Analytica Chimica Acta (v.552, #1-2)
Calendar of forthcoming meetings (N1-N2).
Chemometrical exploration of an isotopic ratio data set of acetylsalicylic acid by I. Stanimirova; M. Daszykowski; E. Van Gyseghem; F.F. Bensaid; M. Lees; J. Smeyers-Verbeke; D.L. Massart; Y. Vander Heyden (1-12).
A data set consisting of fourteen isotopic ratios or quantities derived from such ratios for samples of acetylsalicylic acid (aspirin), commercialized by various pharmaceutical companies from different countries, was analyzed. The goal of the data analysis was to explore whether results can be linked to geographical origin or other features such as different manufacturing processes, of the samples. The methods of data analysis used were principal component analysis (PCA), robust principal component analysis (RPCA), projection pursuit (PP) and multiple factor analysis (MFA). The results do not seem to depend on geographic origin, except for some samples from India. They do depend on the pharmaceutical companies. Moreover, it seems that the samples from certain pharmaceutical companies form clusters of similar samples, suggesting that there is some common feature between those pharmaceutical companies. Variable selection performed by means of MFA showed that the number of variables can be reduced to five without loss of information.
Keywords: Chemometrics; Principal component analysis; Projection pursuit; Multiple factor analysis; Acetylsalicylic acid; Isotopic ratios;
Classification of olive oils using high throughput flow 1H NMR fingerprinting with principal component analysis, linear discriminant analysis and probabilistic neural networks by Serge Rezzi; David E. Axelson; Károly Héberger; Fabiano Reniero; Carlo Mariani; Claude Guillou (13-24).
The combination of 1H NMR fingerprinting with multivariate analysis provides an original approach to study the profile of olive oil in relation to its geographical origin and processing. The present work aims at illustrating the relevance of 1H NMR fingerprints for assessing the geographical origin and the year of production for olive oils from various Mediterranean areas. Multivariate (chemometric) techniques are able to filter out the most relevant information from a spectrum, e.g. for a classification. Principal component analysis (PCA) was carried out on the ∼12,000 variables (chemical shifts) and four data sets were defined prior to PCA. Linear discriminant analysis (LDA) of the first 50 PC's was applied for classification of olive oil samples (97 or 91) according to the geographic origin and year of production. The data analysis has been carried out with and without outliers, as well. Variable selection for LDA was achieved using: (i) the best five variables and (ii) an interactive forward stepwise manner. Using LDA on the external validation sets the correct classification varied between 47 and 75% (random selection), and between 35 and 92% (Kennard–Stone selection (KS)) depending on geographic origin (country) and production years. A similar success rate could be achieved using partial least squares discriminant analysis (PLS DA). The success rate can be considerably improved by using probabilistic neural networks (PNN). Correct classification by PNN varied between 58 and 100% on the external validation sets. Other chemometric techniques, such as multiple linear regression, or generalized pair-wise correlation, did not give better results.
Keywords: NMR; Authenticity; Multivariate methods; Linear discriminant analysis; Principal component analysis; Chemometrics; Artificial neural networks;
A procedure to assess linearity by ordinary least squares method by Scheilla V.C. de Souza; Roberto G. Junqueira (25-35).
A detailed procedure for testing linearity of calibration curves in method validation by the ordinary least squares method (OLSM), including experimental design, estimation of the parameters, outlier treatment and evaluation of the assumptions, was proposed. The theoretical background was discussed and the assumptions considered were: (i) normality, homoscedasticity and independency of residuals and (ii) adjustment to the correct model. The procedure involved precise statistical techniques that were easily carried out by any commercial spreadsheet software. The suitability of the procedure for assessing linearity was demonstrated by the application in food analysis.
Keywords: Linearity; Ordinary least squares method; Chemometry; Method validation;
Modifications to the standard additions method for components at very high concentrations by Kevin G. Boto; Lawrence J. Murphy (36-41).
Limitations to the classical methods of standard additions (MSA) are discussed and overcome by the proposed modifications to the method. The modifications permit accurate linear regression determination of analytes at very high concentrations (>5%) in complex materials where matrix matching is difficult or where appropriate standard reference materials (SRM) are not available. The modifications are demonstrated with X-ray diffraction (XRD) determination of θ (56.5%) and amorphous (23.9%) phase concentrations in fumed alumina, which contains a variety of crystalline phases. The modified method may be especially suited to analysis of solids and powders with techniques such as XRD, X-ray fluorescence (XRF), and Raman spectroscopy where similar very high-analyte concentration and sample matrix complexity are commonly encountered, provided that the assumptions of the method can be met.
