Check out our New Publishers' Select for Free Articles

Analytica Chimica Acta (v.709, #)

Editorial Board (pp. iii).

Determination of technetium-99 in environmental samples: A review by Keliang Shi; Xiaolin Hou; Per Roos; Wangsuo Wu (pp. 1-20).

Display Omitted► The source term, physicochemical properties, environmental distribution and behaviour of⁹⁹Tc are presented. ► Various sample pre-treatment and pre-concentration techniques of technetium are discussed. ► Chemical separation and purification techniques for⁹⁹Tc in environmental samples are reviewed. ► Measurement techniques for⁹⁹Tc in environmental level and automated analytical methods are reviewed. ► The reported analytical methods of⁹⁹Tc are critically compared to provide overall information.Due to the lack of a stable technetium isotope, and the high mobility and long half-life,⁹⁹Tc is considered to be one of the most important radionuclides in safety assessment of environmental radioactivity as well as nuclear waste management.⁹⁹Tc is also an important tracer for oceanographic research due to the high technetium solubility in seawater as TcO₄⁻. A number of analytical methods, using chemical separation combined with radiometric and mass spectrometric measurement techniques, have been developed over the past decades for determination of⁹⁹Tc in different environmental samples. This article summarizes and compares recently reported chemical separation procedures and measurement methods for determination of⁹⁹Tc. Due to the extremely low concentration of⁹⁹Tc in environmental samples, the sample preparation, pre-concentration, chemical separation and purification for removal of the interferences for detection of⁹⁹Tc are the most important issues governing the accurate determination of⁹⁹Tc. These aspects are discussed in detail in this article. Meanwhile, the different measurement techniques for⁹⁹Tc are also compared with respect to advantages and drawbacks. Novel automated analytical methods for rapid determination of⁹⁹Tc using solid extraction or ion exchange chromatography for separation of⁹⁹Tc, employing flow injection or sequential injection approaches are also discussed.

Keywords: Abbreviations; AMS; accelerator mass spectrometry; DIHEN; direct injection high efficiency nebulizer; EARP; enhanced actinide removal plant; EDTA; ethylenediaminetetraacetic acid; GBq; giga becquerel, 10; ⁹; Bq; GM; Geiger–Müller; HR; high resolution; ICP-MS; inductively coupled plasma mass spectrometry; ICP-QMS; inductively coupled plasma quadrupole mass spectrometry; ICP-SFMS; inductively coupled plasma sector field mass spectrometry; K; _sp; solubility product; LSC; liquid scintillation counting; MCN; microconcentric nebulizer; MS; mass spectrometry; NAA; neutron activation analysis; PBq; peta becquerel, 10; ¹⁵; Bq; RIMS; resonance ionization mass spectrometry; TBP; tri-butylphosphate; TBq; tera Becquerel, 10; ¹²; Bq; ETV; electrothermal vaporization; TEVA; TEVA-Spec™ resin; TiOA; tri-isooctylamine; TIMS; thermal ionization mass spectrometry; TOA; trioctylamine; USN; ultrasonic nebulizerTechnetium-99; Radionuclide; Analytical procedure; Environmental samples; Automated analysis; Review

Protein separation by capillary gel electrophoresis: A review by Zaifang Zhu; Joann J. Lu; Shaorong Liu (pp. 21-31).

Display Omitted► In this review, we survey 100 plus papers related to capillary gel electrophoresis of proteins. ► We present the progress and current status and discuss the pros and cons of this technique. ► We describe the basic components/procedures to implement CGE and exhibit the representative practical applications. ► We expect CGE to be an important analytical technique for protein analysis in the near future.Capillary gel electrophoresis (CGE) has been used for protein separation for more than two decades. Due to the technology advancement, current CGE methods are becoming more and more robust and reliable for protein analysis, and some of the methods have been routinely used for the analysis of protein-based pharmaceuticals and quality controls. In light of this progress, we survey 147 papers related to CGE separations of proteins and present an overview of this technology. We first introduce briefly the early development of CGE. We then review the methodology, in which we specifically describe the matrices, coatings, and detection strategies used in CGE. CGE using microfabricated channels and incorporation of CGE with two-dimensional protein separations are also discussed in this section. We finally present a few representative applications of CGE for separating proteins in real-world samples.

