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Analytica Chimica Acta (v.728, #)

Editorial Board (pp. iii).

Disposable screen-printed sensors modified with bismuth precursor compounds for the rapid voltammetric screening of trace Pb(II) and Cd(II) by Nikolitsa Lezi; Anastasios Economou; Panagiotis A. Dimovasilis; Pantelis N. Trikalitis; Mamas I. Prodromidis (pp. 1-8).

.Display Omitted► Novel screen-printed sensors loaded with bismuth precursors have been fabricated. ► These are used for the rapid screening of Pb(II), Cd(II) by stripping voltammetry. ► During the accumulation step, the Bi(III) precursors are reduced to metallic bismuth. ► Bismuth citrate at a 6% (w/w) offered the highest sensitivity and reproducibility.In this article, a study of novel screen-printed electrodes bulk-modified with five potential bismuth precursor compounds (bismuth citrate, bismuth titanate, bismuth oxide, bismuth aluminate and bismuth zirconate) is presented for the determination of Cd(II) and Pb(II) by anodic stripping voltammetry. During the electrolytic deposition step, the precursor was reduced and served as the source of bismuth. Different key parameters were investigated in detail such as the nature of the bismuth precursor compound, the precursor content in the carbon ink, the polarisation range of the sensors, the supporting electrolyte, the stripping waveform, the deposition time, the deposition potential and the long-term stability of the sensors under continuous use. Using bismuth citrate as the precursor, the limit of detection was 0.9μgL⁻¹ for Pb(II) and 1.1μgL⁻¹ for Cd(II). The reproducibility on the same sensor (expressed as % relative standard deviation, ( n=8)) was 5.4% for Pb(II) and 7.2% for Cd(II) at the 20μgL⁻¹ level. Finally, the sensors were applied to the determination of Cd(II) and Pb(II) in water samples.

Keywords: Screen-printed electrodes; Bismuth precursors; Cd(II) and Pb(II); Anodic stripping voltammetry

A binderless, covalently bulk modified electrochemical sensor: Application to simultaneous determination of lead and cadmium at trace level by Raghu Gunigollahalli Kempegowda; Pandurangappa Malingappa (pp. 9-17).

Display Omitted► Proposed sensor is a new type of binderless covalent bulk modified electrode. ► Surface can be easily renewed by simple mechanical polishing using emery sheets. ► Free from modifier leaching during electrochemical measurements. ► Provides long term storage stability with good reproducibility. ► Nanomolar level detection limit achieved with selectivity.A new type of covalent binderless bulk modified electrode has been fabricated and used in the simultaneous determination of lead and cadmium ions at nanomolar level. The modification of graphitic carbon with 4-amino salicylic acid was carried out under microwave irradiation through the amide bond formation. The electrochemical behavior of the fabricated electrode has been carried out to decipher the interacting ability of the functional moieties present on the modifier molecules toward the simultaneous determination of Pb²⁺ and Cd²⁺ ions using cyclic and differential pulse anodic stripping voltammetry. The possible mode of interaction of functional groups with metal ions is proposed based on the p Ka values of the modifier functionalities present on the surface of graphitic carbon particles. The analytical utility of the proposed sensor has been validated by measuring the lead and cadmium content from pretreated waste water samples of lead acid batteries.

Keywords: Graphitic carbon; 4-Aminosalicylic acid; Binderless bulk modified electrode; Lead; Cadmium; Battery waste water

Poly( o-phenylenediamine)-carried nanogold particles as signal tags for sensitive electrochemical immunoassay of prolactin by Huafeng Chen; Yuling Cui; Bing Zhang; Bingqian Liu; Guonan Chen; Dianping Tang (pp. 18-25).

