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Analytica Chimica Acta (v.530, #1)

Outside front cover - Editorial Board (pp. co1).

Contents (pp. v-vi).

Calendar of forthcoming meetings (pp. n1-n3).

Cholinesterase immobilisation on the surface of screen-printed electrodes based on concanavalin A affinity by Bogdan Bucur; Andrei Florin Danet; Jean-Louis Marty (pp. 1-6).

This paper reports a new method for the immobilisation of acetylcholine esterase (AChE) on the surface of screen-printed electrodes (SPEs) based on the affinity between the glycoprotein enzyme and concavalin A (Con A). The surface of the working electrode has been modified with a Nafion layer that contains graphite, the mediator 7,7,8,8-tetracyanoquinodimethane (TCNQ) and heptylamine. The enzyme-free SPEs were characterised by cyclic voltammetry in buffer solutions and amperometry using cysteamine as analyte. The AChE immobilisation process leads to the sandwich structure: electrode–carbohydrate–Con A–enzyme. The first step of the immobilisation is the covalent activation of an amino group bound in a Nafion layer. The following steps are based on the affinity. The non-specific adsorption has been totally eliminated using BSA solutions at two different pHs. Various amounts of enzyme, from 0.1 to more than 2mIU AChE, have been loaded on the electrode surface. The method offers the advantage of a free diffusion, which allows obtaining a response time of less than 2min. An operational stability of more than 10 measurements was registered, while the active surface of the electrode was successfully reloaded for three consecutive times without any important change of the analytical performances.

Keywords: Affinity immobilisation; Concanavalin A; Acetylcholine esterase; Screen-printed biosensors

Spectroscopic study of the water-soluble organic matter isolated from atmospheric aerosols collected under different atmospheric conditions by Regina M.B.O. Duarte; Casimiro A. Pio; Armando C. Duarte (pp. 7-14).

The composition of the water-soluble organic matter from fine aerosols collected in a rural location during two different meteorological conditions (summer and autumn) was investigated by UV–vis, synchronous fluorescence (with Δ λ = 20nm), FT-IR and CPMAS-¹³C NMR spectroscopies. A seasonal variation in the concentration of total carbon, organic carbon and water-soluble organic carbon was confirmed, with higher values during the autumn and lower values during the summer season. The chemical characterisation of the water-soluble organic matter showed that both samples are dominated by a high content of aliphatic structures, carboxyl groups and aliphatic carbons single bonded to one oxygen or nitrogen atom. However, the autumn sample exhibits a higher aromatic content than the summer sample, plus signals due to carbons of phenol, ketones and methoxyl groups. These signals were attributed to lignin breakdown products which are likely to be released during wood combustion processes. The obtained results put into evidence the major contribution of biomass burning processes in domestic fireplaces during low temperature conditions into both the concentration and the bulk chemical properties of the WSOC from fine aerosols.

Keywords: Atmospheric aerosols; Water-soluble organic compounds; Synchronous fluorescence spectroscopy; UV–vis spectroscopy; FT-IR spectroscopy; CPMAS-; ¹³; C NMR

Determination of mannitol and three sugars in Ligustrum lucidum Ait. by capillary electrophoresis with electrochemical detection by Gang Chen; Luyan Zhang; Xingliang Wu; Jiannong Ye (pp. 15-21).

A method based on capillary electrophoresis with electrochemical detection has been developed for the separation and determination of mannitol, sucrose, glucose, and fructose in Ligustrum lucidum Ait. for the first time. Effects of several important factors such as the concentration of NaOH, separation voltage, injection time, and detection potential were investigated to acquire the optimum conditions. The detection electrode was a 300μm diameter copper disc electrode at a working potential of +0.65V (versus saturated calomel electrode (SCE)). The four analytes can be well separated within 13min in a 40cm length fused-silica capillary at a separation voltage of 12kV in a 75mM NaOH aqueous solution. The relation between peak current and analyte concentration was linear over about three orders of magnitude with detection limits ( S/ N = 3) ranging from 1 to 2μM for all analytes. The proposed method has been successfully applied to monitor the mannitol and sugar contents in the plant samples at different growth stages with satisfactory assay results.

Keywords: Ligustrum lucidum; Ait.; Mannitol; Sucrose; Glucose; Fructose; Capillary electrophoresis; Electrochemical detection

Determination of dimetridazole and metronidazole in poultry and porcine tissues by gas chromatography–electron capture negative ionization mass spectrometry by Clare Ho; Della W.M. Sin; K.M. Wong; Hubert P.O. Tang (pp. 23-31).

