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Analytica Chimica Acta (v.707, #1-2)
Tuned galvanostatic polarization of solid-state lead-selective electrodes for lowering of the detection limit by Grzegorz Lisak; Tomasz Sokalski; Johan Bobacka; Leo Harju; Konstantin Mikhelson; Andrzej Lewenstam (pp. 1-6).
Display Omitted► We use lead (II) sensitive ion-selective electrode with solid-state membrane. ► We apply electrical current to enhance the electrode measuring range with a linear response. ► The current applied allows to hinder parasitic release of Pb(II) ions from the ion-selective membrane. ► The procedure proposed allows to measure ultra-low concentrations of lead ion.Lowering of the detection limit of solid-state lead-selective electrodes was achieved by using the tuned galvanostatic polarization method. A Nernstian response was obtained down to nanomolar concentrations (low detection limit 10−9moldm−3Pb2+). Good repeatability of the calibration curves was achieved by using a well established measuring procedure. Relatively high cathodic current densities were applied to the solid-state membrane in order to shorten the measurement time. Successful determination of lead in a synthetic sample (pPb2+=7.97±0.08) was achieved by introducing an analytical protocol and favourably compared to inductively coupled plasma mass spectrometry (pPb=7.93). By applying this method, a significant improvement in the detection limit of solid-state lead-selective electrodes was attained.
Keywords: Ion-selective electrode; Solid-state membrane; Low detection limit; Direct measurement of lead (II)
Peroxidase-mimicking DNAzymes for biosensing applications: A review by Joanna Kosman; Bernard Juskowiak (pp. 7-17).
Display Omitted► This review presents fundamentals concerning DNAzymes with peroxidase-like activity. ► Their design, properties and spectral characteristics are described. ► Contribution to bioanalytical research is shown by presenting examples of applications. ► They include nucleic acid probes for detection of specific DNA sequences. ► Determinations of metal cations, small molecules and proteins are also reported.DNAzymes are single stranded DNA molecules that exhibit catalytic activity and are exploited in medicine, biology and material sciences. Development in this area is related to the many advantages of DNAzymes over conventional protein enzymes, such as thermal stability and simpler preparation. DNAzymes with peroxidase-like activity have recently attracted great interest. To assure such catalytic activity, oligonucleotides have to adopt a G-quadruplex structure, which can bind the hemin molecule. This system facilitates a redox reaction between the target molecule and hydrogen peroxide, which results in the appearance of an oxidized target molecule (product).DNAzymes with peroxidase-mimicking activity have great potential in bioanalytical chemistry. This review presents fundamentals concerning the design and engineering of DNAzymes with peroxidase-like activity, describes their properties and spectral characteristics and shows how DNAzymes can contribute to bioanalytical research. Examples of bioanalytical applications of DNAzymes with peroxidase-like activity include nucleic acid probes with DNAzyme labels for the detection of specific DNA sequences in colorimetric or chemiluminescent assays. Assays for telomerase or methyltransferase activity, which are potential targets in anticancer therapy, are also described in this review. Other applications include the determination of metal cations such as Ag+, K+, Hg2+, Pb2+ or Cu2+ and amplified detection of small molecules such as adenosine, cocaine or AMP and proteins such as lysozyme or thrombin. In the last decade, DNAzymes have become part of numerous applications in many areas of science from chemistry to biology to medicine.
Keywords: Aptasensors; Bioassays; DNAzyme; G-quadruplex; Hybridization probes; Peroxidase activity
Chromatographic and spectroscopic analysis of heavy crude oil mixtures with emphasis in nuclear magnetic resonance spectroscopy: A review by Sandra L. Silva; Artur M.S. Silva; Jorge C. Ribeiro; Fernando G. Martins; Francisco A. Da Silva; Carlos M. Silva (pp. 18-37).
The chromatographic and spectroscopic techniques used to characterize heavy crude oils, although more focused in the nuclear magnetic resonance spectroscopy as the technique of choice, due to its capability to provide great information on the chemical nature of individual types of proton and carbon atoms in different and complex mixtures of crude oils are described. This review is based on 65 references and describes in a critical and interpretative ways the advantages of the NMR spectroscopy as a main technique to be used in crude oil refining industries that want to characterize crude oil fractions and the obtained refined products.Display Omitted► Chromatogrfaphic and spectroscopic techniques used to characterize heavy crude oils have been reviewed. ► This review describes in a critical and interpretative ways the advantages of the NMR spectroscopy as a main technique to be used in crude oil refining industries. ► The progress in the interpretation of the NMR spectra and of different multivariate data analyses and their potential in the identification and characterization of hydrocarbons and their physical and chemical properties have also been reviewed.The state of the art in the characterization of heavy crude oil mixtures is presented. This characterization can be done by different techniques, such as gas chromatography (GC), high performance liquid chromatography (HPLC), thin layer chromatography (TLC), infrared spectroscopy (IR), Raman spectroscopy, nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS). Nuclear magnetic resonance spectroscopy is the technique of choice due to its capability to provide information on the chemical nature of individual types of hydrogen and carbon atoms in different and complex mixtures of crude oils. The progress made in the interpretation of the NMR spectra with the development of new NMR techniques and different multivariate data analyses could give relevant information about the identification and characterization of hydrocarbons and their physical and chemical properties. These progresses can improve the refining industries operation as a result of the better knowledge on the crude composition that is fed in the refining process, as well as in the prediction of better operating conditions to obtain refined products with desired specifications and in quantities desirable to meet the market demands. The improvement in the refining operation conditions is reflected in economical benefits.
Keywords: Crude oil; Chromatographic techniques; Spectroscopic techniques; 1D and 2D NMR techniques; Multivariate data analysis; Asphaltenes
D-optimal designs and N-way techniques to determine sulfathiazole in milk by molecular fluorescence spectroscopy by Rocío Morales; M. Cruz Ortiz; Luis A. Sarabia; M. Sagrario Sánchez (pp. 38-46).
Display Omitted► Fluorescence spectroscopy is used to determine sulfathiazole in milk. ► Optimization of the procedure is made by coupling a D-optimal design and PARAFAC. ► A neural network showed to be useful to calibrate with fluorescence emission spectra. ► Performance characteristics of the method are evaluated according to 2002/657/EC Decision. ► Detection capability is 106.5μgL−1 (MRL=100) for 5% false noncompliance and compliance.The present work proposes an analytical procedure to determine sulfathiazole in milk by using molecular fluorescence spectroscopy. For this sulfonamide the European Union in Regulation 37/2010 has established a maximum residue limit in milk of 100μgkg−1.The study includes the effect of six factors on the recovery of sulfathiazole. The factors are: (i) The one related to the matrix depending on the heat treatment of the milk (UHT, pasteurized); (ii) Those related to the protein precipitation step, namely the ratio between the volume of trichloroacetic acid (TCA) and milk, centrifugation speed and temperature; (iii) Those affecting the derivatization reaction: derivatization time and volume of fluorescamine.To do this, two chemometric tools are used together: a D-optimal design for studying the effect of the factors on the recovery of sulfathiazole, considerably reducing the number of needed experiments; and the second-order property of the PARAFAC (Parallel Factor Analysis) decomposition that avoids the need of fitting a new calibration model each time that the experimental conditions change.It has been found that the type of milk, the TCA:milk ratio and the volume of fluorescamine have significant effect on the response. The rest of factors and interactions are not significant. The best recovery is obtained with UHT milk, 4:6 rate for TCA:milk volumes and 40μL of fluorescamine. In UHT milk, the mean recovery ( n=5) in the optimal conditions is 88.7% (RSD=12.4%).As some non-linear behaviour may occur when using fluorescence spectroscopy, the calibration model that relates the fluorescence spectra with the concentration is computed by a partial least squares regression and a multi-layer feed-forward neural network. In both cases, the proposed procedures have been validated according to Decision 2002/657/EC, concluding that the two are accurate although the calibration model built with the neural network has better figures of merit, the decision limit (CC α) for x0=100μgL−1 is 103.3μgL−1 and the detection capability (CC β) is 106.5μgL−1, with the probabilities of false noncompliance ( α) and false compliance ( β) equal to 5%.