Display Omitted► This work designs a sensitive and feasible sandwich-type electrochemical immunoassay system for determination of prolactin. ► A novel class of redox-active molecular tags, poly( o-phenylenediamine)-carried nanogold particles. ► A lower detection limit of the electrochemical immunosensor than that of commercially available ELISAs.A novel class of redox-active molecular tags, poly( o-phenylenediamine)-carried nanogold particles (GPPDs), was first synthesized and functionalized with horseradish peroxidase-anti-prolactin conjugates (HRP-anti-PRL). Thereafter, a specific sandwich-type electrochemical immunoassay was designed for determination of prolactin (PRL) by using GPPD-labeled HRP-anti-PRL conjugates as molecular tags on anti-PRL antibody-modified glassy carbon electrode. Compared with pure gold nanoparticles and poly( o-phenylenediamine) microspheres, the as-prepared GPPDs increased the surface coverage of the nanostructures, and enhanced the immobilization amount of biomolecules. Several labeling protocols compromising GPPD-labeled HRP-anti-PRL, nanogold particles-labeled HRP-anti-PRL and poly( o-phenylenediamine) microspheres-labeled HRP-anti-PRL, were investigated for detection of PRL, and improved analytical features were obtained with the GPPD-based strategy. With the GPPD labeling method, dependence of the electrochemical signals on the incubation time and pH of the assay solution were also studied. The strong attachment of HRP-anti-PRL to the GPPDs resulted in a good repeatability and intermediate reproducibility down to 9.8%. The dynamic concentration range spanned from 0.5 to 180ngmL⁻¹ PRL with a detection limit of 0.1ngmL⁻¹ at the 3 S_blank level. No significant differences at the 95% confidence level were encountered in the analysis of 10 spiked blank cattle serum samples between the developed immunoassay and enzyme-linked immunosorbent assay method for determination of PRL.

Keywords: Electrochemical immunoassay; Nanogold-assembled poly(; o; -phenylenediamine) microspheres; Nanolabels; Prolactin

High-throughput quantification of palladium in water samples by ion pair based-surfactant assisted microextraction by Yadollah Yamini; Morteza Moradi; Elham Tahmasebi (pp. 26-30).

Display Omitted► A method named ion pair based surfactant assisted microextraction was developed. ► The method was applied for extraction of Pd(II) in presence of cationic surfactants. ► The extracted Pd(II) was determined by ICP-OES. ► Theoretical aspects of ion pair based surfactant assisted extraction was discussed.A novel method for the determination of palladium as a metal ion model was developed by ion pair based surfactant-assisted microextraction (IP-SAME) and inductively coupled plasma-optical detection (ICP-OES). In this methodology, a cationic surfactant was used in extraction process. It has two fundamental functions: (1) the formation of an emulsified phase and (2) the ion pair formation with Pd(II) in the presence of iodide ions and makingPdI42− extractable into organic phase (active microextraction). The effective parameters on the extraction recovery such as the types of extraction solvent and the surfactant, surfactant concentration, KI amount and HCl concentration of the sample were investigated and optimized. In the proposed approach, tetradecyl trimethyl ammonium bromide (TTAB) was used as emulsifier and ion pairing agent, and 1-octanol was selected as extraction solvent. Under the optimum conditions, the enhancement factor as large as 146 was obtained. The detection limit for palladium was 0.2μgL⁻¹, and the relative standard deviation (RSD) was 4.1% ( n=5, C=10.0μgL⁻¹). The proposed method was applied for extraction and determination of palladium in different water samples.

Keywords: Ion pair based surfactant-assisted microextraction; Palladium; Inductively coupled plasma-optical emission spectrometry; Water samples

Air-assisted liquid–liquid microextraction method as a novel microextraction technique; Application in extraction and preconcentration of phthalate esters in aqueous sample followed by gas chromatography–flame ionization detection by Mir Ali Farajzadeh; Mohammad Reza Afshar Mogaddam (pp. 31-38).

