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Analytica Chimica Acta (v.755, #)

Editorial Board (pp. iii).

Applications of synchrotron μ-XRF to study the distribution of biologically important elements in different environmental matrices: A review by Sanghamitra Majumdar; Jose R. Peralta-Videa; Hiram Castillo-Michel; Jie Hong; Cyren M. Rico; Jorge L. Gardea-Torresdey (pp. 1-16).

Display Omitted► μ-SXRF is a state-of-the-art technique to map biologically important elements. ► μ-SXRF allows in situ mapping of the elements at nanometer to sub-micrometer scale. ► μ-SXRF can be used in plant, soil, microbe and particulate matter samples. ► μ-SXRF is coupled with other synchrotron techniques to study chemical speciation.Environmental matrices including soils, sediments, and living organisms are reservoirs of several essential as well as non-essential elements. Accurate qualitative and quantitative information on the distribution and interaction of biologically significant elements is vital to understand the role of these elements in environmental and biological samples. Synchrotron micro-X-ray fluorescence (μ-SXRF) allows in situ mapping of biologically important elements at nanometer to sub-micrometer scale with high sensitivity, negligible sample damage and enable tuning of the incident energy as desired. Beamlines in the synchrotron facilities are rapidly increasing their analytical versatility in terms of focusing optics, detector technologies, incident energy, and sample environment. Although extremely competitive, it is now feasible to find stations offering complimentary techniques like micro-X-ray diffraction (μ-XRD) and micro-X-ray absorption spectroscopy (μ-XAS) that will allow a more complete characterization of complex matrices. This review includes the most recent literature on the emerging applications and challenges of μ-SXRF in studying the distribution of biologically important elements and manufactured nanoparticles in soils, sediments, plants, and microbes. The advantages of using μ-SXRF and complimentary techniques in contrast to conventional techniques used for the respective studies are discussed.

Keywords: Synchrotron micro-X-ray fluorescence; Biological important elements; Nanoparticles; Distribution; X-ray absorption spectroscopy

Photon level chemical classification using digital compressive detection by David S. Wilcox; Gregery T. Buzzard; Bradley J. Lucier; Ping Wang; Dor Ben-Amotz (pp. 17-27).

Display Omitted► A new digital compressive detection strategy is developed. ► Chemical classification demonstrated using as few as ∼10 photons. ► Binary filters are optimal when taking few measurements.A key bottleneck to high-speed chemical analysis, including hyperspectral imaging and monitoring of dynamic chemical processes, is the time required to collect and analyze hyperspectral data. Here we describe, both theoretically and experimentally, a means of greatly speeding up the collection of such data using a new digital compressive detection strategy. Our results demonstrate that detecting as few as ∼10 Raman scattered photons (in as little time as ∼30μs) can be sufficient to positively distinguish chemical species. This is achieved by measuring the Raman scattered light intensity transmitted through programmable binary optical filters designed to minimize the error in the chemical classification (or concentration) variables of interest. The theoretical results are implemented and validated using a digital compressive detection instrument that incorporates a 785nm diode excitation laser, digital micromirror spatial light modulator, and photon counting photodiode detector. Samples consisting of pairs of liquids with different degrees of spectral overlap (including benzene/acetone and n-heptane/n-octane) are used to illustrate how the accuracy of the present digital compressive detection method depends on the correlation coefficients of the corresponding spectra. Comparisons of measured and predicted chemical classification score plots, as well as linear and non-linear discriminant analyses, demonstrate that this digital compressive detection strategy is Poisson photon noise limited and outperforms total least squares-based compressive detection with analog filters.

Keywords: Optimal binary filters; Compressive detection; Digital micromirror device; Classification; Total least squares

Mass spectrometry fingerprinting coupled to National Institute of Standards and Technology Mass Spectral search algorithm for pattern recognition by Pablo Martínez-Lozano Sinues; Rosa M. Alonso-Salces; Lorenzo Zingaro; Alessandro Finiguerra; Margaret V. Holland; Claude Guillou; Simone Cristoni (pp. 28-36).