A sensitive and selective method using gas chromatography–electron capture negative ionization mass spectrometry (GC–ECNI-MS) for analysis of dimetridazole (DMZ) and metronidazole (MNZ) in poultry muscles, porcine kidney and liver, and chicken liver, was developed and validated for the purpose of food surveillance testing of the residues of these two nitroimidazoles in various types of animal tissues in the Hong Kong Special Administrative Region. Before homogenization and extraction with toluene, [2H₃]dimetridazole-(DMZ-d³) and secnidazole (SNZ) were added to tissue samples as internal standards. The organic extracts were mixed with n-hexane and subject to solid-phase extraction cleanup by amine extraction columns. MNZ and SNZ were derivatized with BSA prior to GC–ECNI-MS determination. Good recovery and precision were obtained and the limit of detection was below parts per billion levels for poultry and porcine tissues. The method could also be applied for the detection of the hydroxylated metabolite of DMZ.

Keywords: Dimetridazole; Metronidazole; Poultry tissues; Porcine tissues; Gas chromatography–electron capture negative ionization mass spectrometry

Application of novel activated carbon fiber solid-phase, microextraction to the analysis of chlorinated hydrocarbons in water by gas chromatography–mass spectrometry by Tonghua Sun; Jinping Jia; Nenghu Fang; Yalin Wang (pp. 33-40).

This paper presents a study on the performance of activated carbon fiber (ACF) used as extraction fiber for solid-phase microextraction (SPME) and its application for analysis of chlorinated hydrocarbons in water. By means of evaluating scanning electron microscope (SEM) images, specific surface area, pore volume, pore distribution, and properties of adsorption and desorption, the optimal active concentration of phosphoric acid has been determined. Coupled with gas chromatograph–mass spectrometry (GC–MS), ACF-SPME is suitable for determination chlorinated hydrocarbons in water with headspace. Experimental parameters such as adsorption and desorption conditions were studied. The optimized method has an acceptable linearity, good precision, with R.S.D. values <10% for each compound. Compared with commercial fibers, ACF has many advantages such as better resistance to organic solvents, better endurance to high temperature and longer lifetime.

Keywords: Solid-phase microextraction; Activated carbon fiber; Phosphoric acid; Surface area; Porosity; Chlorinated hydrocarbons; HS–GC–MS

Application of ion chromatography to qualitative and quantitative determination of the main inorganic ionic components of samples from a production process of potassium sulphate by Maria A. Giambra (pp. 41-48).

This review presents the possibility to use ion chromatography (IC) to analyse solids and brines deriving from treatment procedures of potassium salts. Qualitative and quantitative determination of ions samples has been used to make their chemical reconstruction. By using conventional calibration methods covering the whole concentration interval, analysis were not suitably accurate. During this process, the analysis is considered acceptable when the difference between the sum of the equivalents of cations and anions (Δ E) is ≤2%. For the process, a calibration method has been used employing four reference curves; each defined by three points corresponding to three standards purposely devised in our laboratory. The composition of the standards matched that expected for the samples from the different stages of the process reaction, after their usual sampling, dissolution and dilution. By comparing the conductivity of the analyte in the real sample to the conductivity of the same analyte in a standard, the effects of other analytes present in the medium are practically cancelled and need not be considered. The IC method results are in good agreement with conventional analysis methods (potentiometric titration, atomic absorption, gravimetric analysis).

Keywords: Ion chromatography; Mine process; (Potassium) salts; Inorganic ions; Calibration method

Mucin/carbopol matrix to immobilize oxalate oxidase in a urine oxalate amperometric biosensor by R.H. Capra; M. Strumia; P.M. Vadgama; A.M. Baruzzi (pp. 49-54).

An enzymatic amperometric electrode with extended analytical range and improved stability for oxalate determination has been developed. Glutarlaldehyde/mucin/carbopol matrix was used for the crosslinking of the enzyme between polymeric membranes to form a classical laminate construction (sandwich) and compared with the glutaraldehyde/mucin/enzyme and glutaraldehyde/albumin/enzyme.The use of a sulphonated membrane as internal membrane allowed rejection of the most important electrooxidable urine interferents. The recovery assays were highly satisfactory. The wide linear response in the range 2–400μM after 1/10 urine dilution (corresponding to 20–4000μM) made it suitable for clinical range. High correlation with the standard spectrophotometric method was obtained ( r² = 0.98, y = 0.89 x, n = 25).

