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Analytica Chimica Acta (v.692, #1-2)

Editorial Board (pp. iii).

Stationary and mobile phases in hydrophilic interaction chromatography: a review by Pavel Jandera (pp. 1-25).

Hydrophilic interaction chromatography (HILIC) is valuable alternative to reversed-phase liquid chromatography separations of polar, weakly acidic or basic samples. In principle, this separation mode can be characterized as normal-phase chromatography on polar columns in aqueous-organic mobile phases rich in organic solvents (usually acetonitrile). Highly organic HILIC mobile phases usually enhance ionization in the electrospray ion source of a mass spectrometer, in comparison to mobile phases with higher concentrations of water generally used in reversed-phase (RP) LC separations of polar or ionic compounds, which is another reason for increasing popularity of this technique. Various columns can be used in the HILIC mode for separations of peptides, proteins, oligosaccharides, drugs, metabolites and various natural compounds: bare silica gel, silica-based amino-, amido-, cyano-, carbamate-, diol-, polyol-, zwitterionic sulfobetaine, or poly(2-sulphoethyl aspartamide) and other polar stationary phases chemically bonded on silica gel support, but also ion exchangers or zwitterionic materials showing combined HILIC-ion interaction retention mechanism. Some stationary phases are designed to enhance the mixed-mode retention character. Many polar columns show some contributions of reversed phase (hydrophobic) separation mechanism, depending on the composition of the mobile phase, which can be tuned to suit specific separation problems. Because the separation selectivity in the HILIC mode is complementary to that in reversed-phase and other modes, combinations of the HILIC, RP and other systems are attractive for two-dimensional applications.This review deals with recent advances in the development of HILIC phase separation systems with special attention to the properties of stationary phases. The effects of the mobile phase, of sample structure and of temperature on separation are addressed, too.

Keywords: HILIC; Stationary phases; Retention mechanism; Mixed-mode separations; Two-dimensional separations

Hyphenated analytical techniques for multidimensional characterisation of submicron particles: A review by Gaëtane Lespes; Julien Gigault (pp. 26-41).

The stakes concerning the characterisation of particles ranged in the size from 1 to 1000nm, namely submicron particles, are today more and more important. Because of the variety of particles even inside a given sample in terms of dimension, mass, charge or chemical composition a characterisation as complete as possible is needed. The possibility of obtaining a multidimensional information by relevant analytical methods is then of the greatest interest. One very interesting strategy consists in using hyphenated techniques, which are intrinsically capable to provide rapidly and accurately such information. This paper summarises the different hyphenated techniques that can be used to characterise submicron particles and is focussed on their main applications to illustrate their current and potential uses. In order to have a relevant overview various on-line separation techniques are considered in a comparative way. In the same way various on-line detectors are then presented. Finally the concepts of multidetection and multidimensional analysis are discussed and their interest showed through different typical examples of hyphenated techniques illustrating submicron particle characterisation in fields of applications such as environmental and nanomaterial sciences.

Keywords: Abbreviations; A4F; asymmetrical flow field-flow fractionation; CE; capillary electrophoresis; CHDF; capillary hydrodynamic chromatography; CNT; carbon nanotubes; CZE; capillary zone electrophoresis; DAD; diode array detector; DEP; dielectrophoresis; DLS; dynamic light scattering; El-FFF; electrical field-flow fractionation; ENM; engineered nanomaterials; ETAAS; electrothermal atomic absorption spectrometry; FFF; field-flow fractionation; Fl-FFF; flow field-flow fractionation; GC-PFPD; gas chromatography-pulsed flame photometric detector; HDC; hydrodynamic chromatography; ICP-AES; inductively coupled plasma- atomic emission spectrometry; ICP-MS; inductively coupled plasma- mass spectrometry; L; channel length; LC; liquid chromatography; LIBD; laser-induced breakdown detection; LS; light scattering; MALS; multi-angle light scattering; MALLS; multi-angle laser-light scattering; MS; mass spectrometry; NP; nanoparticles; PCS; photon correlation spectroscopy; QUELS; quasi elastic light scattering; RI; refractive index detector; RSD; relative standard deviation; Sd-FFF; sedimentation field-flow fractionation; SEC; size exclusion chromatography; SEM; scanning electron microscopy; SLS; static light scattering; SAXS; small-angle X-ray scattering; TEM; transmission electron microscopy; Th-FFF; thermal field-flow fractionation; UV–vis; ultraviolet-visible detectorLiquid chromatography; Field-flow fractionation; Capillary electrophoresis; Ultraviolet; Light scattering; Laser-induced breakdown detection; Mass spectrometry; Multidetection

