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Analytical and Bioanalytical Chemistry (v.376, #6)
Automated coupling of capillary-HPLC to matrix-assisted laser desorption/ionization mass spectrometry for the analysis of small molecules utilizing a reactive matrix by Stephan Brombacher; Stacey J. Owen; Dietrich A. Volmer (pp. 773-779).
This study describes the application of a novel, reactive matrix for the mass spectral analysis of steroids by capillary-high performance liquid chromatography (capillary-HPLC) coupled to matrix-assisted laser desorption/ionization (MALDI). The mass spectral analysis of steroids was accomplished after fully automated peak deposition of chromatographic peaks onto MALDI targets. The seven corticosteroids used as test compounds were: triamcinolone, prednisone, cortisone, fludrocortisone, dexamethasone, deoxycorticosterone, and budesonide. They were separated using a PepMap C18 (3 μm particle size, 100 Å pore width) column at five different concentration levels of 25, 15, 7.5, 2.5 and 1 ng/μL, and the peaks were detected at a wavelength of 237 nm. The column effluent was mixed with 2,4-dinitrophenylhydrazine (DNPH) directly following the UV detector. The chromatographic peaks were then deposited onto the MALDI target with a robotic micro-fraction collector triggered by the UV detector signals. A special hydrophobic surface coating allowed the deposition of up to 4 μL (up to 90 % of the chromatographic peak volume) onto one sample spot. The compounds were then identified by MALDI mass spectrometry. Depending on the nature of the analyte, radical cations ([M]+. ) and sodium adduct ions ([M+Na]+) of the steroids as well as protonated steroid-dinitrophenylhydrazone derivatives ([MD+H]+) were detected in positive ion mode. The detection limits were between 0.5 and 15 ng injected with capillary-HPLC-MALDI-TOF-MS and between 0.3 and 3 ng on target with MALDI-TOF when deposited manually.
Determination of tributyltin in marine sediment: Comité Consultatif pour la Quantité de Matière (CCQM) pilot study P-18 international intercomparison by R. E. Sturgeon; R. Wahlen; T. Brandsch; B. Fairman; C. Wolf-Briche; J. I. Garcia Alonso; P. Rodriguez González; J. Ruiz Encinar; A. Sanz-Medel; K. Inagaki; A. Takatsu; B. Lalere; M. Monperrus; O. Zuloaga; E. Krupp; D. Amouroux; O. F. X. Donard; H. Schimmel; B. Sejerøe-Olsen; P. Konieczka; P. Schultze; P. Taylor; R. Hearn; L. Mackay; R. Myors; T. Win; A. Liebich; R. Philipp; L. Yang; S. Willie (pp. 780-787).
The capabilities of National Metrology Institutes (NMIs—those which are members of the Comité Consultatif pour la Quantité de Matière (CCQM)of the CIPM) and selected outside "expert" laboratories to quantitate (C4H9)3Sn+ (TBT) in a prepared marine sediment were assessed. This exercise was sanctioned by the 7th CCQM meeting, April 4–6, 2001, as an activity of the Inorganic Analysis Working Group and was jointly piloted by the Institute for National Measurement Standards of the National Research Council of Canada (NRC) and the Laboratory of the Government Chemist (LGC), UK. A total of 11 laboratories submitted results (7 NMIs, and 4 external labs). Two external laboratories utilized a standard calibration approach based on a natural abundance TBT standard, whereas all NMIs relied upon isotope dilution mass spectrometry for quantitation. For this purpose, a species specific 117Sn-enriched TBT standard was supplied by the LGC. No sample preparation methodology was prescribed by the piloting laboratories and, by consequence, a variety of approaches was adopted by the participants, including mechanical shaking, sonication, accelerated solvent extraction, microwave assisted extraction and heating in combination with Grignard derivatization, ethylation and direct sampling. Detection techniques included ICP–MS (with GC and HPLC sample introduction), GC–MS, GC–AED and GC–FPD. Recovery of TBT from a control standard (NRCC CRM PACS-2 marine sediment) averaged 93.5±2.4% (n=14). Results for the pilot material averaged 0.680±0.015 µmol kg−1 (n=14; 80.7±1.8 µg kg−1) with a median value of 0.676 µmol kg−1. Overall, performance was substantially better than state-of-the-art expectations and the satisfactory agreement amongst participants permitted scheduling of a follow-up Key comparison for TBT (K-28), a Pilot intercomparison for DBT (P-43), and certification of the test sediment for TBT content and its release as a new Certified Reference Material (HIPA-1) with a TBT content of 0.679±0.089 µmol kg−1 (expanded uncertainty, k=2, as Sn) (80.5±10.6 µg kg−1).
