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Analytica Chimica Acta (v.591, #2)

Editorial Board (pp. co1).

Contents (pp. iii-iv).

Calendar of forthcoming meetings (pp. n3).

Contents (pp. iii-iv).

Editorial Board (pp. co1).

Determination of the antidepressant paroxetine and its three main metabolites in human plasma by liquid chromatography with fluorescence detection by Roberto Mandrioli; Laura Mercolini; Anna Ferranti; Sandra Furlanetto; Giancarlo Boncompagni; Maria Augusta Raggi (pp. 141-147).

A high-performance liquid chromatographic method has been developed for the determination in human plasma of the specific serotonin reuptake inhibitor (SSRI) antidepressant paroxetine and its three main metabolites (M1, M2, M3). Fluorescence detection was used, exciting at λ=294nm and monitoring emission at λ=330nm for paroxetine ( λ_exc=280nm, λ_em=330nm for M1 and M2; λ_exc=268nm, λ_em=290nm for M3). Separation was obtained on a reversed-phase C18 column using a mobile phase composed of 66.7% aqueous phosphate at pH 2.5 and 33.3% acetonitrile. Imipramine ( λ_exc=252nm, λ_em=390nm) was used as the internal standard. A careful pre-treatment of plasma samples was developed, using solid-phase extraction with C8 cartridges (50mg, 1mL). The calibration curves were linear over a working range of 2.5–100ngmL⁻¹ for paroxetine and of 5–100ngmL⁻¹ for all metabolites. The limit of detection (LOD) was 1.2ngmL⁻¹ for PRX and 2.0ngmL⁻¹ for the metabolites. The method was applied with success to plasma samples from depressed patients undergoing treatment with paroxetine. Hence, the method seems to be suitable for the therapeutic drug monitoring of paroxetine and its main metabolites in depressed patients’ plasma.

Keywords: Paroxetine; Metabolites; High-performance liquid chromatography; Fluorescence detection; Human plasma; Solid-phase extraction

Determination of vitamin K homologues by high-performance liquid chromatography with on-line photoreactor and peroxyoxalate chemiluminescence detection by Sameh Ahmed; Naoya Kishikawa; Kenichiro Nakashima; Naotaka Kuroda (pp. 148-154).

A sensitive and highly selective high-performance liquid chromatography (HPLC) method was developed for the determination of vitamin K homologues including phylloquinone (PK), menaquinone-4 (MK-4) and menaquinone-7 (MK-7) in human plasma using post-column peroxyoxalate chemiluminescence (PO-CL) detection following on-line ultraviolet (UV) irradiation. The method was based on ultraviolet irradiation (254nm, 15W) of vitamin K to produce hydrogen peroxide and a fluorescent product at the same time, which can be determined with PO-CL detection. The separation of vitamin K by HPLC was accomplished isocratically on an ODS column within 35min. The method involves the use of 2-methyl-3-pentadecyl-1,4-naphthoquinone as an internal standard. The detection limits (signal-to-noise ratio=3) were 32, 38 and 85fmol for PK, MK-4 and MK-7, respectively. The recoveries of PK, MK-4 and MK-7 were greater than 82% and the inter- and intra-assay R.S.D. values were 1.9–5.4%. The sensitivity and selectivity of this method were sufficient for clinical and nutritional applications.

Keywords: Vitamin K; Peroxyoxalate chemiluminescence detection; Ultraviolet irradiation; High-performance liquid chromatography; Hydrogen peroxide

LC/MS quantitative study of glucose by iodine attachment by Eduard Rogatsky; Vlad Tomuta; Daniel T. Stein (pp. 155-160).