Displacement solid-phase extraction on mercapto-functionalized magnetite microspheres for inductively coupled plasma mass spectrometric determination of trace noble metals by Yan Li; Yan-Feng Huang; Yan Jiang; Bo-lin Tian; Fei Han; Xiu-Ping Yan (pp. 42-49).

A flow injection online displacement solid-phase extraction (DSPE) via magnetic immobilization of mercapto-functionalized magnetite microspheres onto the inner walls of a knotted reactor (KR) coupled with inductively coupled plasma mass spectrometry was developed for selective preconcentration and determination of trace noble metals (Ru, Rh, Pd, Pt, Ir and Au) in complex matrices. Online DSPE of 2.7mL aqueous solution gave the enhancement factors of 32–46 for the six noble metals in comparison with direct nebulization of aqueous sample solution, and the detection limits (3s) of 2.1ngL⁻¹ for Ru, 1.9ngL⁻¹ for Rh, 2.5ngL⁻¹ for Pd, 1.8ngL⁻¹ for Ir, 1.9ngL⁻¹ for Pt and 1.7ngL⁻¹ for Au. The sample throughput of the developed method was about 20 samplesh⁻¹, and the relative standard deviation for eleven replicate determinations of the noble metals at the 30ngL⁻¹ level ranged from 1.2% to 2.1%. The recoveries of Ru, Rh, Pd, Pt, Ir and Au still maintained 90% even after successive 140 cycles of DSPE. The developed method was successfully applied to selective determination of trace Ru, Rh, Pd, Pt, Ir and Au in complex matrices.

Keywords: Displacement solid-phase extraction; Inductively coupled plasma mass spectrometry; Noble metals; Magnetic immobilization

In silico classification of human maximum recommended daily dose based on modified random forest and substructure fingerprint by Dong-Sheng Cao; Qian-Nan Hu; Qing-Song Xu; Yan-Ning Yang; Jian-Chao Zhao; Hong-Mei Lu; Liang-Xiao Zhang; Yi-Zeng Liang (pp. 50-56).

A modified random forest (RF) algorithm, as a novel machine learning technique, was developed to estimate the maximum recommended daily dose (MRDD) of a large and diverse pharmaceutical dataset for phase I human trials using substructure fingerprint descriptors calculated from simple molecular structure alone. This type of novel molecular descriptors encodes molecular structure in a series of binary bits that represent the presence or absence of particular substructures in the molecule and thereby can accurately and directly depict a series of local information hidden in this molecule. Two model validation approaches, 5-fold cross-validation and an independent validation set, were used for assessing the prediction capability of our models. The results obtained in this study indicate that the modified RF gave prediction accuracy of 80.45%, sensitivity of 75.08%, specificity of 84.85% for 5-fold cross-validation, and prediction accuracy of 80.5%, sensitivity of 76.47%, specificity of 83.48% for independent validation set, respectively, which are as a whole better than those by the original RF. At the same time, the important substructure fingerprints, recognized by the RF technique, gave some insights into the structure features related to toxicity of pharmaceuticals. This could help provide intuitive understanding for medicinal chemists.

Keywords: Maximum recommended daily dose (MRDD); Drug toxicity; Modified random forest; Substructure fingerprint; Machine learning

Preparation, characterization and application of organic–inorganic hybrid ractopamine multi-template molecularly imprinted capillary monolithic column by Jinxing He; Guozhen Fang; Qiliang Deng; Shuo Wang (pp. 57-62).

