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Analytica Chimica Acta (v.706, #2)

Editorial Board (pp. i).

Description and validation of coupling high performance liquid chromatography with resonance Rayleigh scattering in aminoglycosides determination by Lei Zhang; Jingdong Peng; Jinxia Tang; Binfang Yuan; Rongxing He; Ying Xiao (pp. 199-204).
Theoretical and experimental analysis had proved that aminoglycosides reacted with Congo red to form binary compounds simultaneously, which led to a novel HPLC–RRS strategy being applied in substances which are not fluorescing and not UV absorbed.Display Omitted► A novel HPLC–RRS strategy was shown in this study. ► Theoretical and experimental analysis had proved the feasibility of this method. ► Because of its specificity, no interference from the matrix was observed. ► The analytes in biological matrix were all well resolved without any interference. ► It provided new insights for analytes lack of useful spectroscopic and electrochemical properties.In view of the fact that many substances generally exhibit very little ultraviolet absorbance and the absence of native fluorescence, a new strategy with simple instrumentation and excellent analytical performance combining high performance liquid chromatography (HPLC) with resonance Rayleigh scattering (RRS) was developed. It was validated for the quantification of aminoglycosides (AGs). This fact was also carefully calculated by quantum chemistry. However, the sensitivity was probably limited by the volume of flow-through cell. Therefore, the result calls for a suitable one to ensure optimal RRS signal. Interestingly, when serum or urine samples of analytes were analyzed by this method, they were all well resolved without any interference, which would hold a new perspective to be applied in the determination of substances in biological matrix.

Keywords: Abbreviations; RRS; resonance Rayleigh scattering; HPLC; -; RRS; the method coupling HPLC with RRS; AGs; aminoglycosides; CR; Congo red; AMK; amikacin; NTL; netilmicin; ETM; etimicin; RSD; the relative standard deviationsAminoglycosides; Congo red; High performance liquid chromatography; Resonance Rayleigh scattering


Recent applications in chiral high performance liquid chromatography: A review by Alberto Cavazzini; Luisa Pasti; Alessandro Massi; Nicola Marchetti; Francesco Dondi (pp. 205-222).
Display Omitted► Papers about chiral separations by HPLC published since 2009 were reviewed. ► Emphasis given to new classes of chiral stationary phases with enhanced properties. ► Sources: Web of Science, Scopus, SciFinder databases.The most important and broadly used chiral stationary phases (CSPs) for high performance liquid chromatography (HPLC) are reviewed. After a short description of the state of the art, for each kind of CSP the most important contributions published in the last couple of years are summarized. For the sake of classification, these works have been divided into studies on enantiorecognition mechanisms, new materials, and new applications. Emphasis is given to new, emerging CSPs that seem to possess all requisites to be considered potentially successful chiral separation media in the next future.

Keywords: Chiral stationary phases; Chiral liquid chromatography; Polysaccharides; Macrocyclic antibiotics; Brush type chiral stationary phases; Cyclofructans; Oligoproline


Application of the interference standard method for the determination of sulfur, manganese and iron in foods by inductively coupled plasma mass spectrometry by Renata S. Amais; George L. Donati; Joaquim A. Nóbrega (pp. 223-228).
Display Omitted► Argon species in the plasma are used to correct for spectral interferences in ICP-QMS. ► The interference standard method (IFS) significantly improves accuracy. ► Interfering ions and IFS probes present similar behaviors in the plasma. ► Significant improvements are obtained for some severe interference affected elements. ► S, Mn and Fe are successfully determined in meat and grain samples.The interference standard method (IFS) is evaluated to improve the accuracy of the determination of S, Mn and Fe in meat and grain samples by inductively coupled plasma quadrupole mass spectrometry (ICP-QMS). Due to ICP-QMS relatively low resolution, polyatomic interferences caused by16O2+, (16OH)2+,40Ar14NH+, and40Ar16O+, for example, can compromise determinations at m/ z 32, 34, 55, and 56, respectively. In IFS, differently from traditional internal standard methods, plasma naturally occurring species are used to correct for variations in the interference signal rather than the analyte signal. The method is based on the hypothesis that the interfering ion and the IFS probe present similar behaviors in the plasma, and that by using the analytical (analyte plus interference)/IFS signal ratio one could reduce variations due to interference and, consequently, improve accuracy. In this work, this strategy is evaluated in real sample applications and significant improvements on accuracy are observed for32S,34S,55Mn, and56Fe determinations. Recoveries ranging from 72% for Mn to 105% for Fe in two different standard reference materials are obtained using the38Ar probe. These analytes are successfully determined in meat and grain samples with concentrations ranging from 4.42μgg−1 for Mn in corn to 7270μgg−1 for S in chicken liver. The method is compared with other strategies such as internal standardization and mathematical correction. No instrumental modification or introduction of foreign gases is required, which is especially attractive for routine applications.

Keywords: ICP-QMS; Spectral interferences; Polyatomic ions; Interference standard; Argon species


Development of a technique based on multi-spectral imaging for monitoring the conservation of cultural heritage objects by Emilio Marengo; Marcello Manfredi; Orfeo Zerbinati; Elisa Robotti; Eleonora Mazzucco; Fabio Gosetti; Greg Bearman; Fenella France; Pnina Shor (pp. 229-237).
Display Omitted► We develop a new approach for the monitoring of cultural heritage objects. ► The technique uses multispectral imaging coupled with multivariate analysis. ► We tested the technique on simulated data and on a sample of parchment artificially aged. ► The technique detected the degraded area and the interested wavelengths even for small degradations.A new approach for monitoring the state of conservation of cultural heritage objects surfaces is being developed. The technique utilizes multi-spectral imaging, multivariate analysis and statistical process control theory for the automatic detection of a possible deterioration process, its localization and identification, and the wavelengths most sensitive to detecting this before the human eye can detect the damage or potential degradation changes occur. A series of virtual degradation analyses were performed on images of parchment in order to test the proposed algorithm in controlled conditions. The spectral image of a Dead Sea Scroll (DSS) parchment, IAA (Israel Antiquities Authority) inventory plate # 279, 4Q501 Apocryphal Lamentations B, taken during the 2008 Pilot of the DSS Digitization Project, was chosen for the simulation.