Keywords: Tributyltin; Marine sediment; International intercomparison
Analytical characteristics and sensitivity mechanisms of electrolyte-insulator-semiconductor system-based chemical sensors—a critical review by Yuri G. Vlasov; Yuri A. Tarantov; Peter V. Bobrov (pp. 788-796).
Recent trends in research and development of electrolyte-insulator-semiconductor (EIS) field-effect chemical sensors (ion-selective field-effect transistors, light-addressable potentiometric sensors, capacitive EIS-sensors) with inorganic gate insulators (oxide, nitride and chalcogenide films) are reviewed. Physical properties of EIS systems and basic mechanisms of their chemical sensitivity are examined. Analytical characteristics and sensing mechanisms of EIS pH sensors with oxide and nitride films, as well as metal ions sensors with chalcogenide films, are critically discussed. Prospects of future research on EIS field-effect biosensors are briefly outlined.
Keywords: EIS sensors; Chemical sensors; ISFETs
Measurement of nitric oxide production by the lesioned rat retina with a sensitive nitric oxide electrode by Markus Groppe; Solon Thanos; Wolfgang Schuhmann; Peter Heiduschka (pp. 797-807).
Nitric oxide (NO) plays multiple roles in the nervous system. It is produced as a result of damage or injury of the retina as a part of the central nervous system. Detailed knowledge of the extent and the time course of NO production is of great importance for the understanding of pathological processes and their appropriate medical treatment.Sections of rat retina were stained with antibodies against the three isoforms of NO synthase (NOS) at several time points after a lesion of the optic nerve. No significant changes of NOS expression could be seen at any of the checked time points.For the electrochemical detection of NO production, we modified small platinum electrodes with a NO-sensitive nickel porphyrin by electrochemical polymerisation. Compared to other substances, electrochemically polymerised eugenol was found to be most suitable for protection against interferences. For the measurements, differential pulse amperometry was used. The response to nitric oxide was linear.NO production of adult rat retinas was measured post axotomy after different time points with electrochemical electrodes ex vivo. With non-treated retinas, an NO concentration of approximately 15 μM was measured. NO concentration is elevated after an axotomy reaching its highest value of up to 30 μM 5 days after the lesion. The NO concentration is decreased below the initial value after 9–14 days post axotomy.
Keywords: Nitric oxide; Electrode; Retina; Eugenol; Axotomy; Immunohistochemistry
A liquid chromatography/electrospray ionization–tandem mass spectrometry method for quantification of specific organophosphorus pesticide biomarkers in human urine by Anders O. Olsson; Johnny V. Nguyen; Melissa A. Sadowski; Dana B. Barr (pp. 808-815).
Organophosphorus pesticides are commonly used in both agricultural and residential settings. The widespread use of these chemicals makes it almost impossible for humans to avoid exposure. In order to determine background human exposure, there is a need for fast, reliable, and sensitive analytical methods. We have developed a sensitive method to quantify specific biomarkers of the organophosphorus pesticides acephate, azinphos, chlorpyrifos, coumaphos, diazinon, isazofos, malathion, methamidophos, parathion and pirimiphos or their O,O-dimethyl analogues in human urine, as their selective metabolites or as the intact pesticide. Isotopically labeled internal standards were used for eight of the analytes. The use of labeled internal standards in combination with high-performance liquid chromatography electrospray ionization–tandem mass spectrometry provided a high degree of specificity. Repeated analysis of urine samples fortified with high and low concentrations of the analytes gave relative standard deviations (RSD) of less than 10% for the analytes with an isotopically labeled standard. Analytes without isotopically labeled standards had higher RSD. For all compounds except methamidophos and acephate, the recoveries were greater than 70%. The limits of quantification for most of the analytes were in the range of 0.1 to 1 ng/mL. We detected concentrations of most of these pesticides and/or their metabolites in urine samples from non-occupationally exposed persons using our method. Our frequencies of detection for the analytes measured ranged from 1% to 98%.
Detection of 1-hydroxypyrene in urine by direct fluorometric analysis on a solid sorbing phase. Validation and application of the method to biological monitoring of PAH-exposed persons by Michel Lamotte; Rachid Belfutmi; Philippe Fornier de Violet; Philippe Garrigues; Michel Lafontaine; Christine Dumas (pp. 816-821).