Four isomers of ractopamine used as multi-template molecule, a molecularly imprinted capillary monolithic column was prepared by organic–inorganic hybrid method. The prepared imprinting capillary monolithic columns were characterized by SEM and FTIR, evaluated under capillary electrochromatograhy and the effect of electroosmotic flow and selectivity were studied in detail. It was found that the prepared imprinted monolithic column had good flow-through property when the ratio of methanol and toluene was 3:2. The result indicated that the imprinted monolithic column has good selectivity for four isomers of ractopamine, and under the conditions of pH value of buffer solution was 7 and 10% acetonitrile content in buffer, four isomers of ractopamine could be separated completely.

Keywords: Capillary electrochromatograhy; Multi-template molecularly imprinted; Organic–inorganic hybrid; Ractopamine

Variable selection in near-infrared spectroscopy: Benchmarking of feature selection methods on biodiesel data by Roman M. Balabin; Sergey V. Smirnov (pp. 63-72).

During the past several years, near-infrared (near-IR/NIR) spectroscopy has increasingly been adopted as an analytical tool in various fields from petroleum to biomedical sectors. The NIR spectrum (above 4000cm⁻¹) of a sample is typically measured by modern instruments at a few hundred of wavelengths. Recently, considerable effort has been directed towards developing procedures to identify variables (wavelengths) that contribute useful information. Variable selection (VS) or feature selection, also called frequency selection or wavelength selection, is a critical step in data analysis for vibrational spectroscopy (infrared, Raman, or NIRS). In this paper, we compare the performance of 16 different feature selection methods for the prediction of properties of biodiesel fuel, including density, viscosity, methanol content, and water concentration. The feature selection algorithms tested include stepwise multiple linear regression (MLR-step), interval partial least squares regression (iPLS), backward iPLS (BiPLS), forward iPLS (FiPLS), moving window partial least squares regression (MWPLS), (modified) changeable size moving window partial least squares (CSMWPLS/MCSMWPLSR), searching combination moving window partial least squares (SCMWPLS), successive projections algorithm (SPA), uninformative variable elimination (UVE, including UVE-SPA), simulated annealing (SA), back-propagation artificial neural networks (BP-ANN), Kohonen artificial neural network (K-ANN), and genetic algorithms (GAs, including GA-iPLS). Two linear techniques for calibration model building, namely multiple linear regression (MLR) and partial least squares regression/projection to latent structures (PLS/PLSR), are used for the evaluation of biofuel properties. A comparison with a non-linear calibration model, artificial neural networks (ANN-MLP), is also provided. Discussion of gasoline, ethanol-gasoline (bioethanol), and diesel fuel data is presented. The results of other spectroscopic techniques application, such as Raman, ultraviolet-visible (UV-vis), or nuclear magnetic resonance (NMR) spectroscopies, can be greatly improved by an appropriate feature selection choice.

Keywords: Linear regression (projection to latent structures); Artificial neural networks; Support vector machines; Biofuel (ethanol-gasoline fuel, vegetable oil, biodiesel); Petroleum (crude oil); Quality control (process analytical chemistry, process analytical technology)

Rapid and selective determination of urinary lysozyme based on magnetic molecularly imprinted polymers extraction followed by chemiluminescence detection by Tao Jing; Huan Xia; Qin Guan; Wenhong Lu; Qing Dai; Jiwei Niu; Jae-Min Lim; Qiaoling Hao; Yong-Ill Lee; Yikai Zhou; Surong Mei (pp. 73-79).