Keywords: PARAFAC; D-optimal design; Sulfathiazole; Milk; Fluorescence spectroscopy; Neural networks
In-line monitoring of alcohol precipitation by near-infrared spectroscopy in conjunction with multivariate batch modeling by Hongxia Huang; Haibin Qu (pp. 47-56).
Batch score control charts ( t1) based on six NOC batches with control limits (±3 SD) dyed solid black line, and average trace marked by dotted black line: (a) batch 7, (b) batch 8, (c) batch 9, (d) batch 10.Display Omitted► NIRS combined with MSPC was proposed for in-line monitoring of alcohol precipitation. ► MSPC control limits were established to detect and diagnose batch-to-batch variation. ► The method has proven to be a feasible PAT tool for monitoring batch evolution.Alcohol precipitation is a critical unit operation during the manufacture of Chinese herbal injections. To facilitate enhanced process understanding and develop control strategy, the use of near-infrared spectroscopy (NIRS) combined with multivariate statistical process control (MSPC) methodology was investigated for in-line monitoring of alcohol precipitation. The effectiveness of the proposed approach was evaluated through an experimental campaign. Six batches were run under normal operating conditions to study batch-to-batch variation or batch reproducibility and establish MSPC control limits, while artificial process variations were purposefully introduced into the four test batches to assess the capability of the model for real-time fault detection. Several MSPC tools were compared and assessed. NIRS, in conjunction with MSPC, has proven to be a feasible process analytical technology (PAT) tool for monitoring batch evolution and potentially facilitating model-based advanced process control of the alcohol precipitation during the manufacture of Chinese herbal injections.
Keywords: Batch-to-batch reproducibility; Chinese herbal injection; Alcohol precipitation; Multivariate statistical process control; Multivariate data analysis; Near-infrared spectroscopy
Determination of copper(II) in the dairy product by an electrochemical sensor based on click chemistry by Suyan Qiu; Lidan Xie; Sen Gao; Qida Liu; Zhenyu Lin; Bin Qiu; Guonan Chen (pp. 57-61).
Display Omitted► Propargyl-functionalized Fc can be covalently coupled on the electrode surface via CuAAC reaction. ► Catalyst of Cu(I) is derived from the electrochemical reduction of Cu(II) via bulk electrolysis. ► propargyl-functionalized Fc modified electrode allows a good and stable electrochemical signal. ► The proposed sensor has high sensitivity and good selectivity for detection of Cu(II).Herein, a novel sensitive electrochemical sensor for copper(II) based on Cu(I) catalyzed alkyne–azide cycloaddition reaction (CuAAC) is described. The catalyst of Cu(I) species is derived from electrochemical reduction of Cu(II) through bulk electrolysis (BE) with coulometry technique. The propargyl-functionalized ferrocene (propargyl-functionalized Fc) is covalently coupled onto the electrode surface via CuAAC reaction and forms propargyl-functionalized Fc modified gold electrode, which allows a good and stable electrochemical signal. The change of current at peak ( dI), detected by differential pulse voltammetry (DPV), exhibits a linear response to the logarithm of Cu(II) concentration in the range of 1.0×10−14–1.0×10−9molL−1. It is also found that the proposed sensor has a good selectivity for copper(II) assay even in the presence of other common metal ions. Additionally, the proposed method has been applied to determine copper(II) in the dairy product (yoghurt) with satisfactory results.
Keywords: Click chemistry; Cu(I) catalyzed alkyne–azide cycloaddition reaction; CuAAC reaction; Electrochemical reduction; Dairy product
Nanostructured conducting molecularly imprinted polymer for selective extraction of salicylate from urine and serum samples by electrochemically controlled solid-phase micro-extraction by Akram Ameli; Naader Alizadeh (pp. 62-68).
Display Omitted► Overoxidized polypyrrole templated with salicylate has been utilized as conducting molecular imprinted polymer for EC-SPME. ► This first study reported on conducting molecular imprinted polymer was used to EC-SPME of salicylate. ► Proposed method, is particularly effective in sample clean-up and selective monitoring of salicylate in physiological samples.Overoxidized polypyrrole (OPPy) films templated with salicylate (SA) have been utilized as conducting molecular imprinted polymers (CMIPs) for potential-induced selective solid-phase micro-extraction processes. Various important fabrication factors for controlling the performance of the OPPy films have been investigated using fluorescence spectrometry. Several key parameters such as applied potential for uptake, release, pH of uptake and release solution were varied to achieve the optimum micro-extraction procedure. The film template with SA exhibited excellent selectivity over some interference. The calibration graphs were linear in the ranges of 5×10−8 to 5×10−4 and 1.2×10−6 to 5×10−4molmL−1 and the detection limit was 4×10−8molL−1. The OPPy film as the solid-phase micro-extraction absorbent has been applied for the selective clean-up and quantification of trace amounts of SA from physiological samples. The results of scanning electron microscopy (SEM) have confirmed the nano-structure morphologies of the films.
Keywords: Polypyrrole; Conducting polymer; Molecularly imprinted polymer; Salicylic acid; Solid-phase micro-extraction; Fluorescence
Ionic liquids based microwave-assisted extraction of lichen compounds with quantitative spectrophotodensitometry analysis by Sarah Bonny; Ludovic Paquin; Daniel Carrié; Joël Boustie; Sophie Tomasi (pp. 69-75).
