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Analytica Chimica Acta (v.699, #1)

Editorial Board (pp. iii).

Detection of multiple cardiac markers with an integrated acoustic platform for cardiovascular risk assessment by Konstantinos Mitsakakis; Electra Gizeli (pp. 1-5).

Display Omitted► A Surface Acoustic Wave platform was used for multiple cardiac marker detection. ► Multiplicity achieved through dividing device surface with microfluidic channels. ► Four biomarkers detected on the same biochip: CK-MB, CRP, D-dimer, and PAPP-A. ► Analytical curves directly correlate acoustic signal to biomarkers’ concentration. ► High selectivity achieved during detection of one biomarker from a mixture.This work describes the application of a newly emerged biosensing configuration incorporating a Surface Acoustic Wave device integrated with a multi-channel microfluidic module for the rapid and efficient analysis of cardiac markers. The examined cardiac markers of creatine kinase MB (CK-MB), cardiac reactive protein (CRP), D-dimer and pregnancy-associated plasma protein A (PAPP-A), comprise a group of both established and emerging heart disease proteins, that has never been probed before with any kind of biochip-related platform. The four markers were successfully detected; kinetics and affinity studies on their interactions with the surface immobilized antibodies are also presented. A concentration detection limit of less than 1nM was achieved, with a dynamic range of more than two orders of magnitude, covering some of the pathological and healthy areas of interest. Mixtures of biomarkers applied to the device surface were used to prove the specificity of each binding event and investigate the microsystem's performance in the presence of complex fluids, towards future utilization with real samples. The simplicity and multiplexing ability of the integrated platform render the system ideal as a potential diagnostic tool for cardiovascular risk assessment, where simultaneous analysis of various protein markers is required.

Keywords: Acoustic biosensors; Cardiac markers; Diagnostics; Microfluidics; Multi-sample sensing

Using dried-droplet laser ablation inductively coupled plasma mass spectrometry to quantify multiple elements in whole blood by Hui-Fang Hsieh; Wei-Shan Chang; Yi-Kong Hsieh; Chu-Fang Wang (pp. 6-10).

Display Omitted► A simple procedure for the direct analysis and determination of multiple elements in dried blood samples on a filter membrane using LA-ICP-MS. ► A major advantage of this method is the small amount of sample required—only 0.5μL, which is readily obtained from a finger or heel stick. ► Simultaneously quantified 13 elements in whole blood. ► An aqueous standard solution can be used as an alternative calibration standard.This paper describes a simple procedure for the direct analysis and determination of multiple elements in dried blood samples on a filter membrane using laser ablation coupled with inductively coupled plasma mass spectrometry (LA-ICP-MS). With this technique, we simultaneously quantified 13 elements in whole blood: Be, Mn, Co, Ni, Tl, Bi, Sb, Pb, Cu, Zn, Ba, Mg, and Cd. The measured accuracies was in agreement with the Seronorm CRM certified values, except for Mn, Zn, Ba and Cd, which presented absolute differences higher than the expanded uncertainty for these elements. The within-run precision was less than 5.7% (relative standard deviation, RSD), except for the analyses of Be, and Mn (8.6% and 11.1%, respectively). The reproducibility (between-run precision) was calculated in terms of the RSD obtained for 12 analyses (i.e., four replicates of each sample in three analytical runs). Apart from Be, Mn, and Zn, the reproducibilities of all the elements listed above ranged between 4.0% and 8.5%. In contrast, for Cd, the concentration obtained was significantly different from the certified value; analyses of this element exhibited low reproducibility. Applying the matrix-matched calibration method, the accuracy for Cd measured was in agreement with both SRM966 and BCR 635; thus, matrix-matched calibration is a practical means of overcoming matrix-enhancement effects for the quantification of Cd. Sample throughput (ca. 5min per sample) made it possible to rapidly screen a larger number of samples relative to other techniques that require time-consuming sample preparation steps (e.g., removal of a portion of the solid sample or digestion).

Keywords: Blood; Multiple elements; Direct analysis; Laser ablation; Inductively coupled plasma mass spectrometry

Non-chromatographic screening procedure for arsenic speciation analysis in fish-based baby foods by using electrothermal atomic absorption spectrometry by Ignacio López-García; Marisol Briceño; Manuel Hernández-Córdoba (pp. 11-17).

