.
Keywords: Meat analysis; Pork; Sample preparation; Focused microwave-assisted digestion; Ultrasound leaching; Metal determination; Atomic absorption spectrometry; Multivariate optimisation
Evaluations of solid electrodes for use in voltammetric monitoring of heavy metals in samples from metallurgical nickel industry by Øyvind Mikkelsen; Silje Marie Skogvold; Knut H. Schrøder; Magne Ivar Gjerde; Thor Anders Aarhaug (pp. 322-326).
Evaluation of different solid electrode systems for detection of zinc, lead, cobalt, and nickel in process water from metallurgical nickel industry with use of differential pulse stripping voltammetry has been performed. Zinc was detected by differential pulse anodic stripping voltammetry (DPASV) on a dental amalgam electrode as intermetallic Ni–Zn compound after dilution in ammonium buffer solution. The intermetallic compound was observed at −375 mV, and a linear response was found in the range 0.2–1.2 mg L−1 (r 2=0.98) for 60 s deposition time. Simultaneous detection of nickel and cobalt in the low μg L−1 range was successfully performed by use of adsorptive cathodic stripping voltammetry (AdCSV) of dimethylglyoxime complexes on a silver–bismuth alloy electrode, and a good correlation was found with corresponding AAS results (r 2=0.999 for nickel and 0.965 for cobalt). Analyses of lead in the μg L−1 range in nickel-plating solution were performed with good sensitivity and stability by DPASV, using a working electrode of silver together with a glassy carbon counter electrode in samples diluted 1:3 with distilled water and acidified with H2SO4 to pH 2. A new commercial automatic at-line system was tested, and the results were found to be in agreement with an older mercury drop system. The stability of the solid electrode systems was found to be from one to several days without any maintenance needed.
Keywords: Voltammetry; Heavy metals; Non-toxic solid electrodes; Metallurgical process water; Wastewater
Determination of methylmercury in environmental samples using static headspace gas chromatography and atomic fluorescence detection after aqueous phase ethylation by M. Leermakers; H. L. Nguyen; S. Kurunczi; B. Vanneste; S. Galletti; W. Baeyens (pp. 327-333).
A rapid and automated method for the determination of monomethylmercury (MMHg) in environmental samples was developed using headspace gas chromatography with atomic fluorescence detection in combination with aqueous phase ethylation. Sample preparation steps were optimized for sediments, biological samples, and water samples using certified reference materials and real samples with a broad range of MMHg concentrations. Different extraction procedures were compared for both sediments and biological samples. The methods were applied in the intercomparison exercises for the certification of MMHg in sediments (IAEA 405) and in Oyster tissue (BCR 710) and the results were accepted for certification. The detection limits for MMHg are 0.002 ng Hg/g for sediments and biological samples and 0.01 ng Hg/L for water samples. The method was tested for methylation artifacts; no artifact was observed in the sediment samples and CRMs tested.
Keywords: Mercury; Speciation; Methylmercury; Headspace gas chromatography
Assessment of element-specific homogeneity in reference materials using microanalytical techniques by M. Rossbach; E. Zeiller (pp. 334-339).
The IAEA established in 1994 a co-ordinated research programme (CRP) on "Reference Materials for Microanalytical Nuclear Techniques" as part of its efforts to promote and strengthen the use of nuclear analytical technologies in member states with the specific aim of improving the quality of analysis of nuclear, environmental, and biological materials. The objectives of this initiative were: to identify suitable biological reference materials which could serve the needs for quality control in microanalytical techniques; to evaluate existing CRMs for use in microanalytical investigations; to evaluate appropriate sample pretreatment procedures for materials being used for analysis with microanalytical techniques; to identify analytical techniques which can be used for characterisation of homogeneity determination, and to apply such techniques to the characterization of candidate reference materials for use with microanalytical techniques. The CRP lasted for 4 years and seven laboratories and the Agency's Laboratories in Seibersdorf participated. A number of materials including the candidate reference materials IAEA 338 (lichen) and IAEA 413 (single cell algae, elevated level) were evaluated for the distribution of elements such as Cl, K, Ca, Cr, Mn, Fe, Zn, As, Br, Rb, Cd, Hg, and Pb. The results obtained during this CRP suggest that: each element exhibits its characteristic distribution in a matrix described by the "Ingamels' sampling constant" or the "relative homogeneity factor" of Kurfuerst; both concepts are valid over a large range of sample mass used for analysis (from 0.1 μg to around 100 mg); and materials being characterised quantitatively for element homogeneity could be used for the experimental determination of total uncertainty of other analytical techniques. As far as we are aware this is the first time the concept of quantitative characterisation of homogeneity has been applied to potential reference materials and the first demonstration of the feasibility and usefulness of the concept with particular emphasis on enhancing quality control opportunities for microanalytical techniques.
Keywords: Homogeneity; Reference materials; IAEA; Nuclear analytical methods; Ingamels' sampling constant
Application of solid-phase extraction for determination of phenolic compounds in barrique wines by D. Matějíček; B. Klejdus; O. Mikeš; D. Štěrbová; V. Kubáň (pp. 340-345).