Various lichen compounds were isolated with imidazolium derived ILs using microwave-assisted extraction or heat-extraction.Display Omitted► IL-MAE and IL-HE of various crustose lichens were performed using various imidazolium derived ionic liquids. ► Sulfate-based ILs [C1mim][MSO4] and [C2mim][ESO4] presented the best extraction efficiency of lichen compounds. ► Important reduction of extraction time (5min versus 2h) was performed using MAE in comparison with HE.Ionic liquids based extraction method has been applied to the effective extraction of norstictic acid, a common depsidone isolated from Pertusaria pseudocorallina, a crustose lichen. Five 1-alkyl-3-methylimidazolium ionic liquids (ILs) differing in composition of alkyl chain and anion were investigated for extraction efficiency. The extraction amount of norstictic acid was determined after recovery on HPTLC with a spectrophotodensitometer. The proposed approaches (IL-MAE and IL-heat extraction (IL-HE)) have been evaluated in comparison with usual solvents such as tetrahydrofuran in heat-reflux extraction and microwave-assisted extraction (MAE). The results indicated that both the characteristics of the alkyl chain and anion influenced the extraction of polyphenolic compounds. The sulfate-based ILs [C1mim][MSO4] and [C2mim][ESO4] presented the best extraction efficiency of norstictic acid. The reduction of the extraction times between HE and MAE (2h–5min) and a non-negligible ratio of norstictic acid in total extract (28%) supports the suitability of the proposed method. This approach was successfully applied to obtain additional compounds from other crustose lichens ( Pertusaria amara and Ochrolechia parella).
Keywords: Pertusaria pseudocorallina; Lichens, Polyphenolic compounds; Ionic liquids; Microwave-assisted extraction (MAE); Heat-extraction (HE)
A high-throughput platform for low-volume high-temperature/pressure sealed vessel solvent extractions by Markus Damm; C. Oliver Kappe (pp. 76-83).
.Display Omitted► Parallel low-volume coffee extractions in sealed-vessel HPLC/GC vials. ► Extractions are performed at high temperatures and pressures (200°C/20bar). ► Rapid caffeine determination from the liquid phase. ► Headspace analysis of volatiles using solid-phase microextraction (SPME).A high-throughput platform for performing parallel solvent extractions in sealed HPLC/GC vials inside a microwave reactor is described. The system consist of a strongly microwave-absorbing silicon carbide plate with 20 cylindrical wells of appropriate dimensions to be fitted with standard HPLC/GC autosampler vials serving as extraction vessels. Due to the possibility of heating up to four heating platforms simultaneously (80 vials), efficient parallel analytical-scale solvent extractions can be performed using volumes of 0.5–1.5mL at a maximum temperature/pressure limit of 200°C/20bar. Since the extraction and subsequent analysis by either gas chromatography or liquid chromatography coupled with mass detection (GC–MS or LC–MS) is performed directly from the autosampler vial, errors caused by sample transfer can be minimized. The platform was evaluated for the extraction and quantification of caffeine from commercial coffee powders assessing different solvent types, extraction temperatures and times. For example, 141±11μg caffeine (5mg coffee powder) were extracted during a single extraction cycle using methanol as extraction solvent, whereas only 90±11 were obtained performing the extraction in methylene chloride, applying the same reaction conditions (90°C, 10min). In multiple extraction experiments a total of ∼150μg caffeine was extracted from 5mg commercial coffee powder. In addition to the quantitative caffeine determination, a comparative qualitative analysis of the liquid phase coffee extracts and the headspace volatiles was performed, placing special emphasis on headspace analysis using solid-phase microextraction (SPME) techniques. The miniaturized parallel extraction technique introduced herein allows solvent extractions to be performed at significantly expanded temperature/pressure limits and shortened extraction times, using standard HPLC autosampler vials as reaction vessels. Remarkable differences regarding peak pattern and main peaks were observed when low-temperature extraction (60°C) and high-temperature extraction (160°C) are compared prior to headspace-SPME-GC–MS performed in the same HPLC/GC vials.
Keywords: Caffeine quantification; Headspace-SPME analysis; Low-volume extraction; Microtiter plates; Microwave effects; Commercial coffee powders; Microwave-assisted solvent extraction
Simplified and rapid determination of polychlorinated biphenyls, polybrominated diphenyl ethers, and polycyclic aromatic hydrocarbons in fish and shrimps integrated into a single method by Kamila Kalachova; Jana Pulkrabova; Lucie Drabova; Tomas Cajka; Vladimir Kocourek; Jana Hajslova (pp. 84-91).
Display Omitted► We developed a new sample preparation method for PCBs, PBDEs and PAHs analysis in fish and shrimps. ► Ethyl acetate-based extraction followed by silica minicolumn clean-up was used. ► DART–TOFMS was shown to be an effective tool for the fat control. ► GC–TOFMS enables simultaneous determination of all target analytes and potential non-target screening.In this study, a new rapid and flexible method for the simultaneous determination of 18 key representatives of polychlorinated biphenyls (PCBs), 7 polybrominated diphenyl ethers (PBDEs), and 32 polycyclic aromatic hydrocarbons (PAHs) in fish and shrimps by gas chromatography coupled to mass spectrometry (GC–MS) was developed and validated. A substantial simplification of sample processing prior to quantification step was achieved: after addition of water to homogenized sample, transfer of hydrophobic analytes into ethyl acetate was supported by added inorganic salts. Bulk fat, contained in crude organic extract obtained by partition, was subsequently removed on a silica minicolumn. This approach enabled to process six samples in less than 1h; moreover, the volume of an extraction solvent and consumption of other chemicals can be significantly reduced compared to, e.g., traditional Soxhlet extraction followed by gel permeation chromatography. The recoveries of target analytes were in the range of 73–120% even at the lowest spiking level (1μgkg−1), repeatabilities (relative standard deviations, RSDs) ranged from 1 to 20%. Under optimized GC–MS conditions (time-of-flight mass analyzer, TOF), the limits of quantification (LOQs) were as follows: PCBs 0.1–0.5μgkg−1, PBDEs 0.5μgkg−1, and PAHs 0.05–0.25μgkg−1. Ambient mass spectrometry employing a direct analysis in real time (DART) ion source was shown as an effective tool for fat control in extract, which is needed during the method development and examination of unknown samples prior to the analysis. Further extension of a method scope by other similar analytes is easily possible.
Keywords: Fish; Shrimps; PCB; PBDE; PAH; GC–TOFMS; DART
Ionic liquid-based microwave-assisted dispersive liquid–liquid microextraction and derivatization of sulfonamides in river water, honey, milk, and animal plasma by Xu Xu; Rui Su; Xin Zhao; Zhuang Liu; Yupu Zhang; Dan Li; Xueyuan Li; Hanqi Zhang; Ziming Wang (pp. 92-99).
The extraction and derivatization efficiency of SAs is dependent on type and volume of extraction solvent, type and volume of disperser, microwave power and irradiation time, volume of derivatization reagent, pH of sample solution as well as ionic strength.Display Omitted► A new, rapid and sensitive method for determining sulfonamides (SAs) was proposed. ► Derivatization, extraction and preconcentration of SAs were performed in one step. ► IL-based MADLLME and derivatization were first applied for the determination of SAs. ► Trace SAs in river water, honey, milk, and pig plasma were determined.The ionic liquid-based microwave-assisted dispersive liquid–liquid microextraction (IL-based MADLLME) and derivatization was applied for the pretreatment of six sulfonamides (SAs) prior to the determination by high-performance liquid chromatography (HPLC). By adding methanol (disperser), fluorescamine solution (derivatization reagent) and ionic liquid (extraction solvent) into sample, extraction, derivatization, and preconcentration were continuously performed. Several experimental parameters, such as the type and volume of extraction solvent, the type and volume of disperser, amount of derivatization reagent, microwave power, microwave irradiation time, pH of sample solution, and ionic strength were investigated and optimized. When the microwave power was 240W, the analytes could be derivatized and extracted simultaneously within 90s. The proposed method was applied to the analysis of river water, honey, milk, and pig plasma samples, and the recoveries of analytes obtained were in the range of 95.0–110.8, 95.4–106.3, 95.0–108.3, and 95.7–107.7, respectively. The relative standard deviations varied between 1.5% and 7.3% ( n=5). The results showed that the proposed method was a rapid, convenient and feasible method for the determination of SAs in liquid samples.
