Check out our New Publishers' Select for Free Articles

Analytica Chimica Acta (v.689, #1)

Editorial Board (pp. iii).

Interpretation of analysis of variance models using principal component analysis to assess the effect of a maternal anticancer treatment on the mineralization of rat bones by I. Stanimirova; K. Michalik; Z. Drzazga; H. Trzeciak; P.D. Wentzell; B. Walczak (pp. 1-7).

The goal of the present study is to assess the effects of anticancer treatment with cyclophosphamide and cytarabine during pregnancy on the mineralization of mandible bones in 7-, 14- and 28-day-old rats. Each bone sample was described by its X-ray fluorescence spectrum characterizing the mineral composition. The data collected are multivariate in nature and their structure is difficult to visualize and interpret directly. Therefore, methods like analysis of variance–principal component analysis (ANOVA–PCA) and ANOVA–simultaneous component analysis (ASCA), which are suitable for the analysis of highly correlated spectral data and are able to incorporate information about the underlined experimental design, are greatly valued. In this study, the ASCA methodology adapted for unbalanced data was used to investigate the impact of the anticancer drug treatment during pregnancy on the mineralization of the mandible bones of newborn rats and to examine any changes in the mineralization of the bones over time.The results showed that treatment with cyclophosphamide and cytarabine during pregnancy induces a decrease in the K and Zn levels in the mandible bones of newborns. This suppresses the development of mandible bones in rats in the early stages (up to 14 days) of formation. An interesting observation was that the levels of essential minerals like K, Mg, Na and Ca vary considerably in the different regions of the mandible bones.

Keywords: Chemometrics; Cytarabine; Cyclophosphamide; XRF; Unbalanced ANOVA; ASCA; ANOVA–PCA

A review of the determination of organic compounds in Bayer process liquors by Greg Power; Joanne S.C. Loh; Johannes E. Wajon; Francesco Busetti; Cynthia Joll (pp. 8-21).

Bayer process liquors present a difficult and complex matrix to the analytical chemist, and the history of the application of modern analytical techniques to this problem is a case study in innovation. All Bayer process liquors contain organic compounds, in amounts varying from traces to several grams per litre. The total organic carbon content of Bayer liquors may be less than 5g/L up to as much as 40g/L. The presence of these organic impurities is of concern to Bayer technologists because they can have significant impacts on the economics of the process and the quality of the product. This review examines the history and current state-of-the-art of the analysis of organics in Bayer process liquors, and provides guidance on the applicable techniques matched to a comprehensive list of the compounds most likely to be present.

Keywords: Organics analysis; Bayer process; Review

A modification of the successive projections algorithm for spectral variable selection in the presence of unknown interferents by Sófacles Figueredo Carreiro Soares; Roberto Kawakami Harrop Galvão; Mário César Ugulino Araújo; Edvan Cirino da Silva; Claudete Fernandes Pereira; Stéfani Iury Evangelista de Andrade; Flaviano Carvalho Leite (pp. 22-28).

This work proposes a modification to the successive projections algorithm (SPA) aimed at selecting spectral variables for multiple linear regression (MLR) in the presence of unknown interferents not included in the calibration data set. The modified algorithm favours the selection of variables in which the effect of the interferent is less pronounced. The proposed procedure can be regarded as an adaptive modelling technique, because the spectral features of the samples to be analyzed are considered in the variable selection process. The advantages of this new approach are demonstrated in two analytical problems, namely (1) ultraviolet–visible spectrometric determination of tartrazine, allure red and sunset yellow in aqueous solutions under the interference of erythrosine, and (2) near-infrared spectrometric determination of ethanol in gasoline under the interference of toluene. In these case studies, the performance of conventional MLR-SPA models is substantially degraded by the presence of the interferent. This problem is circumvented by applying the proposed Adaptive MLR-SPA approach, which results in prediction errors smaller than those obtained by three other multivariate calibration techniques, namely stepwise regression, full-spectrum partial-least-squares (PLS) and PLS with variables selected by a genetic algorithm. An inspection of the variable selection results reveals that the Adaptive approach successfully avoids spectral regions in which the interference is more intense.

