Analytica Chimica Acta (v.696, #1-2)

Display Omitted► We developed a new method for the detection of gene fragment from transgenic plants using gold nanoparticle (NP) probe and dynamic light scattering (DLS) technology. ► The whole detection process was conducted in homogeneous solution without any conjugated process. ► Compared with previously reported methods, the proposed method has a higher sensitivity, and shows a potential application in the analysis of transgenic products.The detection of transgenic products is of great significance for the development of transgenic technique. In this paper, we developed a simple, rapid and ultrasensitive method for the detection of sequence-specific Nopaline synthase (NOS) gene from the transgenic plants using label-free gold nanoparticle (NP) probe and dynamic light scattering (DLS) technology. Gold NPs were stable in NaCl solution with the presence of NOS gene probe. On the contrary, they were aggregated in NaCl solution when the probe sequence was hybridized with target sequence. The change in the size of gold NPs can be detected by DLS technology with high sensitivity. Under the optimal conditions, the average hydrodynamic diameter of gold NPs was linear with the concentration of the target sequence ranging from 1.0 × 10−13  mol L−1 to 5.0 × 10−9  mol L−1, with a detection limit of 3.0 × 10−14  mol L−1 (S/N = 3). The relative standard deviation (at 1.0 × 10−9  mol L−1 of target sequence) was 4.8% (n  = 11). The result shows that gold NPs-based DLS method has great potential in the analysis of transgenic products.
Keywords: Dynamic light scattering; Transgenic product; DNA; Gold nanoparticles;

.Display Omitted► Estrogenic compounds derived from medications and plastics are present in aqueous environments and must be quantified. ► Recent high-throughput, automated, and cost-effective GC and HPLC methods capable of trace level (ng L−1) quantification of EDCs in aqueous systems are reviewed. ► Mass spectrometry offers optimal selectivity and sensitivity required for trace EDC analysis.Recent methods of separation and detection for the quantification of trace-level concentrations of selected endocrine disrupting compounds (EDCs) from aqueous systems are reviewed. A brief introduction of the selected EDCs (natural and synthetic estrogens and plastics-derived xenoestrogens), including their characteristics and importance, is presented. Sample preparation and extraction trends are discussed. Various types of separation techniques are presented, with the express goal of emphasizing time and cost-effective methods that isolate and quantify trace-levels of multiple endocrine disruptors from aqueous systems.
Keywords: Endocrine disruptor; Estrogen; Phthalate; Phenol; Chromatography; Review;

Recent developments in handheld and portable optosensing—A review by Luis Fermín Capitán-Vallvey; Alberto J. Palma (27-46).
Display Omitted► Recent developments (2000–2010) in portable and handheld opto-chemical instrumentation are reviewed. ► Characteristics of typical portable/handheld instrumentation are discussed. ► The presented portable instrumentation is classified according to direct-recognition and reagent-based sensing. ► Key trends and future perspectives for this technology are discussed.Recent developments in portable and handheld opto-chemical analytical instrumentation over the last decade (2000–2010) are reviewed. First, the characteristics of typical portable/handheld instrumentation are discussed from different points of view: in situ operation, low energy consumption, ease of use, and self-contained devices. These advancements have improved or hastened improvements in the development of miniaturized optoelectronic and optical components, mainly solid-state devices such as different types of semiconductor lasers, light-emitting diodes, and photodiodes. A brief review of advances in these components is also presented. The numerous examples of portable instrumentation presented have been classified according to direct-recognition and reagent-based sensing, and within these, by absorption and emission-based systems. The conclusion discusses some key trends and future perspectives for this technology.
Keywords: Handheld optosensing; Portable instrumentation; Review; Optoelectronic components;

