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Analytical and Bioanalytical Chemistry (v.388, #2)

Teaching analytical atomic spectroscopy advances in an environmental chemistry class using a project-based laboratory approach: investigation of lead and arsenic distributions in a lead arsenate contaminated apple orchard by Dulasiri Amarasiriwardena (pp. 307-314).

is Professor of Chemistry at Hampshire College, Amherst, MA, USA. He regularly teaches analytical chemistry, environmental chemistry, and general chemistry. His research is focused on the identification and the transport and fate of trace metals in soil and aquatic environments. This includes chemical speciation of arsenic and antimony and characterization of trace metals bound to soil-derived humic acids by size-exclusion chromatography or ion chromatography coupled with inductively coupled plasma mass spectrometry (ICP-MS). He is also interested in the application of laser ablation ICP-MS for investigation of past trace metal nutrition and the exposure to toxic metal pollutants using hard tissue such as human teeth.

Mercury analysis by Milena Horvat; Holger Hintelmann (pp. 315-317).

is currently Head of the Department of Environmental Sciences of the Jožef Stefan Institute (IJS) in Ljubljana. The Department’s principal work is to monitor sources, concentrations, pathways, exposure, and effects of pollutants (radioactivity, trace and major elements, persistent organic pollutants) and to understand and assess their effects in man and his environment. She is a principal coordinator for a programme on biological and geological cycling of contaminants in the environment and also coordinates a Centre of Excellence on Environmental Technologies. She chaired the 7th International Conference on Mercury as a Global Pollutant (ICMGP) in Ljubljana, Slovenia, 2004. At the 8th ICMGP, Madison, 2006 she was a member of the Steering Committee and panel member dealing with contaminated fisheries. is a Full Professor at Trent University, Peterborough, Ontario, Canada where he chairs the Chemistry Department. He recently completed his NSERC Industry Research Chair in Environmental Modeling and received a Premier’s Research Excellence Award (Ontario). His research is conducted at Trent’s unique Worsfold Water-Quality Centre where, with the aid of a multicollector ICP–MS, he and his co-workers are studying the fractionation of non-traditional isotopes, for example mercury and selenium. He is a principal investigator in the METAALICUS project and explores the challenges posed by new methylmercury formation during wetland restoration efforts. He is also a member of the international advisory board of Analytical and Bioanalytical Chemistry. (Holger Hintelmann and his research group enjoying the closing moments of the conference. From left to right: M. Dzurko, D. Acha, H. Hintelmann, D. Foucher, O. Clarisse, R. Bona, and C. Pabon)

Laboratory simulation of Hg⁰ emissions from a snowpack by Aurélien Dommergue; Enno Bahlmann; Ralf Ebinghaus; Christophe Ferrari; Claude Boutron (pp. 319-327).

Snow surfaces play an important role in the biogeochemical cycle of mercury in high-latitude regions. Snowpacks act both as sources and sinks for gaseous compounds. Surprisingly, the roles of each environmental parameter that can govern the air–surface exchange over snow are not well understood owing to the lack of systematic studies. A laboratory system called the laboratory flux measurement system was used to study the emission of gaseous elemental mercury from a natural snowpack under controlled conditions. The first results from three snowpacks originating from alpine, urban and polar areas are presented. Consistent with observations in the field, we were able to reproduce gaseous mercury emissions and showed that they are mainly driven by solar radiation and especially UV-B radiation. From these laboratory experiments, we derived kinetic constants which show that divalent mercury can have a short natural lifetime of about 4–6 h in snow.

Keywords: Flux chamber; Snow; Gaseous mercury; Air; Photochemical reaction

Simultaneous determination of trace levels of ethylmercury and methylmercury in biological samples and vaccines using sodium tetra(n-propyl)borate as derivatizing agent by Darija Gibičar; Martina Logar; Nuša Horvat; Andreja Marn-Pernat; Rafael Ponikvar; Milena Horvat (pp. 329-340).