Keywords: Ionic liquid-based microwave-assisted dispersive liquid–liquid microextraction; In situ derivatization; Sulfonamides; High-performance liquid chromatography-fluorescence detection
Improvement and extension of the application scope for matrix-assisted laser desorption/ionization mass spectrometric analysis-oriented N-alkylpyridinium isotope quaternization by Hang Wang; Haoyang Wang; Li Zhang; Jing Zhang; Jiapeng Leng; Tingting Cai; Yinlong Guo (pp. 100-106).
Display Omitted► N-Alkylpyridinium isotope quaternization (NAPIQ) was developed to wider applications. ► NAPIQ was extended to steroids and carbohydrates. ► NAPIQ improved the detection sensitivity in mass spectrometric analysis. ► NAPIQ avoid using isotope-coded internal standards of the identical structure. ► Urinary steroids were screened by NAPIQ method.Based on our previous report on N-alkylpyridinium isotope quaternization (NAPIQ) for the analysis of cholesterol and fatty alcohols, we have further developed the NAPIQ method for wider applications in screening various small compounds. The reaction scope and improvement were investigated via the screening of compounds with different reaction sites. The experimental results showed that the NAPIQ strategy was suitable not only for steroids with alcoholic or α, β-unsaturated ketone moieties, but could also be applied to label carbohydrates by changing the reaction solvent. The byproducts from target compounds with multiple groups could be reduced by improving the reaction conditions. The derivatization method significantly improved the detection sensitivity for these compounds in matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometric (MALDI-FTMS) analysis. The detection sensitivity and selectivity of the NAPIQ method were higher than conventionally used Girard reagents. Finally, endogenous steroids in urine samples were screened using the NAPIQ method. NAPIQ was proven to be an efficient alternative method for analyzing steroids and carbohydrates, without the need for isotopically coded internal standards.
Keywords: Isotopic pyridinium; Chemical derivatization; α; ,; β; -Unsaturated ketone; Steroids; Carbohydrates; Mass spectrometry
Determination of Vasopressin and Desmopressin in urine by means of liquid chromatography coupled to quadrupole time-of-flight mass spectrometry for doping control purposes by A. Thomas; E. Solymos; W. Schänzer; N. Baume; M. Saugy; F. Dellanna; M. Thevis (pp. 107-113).
Display Omitted► Antidiuretic-hormones Vasopressin and Desmopressin have a relevancy in doping controls. ► Determination in urinary specimens by mass spectrometry was developed. ► Target compound were found in excretion study urine samples.The anti-diuretic neurohypophysial hormone Vasopressin (Vp) and its synthetic analogue Desmopressin (Dp, 1-desamino-vasopressin) have received considerable attention from doping control authorities due to their impact on physiological blood parameters. Accordingly, the illicit use of Desmopressin in elite sport is sanctioned by the World Anti-Doping Agency (WADA) and the drug is classified as masking agent. Vp and Dp are small (8–9 amino acids) peptides administered orally as well as intranasally.Within the present study a method to determine Dp and Vp in urinary doping control samples by means of liquid chromatography coupled to quadrupole high resolution time-of-flight mass spectrometry was developed. After addition of Lys-Vasopressin as internal standard and efficient sample clean up with a mixed mode solid phase extraction (weak cation exchange), the samples were directly injected into the LC–MS system. The method was validated considering the parameters specificity, linearity, recovery (80–100%), accuracy, robustness, limit of detection/quantification (20/50pgmL−1), precision (inter/intra-day<10%), ion suppression and stability. The analysis of administration study urine samples collected after a single intranasal or oral application of Dp yielded in detection windows for the unchanged target analyte for up to 20h at concentrations between 50 and 600pgmL−1. Endogenous Vp was detected in concentrations of approximately 20–200pgmL−1 in spontaneous urine samples obtained from healthy volunteers.The general requirements of the developed method provide the characteristics for an easy transfer to other anti-doping laboratories and support closing another potential gap for cheating athletes.
Keywords: Doping; Sport; Mass spectrometry; Anti-diuretic
Interaction of adenine with palladium chloride, determination of adenine via resonance Rayleigh scattering method by Qianying Xu; Zhongfang Liu; Xiaoli Hu; Ling Kong; Shaopu Liu (pp. 114-120).
Palladium chloride could react with adenine to form a 1:1 chelate, which led to the remarkable enhancement of resonance Rayleigh scattering (RRS) with the peak at 311nm. The enhanced intensities present a good linear relationship with the concentration of adenine, which suggests that the system can be used for the quantitative determination of adenine.Display Omitted► This method is sensitive, the detection limit for adenine is 5.4×10−9molL−1. ► Other nucleobases have no similar reaction, the method has high selectivity. ► The interaction are characterized by many methods.In pH 1.7–3.5 acid medium, palladium chloride could react with adenine (A) to form a ternary complex of [PdCl2·A], which would self-aggregate to form uniformly dispersed nanoparticles-[PdCl2·A]n with an average size of 42nm through the squeezing effect of aqueous phase and van der Waals force. This resulted in an enhancement of resonance Rayleigh scattering (RRS), second-order scattering (SOS) and frequency doubling scattering (FDS). The maximum wavelengths were located at 311nm, 611nm and 395nm, respectively. The scattering intensities of the three methods were proportional to the concentration of adenine in certain ranges, and the detection limit of the most sensitive RRS method was 5.4×10−9molL−1 (0.73ngmL−1). The experimental conditions were optimized and effects of coexisting substances were evaluated. The method showed excellent selectivity because a certain amount of other nucleobase, nucleoside or nucleotide would not influence the measurement. Accordingly, a novel rapid, convenient, sensitive and selective RRS method for determination of adenine was proposed and applied to detect adenine in tablet and hydrolyzates of ctDNA samples with satisfactory results. The shape of nanoparticles was characterized by atomic force microscopy. The reaction mechanism and the reasons for enhancement of scattering were discussed by infrared spectra, quantum chemical calculations and absorption spectroscopy.
Keywords: Adenine; Palladium chloride; Resonance Rayleigh scatting; [PdCl; 2; ·A]; n; nanoparticles
Kinetics and selectivity of permanganate chemiluminescence: A study of hydroxyl and amino disubstituted benzene positional isomers by Teo Slezak; Zoe M. Smith; Jacqui L. Adcock; Christopher M. Hindson; Neil W. Barnett; Pavel N. Nesterenko; Paul S. Francis (pp. 121-127).