Keywords: Capillary gel electrophoresis; Proteins; Capillary electrophoresis; Capillary sieving electrophoresis

The reduction of rotational ambiguity in soft-modeling by introducing hard models by Azadeh Golshan; Hamid Abdollahi; Marcel Maeder (pp. 32-40).

Range of feasible concentration profiles before (top) and after hard constraint (right); each concentration profile is normalised to a maximum of one.Display Omitted► This is the first systematic study of effects of hard-model constraints on rotational ambiguity. ► The resulting reduction of the area of feasible solutions is substantial. ► This is demonstrated on a set of representative systems with three components.Rotational ambiguity is a major problem in the application of soft-modeling analysis to a variety of multivariate mixture resolution problems and particularly important in the analysis of kinetic data. Soft-modeling analyses rely on constraints that restrict the concentration profiles and/or the spectral responses of all components. The main goal of this work is to demonstrate how a hard-modeling constraint on concentration profiles drastically decreases the extent of the rotational ambiguity. Therefore, in the present paper the discussion is focused on systems in which hard-modeling information is available. The results of simulated examples reveal that the utilized hard constraint decreases the rotational ambiguity in estimated concentration profile even components that do not take part in the explicit model. In addition, the rate constant of known reaction is determined in this method.

Keywords: Hard–soft modeling; Rotational ambiguity; Unique and band solutions; Band boundaries of feasible solutions

Fabrication of tunable microreactor with enzyme modified magnetic nanoparticles for microfluidic electrochemical detection of glucose by Jin Sheng; Lei Zhang; Jianping Lei; Huangxian Ju (pp. 41-46).

Display Omitted► An enzyme microreactor is prepared using an enzyme-nanoparticles packed microchannel. ► The optimal performance can be obtained by the tunable length of the microreactor. ► Baseline separation from interferents can be achieved with a microfluidic device. ► A pretreatment-free determination method for glucose is proposed.A microfluidic device was designed for amperometric determination of glucose by packing enzyme modified magnetic nanoparticles (MNPs) in its microchannel as an enzyme microreactor. Glucose oxidase was covalently attached to the surface of MNPs and localized in the microchannel by the help of an external magnetic field, leading to a tunable packing length. By changing the length of microreactor from 3 to 10mm, the performance for glucose detection was optimized. The optimal linear range to glucose was from 25μM to 15mM with a detection limit of 11μM at a length of 6mm. The inter- and intra-day precisions for determination of 1.0mM glucose were 0.8% and 1.7%, respectively, and the device-to-device reproducibility was 95.6%. The enzyme reactor remained its 81% activity after three-week storage. Due to the advantages of the device and fracture sampling technique, serum samples could be directly sampled through the fracture to achieve baseline separation from ascorbic acid, and proteins in the samples did not interfere with the detection. This work provided a promising way for pretreatment-free determination of glucose with low cost and excellent performance.

Keywords: Enzyme; Microreactor; Electrochemical detection; Magnetic nanoparticles; Glucose

A novel non-enzymatic glucose sensor based on Cu nanoparticle modified graphene sheets electrode by Jing Luo; Sisi Jiang; Hongyan Zhang; Jinqiang Jiang; Xiaoya Liu (pp. 47-53).

Display Omitted► We electrodeposited Cu nanoparticles on graphene sheets. ► The obtained Cu-graphene sheets nanocomposite is a good catalyst for the oxidation of glucose. ► Wide linear range, low detection limit as well as quick response for glucose. ► Easy fabrication, low cost, good reproducibility and perfect specificity to glucose in the presence of interferents.A novel, stable and sensitive non-enzymatic glucose sensor was developed by potentiostatically electrodepositing metallic Cu nanoparticles on graphene sheets. The electrochemical performance of the Cu-graphene sheets electrode for detection of glucose was investigated by cyclic voltammetry and chronamperometry. The Cu-graphene sheets electrode displayed a synergistic effect of copper nanoparticles and graphene sheets towards the oxidation of glucose in alkaline solution, showing higher oxidation current and negative shift in peak potential. At detection potential of 500mV, the Cu-graphene electrode sensor presented a wide linear range up to 4.5mM glucose with a detection limit of 0.5μM (signal/noise=3). In addition, the sensor responds very quickly (<2s) with addition of glucose. Furthermore, the Cu-graphene sheets electrode exhibits high stability and selectivity to glucose, and the poisoning by chloride ion as well as interference from the oxidation of common interfering species (ascorbic, dopamine, uric acid and carbohydrate) are effectively avoided. The Cu-graphene sheets electrode allows highly selective and sensitive, stable and fast amperometric sensing of glucose, which is promising for the development of non-enzymatic glucose sensor.