Because of increasing awareness of the potential neurotoxicity of even low levels of organomercury compounds, analytical techniques are required for determination of low concentrations of ethylmercury (EtHg) and methylmercury (MeHg) in biological samples. An accurate and sensitive method has been developed for simultaneous determination of methylmercury and ethylmercury in vaccines and biological samples. MeHg and EtHg were isolated by acid leaching (H₂SO₄–KBr–CuSO₄), extraction of MeHg and EtHg bromides into an organic solvent (CH₂Cl₂), then back-extraction into Milli-Q water. MeHg and EtHg bromides were derivatized with sodium tetrapropylborate (NaBPr₄), collected at room temperature on Tenax, separated by isothermal gas chromatography (GC), pyrolysed, and detected by cold-vapour atomic fluorescence spectrometry (CV AFS). The repeatability of results from the method was approximately 5–10% for EtHg and 5–15% for MeHg. Detection limits achieved were 0.01 ng g⁻¹ for EtHg and MeHg in blood, saliva, and vaccines and 5 ng g⁻¹ for EtHg and MeHg in hair. The method presented has been shown to be suitable for determination of background levels of these contaminants in biological samples and can be used in studies related to the health effects of mercury and its species in man. This work illustrates the possibility of using hair and blood as potential biomarkers of exposure to thiomersal.

Keywords: Ethylmercury; Methylmercury; Biological samples; Vaccines; Thiomersal

Thiourea catalysis of MeHg ligand exchange between natural dissolved organic matter and a thiol-functionalized resin: a novel method of matrix removal and MeHg preconcentration for ultratrace Hg speciation analysis in freshwaters by Brian R. Vermillion; Robert J. M. Hudson (pp. 341-352).

Ultratrace analysis of dissolved MeHg in freshwaters requires both dissociation of MeHg from strong ligands in the sample matrix and preconcentration for detection. Existing solid phase extraction methods generally do not efficiently adsorb MeHg from samples containing high concentrations of natural dissolved organic matter. We demonstrate here that the addition of 10–60 mM thiourea (TU) quantitatively releases MeHg from the dissolved matrix of freshwater samples by forming a more labile complex (MeHgTU⁺) that quantitatively exchanges MeHg with thiol-functionalized resins at pH∼3.5 during column loading. The contents of these columns were efficiently eluted with acidified TU and MeHg was analyzed by Hg–TU complex ion chromatography with cold-vapor atomic fluorescence spectrometry detection. Routinely more than 90% of MeHg was recovered with good precision (average relative standard deviation of 6%) from natural waters—obtained from pools and saturated sediments of wetlands and from rivers—containing up to 68.7 mg C L⁻¹ dissolved organic matter. With the preconcentration step, the method detection limit of 0.29 pg absolute or 0.007 ng L⁻¹ in 40-mL samples is equivalent to that of the current state-of-the- art as practiced by skilled analysts. MeHg in 20–50-mL samples was completely trapped. On the basis of our knowledge of the chemistry of the process, breakthrough volume should depend on the concentrations of TU and H⁺. At a TU concentration of 12 mM breakthrough occurred between 50 and 100 mL, but overall adsorption efficiency was still 85% at 100 mL. Formation of artifactual MeHg is minimal; only about 0.7% of ambient MeHg is artifactual as estimated from samples spiked with 4 μg L⁻¹ Hg^II.

Keywords: Methylmercury; Thiourea; Solid-phase extraction; Porewater; Speciation analysis

Reporting of variations in the natural isotopic composition of mercury by Joel D. Blum; Bridget A. Bergquist (pp. 353-359).

High-precision measurements of natural variations in the stable isotopic composition of mercury show great promise as a new tracer of mercury sources and chemical transformations in the environment. We strongly suggest that all laboratories adopt a common means of data correction, standardization, and nomenclature in order to ensure that data from various laboratories can be easily evaluated and compared. We make suggestions for mass bias correction, reporting of mass-dependent and mass-independent isotope variations, and a standard protocol for reporting analytical uncertainties. We also present our measured values for isotope ratios in several mercury standard solutions.

Keywords: Mercury; Stable isotopes; Inductively coupled plasma mass spectrometry

Analytical artifacts produced by a polycarbonate chamber compared to a Teflon chamber for measuring surface mercury fluxes by Anthony Carpi; Allan Frei; Daniel Cocris; Rachel McCloskey; Elisabeth Contreras; Kylie Ferguson (pp. 361-365).