Keywords: Variable selection; Successive projections algorithm; Interferents; Ultraviolet–visible and near-infrared spectrometry; Colorants; Gasoline

Redox cycling amplified electrochemical detection of DNA hybridization: Application to pathogen E. coli bacterial RNA by Anne Walter; Jie Wu; Gerd-Uwe Flechsig; David A. Haake; Joseph Wang (pp. 29-33).

An electrochemical genosensor in which signal amplification is achieved using p-aminophenol ( p-AP) redox cycling by nicotinamide adenine dinucleotide (NADH) is presented. An immobilized thiolated capture probe is combined with a sandwich-type hybridization assay, using biotin as a tracer in the detection probe, and streptavidin-alkaline phosphatase as reporter enzyme. The phosphatase liberates the electrochemical mediator p-AP from its electrically inactive phosphate derivative. This generated p-AP is electrooxidized at an Au electrode modified self-assembled monolayer to p-quinone imine ( p-QI). In the presence of NADH, p-QI is reduced back to p-AP, which can be re-oxidized on the electrode and produce amplified signal. A detection limit of 1pM DNA target is offered by this simple one-electrode, one-enzyme format redox cycling strategy. The redox cycling design is applied successfully to the monitoring of the 16S rRNA of E. coli pathogenic bacteria, and provides a detection limit of 250CFUμL⁻¹.

Keywords: Electrochemistry; Genosensor; Amplification; Redox cycling; Escherichia coli

Investigation of iodine liberation process in redox titration of potassium iodate with sodium thiosulfate by Toshiaki Asakai; Akiharu Hioki (pp. 34-38).

Potassium iodate is often used as a reference material to standardize a sodium thiosulfate solution which is a familiar titrant for redox titrations. In the standardization, iodine (triiodide) liberated by potassium iodate in an acidic potassium iodide solution is titrated with a sodium thiosulfate solution. The iodine liberation process is significantly affected by the amount of acid, that of potassium iodide added, the waiting time for the liberation, and light; therefore, the process plays a key role for the accuracy of the titration results. Constant-voltage biamperometry with a modified dual platinum-chip electrode was utilized to monitor the amount of liberated iodine under several liberation conditions. Coulometric titration was utilized to determine the concentration of a sodium thiosulfate solution on an absolute basis. Potassium iodate was assayed by gravimetric titration with the sodium thiosulfate solution under several iodine liberation conditions. The liberation process was discussed from the changes in the apparent assay of potassium iodate. The information of the appropriate titration procedure obtained in the present study is useful for any analysts utilizing potassium iodate to standardize a thiosulfate solution.

Keywords: Coulometric titration; Oxidation–reduction titration; Iodine liberation; Certified reference material; Sodium thiosulfate; Potassium iodate

The application of β-cyclodextrin derivative functionalized aligned carbon nanotubes for electrochemically DNA sensing via host–guest recognition by Lizhu Yang; Ying Xu; Xiuhua Wang; Jing Zhu; Renyi Zhang; Pingang He; Yuzhi Fang (pp. 39-46).

We functionalized aligned carbon nanotubes (ACNTs) electrode with a new kind of β-cyclodextrin (β-CD) derivative through diazotization reaction. The resulting β-CD/ACNTs electrode was used to detect DNA hybridization in homogeneous solution based on host–guest recognition technology. In the sensing protocol, one special DNA probe was designed with a stem-loop structure and both ends modified, which we called dually labeled DNA probe (DLP). One end of the DLP was labeled with dabcyl as guest molecule for β-CD/ACNTs electrode capture, and the other end was labeled with a CdS nanoparticle as an electrochemical tag to indicate the occurrence of DNA hybridization. In the absence of the target DNA sequence, the DLP maintains its hairpin structure in solution phase and would not be captured and detected by the β-CD/ACNTs electrode. In the presence of the complementary target sequence, the conformational structure of the DLP was altered and a double-stranded DNA (dsDNA) molecule was formed by the hybridization of DLP and complementary DNA sequence. Consequently, the dsDNA was captured by the β-CD/ACNTs electrode owing to guest–host recognition between β-CD and dabcyl. The electrochemical signal from the CdS nanoparticle–dsDNA/β-CD/ACNTs was then measured. Under optimized detection conditions, the proposed method showed high sensitivity and selectivity with a detection limit of 5.0×10⁻¹³M for complementary DNA sequence.