Keywords: Graphene sheets; Copper nanoparticles; Electrodeposition; Glucose; Non-enzymatic sensor

Determination of ethylenediaminetetraacetic acid in sea water by solid-phase extraction and high-performance liquid chromatography by Tomoko Kemmei; Shuji Kodama; Hironori Fujishima; Atsushi Yamamoto; Yoshinori Inoue; Kazuichi Hayakawa (pp. 54-58).

Display Omitted► EDTA in sea water was analyzed by HPLC combined with a new preconcentration procedure. ► Solid-phase extraction using activated carbon was applied for the sample preconcentration. ► The enrichment permitted the determination of EDTA at concentrations as low as 1.0nM. ► Good recoveries were obtained for both brackish and full-strength sea water.The chelating agent EDTA is widely used, and as a result is showing up widely in the aquatic environment. Here we describe a preconcentration procedure for measuring EDTA concentration in sea water samples by HPLC. The procedure consists of forming an Fe(III) complex followed by solid-phase extraction using an activated carbon cartridge. After the preconcentration, EDTA was quantified by HPLC with ultraviolet detection (260nm). The enrichment permitted the determination of EDTA at concentrations as low as 1nM. Good recoveries were obtained for both brackish and full-strength sea water with high repeatability (RSD<6%). The method was applied to sea water samples taken from near the mouth of the Oyabe River in Japan.

Keywords: EDTA; Solid-phase extraction; Activated carbon; HPLC; Sea water; Synthetic chelating agents

Highly efficient microextraction of chlorophenoxy acid herbicides in natural waters using a decanoic acid-based nanostructured solvent prior to their quantitation by liquid chromatography–mass spectrometry by Antonia Moral; Carmen Caballo; María Dolores Sicilia; Soledad Rubio (pp. 59-65).

Display Omitted► A solvent made up of nanostructured assemblies is proposed for microextraction. ► Chlorophenoxy acids are isolated and concentrated from natural waters. ► Method assets are high extraction efficiency, rapidity, simplicity and low cost.Solvents used in microextraction require high solubilising capability to efficiently extract the target compounds. In this article, nanostructured solvents made up of alkyl carboxylic acids (ACAs) aggregate are proposed for the efficient microextraction of acidic pesticides from natural waters. The target compounds were chlorophenoxy acid herbicides (CPAHs) widely used in agriculture, forestry and gardening (viz. 2,4-D, MCPA, MCPP, 2,4,5-T and MCPB). The supramolecular solvents (SUPRASs) tested were generated from solutions of reverse micelles of octanoic (OcA), decanoic (DeA) and dodecanoic (DoA) acid in THF by the addition of water, which acted as the coacervating agent. The DeA-based SUPRAS was the most efficient extractant for CPAHs; actual concentration factors (ACFs) of 260 for 2,4-D, 290 for MCPA, and 400 for MCPP, 2,4,5-T and MCPB were obtained. The explanation for so high ACFs can be found in the extremely efficient retention mechanisms that the DeA-based SUPRAS provides for CPAHs (i.e. formation of hydrogen bonds and hydrophobic interactions), and the high number of binding sites that it contains (i.e. the concentration of biosurfactant in the SUPRAS was 0.56mgμL⁻¹). Both characteristics permitted to effectively extract the target analytes in a low volume of solvent (about 2μL of solvent per mL of sample). Others assets of the proposed supramolecular solvent-based microextraction (SUSME) approach included recoveries no dependent on matrix composition, rapidity (sample treatment spent about 15min), use of low volume of sample (63mL per analysis) and simplicity (no special lab equipments was needed). Combination with liquid chromatography/ion–trap mass spectrometry [LC–(IT)MS] afforded method quantitation limits for CPAHs within the interval 22–30ngL⁻¹. The precision of the method, expressed as relative standard deviation ( n=11, [CPAH]=200ngL⁻¹), was in the range 2.9–5.8%. The applicability of the method to the analysis of natural waters was assessed by determining the target analytes in fortified river and underground water samples.