Display Omitted► A simple air-assisted liquid–liquid microextraction (AALLME) method has been developed for the first time. ► Enrichment factors of the proposed method were higher than those of conventional DLLME. ► The new method avoided using disperser solvent. ► Short extraction time of the present method relative to the other methods was another advantage of this method.A novel microextraction technique, air-assisted liquid–liquid microextraction (AALLME), which is a new version of dispersive liquid–liquid microextraction (DLLME) method has been developed for extraction and preconcentration of phthalate esters, dimethyl phthalate (DMP), diethyl phthalate (DEP), di-iso-butyl phthalate (DIBP), di-n-butyl phthalate (DNBP), and di-2-ethylhexyl phthalate (DEHP), from aqueous samples prior to gas chromatography–flame ionization detection (GC–FID) analysis. In this method, much less volume of an organic solvent is used as extraction solvent in the absence of a disperser solvent. Fine organic droplets were formed by sucking and injecting of the mixture of aqueous sample solution and extraction solvent with a syringe for several times in a conical test tube. After extraction, phase separation was performed by centrifugation and the enriched analytes in the sedimented phase were determined by GC–FID. Under the optimum extraction conditions, the method showed low limits of detection and quantification between 0.12–1.15 and 0.85–4ngmL⁻¹, respectively. Enrichment factors (EFs) and extraction recoveries (ERs) were in the ranges of 889–1022 and 89–102%, respectively. The relative standard deviations (RSDs) for the extraction of 100ngmL⁻¹ and 500ngmL⁻¹ of each phthalate ester were less than 4% for intra-day ( n=6) and inter-days ( n=4) precision. Finally some aqueous samples were successfully analyzed using the proposed method and three analytes, DIBP, DNBP and DEHP, were determined in them at ngmL⁻¹ level.

Keywords: Abbreviations; AALLME; air-assisted liquid–liquid microextraction; DLLME; dispersive liquid–liquid microextraction; PEs; phthalate esters; GC; gas chromatography; FID; flame ionization detectorAir-assisted liquid–liquid microextraction; Phthalate esters; Gas chromatography; Flame ionization detection

Development of a dedicated peptide tandem mass spectral library for conservation science by Wim Fremout; Maarten Dhaenens; Steven Saverwyns; Jana Sanyova; Peter Vandenabeele; Dieter Deforce; Luc Moens (pp. 39-48).

Display Omitted► Sequence library search is not working for species determination of animal glues. ► Spectral library matching is proposed as an alternative approach. ► A dedicated spectral library for conservation science is developed. ► This methodology was successfully applied on paint samples.In recent years, the use of liquid chromatography tandem mass spectrometry (LC–MS/MS) on tryptic digests of cultural heritage objects has attracted much attention. It allows for unambiguous identification of peptides and proteins, and even in complex mixtures species-specific identification becomes feasible with minimal sample consumption. Determination of the peptides is commonly based on theoretical cleavage of known protein sequences and on comparison of the expected peptide fragments with those found in the MS/MS spectra. In this approach, complex computer programs, such as Mascot, perform well identifying known proteins, but fail when protein sequences are unknown or incomplete. Often, when trying to distinguish evolutionarily well preserved collagens of different species, Mascot lacks the required specificity. Complementary and often more accurate information on the proteins can be obtained using a reference library of MS/MS spectra of species-specific peptides. Therefore, a library dedicated to various sources of proteins in works of art was set up, with an initial focus on collagen rich materials. This paper discusses the construction and the advantages of this spectral library for conservation science, and its application on a number of samples from historical works of art.

Keywords: Protein; Tryptic peptide; LC–MS/MS; MS library; Cultural heritage

A comparative study of glycoprotein concentration, glycoform profile and glycosylation site occupancy using isotope labeling and electrospray linear ion trap mass spectrometry by Chih-Yu Lin; Yi-Chun Ma; Pei-Jing Pai; Guor-Rong Her (pp. 49-56).