Keywords: X-ray diffraction; Standard additions; High-analyte concentrations; Fumed alumina crystal phases;
QSAR analysis of a series of 2-aryl(heteroaryl)-2,5-dihydropyrazolo[4,3-c]quinolin-3-(3H)-ones using piecewise hyper-sphere modeling by particle swarm optimization by Li Lin; Wei-Qi Lin; Jian-Hui Jiang; Yan-Ping Zhou; Guo-Li Shen; Ru-Qin Yu (42-49).
In the present work, we employed piecewise hyper-sphere modeling by particle swarm optimization (PHMPSO) which splits the dataset into subsets with desired linearity in each model for QSAR studies of a series of 2-aryl(heteroaryl)-2,5-dihydropyrazolo[4,3-c]quinolin-3-(3H)-ones (PQs) for their affinity to benzodiazepine receptor (BzR). The results were compared to those obtained by MLR modeling in a single model with the whole data set as well as in submodels based on K-means clustering analysis. It has been clearly shown that electronic descriptors and spatial descriptors play the important roles in the compounds’ affinity to BzR. In addition, the molecular density, the Y component of the principal moment of inertia, the magnitude and the Y component of the dipole moment of the molecules can detrimentally affect PQ analogue BzR affinity, while the X component of the dipole moment of the molecules can favorably affect compounds’ affinity.
Keywords: Quantitative structure–activity relationship; Piecewise hyper-sphere modeling; Particle swarm optimization; 2-Aryl(heteroaryl)-2,5-dihydropyrazolo[4,3-c]quinolin-3-(3H)-ones;
Sequential superheated liquid extraction of pesticides, pharmaceutical and personal care products with different polarity from marine sediments followed by gas chromatography mass spectrometry detection by S. Morales-Muñoz; J.L. Luque-García; M.J. Ramos; A. Fernández-Alba; M.D. Luque de Castro (50-59).
A method for the extraction of compounds with different polarity (namely, triclosan, estrone, 17β-estradiol, diethylstilbestrol, 4-octylphenol, procymidone, permethrin, oxyfluorfen, bisphenol A and 2,8-dibenzodichloro-p-dioxin) from marine sediments has been proposed. The proposed method consists of a sequential superheated fluid extraction with dichloromethane in a dynamic manner and with water in a static–dynamic manner for 50 min. The organic and aqueous extracts are independently collected and treated by evaporation and liquid–liquid extraction, respectively. The working conditions were optimized using multivariate approaches. Triclosan, bisphenol A, oxyfluorfen and permethrin were quantitatively extracted with repeatability and reproducibility in the range 2.9–9.1 and 5.5–9.1% R.S.D., respectively. The analytes were identified and quantified by gas chromatography–tandem mass spectrometry. The method was compared with conventional Soxhlet for the extraction of the analytes from spiked (at low ppb levels) sediments collected at the outflow of an urban wastewater treatment plant and non-spiked sediment collected from a sporting harbour. Statistical differences between the results of both methods were not found from the t-test for 95% of confidence level (p-value = 0.131).
Keywords: Sequential superheated liquid extraction; Marine sediments; Gas chromatography;
Determination of halogenated solvents content in olive oil by two completely automated headspace techniques coupled to gas chromatography–mass spectrometry by F.J. Arrebola; M.J. González-Rodríguez; A. Garrido Frenich; A. Marín-Juan; J.L. Martínez Vidal (60-66).
Two different methods have been developed and compared for determining the halogenated solvents content of olive oils. The optimal parameters for isolation and preconcentration of relevant halogenated solvents (bromodichloromethane, dibromochloromethane, chloroform, bromoform, tetrachloroethene, trichloroethene, ethylenedichloride, and vinyl chloride) were established. These proposed procedures are completely automated and do not require reagents because both methods are based on headspace techniques, conventional headspace (HS) and headspace solid-phase microextraction (HS-SPME), both techniques on-line coupled to a gas chromatograph–mass spectrometer (GC–MS) operated in selected ion monitoring (SIM) mode. The methods were validated and compared their figures of merit. In general, both extraction techniques presented similar extraction efficiency at the studied concentrations. However, average relative standard deviation (R.S.D.) obtained at low concentration levels was slightly better for HS (8.6%) than for HS-SPME (11.8%) technique. It was due to the lower limits of detection (LOD) and quantification (LOQ) values obtained for HS, especially for the less volatile vinyl chloride, chloroform and ethylene dichloride compounds. Finally, the HS-GC–MS method was applied to the analysis of real olive oil and olive-pomace oil samples. None content of halogenated solvents was found above the LOD in the studied samples. The proposed methods are faster, simpler and easier than the official methods proposed by the European Union and the International Olive Oil Council.