Keywords: Nanostructured solvents; Supramolecular assemblies; Liquid chromatography–ion trap mass spectrometry; Chlorophenoxy acid herbicides; Underground and river waters

Optimal strategies for determination of free/extractable and total microcystins in lake sediment by Xingqiang Wu; Chunbo Wang; Bangding Xiao; Yang Wang; Na Zheng; Jingshuang Liu (pp. 66-72).

Display Omitted► An optimized solvent extraction for analysis of free MCs in sediments was proposed. ► Best recovery of free MCs in sediments was found via sequential solvent extraction. ► We further optimized the Lemieux oxidation for analysis of total MCs in sediments. ► The yield of MMPB decreased as the content of sediment organic matter increased. ► Seven of thirty sediment samples showed positive results of MCs in Lake Dianchi.The optimization of analytical procedures for the quantification of free and total microcystins (MCs) in natural sediments was systematically examined based on solvent extraction and Lemieux oxidation. In this optimized analytical procedure, a sequential solvent extraction using 50% (v/v) methanol and EDTA-sodium pyrophosphate was selected as the optimal extraction solvent for free MCs analysis, after which the purified extracts and sediment residuals were applied to the optimized Lemieux oxidation for determination of total MCs in lake sediments. The optimized procedures were shown to be efficient and reliable for the routine analysis of both free and total MCs in lake sediment samples, as indicated by the minimal adverse impact of sediment organic matter on the recovery of free MCs and yield of MMPB (2-methyl-3-methoxy-4-phenylbutyric acid). Finally, the developed procedures were applied to field sediment samples collected from Lake Dianchi during a bloom season and seven of thirty samples showed positive results.

Keywords: Microcystin; 2-Methyl-3-methoxy-4-phenylbutyric acid (MMPB); Sediment; Solvent extraction; Lemieux oxidation

Development of GC–MS/MS method with programmable temperature vaporization large volume injection for monitoring of 17β-estradiol and 2-methoxyestradiol in plasma by A.K. Tsakalof; D.C. Gkagtzis; G.N. Koukoulis; C.S. Hadjichristodoulou (pp. 73-80).

Display Omitted► GC–MS/MS method for the quantification of 17β-estradiol and 2-methoxyestradiol in plasma. ► Increased sensitivity with ion trap operated under increased damping gas flow. ► Straightforward and efficient method for steroids’ isolation from plasma is described. ► LOD 5.5 and 18.4pgmL⁻¹ for 2-methoxyestradiol and 17β-estradiol, respectively.Monitoring of estradiol and its metabolites in biological samples is essential for the accurate diagnosis of a number of endocrine diseases. In this study, a sensitive, precise and specific GC–MS/MS method for the quantification of 17β-estradiol (17-BE) and its main metabolite, 2-methoxyestradiol (2-MEOE), in plasma was developed and validated. Plasma concentrations of these steroids are currently investigated as diagnostic markers for pre-eclampsia, a systematic disorder of pregnancy and a leading cause of maternal and fetal morbidity and mortality worldwide.The method comprised treatment of the plasma sample by protein precipitation and subsequent isolation of steroids by solid phase extraction, derivatization of steroids by trifluoroacetic anhydride and GC–MS/MS analysis of the derivatized steroids. The large volume (10μL) injection with the assistance of a Programmed Temperature Vaporization (PTV) injector in solvent split mode allowed a substantial increase in the sensitivity of the method.The ion trap MS was operated in optimized Product Ion Scan. By increasing the damping gas flow in the ion trap from the conventional 0.3mLmin⁻¹ to 2mLmin⁻¹, ion fragmentation was reduced and the instrument response was enhanced substantially. As a result, mass spectra with predominant molecular ions were acquired and molecular ions of the steroids of interest were used as precursor ions thus increasing specificity of the method.Under optimized GC–MS/MS conditions in product ion mode, the Limit of Detection (LOD) of the analyzed steroids ranged from 18.4pgmL⁻¹ for 17-BE to 5.5pgmL⁻¹ for 2-MEOE (S/N=3). The instrument response was linear in the investigated concentration range from 0.1 to 10ngmL⁻¹ with R²>0.99 for 17-BE and 2-MEOE. The intra-batch accuracy obtained for quality control samples at the concentration levels of 0.1, 1, 3, 7ngmL⁻¹ ranged from 94.9% to 109.9% for 17-BE and from 99.9% to 104.5% for 2-MEOE.