We explored the potential of iodine attachment to improve the sensitivity of glucose measurement by LC/MS. After sample preparation, glucose was separated by normal phase chromatography, followed by anionization by I⁻-attachment prior to MS by post-column addition of a methanolic solution of iodoform. Iodine is capable of forming an anionic adduct with neutral monosaccharides in negative ion mode electrospray mass spectrometry. Quasi-molecular ions [M+I]⁻ of glucose, and [6,6-²H₂]glucose (abbreviated d₂-glucose) internal standard were quantitated in selected ion monitoring (SIM) mode. Iodine attachment LC/MS analysis provided high sensitivity, superior to GC/MS. It greatly simplified sample preparation and increased throughput. The advantages of iodine attachment can be realized even on old mass spectrometers. A LOD of 50pg glucose on column was achieved. Due to iodine's predisposition to sublimate, the iodoform concentration must be minimized, which adds complexity to method development. To optimize reagent concentration we developed an efficient and flexible gradient-based delivery platform. Strategy for method development with iodoform is given.

Keywords: Glucose; Human plasma; Liquid chromatography–mass spectrometry; Isotope dilution assay; Iodine attachment

LC/MS quantitative study of glucose by iodine attachment by Eduard Rogatsky; Vlad Tomuta; Daniel T. Stein (pp. 155-160).

Keywords: Glucose; Human plasma; Liquid chromatography–mass spectrometry; Isotope dilution assay; Iodine attachment

Microwave-assisted extraction of scutellarin from Erigeron breviscapus Hand-Mazz and its determination by high-performance liquid chromatography by Min Gao; Wei Huang; Moytri RoyChowdhury; Chunzhao Liu (pp. 161-166).

An efficient microwave-assisted extraction (MAE) technique has been developed to extract scutellarin from Erigeron breviscapus for rapid determination by high-performance liquid chromatography (HPLC). The maximum yield of scutellarin reached 1.02% in 40min under the optimal MAE conditions with 80°C of extraction temperature and 1:10 (w/v) of the solid/liquid ratio. The MAE showed obvious advantages in terms of short duration and high efficiency to extract scutellarin in comparison with heat-flux extraction. The mechanism of the enhanced extraction by microwave assistance was discussed by detecting particle size and specific surface area of plant materials and observing cell destruction of plant material by light microscopy and scanning electron microscopy. The results showed that the plant materials were significantly destroyed due to the cell rupture after MAE treatment. Afterward, the method validation for HPLC-UV analysis was developed. Calibration range was 0.1–100μgmL⁻¹ for scutellarin, and correlation coefficient R was 0.9993. Limit of detection was less than 0.01μgmL⁻¹. The intra- and inter-day relative standard deviation (R.S.D.) of scutellarin detection ranged from 1.58% to 2.96% and from 3.32% to 4.19%, respectively. The recovery of the method for scutellarin ranged from 96.7% to 101.9%.

Keywords: Erigeron breviscapus; Heat-reflux extraction; High-performance liquid chromatography; Microwave-assisted extraction; Scutellarin

Determination of 1,3-dichloro-2-propanol and 3-chloro-1,2-propandiol in soy sauce by headspace derivatization solid-phase microextraction combined with gas chromatography–mass spectrometry by Maw-Rong Lee; Tzu-Chun Chiu; Jianpeng Dou (pp. 167-172).

This study proposes a method for identifying 1,3-dichloro-2-propanol and 3-chloro-1,2-propandiol in aqueous matrices by using headspace on-fiber derivatization following solid-phase microextraction combined with gas chromatography–mass spectrometry. The optimized SPME experimental procedures for extracting 1,3-dichloro-2-propanol and 3-chloro-1,2-propandiol in aqueous solutions involved a 85μm polyacrylate-coated fiber at pH 6, a sodium chloride concentration of 0.36gmL⁻¹, extraction at 50°C for 15min and desorption of analytes at 260°C for 3min. Headspace derivatization was conducted in a laboratory-made design with N-methyl- N-(trimethylsilyl)-trifluoroacetamide vapor following solid-phase microextraction by using 3μL N-methyl- N-(trimethylsilyl)-trifluoroacetamide at an oil bath temperature of 230°C for 40s. This method had good repeatability (R.S.D.s≤19%, n=8) and good linearity ( r²≥0.9972) for ultrapure water and soy sauce samples that were spiked with two analytes. Detection limits were obtained at the ngmL⁻¹. The result demonstrated that headspace on-fiber derivatization following solid-phase microextraction was a simple, fast and accurate technique for identifying trace 1,3-dichloro-2-propanol and 3-chloro-1,2-propandiol in soy sauce.