The least squares support vector machines (LS-SVM) was used to model infrared spectral data for TSH hormone secreted by thyroid, which regulates the basal metabolic rate. This model was used for direct estimation of the content of TSH in blood serum samples, and the results were comparable with those obtained with the conventional analytical method based on chemoluminescence methodology. Excellent agreement was observed between the conventional method and the newly developed calibration model based in analysis of spectral data with LS-SVM. The latter has clear advantages, because it is fast and requires no reagent once the measurements were done directly in the serum by using a simple mid-infrared spectrometer in the ATR mode. An important advantage observed in this calibration method based on LS-SVM is the remarkable capacity to avoid overfitting in the model-building step, that is, the developed method is highly robust.
Keywords: Thyroid stimulating hormone; Fourier-transform-infrared; Fast determination; Without-chemical-preprocessing; Least square support vector machines;

Fast batch injection analysis of H2O2 using an array of Pt-modified gold microelectrodes obtained from split electronic chips by Bruno D. Pacheco; Jaqueline Valério; Lúcio Angnes; Jairo J. Pedrotti (53-58).
Display Omitted► An array of gold microelectrodes modified with Pt was used for batch injection analysis of H2O2 in rainwater. ► The microelectrode array (n  = 14) was obtained from electronic chips developed for surface mounted device technology. ► The analytical frequency of the method can attain 300 determinations per hour. ► The volume-weighted mean concentration of H2O2 in rainwater investigated (n  = 25) was 14.2 μmol L−1.A fast and robust analytical method for amperometric determination of hydrogen peroxide (H2O2) based on batch injection analysis (BIA) on an array of gold microelectrodes modified with platinum is proposed. The gold microelectrode array (n  = 14) was obtained from electronic chips developed for surface mounted device technology (SMD), whose size offers advantages to adapt them in batch cells. The effect of the dispensing rate, volume injected, distance between the platinum microelectrodes and the pipette tip, as well as the volume of solution in the cell on the analytical response were evaluated. The method allows the H2O2 amperometric determination in the concentration range from 0.8 μmol L−1 to 100 μmol L−1. The analytical frequency can attain 300 determinations per hour and the detection limit was estimated in 0.34 μmol L−1 (3σ). The anodic current peaks obtained after a series of 23 successive injections of 50 μL of 25 μmol L−1 H2O2 showed an RSD < 0.9%. To ensure the good selectivity to detect H2O2, its determination was performed in a differential mode, with selective destruction of the H2O2 with catalase in 10 mmol L−1 phosphate buffer solution. Practical application of the analytical procedure involved H2O2 determination in rainwater of São Paulo City. A comparison of the results obtained by the proposed amperometric method with another one which combines flow injection analysis (FIA) with spectrophotometric detection showed good agreement.
Keywords: Hydrogen peroxide; Amperometry; Batch injection analysis; Gold microelectrode arrays; Rainwater;

Display Omitted► A method for determination of fatty acids in wines is developed for the first time. ► This method is faster as it does not require a previous derivatization process. ► The detection limits are below olfaction thresholds of the analytes in wines. ► The variability of the % of alcohol is solved using a suitable internal standard. ► The matrix effect of five analytes is solved by use of the recoveries.A new analytical method for the determination of nine short-chain fatty acids (acetic, propionic, isobutyric, butyric, isovaleric, 2-methylbutyric, hexanoic, octanoic and decanoic acids) in wines using the automated HS/SPME–GC–ITMS technique was developed and optimised. Five different SPME fibers were tested and the influence of different factors such as temperature and time of extraction, temperature and time of desorption, pH, strength ionic, tannins, anthocyans, SO2, sugar and ethanol content were studied and optimised using model solutions. Some analytes showed matrix effect so a study of recoveries was performed. The proposed HS/SPME–GC–ITMS method, that covers the concentration range of the different analytes in wines, showed wide linear ranges, values of repeatability and reproducibility lower than 4.0% of RSD and detection limits between 3 and 257 μg L−1, lower than the olfactory thresholds. The optimised method is a suitable technique for the quantitative analysis of short-chain fatty acids from the aliphatic series in real samples of white, rose and red wines.
Keywords: Fatty acids; Solid-phase microextraction; Gas chromatography–ion trap mass spectrometry; Wines;