Keywords: Surface artifacts monitoring; Cultural heritage preservation; Multi-spectral imaging; Multivariate analysis


Prediction of compositional and sensory characteristics using RGB digital images and multivariate calibration techniques by Giorgia Foca; Francesca Masino; Andrea Antonelli; Alessandro Ulrici (pp. 238-245).
Display Omitted► Visual aspect of a sample can be quantified by RGB images. ► Colour-related information is codified in the form of a signal named colourgram. ► Colourgrams are used to build multivariate calibration/feature selection models. ► Sensory and compositional characteristics of samples (e.g. food) can be predicted. ► Reconstruction of selected features as images allows direct and easy interpretation.In the present paper, the possibility to use the information contained in RGB digital images to gain a fast and inexpensive quantification of colour-related properties of food is explored. To this aim, we present an approach which consists, as first step, in condensing the colour related information contained in RGB digital images of the analysed samples in one-dimensional signals, named colourgrams. These signals are then used as descriptor variables in multivariate calibration models. The feasibility of this approach has been tested using as a benchmark a series of samples of pesto sauce, whose RGB images have been used to predict both visual attributes defined by a panel test and the content of various pigments (chlorophylls a and b, pheophytins a and b, β-carotene and lutein). The possibility to predict correctly the values of some of the studied parameters suggests the feasibility of this approach for fast monitoring of the main aspect-related properties of a food matrix. The values of the squared correlation coefficient computed in prediction on a test set(RPred2) for green and yellow hues were greater than 0.75, whileRPred2 values greater than 0.85 were obtained for the prediction of total chlorophylls content and of chlorophylls/pheophytins ratio. The great flexibility of this blind analysis method for the quantitative evaluation of colour related features of matrices with an inhomogeneous aspect suggests that it is possible to implement automated, objective, and transferable systems for fast monitoring of raw materials, different stages of the manufacture and end products, not necessarily for the food industry only.

Keywords: RGB digital image analysis; Multivariate calibration; Wavelet transform; Colour; Food aspect; Pigments; Sensory evaluation


Simultaneous voltammetric determination of acetaminophen and tramadol using Dowex50wx2 and gold nanoparticles modified glassy carbon paste electrode by Bankim J. Sanghavi; Ashwini K. Srivastava (pp. 246-254).
Display Omitted► Simultaneous determination of acetaminophen (ACOP) and tramadol (TRA) carried out. ► Adsorptive stripping square wave voltammetry (AdSSWV) employed for the determination. ► Dowex50wx2 and gold nanoparticles modified glassy carbon paste electrode used for the analysis. ► Analysis of ACOP and TRA in pharmaceutical formulations, blood serum and urine. ► Dowex50wx2 used for the first time as a modifier for organic molecules.A glassy carbon paste electrode (GCPE) modified with a cation exchanger resin, Dowex50wx2 and gold nanoparticles (D50wx2–GNP–GCPE) has been developed for individual and simultaneous determination of acetaminophen (ACOP) and tramadol (TRA). The electrochemical behavior of both the molecules has been investigated employing cyclic voltammetry (CV), chronocoulometry (CC), electrochemical impedance spectroscopy (EIS) and adsorptive stripping square wave voltammetry (AdSSWV). The studies revealed that the oxidation of ACOP and TRA is facilitated at D50wx2–GNP–GCPE. Using AdSSWV, the method allowed simultaneous determination of ACOP and TRA in the linear working range of 3.34×10−8 to 4.22×10−5M with detection limits of 4.71×10−9 and 1.12×10−8M (S/N=3) for ACOP and TRA respectively. The prepared modified electrode shows several advantages such as simple preparation method, long-time stability, ease of preparation and regeneration of the electrode surface by simple polishing and excellent reproducibility. The high sensitivity and selectivity of D50wx2–GNP–GCPE were demonstrated by its practical application in the determination of both ACOP and TRA in pharmaceutical formulations, urine and blood serum samples.

Keywords: Acetaminophen; Tramadol; Dowex50wx2; Gold nanoparticles; Stripping voltammetry


A strategy for constructing sensitive and renewable molecularly imprinted electrochemical sensors for melamine detection by Jianping Li; Zhiqiang Chen; Yuping Li (pp. 255-260).
A strategy for preparing molecularly imprinted electrochemical sensors with a highly sensitive and easily renewable film is proposed. Film renewability was achieved by embedding MIP particles in a solid paraffin carbon paste, and the high sensitivity was detected using a highly sensitive enzyme amplifier.Display Omitted► A strategy for preparing molecularly imprinted electrochemical sensors with a highly sensitive and easily renewable film is proposed. ► MIP particles were synthesized and embedded in a solid paraffin carbon paste to prepare the MIP sensor. ► The detection signals were amplified because of enzymatic reaction to the H2O2 catalytic oxidation. ► Sensitive film renewability was achieved by embedding MIP particles in a solid paraffin carbon paste. ► Melamine was selected as the template molecule.A novel strategy for preparing highly sensitive and easily renewable molecularly imprinted polymer (MIP) sensors was proposed. Using melamine (MA) as the template molecule, MIP particles were synthesized and embedded in a solid paraffin carbon paste to prepare the MIP sensor. MA was indirectly determined from the competition between the reactions of MA and horseradish peroxidase-labeled MA (MA-HRP) with the vacant cavities. The detection signals were amplified because of enzymatic reaction to the H2O2 catalytic oxidation. Sensitivity was markedly improved. Sensor renewal was achieved by a simple mechanical polishing of the sensitive film. The linear range for MA detection was 0.005–1μmolL−1 and the detection limit was 0.7nmolL−1. The molecularly imprinted solid paraffin carbon paste sensor was used for MA detection in milk samples.