Keywords: β-Cyclodextrin derivative; Aligned carbon nanotubes; Host–guest recognition; Diazotization reaction; DNA biosensor

In situ synthesis of thulium(III) hexacyanoferrate(II) nanoparticles and its application for glucose detection by Zuchao Meng; Jianbin Zheng; Qinglin Sheng; Xiaohui Zheng (pp. 47-51).

Thulium hexacyanoferrate (TmHCF) nanoparticles (NPs) were in situ synthesized within the chitosan film on the electrode surface by a biocatalyzed reaction. The properties of the obtained nanoparticles are characterized with scanning electron microscope (SEM) and energy-dispersive X-ray (EDX). The optimized conditions for the formation of TmHCF NPs were 16mM Fe(CN)₆³⁻ and 1.5mM Tm³⁺ with an accumulation time of 20min. Based on process of in situ synthesis of TmHCF NPs, a novel biosensor for glucose was designed, and there is a linear relationship between the current response of TmHCF NPs and glucose concentration. The linear range for glucose detection was 0.02–0.4mM ( r=0.9975, n=5) and 0.4–13.6mM ( r=0.9935, n=10) and the detection limit was 6μM at a signal-to-noise ratio of 3.

Keywords: Biosensor; In situ synthesis; Thulium hexacyanoferrate; Glucose oxidase; Glucose

Application of an Hg²⁺ selective imprinted polymer as a new modifying agent for the preparation of a novel highly selective and sensitive electrochemical sensor for the determination of ultratrace mercury ions by Taher Alizadeh; Mohamad Reza Ganjali; Mashaalah Zare (pp. 52-59).

A simple and very selective electrode, based on a mercury ion imprinted polymer (IIP), and its application for the determination of Hg²⁺ ions in the real samples is introduced. Mercury ion selective cavities were created in the vinyl pyridine based cross-linked polymer. In order to fabricate the sensor carbon particles and polymer powder were mixed with melted n-eicosane. An explicit difference was observed between the responses of the electrodes modified with IIP and non imprinted polymer (NIP), indicating proper performance of the recognition sites of the IIP. Various factors, known to affect the response behavior of selective electrode, were investigated and optimized. The interference of different ionic species with the response of the electrode was also studied. The results revealed that, compared to previously developed mercury selective sensors, the proposed sensor was more selective, regarding the common potential interferer. This sensor showed a linear response range of 2.5×10⁻⁹–5.0×10⁻⁷M and lower detection limit of 5.2×10⁻¹⁰M ( S/ N). The sensor was successfully applied to the determination of mercury in real samples.

Keywords: Hg; ²⁺; imprinted polymer; Electrochemical sensor; Carbon paste electrode; Ultratrace level

Determination of mercury in ambient water samples by anodic stripping voltammetry on screen-printed gold electrodes by E. Bernalte; C. Marín Sánchez; E. Pinilla Gil (pp. 60-64).

The applicability of commercial screen-printed gold electrodes (SPGEs) for the determination of Hg(II) in ambient water samples by square wave anodic stripping voltammetry has been demonstrated. Electrode conditioning procedures, chemical and instrumental variables have been optimized to develop a reliable method capable of measuring dissolved mercury in the low ngmL⁻¹ range (detection limit 1.1ngmL⁻¹), useful for pollution monitoring or screening purposes. The proposed method was tested with the NIST 1641d Mercury in Water Standard Reference Material (recoveries 90.0–110%) and the NCS ZC 76303 Mercury in Water Certified Reference Material (recoveries 82.5–90.6%). Waste water samples from industrial origin and fortified rain water samples were assayed for mercury by the proposed method and by a reference ICP-MS method, with good agreement. Screen printing technology thus opens a useful way for the construction of reliable electrochemical sensors for decentralized or even field Hg(II) testing.

Keywords: Hg(II); SWASV (Square wave anodic stripping voltammetry); Screen-printed gold electrodes; Rain water; Waste water

Determination of benzothiazole in untreated wastewater using polar-phase stir bar sorptive extraction and gas chromatography–mass spectrometry by Elke Fries (pp. 65-68).