Display Omitted► The rate of reaction and chemiluminescence intensity are highly analyte dependent. ► The selectivity of reagent can be tuned by manipulating reaction conditions. ► Acids and polyphosphates both stabilise the key Mn(III) precursor to the emitter. ► Formaldehyde and formic acid generate higher concentrations of Mn(III).Examination of the chemiluminescence reactions of dihydroxybenzenes, aminophenols and phenylenediamines with acidic potassium permanganate has provided a new understanding of the relationships between analyte structure, reaction conditions, kinetics of the light-producing pathway and emission intensity, with broad implications for this widely utilised chemiluminescence detection system. Using a permanganate reagent prepared in a polyphosphate solution and adjusted to pH 2.5, large differences in the rate of reaction with different positional isomers were observed, with the meta-substituted forms reacting far slower and therefore exhibiting much lower chemiluminescence intensities in flow analysis systems. The preliminary partial reduction of permanganate to form significant concentrations of Mn(III) increased the rate of reaction with all analytes tested, resulting in comparable or (in the case of aminophenol and phenylenediamine) even greater emission intensities for the meta-isomers, demonstrating the opportunity to tune the selectivity of the reagent towards certain classes of compound or even specific positional isomers of the same compound. Using more acidic permanganate reagents, in which polyphosphates are not required, the discrepancy between the chemiluminescence intensities was still observed, but was less prominent due to the generally faster rates of reaction. The enhancement of these chemiluminescence reactions by on-line addition of formic acid or formaldehyde can in part also be attributed to the generation of significant pools of the key Mn(III) precursor to the emitting species.
Keywords: Chemiluminescence; Flow injection analysis; Permanganate; Selectivity
Simultaneous determination of norfloxacin and lomefloxacin in milk by first derivative synchronous fluorescence spectrometry using Al (III) as an enhancer by Yan-Ni Yi; Gui-Rong Li; Yong-Sheng Wang; Yu-Zhen Zhou; Hui-Min Zhu (pp. 128-134).
Display Omitted► Norfloxacin and lomefloxacin in milk were determined simultaneously. ► The combination of synchronous, derivative and zero-crossing techniques reveals high sensitivity and selectivity. ► Al (III) was used as a fluorescence enhancer for norfloxacin and lomefloxacin.A novel method for the simultaneous determination of norfloxacin (NFLX) and lomefloxacin (LFLX) in milk samples was developed by using first derivative synchronous fluorimetry. The synchronous fluorescence (Δ λ=160nm) spectra and first derivative synchronous fluorescence spectra of NFLX, LFLX and their mixture were studied. The zero-crossing method was utilized to measure the first derivative value of the derivative spectrum. The zero-crossing points were located at 275.0nm for NFLX and at 283.8nm for LFLX, in first derivative synchronous fluorescence spectra. Therefore, 283.8nm and 275.0nm were selected for the determination of NFLX and LFLX. The first derivative values varied linearly with the concentrations in the range of 1.68×10−8–5.64×10−6molL−1 for NFLX and 1.89×10−8–6.19×10−6molL−1 for LFLX. The detection limits were 5.03×10−9molL−1 for NFLX and 7.58×10−9molL−1 for LFLX. The proposed method is reliable, selective and sensitive, and has been used successfully in the simultaneous determination of NFLX and LFLX in milk samples, whose results were in good agreement with those obtained by HPLC.
Keywords: Synchronous fluorimetry; First derivative spectrum; Zero-crossing; Norfloxacin; Lomefloxacin
A dual enzymatic-biosensor for simultaneous determination of glucose and cholesterol in serum and peritoneal macrophages of diabetic mice: Evaluation of the diabetes-accelerated atherosclerosis risk by Qilin Huang; Yarui An; Linlin Tang; Xiaoli Jiang; Hua Chen; Wenji Bi; Zhongchuan Wang; Wen Zhang (pp. 135-141).
In this paper, we reported a novel dual enzymatic-biosensor for simultaneous determination of glucose and cholesterol in serum and peritoneal macrophages (PMs) of diabetic mice to evaluate the diabetes-accelerated atherosclerosis risk. The biosensor was firstly modified with a poly-thionine (PTH) film as electron transfer mediator (ETM), then the gold nanoparticles (GNPs) were covered on the surface of PTH to act as tiny conduction centers for facilitating the electron transfer between enzymes and electrode. The schematic of the dual biosensor is shown in figure. The developed dual biosensor had good electrocatalytic activity toward the oxidations of glucose and cholesterol, exhibited a linear range from 0.008mM to 6.0mM for glucose with a detection limit of 2.0μM, and a linear range from 0.002mM to 1.0mM for cholesterol with a detection limit of 0.6μM. The results of the diabetic mice demonstrated that the cholesterol level was not changed obviously with the increase of glucose level in serum, while the cholesterol level was enhanced together with the increase of the glucose level in PMs. Previous studies have shown that the large accumulation of cholesterol in macrophage could lead to macrophage foam cell formation, the hallmark of early atherosclerosis. These findings indicated the possibility that high glucose induced by diabetes might increase the macrophage cholesterol level to further accelerate atherosclerosis development.Display Omitted► A novel biosensor was developed to determine glucose and cholesterol simultaneously.► The dual enzymatic-biosensor has good selectivity and high sensitivity.► We determined glucose and cholesterol in the real samples of diabetic mice.► The results showed that high glucose might increase the macrophage cholesterol level.► It provided useful experimental evidences for diabetes-accelerate atherosclerosis.In this paper, a novel dual enzymatic-biosensor is described for simultaneous determination of glucose and cholesterol in serum and peritoneal macrophages (PMs) of diabetic mice to evaluate the risk of diabetes-accelerated atherosclerosis. The biosensor was constructed by a three-step method. First, a poly-thionine (PTH) film was assembled on the surface of glassy carbon electrode by cyclic voltammetric electropolymerization of thionine, which serves as an electron transfer mediator (ETM). Second, gold nanoparticles (GNPs) were covered on the surface of PTH facilitating the electron transfer between glucose oxidase (GOx), cholesterol oxidase (ChOx) and electrode. Finally, the enzymes, GOx, cholesterol esterase (ChE), and ChOx, were covalently attached to the PTH layer through a chitosan (CH) linker. The PTH coupled with GNPs provides good selectivity, high sensitivity and little crosstalk for the dual enzymatic-biosensor. The developed biosensor had good electrocatalytic activity toward the oxidations of glucose and cholesterol, exhibiting a linear range from 0.008mM to 6.0mM for glucose with a detection limit of 2.0μM, and a linear range from 0.002mM to 1.0mM for cholesterol with a detection limit of 0.6μM. The results of the diabetic mice demonstrated that the cholesterol level did not change obviously with the increase of glucose level in serum, while the cholesterol level was induced with the increase of the glucose level in PMs. Previous studies have shown that the large accumulation of cholesterol in macrophage could lead to macrophage foam cell formation, which is the hallmark of early atherosclerosis. This study provides useful further evidences for the development of diabetes-accelerated atherosclerosis.
Keywords: Glucose; Cholesterol; Simultaneous determination; Diabetes-accelerated atherosclerosis risk
Immobilization of E. coli with autodisplayed Z-domains to a surface-modified microplate for immunoassay by Gu Yoo; Min Park; Eun-Hang Lee; Joachim Jose; Jae-Chul Pyun (pp. 142-147).