A new method for the detection and quantification of 1-hydroxypyrene (1-OHPy) in the urines of persons exposed to polycyclic aromatic hydrocarbons (PAH) has been evaluated. The method is based on extraction/concentration of the analyte onto a small element cut into tabs from an extraction disk (ENVI-Disk™ C18 from Supelco) combined with front-face synchronous fluorescence detection and direct quantification on the solid sorbent element. The limit of detection for 1-OHPy was estimated to be about 0.03–0.04 µg/L, a value which is significantly lower than the pyrene metabolite concentration commonly found in unexposed to weakly PAH-exposed persons (≈0.1–0.3 µg/L). A quantification based on only one standard addition has been adopted and the method was validated both by testing analyte recovery using a known amount of a commercially available pyrene metabolite and by comparing the results with those obtained by high-performance liquid chromatography (HPLC). The results were very close to the HPLC results, the largest deviations being attributed to variations or defects in the stirring system, the rate stability of which was found to be of major importance for the reproducibility and reliability of the measurements. The applicability of the method was further tested by analyzing 1-OHPy in the urine of a volunteer exposed to various automobile traffic zones. The results confirm previous findings which lead to the conclusion that urinary concentrations of PAH metabolites are influenced more by smoking habit than by exposure to urban atmospheric pollution. Thus, the method appears to be an alternative to the usual method based on HPLC. Moreover it presents some advantages, being simple to operate and requiring relatively low-cost instruments.
Keywords: SPE; Fluorescence; PAH exposure; Urine; 1-Hydroxypyrene
Partial-filling affinity capillary electrophoresis by Valerie Villareal; John Kaddis; Maryam Azad; Cecilia Zurita; Isba Silva; Lili Hernandez; Marcellus Rudolph; Julio Moran; Frank A. Gomez (pp. 822-831).
Partial-filling affinity capillary electrophoresis (PFACE) is used to examine the binding interactions between two model biological systems: D-Ala-D-Ala terminus peptides to the glycopeptide antibiotic vancomycin (Van) from Streptomyces orientalis, and arylsulfonamides to carbonic anhydrase B (CAB, EC 4.2.1.1, bovine erythrocytes). Using these two systems, modifications in the PFACE technique are demonstrated including flow-through PFACE (FTPFACE), competitive flow-through PFACE (CFTPFACE), on-column ligand synthesis PFACE (OCLSPFACE), and multiple-step ligand injection PFACE (MSLIPFACE). In PFACE small plugs of sample are injected into the capillary column and an equilibrium is established between receptor and ligand during electrophoresis. Binding constants are then obtained by Scatchard analysis using changes in the migration time of the receptor/ligand on changing the concentration of the ligand/receptor. Data demonstrating the quantitative potential of these methods are presented. This review focuses on the unique capabilities of the different PFACE techniques as applied to two model biological systems.
Keywords: Partial filling; Affinity capillary electrophoresis; Binding constants; Receptor; Ligand; Scatchard plot
Polymeric FAD used as enzyme-friendly mediator in lactate detection by Mihaela D. Leonida; Daniel T. Starczynowski; Riva Waldman; Benedict Aurian-Blajeni (pp. 832-837).
We present the fabrication and properties of lactate biosensors. The novel feature is the use of polymerized flavin adenine dinucleotide (FAD) as mediator for electron transfer. The biosensors were prepared using lactate dehydrogenase (LDH), lactate oxidase (LOX), or baker's yeast (BY) immobilized at the surface of the electrode. The sensors using purified enzymes showed good sensitivity, linearity, and stability. The sensitivity of the BY electrodes was slightly lower. The advantages of this type of sensors are discussed in connection with potential applications.
Keywords: Biosensors; Lactate; Lactate oxidase; Lactate dehydrogenase; FAD
Sustained modelling ability of artificial neural networks in the analysis of two pharmaceuticals (dextropropoxyphene and dipyrone) present in unequal concentrations by María S. Cámara; Félix M. Ferroni; Mercedes De Zan; Héctor C. Goicoechea (pp. 838-843).
An improvement is presented on the simultaneous determination of two active ingredients present in unequal concentrations in injections. The analysis was carried out with spectrophotometric data and non-linear multivariate calibration methods, in particular artificial neural networks (ANNs). The presence of non-linearities caused by the major analyte concentrations which deviate from Beer's law was confirmed by plotting actual vs. predicted concentrations, and observing curvatures in the residuals for the estimated concentrations with linear methods. Mixtures of dextropropoxyphene and dipyrone have been analysed by using linear and non-linear partial least-squares (PLS and NPLSs) and ANNs. Notwithstanding the high degree of spectral overlap and the occurrence of non-linearities, rapid and simultaneous analysis has been achieved, with reasonably good accuracy and precision. A commercial sample was analysed by using the present methodology, and the obtained results show reasonably good agreement with those obtained by using high-performance liquid chromatography (HPLC) and a UV-spectrophotometric comparative methods.
Keywords: Simultaneous determination; Dextropropoxyphene; Dipyrone; Artificial neural networks; Non-linearities
Diamond paste-based electrodes for determination of Cr(III) in pharmaceutical compounds by Raluca-Ioana Stefan; Semere Ghebru Bairu; Jacobus Frederick van Staden (pp. 844-847).