.Display Omitted► Arsenic in fish-based food samples can be determined without the need of a dissolution stage. ► Speciation of the main forms of arsenic in fish-based baby foods does not require chromatography. ► The behavior of arsenic compounds in ETAAS strongly depends on the chemical modifier used.A procedure for the speciation analysis of arsenic in fish-based baby foods is presented. Inorganic arsenic, methylarsonic acid (MA), dimethylarsinic acid (DMA) and arsenobetaine (AB) were determined by electrothermal atomic absorption spectrometry (ETAAS) using suspensions prepared in a 0.01molL⁻¹ tetramethylammonium hydroxide (TMAH) solution. Speciation is based on the use of three different chemically modified ETAAS atomizers to obtain the analytical signals. Using a palladium salt as the chemical modifier, the signal corresponding to the total arsenic concentration is obtained. When palladium is replaced by Ce(IV), the signal is solely due to inorganic arsenic (III and V)+MA. If no signal is obtained in this latter case, it is possible to distinguish between DMA and AB using a zirconium coated atomizer. The signal obtained in this way is due solely to DMA, and the concentration of AB can be obtained by the difference with the total arsenic content. Determinations by ETAAS require the use of the standard additions method. The limits of detection for the determination of AB, DMA and inorganic arsenic (+MA) are 15, 25 and 50ngg⁻¹ expressed as arsenic, respectively. These detection limits are good enough for the procedure to be appropriate for the rapid determination of these compounds, avoiding extraction processes and/or chromatographic separations. Data for commercial samples, as well as for four standard reference materials, are given.

Keywords: ETAAS; Arsenic; Arsenobetaine; Speciation; Suspensions; Foods; Baby foods

A new and efficient variable selection algorithm based on ant colony optimization. Applications to near infrared spectroscopy/partial least-squares analysis by Franco Allegrini; Alejandro C. Olivieri (pp. 18-25).

Display Omitted► We developed a new variable selection algorithm combining ant colony optimization with a Monte Carlo approach. ► We applied it to PLS regression analysis of near infrared spectroscopic experimental data. ► Improved analytical figures were obtained upon wavelength selection.A new variable selection algorithm is described, based on ant colony optimization (ACO). The algorithm aim is to choose, from a large number of available spectral wavelengths, those relevant to the estimation of analyte concentrations or sample properties when spectroscopic analysis is combined with multivariate calibration techniques such as partial least-squares (PLS) regression. The new algorithm employs the concept of cooperative pheromone accumulation, which is typical of ACO selection methods, and optimizes PLS models using a pre-defined number of variables, employing a Monte Carlo approach to discard irrelevant sensors. The performance has been tested on a simulated system, where it shows a significant superiority over other commonly employed selection methods, such as genetic algorithms. Several near infrared spectroscopic experimental data sets have been subjected to the present ACO algorithm, with PLS leading to improved analytical figures of merit upon wavelength selection. The method could be helpful in other chemometric activities such as classification or quantitative structure-activity relationship (QSAR) problems.

Keywords: Ant colony optimization; Variable selection; Near infrared spectroscopy; Partial least-squares regression

Classification of amino acids and oligopeptides with the use of multi-mode chemical images obtained with ion selective electrode array by Patrycja Ciosek; Martyna Jańczyk; Wojciech Wróblewski (pp. 26-32).

Display Omitted► In thos work multi-mode approach for amino acids and oligopeptides analysis was proposed. ► Potentiometric sensor array was used during the titration of aminoacids and oligopeptides. ► The increase of information gained during the titration and multi-mode analysis leads to the lowering of classification errors.The analysis of amino acids and oligopeptides as important bioanalytes is a significant task in medical diagnostics and proteomic research and currently it is based on chromatographic and electrophoretic methods. In this paper, an approach based on sensor array coupled with titration is proposed for effective recognition of 5 amino acids and 4 oligopeptides. It is shown, that the increase of information gained during measurements of sensors’ signals in various pH allows for capturing more data on interaction of amino acids and oligopeptides with various polymeric membranes of potentiometric electrodes used in the array, and that leads to the lowering of classification errors in partial least squares analysis.