Stir bar sorptive extraction (SBSE) was applied to extract benzothiazole (BT) from untreated wastewater using a novel polyacrylate (PA)-coated stir bar (PA Twister^®). After extraction, BT was desorbed in a thermal desorption system (TDS) and analysed by GC–MS (gas chromatography–mass spectrometry). The sample contained 30% (w/w) NaCl, the sample temperature was 30°C and the extraction time was 240min. Since no filtering or clean-up steps or solvents were necessary SBSE clearly performs better than all previously used extractions techniques for analysing BT in untreated wastewater in terms of easy use, sample throughput and analytical costs. In addition, matrix effects were small. The calibration curve resulting from the standard addition method was linear with a value of the stability index ( R²) of 0.999 ( n=3). A good inter-day repeatability of the method was observed with a relative standard deviation (RSD) of 9.8% ( n=6). A low limit of detection (LOD) of 0.256μgL⁻¹ was achieved using only a small sample volume of 18mL. Small sample volumes significantly reduce sample transport costs. The concentration of BT in untreated wastewater was determined to be 1.04μgL⁻¹.

Keywords: Wastewater influent; Wastewater treatment plant; Solvent-free extraction technique; Tyres; Vulcanisation accelerator; 2-Mercaptobenzothiazole

Derivatization of (5 R)-hydroxytriptolide from benzylamine to enhance mass spectrometric detection: Application to a Phase I pharmacokinetic study in humans by Jia Liu; Xiaoyan Chen; Yifan Zhang; Hong Miao; Ke Liu; Liang Li; Dafang Zhong (pp. 69-76).

(5 R)-Hydroxytriptolide, a semisynthetic structural analog of triptolide, exhibits anti-inflammatory and immunosuppressive effect both in vitro and in vivo. The compound is currently undergoing Phase I clinical trials. This work describes the quantification of (5 R)-hydroxytriptolide in human plasma based on chemical derivatization from benzylamine. Analysis through liquid chromatography–tandem mass spectrometry (LC–MS/MS) is performed for characterization. The primary reaction product between (5 R)-hydroxytriptolide and benzylamine was identified as a 12,13-epoxide ring adduct. For quantification in plasma, (5 R)-hydroxytriptolide and the internal standard (triptolide) were first extracted from diethyl ether–dichloromethane (3:2, v/v) and then converted to their benzylamine derivates at 80°C for 1h. The analytes are separated on a Gemini 5μm 100Å column, using a gradient elution program with a solvent consisting of 0.77mM ammonium hydroxide (pH 10.0) and acetonitrile. An API 4000 tandem mass spectrometer operated in positive ion mode and equipped with an electrospray ionization source is used as detector. This method allows for a lower limit of quantification of 0.030ngmL⁻¹. The validation results show accuracy (%RE<11.7) and precision (%RSD<8.6) at a broad linear dynamic range (0.030–100ngmL⁻¹). The simple and quantitative derivatization coupled with tandem mass spectrometric analysis yields a sensitive and robust method for the quantification of (5 R)-hydroxytriptolide in Phase I pharmacokinetic studies.

Keywords: (5; R; )-Hydroxytriptolide; Triptolide; Benzylamine; Derivatization; Liquid chromatography–tandem mass spectrometry; Human plasma

Ultra-high performance liquid chromatography tandem mass spectrometry for comprehensive analysis of urinary acylcarnitines by Azeret Zuniga; Liang Li (pp. 77-84).

We report an enabling mass spectrometric method for the analysis of lipid metabolites in order to define better the lipid metabolome in terms of chemical diversity and generate fragment ion spectra of these metabolites as a potential resource for unknown metabolite identification. This work focuses on the analysis of one important class of lipid metabolites, the acylcarnitines. Current analytical methods have only detected and identified a limited number of these metabolites. The method described herein provides the most comprehensive acylcarnitine profile in urine of healthy individuals up to date. It involves an optimized solid phase extraction technique for selective analyte extraction using cartridges containing both lipophilic and cation-exchange properties. The captured analytes are then subjected to ultra-high performance liquid chromatography (UPLC) separation, followed by tandem mass spectrometry (MS/MS) analysis using information-dependent acquisitions and selected reaction monitoring (SRM). The urine of six healthy individuals was analyzed using this method. A total of 355 acylcarnitines were detected; only 43 of them have been previously reported in the urine of healthy individuals. Detection of this large number of acylcarnitines illustrates the great diversity of the lipid metabolome as well as the usefulness of the method for profiling acylcarnitines. Furthermore, the MS/MS spectra of the 355 acylcarnitines will be uploaded to a public human metabolome database as a mass spectrometric resource for unknown metabolite identification.