A new class of monocrystalline diamond paste-based electrodes is proposed for the determination of chromium(III) at trace levels in vitamins. Three types of monocrystalline diamond—natural diamond 1μ (natural diamond), synthetic diamond 50μ (synthetic-1), and synthetic diamond 1μ (synthetic-2)—were used for electrode construction. The linear concentration ranges are between 10−10 and 10−8; 10−9 and 10−7, and 10−10 to 10−8 mol L−1, with limits of detection of 10−12, 10−12, and 10−11 mol L−1, when natural diamond, synthetic-1, and synthetic-2, respectively, are used as electrode materials. For electrodes based on natural diamond and synthetic-1 it was found that Cr(III) yields a peak at about +0.275±0.015 V (vs. Ag/AgCl) within a predetermined positive potential range situated between +0.4 and +0.2 V, while for the electrode based on synthetic-2 the peaks are found at +0.300±0.015 V (vs. Ag/AgCl). The proposed method is reliable for the determination of chromium(III) at trace levels in two vitamin tablets (RSD<0.2%).
Keywords: Diamond paste-based electrodes; Monocrystalline diamond; Chromium(III)
High-performance liquid chromatographic determination of diltiazem in human plasma after solid-phase and liquid–liquid extraction by Dragica Zendelovska; Trajče Stafilov; Marina Stefova (pp. 848-853).
A selective, sensitive, and accurate high-performance liquid chromatographic method for determination of diltiazem in plasma samples has been developed and validated. The effects of mobile phase composition, buffer concentration, mobile phase pH, and concentration of organic modifiers on retention of diltiazem and internal standard were investigated. Solid-phase and liquid–liquid extraction were examined and proposed for isolation of the drug and elimination of endogenous plasma interferences. A 5 μm Lichrocart Lichrospher 60 RP-select B chromatographic column was used; the mobile phase was acetonitrile–0.025 mol L−1 KH2PO4 (pH 5.5), 35:65 ( v / v) at a flow-rate of 1.5 mL min−1. The detection wavelength was 215 nm. The calibration plots were linear in the concentration range 20.0–500.0 ng mL−1. The method has been implemented to monitor diltiazem levels in patient samples.
Keywords: Diltiazem; Determination; Human plasma; High-performance liquid chromatography
Isolation and determination of p-hydroxybenzoylcholine in traditional Chinese medicine Semen sinapis Albae by Lifang Liu; Tao Liu; Genxi Li; Qiang Wang; Tzibun Ng (pp. 854-858).
A special component is isolated from Semen sinapis Albae (white mustard seed), a traditional Chinese medicine. According to the physical and chemical investigation and spectroscopic identification, this component can be known as p-hydroxybenzoylcholine bisulfate, a choline base. This component in the drug is also determined by RP-HPLC. A reversed-phase C18 column is used to separate the p-hydroxybenzoylcholine with an eluent of methanol–0.05 mol/L monopotassium phosphate solution (30:70) (adjusted by phosphoric acid to pH 3.6) at the flow rate of 0.5 mL/min. Detection is carried out with a UV detector operated at 285 nm, and the column temperature is 25 °C. It reveals that there is 0.021% (w/w) of p-hydroxybenzoylcholine bisulfate in Semen sinapis Albae and 0.037% (w/w) in stir-baked Semen sinapis Albae.
Keywords: Semen sinapis Albae; p-Hydroxybenzoylcholine bisulfate; HPLC; Determination
Quantitative enantiomeric analysis of chlorcyclizine, hydroxyzine, and meclizine by capillary electrophoresis by Yu- Hsiang Ho; Hsin- Lung Wu; Shou- Mei Wu; Su- Hwei Chen; Hwang- Shang Kou (pp. 859-863).
A simple capillary zone electrophoresis method was developed for the quantitative enantiomeric analysis of piperazine antihistamines with teratogenic suspicion in animals. Enantioseparation of chlorcyclizine, hydroxyzine, and meclizine was performed in glycine buffer (0.6 mol L-1; pH 3.00) with sulfated β-cyclodextrin (5 mg mL-1) as a chiral selector; and the separated drugs were monitored by ultra-violet detector. The lower quantitation of the individual enantiomer is attainable at 10 µmol L-1, using an achiral piperazine drug (cyclizine) as internal standard. The method is simple and rapid with a short run time (<5 min) for the analysis of chlorcyclizine, hydroxyzine or meclizine enantiomers.