Keywords: Halogenated solvents; Olive oil; Headspace; Solid-phase microextraction; Gas chromatography–mass spectrometry;
Determination of clenbuterol in urine using headspace solid phase microextraction or liquid–liquid–liquid microextraction by Mahaveer B. Melwanki; Wei-Hsun Hsu; Shang-Da Huang (67-75).
Headspace solid phase microextraction (HS-SPME) and liquid–liquid–liquid microextraction with automated movement of the acceptor phase (LLLME/AMAP) techniques are described for the extraction of clenbuterol (CB) in urine. HS-SPME technique involves the extraction of the drug by SPME fibre in a headspace mode with a cooling device at the upper part of the vial to cool the headspace of the vial where the fiber is suspended. This cooling effect will enhance the absorption of analytes by the fiber. As the cooling system is surrounding the vial, the headspace will also be cooled in addition to the cooling of the fiber. After extraction the derivatization of the extracted drug with hexamethyldisilazane (HMDS) was performed by suspending the fiber in the headspace of another vial saturated with the vapor of HMDS. This derivatized compound was analyzed by gas chromatography with mass spectrometric detection (GC/MS). LLLME/AMAP technique involves the extraction of CB, a basic drug, from an alkaline solution into the organic solvent residing in the pores of the hollow fiber and then back extracted into the acidic acceptor solution inside the lumen of the hollow fiber. The acceptor solution was repeatedly moved in and out of the hollow fibre assisted by a syringe pump. This repeated movement provides fresh acceptor phase to come in-contact with the organic phase and thus improving the efficiency of extraction. Quantification was performed using high performance liquid chromatography with ultraviolet (HPLC/UV) detection. In both the techniques, experimental parameters have been studied to achieve greater sensitivity. Linearity was observed over the range of 1–1000 ng ml−1 (R 2 = 0.9990) and 50–3000 ng ml−1 (R 2 = 0.9956) with detection limits of 0.23 ng ml−1 and 3.9 ng ml−1, respectively, for HS-SPME-GC/MS and LLLME/AMAP-HPLC/UV method. R.S.D. values of 3.9% (HS-SPME-GC/MS) and 5.8% (LLLME/AMAP-HPLC/UV) indicated good precision of the techniques. Absolute recovery was found to be 0.007% and 18%, respectively, for HS-SPME-GC/MS and LLLME-HPLC/UV methods. Finally, the techniques have been applied for the analysis of CB in urine samples. No effort has been made to compare the method with official method.
Keywords: Clenbuterol; Headspace solid phase microextraction; GC-MS; Liquid–liquid–liquid microextraction; HPLC-UV; Urine analysis;
Application of standard addition methodology for the determination of banned azo dyes in different leather types by Lars-Henric Ahlström; Johan Raab; Lennart Mathiasson (76-80).
An analytical procedure based on microwave-assisted extraction (MAE) and standard addition was applied for the determination of banned azo dyes in bovine, sheep, and goat leather. Standard addition at four different concentration levels was performed using azo dyes, dissolved either in methanol or water. All dyes were determined indirectly by measuring their corresponding harmful aromatic amines, formed after reduction by use of sodium dithionite. Comparing found amounts of amines with theoretical target values allowed an assessment of accuracy. The recoveries were also compared with those obtained for non-spiked samples using external standard calibration. The standard addition approaches provided much better accuracy than external standard calibration, with recoveries close to 100% for most amines. Since there was no great difference in recoveries when using methanol or water as solvent, preparation of the dyes in methanol might be preferred because of the faster evaporation of the solvent after spiking.
Keywords: Azo dyes; Aromatic amines; Leather; MAE; Standard addition;
Synthesis and application of an oxytetracycline imprinted polymer for the solid-phase extraction of tetracycline antibiotics by E. Caro; R.M. Marcé; P.A.G. Cormack; D.C. Sherrington; F. Borrull (81-86).
Two molecularly imprinted polymers (MIPs) were synthesised using tetracycline and oxytetracycline antibiotics as template molecules in non-covalent molecular imprinting procedures. After a chromatographic evaluation, the performance of the MIPs as selective SPE sorbents was evaluated. In this study, it was demonstrated that after a clean-up step to disrupt the non-specific interactions between the MIPs and the compounds retained on them, the polymers showed cross-reactivity for certain other tetracycline analytes. The feasibility of the MIP to selectively extract tetracycline antibiotics in pig kidney tissue extract was demonstrated with the oxytetracycline MIP which gave rise to the best MISPE results when it was applied. Good recoveries were obtained when oxytetracycline and tetracycline were selectively extracted from 25 ml of pig kidney tissue extract.