A rapid, low cost and selective chemiluminescence method coupled with magnetic molecularly imprinted polymers extraction was developed to detect lysozyme in human urine samples. Compared with traditional solid-phase extraction, this method could achieve selective extraction for the lysozyme, avoid the time consuming elution from a column or centrifugation steps, and then showed great potential in the high-throughput screening of clinical samples. The parameters affecting the performance of extraction and chemiluminescence were investigated. Under optimal conditions, the whole analytical procedure was completed within 12min and spiked recovery ranged from 90.1% to 103.7% (R.S.D.≤6.7%). The limit of quantitation was 5ngmL⁻¹. Furthermore, the results obtained by the proposed method were linearly correlated to those by commercial lysozyme detection kit ( r=0.9595). Finally, the validated method was used to measure the urinary lysozyme of renal disease patients and healthy controls. The results confirmed the reliability and practicality of the protocol and revealed a good perspective of this method for biological sample analysis.

Keywords: Molecularly imprinted polymers; Magnetic separation; Chemiluminescence; Lysozyme; Urine samples

Extraction of fluoxetine from aquatic and urine samples using sodium dodecyl sulfate-coated iron oxide magnetic nanoparticles followed by spectrofluorimetric determination by Habib Bagheri; Omid Zandi; Ali Aghakhani (pp. 80-84).

A new method based on the combination of magnetic solid phase extraction (MSPE) and spectrofluorimetric determination was developed for isolation and preconcentration of fluoxetine form aquatic and biological samples using sodium dodecyl sulfate (SDS) coated Fe₃O₄ nanoparticles (NPs) as a sorbent. The unique properties of Fe₃O₄ NPs including high surface area and strong magnetism were utilized effectively in the MSPE process. Effect of different parameters influencing the extraction efficiency of fluoxetine including the amount of Fe₃O₄ and SDS, pH value, sample volume, extraction time, desorption solvent and time were optimized. Under optimized condition, the method was successfully applied to the extraction of fluoxetine from water and urine samples and absolute recovery amount of 85%, detection limit of 20μgL⁻¹ and a relative standard deviation (RSD) of 1.4% were obtained. The method linear response was over a range of 50–1000μgL⁻¹ with R²=0.9968. The relative recovery in different aquatic and urine matrices were investigated and values of 80% to 104% were obtained. The whole procedure showed to be conveniently fast, efficient and economical for extraction of fluoxetine from environmental and biological samples.

Keywords: Magnetic solid phase extraction; Fe; ₃; O; ₄; Fluoxetine; Spectrofluorimetry; Water analysis; Urine analysis

A statistical design of experiments for optimizing the MALDI-TOF-MS sample preparation of polymers. An application in the assessment of the thermo-mechanical degradation mechanisms of poly (ethylene terephthalate) by J.D. Badía; E. Strömberg; A. Ribes-Greus; S. Karlsson (pp. 85-95).

The sample preparation procedure for MALDI-TOF MS of polymers is addressed in this study by the application of a statistical Design of Experiments (DoE). Industrial poly (ethylene terephthalate) (PET) was chosen as model polymer. Different experimental settings (levels) for matrixes, analyte/matrix proportions and concentrations of cationization agent were considered. The quality parameters used for the analysis were signal-to-noise ratio and resolution. A closer inspection of the statistical results provided the study not only with the best combination of factors for the MALDI sample preparation, but also with a better understanding of the influence of the different factors, individually or in combination, to the signal. The application of DoE for the improvement of the MALDI measure of PET stated that the best combination of factors and levels was the following: matrix (dithranol), proportion analyte/matrix/cationization agent (1/15/1, V/V/V), and concentration of cationization agent (2gL⁻¹). In a second part, multiple processing by means of successive injection cycles was used to simulate the thermo-mechanical degradation effects on the oligomeric distribution of PET under mechanical recycling. The application of MALDI-TOF-MS showed that thermo-mechanical degradation primarily affected initially predominant cyclic species. Several degradation mechanisms were proposed, remarking intramolecular transesterification and hydrolysis. The ether links of the glycol unit in PET were shown to act as potential reaction sites, driving the main reactions of degradation.