Display Omitted► MS fingerprinting combined with the NIST-MS search program for pattern recognition. ► NIST classifications were compared to chemometric techniques: LDA, PLS-DA, kNN, CPANN. ► NIST predicted correctly up to 96% of the geographical origin of olive oil samples. ► NIST outperforms traditional classification techniques: PLS-DA achieved 88% of hits.A new analytical strategy based on mass spectrometry fingerprinting combined with the NIST-MS search program for pattern recognition is evaluated and validated. A case study dealing with the tracing of the geographical origin of virgin olive oils (VOOs) proves the capabilities of mass spectrometry fingerprinting coupled with NIST-MS search program for classification. The volatile profiles of 220 VOOs from Liguria and other Mediterranean regions were analysed by secondary electrospray ionization-mass spectrometry (SESI-MS). MS spectra of VOOs were classified according to their origin by the freeware NIST-MS search v 2.0. The NIST classification results were compared to well-known pattern recognition techniques, such as linear discriminant analysis (LDA), partial least-squares discriminant analysis (PLS-DA), k-nearest neighbours ( kNN), and counter-propagation artificial neural networks (CP-ANN). The NIST-MS search program predicted correctly 96% of the Ligurian VOOs and 92% of the non-Ligurian ones of an external independent data set; outperforming the traditional chemometric techniques (prediction abilities in the external validation achieved by kNN were 88% and 84% for the Ligurian and non-Ligurian categories respectively). This proves that the NIST-MS search software is a useful classification tool.

Keywords: Abbreviations; VOO; virgin and extra virgin olive oils; PDO; Protected Designation of Origin; PGI; Protected Geographical Indication; TSG; Traditional Specialty Guaranteed; NMR; nuclear magnetic resonance; MS; mass spectrometry; MALDI-MS; matrix assisted laser desorption; SESI; secondary electrospray ionization; ToF-MS; time of flight mass spectrometry; PTR-MS; proton-transfer-reaction mass spectrometry; NIR; near-infrared; IR; infrared; FT; Fourier transformation; GC; gas chromatography; NIST; National Institute of Standards and Technology; ANOVA; analysis of variance; PCA; principal component analysis; PC; principal component; LDA; linear discriminant analysis; PLS-DA; partial least-squares discriminant analysis; k; NN; k; -nearest neighbours; CP-ANN; counter propagation artificial neural networks; ANN; artificial neural network; PRESS; predicted error sum of squares; RMSEP; root-mean-square error of prediction; CV; cross-validation; LOO-CV; leave-one-out cross-validationNational Institute of Standards and Technology Mass Spectral search algorithm; Mass spectrometry; Secondary electrospray ionization; Pattern recognition; Chemometrics; Olive oil

Application of parallel factor analysis to total synchronous fluorescence spectrum of dilute multifluorophoric solutions: Addressing the issue of lack of trilinearity in total synchronous fluorescence data set by Keshav Kumar; Ashok Kumar Mishra (pp. 37-45).

Display Omitted► TSF based three way array was found to lack trilinear structure. ► Practical issues in representing the TSF data in EEMF layout were studied. ► Trilinear decomposition was achieved by PARAFAC analysis on the TSF data in EEMF layout.In recent years, total synchronous fluorescence (TSF) spectroscopy has become popular for the analysis of multifluorophoric systems. Application of PARAFAC, a popular deconvolution tool, requires trilinear structure in the three-way data array. The present work shows that TSF based three-way array data set of dimension sample×wavelength×Δ λ does not have trilinear structure and hence it should not be subjected to PARAFAC analysis. This work also proposes that a TSF data set can be converted to an excitation–emission matrix fluorescence (EEMF) like data set which has trilinear structure, so that PARAFAC analysis can be performed on it. This also enables the retrieval of PARAFAC-separated component TSF spectra.

Keywords: PARAFAC; TSF spectroscopy; Synchronous fluorescence; Trilinear; Three-way array; EEMF layout

A dual-amplification aptasensor for highly sensitive detection of thrombin based on the functionalized graphene-Pd nanoparticles composites and the hemin/G-quadruplex by Shunbi Xie; Yaqin Chai; Ruo Yuan; Lijuan Bai; Yali Yuan; Yan Wang (pp. 46-53).