We found significant differences in mercury fluxes measured with a dynamic surface mercury flux chamber made of Teflon versus one made of polycarbonate. While both materials responded reasonably well when virgin materials were used, the polycarbonate chamber was found to exhibit significant chamber blanks under light after it was exposed to surface mercury fluxes of >100 ng/m²/h. Most significantly, the polycarbonate chamber blocked all wavelengths of light below ∼320 nm. Given that ultraviolet radiation plays an important role in soil mercury flux, the polycarbonate chamber was found to significantly underestimate observed fluxes from background soil in both high light conditions (by 1–4-fold) and under diffuse, low light conditions (by ∼10-fold). These results suggest that Teflon produces fewer analytical artifacts in the surface emission of mercury measured with a flux chamber than polycarbonate.

Keywords: Atmosphere; Elemental mercury; Emission; Atomic fluorescence

Quartz crystal microbalance immunosensor for the detection of antibodies to double-stranded DNA by Rawil F. Fakhrullin; Victor G. Vinter; Alsu I. Zamaleeva; Maria V. Matveeva; Roustem A. Kourbanov; Belayhun K. Temesgen; Dilara G. Ishmuchametova; Zinaida I. Abramova; Olga A. Konovalova; Myakzyum K. Salakhov (pp. 367-375).

We report the development of a novel quartz crystal microbalance immunosensor with the simultaneous measurement of resonance frequency and motional resistance for the detection of antibodies to double-stranded DNA (dsDNA). The immobilization of poly(l-lysine) and subsequent complexation with DNA resulted in formation of a sensitive dsDNA-containing nanofilm on the surface of a gold electrode. Atomic force microscopy has been applied for the characterization of a poly(l-lysine)–DNA film. After the blocking with bovine serum albumin, the immunosensor in flow-injection mode was used to detect the antibodies to dsDNA in purified protein solutions of antibodies to dsDNA and to single-stranded DNA, monoclonal human immunoglobulin G, DNase I and in blood serum of patients with bronchial asthma and systemic lupus erythematosus. Experimental results indicate high sensitivity and selectivity of the immunosensor.

Keywords: Quartz crystal microbalance; Atomic force microscopy; Antibodies to double-stranded DNA; Systemic lupus erythematosus; Bronchial asthma; Immunosensor

New cloud vapor zone (CVZ) coupled headspace solid-phase microextraction technique by Yi-Ching Huang; Yi-Song Su; Sarangapani Muniraj; Weibing Zhang; Jen-Fon Jen (pp. 377-383).

A new cloud vapor zone (CVZ)-based headspace solid-phase microextraction (HS-SPME) technique has been demonstrated with the capability of heating the sample matrix and simultaneously cooling the sampling zone. A bi-temperature-controlled (BTC) system, allowing 10 mL of test sample heating and headspace external-cooling, was employed for the CVZ formation around the SPME-fiber sampling area. In the CVZ procedure, the heated headspace vapor undergoes a sudden cooling near the SPME to form a dense cloud of analyte–water vapor, which is helpful for adsorption or absorption of the analyte. The device was evaluated for the quantitative analysis of aqueous chlorothalonil. Parameters influencing sampling efficiency, e.g., SPME fiber coating, SPME sampling temperature and time, solution modifier, addition of salt, sample pH, and temperature, were investigated and optimized thoroughly. The proposed BTC-HS-SPME method afforded a best extraction efficiency of above 94% accuracy (less than 4.1% RSD, n = 7) by using the PDMS fiber to collect chlorothalonil in the headspace at 5 °C under the optimized condition, i.e., heating sample solution (added as 10% ethylene glycol and 30% NaCl, at pH 7.0) at 130 °C for 15 min. The detection was linear from 0.01 to 80 μg L⁻¹ with a regression coefficient of 0.9998 and had a detection limit of 3.0 ng L⁻¹ based on S/N = 3. Practical application was demonstrated by analyzing chlorothalonil in farm water samples with promising results and recoveries. The approach provided a very simple, fast, sensitive, and solvent-free procedure to collect analytes from aqueous solution. The approach can provide a new platform for other sensitive HS-SPME assays.

Keywords: Cloud vapor zone; Headspace; Solid-phase microextraction; Chlorothalonil

Determination of nitrogen in boron carbide by instrumental photon activation analysis by Silke Merchel; Achim Berger (pp. 385-389).