Keywords: Molecularly imprinted; Sensor; Melamine; Horseradish peroxidase; Solid paraffin carbon paste


Influence of acidification on the optical properties and molecular composition of dissolved organic matter by Malak M. Tfaily; David C. Podgorski; Jane E. Corbett; Jeffrey P. Chanton; William T. Cooper (pp. 261-267).
Display Omitted► We characterized the effects of acidification on dissolved organic matter (DOM). ► Methods used included FT-ICR mass spectrometry and 3-D fluorescence spectroscopy. ► Fluorescence decreased as a function of composition and fluorophore. ► Compositional changes included an increase in highly oxygenated compounds. ► For samples with a low SUVA value, freezing is recommended for sample preservation.Acidification is a common method for preserving dissolved organic matter (DOM) in natural water samples until sophisticated laboratory analyses can be performed. However, little is known about the effects of this practice on the composition and optical properties of DOM. In this study, the effects of acidification on DOM in porewater samples collected from the RL IV bog system of the Glacial Lake Agassiz Peatlands in northern Minnesota were characterized. Molecular composition was determined by ultrahigh resolution mass spectrometry and optical properties by UV absorption and three-dimensional fluorescence spectroscopy. Excitation–emission matrix fluorescence spectroscopy results indicate that the fluorescence properties of the peatland porewater DOM were sensitive to pH and that the observed changes were fluorophore dependent. Ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry revealed the appearance of newly formed, oxygen-rich compounds upon acidification. The extent to which these oxygen-rich compounds were formed was also dependent on the composition of the DOM.

Keywords: Dissolved organic matter (DOM); Sample preservation; Optical properties; Molecular composition; Ultrahigh resolution mass spectrometry of DOM; UV–vis spectroscopy; Excitation–emission matrix fluorescence spectroscopy


Dispersive suspended microextraction by Zhong-Hua Yang; Yu Liu; Yue-Le Lu; Tong Wu; Zhi-Qiang Zhou; Dong-Hui Liu (pp. 268-274).
.Display Omitted► A novel technique termed dispersive suspended microextraction has been developed. ► Varieties of experiment factors which would affect the experiment results were optimized and selected. ► Compared with other LPME, the most difference is that the restoration step instead of centrifugation process. ► In this technique, the experiment process was divided into two critical steps: the extraction step and the restoration step. ► In the final experiment, this method has been successfully applied in the analysis of wine and tap water samples.A novel sample pre-treatment technique termed dispersive suspended microextraction (DSME) coupled with gas chromatography-flame photometric detection (GC-FPD) has been developed for the determination of eight organophosphorus pesticides (ethoprophos, malathion, chlorpyrifos, isocarbophos, methidathion, fenamiphos, profenofos, triazophos) in aqueous samples. In this method, both extraction and two phases’ separation process were performed by the assistance of magnetic stirring. After separating the two phases, 1μL of the suspended phase was injected into GC for further instrument analysis. Varieties of experiment factors which could affect the experiment results were optimized and the following were selected: 12.0μL p-xylene was selected as extraction solvent, extraction speed was 1200rpm, extraction time was 30s, the restoration speed was 800rpm, the restoration time was 8min, and no salt was added. Under the optimum conditions, limits of detections (LODs) varied between 0.01 and 0.05μgL−1. The relative standard deviation (RSDs, n=6) ranged from 4.6% to 12.1%. The linearity was obtained by five points in the concentration range of 0.1–100.0μgL−1. Correlation coefficients ( r) varied from 0.9964 to 0.9995. The enrichment factors (EFs) were between 206 and 243. In the final experiment, the developed method has been successfully applied to the determination of organophosphorus pesticides in wine and tap water samples and the obtained recoveries were between 83.8% and 101.3%. Compared with other pre-treatment methods, DSME has its own features and could achieve satisfied results for the analysis of trace components in complicated matrices.

Keywords: Organophosphorus pesticides; Dispersive suspended microextraction; Gas chromatography; Wine; Tap water


Synthesis and characterization of bisphenol-A imprinted polymer as a selective recognition receptor by M.C. Cela-Pérez; M.M. Castro-López; A. Lasagabáster-Latorre; J.M. López-Vilariño; M.V. González-Rodríguez; L.F. Barral-Losada (pp. 275-284).
Display Omitted► The binding affinity of BPA-MIP high affinity sites is very resilient. ► A low volatile solvent and a non-reactive linear polymer are a good porogen system. ► Selectivity recognition is achieved for aqueous samples. ► The limiting step of the adsorption process is carried out in the imprinted cavities. ► The adsorption capacity is kept when the sorbent is regenerated.Molecularly imprinted polymers (MIPs) are currently used to provide selectivity in chemical sensors. In this context, a non-covalent bisphenol-A (BPA)-imprinted polymer using 4-vinylpyridine (4-Vpy) as the functional monomer, ethylene glycol dimethacrylate (EGDMA) as crosslinker and a low volatile solvent, triethylene glycol dimethyl ether (TRIGLYME), in combination with a non-reactive linear polymer, poly (vinyl acetate) (PVAc), as porogen, was synthesized with a simple polymerization procedure. Batch rebinding experiments were carried out to evaluate the binding and selectivity properties of the BPA-MIP. The experimental adsorption isotherms were fitted and a heterogeneous distribution of the binding sites was found. The selectivity of MIP demonstrated higher affinity for target BPA and BPA-analogues over other common water pollutants. The adsorption kinetics followed the pseudo-second-order kinetic model so that the specific adsorption in the imprinted cavities by two strong hydrogen bonds could be described as a chemisorption process. The diffusion mechanism was determined by the intra-particle diffusion and Boyd models, both of them revealing that the adsorption was mainly governed by intra-particle diffusion. MIP was shown to be promising for regeneration without significant loss in adsorption capacity.