Keywords: Abbreviations; 17-BE; 17β-estradiol; 2-MEOE; 2-methoxyestradiol; 2FE; 2-fluoroestradiol; TFAA; trifluoroacetic anhydride; PTV injector; Programmed Temperature Vaporizing injector; IT; ion trap; CID; Collision Induced Dissociation; SPE; Solid Phase Extraction17β-Estradiol; 2-Methoxyestradiol; GC–MS/MS; Steroids; Pre-eclampsia

Analysis of recombinant human erythropoietin glycopeptides by capillary electrophoresis electrospray–time of flight-mass spectrometry by Estela Giménez; Raquel Ramos-Hernan; Fernando Benavente; José Barbosa; Victoria Sanz-Nebot (pp. 81-90).

Display Omitted► CE–TOF-MS methodology for the analysis of rhEPO and hEPO glycopeptides in biological fluids. ► Obtaining a reliable glycopeptide map of rhEPO. ► Starting point to detect the use of this hormone in sports. ► Detection of 2 sialoforms not previously described in the glycopeptide literature.Capillary electrophoresis electrospray–mass spectrometry was used to detect and characterize the great variety of O- and N-glycopeptide glycoforms of recombinant human erythropoietin (rhEPO) using an orthogonal accelerating time-of-flight mass spectrometer to obtain their exact molecular masses (CE–TOF-MS). rhEPO was digested with trypsin and Glu-C and analyzed by CE–TOF-MS to detect O₁₂₆, N₈₃, N₂₄–N₃₈ and N₂₄ and N₃₈ glycopeptide glycoforms, respectively. Neuraminidase was first used to enhance the detection of the glycopeptides and detect all possible glycoforms contained in each glycosylation site. O₁₂₆ and N₈₃ glycopeptides were extensively characterized. Twelve sialoforms corresponding to 5 different glycoforms were detected in N₈₃, and for the first time, a sulfated sialoform of this glycopeptide was also detected. In the case of O₁₂₆, different sialoforms with different types of sialic acids (Neu5Gc and Neu5Ac) were detected and an estimation of the relative percentage of Neu5Gc versus Neu5Ac was also carried out for this glycopeptide. N₂₄ and N₃₈ glycosylation sites were also characterized by CE–TOF-MS after Glu-C digestion and these results permitted to rule out some glycan combinations for N₂₄–N₃₈ glycopeptide glycoforms. This study provided a reliable glycopeptide map of rhEPO and may be regarded as an excellent starting point to analyze rhEPO glycopeptides in biological fluids and detect the use of this hormone in sports.

Keywords: Glycopeptide; EPO; Doping; Capillary electrophoresis electrospray-mass spectrometry

Surface-enhanced Raman scattering-active silver nanostructures with two domains by Chun-Chao Chang; Kuang-Hsuan Yang; Yu-Chuan Liu; Chung-Chin Yu (pp. 91-97).

SEM image of Ag NSs-deposited Pt substrate prepared by sonoelectrochemical deposition–dissolution cycles under a cathodic overpotential of 0.6V and an anodic overpotential of 0V from OCP with a ratio of reaction times of deposition to dissolution of Ag NSs to be 0.2.Display Omitted► Prepare new SERS-active substrates with two domain-Ag na nostructures. ► The method is based on a strategy of electrochemical deposition–dissolution cycles. ► Raman scattering enhancement for R6G with an enhancement factor of 2.3×10⁸.Generally, a controllable and reproduced surface roughness for surface-enhanced Raman scattering (SERS) studies can be generated through control of the electrochemical oxidation–reduction cycles (ORC) procedure. In this work, we propose a new sonoelectrochemical approach to prepare SERS-active substrates with two domain-Ag nanostructures. The method is based on a strategy of deposition–dissolution cycles (DDCs) by using a cathodic overpotential and an anodic overpotential from open circuit potential (OCP) in turn under sonication. The prepared SERS-active substrate demonstrates large Raman scattering enhancement for adsorbed Rhodamine 6G (R6G) with an enhancement factor of 2.3×10⁸ and a limit of detection of 2×10⁻¹³M. The improved SERS performances can be successfully explained from the viewpoints of electromagnetic (EM) and chemical (CHEM) enhancements.