Keywords: Column liquid chromatography; Solid-phase extraction; Molecularly imprinted polymer; Tetracycline antibiotics; Tissue samples;
Application of a multi-sulfonamide biosensor immunoassay for the detection of sulfadiazine and sulfamethoxazole residues in broiler serum and its use as a predictor of the levels in edible tissue by Willem Haasnoot; Monique Bienenmann-Ploum; Urpo Lamminmäki; Manon Swanenburg; Hans van Rhijn (87-95).
A multi-sulfonamide biosensor immunoassay (BIA), based on a previously developed mutant antibody (A.3.5) in an optical biosensor (Biacore 3000), was applied to analyse the serum and plasma samples obtained from the broilers treated with sulfamethoxazole and sulfadiazine. The assay was fast (5 min per sample), the sample preparation easy (dilution in antibody containing buffer only) and an equal sensitivity for the two sulfonamides was obtained with limits of detection (LOD) in serum and plasma below 10 ng ml−1. The concentrations found with the BIA in serum and plasma of the treated broilers were comparable and higher than the concentrations found in the tissue by LC–MS/MS. The average serum/tissue ratios for sulfamethoxazole were 6.2 (leg meat), 2.5 (liver) and 1.3 (skin + fat) and for sulfadiazine 8.7 (leg meat), 3.1 (liver) and 2.2 (skin + fat). To predict the concentrations of the two sulfonamides below the maximum residue limit (MRL) of 100 ng g−1 in the tissue with the highest level (skin + fat), the proposed action level of the multi-sulfonamide BIA in serum is 130 ng ml−1. A later developed mutant antibody (M.3.4), with a better sensitivity towards more sulfonamides, was applied during a survey. Serum samples (n = 300) of broilers from 30 different flocks were found negative. Concentrations between <5 and 152 ng ml−1 (sulfamethoxazole equivalents) were found in the serum samples of one flock (n = 160) with an average of 25 ± 21 ng ml−1. The sulfonamide identified by LC–MS/MS in these samples was sulfamethoxazole.
Keywords: Biosensor immunoassay; Biacore 3000; Recombinant antibodies; Sulfonamides; Chicken; Serum; Plasma; Tissue;
Screening and confirmation of recombinant human erythropoietin and darbepoietin-α in spiked plasma samples from drug-free horses by Shveta Gupta; Abby Sage; Ashok K. Singh (96-109).
Methods for screening and confirmation of erythropoiesis stimulating glycopeptides (ESGs) such as endogenous equine erythropoietin (eEPO), recombinant human erythropoietin (rhEPO) and darbepoietin-α (DAR) have been described. Four rhEPO immunoassay kits (R&D ELISA, Diagnostic Systems Limited (DSL) ELISA, chemiluminescent IMMULITE (CHEM), and DiaSorin RIA kits) were evaluated for eEPO, rhEPO and DAR screening in basal and spiked horse samples. The R&D-ELISA detected rhEPO and DAR, but did not detect eEPO. DSL-ELISA, CHEM and DS-RIA kits detected all three ESGs. The immunoassay kits did not differentiate rhEPO and DAR. Deglycosylation of the ESGs increased the detection limits of the immunoassays. DAR, rhEPO and eEPO were extracted from positive or spiked samples by using the Affi-gel and/or immunoaffinity columns. The R&D antibodies did not retain eEPO but retained rhEPO and DAR. The antibodies from DS and DSL effectively retained all three ESGs. The isolated ESGs were confirmed by using either gel electrophoresis or MALDI-TOF-MS methods. DAR and rhEPO extracted from horse plasma were hydrolyzed using trypsin and the fragments were analyzed by the MALDI-TOF-MS for their amino acid sequence. DAR and rhEPO could be differentiated according to their intact mass-ions (m/z 29,000 for rhEPO and m/z 36,000 for DAR) or trypsin-hydrolysis products (m/z 2689 and 2359 for rhEPO and m/z 2696 and 2293 for DAR).
Keywords: Erythropoietin; Darbepoietin; MALDI-TOF;
Rapid determination of sulfonamides in milk using micellar electrokinetic chromatography with fluorescence detection by Sushma Lamba; Sunil Kumar Sanghi; Amit Asthana; Manjusha Shelke (110-115).
A new method was developed for the determination of sulfonamides in milk by using micellar electrokinetic chromatography coupled with fluorescence detection. Separation of fluorescamine-derivatized sulfonamides was accomplished by using a buffer 13.32 mM disodium hydrogen phosphate, 6.67 mM potassium dihydrogen phosphate and 40 mM sodium dodecyl sulphate at pH 7.5 in addition to positive power supply at 21 kV at 25 °C. Detection was performed using UG-11 excitation filter and 495 nm emission filters. The proposed capillary electrophoresis method allows the separation of five sulfonamides within 7 min with a limit of detection of 1.59–7.68 nmol/L for all the sulfonamides considered for present study. A simple sample preparation method with fairly good recoveries 85–114% is also presented in current paper. Inter-day and intra-day validation of the separation method shows fairly good results. Robustness of the method has also been studied.