Keywords: Molecularly imprinted polymer; Bisphenol-A; Affinity distribution; Kinetics; Adsorption


Differentiation of various kinds of Fructus schisandrae by surface desorption atmospheric pressure chemical ionization mass spectrometry combined with Principal Component Analysis by Zifeng Pi; Hao Yue; Li Ma; Liying Ding; Zhiqiang Liu; Shuying Liu (pp. 285-290).
Various kinds of Fructus schisandrae were studied by surface desorption atmospheric pressure chemical ionization mass spectrometry (DAPCI-MS) for the first time and the schematic diagram was shown in . The results demonstrated that DAPCI-MS in combination with PCA was a feasible technique for high-throughput differentiation of various kinds of F. schisandrae. It is also possible that DAPCI-MS could become a powerful technology in the studies of traditional Chinese medicine studies and in situ analysis of Chinese herbs.Display Omitted► The method is a convenient technique for differentiation of Fructus schisandrae. ► The analysis was operated in the ambient environment without sample pretreatment. ► The analytical time for each sample was only 30s.Various kinds of Fructus schisandrae were studied by surface desorption atmospheric pressure chemical ionization mass spectrometry (DAPCI-MS) without any sample pretreatment. The volatile components in F. schisandrae were detected in the ambient environment and the analytical time for each sample was only 30s. F. schisandrae are produced mainly in 5 different geographical regions (Elunchun, Mudanjiang, Tonghua, Tieling and Shangluo), and they could be successfully differentiated according to their chemical markers by Principal Component Analysis (PCA). A total of 8 components which gave more contribution for PCA analysis were unambiguously identified by comparison of the MS2 data of chemical markers to the data of reference compounds as reported in the literature. Similarly, wild grown and cultivatable species of F. schisandrae were well separated by the above-mentioned method. In addition, raw and processed cultivatable F. schisandrae (steamed by water, alcohol, vinegar, or honey, and fried by honey) were found to be clustered at different location, respectively. Furthermore, the clustered degree of differently processed products was correlated with their clinical effects. Our results demonstrated that DAPCI-MS in combination with PCA was a feasible technique for high-throughput differentiation of various kinds of F. schisandrae. It is also possible that DAPCI-MS could become a powerful technology in the studies of traditional Chinese medicine studies and in situ analysis of Chinese herbs.

Keywords: Fructus schisandrae; Surface desorption atmospheric pressure chemical ionization mass spectrometry; Principal Component Analysis; Chemical marker


Assisted inhibition effect of acetylcholinesterase with n-octylphosphonic acid and application in high sensitive detection of organophosphorous pesticides by matrix-assisted laser desorption/ionization Fourier transform mass spectrometry by Tingting Cai; Li Zhang; Haoyang Wang; Jing Zhang; Yinlong Guo (pp. 291-296).
In the presence of n-octylphosphonic acid, the percentage of AChE inhibition caused by acephate pesticide was increased significantly. The enzyme inhibition still kept correlation with acephate concentrations. Monitoring of enzyme reaction and screening enzyme inhibitor in cowpea samples were based on MALDI-FTMS.Display Omitted► n-Octylphosphonic acid enhanced enzyme inhibition by organophosphorous pesticide. ► The detection limits were much lower than those of other enzymatic methods. ► This approach was applied in cowpea samples and confirmed by standard method.A simple and practical approach to improve the sensitivity of acetylcholinesterase (AChE)-inhibited method has been developed for monitoring organophosphorous (OP) pesticide residues. In this work, matrix-assisted laser desorption/ionization Fourier transform mass spectrometry (MALDI-FTMS) was used to detect AChE activity. Due to its good salt-tolerance and low sample consumption, MALDI-FTMS facilitates rapid and high-throughput screening of OP pesticides. Here we describe a new method to obtain low detection limits via employing external reagents. Among candidate compounds, n-octylphosphonic acid ( n-Octyl-PA) displays assistant effect to enhance AChE inhibition by OP pesticides. In presence of n-Octyl-PA, the percentages of AChE inhibition still kept correlation with OP pesticide concentrations. The detection limits were improved significantly even by 102–103 folds in comparison with conventional enzyme-inhibited methods. Different detection limits of OP pesticides with different toxicities were as low as 0.005μgL−1 for high toxic pesticides and 0.05μgL−1 for low toxic pesticides. Besides, the reliability of results from this method to analyze cowpea samples had been demonstrated by liquid-chromatography tandem mass spectrometry (LC–MS/MS). The application of this commercial available assistant agent shows great promise to detect OP compounds in complicated biological matrix and broadens the mind for high sensitivity detection of OP pesticide residues in agricultural products.