Boron carbide is widely used as industrial material, because of its extreme hardness, and as a neutron absorber. As part of a round-robin exercise leading to certification of a new reference material (ERM-ED102) which was demanded by the industry we analysed nitrogen in boron carbide by inert gas fusion analysis (GFA) and instrumental photon activation analysis (IPAA) using the ¹⁴N(γ,n)¹³N nuclear reaction. The latter approach is the only non-destructive method among all the methods applied. By using photons with energy below the threshold of the ¹²C(γ,n)¹¹C reaction, we hindered activation of matrix and other impurities. A recently installed beam with a very low lateral activating flux gradient enabled us to homogeneously activate sample masses of approximately 1 g. Taking extra precautions, i.e. self-absorption correction and deconvolution of the complex decay curves, we calculated a nitrogen concentration of 2260 ± 100 μg g⁻¹, which is in good agreement with our GFA value of 2303 ± 64 μg g⁻¹. The values are the second and third highest of a rather atypical (non-S-shape) distribution of data of 14 round-robin participants. It is of utmost importance for the certification process that our IPAA value is the only one not produced by inert gas fusion analysis and, therefore, the only one which is not affected by a possible incomplete release of nitrogen from high-melting boron carbide. Figure Twin-Detector system for analyzing spatially extended samples

Keywords: Nitrogen; Reference materials; Gas fusion analysis; Photon activation analysis

Stir-bar-sorptive extraction, with in-situ deconjugation, and thermal desorption with in-tube silylation, followed by gas chromatography-mass spectrometry for measurement of urinary 4-nonylphenol and 4-tert-octylphenol glucuronides by Migaku Kawaguchi; Rie Ito; Norihiro Sakui; Noriya Okanouchi; Koichi Saito; Yasuo Seto; Hiroyuki Nakazawa (pp. 391-398).

A novel method, stir-bar-sorptive extraction (SBSE), with in-situ deconjugation and thermal desorption (TD) with in-tube silylation, followed by gas chromatography-mass spectrometry (GC-MS), for determination of trace amounts of 4-nonylphenol glucuronide (NP-G) and 4-tert-octylphenol glucuronide (OP-G) in human urine, is described. The method involved correction by use of stable isotopically labeled internal standards 4-(1-methyl)octylphenol-d₅ (NP-d) and deuterium 4-tert-octylphenol (OP-d). A human urine sample to which β-glucuronidase had been added was extracted for 90 min at 37 °C using a stir bar coated with a 500-μm-thick layer of polydimethylsiloxane (PDMS). NP-G and OP-G were deconjugated, becoming free 4-nonylphenol (NP) and 4-tert-octylphenol (OP). The analytes were then extracted with the PDMS stir bar and the stir bar was subjected to TD with in-tube silylation; this was followed by GC-MS in selected-ion-monitoring (SIM) mode. To optimize the conditions for SBSE with in-situ deconjugation and to test recovery, NP-G and OP-G were synthesized by a biochemical technique in our laboratory. Average recoveries from human urine samples spiked with NP-G and OP-G were between 91.9 and 95.6% with correction using the added surrogate standards. Limits of detection were 0.11 ng mL⁻¹ for NP and 0.01 ng mL⁻¹ for OP. We also measured background levels of NP-G and OP-G in six urine samples from healthy volunteers. NP and OP were detected in the samples at concentrations of 0.62–1.95 ng mL⁻¹ and <0.04–0.18 ng mL⁻¹, respectively.

Keywords: Nonylphenol; Octylphenol; Urine; Stir-bar-sorptive extraction (SBSE); In-situ deconjugation; In-tube derivatization

An electrochemiluminescent sensor for glucose employing a modified carbon nanotube paste electrode by Jinhua Chen; Zhenyu Lin; Guonan Chen (pp. 399-407).