Display Omitted► The hemin/G-quadruplex simultaneously acts as NADH oxidase and HRP-mimicking DNAzyme. ► The PdNPs-RGs were adopted to further enhance the electrochemical signal. ► The avidin–biotin system was employed to improve the sensitivity of thrombin analysis. ► The prepared aptasensor exhibited low detection limit and wide linear range to TB.In this work, an advanced sandwich-type electrochemical aptasensor for thrombin was proposed by integrating hemin/G-quadruplex with functionalized graphene-Pd nanoparticles composites (PdNPs-RGs). The hemin/G-quadruplex formed by intercalating hemin into thrombin binding aptamer (TBA), firstly acted as a NADH oxidase, assisting the oxidation of NADH to NAD⁺ accompanying with the generation of H₂O₂ in the presence of dissolved O₂. Subsequently, the hemin/G-quadruplex acted as HRP-mimicking DNAzyme that rapidly bioelectrocatalyze the reduction of the produced H₂O₂. At the same time, the Pd nanoparticles supported on p-iodoaniline functionalized graphene were also adopted to catalyze the reduction of H₂O₂. Thus, with the dual catalysis, a dramatically amplified electrochemical signal could be obtained. Besides, the avidin–biotin system for binding aptamer sequences on electrodes not only improved the sensitivity of thrombin analysis but also obtained an acceptable repeatability of the aptasensor. With several factors mentioned above, a wide linear ranged from 0.1pM to 50nM was acquired with a relatively low detection limit of 0.03pM (defined as S/ N=3). These excellent performances provided our approach a promising way for ultrasensitive assay in electrochemical aptasensors.

Keywords: Aptasensor; Functionalized graphene; Pd nanoparticles; Thrombin; Hemin/G-quadruplex

A cation trap for anodic stripping voltammetry: NH₃–plasma treated carbon nanotubes for adsorption and detection of metal ions by Yan Wei; Ran Yang; Xing Chen; Lun Wang; Jin-Huai Liu; Xing-Jiu Huang (pp. 54-61).

NH₃–plasma treated multi-walled carbon nanotubes (pn-MWCNTs) with cation traps for the detection of ultratrace quantities of Zn(II), Cd(II), Cu(II), and Hg(II) using square wave anodic stripping voltammetry (SWASV) is described. The pn-MWCNTs use their adsorption performance during the metal ions deposition step to enhance the sensitivity of the tripping response.Display Omitted► We introduce amino groups onto the surface of multi-walled carbon nanotubes (pn-MWCNTs) using NH₃–plasma method. ► pn-MWCNTs exhibit a different ability of adsorption toward metal ions. ► pn-MWCNTs exhibit excellent performances toward heavy metal ions in a SWASV arrangement. ► Zn(II), Cd(II), Cu(II) and Hg(II) were individually detected at potentials of −1.16, −0.78, −0.268 and 0.108V, respectively. ► No interference could be seen during the simultaneous detection of Zn(II), Cd(II), Cu(II), and Hg(II).NH₃–plasma treated multi-walled carbon nanotubes (pn-MWCNTs) with cation traps for the detection of ultratrace quantities of Zn(II), Cd(II), Cu(II), and Hg(II) using square wave anodic stripping voltammetry (SWASV) is described. The pn-MWCNTs use their adsorption performance to enhance the sensitivity. It is found that under optimized conditions Zn(II), Cd(II), Cu(II) and Hg(II) were individually detected at potentials of −1.16, −0.78, −0.268 and 0.108V, respectively. The detection limit (3σ method) of 0.314, 0.0272, 0.2263, and 0.1439nM toward Zn(II), Cd(II), Cu(II), and Hg(II) is achievable, respectively. No interference could be seen during the simultaneous detection of Zn(II), Cd(II), Cu(II), and Hg(II). The pn-MWCNTs exhibit excellent selectivity owing to the different ability of adsorption. A study of the ability of pn-MWCNTs in practical application is carried out using a sample of water collected from Dongpu Reservoir in Hefei City, Anhui, China. It is found that the results were favorable when compared against inductively coupled plasma atomic emission spectrometry (ICP-AES) analysis.