Display Omitted► An immunoassay is presented by immobilizing Escherichia coli with autodisplayed Z-domains. ► A microplate for the immobilization of E. coli was prepared for immunoassay. ► The surface of microplate was modified by using parylene-H and poly-l-lysine. ► The applicability was demonstrated for the medical diagnosis. Escherichia coli with autodisplayed Z-domains was reported to improve the sensitivity of immunoassays by the orientation control of antibodies. In this work, a sensitive microplate-based immunoassay is presented by immobilizing E. coli cells to a surface-modified microplate. The microplate was prepared by coating parylene-H film with formyl groups, and then covalently coupling poly-l-lysine to the parylene-H film. The E. coli cells were bound to the microplate by charge interactions between the negatively charged E. coli outer membrane and the positively charged microplate surface. In this work, the preparation of the microplate coated with poly-l-lysine is presented. The immobilization efficiency of E. coli to the modified surface was estimated to be far higher than non-specific interaction by fluorescence microscope and the optical transmittance of the modified microplate was measured to be feasible for immunoassay. The microplate-based immunoassay is demonstrated to be feasible for medical diagnosis of inflammatory diseases by using C-reactive protein as a target analyte for the medical diagnosis of inflammatory diseases.
Keywords: Immunoassay; Orientation control; Z-domain; Poly-; l; -lysine; Parylene; c-Reactive protein
Simultaneous determination of malachite green, brilliant green and crystal violet in grass carp tissues by a broad-specificity indirect competitive enzyme-linked immunosorbent assay by Yu-Dong Shen; Xing-Fei Deng; Zhen-Lin Xu; Yu Wang; Hong-Tao Lei; Hong Wang; Jin-Yi Yang; Zhi-Li Xiao; Yuan-Ming Sun (pp. 148-154).
Display Omitted► A broad-specificity ELISA for three triphenylmethane dyes was developed. ► The effect of hapten structures on assay performance was studied. ► The developed ELISA showed good sensitivity and uniform response to three analytes. ► Good accuracy and reproducibility were obtained in spiked fishes samples.An immunizing hapten (4-(carboxymethoxy)phenyl)bis(4-(diethylamino)phenyl)methylium for brilliant green (BG), a triphenylmethane dye with a potential illegal use in fish feeding, was synthesized and used to produce polyclonal antibody (PcAb) against BG. Unexpectedly, the obtained PcAb showed high cross-reactivity (CR) to malachite green (MG) and crystal violet (CV) in an indirect competitive enzyme-linked immunosorbent assay (icELISA). After screening against three heterologous coating antigens, the icELISA exhibited good sensitivity and uniform response to BG (IC50 of 1.98ngmL−1 and CR of 100%), MG (IC50 of 1.61ngmL−1 and CR of 105%) and CV (IC50 of 1.34ngmL−1 and CR of 142%) when using (4-(carboxymethoxy)phenyl)bis(4-(dimethylamino)phenyl)methylium as the coating hapten. Therefore, a broad-specificity icELISA for simultaneous determination of BG, MG and CV was developed. The recoveries of single analyte and mixture of three analytes from spiked grass carp tissues were estimated ranging from 74.94% to 110.39%. A statistically significant correlation of results was obtained between the developed icELISA and previously established HPLC approaches with the food-relevant three triphenylmethane dyes concentration range 1.83–200ngmL−1 ( R2=0.9224), indicating good accuracy of the icELISA and suitability for the broad-specific detection of the three triphenylmethane dyes in grass carp tissues.
Keywords: Broad-specific immunoassay; Malachite green; Brilliant green; Crystal violet; Grass carp tissues
Surface-enhanced Raman spectroscopic detection of Bacillus subtilis spores using gold nanoparticle based substrates by Han-Wen Cheng; Yuan-Yuan Chen; Xin-Xin Lin; Shuang-Yan Huan; Hai-Long Wu; Guo-Li Shen; Ru-Qin Yu (pp. 155-163).
Display Omitted► Gold nanoparticle-assembled substrates are demonstrated as a sensitive SERS probe. ► The SERS probe exhibits low LOD (1.5×109 sporesL−1) for detection of biomarker. ► The SERS probe is capable of detection of CaDPA released from spores. ► The reduction of the diagnostic peak width offers high resolution and sensitivity.The detection of bacterial spores requires the capability of highly sensitive and biocompatible probes. This report describes the findings of an investigation of surface-enhanced Raman spectroscopic (SERS) detection of Bacillus subtilis spores using gold-nanoparticle (Au NP) based substrates as the spectroscopic probe. The SERS substrates are shown to be highly sensitive for the detection of B. subtilis spores, which release calcium dipicolinate (CaDPA) as a biomarker. The SERS bands of CaDPA released from the spores by extraction using nitric acid provide the diagnostic signal for the detection, exhibiting a limit of detection (LOD) of 1.5×109 sporesL−1 (or 2.5×10−14M). The LOD for the Au NP based substrates is quite comparable with that reported for Ag nanoparticle based substrates for the detection of spores, though the surface adsorption equilibrium constant is found to be smaller by a factor of 1–2 orders of magnitude than the Ag nanoparticle based substrates. The results have also revealed the viability of SERS detection of CaDPA released from the spores under ambient conditions without extraction using any reagents, showing a significant reduction of the diagnostic peak width for the detection. These findings have demonstrated the viability of Au NP based SERS substrates for direct use with high resolution and sensitivity as a biocompatible probe for the detection of bacterial spores.
Keywords: Surface-enhanced Raman scattering; Gold nanoparticles; Biomarker; Calcium Dipicolinate; Bacillus subtilis
Magnetic core–shell fluorescent pH ratiometric nanosensor using a Stöber coating method by A. Lapresta-Fernández; T. Doussineau; A.J. Moro; S. Dutz; F. Steiniger; G.J. Mohr (pp. 164-170).