A carbon nanotube paste (CNTP) electrode and a carbon nanotube paste/glucose oxidase (CNTP/GOx) electrode were prepared, and the electrochemiluminescent (ECL) behavior of luminol in the presence of glucose was investigated in detail at each of these electrodes. Compared to the classical carbon paste (CP) electrode, the CNTP electrode incorporating glucose oxidase greatly enhanced the response of the ECL sensor to glucose due to the electrocatalytic activity of the carbon nanotubes, the specificity of the enzymatic reaction, and the sensitivity of the luminol ECL reaction. Under optimal conditions, the electrode was found to respond linearly to glucose in the concentration range 1.0 × 10⁻⁶~2.0 × 10⁻³ mol/L, and the detection limit (defined as the concentration that can be detected at a signal-to-noise ratio of 3) was found to be a glucose concentration of 5.0 × 10⁻⁷ mol/L. The method used to prepare the CNTP/GOx electrode was very convenient, and the electrode surface could be renewed in the case of fouling by simply polishing or cutting it to expose a new and fully active surface. The relative standard deviations (RSD) were found to be 6.8% and 8.9% for the CNTP electrode and the CNTP/GOx electrode (n = 6). The electrode retained 95% of its initial response after two weeks.

Keywords: Electrochemiluminescent sensor; Glucose oxidase; Glucose; Modified carbon nanotube paste electrode

Investigation of polynuclear Zr(IV) hydroxide complexes by nanoelectrospray mass-spectrometry combined with XAFS by Clemens Walther; Jörg Rothe; Markus Fuss; Sebastian Büchner; Sergei Koltsov; Thorald Bergmann (pp. 409-431).

Polynuclear species of zirconium in acidic aqueous solution are investigated by combining X-ray absorption spectroscopy (XAFS) and nanoelectrospray mass spectrometry (ESI-MS). Species distributions are measured between pH_C 0 and pH_C 3 for [Zr] = 1.5–10 mM. While the monomer remains a minor species, with increasing pH the degree of polymerization increases and the formation of tetramers, pentamers, octamers, and larger polymers is observed. The high resolution of the mass spectrometer permits the unambiguous determination of polynuclear zirconium hydroxide complexes by means of their isotopic patterns. The relative abundances of mononuclear and polynuclear species present simultaneously in solution are measured, even if one of the species contributes only 0.1% of the Zr concentration. For the first time it has been directly observed that the hydrolysis of polynuclear Zr species is a continuous process which leads to charge compensation through the sequential substitution of water molecules by hydroxide ligands until doubly charged polymers dominate at conditions (H⁺ and Zr concentrations) close to the solubility of Zr(OH)₄(am). The invasiveness of the electrospray process was minimized by using very mild declustering conditions, leaving the polynuclear species within a solvent shell of approximately 20 water molecules. Figure Schematic Diagram of Multiplexed Measurement of 9 Anti-Nuclear Antibodies Using the AtheNa Multilyte Assay

Keywords: Zirconium; Hydrolysis; Polymerization; Nanoelectrospray; EXAFS

Profiling of amine metabolites in human biofluids by micellar electrokinetic chromatography with laser-induced fluorescence detection by Hua-Ming Tseng; Yin Li; David A. Barrett (pp. 433-439).

A rapid and sensitive capillary electrophoresis (CE) method has been developed for profiling organic metabolites containing amine functional groups in mammalian biofluids. Metabolites containing an amine group were derivatized with 4-fluoro-7-nitrobenzo-2,1,3-oxadiazol (NBD-F), separated by micellar electrokinetic chromatography (MEKC), and detected by argon-ion (488 nm) laser-induced fluorescence detection. The optimized MEKC background electrolyte conditions were: 50 mmol L⁻¹ sodium cholate, 5 mmol L⁻¹ β-cyclodextrin, and 20 mmol L⁻¹ Brij 35 in 20 mmol L⁻¹ aqueous borate buffer, pH 9.3, containing 7% methanol. Under these conditions all the amine compounds in mammalian biofluids, for example plasma, saliva, and urine, were derivatized directly, without extraction, in a minimum volume of 100 nL and the derivatives could be separated within 16 min. Up to 90% of the amine-containing metabolites in plasma and saliva could be identified by reference to standard compounds. For twenty amine standards linearity of calibration was better than R ² = 0.99. Migration-time and peak-area reproducibility were better than RSD 1.5% and 15% respectively. In replicate analysis of human plasma bioanalytical precision ranged between 0.7 and 3.8 RSD% for a 5.0-μL volume and between 1.7 and 5.5 RSD% for 100-nL volume. The concentrations measured were found to be in agreement with literature values.