Keywords: Metabolome analysis; Metabolite identification; Acylcarnitines; Liquid chromatography mass spectrometry; Tandem mass spectrometry; Ultra-high performance liquid chromatography; Metabolomics

Plasma esterified and non-esterified fatty acids metabolic profiling using gas chromatography–mass spectrometry and its application in the study of diabetic mellitus and diabetic nephropathy by Li-Da Han; Jian-Fei Xia; Qiong-Lin Liang; Yong Wang; Yi-Ming Wang; Ping Hu; Ping Li; Guo-An Luo (pp. 85-91).

Using gas chromatography–mass spectrometry (GC–MS), a new metabolic profiling method was established to assess the levels of non-esterified fatty acids (NEFAs) and esterified fatty acids (EFAs) in plasma. The extraction method was simple and robust without removing protein process. With this method 25 fatty acids (FAs), both EFAs and NEFAs, can be recognized simultaneously with only 10μL plasma. 15 of the 25 can be precisely quantified. The method was validated and then applied into clinical metabonomics research. Five clinical groups including 150 cases were involved. The relationship between FA levels and diabetic mellitus (DM) as well as diabetic nephropathy (DN) pathology was speculated. Furthermore, the possible pathological causes and effects were discussed in detail. Potential biomarkers ( p value <0.01) were screened with Student's t-test. With the application of partial least squares-discriminant analysis (PLS-DA), different stages were distinguished. The result may be useful for the pathology study of metabolic syndromes, and may also be helpful for monitoring the progression of DM and DN.

Keywords: Fatty acid; Gas chromatography–mass spectrometry; Metabolic profiling; Diabetic mellitus; Diabetic nephropathy; Clinical metabonomics

Determination of bisphenol A in water via inhibition of silver nanoparticles-enhanced chemiluminescence by Xiaolan Chen; Can Wang; Xinmei Tan; Jianxiu Wang (pp. 92-96).

Sensitive detection of trace bisphenol A (BPA) in water samples has been accomplished via inhibition of luminol chemiluminescence (CL) by BPA on the silver nanoparticles (AgNPs)-enhanced luminol–KMnO₄ CL system for the first time. Under the optimized experimental conditions, the CL intensity was found to be proportional to the concentration of BPA ranging from 1.0×10⁻⁸ to 5.0×10⁻⁵gL⁻¹. The detection limit (3 σ) was estimated to be 1×10⁻⁹gL⁻¹. Such a concentration level is approximately 1–4 orders of magnitude lower than those reported by other methods. The feasibility of the method for determination of BPA in real water samples has been demonstrated. Via examining CL and UV–vis spectra of the CL system, possible mechanism inherent in the AgNPs-enhanced CL assay and the follow-up inhibition of BPA on the above system was proposed. The method described herein is simple, selective and obviates the need of extensive sample pretreatment.

Keywords: Silver nanoparticles; Chemiluminescence; Bisphenol A; Inhibition; Water samples

Cucurbit[6]uril nanocavity as an enhanced spectrofluorimetric method for the determination of pyrene by Valeria N. Sueldo Occello; Alicia V. Veglia (pp. 97-102).

The effect of the addition of macrocyclic host cucurbit[6]uril (CB6) on the photophysical properties of polycyclic aromatic hydrocarbon pyrene (PYR) was analyzed. The fluorescence emission spectra of the aromatic compound were determined at 25.0°C in different acidic media (HCl 18%, w/v, or HCOOH 55%, w/v) with and without CB6. A significant enhancement in the fluorescence signals in the presence of CB6 was observed. The average values of the association constant ( K_A) for the 1:1 stoichiometry complex and the relative fluorescence quantum yield ratio between the complexed and free PYR ( ϕ^PYR–CB6/ ϕ^PYR) in acidic media were (4.0±0.5)×10²M⁻¹ and (5.7±0.2), respectively.The analytical parameters improved in the presence of CB6. The relative decrease in the limit of detection was 92%. The matrix effect was evaluated in fortified samples of tap water and tea extracts. Apparent recoveries obtained by the proposed method in tap water and tea extracts were (82–103)% and (89–99)%, respectively. Selectivity studies with inorganic and organic species were performed. The method is rapid, direct, selective and simple.