Determination of amphetamine-type stimulants in oral fluid by solid-phase microextraction and gas chromatography–mass spectrometry by Daniele Z. Souza; Paula O. Boehl; Eloisa Comiran; Kristiane C. Mariotti; Flavio Pechansky; Paulina C.A.V. Duarte; Raquel De Boni; Pedro E. Froehlich; Renata P. Limberger (67-76).
Display Omitted► Propylchloroformate derivatization of amphetamine-type stimulants in oral fluid. ► Direct immersion solid-phase microextraction/gas chromatography–mass spectrometry. ► Linear range 2(4)–256 ng mL−1, detection limits 0.5–2 ng mL−1. ► Accuracy 98–112%, precision <15% of RSD, recovery 77–112%. ► Importance of residual evaluation in checking model goodness-of-fit.A method for the simultaneous identification and quantification of amphetamine (AMP), methamphetamine (MET), fenproporex (FEN), diethylpropion (DIE) and methylphenidate (MPH) in oral fluid collected with Quantisal™ device has been developed and validated. Thereunto, in-matrix propylchloroformate derivatization followed by direct immersion solid-phase microextraction and gas chromatography–mass spectrometry were employed. Deuterium labeled AMP was used as internal standard for all the stimulants and analysis was performed using the selected ion monitoring mode. The detector response was linear for the studied drugs in the concentration range of 2–256 ng mL−1 (neat oral fluid), except for FEN, whereas the linear range was 4–256 ng mL−1. The detection limits were 0.5 ng mL−1 (MET), 1 ng mL−1 (MPH) and 2 ng mL−1 (DIE, AMP, FEN), respectively. Accuracy of quality control samples remained within 98.2–111.9% of the target concentrations, while precision has not exceeded 15% of the relative standard deviation. Recoveries with Quantisal™ device ranged from 77.2% to 112.1%. Also, the goodness-of-fit concerning the ordinary least squares model in the statistical inference of data has been tested through residual plotting and ANOVA. The validated method can be easily automated and then used for screening and confirmation of amphetamine-type stimulants in drivers’ oral fluid.
Keywords: Amphetamine; Methamphetamine; Diethylpropion; Fenproporex; Methylphenidate; Oral fluid;

Feasibility of capillary liquid chromatography–microchip-atmospheric pressure photoionization–mass spectrometry for pesticide analysis in tomato by Anneli Kruve; Markus Haapala; Ville Saarela; Sami Franssila; Risto Kostiainen; Tapio Kotiaho; Raimo A. Ketola (77-83).
.Display Omitted► We tested feasibility of microchip based APPI for selected pesticides. ► CapillaryLC-μAPPI-MS/MS method was developed for carbamate pesticide analysis. ► A versatile μAPPI ion source can be combined with any commercial MS instrument. ► Sensitive analysis of selected carbamate pesticides from tomato was obtained.A new and sensitive analytical method, using capillary liquid chromatography (capLC) with a microfabricated heated nebulizer chip for atmospheric pressure photoionization and tandem mass spectrometry (μAPPI–MS/MS), was developed for the analysis of selected carbamate pesticides in a tomato matrix. The performance of the instrumental method was evaluated, using seven pesticides, namely oxamyl, methomyl, aldicarb, carbofuran, pirimicarb, thiocarb, and ditalimfos. The limits of detection achieved with the capLC–μAPPI–MS/MS method in the positive ion mode were low, ranging from 0.25 ng mL−1 for pirimicarb to 5 ng mL−1 for oxamyl and methomyl, corresponding to 5 and 0.25 μg kg−1 for tomato samples, respectively, which are clearly below the maximum residue limits for them in fruits and vegetables. The repeatability of the instrumental method ranged from 2.9 to 13.9% (RSD) at a low (0.05 μg mL−1) concentration level. An adequate linearity (r 2  = 0.984–0.999) at a concentration range from 0.005 to 5.0 μg mL−1 was observed for all pesticides. The results obtained show that the capLC–μAPPI–MS/MS method developed could be used for the analysis of selected pesticides from tomato.
Keywords: Pesticide analysis; Carbamate pesticide; Tomato; Liquid chromatography; Mass spectrometry; Heated nebulizer microchip; Atmospheric pressure photoionization;