Display Omitted► Architecture combination of magnetic core with two fluorescence silica shells. ► Both shells properly functionalized which develops ratiometric pH measurements. ► Reference dye does not change significantly (∼1.9%) by modifying the pH. ► Sensitivity range between 2.0% and 4.9% and a few seconds of response time. ► One month stability with a signal variation of 4.3%.We describe the use of a modified Stöber method for coating maghemite (γ-Fe2O3) nanocrystals with silica shells in order to built magnetic fluorescent sensor nanoparticles in the 50–70nm diameter range. In detail, the magnetic cores were coated by two successive silica shells embedding two fluorophores (two different silylated dye derivatives), which allows for ratiometric pH-measurements in the pH range 5–8. Silica coated magnetic nanoparticles were prepared using maghemite nanocrystals as cores (5–10nm in diameter) coated by tetraethoxyorthosilicate via hydrolysis/condensation in ethanol, catalyzed by ammonia. In the inner shell was covalently attached a sulforhodamine B, which was used as a reference dye; while a pH-sensitive fluorescein was incorporated into the outer shell. Once synthesized, the particles were characterized in terms of morphology, size, composition and magnetization, using dynamic light scattering (DLS), transmission electron microscopy (TEM), X-ray diffraction (XRD) and vibrating sample magnetometry (VSM). TEM analysis showed the nanoparticles to be very uniform in size. Wide-angle X-ray diffractograms showed, for uncoated as well as coated nanoparticles, typical peaks for the spinel structure of maghemite at the same diffraction angle, with no structural changes after coating. When using VSM, we obtained the magnetization curves of the resulting nanoparticles and the typical magnetization parameters as saturation magnetization ( M s), coercivity ( H c), and remanent magnetization ( M r). The dual-dye doped magnetic-silica nanoparticles showed a satisfactory magnetization that could be suitable for nanoparticle separation and localized concentration of them. Changes in fluorescence intensity of the pH indicator in the different pH buffered solutions were observed within few seconds indicating an easy accessibility of the embedded dye by protons through the pores of the silica shell. The relationship between the ratio in fluorescence (sensor/reference dyes) and pH was adjusted to a sigmoidal fit using a Boltzmann type equation. Finally, the proposed method was statistically validated against a reference procedure using samples of water and physiological buffer with 2% (w/v) of horse serum added, indicating that there are no significant statistical differences at a 95% confidence level.
Keywords: Nanosensor; Stöber method; Iron oxide nanoparticles; Fluorescence; Ratiometric pH measurements
Part I: A comparative study of bismuth-modified screen-printed electrodes for lead detection by Josefina Calvo Quintana; Fabiana Arduini; Aziz Amine; Francesco Punzo; Giovanni Li Destri; Chiara Bianchini; Daniela Zane; Antonella Curulli; Giuseppe Palleschi; Danila Moscone (pp. 171-177).
.Display Omitted► “In situ” Bi-SPE has higher sensitivity than “ex situ” Bi-SPE and “Bi2O3 bulk” SPE. ► Electrochemical treatment of SPE before Bi film deposition allows one to reach low LOD. ► The linearity of Pb2+ in HCl and HClO4 is greatly affected by the ionic strength. ► Satisfactory values of the recovery percentage were obtained in drinking water samples.Lead determination was carried out in the frame of the European Union project Biocop (www.biocop.org) using a bismuth-modified screen-printed electrode (Bi-SPE) and the stripping analysis technique. In order to choose a sensitive Bi-SPE for lead detection, an analytical comparative study of electrodes modified by Bi using “in situ”, “ex situ” and “bulk” procedures was carried out. On the basis of the results obtained, we confirmed that the “in situ” procedure resulted in better analytical performances with respect to not only “ex situ” but also to “Bi2O3 bulk” modified electrodes, allowing for a linear range of lead ion concentration from 0.5 to 100μgL−1 and a detection limit of 0.15μgL−1. We demonstrated that, before the Bi film deposition, an oxidative electrochemical pre-treatment of the working electrode could be useful because it eliminates traces of lead in the graphite-ink, as shown with stripping measurements. It also improves the electrochemical performance of the electrodes as demonstrated with Electrochemical Impedance Spectroscopy (EIS) measurements. The influence of different analytical parameters, such as the electrolyte solution composition (acetate buffer, chloridric acid, nitric acid, perchloric acid) and the ionic strength was investigated in order to evaluate how to treat the sample before the analysis. The morphology of prepared “in situ” Bi-SPEs was also characterized by Atomic Force Microscopy (AFM). Finally, the Bi-SPEs were used to determine the concentration of lead ions in tap and commercial water samples obtaining satisfactory values of the recovery percentage (81% and 98%).
Keywords: Lead; Bismuth; Stripping analysis; Screen-printed electrode
Surface Plasmon Resonance imaging-based sensing for anti-bovine immunoglobulins detection in human milk and serum by S. Scarano; C. Scuffi; M. Mascini; M. Minunni (pp. 178-183).
Display Omitted► SPR imaging applied to human bodily fluids for immunosensing. ► Anti-bovine IgG in serum and milk for T1 diabetes risk prediction. ► Ex ante evaluation of matrix effect on biosensor. ► Experimental detection limits compatible for real application of the method.Only few papers deal with Surface Plasmon Resonance imaging (SPRi) direct detection on complex matrices, limiting the biosensor application to real analytical problems. In this work a SPRi biosensor for anti-bovine IgG detection in untreated human bodily fluids, i.e. diluted human serum and milk, was developed. Enhanced levels of cow's milk antibodies in children's serum are suspected for their possible correlation with Type 1 diabetes during childhood and their detection in real samples was up to now performed by classical immunoassays based on indirect detection. The biosensor was optimised in standard samples and then in untreated human milk for anti-bovine IgG direct detection. The key novelty of the work is the evaluation of matrix effect by applying to real samples an experimental and ex ante method previously developed for SPRi signal sampling in standard solutions, called “Data Analyzer”; it punctually visualises and analyses the behaviour of receptor spots of the array, to select only spot areas with the best specific vs. unspecific signal values. In this way, benefits provide by SPRi image analysis are exploited here to quantify and minimise drawbacks due to the matrix effect, allowing to by-pass every matrix pre-treatment except dilution.
Keywords: Surface Plasmon Resonance imaging; Diabetes T1D; Bovine IgG; Human milk; Human serum
Self-assembly and sensor response of photosynthetic reaction centers on screen-printed electrodes by Vijayender Bhalla; Valter Zazubovich (pp. 184-190).
.Display Omitted► New simple immobilization procedure for photosynthetic reaction centers on gold electrodes. ► Improved access of the mediator to the electrodes and faster response due to deliberately defective mercaptopropionic acid SAM. ► Method suitable for screen-printed gold electrodes ► Atrazine and picric acid detected by respective sensor.Photosynthetic reaction centers were immobilized onto gold screen-printed electrodes (Au-SPEs) using a self-assembled monolayer (SAM) of mercaptopropionic acid (MPA) which was deliberately defective in order to achieve effective mediator transfer to the electrodes. The pure Photosystem II (PS II) cores from spinach immobilize onto the electrodes very efficiently but fair badly in terms of photocurrent response (measured using duroquinone as the redox mediator). The cruder preparation of PS II known as BBY particles performs significantly better under the same experimental conditions and shows a photocurrent response of 20–35nA (depending on preparation) per screen-printed electrode surface (12.5mm2). The data was corroborated using AFM, showing that in the case of BBY particles a defective biolayer is indeed formed, with grooves spanning the whole thickness of the layer enhancing the possibility of mass transfer to the electrodes and enabling biosensing. In comparison, the PS II core layer showed ultra-dense organization, with additional formation of aggregates on top of the single protein layer, thus blocking mediator access to the electrodes and/or binding sites. The defective monolayer biosensor with BBY particles was successfully applied for the detection of photosynthesis inhibitors, demonstrating that the inhibitor binding site remained accessible to both the inhibitor and the external redox mediator. Biosensing was demonstrated using picric acid and atrazine. The detection limits were 1.15nM for atrazine and 157nM for picric acid.