Display Omitted► Concentration, site occupancy and glycoform variation can be differentiated. ► Glycopeptides and peptides were stable isotope labeled and analyzed by ESI-MS. ► Nonglycosylated peptide provided glycoprotein concentration variation. ► Glycoform variation was obtained by comparing d₀ and d₄ labeled glycopeptides. ► The variation of glycosylation site occupancy could be calculated.A strategy is presented for comparative analysis of glycoproteins in which the variation of protein concentration, variation of glycosylation site occupancy and variation of glycoform profile can be determined. A comparative study was performed using stable isotope labeling of glycopeptides and peptides by formaldehyde-H₂ and formaldehyde-D₂ and analysis by ESI-MS analysis. The relative intensity of the nonglycosylated peptide provided information about protein concentration variation. Variation of the glycoform profile was obtained by comparing the glycoform profile of d₀- and d₄-dimethyl labeled glycopeptides. By knowing the variation of protein concentration and the variation of glycoform profile, the variation of glycosylation site occupancy could be calculated. The utility of the proposed strategy was demonstrated with ribonuclease B with different protein concentrations, different levels of glycosylation site occupancy and different glycoform profiles.

Keywords: Glycoprotein quantitation; Glycosylation site occupancy; Glycan profile; Electrospray mass spectrometry; Isotope labeling

An infrared spectroscopic based method for mercury(II) detection in aqueous solutions by Asela Chandrasoma; Amer Al Abdel Hamid; Alice E. Bruce; Mitchell R.M. Bruce; Carl. P. Tripp (pp. 57-63).

Display Omitted► Solid phase extraction coupled with FTIR spectroscopy selectively detects Hg(II)(aq). ► The method is selective vs. thiophilic ions such as Pb(II), Cd(II), Fe(III), and Zn(II). ► The method is also selective vs. metals such as Ni(II), Mn(II), Co(II), and Cu(II). ► Method of detection limit (MDL) for the SPE/IR is 5μg of Hg(II)cm⁻². ► The study identifies mass transport issues relevant for further development.A new method that uses solid phase extraction (SPE) coupled with FTIR spectroscopy to detect Hg(II) in aqueous samples is described. The technique is envisioned for on-site, field evaluation rather than lab-based techniques. This paper presents the “proof of principle” of this new approach toward measurements of Hg(II) in water and identifies mass transport issues that would need to be overcome in order to migrate from a lab based method to field operation. The SPE material supported on a Si wafer is derivatized with an acylthiosemicarbazide, which undergoes a reaction in the presence of aqueous Hg(II) to form an oxadiazole ring. The progress of the reaction is monitored by IR spectroscopy. Following EPA guidelines, the method of detection limit (MDL) for the SPE/IR was 5μg of Hg(II)cm⁻². In a 1L sample and a 1cm² Si wafer, this translates to a detection limit of 5ppb. This system shows a high selectivity toward aqueous Hg(II) over other thiophilic heavy metal ions such as Pb(II), Cd(II), Fe(III), and Zn(II) and other metal ions such as Ni(II), Mn(II), Co(II), Cu(II), In(III), Ru(III), Na(I), and Ag(I) in aqueous solutions.

Keywords: Infrared spectroscopy; Mercury(II); Detection; Solid phase extraction; Sensors

Label-free detection of C-reactive protein using reflectometric interference spectroscopy-based sensing system by Hyung Woo Choi; Yasuhiko Sakata; Yoshikazu Kurihara; Tooru Ooya; Toshifumi Takeuchi (pp. 64-68).