Keywords: Carbon nanotubes; NH; ₃; –plasma treatment; Surface modification; Adsorption and electrochemical detection; Metal ions

Enzyme-catalyzed silver deposition on irregular-shaped gold nanoparticles for electrochemical immunoassay of alpha-fetoprotein by Wenqiang Lai; Dianping Tang; Xiaohua Que; Junyang Zhuang; Libing Fu; Guonan Chen (pp. 62-68).

Display Omitted► We report a new sandwich-type electrochemical immunoassay of biomarkers. ► Enzyme-catalyzed silver deposition. ► Irregular-shaped gold nanoparticles. ► Nanosilver molecular tags.A new and disposable electrochemical immunosensor was designed for detection of alpha-fetoprotein (AFP), as a model analyte, with sensitivity enhancement based on enzyme-catalyzed silver deposition onto irregular-shaped gold nanoparticles (ISGNPs). The assay was carried out with a sandwich-type immunoassay protocol by using ISGNP-labeled anti-AFP antibodies conjugated with alkaline phosphatase (ALP–Ab₂) as detection antibodies. The enzymatically catalytic deposition of silver on the electrode could be measured by stripping analysis in KCl solution due to the Ag/AgCl solid-state voltammetric process. Several labeling protocols including spherical gold nanoparticle-labeled ALP–Ab₂ and ISGNP-labeled ALP–Ab₂ were investigated for determination of AFP, and improved analytical properties were achieved with the ISGNP labeling. With the ISGNP labeling method, the effects of incubation time and incubation temperature for antigen-antibody reaction, and deposition time of silver on the current responses of the electrochemical immunosensors were also monitored. Under optimal conditions, the electrochemical immunosensor exhibited a wide dynamic range from 0.01ngmL⁻¹ to 200ngmL⁻¹ with a detection limit of 5.0pgmL⁻¹ AFP. The immunosensor displayed a good stability and acceptable reproducibility and accuracy. No significant differences at the 95% confidence level were encountered in the analysis of 10 clinical serum samples between the developed immunoassay and the commercially available electrochemiluminescent method for determination of AFP.

Keywords: Electrochemical immunosensor; Enzyme-catalyzed silver deposition; Irregular-shaped gold nanoparticles; Alpha-fetoprotein

Development of an analytical methodology for the determination of the antiparasitic drug toltrazuril and its two metabolites in surface water, soil and animal manure by Jesper Olsen; Erland Björklund; Kristine A. Krogh; Martin Hansen (pp. 69-76).

This paper presents the development, optimization and validation of a LC–MS/MS methodology to determine the antiparasitic veterinary drug toltrazuril and its two main metabolites, toltrazuril sulfoxide and toltrazuril sulfone, in environmental surface water, soil and animal manure. Using solid phase extraction and selective pressurized liquid extraction with integrated clean-up, the analytical method allows for the determination of these compounds down to 0.06–0.13ngL⁻¹ in water, 0.01–0.03ngg⁻¹dw in soil and 0.22–0.51ngg⁻¹dw in manure. The deuterated analog of toltrazuril was used as internal standard, and ensured method accuracy in the range 96–123% for water and 77–110% for soil samples. The developed method can also be applied to simultaneously determine steroid hormones in the solid samples. The antiparasitic drug and its metabolites were found in manure and soil up to 114 and 335pgg⁻¹dw, respectively. Little is known regarding the environmental fate and effects of these compounds; consequently more research is urgently needed.Display Omitted► A LC–MS/MS methodology was developed for toltrazuril and its two metabolites. ► Selective pressurized liquid extraction with integrated clean-up. ► The antiparasitic drug and its metabolites were found in manure and soil. ► Little is known regarding the environmental fate and effects of these compounds.This paper presents the development, optimization and validation of a LC–MS/MS methodology to determine the antiparasitic veterinary drug toltrazuril and its two main metabolites, toltrazuril sulfoxide and toltrazuril sulfone, in environmental surface water, soil and animal manure. Using solid phase extraction and selective pressurized liquid extraction with integrated clean-up, the analytical method allows for the determination of these compounds down to 0.06–0.13ngL⁻¹ in water, 0.01–0.03ngg⁻¹dw in soil and 0.22–0.51ngg⁻¹dw in manure. The deuterated analog of toltrazuril was used as internal standard, and ensured method accuracy in the range 96–123% for water and 77–110% for soil samples. The developed method can also be applied to simultaneously determine steroid hormones in the solid samples. The antiparasitic drug and its metabolites were found in manure and soil up to 114 and 335pgg⁻¹dw, respectively. Little is known regarding the environmental fate and effects of these compounds; consequently more research is urgently needed.