Keywords: Metabolite profiling; Amines; Micellar electrokinetic chromatography; NBD-F; Laser-induced fluorescence; Plasma; Urine; Saliva

Determination of major and trace elements in human scalp hair by pressurized-liquid extraction with acetic acid and inductively coupled plasma–optical-emission spectrometry by Jorge Moreda-Piñeiro; Elia Alonso-Rodríguez; Purificación López-Mahía; Soledad Muniategui-Lorenzo; Darío Prada-Rodríguez; Antonio Moreda-Piñeiro; Pilar Bermejo-Barrera (pp. 441-449).

An analytical method has been developed for determination of major (Ca, K, Mg, and Na) and trace elements (As, Cd, Co, Li, Ni, and Sr) in human scalp hair. The proposed method includes a novel, simple, rapid, highly efficient, and automated metal-leaching procedure, by pressurized-liquid extraction (PLE), combined with a rapid simultaneous detection system—inductively coupled plasma–optical-emission spectrometry (ICP–OES). PLE is one of the most promising recently introduced sample-preparation techniques, with the advantages of reducing solvent consumption and enabling automated sample handling. The operating conditions for PLE, including concentration of the extraction solvent, extraction temperature, static time, number of extraction steps, pressure, mean particle size, diatomaceous earth (DE) mass/sample mass ratio, and flush volume were studied using an experimental design (Plackett–Burman design, PBD). The optimum conditions were use of 0.75 mol L⁻¹ acetic acid as extracting solution and powdered hair samples thoroughly mixed with DE, as a dispersing agent, at a DE mass/sample mass ratio of 4. Extraction was performed at room temperature and an extraction pressure of 140 atm for 5 min in one extraction step. The flush volume was fixed at 60%. The PLE-assisted multi-element leaching proposed is complete after 7 min (5 min static time plus 1 min purge time plus 1 min end relief time). Under the optimised conditions the figures of merit, for example limits of detection and quantification, repeatability of the over-all procedure, and accuracy, were evaluated. Analysis of GBW-07601 (human hair) certified reference material revealed accuracy was good for the target elements. The optimised method was finally applied to several human scalp-hair samples.

Keywords: PLE; Acetic acid; Major and trace elements; Human scalp hair; ICP–OES

Focused microwave-assisted Soxhlet extraction of acorn oil for determination of the fatty acid profile by GC–MS. Comparison with conventional and standard methods by J. A. Pérez-Serradilla; M. C. Ortiz; L. Sarabia; M. D. Luque de Castro (pp. 451-462).

A study of the feasibility of focused microwave-assisted Soxhlet extraction of acorn oil and comparison of results from analysis of trans fatty acids in the oil thus obtained with those for oils obtained by use of other methods commonly used for oil extraction are reported here. The proposed method was optimized by means of a 21-experiment screening design to determine, by means of a reduced number of experiments, which factors affect both extraction efficiency and the degree of unsaturation of the fatty acids in the oil. The proposed method enables total extraction of the fatty acids in 30 min, which is much less than the time required by the Folch (4.5 h), Soxhlet (16 h), and ISO (8 h) reference methods and the stirring–extraction method (56 h). The efficiency of extraction achieved by use of the proposed method is statistically equivalent to that achieved by use of the other methods; the composition of the extracts obtained by use of the proposed method and the Folch and stirring reference methods are also statistically similar. No trans fatty acids were present in the extracts obtained by use of the Folch, stirring, and proposed methods but they were detected in the extracts obtained by use of both the Soxhlet and ISO methods.

Keywords: Focused microwave-assisted extraction; Comparison of extraction methods; Chemometric approaches; Fatty acids; Acorns

Simultaneous determination of speciation parameters of Cu, Pb, Cd and Zn in model solutions of Suwannee River fulvic acid by pseudopolarography by Parthasarathi Chakraborty; Ismail I. Fasfous; John Murimboh; Chuni L. Chakrabarti (pp. 463-474).