Display Omitted► A new RIfS-based label-free biosensing system for C-reactive protein was developed. ► Silicon-based inexpensive chips and the simple optical setup were employed. ► Owing to the TMS treatment and the use of protein A, the sensitivity was enhanced. ► It can be applied to other target as a substitute of SPR-based expensive sensors.Reflectometric interference spectroscopy (RIfS) is a label-free, time-resolved technique, and suitable for detecting antibody–antigen interaction. This work describes a continuous flow biosensor for C-reactive protein (CRP), involving an effective immobilization method of a monoclonal antibody against CRP (anti-CRP) to achieve highly sensitive RIfS-based detection of CRP. The silicon nitride-coated silicon chip (SiN chip) for the RIfS sensing was first treated with trimethylsilylchloride (TMS), followed by UV-light irradiation to in situ generation of homogeneous silanols on the surface. Following amination by 3-aminopropyltriethoxysilane, carboxymethyldextran (CMD) was grafted, and subsequently, protein A was immobilized to create the oriented anti-CRP surface. The immobilization process of protein A and anti-CRP was monitored with the RIfS system by consecutive injections of an amine coupling reagent, protein A and anti-CRP, respectively, to confirm the progress of each step in real time. The sensitivity was enhanced when all of the processes were adopted, suggesting that the oriented immobilization of anti-CRP via protein A that was coupled with the grafted CMD on the aminated surface of TMS-treated SiN chip. The feasibility of the present sensing system was demonstrated on the detection of CRP, where the silicon-based inexpensive chips and the simple optical setup were employed. It can be applied to other target molecules in various fields of life science as a substitute of surface plasmon resonance-based expensive sensors.

Keywords: Reflectometric interference spectroscopy (RIfS); C-reactive protein (CRP); Protein A; Carboxymethyl dextran (CMD); Label-free biosensing

Comparative study of different alcohol sensors based on Screen-Printed Carbon Electrodes by Estefanía Costa Rama; Julien Biscay; María Begoña González García; A. Julio Reviejo; José Manuel Pingarrón Carrazón; Agustín Costa García (pp. 69-76).

Display Omitted► We developed three alcohol sensors using screen-printed carbon/mediator electrodes. ► Better results were obtained with screen-printed carbon/Co-phthalocyanine electrodes. ► The sensor is fabricated in a simple way resulting in good sensitivity and stability. ► Results obtained in real samples have good accuracy and precision comparing with GC.Different very simple single-use alcohol enzyme sensors were developed using alcohol oxidase (AOX) from three different yeast, Hansenula sp., Pichia pastoris and Candida boidinii, and employing three different commercial mediator-based Screen-Printed Carbon Electrodes as transducers. The mediators tested, Prussian Blue, Ferrocyanide and Co-phthalocyanine were included into the ink of the working electrode. The procedure to obtain these sensors consists of the immobilization of the enzyme on the electrode surface by adsorption. For the immobilization, an AOX solution is deposited on the working electrode and left until dried (1h) at room temperature. The best results were obtained with the biosensor using Screen-Printed Co-phthalocyanine/Carbon Electrode and AOX from Hansenula sp. The reduced cobalt–phthalocyanine form is amperometrically detected at +0.4V (vs. Ag pseudo reference electrode). This sensor shows good sensitivity (1211nAmM⁻¹), high precision (2.1% RSD value for the slope value of the calibration plot) and wide linear response (0.05–1.00mM) for ethanol determination. The sensor provides also accurate results for ethanol quantification in alcoholic drinks.

Keywords: Abbreviations; AOX; alcohol oxidase; SPPBCEs; Screen-Printed Prussian Blue/Carbon Electrodes; SPFCEs; Screen-Printed Ferrocyanide/Carbon Electrodes; SPCPCEs; Screen-Printed Co-phthalocyanine/Carbon ElectrodesFerrocyanide; Prussian Blue; Co-phthalocyanine; Screen-Printed Carbon Electrode; Alcohol oxidase

A ratiometric fluorescence sensor for Be²⁺ based on Beryllon II/layered double hydroxide ultrathin films by Xiaolan Ji; Wenying Shi; Shitong Zhang; Min Wei; David G. Evans; Xue Duan (pp. 77-85).