Keywords: 1,3-Dichloro-2-propanol; 3-Chloro-1,2-propandiol; Solid-phase microextraction; Gas chromatography–mass spectrometry; Soy sauce

Hapten design and indirect competitive immunoassay for parathion determination: Correlation with molecular modeling and principal component analysis by Yi Hua Liu; Mao Jun Jin; Wen Jun Gui; Jing Li Cheng; Yi Rong Guo; Guo Nian Zhu (pp. 173-182).

A novel procedure for parathion hapten design is described. The optimal antigen for parathion was selected after molecular modeling studies of six types of potentially immunizing haptens with the aim to identify the best mimicking target analyte. Heterologous competitive indirect enzyme-linked immunosorbent assay (ELISA) was developed after screening a battery of competitors as coating antigens. The relationship between the heterology degree of the competitor and the resulting immunoassay detectability was investigated according to the electronic similarities of the competitor haptens and the target analyte. Molecular modeling and principal component analysis were performed to understand the electronic distribution and steric parameters of the haptens at their minimum energetic levels. The results suggested that the competitors should have a high heterology to produce assays with good detectability values. An indirect competitive ELISA was finally selected for further investigation. The immunoassay had an IC₅₀ value of 4.79ngmL⁻¹ and a limit of detection of 0.31ngmL⁻¹. There was little or no cross-reactivity to similar compounds tested except for the insecticide parathion-methyl, which showed a cross-reactivity of 7.8%.

Keywords: Hapten design; Enzyme-linked immunosorbent assay; Parathion; Molecular modeling; Principal component analysis

Enzyme-linked immunosorbent assays for the insecticide fenitrothion by Yoo Jung Kim; Young Ah Kim; Yong Tae Lee; Hye-Sung Lee (pp. 183-190).

This study aimed at developing competitive enzyme-linked immunosorbent assays (ELISAs) for the organophosphorus (OP) insecticide fenitrothion using a monoclonal antibody. The hapten used to obtain the antibody had an ideal structural feature that allowed minimal functional group sacrifice. By using the antibody and a coating antigen, a competitive indirect ELISA was developed, which showed an IC₅₀ of 14ngmL⁻¹ with a detection limit of 3.0ngmL⁻¹. A competitive direct ELISA using an enzyme tracer was also developed, which showed an IC₅₀ of 17ngmL⁻¹ with a detection limit of 1.6ngmL⁻¹. The antibodies in both assays showed negligible cross-reactivity with the metabolites of fenitrothion and other OP pesticides except with the insecticides parathion-methyl and parathion-ethyl. Recoveries of fenitrothion from fortified rice and lettuce samples were determined and the bias in the recovery values was rationalized by using the standard curves obtained in the matrix extract.

Keywords: Fenitrothion; Insecticide; Monoclonal antibody; Immunoassay; Enzyme-linked immunosorbent assay

Enzyme-linked immunosorbent assays for the insecticide fenitrothion by Yoo Jung Kim; Young Ah Kim; Yong Tae Lee; Hye-Sung Lee (pp. 183-190).

Keywords: Fenitrothion; Insecticide; Monoclonal antibody; Immunoassay; Enzyme-linked immunosorbent assay

Surface plasmon resonance-based trace detection of small molecules by competitive and signal enhancement immunoreaction by Hidenobu Aizawa; Mitsuhiro Tozuka; Shigeru Kurosawa; Koichi Kobayashi; Subrayal M. Reddy; Masahiro Higuchi (pp. 191-194).