Keywords: Organophosphorus pesticide; Acetylcholinesterase; Mass spectrometry; Alkylphosphonic acid; Assistance


An evaluation of a single-step extraction chromatography separation method for Sm–Nd isotope analysis of micro-samples of silicate rocks by high-sensitivity thermal ionization mass spectrometry by Chao-Feng Li; Xian-Hua Li; Qiu-Li Li; Jing-Hui Guo; Xiang-Hui Li; Tao Liu (pp. 297-304).
Distribution curve of all eluting fractions for a BCR-2 (1–2–3.5–7mg) on LN column using HCl and HF as eluting reagent.Display Omitted► This analytical protocol affords a simple and rapid analysis for Sm and Nd isotope in minor rock samples. ► The single-step separation method exhibits satisfactory separation effect for complex silicate samples. ► Corrected143Nd/144Nd data show excellent accuracy even if the140Ce16O+/144Nd16O+ ratio reached to 0.03.A single-step separation scheme is presented for Sm–Nd radiogenic isotope system on very small samples (1–3mg) of silicate rock. This method is based on Eichrom® LN Spec chromatographic material and affords a straightforward separation of Sm–Nd from complex matrix with good purity and satisfactory blank levels, suitable for thermal ionization mass spectrometry (TIMS).This technique, characterized by high efficiency (single-step Sm–Nd separation) and high sensitivity (TIMS on NdO+ ion beam), is able to process rapidly (3–4h), with low procedure blanks (<10pg) and very small sample (1–3mg). Replicate measurements by TIMS on143Nd/144Nd ratios and Sm–Nd concentrations are presented for eleven international silicate rock reference materials, spanning a wide range of Sm–Nd contents and bulk compositions. The analytical results show a good agreement with recommended values within ±0.004% for the143Nd/144Nd isotopic ratio and ±2% for Sm–Nd quantification at the 95% confidence level. It is noted that the uncertainty of this method is about 3 times larger than typical precision achievable with two-stage full separation followed by state-of-the-art conventional TIMS using Nd+ ion beams which require much larger amounts of Nd. Hence, our single-step separation followed by NdO+ ion beam technique is preferred to the analysis for microsamples.

Keywords: LN Spec; Extraction chromatography; Sm–Nd isotopes; Thermal ionization mass spectrometry; NdO; +


Pyrolysis–gas chromatography–mass spectrometry for studying N-vinyl-2-pyrrolidone- co-vinyl acetate copolymers and their dissolution behaviour by Aleksandra Chojnacka; Abdul Ghaffar; Andrew Feilden; Kevin Treacher; Hans-Gerd Janssen; Peter Schoenmakers (pp. 305-311).
Display Omitted► SEC and Py–GC–MS for characterization of PVP–VA copolymers. ► Quantitative Py–GC–MS of copolymers to calculate monomer ratios. ► Py–GC–MS for dissolution behaviour of PVP–VA copolymers in water. ► SEC combined with Py–GC–MS to provide copolymer composition as function of molecular weight.Knowledge on the solubility behaviour and dissolution rate of speciality and commodity polymers is very important for the use of such materials in high-tech applications. We have developed methods for the quantification and characterization of dissolved copolymers of N-vinyl-2-pyrrolidone (VP) and vinyl acetate (VA) during dissolution in water. The methods are based on pyrolysis (Py) performed in a programmed-temperature vaporization injector with subsequent identification and quantification of the components in the pyrolysate using capillary gas chromatography–mass spectrometry (GC–MS). By injecting large volumes and applying cryo-focussing at the top of the column, low detection limits could be achieved.The monomer ratio was found to have the greatest effect on the dissolution rate of the PVP- co-VA copolymers. The material with the highest amount of VA (50%) dissolves significantly slower than the other grades. Size-exclusion chromatography (SEC) and Py–GC–MS were used to measure molecular weights and average chemical compositions, respectively. Combined off-line SEC//Py–GC–MS was used to determine the copolymer composition (VP/VA ratio), as a function of the molecular weight for the pure polymers. In the dissolution experiments, a constant VP/VA ratio across the dissolution curve was observed for all copolymers analysed. This suggests a random distribution of the two monomers over the molecules.

Keywords: Copolymer dissolution; Copolymer characterization; Pyrolysis–GC–MS; SEC; N; -vinyl-2-pyrrolidone; Vinyl acetate


Screening adulteration of polypropylene bottles with postconsumer recycled plastics for oral drug package by near-infrared spectroscopy by Lan-Gui Xie; Hui-Min Sun; Shao-Hong Jin (pp. 312-320).
Display Omitted► NIR was used for screening the adulteration of plastic packaging containers with postconsumer recycled plastics. ► NIR models were validated by studying the identification reliability, specificity, and robustness. ► NIR models screened the adulterated samples in the spiking level of 20% successfully. ► The universal NIR model rejected an unqualified PP bottle adulterated with recycle plastics in practice.Adulteration of pharmaceutical packaging containers with postconsumer recycled plastic materials was considerably difficult to identify due to the similar chemical compositions of virgin and recycled plastics. In the present study, near-infrared (NIR) spectroscopy coupled with conformity test was proposed to screen the adulteration of pharmaceutical packaging containers. Two kinds of representative screening models were investigated on polypropylene (PP) bottles for oral drug package. The reliability of the screening models was validated through studying the identification reliability, specificity, and robustness of the methods. The minimum spiking level of two modeled adulterants at the proportion of 20% could be detected, and the unqualified sample from a domestic manufacturer was rejected by this developed method. This strategy represents a rapid and promising analytical method for screening the adulteration of pharmaceutical plastic packaging containers with postconsumer recycled plastics.