This paper reports the fabrication of Beryllon II/layered double hydroxide ultrathin films via the layer-by-layer assembly technique, which can be used as a ratiometric fluorescence chemosensor for Be²⁺ with good repeatability, high stability and excellent selectivity.Display Omitted► A ratiometric fluorescence sensor for Be²⁺ was fabricated by LBL method. ► The chemosensor shows a broad linear response range and a low detection limit. ► The sensor exhibits a high stability and excellent selectivity toward Be²⁺. ► The chemosensor can be easily regenerated and reused.A ratiometric fluorescence sensor for Be²⁺ has been fabricated via alternate assembly of 2-(3,6-disulfo-8-hydroxynaphthylazo)-1,8-dihydroxynaphthalene-3,6-disulfonate (Beryllon II) and MgAl-LDH nanosheets on quartz substrates using the layer-by-layer (LBL) deposition technique. UV–vis absorption and the fluorescence emission spectroscopy indicate a stepwise and regular growth of the Beryllon II/LDH UTFs upon increasing deposition cycle. The film of Beryllon II/LDH possesses a periodic layered structure perpendicular to the substrate revealed by X-ray diffraction and scanning electron microscopy. Atomic force microscopy images show that the film surface is continuous and uniform. The Beryllon II/LDH UTFs display ratiometric fluorescence response for Be²⁺ with a linear response range in 1.0×10⁻⁷–1.9×10⁻⁶molL⁻¹ and a detection limit of 4.2×10⁻⁹molL⁻¹. Furthermore, the ratiometric sensor exhibits good repeatability, high stability (thermal, storage and mechanical) as well as excellent selectivity toward Be²⁺. XPS and Raman measurements demonstrate that the specific response of the sensor is attributed to the coordination between Be²⁺ and Beryllon II in the UTF. The Beryllon II/LDH UTFs in this work can be potentially used as a chemosensor for the detection of Be²⁺ in the environmental and biomedical field.

Keywords: Beryllon II; Layered double hydroxide; Ratiometric fluorescence sensor; Ultrathin film; Beryllium

Dynamic labeling of diagnostically significant microbial cells in cerebrospinal fluid by red chromophoric non-ionogenic surfactant for capillary electrophoresis separations by Marie Horká; Filip Růžička; Anna Kubesová; Karel Šlais (pp. 86-92).

Display Omitted► We found method for rapid detection of tens cells of labeled microbes in 1mL of sample. ► Red non-ionogenic surfactant was prepared. ► Filtration cartridge was coupled with CIEF. ► Method was tested on spiked CSF.During bacterial infections of the central nervous system the number of microorganisms in the cerebrospinal fluid is often ranging from few up to hundreds of cells per milliliter. The electrophoretic techniques with the UV-detection reach a detection limit for whole cells of approximately 10⁷cells per milliliter. The coupling of the filtration cartridge with capillary isoelectric focusing can improve the detection limit by four orders of magnitude. In order to improve the detection limit the red non-ionogenic surfactant 1-[[4-(phenylazo)phenyl]azo]-2-hydroxy-3-naphthoic acid polyethylene glycol ester, PAPAN 1000, has been prepared and used for the dynamic labeling of analytes before filtration of the sample with a concentration modulation in the analysis of proteins or microorganisms. Values of isoelectric points of labeled analytes have been calculated using p I markers detectable at 515nm and have been found comparable with p I of the native compounds. Minimum detectable amounts of proteins and microorganisms were lower than nanograms and a hundred labeled cells, respectively. The introduced method, coupling of the filtration cerebrospinal fluid spiked with microorganisms and labeled by PAPAN, facilitates their rapid CIEF separation in the pH gradient pH range of 2–5 at their clinically important level 10¹ to 10²cells per milliliter.

Keywords: CZE and CIEF; Preconcentration; Microorganisms; Cerebrospinal fluid; Colored non-ionogenic surfactant; Dynamic modification

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Analytica Chimica Acta (v.728, #)