Keywords: Enantiomeric quantitation; CE; Chlorcyclizine; Hydroxyzine; Meclizine
Interaction of magnolol with bovine serum albumin: a fluorescence-quenching study by Jiaqin Liu; Jian-niao Tian; Jiyou Zhang; Zhide Hu; Xingguo Chen (pp. 864-867).
The interaction of magnolol with bovine serum albumin(BSA) was studied using fluorescence spectroscopy under physiological conditions. The binding constants, K, and the ratio of quantum yields of protein fluorescence for complex and free protein, f, at 298 K, 304 K, and 310 K were obtained; the values were 6.799×105 L mol−1, 5.541×105 L mol−1, and 4.344×105 L mol−1 and 0.17, 0.30, and 0.34, respectively. The standard enthalpy change (ΔH°) and the standard entropy change (ΔS°) were calculated to be –28.53 kJ mol−1 and 15.88 J mol−1 K−1, which indicated that hydrophobic forces played major role in the interaction of magnolol and BSA. The binding average distance between magnolol and BSA (4.32 nm) was obtained on the basis of the theory of Förster energy transfer.
Keywords: Magnolol; Bovine serum albumin; Fluorescence quenching
Determination of berberine by measuring the enhanced total internal reflected fluorescence at water/tetrachloromethane interface in the presence of sodium dodecyl benzene sulfonate by Ping Feng; Cheng Zhi Huang; Yuan Fang Li (pp. 868-872).
A highly sensitive method for determination of berberine is proposed based on the measurements of total internal reflected fluorescence (TIRF) at water/ tetrachloromethane (H2O/CCl4) interface. In the pH range of 2.6–5.7, the co-adsorption of the berberine with the anionic surfactants such as sodium dodecyl benzene sulfonate (SDBS), sodium dodecylsulfonate (SDS), and sodium lauryl sulfate (SLS) occurs at the H2O/CCl4 interface, resulting in greatly enhanced TIRF signal characterized by the emission at 526 nm when excited with a 351 nm light beam. The enhanced TIRF intensity is in proportion to the berberine concentration in the range 0.2–10.0×10-7 mol L-1. The limit of detection is 1.7×10-9 mol L-1 (3σ). It was found that ions such as Ca(II), Cu(II), Fe(III), Cd(II), Mg(II), Zn(II), Pb(II), and Al(III) can be allowed larger than 1.0×10-4 mol L-1. Meanwhile, the organic compounds such as vitamin B, saccharine, and amino acid do not display any effect for the present TIRF method even if they are larger than 1.0×10-2 mol L-1in high concentration levels (larger than 1.0×10-5 mol L-1). The results of determination for synthetic samples were agreement with the desired values, and the ones for tablets were identical with those obtained according to the method of Chinese Pharmacopoeia.
Keywords: Total internal reflected fluorescence; Berberine; Sodium dodecyl benzene sulfonate
Chemiluminescence determination of melatonin and some of its derivatives using potassium permanganate and formaldehyde system by Guo Nan Chen; Fu Xin Huang; Xiao Ping Wu; Zheng Feng Zhao; Jian Ping Duan (pp. 873-878).
It was found that melatonin and its derivatives, such as N-acetyl- 5-methoxytryptamine (MT), N-acetyl-5-hydroxytryptamine (NAS), 5-Methoxytrypt- amine (5-MT), 5-Methoxyindolyl acetic acid (5-MIAA) and N-acetyl-5-methoxy- 6-hydroxytryptamine (6-HMT) would give chemiluminescence in the acidic potassium permanganate solution, and formaldehyde would enhance this chemiluminescent reaction greatly. The optimum conditions for this chemiluminescent reaction were studied in detail by a flow injection system. A new simple rapid method has been developed under the optimum conditions for determination of melatonin. This method has the advantages of high sensitivity, wide range of linear response and low detection limit. On the basis of investigation of chemiluminescent, fluorescent and UV spectra of melatonin in acidic solution containing potassium permanganate and formaldehyde, a possible mechanism of this reaction was proposed.
Keywords: Melatonin and its derivatives; Chmeiluminescence; Flow injection
Three useful bromimetric methods for the determination of salbutamol sulfate by K. Basavaiah; H. C. Prameela (pp. 879-883).