A surface plasmon resonance (SPR)-immunosensor for detection of the low molecular weight compound 2,4-dinitorophenol (DNP) at ultra-low concentration has been developed. The sensor strategy is based on a competitive immunoreaction between DNP and a DNP–protein conjugate, namely DNP–bovine serum albumin conjugate (DNP–BSA). Anti-DNP monoclonal antibody was immobilized on a gold thin-film coated SPR-sensor chip by means of a chemical coupling process. DNP–BSA, on contact with the anti-DNP antibody immobilized SPR-immunosensor chip causes an increase in the resonance angle of the sensor chip. The optimum concentration of immobilized antibody on the SPR-sensor chip is 100μgmL⁻¹. The SPR-immunosensor response for free DNP determination using the competitive immunoreaction had a response time of ca. 15min. Using this method, DNP could be determined in the concentration range 1ppt to 1ppb. The SPR signal for ppt levels of DNP was enhanced by a factor of three by subsequently treating immuno-bound DNP–BSA with a secondary anti-DNP antibody.

Keywords: Surface plasmon resonance (SPR); SPR-immunosensor; 2,4-Dinitrophenol (DNP); DNP–protein conjugate; Anti-DNP–protein monoclonal antibody; Signal enhancement immunoreaction

An amperometric glucose biosensor constructed by immobilizing glucose oxidase on titanium-containing mesoporous composite material of no. 41 modified screen-printed electrodes by Zhihui Dai; Min Fang; Jianchun Bao; Huaisheng Wang; Tianhong Lu (pp. 195-199).

We have constructed a glucose biosensor by immobilizing glucose oxidase (GOD) on titanium-containing MCM-41 (Ti-MCM-41) modified screen-printed electrodes. The strategy of the sensing method is to monitor the extent of the decrease of the reduction current of O₂ upon adding glucose at a selected potential. The detection can be done at the applied potential of −0.50V and can efficiently exclude the interference from commonly coexisted substances. The constructed sensor has a high sensitivity to glucose (5.4mAM⁻¹cm⁻²) and a linear response range of 0.10–10.0mM. The detection limit is 0.04mM at a signal-to-noise ratio of 3. The sensor also shows high stability and remains its catalytic activity up to 60°C. The biocompatibility of Ti-MCM-41 means that this immobilization matrix not only can be used for immobilizing GOD but also can be extended to other enzymes and bioactive molecules, thus providing a promising platform for the development of biosensors.

Keywords: Titanium-containing mesoporous composite material of no. 41; Glucose oxidase; Glucose; Biosensor

Biosensing hydrogen peroxide utilizing carbon paste electrodes containing peroxidases naturally immobilized on coconut ( Cocus nucifera L.) fibers by J.V.B. Kozan; R.P. Silva; S.H.P. Serrano; A.W.O. Lima; L. Angnes (pp. 200-207).

A novel unmediated hydrogen peroxide biosensor based on the incorporation of fibrous tissue of coconut fruit in carbon paste matrix is presented. Cyclic voltammetry and amperometry were utilized to characterize the main electrochemical parameters and the performance of this new biosensor under different preparation and operation conditions. The resulting H₂O₂-sensitive biosensors respond rapidly (7s to attain 90% of the signal), was operated at −0.15V, presented linear response between 2.0×10⁻⁴ and 3.4×10⁻³molL⁻¹, the detection limit was estimated as 4.0×10⁻⁵molL⁻¹. Its operation potential was situated between −0.2 and 0.1V and the best pH was determined as 5.2. Electrodes containing 5% (w/w) of coconut fiber presented the best signal and their lifetime was extended to 3 months. The apparent Michaelis–Menten constantKMapp and V_max were estimated to be 8.90mmolL⁻¹ and 6.92mmolL⁻¹μA⁻¹, respectively. The results obtained for determination of hydrogen peroxide in four pharmaceutical products (antiseptic solution, contact lenses cleaning solution, hair coloring cream and antiseptic dental rinse solution) were in agreement with those obtained by the spectrophotometric method. An additional advantage of these biosensors is the capacity to measure hydrogen peroxide even in samples with relatively low pH. To demonstrate the enzymatic activity of the coconut tissue, a very simple way was created during this work. Coconut fibers were immersed in H₂O₂ solution between two glass slides. Sequential images were taken to show the rapid generation of O₂, attesting the high activity of the enzymes.

Keywords: Plant tissue-based biosensors; Coconut; Voltammetry; Peroxidase; Hydrogen peroxide; Carbon paste electrode

Development of a disposable mercury ion-selective optode based on trityl-picolinamide as ionophore by Bambang Kuswandi; Nuriman; Henk H. Dam; David N. Reinhoudt; Willem Verboom (pp. 208-213).