Keywords: Manure; Soil; Water; Toltrazuril; Antiparasitic; Metabolites

Revisiting extraction of bioactive apocarotenoids from Crocus sativus L. dry stigmas (saffron) by Anastasia Kyriakoudi; Andreas Chrysanthou; Fani Mantzouridou; Maria Z. Tsimidou (pp. 77-85).

Display Omitted► We attempted to optimize the simultaneous recovery of crocins and picrocrocin. ► We employed ultrasounds to assist extraction and reduce time needed. ► We propose aqueous methanol to assist cell lysis and easier release of crocins. ► We employed response surface methodology to systematically investigate the effect of different variables.An ultrasound assisted extraction method is proposed for the recovery of bioactive glycosides ( i.e. crocins and picrocrocin) from Crocus sativus L. dry stigmas using aqueous methanol. Response surface methodology (RSM) was employed to optimize the extraction parameters, namely, the percentage of methanol (%), the duration (min) and the duty cycles (s) of sonication. Optical microscopy, spectrophotometry and RP-HPLC-DAD were employed to follow pros and cons of the process. Additional experiments were conducted to compare recoveries with those under other agitation conditions ( e.g. magnetic stirring according to ISO 3632-2 standard). The percentage of methanol, the sonication duration and duty cycles combination that can be recommended as optimum for the recovery of crocins and picrocrocin were 50%, 30min, 0.2s and 0.44%, 30min, 0.6s, respectively. Picrocrocin levels were not influenced dramatically under the optimum conditions for crocins extraction (11±2 instead of 12±1mgkg⁻¹ dry stigmas, respectively) so that these can be considered optimum for both categories of tested compounds. Ultrasound assisted extraction speeded up further recovery of these precious apocarotenoids. Our findings for extraction conditions are useful for both industrial and analytical applications and should be considered in a forthcoming revision of the ISO 3632-2 technical standard.

Keywords: Abbreviation; RP-HPLC-DAD; reversed phase high performance liquid chromatography-diode array detectionSaffron; Bioactive apocarotenoids; Crocins; Picrocrocin; Ultrasound assisted extraction; Response surface methodology

Measuring the molecular second hyperpolarizability in absorptive solutions by the third harmonic generation ratio technique by Danielle Tokarz; Richard Cisek; Nicole Prent; Ulrich Fekl; Virginijus Barzda (pp. 86-92).

Display Omitted► Second hyperpolarizability ( γ) measured with THG ratio technique. ► γ determination with concentrations as low as μM have been achieved. ► Refractive indices are measured with a home-built UV-near IR tunable refractometer. ► Measured carotenoids have positive γ values and chlorophylls negative γ values. ► Opposite signs of γ lead to interesting implications for photosynthetic complexes.Measurement of the second hyperpolarizability ( γ) values of compounds can provide insight into the molecular structural requirements for enhancement of third harmonic generation (THG) signal. A convenient method for measuring the γ of compounds in solutions was developed by implementing the THG ratio method which is based on measuring the THG intensity from two interfaces using a nonlinear optical microscope while accounting for the refractive index of solutions at the fundamental and third harmonic wavelengths. We demonstrated that the difference in refractive index at both wavelengths strongly influenced the calculation of γ values when compounds have absorption near the third harmonic or fundamental wavelength. To this end, a refractometer with the wavelength tuning range from UV to near IR was constructed, and the measured refractive indices were used to extract the γ values. The γ values of carotenoids and chlorophylls found in photosynthetic pigment–protein complexes were explored. Large differences in the refractive index at third harmonic and fundamental wavelengths for chlorophylls result in γ values that are more than two orders of magnitude larger than γ values for carotenoids as well as the sign of chlorophylls’ γ values is negative while carotenoids have positive γ values.