Keywords: Amino acids; Oligopeptides; Sensor array; Electronic tongue; Partial least squares-discriminant analysis

The use of digital simulation to improve the cyclic voltammetric determination of rate constants for homogeneous chemical reactions following charge transfers by J.D. Mozo; J. Carbajo; J.C. Sturm; L.J. Núñez-Vergara; R. Moscoso; J.A. Squella (pp. 33-43).

Cyclic voltammetry (CV) is a very useful electrochemical tool used to study reaction systems that include chemical steps that are coupled to electron transfers. This type of system generally involves the chemical reaction of an electrochemically generated free radical. Published methods exist that are used to determine the kinetics of electrochemically initiated chemical reactions from the measurements of the peak current ratio ( i_pa/ i_pc) of a cyclic voltammogram. The published method requires working curves to relate a kinetic parameter to the peak current ratio.In the presented work, a digital simulation package was used to obtain improved working curves for specific working conditions. The curves were compared with the published results for the first- and second-order chemical reactions following the charge transfer step mechanisms.According to the presented results, the previously published working curve is reliable for a mechanism with a first-order chemical reaction; however, a change in the switching potential requires a recalculation of the curve. In the case of mechanisms with a second-order step (dimerisation and disproportionation), several different views exist on how the second-order chemical term should be expressed so that different values of the constant are obtained. Parameters such as electrode type, electrode area, electroactive species concentration, switching potential, scan rate and method for peak current ratio calculation modify the working curves and must always be specified.We propose a standardised method to obtain the most reliable kinetic constant values.The results of this work will permit researchers who handle simulation software to construct their own working curves. Additionally, those who do not have the simulation software could use the working curves described here.The revelations of the presented experiments may be useful to a broad chemistry audience because this study presents a simple and low-cost procedure for the study of free radicals that otherwise should be studied with more sophisticated and expensive techniques, such as ESR or pulse radiolysis.

Keywords: Simulation; Cyclic voltammetry; Working curves; Coupled reactions

Graphene-based immunosensor for electrochemical quantification of phosphorylated p53 (S15) by Yunying Xie; Aiqiong Chen; Dan Du; Yuehe Lin (pp. 44-48).

. A new graphene-based immunosensor for electrochemical quantification of phosphorylated p53 on serine 15 (phospho-p53¹⁵) was proposed. This easily fabricated immunosensor provides a potential tool for analysis of other biomarkers.Display Omitted► A new graphene-based immunosensor for electrochemical quantification of phosphorylated p53 on serine 15 (phospho-p53¹⁵) was proposed. ► Graphene served as sensor platform greatly increased detection sensitivity. ► This easily fabricated immunosensor provides a potential tool for analysis of other biomarkers.We reported a graphene-based immunosensor for electrochemical quantification of phosphorylated p53 on serine 15 (phospho-p53¹⁵), a potential biomarker of gamma-radiation exposure. The principle is based on sandwich immunoassay and the resulting immunocomplex is formed among phospho-p53 capture antibody, phospho-p53¹⁵ antigen, biotinylated phospho-p53¹⁵ detection antibody and horseradish peroxidase (HRP)-labeled streptavidin. The introduced HRP results in an electrocatalytic response to reduction of hydrogen peroxide in the presence of thionine. Graphene served as sensor platform not only promotes electron transfer, but also increases the surface area to introduce a large amount of capture antibody, thus increasing the detection sensitivity. The experimental conditions including blocking agent, immunoreaction time and substrate concentration have been optimized. Under the optimum conditions, the increase of response current is proportional to the phospho-p53¹⁵ concentration in the range of 0.2–10ngmL⁻¹, with the detection limit of 0.1ngmL⁻¹. The developed immunosensor exhibits acceptable stability and reproducibility and the assay results for phospho-p53¹⁵ are in good correlation with the known values. This easily fabricated immunosensor provides a new promising tool for analysis of phospho-p53¹⁵ and other phosphorylated proteins.

Keywords: Phosphorylated p53; Graphene; Immunosensor; Electrochemistry

Accurate quantification of polycyclic aromatic hydrocarbons in dust samples using microwave-assisted solvent extraction combined with isotope-dilution mass spectrometry by Nobuyasu Itoh; Akihiro Fushimi; Takashi Yarita; Yoshie Aoyagi; Masahiko Numata (pp. 49-56).