Keywords: Nanosensor; Cucurbituril; Supramolecular; Polycyclic aromatic hydrocarbons; Fluorescence; Pyrene

Fabrication and characterization of a α,β,γ,δ-Tetrakis(1-methylpyridinium-4-yl)porphine/silica nanocomposite thin-layer membrane for detection of ppb-level heavy metal ions by Kyaing Kyaing Latt; Yukiko Takahashi (pp. 103-109).

A new detection membrane for filtration enrichment combined with colorimetric determination of Cd(II), Zn(II), Pb(II) and Cu(II) ions is presented. We have demonstrated the use of a dye nanoparticle coated test strip (DNTS) structured with a reagent layer for on-site analysis of trace metal ions. In this study, a [TMPyP/SA] DNTS coated with a nanocomposite layer (average thickness: 5.39μm) of α,β,γ,δ-Tetrakis(1-methylpyridinium-4-yl)porphine (TMPyP) and silica-SA on the top surface of a cellulose ester membrane filter was fabricated by a simple filtration of an aqueous TMPyP/silica-SA nanocomposite dispersion through a membrane filter. The nanocomposite formation of cationic TMPyP and negatively charged colloidal SA (9–80nm) was based on electrostatic interaction and was confirmed in the 120–800nm diameter range by a dynamic light scattering photometer (DLS). To optimize the DNTS nanocomposite layer, surface uniformity, mechanical strength, the percent retention of TMPyP, and sensitivity to Cd(II) detection for six DNTSs with five different types of silica were examined. A half[TMPyP/SA] DNTS with an average layer thickness of 2.60μm, which was prepared by controlling the amount of TMPyP and SA, demonstrated the highest sensitivity to Cd(II) ion because it had the lowest background absorbance. In addition, factors that affected the percent retention of TMPyP, such as pH and TMPyP/SA ratio, were determined. More than 99% of the TMPyP was retained on a membrane filter at pH 7.8 with a TMPyP and SA concentration of 2×10⁻⁵M and 4×10⁻⁵wt%, respectively. Filtration enrichment of 100mL of an aqueous solution containing Cd(II), Zn(II), and Pb(II) at ppb levels was achieved by concentrating the metal ions in a nanocomposite layer (the effective TMPyP area was 1.77cm², pH 10.2). The signaling surface changed from a brown color to green when the ions were captured. The percent extraction for metal ions on a half[TMPyP/SA] DNTS were estimated by TLC scanning and ICP-MS. It was observed that, when using the half[TMPyP/SA] DNTS, Cd(II) concentrations as low as 1ppb were detectable at a filtration rate of 4.0–5.0mLmin⁻¹.

Keywords: Cadmium; α,β,γ,δ-Tetrakis(1-methylpyridinium-4-yl)porphine; Nanocomposite membrane; Dye nanoparticle coated test strip; Colloidal silica; Colorimetry

Study on ionic liquid-based ultrasonic-assisted extraction of biphenyl cyclooctene lignans from the fruit of Schisandra chinensis Baill by Chun-hui Ma; Ting-ting Liu; Lei Yang; Yuan-gang Zu; Shu-ya Wang; Rong-rui Zhang (pp. 110-116).

The ionic liquid-based ultrasonic-assisted extraction (ILUAE) has been successfully applied in extracting four biphenyl cyclooctene lignans from the fruit of Schisandra chinensis Baill. Seventeen different types of ionic liquids with different cations and anions have been investigated. 0.8M 1-lauryl-3-methylimidazolium bromide ([C12mim]Br) solution was selected as solvent. In addition, the ultrasonic parameters including ultrasonic power, time for ultrasonic treatment and solid–liquid ratio have been optimized by Response Surface Method (RSM). Compared with the conventional solvent extraction, the efficiency of the approach proposed in this work is about 3.5 times as much as that of the conventional solvent extraction method. With the proposed extraction method, the extraction time has been reduced to 30min, whereas the conventional extraction method requires about 6.0h. The experimental results presented in this work indicate that the ILUAE is a simple and efficient technique for sample preparation. The proposed method is reproducible.

Keywords: Schisandra chinensis; Baill; Biphenyl cyclooctene lignans; Ionic liquid; Ultrasonic-assisted extraction; Response Surface Method

A new solid phase micro extraction for simultaneous head space extraction of ultra traces of polar and non-polar compounds by Reza Alizadeh; Nahid Mashkouri Najafi; Sharmin Kharrazi (pp. 117-121).