Keywords: Conformity test; NIR spectroscopy; Medical bottle; Virgin plastic; Recycled plastic; Adulteration


Allergen diagnosis microarray with high-density immobilization capacity using diamond-like carbon-coated chips for profiling allergen-specific IgE and other immunoglobulins by Koichi Suzuki; Mineyoshi Hiyoshi; Hitomi Tada; Miwa Bando; Takao Ichioka; Norio Kamemura; Hiroshi Kido (pp. 321-327).
. To improve protein microarray sensitivity and scope of measurements, we designed the high-density DNA solidification technique of the carboxylated diamond like carbon chip for the allergen microarray technique. High-density antigen immobilization accomplished high-sensitivity with wide dynamic range and throughput antibodies (IgE, IgA, IgG, IgG1, IgG4, saliva IgA) quantification by a minimal amount (1–2μL) of sera and saliva.Display Omitted► We develop a new allergen diagnosis microarray using a diamond-like carbon (DLC) chip. ► The DLC chip shows highest density of antigen immobilization in microarrays reported. ► The DLC chip measures allergen-specific IgE, IgA, and IgG quantitatively with high sensitivity.The diagnosis of antibody-mediated allergic disorders is based on clinical findings, skin prick tests and detection of allergen-specific IgE in serum. Here, we present a new microarray technique of high-density antigen immobilization using carboxylated arms on the surface of a diamond-like carbon (DLC)-coated chip. High immobilization capacity of antigen on DLC chip at (0.94–7.82)×109moleculesmm−2 allowed the analysis of allergen-specific immunoglobulins against not only purified proteins but also natural allergen extracts with wide assay dynamic range. The higher sensitivity of the allergen-specific IgE detection on DLC chip was observed for comparison with the UniCAP system: the DLC chip allowed lowering the limit of dilution rate in UniCAP system to further dilution at 4–8-fold. High correlations ( ρ>0.9–0.85) of allergen-specific IgE values determined by the DLC chip and UniCAP were found in most of 20 different allergens tested. The DLC chip was useful to determine allergen-induced antibodies of IgA, IgG, IgG1, and IgG4 in sera, apart from IgE, as well as secretory IgA in saliva against the same series of allergens on the chip in a minimal amount (1–2μL) of sample.

Keywords: Allergen; Diamond-like carbon; Immunoassay; Microarray technology


Environmental monitoring using a conventional photographic digital camera for multianalyte disposable optical sensors by A. Lapresta-Fernández; L.F. Capitán-Vallvey (pp. 328-337).
Display Omitted► An inexpensive photographic camera with flash as analytical system is presented. ► The procedure is tested with disposable multianalyte optical sensors and pH strips. ► Analytical performance and comparison with other imaging techniques are discussed.The primary interest of this study concerns the use of an inexpensive photographic digital camera as the detection system, using its own flash as the source of light to present a new analytical procedure to measure disposable multianalyte optical sensors for potassium, magnesium, hardness and conventional pH test strips. The camera arrangement was designed in a fixed position over an optical board with controllable ambient conditions. After acquiring the digital image, the analytical information contained in each test zone is analyzed using theRGB colour space. Reflectance measurements were developed to study the colourimetric and spectral characteristics of the test zones. We obtained the following application ranges and precision in terms of relative standard deviation (RSD %): for potassium from 3.2×10−7 to 0.1M with a precision between 3.3 and 4.0%, for magnesium from 2.7×10−6 to 1.5M showing a precision between 4.7 and 7.8% and finally for hardness from 4.3×10−2 to 200,000mgL−1 CaCO3 and between 5.1 and 7.0%. Moreover, the analytical characteristics of several optical procedures were compared with the results presented here. The proposed method was statistically validated against a reference procedure using samples of water from different sources and beverages, indicating that there are no significant statistical differences at a 95% confidence level.

Keywords: Photographic digital camera; Image colour analysis; Potassium, magnesium and hardness determination; Disposable multianalyte sensor; Environmental monitoring


Oligonucleotide stabilized silver nanoclusters as fluorescence probe for drug–DNA interaction investigation by Jipei Yuan; Weiwei Guo; Erkang Wang (pp. 338-342).
In this work, oligonucleotide stabilized silver nanoclusters as novel fluorescent probes were successfully utilized for the drug–DNA interaction study. With the advantage of biocompatibility and simple synthesis procedure, Ag clusters are promising fluorescent probes in the chemical and especially biochemical sensing fields.Display Omitted► Oligonucleotide stabilized silver nanoclusters were utilized as novel fluorescent probes for drug–DNA interaction. ► The binding constants and binding site sizes of drug–DNA interactions were investigated using non-linear fit analysis. ► Sequence preference between daunorubicin and six double-stranded tetranucleotides was studied.In this work, oligonucleotide stabilized silver nanoclusters as novel fluorescent probes were successfully utilized for the drug–DNA interaction study. Silver nanoclusters were proved to be sensitive probes for the drugs investigated (including of two kinds of intercalators, daunorubicin and quinacrine, as well as a non-intercalating binder bisBenzimide H 33258), as the detection limits at 10−8molL−1 level of studied drugs can be achieved. The interactions of drugs and calf thymus DNA were investigated using non-linear fit analysis, and the binding constants as well as binding site sizes were obtained. As biocompatible materials, silver nanoclusters are promising in the chemical especially biochemical analysis fields.