A fast, selective and sensitive chromatographic method has been developed for determination of gallic, protocatechuic, p-hydroxybenzoic, vanillic, caffeic, syringic, p-coumaric, benzoic, ferulic, sinapic, cinnamic, and ellagic acids and p-hydroxybenzaldehyde, vanillin, syringaldehyde, 2-furfural, 5-methylfurfural, and 5-methoxyfurfural. The compounds from untreated wine samples were pre-concentrated and cleaned using solid-phase extraction on RP-105 polymeric sorbent. The cartridge was conditioned with methanol and water. Co-extracted ballast substances were rinsed from the sorbent with 0.1 mol L−1 hydrochloric acid–methanol, 1:4 (v/v). Retained phenolic compounds were selectively eluted with diethyl ether. A linear mobile phase gradient containing 0.3% acetic acid and methanol was used for final baseline chromatographic separation on a Hypersil BDS C18 column. Limits of detection (LOD=3s bl) in the range 5.2 to 181.2 μg L−1, resolution (R) better than 1.7, and repeatability of 2.7–5.1% (RSD for real samples) were achieved. The method was applied for quantification of individual phenolic compounds in barrique wines.
Keywords: Liquid chromatography; Phenolic compounds; Benzoic acid derivatives; Cinnamic acid derivatives; 2-Furfural derivatives; Solid-phase extraction; Barrique wine
Novel fluorescent colloids as a DNA fluorescence probe by Liu Jinshui; Wang Lun; Gao Feng; Li Yongxing; Wei Yun (pp. 346-349).
Fluorescent perylene colloids in the 80–90 nm size range have been prepared by the reprecipitation method. These nanoparticles were modified by cetyltrimethylammonium bromide (CTAB) which inhibited their growth. The nanoparticles also readily interacted with DNA. The fluorescence emission was measured at λ ex/λ em=400/565 nm. The fluorescence decrease of colloid–CTAB in aqueous solution was measured in the presence of nucleic acids. Under the optimum conditions, the ratio of fluorescence intensity in the absence and presence of nucleic acids was proportional to the concentration of nucleic acids over the range 0.02–5.1 µg mL−1 for FS (fish sperm) DNA or CT (calf thymus) DNA. The detection limits were 0.01 µg mL−1 for FS DNA and 0.012 µg mL−1 for CT DNA, respectively. Based on this approach, a new quantitative method for DNA assay is presented in this paper.
Keywords: Fluorescent technique; Perylene colloids; Cetyltrimethylammonium bromide (CTAB); DNA
Direct spectrometric determination of proteins in body fluids using a near-infrared cyanine dye by Wei-Rong Li; Hong Wang; Ting-Xian Yang; Hua-Shan Zhang (pp. 350-355).
A new near-infrared (NIR) dye, 1,1′-disulfobutyl-3,3,3′,3′-tetramethylindotricarbocyanine (DTCY) has been developed for the quantitation of proteins in solution. The method is based on the binding of DTCY to proteins under acidic conditions. The binding of DTCY to proteins causes a new band at 814 nm. The maximum binding number of bovine serum albumin (BSA) with DTCY was measured as 100. The linear range is 0.3–40 μg mL−1 for BSA and human serum albumin (HSA), respectively. Except for Fe2+, Cu2+, and cetyltrimethylammonium bromide, all of the examined coexisting substances show no interference in the assay. The method has been applied to the quantitation of proteins in serum and urine with recoveries between 96 and 105%.
Keywords: 1,1′-Disulfobutyl-3,3,3′,3′-tetramethylindotricarbocyanine (DTCY); Near-infrared (NIR) dye; Protein assay; Spectrophotometry
Amperometric and spectrophotometric determination of carbaryl in natural waters and commercial formulations by Dionísia C. Portela; Isabel M. F. Pereira; Paula Paíga; Cristina Delerue-Matos; M. Carmo V. F. Vaz (pp. 356-361).
The work presented describes the development and evaluation of two flow-injection analysis (FIA) systems for the automated determination of carbaryl in spiked natural waters and commercial formulations. Samples are injected directly into the system where they are subjected to alkaline hydrolysis thus forming 1-naphthol. This product is readily oxidised at a glassy carbon electrode. The electrochemical behaviour of 1-naphthol allows the development of an FIA system with an amperometric detector in which 1-naphthol determination, and thus measurement of carbaryl concentration, can be performed. Linear response over the range 1.0×10−7 to 1.0×10−5 mol L−1, with a sampling rate of 80 samples h−1, was recorded. The detection limit was 1.0×10−8 mol L−1. Another FIA manifold was constructed but this used a colorimetric detector. The methodology was based on the coupling of 1-naphthol with phenylhydrazine hydrochloride to produce a red complex which has maximum absorbance at 495 nm. The response was linear from 1.0×10−5 to 1.5×10−3 mol L−1 with a detection limit of 1.0×10−6 mol L−1. Sample-throughput was about 60 samples h−1. Validation of the results provided by the two FIA methodologies was performed by comparing them with results from a standard HPLC–UV technique. The relative deviation was <5%. Recovery trials were also carried out and the values obtained ranged from 97.0 to 102.0% for both methods. The repeatability (RSD, %) of 12 consecutive injections of one sample was 0.8% and 1.6% for the amperometric and colorimetric systems, respectively.