There is a growing awareness of the importance of quantitative determinations of speciation parameters of the trace metals Cu, Zn, Cd and Pb in aqueous samples containing chemically heterogeneous humic substances, especially when they are present together, interacting with one another and competing for specific binding sites of the humic substances. Such determinations require fundamental knowledge and understanding of these complex interactions, gained through basic laboratory-based studies of well-characterized humic substances in model solutions. Since the chemical heterogeneity of humic substances plays an important role in the thermodynamics (stability) and kinetics (lability) of trace metal competition for humic substances, a metal speciation technique such as pseudopolarography that can reveal the special, distinctive nature of metal complexation is required, and it was therefore used in this study. A comparison of the heterogeneity parameters (Γ) for Zn(II), Cd(II), Pb(II) and Cu(II) complexes in model solutions of Suwannee River fulvic acid (SRFA) shows that Γ_Cd>Γ_Zn>Γ_Pb>Γ_Cu, suggesting that SRFA behaves as a relatively homogeneous complexant for Zn(II) and Cd(II), whereas it behaves as a relatively heterogeneous complexant for Pb(II) and an even more heterogeneous complexant for Cu(II) under the experimental conditions used. The order of values of logK* (from the differential equilibrium function, DEF) for the trace metals at pH 5.0 follow the sequence: $$log K^{ * }_{{{ ext{Cu}}}} > log K^{ * }_{{{ ext{Pb}}}} > log K^{ * }_{{{ ext{Zn}}}} > log K^{ * }_{{{ ext{Cd}}}} $$ These results are in good agreement with the literature values. The results of this work suggest the possibility of simultaneously determining several metals in a sample in a single experiment, and hence in a shorter time than required for multiple experiments.

Keywords: Simultaneous determination; Suwannee River fulvic acid; Trace metal speciation; Metal complexation; Pseudopolarography

Simultaneous determination of p-hydroxyacetophenone, chlorogenic acid, and caffeic acid in Herba Artemisiae Scopariae by capillary electrophoresis with electrochemical detection by Xiao Yao; Gang Chen (pp. 475-481).

Capillary electrophoresis with electrochemical detection has been employed for the determination of p-hydroxyacetophenone, chlorogenic acid, and caffeic acid in Herba Artemisiae Scopariae (the dried sprout of Artemisia scoparia Waldst. et Kit.). The effects of several important factors, such as the concentration and the acidity of the running buffer, separation voltage, injection time, and detection potential, were investigated to acquire the optimum conditions. The detection electrode was a 300-μm-diameter carbon disc electrode at a working potential of +0.90 V (relative to the saturated calomel electrode). The three analytes can be well separated within 11 min in a 40-cm-long fused-silica capillary at a separation voltage of 15 kV in 50 mM borate buffer (pH 9.2). The relation between peak current and analyte concentration was linear over about 3 orders of magnitude, with detection limits (signal-to-noise ratio of 3) of 0.31, 0.39, and 0.50 μM for p-hydroxyacetophenone, chlorogenic acid, and caffeic acid, respectively. The proposed method has been successfully applied to monitor the three bioactive constituents in real plant samples and to differentiate between different herbal drugs with satisfactory assay results.

Keywords: Herba Artemisiae Scopariae; p-Hydroxyacetophenone; Chlorogenic and caffeic acids; Capillary electrophoresis; Electrochemical detection

Evaluation of two methods for the extraction of antioxidants from medicinal plants by Hua-Bin Li; Yue Jiang; Chi-Chun Wong; Ka-Wing Cheng; Feng Chen (pp. 483-488).

The efficiencies of two traditional extraction methods used in Chinese medicine (the decoction method and the maceration method) were evaluated for the extraction of antioxidants from medicinal plants. A group of medicinal plants possessing nutritious and tonic functions were chosen as model plants. A commonly used extraction method was used as a reference method. The antioxidant capacities and total phenolic contents of the extracts were measured by ferric-reducing antioxidant power and Trolox equivalent antioxidant capacity assays as well as the Folin–Ciocalteu method, respectively. The results obtained indicated that the two traditional extraction methods could effectively extract antioxidants from medicinal plants. These extraction methods can be applied to the analysis and purification of antioxidants in plants, respectively. At home, people can use these methods to extract antioxidants from plants for consumption. In the food industry, these methods could be utilized to prepare crude extracts from plants containing antioxidants for use as food additives. Figure Relation and comparison of extraction efficiencies of two traditional extraction methods with the reference method

Keywords: Extraction method; Antioxidant; FRAP assay; TEAC assay; Polyphenol

Determination of triadimenol based on the quenching effect on resonance light scattering from the triadimenol–deoxyribonucleic acid–hydrochloric acid system by Fengpei Du; Xiaolin Luo; Guibin Jiang; Shicong Hou; Gang Liu; Liping Ren; Li Zhang; Qin Huang; Nianqin Jie (pp. 489-493).