Keywords: Fluorescence; Silver nanoclusters; Quenching; Drug–DNA interaction


A novel, ultra sensible biosensor built by layer-by-layer covalent attachment of a receptor for diagnosis of tumor growth by Zihni Onur Uygun; Mustafa Kemal Sezgintürk (pp. 343-348).
Display Omitted► Vascular Entothelial Growth Factor Receptor-1 was used as a biorecognition element as a first time in the literature. ► Electrochemical impedance spectroscopy, as a measurement principle was used for analysis of VEGF-R1/VEGF interaction as a first time. ► A layer-by-layer immobilization procedure enhanced the sensibility of the biosensor. ► The biosensor could detect vascular endothelial growth factor in the range of 100–600femtogrammL−1.In the presented research, a novel, ultra sensitive biosensor for the impedimetric detection of vascular endothelial growth factor (VEGF) is introduced. The human vascular endothelial growth factor receptor 1 (VEGF-R1, Flt-1) was used as a biorecognition element for the first time. The immobilization of VEGF-R1 on glassy carbon electrodes was carried out using layer-by-layer covalent attachment of VEGF-R1. The electrochemical properties of the layers constructed on the electrodes were characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The differences in electron transfer resistance ( Ret) between the working solution and the biosensor surface, recorded by the redox probe K3[Fe(CN)6]/K4[Fe(CN)6], confirmed the binding of VEGF to VEGF-R1. The new biosensor allowed a detection limit of 100fgmL−1 with a linear range of 100–600fgmL−1 to be obtained. The biosensor also exhibited good repeatability (with a correlation coefficient of 1.95%), and reproducibility.

Keywords: Tumor growth; Cancer; Vascular endothelial growth factor; Vascular endothelial growth factor receptor-1; Electrochemical impedance spectroscopy; Biosensor


Aptamer enzymatic cleavage protection assay for the gold nanoparticle-based colorimetric sensing of small molecules by Valérie Guieu; Corinne Ravelet; Sandrine Perrier; Zhenyu Zhu; Simon Cayez; Eric Peyrin (pp. 349-353).
Display Omitted► Homogeneous aptasensor designed for colorimetric detection of small molecules. ► Format relied on target-induced protection of aptamer from enzymatic digestion. ► Transduction attained through adsorption of DNA onto gold nanoparticles. ► Sensing platform successfully applied to tyrosinamide and adenosine detection.A label-free, homogeneous aptamer-based sensor strategy was designed for the facile colorimetric detection of small target molecules. The format relied on the target-induced protection of DNA aptamer from the enzymatic digestion and its transduction into a detectable signal through the length-dependent adsorption of single-stranded DNA onto unmodified gold nanoparticles (AuNPs). The proof-of-principle of the approach was established by employing the anti-tyrosinamide aptamer as a model functional nucleic acid. In the absence of target, the aptamer was cleaved by the phosphodiesterase I enzymatic probe, leading to the release of mononucleotides and short DNA fragments. These governed effective electrostatic stabilization of AuNPs so that the nanoparticles remained dispersed and red-colored upon salt addition. Upon tyrosinamide binding, the enzymatic cleavage was impeded, resulting in the protection of the aptamer structure. As this long DNA molecule was unable to electrostatically stabilize AuNPs, the resulting colloidal solution turned blue after salt addition due to the formation of nanoparticle aggregates. The quantitative determination of the target can be achieved by monitoring the ratio of absorbance at 650 and 520nm of the gold colloidal solution. A limit of detection of ∼5μM and a linear range up to 100μM were obtained. The sensing platform was further applied, through the same experimental protocol, to the adenosine detection by using its DNA aptamer as recognition tool. This strategy could extend the potentialities, in terms of both simplicity and general applicability, of the aptamer-based sensing approaches.

Keywords: Aptamer; Unmodified gold nanoparticles; Colorimetric sensing; Enzymatic cleavage protection


Antibody-based surfaces: Rapid characterization using two complementary colorimetric assays by Thomas Moreau; Clément Faye; Mickael Baqué; Isabelle Desvignes; Gaëlle Coussot; Robert Pascal; Odile Vandenabeele-Trambouze (pp. 354-360).
Display Omitted► Two sensitive colorimetric assays were developed to characterize antibody grafting. ► These methods are well adapted to pre-screening of antibody grafting performances. ► Grafting efficiency and specific activity were measured on two commercial surfaces. ► Grafting conditions were optimized in terms of pH buffer and antibody concentration.Finding a general solution for optimizing the grafting of antibody on solid surfaces is difficult due to the variety of material, grafting principles and chemistries or surface formats available (beads, microplates, fibers, etc.). Pre-screening methods able to assess grafting efficiency (GE) and specific activity (SA) are required. In this context, we present here two colorimetric assays that can be used on a wide variety of surface format, chemistry, etc. The first one, ADECA (Amino Density Estimation by Colorimetric Assay) allows a rapid estimation of grafted antibodies and allows calculating the GE. The second one, A 2 HRP (Antibody Anti-HorseRadish Peroxidase) provides a measure of the amount of active antibody, which, combined to ADECA, is used to determine the SA of grafted antibody. Analytical parameters (limit of detection, repeatability, linearity, etc.) of these two colorimetric assays are presented. Using two commercially available microplates, we demonstrated that, when used in parallel, these rapid and sensitive methods are well adapted to pre-screening of antibody grafting performances.