.Display Omitted► We applied MAE–IDMS for accurate quantification of PAHs in dust samples. ► Both partitioning and isotopic equilibria can be achieved using this technique. ► MAE–IDMS can provide accurate concentrations even if extraction efficiencies were low. ► Characteristics of samples strongly affected for low extraction efficiencies of PAHs.For accurate quantification of polycyclic aromatic hydrocarbons (PAHs) in dust samples, we investigated the use of microwave-assisted solvent extraction (MAE) combined with isotope-dilution mass spectrometry (IDMS) using deuterium-labelled PAHs (D-PAHs). Although MAE with a methanol/toluene mixture (1:3 by volume) at 160°C for 40min was best for extracting PAHs from tunnel dust among examined, the recovery yields of D-PAHs decreased with increasing molecular weight (<40% for MW≥264; that of deuterium-labelled indeno[123-cd]pyrene (D-IcdP) was only 7.1%). Although the residues were extracted a second time, the observed concentrations did not change dramatically (<5%), and the recovery yields of heavier D-PAHs (i.e., MW≥264) were approximately half of those of the first extract, including D-IcdP (3.4%). These results suggest that both partitioning and isotopic equilibria of PAHs and D-PAHs between sample and solvent were achieved for extractable heavier PAHs under the condition. Thus, the observed concentrations of PAHs obtained by MAE–IDMS were reasonable, even though recovery yields of D-PAHs were <50%. From the results of carbon analyses and extractable contents, lower recovery yields of D-PAHs from the tunnel dust were due to a large content of char with low extractable contents.

Keywords: Polycyclic aromatic hydrocarbons (PAHs); Microwave-assisted solvent extraction (MAE); Isotope-dilution mass spectrometry (IDMS); Tunnel dust

Development of a gas chromatography–mass spectrometry method for the determination of pesticides in gaseous and particulate phases in the atmosphere by E. Borrás; P. Sánchez; A. Muñoz; L.A. Tortajada-Genaro (pp. 57-65).

Display Omitted► An efficient method for the determination of sixteen pesticides in atmospheric samples. ► XAD-4 is an interesting support for collecting gas-phase pesticides, with similar performances than the conventional XAD-2. ► The ultrasonic extraction is cheaper, less aggressive and time-consuming with excellent analytical parameters. ► The method has been successfully tested by using high volume atmospheric simulation chamber and field campaigns.A reliable multi-residue method for determining gaseous and particulate phase pesticides in atmospheric samples has been developed. This method, based on full scan gas chromatography–mass spectrometry (GC–MS), allowed the proper determination of sixteen relevant pesticides, in a wide range of concentrations and without the influence of interferences. The pesticides were benfluralin, bitertanol, buprofezin, chlorfenvinphos, chlorpyrifos, chlorpyrifos-methyl, ethalfluralin, fenthion, lindane, malathion, methidathion, propachlor, propanil, pyriproxifen, tebuconazol and trifluralin. Comparisons of two types of sampling filters (quartz and glass fibre) and four types of solid-phase cartridges (XAD-2, XAD-4, Florisil and Orbo-49P) showed that the most suitable supports were glass fibre filter for particulate pesticides and XAD-2 and XAD-4 cartridges for gaseous pesticides (>95% recovery). Evaluations of elution solvents for ultrasonic-assisted extraction demonstrated that isooctane is better than ethylacetate, dichloromethane, methanol or a mixture of acetone:hexane (1:1).Recovery assays and the standard addition method were performed to validate the proposed methodology. Moreover, large simulator chamber experiments allowed the best study of the gas-particle partitioning of pesticides for testing the sampling efficiency for the validation of an analytical multiresidue method for pesticides in air. Satisfactory analytical parameters were obtained, with a repeatability of 5±1%, a reproducibility of 13±3% and detection limits of 0.05–0.18pgm⁻³ for the particulate phase and 26–88pgm⁻³ for the gaseous phase. Finally, the methodology was successfully applied to rural and agricultural samples in the Mediterranean area.