Analysis of triadimenol was carried out using deoxyribonucleic acids (DNA) via the resonance light scattering (RLS) technique. After adding triadimenol into aqueous medium of pH 1.72, the RLS of DNA was remarkably quenched. A resonance light scattering peak at 310 nm was found, and the quenched intensity of RLS at this wavelength was proportional to the concentration of triadimenol. The linear range of the calibration curve was approximately 0–3 μg mL⁻¹ with a detection limit (S/N = 3) of 0.07 μg mL⁻¹. The triadimenol in samples of water, cucumber and human serum was determined. The results were satisfactory, and the recovery rates were in the range of 96.3–106.0%, 94.8–105.9% and 92.3–100.5%, respectively. The interaction mechanism was also studied.

Keywords: Triadimenol; Resonance light scattering method; Deoxyribonucleic acids (DNA)

Instrumental modification intended to save time, and volumes of sample and reagent solutions, in the atomic fluorescence spectrometric determination of mercury by Carmen Pérez-Sirvent; María J. Martínez-Sánchez; Mariluz García-Lorenzo; Ignacio López-García; Manuel Hernández-Córdoba (pp. 495-498).

Use of small membrane pumps, instead of peristaltic pumps, to introduce sample and reagent solutions into the spectrometer has several advantages in atomic fluorescence spectrometric determination of mercury. This simple modification results in a substantial saving in the time required for the measurements and so 90% of reagent solution volumes and 95% of sample solution volumes are saved, with a consequent decrease in the volume of waste generated. The sampling frequency is almost tripled, with no deterioration in sensitivity, which is similar to that obtained by use of peristaltic pumps. The relative standard deviation for ten consecutive measurements of a 1 μg L⁻¹ mercury solution was approximately 2%. Figure Small membrane pumps for the atomic fluorescene spectro metric determination of mercury

Keywords: Mercury; Atomic fluorescence spectrometry; Instrumentation; Multipumping

Assessment of chemical purity of ¹⁰B-enriched p-boronophenylalanine by high-performance liquid chromatography coupled on-line with inductively coupled plasma optical emission spectrometry by Eduardo A. Gautier; María J. Roberti; Raquel T. Gettar; Raúl Jiménez Rebagliati; Daniel A. Batistoni (pp. 499-503).

A dual-detection technique, consisting of a combination of reversed-phase high-performance liquid chromatography and on-line detection of elemental boron in the column effluents by inductively coupled plasma optical emission spectrometry, was tested for drug analysis. The method was applied to assessing the chemical purity of p-boronophenylalanine (BPA), isotopically enriched in ¹⁰B. This compound is employed as a fructose complex solution for biodistribution studies in laboratory and clinical trials of boron neutron capture therapy. Besides the determination of the content of BPA, required for chemical quality controls of solutions of the complex used for infusions, resolution of mixtures of BPA and two usually accompanying residual impurities (phenylalanine and tyrosine) was achieved with UV detection. The limits of detection (in solution) were 1.5 and 0.6 ng ml⁻¹, respectively. In addition, by monitoring a sensitive-element emission wavelength it was possible to jointly observe the elution of boron-containing compounds that may be transparent to UV radiation or to confirm the presence of boron in potential impurities accompanying the drug. Those impurities may arise from the BPA synthesis or may be produced by degradation during the aging of the solutions. Chromatographic peaks corresponding to the amino acids and also to a related inorganic compound were detected in BPA–fructose complex solutions that were stored for different times and under different conditions. An increase in the areas of the peaks attributed to tyrosine and phenylalanine was observed for BPA–fructose solutions stored refrigerated for 1 month to 1 year, suggesting that degradation processes able to reduce the amount of bioavailable BPA could be active.

Keywords: Bioanalytical methods; p-Boronophenylalanine; Drug monitoring; High-performance liquid chromatography; UV–vis; Inductively coupled plasma optical emission spectrometry

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Analytical and Bioanalytical Chemistry (v.388, #2)

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Analytical and Bioanalytical Chemistry (v.388, #2)