Keywords: Sulfonamides; Fluorescamine; Micellar electrokinetic chromatography; Milk;
Detection of boldenone and its major metabolites by liquid chromatography—tandem mass spectrometry in urine samples by F. Buiarelli; G.P. Cartoni; F. Coccioli; L. Giannetti; M. Merolle; B. Neri; A. Terracciano (116-126).
Boldenone is an androgenic anabolic steroid (AAS) intensively used for growth promoting purposes in animals destined for meat production and as a performance enhancer in athletics. Therefore its use is officially banned either in animals intended for consumption or in humans. Because most anabolic steroids are completely metabolized and usually no parent steroid is excreted, metabolite identification is crucial to detect the illegal use of anabolic steroids either in humans or in livestock.The aim of this work is the investigation of 17β-boldenone and its main metabolites, 17β-sulphate, 17β-glucuronide, 5β-androst-1-en-17β-ol-3-one and 17α-boldenone, in human and bovine urine developing a multiresidue analysis.After solid phase extraction of urine samples, detection is carried out by high performance liquid chromatography–tandem mass spectrometry in multiple reaction monitoring. The average recovery for all the investigated compounds is above 70%. The developed method is very easy, quick and highly specific. Linearity, precision, decision limit and detection capability were also evaluated.
Keywords: Liquid chromatography–tandem mass spectrometry; Urine; Boldenone metabolites; Conjugated boldenone;
Electrochemical behavior of vardenafil on glassy carbon electrode: Determination in tablets and human serum by Bengi Uslu; Burcu Dogan; Sibel A. Özkan; Hassan Y. Aboul-Enein (127-134).
The voltammetric behavior of vardenafil was studied on glassy carbon electrode using cyclic, differential pulse (DPV) and Osteryoung square-wave (OSW) voltammetric techniques. Vardenafil exhibited irreversible anodic waves over the pH range 1.00–12.00 in different supporting electrolytes. The current–concentration plot was rectilinear over the range from 4 × 10−7 to 2 × 10−5 M with correlation coefficient of 0.999. The wave was characterized as being irreversible and diffusion-controlled. The developed procedure was successfully applied to the determination of vardenafil in tablets and in spiked human serum. Furthermore, results obtained by the proposed method have been compared with high-performance liquid chromatographic method.
Keywords: Vardenafil hydrochloride; Voltammetry; Drug analysis; Oxidation mechanism;
Measurement of ion speciation in animal slurries using the Donnan Membrane Technique by B. van der Stelt; E.J.M. Temminghoff; W.H. van Riemsdijk (135-140).
The availability of nutrients in animal slurry for plant uptake depends on the total content as well as on the forms in which these nutrients are present in slurry manure. A DMT-manure cell was developed which can help to determine the speciation of nutrients in animal slurries. The cell consists of an acceptor compartment, which is separated from the slurry by two negatively charged cation-exchange membranes. The membranes only allow exchange of ‘free’ cations between the slurry and the acceptor solution. After about 4 days, Donnan equilibrium will be reached between ‘free’ cation concentrations in the acceptor solution and the ‘free’ cation concentrations in the animal slurry.The DMT-manure cell has been used to study the effect of dilution of animal slurry (with distilled water) on ‘free’ ionic species (K+, Mg2+, Na+, Ca2+ and NH4 +). Total nutrient concentrations and the ‘free’ K+, Na+ and NH4 + concentrations decreased proportionately with increasing dilution. In contrast, the ‘free’ concentrations of Ca2+ and Mg2+ remained more or less constant upon dilution. The buffering of the ‘free’ Ca2+ and Mg2+ concentrations is most probably the result of Ca2+ and Mg2+ release from organic matter. Also, dissolution of phosphate minerals (struvite and whitlockite), which were likely present in the initial slurry, may have contributed to the buffering of the ‘free’ Ca2+ and Mg2+ concentrations.
Keywords: Chemical speciation; Donnan Membrane Technique; Animal slurry; Buffering of nutrients; N fractionation; Struvite;
Chemiluminescent determination of humic substances based on the oxidation by peroxymonosulfate by Giselle Baratti Magdaleno; Nina Coichev (141-146).