Keywords: Pesticides; Atmospheric samples; Gas chromatography–mass spectrometry

Comparison of silica gel modified with three different functional groups with C-18 and styrene–divinylbenzene adsorbents for the analysis of selected volatile flavor compounds by Mariusz Dziadas; Magdalena Nowacka; Teofil Jesionowski; Henryk H. Jeleń (pp. 66-72).

Display Omitted► C-18 and SDVB phases are usually used for the SPE extraction of volatile flavor compounds. ► A simple and low cost method for obtaining silica phases functionalized with alcoxysilanes with three different functional groups is proposed. ► Obtained phases was evaluated for selected volatile flavor compounds. ► The performance of obtained phases was comparable to commercially available C-18 and SDVB phases.A comparison of SPE cartridges produced in authors laboratory containing silica modified by addition of three functional moieties with standard C-18 and SDVB cartridges was made in terms of their applicability for the isolation of flavor compounds. Compounds found in wine and grapes were used for model mixture, which was spiked into a grape juice. Functionalized phases for SPE were prepared modifying silica gel with alkoxysilanes with different functional groups: (3-(phenylamino)-propyltrimethoxysilane, octyltriethoxysilane and octadecyl-silane. The functionalization was carried out by the dry method, which resulted 5, 10 and 20 weight parts of initial support. Functionalized phases were characterized using FT-IR, elemental analysis and NMR.Performance for new phases compared to “standard” ones (C-18 and SDVB (styrene–divinylbenzene) varied, depending on the group or type of analyzed compound. They were more efficient in extraction of methyl anthranilate and vanilins. For extraction of terpenes, C-6 alcohols, isoprenoids, benzene derivatives and phenols their efficiency was comparable to that of C-18.Functionalized laboratory-made mixed phases are suitable for extraction of flavor compounds from grape juice. They are suitable for extraction of compounds belonging to different chemical classes with the efficiency comparable to C-18 and SDVB phases. The production of such functionalized phases can be easily performed in the laboratory, at a very low cost, comparing to C-18 or SDVB cartridges. This makes the proposed functionalized phases an interesting alternative, in sample preparation for analysis and particularly in preparative/flash chromatography.

Keywords: Solid phase extraction; Grape; Wine; Flavor compounds; Silica

Matrix effect in the analysis of drugs of abuse from urine with desorption atmospheric pressure photoionization-mass spectrometry (DAPPI-MS) and desorption electrospray ionization-mass spectrometry (DESI-MS) by Niina M. Suni; Pia Lindfors; Olli Laine; Pekka Östman; Ilkka Ojanperä; Tapio Kotiaho; Tiina J. Kauppila; Risto Kostiainen (pp. 73-80).

Display Omitted► DAPPI-MS and DESI-MSI in the analysis of drugs of abuse from urine. ► DAPPI-MS has better urine matrix tolerance over DESI-MS. ► Urine matrix can affect the ionization mechanism in DAPPI. ► DAPPI-MS/MS can be used for screening of drugs from urine after sample pretreatment.We have studied the matrix effect within direct analysis of benzodiazepines and opioids from urine with desorption electrospray ionization-mass spectrometry (DESI-MS) and desorption atmospheric pressure photoionization-mass spectrometry (DAPPI-MS). The urine matrix was found to affect the ionization mechanism of the opioids in DAPPI-MS favoring proton transfer over charge exchange reaction. The sensitivity for the drugs in solvent matrix was at the same level with DESI-MS and DAPPI-MS (LODs 0.05–6μgmL⁻¹) but the decrease in sensitivity due to the urine matrix was higher with DESI (typically 20–160-fold) than with DAPPI (typically 2–15-fold) indicating better matrix tolerance of DAPPI over DESI. Also in MS/MS mode, DAPPI provided better sensitivity than DESI for the drugs in urine. The feasibility of DAPPI-MS/MS was then studied in screening the same drugs from five authentic, forensic post mortem urine samples. A reference measurement with gas chromatography-mass spectrometry (GC–MS) (including pretreatment) revealed 16 findings from the samples, whereas with DAPPI-MS/MS after sample pretreatment, 15 findings were made. Sample pretreatment was found necessary, since only eight findings were made from the same samples untreated.