Keywords: Abbreviations; ϕ; diameter screw (injection machine); d; diameter pellet; DEG; diethyleneglycol; DHB; 2,5-dihydroxybenzoic acid; DoE; Design of Experiments; EG; ethylene glycol; F; factor (for the DoE); FA; ferulic acid; G; glycol unit (EG); GLM; general linear model; HABA; hydroxyphenylazo benzoic acid; IAA; trans-3-indoleacrylic acid; IP; interaction plot; m; number of GT repeating units (; m; >; n; ); m; /; z; mass-to-charge ratio; MALDI; matrix-assisted laser desorption/ionization; MAC; combination of matrix/analyte/cationization agent; MEP; main effects plot; MMD; molar mass distribution; MS; mass spectrometry; n; number of GT repeating units; NaTFA; sodium trifluoroacetate; P; also; p; -value, statistic (for the DOE); PET; poly(ethylene terephthalate); pc-PET; post-consumed PET; RES; resolution; RPET-; i; PET reprocessed; i; cycles; SA; sample analysis; SP; sample preparation; S; /; N; signal-to-noise ratio; T; terephthalate unit; THA; 2,4,6-trihydroxy acetophenone; TOF; time of flight; V; volume; VPET; virgin PETMatrix-assisted laser desorption/ionization time-of-flight; Mass spectrometry; Design of Experiments; Poly (ethylene terephthalate); Recycling; Thermo-mechanical degradation

Surface-enhanced Raman scattering for arsenate detection on multilayer silver nanofilms by Mei-Juan Han; Jumin Hao; Zhonghou Xu; Xiaoguang Meng (pp. 96-102).

Surface-enhanced Raman scattering (SERS) has recently emerged as a promising method for chemical and biomolecular sensing. SERS quantification analysis of arsenate (As(V)) was investigated using multilayer Ag nanofilms deposited on glass slides as SERS-active substrates (Ag/GL substrates) by an electroless deposition process. The As(V) limit of detection (LOD) was determined to be ∼5μgL⁻¹ or lower with or without coexisting multiple background electrolytes (Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl⁻, NO₃⁻, SO₄²⁻ and H₂PO₄⁻). The presence of the background electrolytes at low concentrations was observed to enhance the SERS sensitivity of the substrate towards As(V) more than twofold. Standard calibration curves were prepared in the absence and presence of the background electrolytes. Excellent linear relationships between the peak heights of the As(V) SERS band at ∼780cm⁻¹ and the As(V) concentrations were obtained in a concentration range of 0–250μgL⁻¹. The selectivity of the Ag nanofilm towards oxyanions was examined to be in the order of As(V)≫phosphate≫nitrate, sulphate. A low sample-to-sample relative standard deviation (RSD) of 5.2% was also determined, suggesting the Ag/GL substrate was uniform and highly reproducible. Experimental results indicated that the SERS method could be used for quantitative analysis of As(V) in groundwater samples.

Keywords: Surface-enhanced Raman scattering; Arsenate detection; Silver nanofilm; Electroless deposition; Groundwater; Sensor

Rapid fluorescence determination of diquat herbicide in food grains using quantum dots as new reducing agent by Carolina Carrillo-Carrión; Bartolomé M. Simonet; Miguel Valcárcel (pp. 103-108).

CdSe/ZnS QDs have demonstrated capacity to act as reducing agent in organic media such as acetonitrile and ethanol. By using fluorescence and Raman spectroscopy, it has been demonstrated that QDs reduce diquat herbicide to its monocation radical. The reaction is characterized to present a high reaction rate making possible to perform the reaction by simple filtration of the solution containing the herbicide through a QDs modified filter. The monocation radical presents a high fluorescence emission spectrum which was selected as the analytical signal to quantify the diquat herbicide. The method described here for the analysis of diquat herbicide in oat grains is simple and fast allowing the analysis of trace level of herbicide in only 6min. The excellent sensitivity and reproducibility of the methods indicate that the reaction is favoured from both thermodynamic and kinetic point of view. The results presented open up the possibility to use QDs as redox agent. The sensitivity of the method expressed as detection limit was only of 0.01mgkg⁻¹.The lineal range was between 0.05 and 0.5mgkg⁻¹. The time of analysis per sample, including extraction, reaction and fluorescent measurement was only of 6min.