The intensity of emission radiation produced by humic (HA) and fulvic acids (FA) in the presence of SO5 2− in basic medium was used to determine HA and FA in the range of 0.5–20.0 mg l−1. The detection limit was 0.24 mg l−1. A comparative study was carried out using H2O2 in the presence of CH2O as oxidizing agent. Humic substances (HS) from several soil sources, different extraction and purifying procedures led to different calibration sensitivities and selectivity. Cations and anions such as Cu(II), Cr(III), Ca(II), Cl−, EDTA2−, NO3 −, PO4 3− and CO3 2−, did not interfere with the determination of HA. Although it was not possible to confirm the accuracy of the chemiluminescent method, low concentrations of HS in natural waters can be detected.
Keywords: Humic acid; Fulvic acid; Peroxymonosulfate; Chemiluminescence;
Chemiluminescent determination of oxalate based on its enhancing effect on the oxidation of methyl red by dichromate by Tomás Pérez-Ruiz; Carmen Martínez-Lozano; Virginia Tomás; José Fenoll (147-151).
A flow injection configuration for the chemiluminescence determination of oxalate is proposed. The procedure is based on the catalytic effect of oxalate on the oxidation of methyl red by dichromate. The chromium(III) formed catalyzes the luminescent reaction between luminol and hydrogen peroxide. The proposed method is simple, inexpensive, sensitive and suitable for concentrations of oxalate between 0.24 and 8.11 μg ml−1. The applicability of the method was demonstrated by determining oxalate in vegetables.
Keywords: Oxalate; Chemiluminescence; Flow-injection; Vegetables; Luminol;
A novel spectrofluorimetric method for determination of lomefloxacin based on supramolecular inclusion complex between it and p-sulfonated calyxarene by Yunyou Zhou; Qin Lu; Chun Liu; Shike She; Lun Wang (152-159).
The characteristics of host–guest complexation between p-sulfonated calixarene (SC4A) and lomefloxacin (LFLX) were investigated by fluorescence spectrometry. 1:1 stoichiometry for the complexation was established and their association constant at 25 °C was calculated by applying a deduced equation. The interaction mechanism of the inclusion complex was discussed. It was found that an appropriate amount of cationic surfactant cetyltrimethylammonium bromide (CTAB) could remarkably enhance the fluorescence intensity of the supramolecular complex system. Based on the obtained results, a novel sensitive spectrofluorimetric method for the determination of lomefloxacin was developed with a linear range of 0.01–3.0 μg ml−1 and a detection limit of 0.008 μg ml−1. The proposed method was applied satisfactorily to determine lomefloxacin in pharmaceutical preparations.
Keywords: Spectrofluorimetry; p-Sulfonated calyxarene; Host–guest complexation; Inclusion interaction; Lomefloxacin;
Quantification of aldehyde impurities in poloxamer by 1H NMR spectrometry by Jenny Forshed; Bengt Erlandsson; Sven P. Jacobsson (160-165).
This work presents a fast and simple quantitative method for impurity determination of acetaldehyde and propionaldehyde in poloxamer 188 by proton nuclear magnetic resonance spectroscopy (1H NMR). The sample is dissolved in D2O with DCl and analyzed with a 600 MHz NMR spectrometer. Data processing, including filtering by convolution of spectra with a triangular function and integration, is performed in MATLAB. The repeated studies of one sample, including automatic gradient shimming and data processing, revealed a relative standard deviation (R.S.D.) of 2.8%. For the reproducibility, also including sample preparation, the R.S.D. was less than 10%. The predictability of a linear calibration model was estimated by the root mean square error of prediction from leave-one-out cross-validation (RMSECV). Using 64 scans, RMSECV was found to be 7.2 and 5.5 μg g−1 for acetaldehyde and propionaldehyde respectively for a 4.3-min acquisition time. The limits of detection, defined as three times the noise, reached 19 and 15 μg g−1 respectively under the same experimental conditions. These limits are sufficient to quantify 80 and 100 μg g−1 of the impurities, which has been found to be the maximum allowed content in the poloxamer for some medical applications. Thus the method has the potential to replace the current liquid chromatography (LC) method for impurity determination of acetaldehyde and propionaldehyde in poloxamer, which is time-consuming and includes a work-up procedure involving many steps.
Keywords: Poloxamer; NMR; Quantitative analysis; Impurity determination;
Field-flow fractionation coupled to multi-angle laser light scattering detectors: Applicability and analytical benefits for the analysis of environmental colloids by F. v. d. Kammer; M. Baborowski; K. Friese (166-174).