Keywords: Ambient mass spectrometry; Desorption electrospray ionization; Desorption atmospheric pressure photoionization; Matrix effect; Drug analysis

Quantitative analysis of multiple urinary biomarkers of carcinoid tumors through gold-nanoparticle-assisted laser desorption/ionization time-of-flight mass spectrometry by Tsung-Rong Kuo; Jinn-Shiun Chen; Yu-Chen Chiu; Chia-Yi Tsai; Cho-Chun Hu; Chia-Chun Chen (pp. 81-86).

Display Omitted► We quantified four urinary biomarkers of carcinoid tumors by SALDI-TOF MS. ► Intensities of biomarkers were enhanced with gold-nanoparticles-assisted in MS. ► Internal standard of NAD was selected to improve the reproducibility in MS. ► Simultaneous quantification of urinary biomarkers in urine samples is demonstrated.A simple technique for quantitative analysis of four urinary biomarkers, tryptophan (TRP), 5-hydroxytryptophan (5-HTP), 5-hydroxytryptamine (5-HT) and 5-hydroxyindole acetic acid (5-HIAA) of carcinoid tumors is developed using gold nanoparticles as the assisted matrix in surface-assisted laser desorption/ionization time-of-flight mass spectrometry (SALDI–TOF MS). The optimal SALDI conditions for the efficient ionization of those biomarkers are systematically explored by the adjustments of the concentrations of gold nanoparticles and internal standards. The mass spectra with strong signals and minimal background noise are obtained using 1-naphthaleneacetamide (NAD) as the internal standard. The calibration curves of the biomarker concentrations are determined using SALDI–TOF MS and the high linearity is obtained in all samples. For future clinical testing, multiplexed detection of those biomarkers in the urine samples of healthy males is performed. The successful quantitative detections of TRP, 5-HTP, 5-HT and 5-HIAA indicate that our technique provided great potentials to be developed a simple and rapid platform for the tumor biomarker detections.

Keywords: Multiplexed assay; Gold nanoparticles; Surface-assisted laser desorption/ionization; Urinary biomarkers; 5-Hydroxyindole acetic acid

Interaction of soil humic acids with herbicide paraquat analyzed by surface-enhanced Raman scattering and fluorescence spectroscopy on silver plasmonic nanoparticles by M.L. Roldán; G. Corrado; O. Francioso; S. Sanchez-Cortes (pp. 87-95).

Display Omitted► The interaction between paraquat and soil humic acids amended over 30 years with different substrates is studied. ► SERS and SEF provide significant selective information from the pesticide and the organic matter. ► The aggregation, coiling/uncoiling and the adsorption of humic acids in the presence of paraquat on metallic surfaces can be investigated. ► The presence of carboxylate, aliphatic chains and aromatic moieties determines the interaction mechanism with the pesticide.A study of the interaction between paraquat (methyl viologen) and humic acids, extracted from a soil amended over 30 years with crop residues, cow slurries and cattle manure, was carried out by two emission spectroscopies based on plasmonic effects: surface-enhanced Raman scattering (SERS) and surface-enhanced fluorescence (SEF). To carry out this study Ag nanoparticles were used. The complex formation was tested by analyzing the effect of the herbicide on humic acids, and by varying experimental parameters such as the pH and the laser excitation wavelength. The study of the vibrational bands led to infer information about the interaction mechanism of paraquat with humic acids and to find a correlation between this interaction and the humic acids structural modification induced by the different amendments added to soil.

Keywords: Humic acids; Surface-enhanced Raman scattering (SERS); Surface-enhanced fluorescence (SEF); Paraquat

Near infrared and Raman spectroscopy as Process Analytical Technology tools for the manufacturing of silicone-based drug reservoirs by J. Mantanus; E. Rozet; K. Van Butsele; C. De Bleye; A. Ceccato; B. Evrard; Ph. Hubert; E. Ziémons (pp. 96-106).