Keywords: Mucin; Carbopol; Oxalate biosensor; Amperometric biosensor; Oxalate oxidase

A novel optical sensor for uranium determination by Afsaneh Safavi; Mozhgan Bagheri (pp. 55-60).

A metal ion indicator, Alizarin Red S, was tested for its potential use in uranium selective optode membrane. The water-soluble indicator was lipophilized in the form of an ion pair with tetraoctylammonium bromide, and subsequently immobilized on a triacetyl cellulose membrane. The membrane responds to uranium ions, giving a color change from yellow to violet in acetate buffer pH 5. This optode has a linear range of (1.70–18.7) × 10⁻⁵M of UO₂²⁺ ions with a limit of detection of 5 × 10⁻⁶M. The response time of optode was within 6min depending on the concentration of UO₂²⁺ ions. The sensor can readily be regenerated with hydrochloric acid solution (0.01M). The optode is fully reversible.

Keywords: Uranium; Optode; Alizarin Red S

Miniaturised stripping-based carbon modified sensor for in field analysis of heavy metals by Ilaria Palchetti; Serena Laschi; Marco Mascini (pp. 61-67).

A new miniaturised electrochemical carbon modified sensor for on-site stripping analysis of trace heavy metals is described. The graphite working electrode is modified with a cellulose-derivative mercury coating. A detailed description of the construction of the system as well as the systematic laboratory test carried out to optimise its performance is reported. Coupling this sensor with square wave (SW) anodic stripping analysis, detection limits of 0.3, 1 and 0.5μgl⁻¹ were found for lead(II), cadmium(II) and copper(II), respectively. Deoxygenation of sample solution is not required. The entire analysis time is shorter than 4min.Examples of on-site environmental applications are given. In particular, on-site analysis of heavy metals was performed at a contaminated site. For this purpose, the sensor was coupled with a portable commercial electroanalytical instrumentation.

Keywords: Stripping voltammetry; Screen-printed electrodes; Mercury-coating; Heavy metals; On-site analysis; Soil; Sediments; Wastewater

Electrochemical determination of 2,4-D at a mercury electrode by N. Maleki; A. Safavi; H.R. Shahbaazi (pp. 69-74).

An indirect electrochemical determination of 2,4-dichlorophenoxyacetic acid (2,4-D), has been presented. The method is based on the adsorption and desorption of 2,4-D on mercury electrode. Also, the electrochemical behavior of 2,4-D in aqueous solutions at different pH values and different 2,4-D concentrations were studied. A simple and rapid method has been developed for its extraction from water and soil. The subsequent determination was carried out by a tensammetric method. Three calibration curves could be obtained from different parts of voltammogram. Under the optimum conditions (pH = 2.3; E_acc = −1100mV; t_acc = 60s; alternative current mode; ν = 40mVs⁻¹; pulse height = 20mV; modulation frequency = 60Hz; phase angle = 90°) the limit of detection was 50μgL⁻¹. The proposed method was applied to the determination of 2,4-D in real samples such as soil and water.

Keywords: 2,4-D; Electrochemical determination

Quartz crystal biosensor for detection of sugars and glycated hemoglobin by Jan Přibyl; Petr Skládal (pp. 75-84).

3-Aminophenylboronic acid (APBA) was used for construction of affinity mass sensors for determination of saccharides and glycated hemoglobin using complexation reaction with diol groups. Two approaches were tested for the bioligand layer fabrication—incorporation of APBA inside a thicker matrix and immobilization as a self-assembled monolayer, respectively. The direct affinity sensor with APBA embeded in the structure of glutaraldehyde-crosslinked bovine serum albumine provided linear response to mono- and dissacharides in the range from 0.1 to 15.0mg/ml. This biosensor was also used for kinetic analysis of the interaction of boronic acid with diols; the values of association and dissociation constants were determined. The sensors with a monolayer of boronic groups were better suited for binding of glycated hemoglobin, probably due to improved steric access to the ligand.

Keywords: Quartz crystal microbalance; m; -Aminophenylboronic acid; Saccharides; Glycated hemoglobin; Kinetic analysis

Transition phenomenon of immersion-angle dependence of quartz crystal microbalance in Newtonian liquid by Minoru Yoshimoto; Yasuhiro Maruyama; Shin Tokimura; Shigeru Kurosawa (pp. 85-89).