Results from the analysis of natural colloid with a coupling of field-flow fractionation (FFF) with multi-angle laser light scattering photometers (MALLS) are presented. The results indicate that after FFF of natural colloids MALLS is applicable to retrieve independent and absolute particle sizes (RMS radius or radius of gyration) for the colloids fractionated. For the analysed samples of soil colloids the appropriate data processing in MALLS is the linear or second order ZIMM fitting method for particle sizes up to 500 nm in diameter. This is in contrast to the MALLS analysis of latex beads, where the ZIMM fitting method produces reliable results only below ∼100 nm in diameter. The reason for the good results for the soil colloids can be found in the behaviour of the particle form factor P(θ) which was found to be linear function when plotted as Kc/R(θ) over sin2(θ/2).
Keywords: Field-flow fractionation (FFF); Light scattering; Non-spherical particles; Natural colloids; Environmental particles; MALLS;
A wide dynamic range detection of biopolymer medicines with resonance light scattering and absorption ratiometry by Yi Juan Long; Yuan Fang Li; Cheng Zhi Huang (175-181).
Using the interaction of heparin with Janus Green Blue (JGB) as an example, herein a dual-wavelength resonance lighting scattering (RLS) ratiometric method and an absorbance ratiometric one are developed to detect biopolymer medicines based on their bindings with organic dyes. In aqueous solution, heparin could interact with JGB, displaying significantly enhanced RLS signals in UV–vis region. By measuring the RLS intensity ratio (R ratio) and absorbance ratio (A ratio) at the wavelengths of 285 nm over that at 345 nm, respectively, heparin over a wide dynamic range of content could be detected. Typically, when JGB concentration is kept at 1.00 × 10−5 mol l−1, using R ratio could detect heparin over a range of 0.30–2000 ng ml−1 with a limit of determination of 30 pg ml−1, while using A ratio could detect heparin over the range of 0.01–2000.0 ng ml−1 with a limit of determination of 1 pg ml−1. The wavelength-dependent RLS and absorption ratiometric methods were found to have much better flexibility for a series of common influences, such as pH, and dye concentration, than that of RLS method at a single wavelength. The interaction nature was investigated through size measurements and RLS imaging detections.
Keywords: Heparin; Janus Green Blue (JGB); Resonance light scattering (RLS) ratiometry; Absorbance ratiometry;
Capillary gas chromatography with atomic emission detection for determining chlorophenols in water and soil samples by Natalia Campillo; Nerea Aguinaga; Pilar Viñas; Ignacio López-García; Manuel Hernández-Córdoba (182-189).
A purge-and-trap preconcentration system coupled to a GC equipped with a microwave-induced atomic emission detector was used to determine 2-chlorophenol (2-CP), 2,4-dichlorophenol (2,4-DCP) and 2,4,6-trichlorophenol (2,4,6-TCP) in water and soil samples. The analytes were previously leached from the solid matrices into a 5% (w/v) sodium carbonate solution using an ultrasonic probe. It was necessary to acetylate the compounds before purging them from the aqueous medium, which, at the same time, improved their chromatographic separation. After selecting the optimal experimental conditions, the performance of the system was evaluated. Each chromatographic run took 26 min, including the purge time. Detection limits for 5 ml water samples ranged from 23 to 150 ng l−1, which is lower than the limits reached using the methods proposed by the US Environmental Pollution Agency (EPA) for chlorophenols in water. For soil samples, detection limits were calculated for 7 g samples, the resulting values ranging between 80 and 540 pg g−1 for 2,4,6-TCP and 2-CP, respectively. The accuracy of the method was checked by analysing a certified reference soil, as well as fortified water and soil samples.
Keywords: Chlorophenols; Soils; Waters; Ultrasounds probe; Purge-and-trap; Gas chromatography–atomic emission detection;
Development of a portable electroanalytical system for the stripping voltammetry of metals: Determination of copper in acetic acid soil extracts by Valerio Beni; Vladimir I. Ogurtsov; Nikolai V. Bakunin; Damien W.M. Arrigan; Martin Hill (190-200).
The development, characterisation and evaluation of a prototype portable electrochemical trace metal analyser are presented. The instrument is a battery-powered microcontroller-based potentiostat, which implements anodic stripping voltammetry (ASV) at suitable sensor electrodes. It is capable of operating away from the laboratory, in the absence of an external power source and is usable by low-skilled personnel. The distinguishing feature of the instrument is its custom software, which enables sample pre-screening, data processing and sample dilution and standard additions calculations to be carried out. The instrument has been evaluated by application of a methodology for the detection of copper in acetic acid soil extracts, both in the laboratory and in the field. Underpotential deposition staircase anodic stripping voltammetry (UPD-SCASV) of the copper at gold disk electrodes was used as a test method. There was good agreement between the instrument results and those from laboratory-based reference analytical methods for analyses carried out both in the laboratory and in the field.