Keywords: CdSe/ZnS quantum dots; Reduction reaction; Diquat herbicide/desecant; Oat grains; Fluorescence measurements

Used gold nano-particles as an on/off switch for response of a potentiometric sensor to Al(III) or Cu(II) metal ions by Mohammad Hossein Mashhadizadeh; Rasoul Pourtaghavi Talemi (pp. 109-115).

The potentiometric response of a carbon paste electrode modified with silica sol–gel and mercaptosuccinic acid (MSA) in the presence and absence of gold nano-particles was studied. The results showed that the electrode with gold nano-particles was responded to Al³⁺ ions as a hard metal ion. On the other hand, the electrode without gold nano-particles was responded to copper ions as a soft metal ion. The electrodes without and with gold nano-particles exhibits a Nernstian slope of 29.1 and 19.2mVdecade⁻¹ for copper and aluminum ions over a wide concentration range of 4.3×10⁻⁷–1.0×10⁻² and 4.5×10⁻⁷–1.6×10⁻³molL⁻¹, respectively. The detection limits of electrodes were 4.0×10⁻⁷ and 1.6×10⁻⁷molL⁻¹ for copper and aluminum ions, respectively.

Keywords: Gold nanoparticle; Mercaptosuccinic acid; Potentiometric sensor; Carbon paste electrode; Hard soft metal ions

Gold–silver–graphene hybrid nanosheets-based sensors for sensitive amperometric immunoassay of alpha-fetoprotein using nanogold-enclosed titania nanoparticles as labels by Biling Su; Dianping Tang; Qunfang Li; Juan Tang; Guonan Chen (pp. 116-124).

A new sandwich-type electrochemical immunosensor with enhanced sensitivity was developed for detection of alpha-fetoprotein (AFP, as a model analyte) in biological fluids by using nanogold-enclosed titania nanoparticle (AuTi)-labeled secondary antibody on a gold–silver–graphene hybrid nanosheet (AuAgGP)-functionalized glassy carbon electrode (GCE). The presence of the AuAgGP nanosheets not only enhanced the immobilized amount of biomolecules, but also improved the electrochemical properties of the immunosensor. With the aid of AuTi nanolabels, the electrochemical signal was greatly amplified in comparison with pure nanogold or titania-based labels. Under optimal conditions, the sensitivity and dynamic range of the immunosensor were evaluated by using the labeled horseradish peroxidase on the AuTi as trace and H₂O₂ as enzyme substrate, and exhibited a wide dynamic range of 0.001–200ngmL⁻¹ with a low detection limit (LOD) of 0.5pgmL⁻¹ AFP (at 3 σ). Both the intra- and inter-assay coefficients of variation were less than 10%. The current of the immunosensor at 13th day was as much as 90% of the initial current. In addition, the methodology was evaluated for 8 positive serum specimens obtained from hepatocarcinoma patients and 19 negative sera, and validated with the commercially available Roche 2010 Electrochemiluminescent (ECL) Automatic Analyzer. No significant differences at the 95% confidence level were encountered between two methods.

Keywords: Gold–silver–graphene hybrid nanomaterials; Nanogold-enclosed titania nanoparticles; Alpha-fetoprotein; Electrochemical immunosensor; Enhanced sensitivity

A disposable electrochemical immunosensor for prolactin involving affinity reaction on streptavidin-functionalized magnetic particles by María Moreno-Guzmán; Araceli González-Cortés; Paloma Yáñez-Sedeño; José M. Pingarrón (pp. 125-130).