The present work reports the new effects of the immersion-angle dependence of the resonant-frequency shift (Δ F) of the one-face sealed quartz crystal microbalance (QCM) in a Newtonian liquid. The immersion-angle dependence of Δ F appears below the sucrose concentration of 12wt.%. However, we found that the transition phenomenon of Δ F occurs between 12 and 20wt.% and then the immersion-angle dependence of Δ F disappears above 20wt.% (finally, the Δ F values above 20wt.% are equal to those of 90° in all immersion angles). In order to obtain further insights into the transition phenomenon and the disappearance of the immersion-angle dependence of Δ F, we investigated the immersion-angle dependence of the electrolytic solution, i.e., NaCl solution. This investigation indicated that this monovalent electrolytic solution causes the immersion-angle dependence but not the transition phenomenon and the disappearance of the immersion-angle dependence of Δ F. On the basis of these results, we suggest that the non-charge of the molecule is the important element to generate the transition phenomenon and the disappearance of the immersion-angle dependence of Δ F.

Keywords: QCM; Immersion angle; Newtonian liquid; Electrolytic solution

Uncertainty propagation through correction methodology for the determination of rare earth elements by quadrupole based inductively coupled plasma mass spectrometry by Narendra M. Raut; Li-Shing Huang; King-Chuen Lin; Suresh K. Aggarwal (pp. 91-103).

Determination of rare earth elements by quadrupole based inductively coupled plasma mass spectrometry (ICP-QMS) shows several spectroscopic overlaps from M⁺, MO⁺ and MOH⁺ ions. Especially, the spectroscopic interferences are observed from the atomic and molecular species of lighter rare earth elements including Ba during the determination of Eu, Gd and Tb. Mathematical correction methods, knowing the at.% abundances of different interfering isotopes, and the extent of formation of molecular species determined experimentally, have been used to account for various spectroscopic interferences. However, the uncertainty propagated through the mathematical correction limits its applicability. The uncertainty propagation increases with the increase in contribution from interfering species. However, for the same extent of total contribution, the overall error decreases when the interfering species are more than one. In this work, chondrite as well as a few geological reference materials containing different proportions of various rare earth elements have been used to study the contributions of different interfering species and the corresponding uncertainty in determining the concentrations of rare earth elements. A number of high abundant isotopes are proposed for determining the concentrations of various rare earth elements. The proposed isotopes are tested experimentally for determining the concentrations of different rare earth elements in two USGS reference materials AGV-1 and G-2. The interferences over those isotopes are corrected mathematically and the uncertainties propagated due to correction methodology are determined for those isotopes. The uncertainties in the determined concentrations of rare earth elements due to interference correction using the proposed isotopes are found to be comparable with those obtained by the commonly used isotopes for various rare earth elements.

Keywords: Rare earth elements; ICP-QMS; Ultrasonication; Uncertainty propagation

Electrothermal vaporization inductively coupled plasma mass spectrometry for the determination of trace amount of lanthanides and yttrium in soil with polytetrafluroethylene emulsion as a chemical modifier by Man He; Bin Hu; Zucheng Jiang (pp. 105-112).

A method of electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) for the determination of trace lanthanides and yttrium in soil samples with a polytetrafluorethylene (PTFE) emulsion as chemical modifier to promote the vaporization of the analytes from the graphite furnace was developed in this paper. The analytical characteristics, spectral interference and matrix effect of the analytical method were evaluated and critically compared with those of pneumatic nebulization inductively coupled plasma mass spectrometry (PN-ICP-MS). Under the optimized operation conditions, the relative detection limits of lanthanides (La–Lu) and yttrium for ETV-ICP-MS and PN-ICP-MS were 0.4–20ngl⁻¹ and 1.0–21ngl⁻¹, respectively, the absolute detection limits for ETV-ICP-MS were 4–200fg, which were improved by 1–2 orders of magnitude compared with PN-ICP-MS. While the analytical precision of ETV-ICP-MS is worse than that of PN-ICP-MS, with the R.S.D.s (%) of 4.1–10% for the former and 2.9–7.8% for the latter. Regarding to the matrix effect, both conventional method and stepwise dilution method were employed to observe the effect of matrix and the very similar results were obtained. It was found that the highest tolerance concentration of the matrix is 1000mgl⁻¹ and 800mgl⁻¹ for ETV-ICP-MS and PN-ICP-MS, respectively. To assess the accuracy, the proposed method was applied to the determination of trace lanthanides and yttrium in three different soil standard reference materials and one soil sample, and the determined values are in good agreement with the certified values or reference values.