Keywords: Determination of metals; In-the-field analysis; Stripping voltammetry; Portable instrumentation; BCR; Soil analysis;
Characterization of silica polymorphs in kaolins by X-ray diffraction before and after phosphoric acid digestion and thermal treatment by Sibel Kahraman; Müşerref Önal; Yüksel Sarıkaya; İhsan Bozdoğan (201-206).
To characterize silica polymorphs (silicas) in some kaolins, orthophosphoric acid digestion (240 °C, 15 min), and thermal treatment (1050 °C, 24 h) were applied to eight samples. The original, digested, and heated samples were examined by X-ray diffraction (XRD). Crystalline silica quartz (SiO2) was identified from the standard XRD patterns of the original kaolins; all contained quartz. On the other hand, hydrated partially crystalline silicas (SiO2·nH2O), such as well-ordered opal-C and opal-CT, were not readily distinguished from high-temperature crystalline silica, α-cristobalite, using standard XRD patterns of the original kaolins because, sharp and intense characteristic XRD peaks (h k l = 1 0 1) centered near 0.4 nm for opal-C, opal-CT, and α-cristobalite coincided. In order to distinguish these silicas the XRD patterns of the digested and heated samples were evaluated. It was observed that the 1 0 1 peaks disappear and sharpen in the course of digestion and heating, respectively. Because, the crystallinity of α-cristobalite does not change by these treatments, it was concluded that the kaolins contain opal-C and opal-CT or their mixtures in amorphous opal-A (SiO2·nH2O), but not α-cristobalite, which is probably human carcinogen. Because, the crystallinity increases in order opal-CT and opal-C, the narrowing in width at half-maximum peak height (FWHM) 1 0 1 must be more for opal-CT than opal-C by heating. Therefore, to distinguish opal-CT and opal-C from each other, the FWHM values before and after the heating process, were examined. Based on the results, it was estimated that six kaolins contain opal-CT in opal-A matrix, one kaolin contains only opal-A in a trace amount, and one kaolin contains non-opals.
Keywords: Cristobalite; Kaolin; Opal-C; Opal-CT; Phosphoric acid digestion; X-ray diffraction; Thermal treatment;
Determination of cell wall ferulic and p-coumaric acids in sugarcane bagasse by Feng Xu; Run-Cang Sun; Jin-Xia Sun; Chuan-Fu Liu; Bei-Hai He; Jin-Shan Fan (207-217).
To completely determine ferulic and p-coumaric acids and related phenolic compounds in the cell walls of sugarcane bagasse (SCB), a second mild alkaline hydrolysis of the alkali-soluble lignin preparations and acid hydrolysis of the 90% acidic dioxane-soluble lignin fractions were performed, which released 48.8% of the total ester-linked p-CA and 43.8% of the total esterified FA from the alkali-soluble lignin fractions, and 38.8% of the total ether-linked p-CA and 38.5% of the total ether-linked FA from the 90% acidic dioxane-soluble lignin preparations, respectively. Based on the dry weight, it has been found that the SCB contained 1.76% p-CA and 1.29% FA as well as minor quantities of related phenols. Further study of the solubilized lignin samples by combining with UV and FT-IR spectroscopy, and 1H and 13C NMR spectroscopy confirmed that a predominant amount of p-CA (69.5–76.4%) is ester-linked to the cell wall components, mainly to lignin. On the other hand, about half of the FA (44.0–55.0%) is esterified to the cell wall hemicelluloses, and the remaining half of the FA is also be etherified through the phenolic oxygen to lignin component in the cell walls of SCB.
Keywords: Ferulic acid; p-Coumaric acid; Phenolic compounds; Sugarcane bagasse; NMR;
Analysis and modelling of wicking through carton liquid packaging by Long Lin; Helio R. Jorge (218-225).
One of the more important issues in carton liquid packaging systems is the wicking of liquid content through the carton (usually coated with polymeric films) packaging. A suitable carton packaging for liquid content should have slow rate of wicking to provide satisfactorily long shelf life of the packaged product. In this study, the phenomenon of wicking of various liquid products, through coated carton packaging, was investigated. Thus, methods for the analysis of wicking through carton packaging had been developed. Mathematical models relating the rate of wicking to the physical–chemical properties of the liquid content and of the carton board were proposed. Model parameters for a widely used carton packaging material were obtained based on experimental data. The models obtained were proven capable of giving reliable correlation of the rate of wicking to the physical–chemical parameter of the liquid content and of the coated carton packaging.
Keywords: Wicking; Diffusion; Particle size analysis; Modelling of wicking; Carton packaging;
Author Index (226-227).