Three different methods developed for the determination of salbutamol sulfate (SBS), in pure drug form and in dosage forms, are discussed. The methods are based on the oxidation–bromination reaction of the drug by bromine generated in-situ by the interaction of bromate with bromide in acid medium. In titrimetry the drug is titrated directly with bromate in the presence of a large excess of bromide and in sulfuric acid medium using methyl red as indicator. Spectrophotometry is based on addition of a measured excess of bromate–bromide mixture to the sample solution in sulfuric acid medium followed by the estimation of surplus bromine by reacting it with a definite amount of methyl orange dye and measuring the absorbance at 510 nm. The amount of bromate reacting corresponds to the sample content. The kinetic method depends on the linear relationship between the concentration of the drug and time for oxidation and bromination as indicated by the bleaching of the methyl orange acid colour by the bromine generated in situ. Titrimetry is applicable in the 2–20 mg range. In spectrophotometry, Beer's law is obeyed in the 0.5–5.0 μg mL−1 range whereas concentrations in the 5.0–25.0 μg mL−1 range can be determined by the kinetic method. The effect of common excipients and additives in tablets is discussed. The procedures have been successfully applied to dosage forms; the results agree well with those obtained by use of a reference method. The methods can be used to determine SBS at mg or μg levels.
Keywords: Salbutamol sulfate; Determination; Bromate–bromide; Titrimetry; Spectrophotometry; Kinetic method
Determination of iridoid glycosides in larvae and adults of butterfly Melitaea cinxia by partial filling micellar electrokinetic capillary chromatography—electrospray ionisation mass spectrometry by Johanna Suomi; Heli Sirén; Matti Jussila; Susanne K. Wiedmer; Marja-Liisa Riekkola (pp. 884-889).
The iridoid glycosides, methyl catalpol, asperuloside, verbenalin, cinnamoyl catalpol, catalpol and aucubin, were studied from both larvae and adults of butterfly Melitaea cinxia. Special emphasis in the study was put on finding a correlation between the iridoid glycoside content in butterflies and plants. An optimised partial filling micellar electrokinetic capillary chromatographic–electrospray ionisation mass spectrometric (PF-MECC-ESI-MS) method was employed for the separation and identification of the six iridoid glycosides. In this work, the isolation and determination of catalpol and aucubin from extracts of both larvae and adults of Melitaea cinxia butterflies is demonstrated. The PF-MECC-ESI-MS method, using the [M+Na]+, [M+Li]+ and/or [M+NH4]+ adducts in ESI-MS, was used for quantification of aucubin and catalpol in the insects. In addition, the identification of all analytes was attempted by direct infusion MS/MS analysis. LOQ values for the iridoid glycosides varied between 10 mg/l (for verbenalin) to 50 mg/l (for catalpol and aucubin) corresponding to 0.1% of the sample´s dry mass. A correlation was noticed between the concentrations of iridoid glycosides in plants and the concentrations in larvae feeding on them.
Keywords: Iridoid glycoside; Micellar electrokinetic capillary chromatography; Electrospray ionisation mass spectrometry; Partial filling; Melitaea cinxia
Evalution of sequential extractions on dry and wet sediments by W. Baeyens; F. Monteny; M. Leermakers; S. Bouillon (pp. 890-901).
A five-step sequential extraction procedure was applied on dried and wet Ballastplaat Scheldt estuary sediments. When wet (fresh) sediments were used, all sample handling up to the 3rd extraction step, inclusive, was carried out under inert atmosphere. The repeatability of the procedure was very good on dry samples. For Fe as for Mn, RSD values are lower than 4%, except for Mn in the fifth extraction step where a spread of 10% is observed. The observed RSDs for Pb are of the same order of magnitude as those for Mn. On wet samples the spread of the results is higher than on dried ones. The highest RSDs observed for Fe amount to 20%, for Mn to 15% but for Pb an RSD of up to 44% was found. Better homogenization of the solid sediment part of lyophilized sediments and different porosities of wet sediment sub-samples may be the explanation. These results also indicated that drying/oxidizing of the sediment sample causes a shift from less available/mobile metal fractions to more available/mobile fractions. The Mn and Fe oxyhydroxide spikes added to a wet sediment sample were recovered between 100±10%. The results obtained after changing the sequence of the extraction steps (multiple rotations and inversions were tested) corroborated the progressive increase in the aggressive nature of the extraction solutions in our standard scheme. Although there is also no need to change the ratio volume of extractant to amount of sediment, increasing the number of extraction repetitions in steps 1 to 3 resulted, for some of those extraction steps, in a partially modified analyte distribution. Finally the method was applied to sandy and muddy sediment cores of the Scheldt estuary and revealed clear differences between metal distributions in both types of sediment.
Keywords: Sequential extractions; Dry sediments; Wet sediments; Metal analysis
Amperometric biosensor with HRP immobilized on a sandwiched nano-Au / polymerized m-phenylenediamine film and ferrocene mediator by Jin Li; Lang-Tao Xiao; Xuan-Ming Liu; Guang-Ming Zeng; Guo-He Huang; Guo-Li Shen; Ru-Qin Yu (pp. 902-907).