Display Omitted► In this study, NIR and Raman spectroscopy were successfully used as PAT tools to assess 3 silicone-based drug reservoirs quality attributes. ► API homogeneity (Raman). ► Crosslinking status (NIR). ► API content (NIR).Using near infrared (NIR) and Raman spectroscopy as PAT tools, 3 critical quality attributes of a silicone-based drug reservoir were studied. First, the Active Pharmaceutical Ingredient (API) homogeneity in the reservoir was evaluated using Raman spectroscopy (mapping): the API distribution within the industrial drug reservoirs was found to be homogeneous while API aggregates were detected in laboratory scale samples manufactured with a non optimal mixing process. Second, the crosslinking process of the reservoirs was monitored at different temperatures with NIR spectroscopy. Conformity tests and Principal Component Analysis (PCA) were performed on the collected data to find out the relation between the temperature and the time necessary to reach the crosslinking endpoints. An agreement was found between the conformity test results and the PCA results. Compared to the conformity test method, PCA had the advantage to discriminate the heating effect from the crosslinking effect occurring together during the monitored process. Therefore the 2 approaches were found to be complementary. Third, based on the HPLC reference method, a NIR model able to quantify the API in the drug reservoir was developed and thoroughly validated. Partial Least Squares (PLS) regression on the calibration set was performed to build prediction models of which the ability to quantify accurately was tested with the external validation set. The 1.2% Root Mean Squared Error of Prediction (RMSEP) of the NIR model indicated the global accuracy of the model. The accuracy profile based on tolerance intervals was used to generate a complete validation report. The 95% tolerance interval calculated on the validation results indicated that each future result will have a relative error below ±5% with a probability of at least 95%. In conclusion, 3 critical quality attributes of silicone-based drug reservoirs were quickly and efficiently evaluated by NIR and Raman spectroscopy.

Keywords: Vibrational spectroscopy; Silicone-based drug reservoirs; Quality by Design; Process Analytical Technology; Chemometrics; Validation

Spectrophotometric determination of various polyanions with polymeric film optodes using microtiter plate reader by Nedime Dürüst; Mark E. Meyerhoff; Nazangül Ünal; Sibel Naç (pp. 107-112).

Display Omitted► A new titrimetric analysis method to detect polyanions in food products. ► Application of polycation sensitive optical sensing films for detection of several polyanions like DNA, pentosanpolysulfate(PPS), xanthan, alginate and carrageenan. ► A microtiter plate-based titrimetric assay to detect thickening agents in foods.Polycation-sensitive membrane optodes based on the chromoionophore 2′,7′-dichlorofluorescein octadecylester (DCFOE) have previously been developed and used for determination of heparin via a titrimetric method. In this study, it is shown that some other important polyanions such as PPS (pentosan polysulfate), DNA, xanthan, Na-alginate, and carrageenan (food additive) can also be readily determined by using DCFOE-based microtiter plate-format optodes (MPOs) and polycationic titrants that bind these polyanionic species. The optical sensors are prepared with poly(vinyl chloride) (PVC), polyurethane (PU), bis(2-ethylhexyl)sebacate (DOS), and 2′,7′-dichlorofluorescein octadecylester (DCFOE) and exhibit reproducible and sensitive absorbance changes in response to the varying polycationic titrant concentrations. Three different polycations; protamine, poly-l-lysine and poly-l-arginine, are employed as titrants. The method has a detection limit of 1μgmL⁻¹, and a dynamic range of 1–40μgmL⁻¹. After the quantitative determinations are successfully demonstrated in buffered solutions, similar titrations are also performed in real samples. The method is validated by recovery studies in these samples. The average polyanion recoveries were quantitative [99.7(±1.3) % for pastry cream with vanillin (protamine titrant); 100.4 (±3.3) % for pastry gel with strawberry(PLA titrant), and 102.9(±2.0) % for pastry gel with strawberry (PLL titrant)].

Keywords: Polyanion; Thickening agent; Polymeric film sensor; Chromoionophore; Microtiter plate-format optode

Determination of N-methylcarbamate insecticides in water samples using dispersive liquid–liquid microextraction and HPLC with the aid of experimental design and desirability function by Saeid Khodadoust; Mohammadreza Hadjmohammadi (pp. 113-119).