Keywords: ETV-ICP-MS; Lanthanides; Yttrium; Soil; Matrix effect; Polytetrafluorethylene

Antimony determination and speciation by multisyringe flow injection analysis with hydride generation-atomic fluorescence detection by N.V. Semenova; L.O. Leal; R. Forteza; V. Cerd� (pp. 113-120).

A new analytical procedure for determination of inorganic antimony and speciation of antimony(III) and antimony(V) is presented. For this purpose, a software-controlled time-based multisyringe flow injection system, which contains a multisyringe burette provided with a multi-port selection valve, was developed. Hydride generation-atomic fluorescence spectrometry was used as a detection technique. A 0.3% (w/v) reducing sodium tetrahydroborate solution, hydrochloric acid (2M), an antimony solution and a pre-reducing solution of 10% (w/v) KI and 0.3% (w/v) ascorbic acid are dispensed simultaneously into a gas–liquid separation cell with further propulsion of the reaction product into the flame of an atomic fluorescence spectrometer using argon flow. A hydrogen flow was employed to support the flame.The linear range and the detection limit (3s_b/S) of the proposed technique were 0.2–5.6μgl⁻¹ and 0.08μgl⁻¹, respectively. A sample throughput of 18 samples per hour (corresponding to 80 injections per hour) was achieved. The relative standard deviation for 18 independent measurements was 4.6%. This technique was validated by means of reference solid and water materials with good agreement with the certified values. Satisfactory results for speciation of Sb(III) and Sb(V) by means of the developed technique were obtained.

Keywords: Antimony; Multisyringe flow injection analysis (MSFIA); Speciation; Hydride generation; Atomic fluorescence spectrometry; Water samples; Lead concentrate sample

Determination of iron and copper in seawater at pH 1.7 with a new commercially available chelating resin, NTA Superflow by Maeve C. Lohan; Ana M. Aguilar-Islas; Robert P. Franks; Kenneth W. Bruland (pp. 121-129).

The use of a commercially available chelating resin with NTA-type functional groups for concentration of trace metals from seawater is described. Trace metal recoveries from this NTA Superflow chelating resin are pH dependent. At a pH of ≤2 only iron(III) and copper are quantitatively recovered from the resin. Iron(II) cannot be quantitatively recovered from this resin below a pH of 5. However, oxidation of acidified seawater samples (pH 1.7) with H₂O₂ prior to loading onto the resin has been demonstrated to allow quantitative recovery of total dissolved iron. Deferrioxamine and Rhodoturlic Acid, two commercially available siderophores were used to investigate the effect of strong Fe(III)-binding organic ligands on the ability to retain iron at different pH values. Acidification of seawater samples to pH 1.7 dissociates the iron complexed to these organic ligands, thereby allowing total dissolved iron and copper to be determined. Acidified samples from Monterey Bay were analyzed by a flow injection method coupled to ICP-SFMS detection using the NTA Superflow resin in the pre-concentration step. Results from this study show that when seawater samples are stored acidified (pH 1.7) over time, a portion of iron(III) is reduced to iron(II), thus necessitating the use of H₂O₂ to reoxidize the Fe(II) to Fe(III) prior to analysis. Total dissolved concentrations of iron and copper can be directly obtained on seawater samples at pH 1.7 with this method, eliminating the need to buffer the sample to a higher pH prior to column loading. This resin has the potential to be used in shipboard or in situ flow injection methods.

Keywords: NTA; Chelating resin; Iron; Copper; Organic complexation; pH

A new resonance scattering spectral method for the determination of trace amounts of iodate with rhodamine 6G by Ai-Hui Liang; Zhi-Liang Jiang; Biao-Ming Zhang; Qing-Ye Liu; Jie Lan; Xi Lu (pp. 131-134).

Under the conditions of 0.04molL⁻¹ HCl–8.0 × 10⁻⁴molL⁻¹ KI, there is a fluorescence peak at 540nm and a synchronous fluorescence peak at 540nm for rhodamine 6G (RhG). When there is IO₃⁻, it reacts with exceed I⁻ to form I₃⁻. And I₃⁻ and RhG combine into ion association particles. The particles exhibit three resonance scattering peaks at 320, 400 and 595nm. And there is fluorescence quenching at 540nm. Iodine concentration is proportional to the intensity of the resonance scattering intensity at 400nm in the range of 1.0–20 × 10⁻⁷molL⁻¹. And a new resonance scattering spectral (RSS) method has been described for the determination of IO₃⁻ in salt samples. The spectral results have been verified that the formation of (RhG-I₃)_n association particles and solid–liquid interfaces are the main factor that cause the fluorescence quenching and resonance scattering effects.