A disposable ion-selective optode for mercury based on trityl-picolinamide (T-Pico) as neutral ionophore was developed. The sensing layer consist of plasticised PVC incorporating T-Pico as a selective ionophore for Hg²⁺, ETH 5418 as a chromoionophore, and potassium tetrakis[3,5-bis(trifluoromethyl)phenyl] borate as lipophilic salt. The measurement principle is based on an ion-exchange mechanism. When the optode membrane is introduced into a water sample for 5min, there is a colour change from red to blue, depending on the mercury concentration (pH 4.7), making it possible to use the absorbance at 665nm as the analytical signal. The optode membrane response to Hg²⁺ was not fully reversible; however, it reveals a very good selectivity to many cations including alkali, alkaline earth, transition, and heavy metal ions. The detection limit for Hg²⁺ is 5.0×10⁻⁷M at pH 4.7. The response characteristics of the sensor including dynamic range, reproducibility, response time, and lifetime are discussed in detail. This sensor was used for the determination of mercury in environmental water samples with satisfactory recovery.

Keywords: Ion-selective optode; Poly(vinyl chloride) membrane; Trityl-picolinamide; Hg; ²⁺

Development of a disposable mercury ion-selective optode based on trityl-picolinamide as ionophore by Bambang Kuswandi; Nuriman; Henk H. Dam; David N. Reinhoudt; Willem Verboom (pp. 208-213).

Keywords: Ion-selective optode; Poly(vinyl chloride) membrane; Trityl-picolinamide; Hg; ²⁺

Magnetron sputtering of silver nanowires using anodic aluminum oxide template: A new active substrate of surface enhanced Raman scattering and an investigation of its enhanced mechanism by Lisheng Zhang; Pengxiang Zhang; Yan Fang (pp. 214-218).

A high quality anodic aluminum oxide (AAO) template with ordered apertures about 50–80nm was fabricated by anodizing aluminum in electrolytes through a two-step method, and silver nanowires with diameters from 40nm to 70nm were prepared on this AAO template by magnetron sputtering. On the glass covered with silver nanowires, high quality surface enhanced Raman scattering (SERS) spectra of sudan II (C₁₈H₁₆N₂O) with enhancement factors of 10⁵ were obtained. And comparison of SERS spectra on silver nanowires with the SERS spectra of silver colloids indicates that main enhanced mode is lightning rod effect of nanorods on the Sudan II/silver nanowires system.

Keywords: Nanowire; Magnetron sputtering; Surface enhanced Raman scattering; Anodic aluminum oxide

Combined wavelet transform–artificial neural network use in tablet active content determination by near-infrared spectroscopy by Pascal Chalus; Serge Walter; Michel Ulmschneider (pp. 219-224).

The pharmaceutical industry faces increasing regulatory pressure to optimize quality control. Content uniformity is a basic release test for solid dosage forms. To accelerate test throughput and comply with the Food and Drug Administration's process analytical technology initiative, attention is increasingly turning to nondestructive spectroscopic techniques, notably near-infrared (NIR) spectroscopy (NIRS). However, validation of NIRS using requisite linearity and standard error of prediction (SEP) criteria remains a challenge. This study applied wavelet transformation of the NIR spectra of a commercial tablet to build a model using conventional partial least squares (PLS) regression and an artificial neural network (ANN). Wavelet coefficients in the PLS and ANN models reduced SEP by up to 60% compared to PLS models using mathematical spectra pretreatment. ANN modeling yielded high-linearity calibration and a correlation coefficient exceeding 0.996.

Keywords: Near-infrared spectroscopy; Pharmaceutical; Content uniformity; Wavelet; Artificial neural networks; Tablets

Combined wavelet transform–artificial neural network use in tablet active content determination by near-infrared spectroscopy by Pascal Chalus; Serge Walter; Michel Ulmschneider (pp. 219-224).