Display Omitted► A simple method for the extraction of NMCs by using chemometrics was developed. ► The significant variables were optimized by using a CCD combined with DF. ► This procedure of optimization can be used as a new approach for obtained the optimized condition of variables in experimental design. ► This technique provides good repeatability and high extraction recovery.A rapid and simple method for the extraction and preconcentration of N-methylcarbamates (NMCs) (carbofuran, carbaryl and promecarb) in water samples using dispersive liquid–liquid microextraction (DLLME) using chemometrics was developed. Influence variables such as volume of extracting (CHCl₃) and dispersing solvents (ACN), pH and ionic strength, extraction time and centrifugation time and speed were screened in a 2^7–4 Plackett–Burman design was investigated. The significant variables were optimized by using a central composite design (CCD) combined with desirability function (DF). At optimum conditions values of variables set as 126μL chloroform, 1.5mL acetonitrile, 1min extraction time, 10min centrifugation at 4000rpmmin⁻¹, natural pH, 4.7% (w/v) NaCl, the separation was reached in less than 14min using a C₁₈ column and an isocratic binary mobile phase (acetonitrile: water (50:50, v/v)) with flow rate of 1.0mLmin⁻¹. At optimum conditions method has linear response over 0.001–10μgmL⁻¹ with detection limit between 0.0001 and 0.0005μgmL⁻¹ with relative standard deviations (RSDs) in the range 2.18–5.06% ( n=6).

Keywords: Abbreviations; LLE; liquid–liquid extraction; SDME; single-drop microextraction; MSPD; matrix solid-phase dispersion; μ; -; SPE; micro-solid phase extraction; CPE; cloud-point extraction; SPME; solid-phase microextraction; LPME; liquid-phase microextraction; DLLME; dispersive liquid–liquid microextraction; P; –; B; Plackett–Burman; CCD; central composite design; DF; desirability function; EF; enrichment factor; ER; extraction recovery; ANOVA; analysis of varianceCentral composite design; Dispersive liquid–liquid microextraction; HPLC; Plackett–Burman design; N-methylcarbamates

Quantitative analysis of essential oils in perfume using multivariate curve resolution combined with comprehensive two-dimensional gas chromatography by Luiz Antonio Fonseca de Godoy; Leandro Wang Hantao; Marcio Pozzobon Pedroso; Ronei Jesus Poppi; Fabio Augusto (pp. 120-125).

Display Omitted► Multivariate curve resolution (MCR) was assessed as a quantitative tool for GC×GC. ► Quantitation of essential oils on perfume was made using GC×GC-FID chromatograms. ► The combination GC×GC+MCR resulted on excellent accuracy and precision. ► It can be an alternative to quantify ingredients on complex mixtures.The use of multivariate curve resolution (MCR) to build multivariate quantitative models using data obtained from comprehensive two-dimensional gas chromatography with flame ionization detection (GC×GC-FID) is presented and evaluated. The MCR algorithm presents some important features, such as second order advantage and the recovery of the instrumental response for each pure component after optimization by an alternating least squares (ALS) procedure. A model to quantify the essential oil of rosemary was built using a calibration set containing only known concentrations of the essential oil and cereal alcohol as solvent. A calibration curve correlating the concentration of the essential oil of rosemary and the instrumental response obtained from the MCR-ALS algorithm was obtained, and this calibration model was applied to predict the concentration of the oil in complex samples (mixtures of the essential oil, pineapple essence and commercial perfume). The values of the root mean square error of prediction (RMSEP) and of the root mean square error of the percentage deviation (RMSPD) obtained were 0.4% (v/v) and 7.2%, respectively. Additionally, a second model was built and used to evaluate the accuracy of the method. A model to quantify the essential oil of lemon grass was built and its concentration was predicted in the validation set and real perfume samples. The RMSEP and RMSPD obtained were 0.5% (v/v) and 6.9%, respectively, and the concentration of the essential oil of lemon grass in perfume agreed to the value informed by the manufacturer. The result indicates that the MCR algorithm is adequate to resolve the target chromatogram from the complex sample and to build multivariate models of GC×GC-FID data.

Keywords: Multivariate curve resolution; Comprehensive two-dimensional gas chromatography; Multivariate analysis; Rosemary essential oil; Lemon grass essential oil; Perfume

Erratum to “A modular microfluidic system for deoxyribonucleic acid identification by short tandem repeat analysis” [Analytica Chimica Acta 687 (2011) 150–158] by Carmen R. Reedy; Kristin A. Hagan; Daniel J. Marchiarullo; Alison H. Dewald; Annalise Barron; Joan M. Bienvenue; James P. Landers (pp. 126-126).

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Analytica Chimica Acta (v.699, #1)