An amperometric biosensor has been developed for the determination of H2O2 in plant samples. Horseradish peroxidase (HRP) is immobilized on a sandwiched nano-Au particle / m-phenylenediamine polymer film by glutaraldehyde cross-linking. The film is formulated on the carbon paste electrode (CPE) blended with ferrocene as an electron transfer mediator. On the low concentration range, the current response is related to the H2O2 concentration linearly from 0 to 8×10-6 M with a detection limit of 1.3×10-7 M. On a wider concentration range of 8×10-6 to 1.4×10-4 M, the reciprocal of current response is linearly related to the reciprocal of H2O2 concentration. The apparent Michaelis-Menten constant (Km app) was calculated to be 0.0334 mM. The sensor has been tested by determining H2O2 concentration in plant leaf samples.
Keywords: Enzyme biosensor; H2O2 ; Nano-Au particle; m-Phenylenediamine polymer
Comparison of alternative and conventional extraction techniques for the determination of zearalenone in corn by Lea Pallaroni; Christoph von Holst (pp. 908-912).
Naturally contaminated corn samples of different origin were extracted using two conventional techniques (blending and shaking) and three alternative approaches (ultrasonic extraction, accelerated solvent extraction, and microwave-assisted extraction). Use of the same extraction mixture for all trials enabled the efficiency of the various extraction techniques to be compared. Extracts were filtered and directly analyzed by LC–ESI–MS, without further clean-up. The yield from the alternative extraction techniques showed efficiency to be higher than for conventional techniques. In particular, microwave-assisted extraction was slightly superior to other techniques.
Keywords: Zearalenone; Extraction; Microwave-assisted extraction; Accelerated solvent extraction; Ultrasonic extraction
Distribution of rare earth elements among chloroplast components of hyperaccumulator Dicranopteris dichotoma by Xiao-ping Wang; Xiao-quan Shan; Shu-zhen Zhang; Bei Wen (pp. 913-917).
A rare earth element (REE) hyperaccumulator, Dicranopteris dichotoma, that accumulates more than 0.1% REEs dry leaf mass has been discovered in southern China. The different components of chloroplast were isolated and the concentration of REEs in each component was determined by ICP-MS. The experimental data indicated that about 8% of total leaf REEs was present in the chloroplast of Dicranopteris dichotoma. In order to thoroughly study the distribution of REEs among different components of chloroplast, the membrane of chloroplast, the intact thylakoid and the photosystem II (PS II system) of D. dichotoma were isolated from the chloroplast. It was found that half of total chloroplast REEs was stored at the membrane of the chloroplast and another half was in the thylakoid. And 25% of total chloroplast REEs was bound with PS II system of D.dichotoma. The concentration of REEs in chlorophyll a was only at the level of μg/g on the bases of chlorophylls. These data are useful for understanding of both the storage of REEs in chloroplast and the effect of REEs on the photosynthesis of plants.
Keywords: Hyperaccumulator; Chloroplast; Rare earth elements
Rapid fluorimetric assay for primary amine groups in water samples by A. Sevillano Cabeza; Y. Moliner Martinez; C. Molins Legua; P. Campíns Falcó (pp. 918-922).
Bond Elut C18 solid-phase extraction cartridges were used for pre-concentration followed by derivatization with o-phthaldialdehyde-N-acetylcysteine (OPA-NAC) of primary amines in water. Optimal conditions were: conditioning the cartridges with borate buffer pH 10.4, retention of the primary amines, addition of the OPA-NAC(3.7 mmol L–1) 1:1 molar ratio and borate buffer pH 8, elution of the isoindol with MeOH-borate buffer (9:1) pH 10.2 and fluorescence measurement. The equations of the calibration graphs for methylamine, ethylamine, propylamine, butylamine, pentylamine, and β-phenylethylamine at λexcitation=330 nm and λemission=440 nm, in the optimal conditions are presented. The solid-phase extraction procedure improved ten times the detection limits of the solution derivatization. Those values are in the 0.01–0.06 mg L–1 interval in function of the amine. Also, it is possible to estimate the total primary aliphatic amine concentration in water, expressed as molar concentration of –NH2 group or –NH2-N mg L–1. On the basis of these studies, the method was applied for the determination of primary amino groups in tap, ground, factory and source water samples.
Keywords: Fluorimetry; Primary amines; Solid-support assisted-derivatization; Waters
Chromatographic behavior of cadmium in an ion-pair reversed-phase micro HPLC system and its application to the determination of bio-available cadmium in soil samples by Bin Li; Qiuquan Wang; Hua Yan; Limin Yang; Benli Huang (pp. 923-927).