Keywords: Near-infrared spectroscopy; Pharmaceutical; Content uniformity; Wavelet; Artificial neural networks; Tablets

Improved microwave-assisted wet digestion procedures for accurate Se determination in fish and shellfish by flow injection-hydride generation-atomic absorption spectrometry by I. Lavilla; J.M. González-Costas; C. Bendicho (pp. 225-230).

Accurate determination of Se in biological samples, especially fish and shellfish, by hydride generation techniques has generally proven troublesome owing to the presence of organoselenium that cannot readily converted into inorganic selenium under usual oxidising conditions. Further improvements in the oxidation procedures are needed so as to obtain accurate concentration values when this type of samples is analyzed.Microwave-assisted wet digestion (MAWD) procedures of seafood based on HNO₃ or the mixture HNO₃/H₂O₂ and further thermal reduction of the Se(VI) formed to Se(IV) were evaluated. These procedures were as follows: (I) without H₂O₂ and without heating to dryness; (II) without H₂O₂ and with heating to dryness; (III) with H₂O₂ and without heating to dryness; (IV) with H₂O₂ and with heating to dryness. In general, low recoveries of selenium are obtained for several marine species (e.g., crustaceans and cephalopods), which may be ascribed to the presence of Se forms mainly associated with nonpolar proteins and lipids. Post-digestion UV irradiation proved very efficient since not only complete organoselenium decomposition was achieved but also the final step required for prereduction of Se(VI) into Se(IV) (i.e. heating at 90°C for 30min in 6M HCl) could be avoided. With the MAWD/UV procedure, the use of strong oxidising agents (persuphate, etc.) or acids (e.g. perchloric acid) which are typically applied prior to Se determination by hydride generation techniques is overcome, and as a result, sample pre-treatment is significantly simplified.The method was successfully validated against CRM DOLT-2 (dogfish liver), CRM DORM-2 (dogfish muscle) and CRM TORT-2 (lobster hepatopancreas). Automated ultrasonic slurry sampling with electrothermal atomic absorption spectrometry was also applied for comparison.Total Se contents in ten seafood samples were established. Se levels ranged from 0.7 to 2.9μgg⁻¹.

Keywords: Selenium; Fish and shellfish; Microwave-assisted wet digestion; Ultraviolet irradiation; Hydride generation; Atomic absorption spectrometry

Direct determination of cadmium in Orujo spirit samples by electrothermal atomic absorption spectrometry: Comparative study of different chemical modifiers by M. Vilar Fariñas; J. Barciela García; S. García Martín; R. Peña Crecente; C. Herrero Latorre (pp. 231-238).

In this work, several analytical methods are proposed for cadmium determination in Orujo spirit samples using electrothermal atomic absorption spectrometry (ETAAS). Permanent chemical modifiers thermally coated on the platforms inserted in pyrolytic graphite tubes (such as W, Ir, Ru, W–Ir and W–Ru) were comparatively studied in relation to common chemical modifier mixtures [Pd–Mg(NO₃)₂ and (NH₄)H₂PO₄–Mg(NO₃)₂] for cadmium stabilization. Different ETAAS Cd determination methods based on the indicated modifiers have been developed. In each case, pyrolysis and atomization temperatures, atomization shapes, characteristic masses and detection limits as well as other analytical characteristics have been determined. All the assayed modifiers (permanent and conventional) were capable of achieving the appropriate stabilization of the analyte, with the exception of Ru and W–Ru. Moreover, for all developed methods, recoveries (99–102%) and precision (R.S.D. lower than 10%) were acceptable. Taking into account the analytical performance (best detection limit LOD=0.01μgL⁻¹), the ETAAS method based on the use of W as a permanent modifier was selected for further direct Cd determinations in Orujo samples from Galicia (NW Spain). The chosen method was applied in the determination of the Cd content in 38 representative Galician samples. The cadmium concentrations ranged −1.

Keywords: Cadmium determination; Electrothermal atomic absorption spectrometry; Matrix modifier; Orujo; Alcoholic distillate spirits

Improvement of the decision efficiency of the accuracy profile by means of a desirability function for analytical methods validation by E. Rozet; V. Wascotte; N. Lecouturier; V. Préat; W. Dewé; B. Boulanger; Ph. Hubert (pp. 239-247).