Keywords: Abbreviations; BSA; bovine serum albumin; CBB; Coomassie brilliant blue; ELISA; enzyme-linked immunosorbent assay; HRP; horseradish peroxidase; Ab; antibody; mAb; monoclonal antibody; PBS; phosphate buffered saline; PBST; phosphate buffered saline with Tween 20; DBA; 3,4-diaminobenzoic acid; OPD; Ortho; -phenylenediamine; IgG; immunoglobulin G; MeOH; methanol; IVel; initial velocity; InS; inhibitive solution; PAMAM; polyamidoamine; AFM; atomic force microscopy; DGL; dendrigraftof poly-; l; -lysine; EtOH; ethanol; SA; specific activity; GE; grafting efficiency; BCA; bicinchoninic acid kit; anti-FITC Ab; anti-fluorescein isothiocyanate antibodyAntibody grafting; Pre-screening method; Anti-HRP antibodies; ADECA


Determination of cholesterol and triglycerides in serum lipoproteins using flow field-flow fractionation coupled to gas chromatography–mass spectrometry by Rashid Nazir Qureshi; Erwin Kaal; Hans-Gerd Janssen; Peter J. Schoenmakers; Wim Th. Kok (pp. 361-366).
Display Omitted► Lipoproteins from human serum were separated by size (HDL, LDL, VLDL) using field flow fractionation. ► Pyrolysis-GC–MS could be used to quantify cholesterol and triglycerides in the lipoprotein fractions. ► Cholesterol and triglyceride profiles measured in different samples were very similar to results obtained with other methods. ► Possibilities for fatty acid speciation and study of the cholesterol metabolism were shown.Asymmetric flow field flow fractionation (AsFlFFF) was combined with pyrolysis-gas chromatography mass spectrometry for a sized based fractionation and a detailed compositional study of the triglycerides and cholesterol associated with the various lipoprotein subclasses present in human serum. Serum samples were injected in the AsFlFFF instrument and fractionated with a time-delayed exponential decay cross flow program. The fractions collected after AsFlFFF elution were injected into a programmable temperature vaporizer (PTV) GC-injector, containing a fritted liner. A temperature and split-flow program for the PTV injector was optimized for the thermally assisted hydrolysis and methylation of the compounds of interest. The resulting fatty acid and cholesterol methyl esters were separated by GC and characteristic fragment ions were detected by MS. The system was optimized and calibrated with triglyceride and cholesterol standards for quantitative analysis. The possible interference by phospholipids with the quantitative results was investigated and found to be of minor importance.The concentrations and lipoprotein profiles of triglycerides and cholesterol were determined in a pooled serum sample of healthy volunteers and a serum sample of a sepsis patient. The results obtained with the GC–MS approach were compared with those of a previously developed method based on AsFlFFF with a dual enzymatic reaction detection system. A good agreement of the profiles was found, for cholesterol as well as for the triglycerides, even when the GC–MS method quantifies the fatty acids while with the enzymatic reaction method the glycerol concentrations are determined. Total cholesterol and triglyceride concentration values for the serum samples showed good agreement with the results of the standard enzymatic method as used in practice in the university hospital.

Keywords: Lipoproteins; Cholesterol; Triglycerides; Asymmetric field flow fractionation; Pyrolysis-gas chromatography–mass spectrometry; Fatty acid profiling


Application of an asymmetric flow field flow fractionation multi-detector approach for metallic engineered nanoparticle characterization – Prospects and limitations demonstrated on Au nanoparticles by Harald Hagendorfer; Ralf Kaegi; Jacqueline Traber; Stijn F.L. Mertens; Roger Scherrers; Christian Ludwig; Andrea Ulrich (pp. 367-378).
Display Omitted► In this study we present a size- and element selective method, outlined to characterize metallic ENPs, and demonstrated on engineered Au-NP. ► A method for quantification of ionic- and particular fraction for nanoparticles in dispersions is presented. ► Influence of membrane materials, carrier liquid and flow parameters for A4F was studied. ► Comparison of MALLS and DLS for nanoparticle size determination was performed. ► Coupling of ICPMS to the A4F, UV/vis and light scattering apparatus is shown.In this work we discuss about the method development, applicability and limitations of an asymmetric flow field flow fractionation (A4F) system in combination with a multi-detector setup consisting of UV/vis, light scattering, and inductively coupled plasma mass spectrometry (ICPMS). The overall aim was to obtain a size dependent-, element specific-, and quantitative method appropriate for the characterization of metallic engineered nanoparticle (ENP) dispersions. Thus, systematic investigations of crucial method parameters were performed by employing well characterized Au nanoparticles (Au-NPs) as a defined model system.For good separation performance, the A4F flow-, membrane-, and carrier conditions were optimized. To obtain reliable size information, the use of laser light scattering based detectors was evaluated, where an online dynamic light scattering (DLS) detector showed good results for the investigated Au-NP up to a size of 80nm in hydrodynamic diameter. To adapt large sensitivity differences of the various detectors, as well as to guarantee long term stability and minimum contamination of the mass spectrometer a split-flow concept for coupling ICPMS was evaluated. To test for reliable quantification, the ICPMS signal response of ionic Au standards was compared to that of Au-NP. Using proper stabilization with surfactants, no difference for concentrations of 1–50μg AuL−1 in the size range from 5 to 80nm for citrate stabilized dispersions was observed. However, studies using different A4F channel membranes showed unspecific particle–membrane interaction resulting in retention time shifts and unspecific loss of nanoparticles, depending on the Au-NP system as well as membrane batch and type. Thus, reliable quantification and discrimination of ionic and particular species was performed using ICPMS in combination with ultracentrifugation instead of direct quantification with the A4F multi-detector setup.Figures of merit were obtained, by comparing the results from the multi detector approach outlined above, with results from batch-DLS and transmission electron microscopy (TEM). Furthermore, validation performed with certified NIST Au-NP showed excellent agreement. The developed methods show potential for characterization of other commonly used and important metallic engineered nanoparticles.

Keywords: Asymmetric flow field flow fractionation; Light scattering; ICPMS; Metallic engineered nanoparticles; Au nanoparticles; Particle–membrane interaction
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