A novel reversed phase ion-pair micro HPLC system with on-line fluorescence detection has been developed systematically and studied for the determination of cadmium in its bio-available fractions of soil samples. In this system, a micro ODS column of 1.0 mm i.d.×150 mm length and a mobile phase containing 6 mmol L-1 8-hydroxyquinoline 5-sulphonic acid (HQS), 3 mmol L-1 cetyltrimethylammonium bromide (CTMABr), 10 mmol L-1 acetic acid-acetate buffer (pH 5.1) as well as 50% acetonitrile at 50 μL min-1 flow rate were employed to determine cadmium with a 2 μL flow cell through its fluorescence at 518 nm under 338 nm excitation. Furthermore, the composition of Cd-HQS chelate formed on the column was confirmed to be [Cd(HQS)2]2- through a log–log plot method, and then combined with the ion-pair reagent by the electrostatic force under the chromatographic condition proposed. With such a method, the detection limit of cadmium was 8.48 ng mL-1 (3σ) with 1 μL sample injection, and the linear range for the determination of cadmium was 30–800 ng mL-1 (R2=0.992). This method has been successfully applied to determination of cadmium in its bio-available fractions of BCR-483 and soil samples without interference from other coexistent metal ions. The RSD (n=6) was less than 7.3%. The results were in agreement with the indicative value for BCR-483 and those for the soil samples obtained by ICP-MS with a pretreatment of bis(1,1,3,3-tetramethylbutyl) phosphinic acid extraction.
Keywords: Micro HPLC; Bio-available cadmium; Elemental fractionation
Speciation analysis of chromium by separation on a 5-palmitoyl oxine-functionalized XAD-2 resin and spectrophotometric determination with diphenylcarbazide by Hayati Filik; Melek Doğutan; Reşat Apak (pp. 928-933).
The method developed in this work for the separation and preconcentration of Cr(III) is based on its retention by an Amberlite XAD-2 copolymer resin functionalized with 5-palmitoyl-8-hydroxyquinoline (oxine), abbreviated XAD-POx, with the ligand covalently bound to the copolymer. Cr(III) sorption was quantitative within the pH range 4.5–7.0 and Cr(VI) was not retained. The Cr(III) held by the resin column was eluted with a hot solution of H2O2 in pH≥9.0 aqueous NH3–NH4Cl buffer, and Cr oxidized to CrO4 2− was rejected by the chelating cation-exchanger column. Any Cr(VI) originally present with Cr(III) could be reduced with an acidic solution of H2O2, and retained by the column yielding total Cr results, Cr(VI) being determined from the difference. The resin showed a maximal preconcentration factor of 60 for Cr(III), the LOD and LOQ being 9.3 and 30.1 nmol L−1, respectively. The developed preconcentration-speciation analysis was finished with a diphenylcarbazide (DPC) spectrophotometric procedure suitable for conventional laboratories. The resin showed excellent salt tolerance, enabling Cr analysis in seawater, and was stable over extended use. All the interferents of this procedure that normally occur in an electroplating effluent, a blended coal CRM, and a standard steel sample could be removed by the recommended procedure, by use of partial and total selectivity at the adsorption and desorption stages, respectively, enabling preconcentration and colorimetric determination of chromium in various complex matrices.
Keywords: Chromium speciation analysis; Palmitoyl oxine; XAD resin; Diphenylcarbazide; Spectrophotometry
Spectrophotometric method for the determination of manganese with phenylfluorone in the presence of Triton X-100 and cetylpyridinium chloride in pharmacological preparations and vegetable fertilizers by Wanda Winkler; Franciszek Buhl; Agata Arenhövel-Pacuła; Urszula Hachuła (pp. 934-937).
A simple and very sensitive method for the spectrophotometric determination of manganese in pharmacological preparations and vegetable fertilizers is proposed. The method is based on the formation of a blue coloured complex of Mn (II) with 9-phenyl-2,3,7-trihydroxy-6-fluorone (PF) in the presence of cetylpyridinium chloride (CP) and Triton X-100. Optimum concentrations of PF, CP, Triton X-100 and pH ensuring maximum absorbance were defined. The complex Mn(II)-PF-CP-Triton X-100 shows maximum absorbance at 591 nm with the molar absorptivity value 1.77×105 L mol−1 cm−1. The detection limit of the method is 0.004 μg mL–1. The Beer's law is obeyed for manganese concentrations in the range 0.02–0.2 μg mL−1. The effect of foreign ions was elucidated. The statistical evaluation of the method was carried out for six determination using 5 μg Mn and the following results were obtained: standard deviation 0.021, confidence interval 5.05±0.05 μg Mn. The method has been applied for the determination of manganese in pharmacological preparations (Biovital, Kinder Biovital) and vegetable fertilizers (Hydrovit 100, Florovit).
Keywords: Manganese; Phenylfluorone; Surfactants; Spectrophotometry; Pharmaceuticals; Fertilizers