Display Omitted► The feasibility of replacing KF for water content testing in bulk powders and tablets with at-line near infrared (NIR) or microwave resonance (MR) methods was demonstrated. ► Accurate NIR and MR prediction models were developed with a minimalistic approach to calibration. The NIR method can accurately predict water content in bulk powders in the range of 0.5–5% w/w. ► A general MR method was used to predict water content in two different types of blends.In this paper we demonstrate the feasibility of replacing KF for water content testing in bulk powders and tablets with at-line near infrared (NIR) or microwave resonance (MR) methods. Accurate NIR and MR prediction models were developed with a minimalistic approach to calibration. The NIR method can accurately predict water content in bulk powders in the range of 0.5–5% w/w. Results from this method were compared to a MR method. We demonstrated excellent agreement of both NIR and MR methods for powders vs. the reference KF method. These methods are applicable to in-process control or quality control environments. One of the aims of this study was to determine if a calibration developed for a particular product could be used to predict the water content of another product (with related composition) but containing a different active pharmaceutical ingredient (API). We demonstrated that, contrary to the NIR method, a general MR method can be used to predict water content in two different types of blends.Finally, we demonstrated that a MR method can be developed for at-line moisture determination in tablets.
Keywords: Near infrared (NIR); Microwave resonance technology (MRT); Process analytical technology (PAT); At-line water determination; Powders; Tablets;

Functionalization of mesoporous silica membrane with a Schiff base fluorophore for Cu(II) ion sensing by Xiaotong Chen; Akira Yamaguchi; Manato Namekawa; Toshio Kamijo; Norio Teramae; Aijun Tong (94-100).
Display Omitted► A hybrid mesoporous membrane (SB-HMM) functionalized by Schiff base fluorophores was fabricated. ► SB-HMM showed strong fluorescence with aggregation-induced emission enhancement properties. ► SB-HMM was applicable for the detection of Cu(II) in an aqueous solution with good reversibility and reproducibility.A Schiff base (SB) immobilized hybrid mesoporous silica membrane (SB-HMM) was prepared by immobilizing a Schiff base onto the pore surface of mesoporous silica (pore size = 3.1 nm) embedded in the pores of a porous anodic alumina membrane. In contrast to the non-fluorescent analogous SB molecule in homogeneous solutions, SB-HMM exhibited intense fluorescence due to emission enhancement caused by aggregation of SB groups on the pore surface. The high quantum efficiency of the surface SB groups allows SB-HMM to function as a fluorescent sensor for Cu(II) ions in an aqueous solution with good sensitivity, selectivity and reproducibility. Under the optimal conditions described, the linear ranges of fluorescence intensity for Cu(II) are 1.2–13.8 (M (R 2  = 0.993) and 19.4–60 (R 2  = 0.992) (M. The limit of detection for Cu(II) is 0.8 μM on basis of the definition by IUPAC (C LOD  = 3.3S b/m).
Keywords: Mesoporous silica; Schiff base; Aggregation-induced emission enhancement; Cu(II) detection;