Keywords: Iodate; Rhodamine 6G; Association particle; Resonance scattering; Fluorescence quenching

Study of migration of active components of phosphorescent oxygen sensors for food packaging applications by Tomás C. O’Riordan; Hannes Voraberger; Joe P. Kerry; Dmitri B. Papkovsky (pp. 135-141).

A study of migration of the active components of oxygen sensors into food is presented. Six types of sensors, based on different oxygen sensitive dyes (two metalloporphyrins and one ruthenium dye), polymers (polystyrene and polysulfone) and support materials, were exposed to a number of standard ‘food simulants’ recommended by FDA/EU guidelines and then assayed for migration or sensor components and changes in oxygen calibration. Both metalloporphyrin sensor dyes leached only in olive oil and in 95% ethanol (used as a positive control), at maximum levels of 19.22μg/dm² for PtOEPK and 113.96μg/dm² for PtTFPP. The RuDPP dye showed maximum leaching in 95% ethanol (25.19μg/dm²) while also migrating in an acidic aqueous simulant. Planar supports such as polyester tended to enhance the stability of the sensor. Migration of the styrene monomer from the polystyrene encapsulation medium was concluded to be low enough to be insignificant. Migration of sensor components was shown to correlate with the changes in sensor response to oxygen. Based on these results, sensor combinations were ranked on the basis of their resistance to leaching and their general stability, safety and suitability for use on a large scale in packaged foods and related food applications was proven.

Keywords: Optical oxygen sensors; Migration studies; Phosphorescent dyes; Food simulants; Food packaging; Non-destrictive measurements

Monoclonal antibody-based enzyme-linked immunosorbent assays for the detection of the organophosphorus insecticide diazinon by Eun Kyung Lee; Yoo Jung Kim; Won Chul Park; Taeowan Chung; Yong Tae Lee (pp. 143-153).

Four haptens of the organophosphorus (OP) insecticide diazinon were synthesized to develop enzyme-linked immunosorbent assays (ELISAs) for this pesticide. One of them was conjugated to KLH to be used as the immunogen for production of monoclonal antibodies. By using the antibodies and a coating antigen, an indirect competitive ELISA was developed, which showed an IC₅₀ of 4.0ng/mL with a detection limit of 0.7ng/mL. A direct competitive ELISA using an enzyme tracer was also developed, which showed an IC₅₀ of 6.0ng/mL with a detection limit of 0.9ng/mL. The antibodies in both assays showed negligible cross-reactivity with metabolites of diazinon and other OP pesticides. Recovery of diazinon from fortified lettuce and rice samples was satisfactory except at the fortified concentration of 100ppb.

Keywords: Diazinon; Organophosphorus insecticide; Enzyme-linked immunosorbent assay; ELISA

Headspace solvent microextraction: a very rapid method for identification of volatile components of Iranian Pimpinella anisum seed by Abbas Besharati-Seidani; Ali Jabbari; Yadollah Yamini (pp. 155-161).

At the present study, a new and rapid headspace solvent microextraction (HSME), for the extraction and pre-concentration of the volatile components of plant sample into a microdrop was applied. The extraction occurred by suspending a microliter drop of the solvent from the tip of a microsyringe to the headspace of a ripen and powdered dry fruit sample (Iranian Pimpinella anisum seed) in a sealed vial for a preset extraction time, then the microdrop was retracted back into the microsyringe and injected directly into a GC injection port. The chemical composition of the HSME extracts were confirmed according to their retention indexes and mass spectra (EI, 70eV); and quantitative analysis was performed by GC–FID.Parameters such as the nature of the extracting solvent, particle size of the sample, temperatures of the microdrop and sample, volume of sample and the extraction time were studied and optimized, and the method's performance was evaluated. The optimized conditions were: sample particle size, 1mm; sample volume, 5ml (in a 15ml vial); sample temperature, 60°C; microsyringe needle temperature, 0°C; and extraction time, 10min. Finally, accordingly, the percentage of trans-anethole (the major compound of P. anisum) and the relative standard deviation for extraction and determination of trans-anethole (seven-replicated analysis) were determined to be 90% and 3.9%, respectively.

Keywords: Headspace solvent microextraction (HSME), Anise (; Pimpinella anisum; L.), Volatile components, Trans-anethole, Microdrop, Microsyringe

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Analytica Chimica Acta (v.530, #1)