Keywords: Third harmonic generation; Second hyperpolarizability; Harmonophore; Refractometer; Carotenoid; Chlorophyll

Liquid chromatographic determination of microcystins in water samples following pre-column excimer fluorescence derivatization with 4-(1-pyrene)butanoic acid hydrazide by Tadashi Hayama; Kenji Katoh; Takayoshi Aoki; Miki Itoyama; Kenichiro Todoroki; Hideyuki Yoshida; Masatoshi Yamaguchi; Hitoshi Nohta (pp. 93-99).

Display Omitted► We have developed a novel method for LC determination of microcystins (MCs). ► MCs were successfully derivatized with 4-(1-pyrene)butanoic acid hydrazide. ► The derivatives could be specifically detected at excimer fluorescence wavelength. ► The SPE method was used as pretreatment of MCs in environmental water samples. ► This method can be used for evaluating MC contamination in water samples.A method to measure the concentrations of microcystins (MCs) in water samples has been developed by incorporating pre-column fluorescence derivatization and liquid chromatography (LC). A solid-phase extraction for pretreatment was used to extract the MCs in water samples. The MCs were derivatized with excimer-forming 4-(1-pyrene)butanoic acid hydrazide (PBH). The MCs could then be detected by fluorescence after separation with a pentafluorophenyl (PFP)-modified superficially porous (core shell) particle LC column. The derivatization reactions of MCs with PBH proceeded easily in the presence of 4,6-dimethoxy-1,3,5-triazin-2-yl-4-methylmorpholinium (DMT-MM) as a condensation reagent, and the resulting derivatives could be easily separated on the PFP column. The derivatives were selectively detected at excimer fluorescence wavelengths (440–540nm). The instrument detection limit and the instrument quantification limit of the MCs standards were 0.4–1.2μgL⁻¹ and 1.4–3.9μgL⁻¹, respectively. The method was validated at 0.1 and 1.0μgL⁻¹ levels in tap and pond water samples, and the recovery of MCs was between 67 and 101% with a relative standard deviation of 11%. The proposed method can be used to quantify trace amounts of MCs in water samples.

Keywords: Microcystins; Excimer fluorescence derivatization; Liquid chromatography; Environmental water sample

Modification of polypyrrole nanowires array with platinum nanoparticles and glucose oxidase for fabrication of a novel glucose biosensor by Guangqing Xu; Samuel B. Adeloju; Yucheng Wu; Xinyi Zhang (pp. 100-107).

Display Omitted► Fabrication of well aligned PPyNWA of 20nm diameter within AAO template. ► Improvement of electrochemical properties by decoration with PtNPs. ► Sensitive amperometric and potentiometric detection of glucose by adsorption of GOx on PPyNWA–PtNPs. ► Detection of as little as 5.6μM glucose with potentiometric detection. ► Comparable or better detection limit and sensitivity than some glucose biosensors fabricated with nanomaterials.A novel glucose biosensor, based on the modification of well-aligned polypyrrole nanowires array (PPyNWA) with Pt nanoparticles (PtNPs) and subsequent surface adsorption of glucose oxidase (GOx), is described. The distinct differences in the electrochemical properties of PPyNWA–GOx, PPyNWA–PtNPs, and PPyNWA–PtNPs–GOx electrodes were revealed by cyclic voltammetry. In particular, the results obtained for PPyNWA–PtNPs–GOx biosensor showed evidence of direct electron transfer due mainly to modification with PtNPs. Optimum fabrication of the PPyNWA–PtNPs–GOx biosensor for both potentiometric and amperometric detection of glucose were achieved with 0.2M pyrrole, applied current density of 0.1mAcm⁻², polymerization time of 600s, cyclic deposition of PtNPs from −200mV to 200mV, scan rate of 50mVs⁻¹, and 20 cycles. A sensitivity of 40.5mV/decade and a linear range of 10μM to 1000μM ( R²=0.9936) were achieved for potentiometric detection, while for amperometric detection a sensitivity of 34.7μAcm⁻²mM⁻¹ at an applied potential of 700mV and a linear range of 0.1–9mM ( R²=0.9977) were achieved. In terms of achievable detection limit, potentiometric detection achieved 5.6μM of glucose, while amperometric detection achieved 27.7μM.