Keywords: Amperometry; Spectrophotometry; Carbaryl; Pesticides; Flow-injection analysis
Square-wave voltammetric determination of cefoperazone in a bacterial culture, pharmaceutical drug, milk, and urine by Sabina Billová; René Kizek; František Jelen; Pavla Novotná (pp. 362-369).
Use of square-wave voltammetry (SWV) for determination of cefoperazone (CFPZ) in some buffers, bacterial culture, urine, and milk is described. CFPZ provides a specific voltammetric signal which is affected by pH and solution components. Determination of CFPZ in Britton–Robinson buffer, pH 4.4, is sensitive with a low detection limit (about 0.5 nmol L−1). In a more complex medium (bacterial 2YT medium, pH 7.2) the detection limit was approximately 1.5 μmol L−1. We provide evidence that SWV is a suitable and quick method for CFPZ determination in a culture of living bacteria without separation of biomass. We have found big differences between methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive Staphylococcus aureus (MSSA) in cultivation in the presence of CFPZ, depending on time. When CFPZ is cleaved by penicillinase, a new SWV peak b appears at more positive potentials. This peak rises both with increasing concentration of enzyme and with cleavage time while the original CFPZ peak is simultaneously decreasing. We determined the concentration of CFPZ in the drug Pathozone by the standard addition method and achieved good agreement with the declared value of CFPZ in the drug. With a simple pretreatment procedure it is possible to determine CFPZ in milk; for urine no pretreatment was required. Using SWV we could detect CFPZ concentrations as low as 500 nmol L−1 in bovine milk and human urine.
Keywords: Cefoperazone; Pathozone; Square-wave voltammetry; Mercury electrode; Biological samples
Determination of p-tyrosol and salidroside in three samples of Rhodiola crenulata and one of Rhodiola kirilowii by capillary zone electrophoresis by Shuya Cui; Xiaoli Hu; Xingguo Chen; Zhide Hu (pp. 370-374).
A capillary zone electrophoresis (CZE) method has been developed for simultaneous assay of two bioactive components (p-tyrosol and salidroside) in Rhodiola crenulata and Rhodiola kirilowii for the first time. Those analytes were successfully separated within 15 min using 50 mmol L−1 (pH 9.62) borate containing 30% methanol as running buffer. Regression equations revealed linear relationships (correlation coefficients 0.9998–0.9999) between peak area and concentration of the two analytes. The relative standard deviations (RSD) of the migration times and the peak areas of two constituents ranged from 0.51 to 0.57% and from 0.65 to 1.17%, respectively, intra-day, and from 4.91 to 6.93% and from 3.51 to 5.33%, respectively, inter-day. The recoveries of two constituents ranged from 96.24 to 103.15%.
Keywords: Rhodiola crenulata ; Rhodiola kirilowii ; p-Tyrosol; Salidroside; Capillary zone electrophoresis
Resonance light-scattering method for the determination of BSA and HSA with sodium dodecyl benzene sulfonate or sodium lauryl sulfate by Rutao Liu; Jinghe Yang; Changxia Sun; Xia Wu; Lei Li; Zhengmin Li (pp. 375-379).
A new resonance light-scattering (RLS) assay of proteins such as bovine serum albumin (BSA) and human serum albumin (HSA) is presented. In the medium of phosphoric acid (pH=2.6), the weak RLS of sodium dodecyl benzene sulfonate (SDBS) or sodium lauryl sulfate (SLS) can be greatly enhanced by proteins, owing to interaction between the protein and the anionic surfactant and formation of an associate. The RLS intensity of the SDBS–protein system is stronger than that of the SLS–protein system under same experimental conditions. It is considered that the synergistic resonance caused by the absorption of both protein and SDBS could produce strong RLS, while absorption of protein only in the SLS system could cause relatively weak RLS. The enhanced intensity of RLS is proportional to the concentration of the protein. If SDBS is used as the probe the linear range is 7.5×10−9–1.5×10−5 g mL−1 for BSA and 1.0×10−8–1.0×10−5 g mL−1 for HSA. The detection limits are 1.8 and 2.8 ng mL−1, respectively. When SLS is used as the probe the linear range is 2.0×10−8–1.0×10−5 g mL−1 and 2.5×10−8–1.0×10−5 g mL−1 for BSA and HSA, respectively, and the detection limits are 12.8 and 21.6 ng mL−1, respectively. The biological mimics samples are synthetic concoctions of BSA and HSA with some interferents. In these samples, the concentration of interferents is higher than the concentration normally existing in organisms. The samples were determined satisfactorily.
Keywords: BSA; HSA; Sodium dodecyl benzene sulfonate; Sodium lauryl sulfate; Resonance light scattering