Keywords: Photosynthetic reaction centers; Gold screen printed electrode; Self-assembled monolayer; Herbicide detection; Atrazine; Picric acid
Optimization of the structure-switching aptamer-based fluorescence polarization assay for the sensitive tyrosinamide sensing by Zhenyu Zhu; Thomas Schmidt; Maroi Mahrous; Valérie Guieu; Sandrine Perrier; Corinne Ravelet; Eric Peyrin (pp. 191-196).
Display Omitted► A structure-switching aptamer assay based on a fluorescence polarization (FP) signal transduction approach. ► Format relied on CS displacement by target. ► Fluorescence signal generation dependent on the fine interconnection between dye nature and CS length. ► Impact on assay performances.In this paper, a structure-switching aptamer assay based on a fluorescence polarization (FP) signal transduction approach and dedicated to thel-tyrosinamide sensing was described and optimized. A fluorescently labelled complementary strand (CS) of the aptamer central region was used as a probe. The effects of critical parameters such as buffer composition and pH, temperature, aptamer:CS stoichiometry, nature of the dye (Fluorescein (F) or Texas Red (TR)) and length of the CS (15-, 12-, 9- and 6-mer) on the assay analytical performances were evaluated. Under optimized experimental conditions (10mM Tris–HCl, 5mM MgCl2 and 25mM NaCl, pH 7.5 temperature of 22°C and stoichiometry 1:1), the results showed that, for a 12-mer CS, the F dye moderately increased the method sensitivity in comparison to the TR label. The F labelled 9-mer CS, however, did not allow the hybrid formation with the functional nucleic acid, thus emphasizing the importance of the nature of the fluorophore. In contrast, the same 9-mer CS labelled with the TR dye was able to effectively associate with the aptamer and was easily displaced upon target binding as demonstrated by a significant improvement of the sensitivity and a detection limit of 250nM, comparable to those reported with direct aptasensing methods. The present study demonstrates that not only the CS length but also the nature of the dye played a preponderant role in the performance of the structure-switching aptamer assay, highlighting the importance of interdependently controlling these two factors for an optimal FP-based sensing platform.
Keywords: Aptamer; Fluorescence polarization; Structure switching; Complementary strand
Fully automated solid-phase microextraction–fast gas chromatography–mass spectrometry method using a new ionic liquid column for high-throughput analysis of sarcosine and N-ethylglycine in human urine and urinary sediments by F. Bianchi; S. Dugheri; M. Musci; A. Bonacchi; E. Salvadori; G. Arcangeli; V. Cupelli; M. Lanciotti; L. Masieri; S. Serni; M. Carini; M. Careri; A. Mangia (pp. 197-203).
Display Omitted► Fully automated SPME–Fast GC–MS method for sarcosine and N-ethylglycine determination. ► Possibility of high-throughput analyses and point of care testing. ► Potential role of sarcosine as biomarker for prostate cancer detection.A fully automated, non invasive, rapid and high-throughput method for the direct determination of sarcosine and N-ethylglycine in urine and urinary sediments using hexyl chloroformate derivatization followed by direct immersion solid-phase micro extraction and fast gas chromatography–mass spectrometric analysis was developed and validated. The use of a new ionic liquid narrow bore column, as well as the automation and miniaturization of the preparation procedure by a customized configuration of the utilized XYZ robotic system, allowed a friendly use of the GC apparatus achieving a quantitation limit of 0.06μgL−1 for sarcosine, good repeatability with CV always lower than 7% and reduced analysis times useful for point-of-care testing. The method was then applied for the analysis of 56 samples of urine and urinary sediments in healthy subjects, in those with benign prostatic hypertrophy and in patients with clinically localized prostate cancer. The results obtained showed that the medians of sarcosine/creatinine in urine were 103, 137 and 267μgg−1 respectively, thus assessing the potential use of sarcosine as urinary biomarker for prostate cancer detection.The highest values of sensitivity (79%) and specificity (87%) were obtained in correspondence of a cut-off value of 179μgsarcosine(gcreatinine)−1, thus by using this cut-off threshold, sarcosine was significantly associated with the presence of cancer ( p<0.0001).Finally, ROC analyses proved that the discrimination between clinically localized prostate cancer and patients without evidence of tumor is significantly correlated with sarcosine.
Keywords: Solid-phase microextraction; Ionic liquid column; Fast GC; Sarcosine; Prostate cancer
Solid phase extraction method for the separation and determination of chromium(III) in the presence of chromium(VI) using silica gel modified by N,N′-bis-(α-methylsalicylidene)-2,2-dimethyl-1,3-propanediimine by Agata Bartyzel; Ewa M. Cukrowska (pp. 204-209).
Display Omitted► New SPE method for Cr(III) separation/preconcentration was described. ► Silica gel modified with Schiff base was used as adsorbent. ► Conditions for quantitative preconcentration, elution and GFAAS determination were studied. ► The method can be applied to the highly saline samples. ► This method is a simple, effective, accurate and reproducible.N,N′-bis-(α-methylsalicylidene)-2,2-dimethyl-1,3-propanediimine (SBTD) modified silica gel was prepared and used as sorbent for solid phase extraction of Cr(III) ions from aqueous solution. This sorbent showed a high sorption affinity for Cr(III) while recovery of Cr(VI) was very low. The analyte ion retained on the column was eluted with 1molL−1 HNO3. The chromium ion in the eluent was determined by graphite furnace atomic absorption spectrometry. The effects of different parameters such as pH, eluent type and volume, Schiff's base concentration, sample and eluent flow rate, interfering ions and adsorbent amount were investigated.
Keywords: Chromium(III); Schiff's base; Silica gel; Solid phase extraction; Graphite furnace atomic absorption spectrometry
Multilayer chitosan-based open tubular capillary anion exchange column with integrated monolithic capillary suppressor by Xiaojia Huang; Frank W. Foss Jr.; Purnendu K. Dasgupta (pp. 210-217).
Display Omitted► Uses a multilayer chitosan–glutaraldehyde coating as anion exchanger. ► Uses a methacrylate-acrylic acid polymer monolith as suppressor. ► Demonstrates first integral suppressor open tubular anion chromatography.We describe a multilayered open tubular anion exchange column fabricated by alternately pumping solutions of chitosan and glutaraldehyde. The column is terminated in an integrally bonded monolithic suppressor cast around a mandrel of a tungsten wire, composed of an acrylic acid (AA)–ethylene dimethacrylate (EDMA) monolith that is made with sufficient porogen for the monolith to function as a membrane. For a 4.5m long 75μm bore column coated with 24 successive layers of the condensation polymer (estimated to contain ∼72 molecular layers) and coupled to 1cm length of a suppressor fabricated with 55–60% AA, effective separation of several common anions (F−, Cl−, NO2−, Br−, NO3−, average number of theoretical plates ∼12,000) and adequate suppression of 1mM KOH used as eluent was observed at a flow rate of 800nLmin−1 to obtain sub-picomol detection limits at an operating pressure of ∼1bar. The separation is not time efficient but the system can be meritorious in unique niche applications where a small form factor is desired and liquid volume and power consumption are more important than separation speed.
Keywords: Ion chromatography; Monolithic suppressor; Integrated suppressor; Open tubular chromatography