The results of the innovative study on a new stationary phase with high efficiency based on ZnO nano and micro rod coating on fused silica are reported in this paper. ZnO nanorods with a diameter in the range of 70–300nm and the length of about 500nm, have been grown on fused silica fibers using a hydrothermal process. The extraction properties of the fiber were investigated using headspace solid-phase microextraction (HS-SPME) mode coupled with gas chromatography–mass spectrometry detection (GC–MS) for 1,4-dichloro-nitrobenzene, biphenyl and acenaphthene. The calibration curves were linear up to 10²–10⁷ngL⁻¹ ( R²>0.995) with detection limits of 10⁻³ngL⁻¹ for biphenyl and acenaphthene and 10ngL⁻¹ for 1,4-dichloro-nitrobenzene. The RSD for single fiber and fiber-to-fiber were less than 7.0 and 11.5%, respectively. The high stability of the ZnO coating is proved at relatively high temperatures (up to 300°C) with a high extraction capacity and long lifespan (more than 100 times). Promising recoveries (91–102%) were obtained in environmental water samples analysis by applying the proposed technique.

Keywords: ZnO nanorod; Headspace SPME; GC–MS; 1,4-Dichloro-nitrobenzene; Biphenyl; Acenaphthene

Synthesis and application of a novel solid-phase microextraction adsorbent: Hollow fiber supported carbon nanotube reinforced sol–gel for determination of phenobarbital by Zarrin Es’haghi; Zohreh Rezaeifar; Gholam-Hossein Rounaghi; Zahra Alian Nezhadi; Mazyar Ahmadi Golsefidi (pp. 122-128).

A novel solid-phase microextraction technique using a hollow fiber-supported sol–gel combined with multi-walled carbon nanotubes was employed in the determination of phenobarbital in wastewater. In this new technique, a silica-based, organic–inorganic polymer containing functionalized multi-walled carbon nanotubes (MWCNTs) was prepared with sol–gel technology via the reaction of tetraethylorthosilicate (TEOS) with an acidic catalyst (HCl). This sol was injected into a polypropylene hollow fiber segment for in situ gelation. This device operated in direct immersion sampling mode. The experimental setup is simple and affordable, and the device is disposable, so there is no risk of cross-contamination or carry-over. Parameters affecting extraction such as pH of the aqueous solution, ageing and extraction times, aqueous sample volume, agitation speed and carbon nanotube amount were optimized. Linearity was observed over a range of 0.50–5000ngmL⁻¹, with an estimation coefficient ( r²) higher than 0.982. The limit of detection (LOD) was 0.32ngmL⁻¹ ( n=5), and repeatability (RSD%=2.9) was from the average of three levels of analyte concentrations (1, 1000 and 4500ngmL⁻¹) with three replicates for each within a single day. Finally, a pre-concentration factor of 2100 was obtained for phenobarbital.

Keywords: Phenobarbital; Solid-phase microextraction; Sol–gel; Carbon nanotube; Hollow fiber

A simplified Quick, Easy, Cheap, Effective, Rugged and Safe approach for the determination of trihalomethanes and benzene, toluene, ethylbenzene and xylenes in soil matrices by fast gas chromatography with mass spectrometry detection by Carmelo García Pinto; Sara Herrero Martín; José Luis Pérez Pavón; Bernardo Moreno Cordero (pp. 129-136).

A method based on simplified QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) extraction followed by large-injection volume-fast gas chromatography and mass spectrometry detection has been developed for the determination of trihalomethanes (chloroform, bromodichloromethane, dibromochloromethane and bromoform) and BTEX (benzene, toluene, ethylbenzene and xylenes) in soil samples.The simplified version of QuEChERS used meets the requirements of the “green chemistry” and provides reliable results with high sample throughput, low solvent consumption, little labour and the use of materials commonly employed in laboratories. The GC device used is equipped with a programmable temperature vaporizer (PTV), with a liner packed with Tenax-TA^®. Using the solvent-vent mode, the PTV allows the injection of large volumes of sample, affording an improvement in the sensitivity of the method. The chromatographic conditions used here allowed the separation of the compounds in less than 5.50min. Good linearity was obtained for all the target compounds, with highly satisfactory repeatability and reproducibility values. The limits of detection were in the 0.2 to 15μgkg⁻¹ range. The method was validated by the analysis of two certified reference materials.