Validation of analytical methods is a widely used and regulated step for each analytical method. However, the classical approaches to demonstrate the ability to quantify of a method do not necessarily fulfill this objective. For this reason an innovative methodology was recently introduced by using the tolerance interval and accuracy profile, which guarantee that a pre-defined proportion of future measurements obtained with the method will be included within the acceptance limits. Accuracy profile is an effective decision tool to assess the validity of analytical methods. The methodology to build such a profile is detailed here. However, as for any visual tool it has a part of subjectivity. It was then necessary to make the decision process objective in order to quantify the degree of adequacy of an accuracy profile and to allow a thorough comparison between such profiles. To achieve this, we developed a global desirability index based on the three most important validation criteria: the trueness, the precision and the range. The global index allows the classification of the different accuracy profiles obtained according to their respective response functions. A diacetyl-monoxime colorimetric assay for the determination of urea in transdermal iontophoretic extracts was used to illustrate these improvements.

Keywords: Colorimetric method; Iontophoretic extracts; Validation; Accuracy profile; Tolerance interval; Desirability index

Flow injection determination of anisidine value in palm oil samples using a triiodide potentiometric detector by Bahruddin Saad; Wan Tatt Wai; Boey Peng Lim; Muhammad Idiris Saleh (pp. 248-254).

A flow injection analysis (FIA) procedure for the determination of anisidine value (AV) in palm olein using a triiodide detector is described. Undiluted oil sample and chloramine-T reagent were added to a reaction chamber, and reaction was accelerated by applying a short vortex action (typically for 30s). After allowing the emulsified oil phase to be separated from the aqueous phase (bottom layer), an aliquot of the aqueous phase (containing unreacted chloramine-T) was aspirated into a carrier stream that contained I⁻ where the chloramine-T oxidized the I⁻ to form I₃⁻ which was finally detected by a flow-through triiodide potentiometric detector. Variables that affect the FIA signals such as size of the reaction chamber, oil and reagent flow rates, chloramine-T concentration, vortex time, time for phase separation, carrier stream pH and injected volume were studied. The optimized FIA procedure is linear over 1.0–23.0AV. The method exhibits good repeatabililty (R.S.D. of ±3.16% ( n=4) for the determination of 5.0AV) and a sampling rate of 40 samples per hour was achieved. Good correlation ( r²=0.996 ( n=4)) between the proposed method and the manual American Oil Chemists’ Society procedure was found when applied to the determination of twenty different types of palm olein samples.

Keywords: Anisidine value; Oxidative stability; Palm olein; Flow injection analysis; Triiodide electrode; Chloramine-T

Flow injection determination of anisidine value in palm oil samples using a triiodide potentiometric detector by Bahruddin Saad; Wan Tatt Wai; Boey Peng Lim; Muhammad Idiris Saleh (pp. 248-254).

Keywords: Anisidine value; Oxidative stability; Palm olein; Flow injection analysis; Triiodide electrode; Chloramine-T

Quantitative structure activity relationship model for predicting the depletion percentage of skin allergic chemical substances of glutathione by Hongzong Si; Tao Wang; Kejun Zhang; Yun-Bo Duan; Shuping Yuan; Aiping Fu; Zhide Hu (pp. 255-264).

A quantitative model was developed to predict the depletion percentage of glutathione (DPG) compounds by gene expression programming (GEP). Each kind of compound was represented by several calculated structural descriptors involving constitutional, topological, geometrical, electrostatic and quantum-chemical features of compounds. The GEP method produced a nonlinear and five-descriptor quantitative model with a mean error and a correlation coefficient of 10.52 and 0.94 for the training set, 22.80 and 0.85 for the test set, respectively. It is shown that the GEP predicted results are in good agreement with experimental ones, better than those of the heuristic method.

Keywords: Allergic contact dermatitis; Gene expression programming; Quantitative structure activity relationship; Heuristic method; Depletion percent of glutathione

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Analytica Chimica Acta (v.591, #2)