Patterning pallet arrays for cell selection based on high-resolution measurements of fluorescent biosensors by Hamed Shadpour; Jon S. Zawistowski; Annadele Herman; Klaus Hahn; Nancy L. Allbritton (101-107).
► Precision stamping of the pallet arrays was demonstrated to pattern chemicals on the array surface. ► Pallet arrays patterned with fibronectin showed cell localization on to the patterned region. ► A fluorescent biosensor in cells was measured with high spatial resolution on pallet arrays.Pallet arrays enable cells to be separated while they remain adherent to a surface and provide a much greater range of cell selection criteria relative to that of current technologies. However there remains a need to further broaden cell selection criteria to include dynamic intracellular signaling events. To demonstrate the feasibility of measuring cellular protein behavior on the arrays using high resolution microscopy, the surfaces of individual pallets were modified to minimize the impact of scattered light at the pallet edges. The surfaces of the three-dimensional pallets on an array were patterned with a coating such as fibronectin using a customized stamping tool. Micropatterns of varying shape and size were printed in designated regions on the pallets in single or multiple steps to demonstrate the reliability and precision of patterning molecules on the pallet surface. Use of a fibronectin matrix stamped at the center of each pallet permitted the localization of H1299 and mouse embryonic fibroblast (MEF) cells to the pallet centers and away from the edges. Compared to pallet arrays with fibronectin coating the entire top surface, arrays with a central fibronectin pattern increased the percentage of cells localized to the pallet center by 3–4-fold. Localization of cells to the pallet center also enabled the physical separation of cells from optical artifacts created by the rough pallet side walls. To demonstrate the measurement of dynamic intracellular signaling on the arrays, fluorescence measurements of high spatial resolution were performed using a RhoA GTPase biosensor. This biosensor utilized fluorescence resonance energy transfer (FRET) between cyan fluorescent protein (CFP) and yellow fluorescent protein (YFP) to measure localized RhoA activity in cellular ruffles at the cell periphery. These results demonstrated the ability to perform spatially resolved measurements of fluorescence-based sensors on the pallet arrays. Thus, the patterned pallet arrays should enable novel cell separations in which cell selection is based on complex cellular signaling properties.
Keywords: Pallet array; Cell separation; Patterned surfaces; FRET; Cell sorting; Micro-contact printing;

Direct classification of olive oils by using two types of ion mobility spectrometers by Rocío Garrido-Delgado; Flora Mercader-Trejo; Stefanie Sielemann; Wolfgang de Bruyn; Lourdes Arce; Miguel Valcárcel (108-115).
Display Omitted► We explore the use of Ion Mobility Spectrometers for classification of olive oils. ► Three types of olive oils were analyzed with both devices coupled to headspace system. ► The ion mobility data were processed using chemometric to obtain global information. ► The classification rate was better using tritium source and separation step prior IMS.In this work, we explored the use of an Ion Mobility Spectrometry (IMS) device with an ultraviolet (UV) source, and of a Gas Chromatographic (GC) column coupled to an IM Spectrometer with a tritium source, for the discrimination of three grades of olive oil, namely: extra virgin olive oil (EVOO), olive oil (OO) and pomace olive oil (POO). The three types of oil were analyzed with both equipment combinations as coupled to a headspace system and the obtained ion mobility data were consecutively processed with various chemometric tools. The classification rate for an independent validation set was 86.1% (confidence interval at 95% [83.4%, 88.5%]) with an UV–IMS and 100% (confidence interval at 95% [87%, 100%]) using a GC–IMS system. The classification rate was improved by using a more suitable ionization source and a pre-separation step prior to the IM analysis.
Keywords: Ultraviolet–Ion Mobility Spectrometry; Gas Chromatography–Ion Mobility Spectrometry; Classification; Olive oil;

► Stepwise HPLC method development strategy. ► Automated column screening, optimization of chromatographic parameters, DryLab® modeling, and experimental verification. ► Understanding interrelated effects and design space enhances method development efficiency. ► DryLab® can be used to evaluate method robustness with acceptable accuracy.A stepwise method development strategy has been employed to develop a robust HPLC method to resolve several closely eluting structurally related impurities in an active pharmaceutical ingredient (API). This strategy consisted of automated column screening, optimization of the most critical chromatographic parameters, DryLab® modeling, and experimental verification of optimized separation conditions. DryLab® was used to predict an optimized gradient profile and separation temperature and these predictions were verified experimentally. A discussion of the accuracy of these predictions is presented. The robustness of the method was verified and the ability of DryLab® to predict, with reasonable accuracy, the outcome of such robustness studies was also examined. Once the robustness was established by the DryLab® predictions the remainder of the subsequent verification by experiment becomes a simple reiterative exercise. This study also demonstrates that factors such as column chemistry and critical chromatographic parameters can have a profound and oftentimes interrelated effect on the chromatographic separation of isomers, bromo analogs and other structurally very similar impurities. Therefore, it is critical to adopt a rational strategy, as demonstrated here, to evaluate the interplay of these factors, thereby greatly enhancing method development efficiency.
Keywords: Method development strategy; Column screening system; Method optimization; DryLab®;