Keywords: PPy nanowires; Pt nanoparticles; Biosensor; Electrochemical detection; Glucose

Sensitive and simultaneous detection of different disease markers using multiplexed gold nanorods by Haowen Huang; Fang Liu; Shaowen Huang; Shishan Yuan; Bo Liao; Shoujun Yi; Yunlong Zeng; Paul K. Chu (pp. 108-114).

Display Omitted► A rapid and sensitive multiplex bioassay based on gold nanorods has been developed. ► This bioanalytical assay can simultaneously detect different acceptor–ligand pairs in a wide detection wavelength range. ► This assay allows easy detection of human serum specimens infected by different diseases without sample pretreatment.A multiplexed bioanalytical assay is produced by incorporating two types of gold nanorods (GNRs). Besides retaining the desirable features of common GNRs LSPR sensors, this sensor is easy to fabricate and requires only a visible–NIR spectrometer for detection. This assay can simultaneously detect different acceptor–ligand pairs by choosing the proper GNRs possessing various LPWs in a wide detection wavelength range and can be developed into a high-throughput detection method. This bioanalytical assay allows easy detection of human serum specimens infected by S. japonicum and tuberculosis (TB) from human serum specimens (human serum/Tris–HCl buffer ratio=1:10⁴) without the need for sample pretreatment. The technique is very sensitive compared to other standard methods such as indirect hemagglutination assays (IHA) that require a serum concentration ratio of larger than 1:20 and enzyme-linked immunosorbent assays (ELISA) requiring a ratio larger than 1:100. This methodology can be readily extended to other immunoassays to realize wider diagnostic applications.

Keywords: Multiplex bioanalytical assay; Gold nanorod; Schistosoma japonicum; Tuberculosis

Separation of carboxylic acids in human serum by isotachophoresis using a commercial field-deployable analytical platform combined with in-house glass microfluidic chips by Petr Smejkal; Michael C. Breadmore; Rosanne M. Guijt; Jakub Grym; František Foret; Fritz Bek; Mirek Macka (pp. 115-120).

Display Omitted► A glass ITP microfluidic chip was designed for analysis of lactate in human serum. ► ITP chip was compatible with a field-deployable commercial platform. ► LIF/LEDIF indirect fluorescence detection was used. ► Lack of research-flexible commercial microfluidic separation platform is addressed.Portable and field deployable analytical instruments are attractive in many fields including medical diagnostics, where point of care and on-site diagnostics systems capable of providing rapid quantitative results have the potential to vastly improve the productivity and the quality of medical care. Isotachophoresis (ITP) is a well known electrophoretic separation technique previously demonstrated as suitable for miniaturization in microfluidic chip format (chip-ITP). In this work, a purpose-designed ITP chip compatible with a commercial end-used targeted microfluidic system was used to study different injection protocols and to evaluate the effect of the length of the separation channel on the analytical performance. The in-house ITP chips were made from Corning glass and compared to the commercial DNA chip for the ITP separation of anions from the hydrodynamic injection of human serum. Using the in-house ITP chip the isotachophoretic step of lactate from human serum was approximately two times longer. The results of this research suggested that microfluidic ITP with indirect fluorescence detection is a viable technique for separation of organic acids in human serum samples, especially when a chip with suitable design is used.

Keywords: Abbreviations; R6G; rhodamine 6G; PVP; polyvinilpyrolidone; LE; leading electrolyte; TE; terminating electrolyteIsotachophoresis; Microfluidic chip; Fluorescence; Indirect detection; Carboxylic acids; Serum

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Analytica Chimica Acta (v.755, #)