Keywords: Quick; Easy; Cheap; Effective; Rugged and Safe approach; Trihalomethanes; Benzene; Toluene; Ethylbenzene; Xylenes; Mass spectrometry; Soil samples

Determination of phthalate esters in water samples by ionic liquid cold-induced aggregation dispersive liquid–liquid microextraction coupled with high-performance liquid chromatography by Hui Zhang; Xiaoqing Chen; Xinyu Jiang (pp. 137-142).

A novel method, termed ionic liquid cold-induced aggregation dispersive liquid–liquid microextraction (IL-CIA-DLLME), combined with high-performance liquid chromatography (HPLC) was developed for the determination of three phthalate esters in water samples. Several important parameters influencing the IL-CIA-DLLME extraction efficiency, such as the type of extraction and disperser solvent, the volume of extraction and disperser solvent, temperature, extraction time and salt effect, were investigated. Under optimal extraction conditions, the enrichment factors and extraction recoveries ranged from 174 to 212 and 69.9 to 84.8%, respectively. Excellent linearity with coefficients of correlation from 0.9968 to 0.9994 was observed in the concentration range of 2–100ngmL⁻¹. The repeatability of the proposed method expressed as relative standard deviations ranged from 2.2 to 3.7% ( n=5). Limits of detection were between 0.68 and 1.36ngmL⁻¹. Good relative recoveries for phthalate esters in tap, bottled mineral and river water samples were obtained in the ranges of 91.5–98.1%, 92.4–99.2% and 90.1–96.8%, respectively. Thus, the proposed method has excellent potential for the determination of phthalate esters in the environmental field.

Keywords: Phthalate esters; Ionic liquid; Cold-induced aggregation dispersive liquid–liquid microextraction; High performance liquid chromatography

A novel lipase-based stationary phase in liquid chromatography by Zeying He; Chunguang Lv; Xinxin Fan; Zhiqiang Zhou (pp. 143-148).

In this paper, a new chiral stationary phase (CSP) based on Candida antarctica lipase B (CALB) bounding to the surface of macroporous silica gel was developed and its stereoselectivity in enantioseparation and asymmetrical hydrolysis was evaluated. Three CALB-based HPLC columns with different amounts of enzyme immobilized were prepared by employing the immobilization method, namely “in batch”. In this technique two chromatographic supports epoxy silica and aminopropyl silica were considered. This novel CSP was proven capable of hydrolyzing chiral esters asymmetrically as bioreactor and separating several aromatic alcohols and diniconazole enantiomers.

Keywords: Chiral stationary phase; Immobilized enzyme reactor; Candida antarctica; lipase B; Lipase; Asymmetrical hydrolysis

Preparative isolation and purification of cuminaldehyde and p-menta-1,4-dien-7-al from the essential oil of Cuminum cyminum L. by high-speed counter-current chromatography by Qinqin Chen; Xuefang Hu; Jingming Li; Ping Liu; Yang Yang; Yuanying Ni (pp. 149-154).

High-speed counter-current chromatography (HSCCC) technique in semi-preparative scale was successfully used in isolation and purification of cuminaldehyde and p-menta-1,4-dien-7-al from the essential oil of Cuminum cyminum L. by using a two-phase solvent system composed of n-hexane–methanol–water (5:4:1, v/v/v). The targeted compounds were isolated, collected, purified by HSCCC in the head–tail mode, and then analyzed by gas chromatography (GC). A total of 12.72±0.22mg of cuminaldehyde and 10.61±0.27mg of p-menta-1,4-dien-7-al were obtained from 50mg of the essential oil of C. cyminum L. in less than 6h, with purities of 95.42% and 97.21%, respectively. In addition to GC-EI/MS, the identity of the cuminaldehyde was further confirmed with the retention time using the method of standard addition, while, the structural identification of p-menta-1,4-dien-7-al was performed with GC-EI/MS,¹H NMR and¹H–¹H COSY.

Keywords: High-speed counter-current chromatography (HSCCC); Cumin essential oil; Cuminaldehyde; p; -Menta-1,4-dien-7-al

Sections

Personal tools

Analytica Chimica Acta (v.689, #1)

Sections

Personal tools

Local resources

Analytica Chimica Acta (v.689, #1)