Keywords: Surface-enhanced Raman scattering; Ag nanostructures; Sonoelectrochemical methods; Limit of detection

Rational design and synthesis of water-compatible molecularly imprinted polymers for selective solid phase extraction of amiodarone by Turghun Muhammad; Liu Cui; Wang Jide; Elena V. Piletska; Antonio R. Guerreiro; Sergey A. Piletsky (pp. 98-104).

Display Omitted► We developed a non-imprinted polymer (NIP) library with 18 monomers. ► Monomers were screened against amiodarone with NIP library by binding test. ► NIP library screening had similar result with computer modeling. ► High selective water compatible imprinted polymers were made with the monomer selected by the screening. ► The polymers were used in solid-phase extraction of amiodarone from aqueous sample.Novel water-compatible molecularly imprinted polymers (MIPs) selective for amiodarone (AD) were designed via a new methodology which relies on screening library of non-imprinted polymers (NIPs). The NIP library consisted of eighteen cross-linked co-polymers synthesized from monomers commonly used in molecular imprinting. The binding capacity of each polymer in the library was analyzed in two different solvents. Binding in water was used to assess non-specific (hydrophobic) interactions and binding in an appropriate organic solvent was used to assess specific interactions. A good correlation was found between the screening tests and modeling of monomer–template interactions performed using computational approach. Additionally, analysis of template–monomer interactions was performed using UV–vis spectroscopy. As the result, 4-vinylpyridine (4-VP) was selected as the best monomer for developing MIP for AD. The 4-VP-based polymers demonstrated imprinting factor equal 3.9. The polymers performance in SPE was evaluated using AD and its structural analogues. The recovery of AD was as high as 96% when extracted from spiked phosphate buffer (pH 4.5) solution and 82.1% from spiked serum samples. The developed MIP shown as a material with specific binding to AD, comparing to its structural analogues, 1-(2-diethylaminoethoxy)-2,6-diiodo-4-nitrobenzene and lidocaine, which shown 9.9% and 25.4% of recovery from the buffer solution, correspondingly. We believe that the screening of NIP library could be proposed as an alternative to commonly used computational and combinatorial approaches.

Keywords: Molecularly imprinted polymer; Solid-phase extraction; Amiodarone; Bovine serum; Monomer screening; Rational design

Waterpipe smoke: A considerable source of human exposure against furanic compounds by Jens Schubert; Jana Bewersdorff; Andreas Luch; Thomas G. Schulz (pp. 105-112).

Display Omitted► First study reporting on furanic compounds in waterpipe smoke. ► Identification of as yet unknown compounds in waterpipe smoke by means of HS-SPME–GC–MS. ► Development and validation of an RP-HPLC–DAD method for the determination of nine furanic compounds in waterpipe smoke. ► Advancement of published RP-HPLC methods by introducing an internal standard. ► Waterpipe smoke reveals as significant source of exposure against furanic compounds.Smoking of waterpipes became increasingly popular in the Western hemisphere in recent years. Yet, up to now only little is known about the health hazards and on the composition of waterpipe smoke. To obtain more information on the ingredients present in waterpipe smoke we utilized two different approaches. Based on headspace-solid-phase microextraction–gas chromatography–mass spectrometry (HS-SPME–GC–MS) instrumentation we identified new compounds present in the waterpipe smoke. Additional reversed-phase-high performance liquid chromatography–diode array detection (RP-HPLC–DAD) then led us to perform reliable quantification of the newly detected chemical species. Upon identification of a range of different furanic compounds such as 5-(hydroxymethyl)-2-furaldehyde (HMF), 2-furaldehyde, and others, we developed an easy-to-perform and fast RP-HPLC–DAD method to quantify these compounds in the complex matrix of waterpipe smoke. The detection limits range from 0.04μg for HMF to 7.1μg for 3-furan methanol per smoking session. Linearity, intra- and inter-day precision and recovery were determined and proved excellent. We analyzed 5 waterpipe tobacco brands and found up to 62.3±11mg of HMF generated during one waterpipe smoking session. The applied smoking protocol comprised 171 puffs of 530mL each and 2.6s duration every 20s. Our results reveal that waterpipe smoking constitutes a major source of HMF exposure. Furthermore, we found a distinct filter effect of the bowl water for all furanic compounds investigated except HMF.