A novel electrochemical immunosensor was developed for the determination of the hormone prolactin. The design involved the use of screen-printed carbon electrodes and streptavidin-functionalized magnetic particles. Biotinylated anti-prolactin antibodies were immobilized onto the functionalized magnetic particles and a sandwich-type immunoassay involving prolactin and anti-prolactin antibody labelled with alkaline phosphatase was employed. The resulting bio-conjugate was trapped on the surface of the screen-printed electrode with a small magnet and prolactin quantification was accomplished by differential pulse voltammetry of 1-naphtol formed in the enzyme reaction using 1-naphtyl phosphate as alkaline phosphatase substrate. All variables involved in the preparation of the immunosensor and in the electrochemical detection step were optimized. The calibration plot for prolactin exhibited a linear range between 10 and 2000ngmL⁻¹ with a slope value of 7.0nAmLng⁻¹. The limit of detection was 3.74ngmL⁻¹. Furthermore, the modified magnetic beads–antiprolactin conjugates showed an excellent stability. The immunosensor exhibited also a high selectivity with respect to other hormones. The analytical usefulness of the immnunosensor was demonstrated by analyzing human sera spiked with prolactin at three different concentration levels.

Keywords: Prolactin; Immunosensor; Electrochemical; Magnetic particles; Screen-printed electrodes

Immobilization of trypsin on sub-micron skeletal polymer monolith by Chunhe Yao; Li Qi; Wenbin Hu; Fuyi Wang; Gengliang Yang (pp. 131-137).

A new kind of immobilized trypsin reactor based on sub-micron skeletal polymer monolith has been developed. Covalent immobilization of trypsin on this support was performed using the epoxide functional groups in either a one- or a multi-step reaction. The proteolytic activity of the immobilized trypsin was measured by monitoring the formation of N-α-benzoyl-l-arginine (BA) which is the digestion product of a substrate N-α-benzoyl-l-arginine ethyl ester (BAEE). Results showed that the digestion speed was about 300 times faster than that performed in free solution. The performance of such an enzyme reactor was further demonstrated by digesting protein myoglobin. It has been found that the protein digestion could be achieved in 88s at 30°C, which is comparable to 24h digestion in solution at 37°C. Furthermore, the immobilized trypsin exhibits increased stability even after continuous use compared to that in free solution. The present monolithic enzyme-reactor provides a promising platform for the proteomic research.

Keywords: High internal phase emulsion; Immobilized enzymatic reactor; Immobilized trypsin; Monolithic column; Protein digestion

Simultaneous determination of fumonisins B₁, B₂ and B₃ contaminants in maize by ultra high-performance liquid chromatography tandem mass spectrometry by Yiping Ren; Yu Zhang; Shiyun Han; Zheng Han; Yongning Wu (pp. 138-145).

The present work developed an analytical method for simultaneous determination of fumonisins B₁, B₂ and B₃ residues in maize by ultra high-performance liquid chromatography combined with electrospray ionization triple quadrupole tandem mass spectrometry (UHPLC–MS/MS) under the multiple reaction monitoring (MRM) mode, and especially focused on the optimization of extraction, clean-up, UHPLC separation and MS/MS parameters. The method involves addition of fumonisins isotope internal standards, extraction with a mixture of acetonitrile and water and clean-up with solid-phase extraction (SPE) cartridges before UHPLC–MS/MS analysis. A single-laboratory method validation was conducted by testing three different spiking levels for repeatability and recovery according to International Union of Pure and Applied Chemistry (IUPAC) guidelines. The LOQ of FB₁, FB₂ and FB₃ were 1.50, 1.65 and 0.4μgkg⁻¹, respectively, which were lower than the criteria of EU, USA and other countries regarding minimum residue limits of fumonisins in foods including baby foods and feedstuffs. Recoveries of three fumonisins ranged from 80.9% to 97.0% with RSD values of 2.4–11.1%.The advantages of this method include simple pretreatment, rapid determination and high sensitivity, and it fulfills the requirements for food analysis with respect to minimum residue limits of fumonisins in various countries.

Keywords: Fumonisins; Maize; Solid-phase extraction; Ultra high-performance liquid chromatography tandem mass spectrometry; Multiple reaction monitoring

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Analytica Chimica Acta (v.692, #1-2)