Keywords: Waterpipe; Furanic compounds; 5-(Hydroxymethyl)-2-furaldehyde; 2-Furaldehyde; Reversed-phase-high performance liquid chromatography–diode array detection

Analysis of isoflavones in soy drink by capillary zone electrophoresis coupled with electrospray ionization mass spectrometry by M. Bustamante-Rangel; M.M. Delgado-Zamarreño; R. Carabias-Martínez; J. Domínguez-Álvarez (pp. 113-119).

.Display Omitted► Separation and quantification of isoflavones by CE–ESI-MS. ► CE separation as anions in positive mode and ionization in ESI positive-ion mode. ► Programmed nebulizing gas pressure prevents drops in current and improves the resolution of anions. ► Analysis of isoflavones (glucosides and aglycones) in soy drink samples.Capillary zone electrophoresis coupled with electrospray ionization mass spectrometry (CZE–ESI-MS) has been applied for the first time for the separation and quantification of isoflavones in soy products. The proposed method was successfully applied to the determination of seven isoflavones, including aglycones and glucosides, in soy drink. The target compounds were the glucosides daidzin and genistin, and the aglycones daidzein, genistein, formononetin, biochanin A and glycitein. During CE separation in positive mode, the analytes were present as anions, and MS detection was carried out in ESI positive-ion mode. To prevent the frequent drops in current and to improve the resolution in the separation of analytes in anionic form, a programmed nebulizing gas pressure (PNP) was applied along the analysis.Extraction of isoflavones from soy drinks was carried out by liquid–liquid extraction using ethanol. The proposed extraction procedure is simple, efficient, and affords reproducible results. Quantification of the isoflavones in soy drinks using the external standard method did not produce good results; therefore, both internal standard and standard addition quantification methods were used, obtaining significantly similar results. The detection limits found were lower than 3.2μgL⁻¹.

Keywords: Capillary electrophoresis; Electrospray mass spectrometry; Isoflavones; Soy drink

Capillary electrophoretic studies on displacement and proteolytic cleavage of surface bound oligohistidine peptide on quantum dots by Jianhao Wang; Jiang Xia (pp. 120-127).

Display Omitted► Capillary electrophoresis reveals details in QD–oligohistidine peptide binding. ► An ordered assembly of peptides on QDs was revealed. ► Intermediates of QD–peptide binding were found. ► Detailed displacement kinetics was revealed. ► Proteolysis of surface ligands causes mobility shift and peak broadening in CE.Subtle changes in the chemical structure or the composition of surface bound ligands on quantum dots (QDs) remain difficult to detect. Here we describe a facile setup for fluorescence detection coupled capillary electrophoresis (CE-FL) and its application in monitoring ligand displacement on QDs through metal-affinity driven assembly. We also describe the use of CE-FL to monitor amide bond cleavage by a specific protease, based on Förster resonance energy transfer (FRET) between Cy5 and QDs spaced by a hexahistidine peptide (H6–Cy5). CE-FL allowed separation of unbound QDs and ligand bound QDs and also revealed an ordered assembly of H6–Cy5 on QDs. In a ligand displacement experiment, unlabeled hexahistidine peptide gradually displaced surface bound H6–Cy5 until finally reaching equilibrium. The displacement intermediates were clearly separated on CE-FL. Proteolytic cleavage of surface bound H6–Cy5 by thrombin was monitored by CE-FL through mobility shift, peak broadening, and FRET changes. Enzymatic parameters thus obtained were comparable with those measured by fluorescence spectroscopy.

Keywords: Quantum dots; Capillary electrophoresis; Förster resonance energy transfer; Ligand displacement; Protease peptide

Corrigendum to “Implications of partial tryptic digestion in organic–aqueous solvent systems for bottom-up proteome analysis” [Anal. Chim. Acta (2011) 194–203] by Mark J. Wall; Andrew M.J. Crowell; Gordon A. Simms; Graham H. Carey; Fang Liu; Alan A. Doucette (pp. 128-128).

Sections

Personal tools

Analytica Chimica Acta (v.709, #)

Sections

Personal tools

Local resources

Analytica Chimica Acta (v.709, #)