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Analytical and Bioanalytical Chemistry (v.367, #6)
Determination of low-molecular-weight carboxylic acids in the ambient air and vehicle emissions: a review by E. Dabek-Zlotorzynska; M. McGrath (pp. 507-518).
This review surveys analysis of airborne and vehicle emitted low-molecular-weight carboxylic acids. Attention is paid to providing a comprehensive coverage of collection techniques, sample handling, storage, extraction methods followed by a discussion of recent developments in carboxylic acid analysis using chromatographic (gas and ion chromatography) and electrophoretic (capillary electrophoresis) techniques. The occurrence and sources of carboxylic acids in the ambient air are also summarized.
Progress in pulsed-current Karl Fischer coulometry using diaphragm-free cells by U. Nordmark; A. Cedergren (pp. 519-524).
Factors influencing the accuracy of water determinations using diaphragm-free, pulsed current Karl Fischer (KF) coulometry were investigated with the new Metrohm 756 instrument. Results obtained with commercially available reagents from Riedel-deHaën and Merck were compared with home-made ones that were especially designed to minimize the formation of iodine-consuming reduction products generated in the cathode reaction. Positive errors in the range 2–5% were found for the commercial reagents as compared to 0.2–1% for the home-made ones which were buffered at about pH 10 containing modifiers like chloroform, hexanol or ethylene glycol. Except for the composition of the KF-reagent, the cathode current density and the titration rate were found to be critical parameters for the accuracy of the determinations. For all reagents investigated, the best results were obtained for the maximum generator current 400 mA (corresponding to a current density of 1400 mA cm–2) in combination with a maximum titration rate of 2000 μg min–1. Surprisingly, the errors found under optimum conditions for the pulse technique were always somewhat larger than the corresponding values obtained with continuous coulometry.
A novel method to calculate the approximate derivative photoacoustic spectrum using continuous wavelet transform by X. Shao; C. Pang; Q. Su (pp. 525-529).
A novel method based on continuous wavelet transform (CWT) using Haar wavelet function for approximate derivative calculation of analytical signals is proposed and successfully used in processing the photoacoustic signal. An approximate nth derivative of an analytical signal can be obtained by applying n times of the wavelet transform to the signal. The results obtained from four other different methods – the conventional numerical differentiation, the Fourier transform method, the Savitzky-Golay method, and the discrete wavelet transform (DWT) method – were compared with the proposed CWT method; it was demonstrated that all the results are almost the same for signals without noise, but the proposed CWT method is superior to the former four methods for noisy signals. The approximate first and second derivative of the photoacoustic spectrum of Pr(Gly)3Cl3· 3 H2O and PrCl3· 6 H2O were obtained using the proposed CWT method; the results are satisfactory.
Neutral bidentate organophosphorus compounds as novel ionophores for potentiometric membrane sensors for barium(II) by Mohamed Besis Saleh (pp. 530-534).
Bis(diarylphosphine oxide) naphthalene compounds are used as novel ionophores in plasticized poly(vinyl chloride) matrix membrane sensors for barium ions. The most favorable sensor was 1,2-bis(diethylphenylphosphine oxide)naphthalene containing potassium tetrakis(4-chlorophenyl)borate as lipophilic salt and o-nitrophenyloctyl ether as plasticizer for ion-selective electrode membrane construction. The electrode showed excellent properties. It gave a linear response with a Nernstian slope of 30 mV per decade within the concentration range 10–1–10–5 mol L–1 BaCl2. The electrode exhibits a high selectivity towards Ba2+ with respect to Li+, Na+, K+, Rb+, Cs+, NH4 +, Ag+, Mg2+, Ca2+, Sr2+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Pb2+, Al3+, La3+, and Ce3+ ions. The electrode response was stable over a wide pH range (3–11). The lifetime of the electrode was about 2 months. It was successfully applied to the determination of Ba2+contents in some rocks.
Selective electrodes for silver based on polymeric membranes containing calix[4]arene derivatives by Langxing Chen; Xianshun Zeng; Xiwen He; Zhengzhi; Zhang (pp. 535-538).
Silver ion-selective electrodes were prepared with polymeric membranes based on two calix[4]arene derivatives functionalized by two hydroxy and two benzothiazolylthioethoxy groups. The electrodes all gave a good Nernstian response of 58 mV decade–1 for silver in the activity range 5 × 10–6–10–1 M, the limits of detection reached 10–5.8 M and exhibited high selectivity towards alkali, alkaline earth and some transition metal ions. The electrode was used as indicator electrode in titrations of Ag+ with Cl– ion.
An amperometric biosensor based on the coimmobilization of horseradish peroxidase and methylene blue on a β-type zeolite modified electrode by Baohong Liu; Zhenjiu Liu; Dandan Chen; Jilie Kong; Jiaqi Deng (pp. 539-544).
A new biosensor for the amperometric detection of hydrogen peroxide was developed based on the co-immobilization of horseradish peroxidase (HRP) and methylene blue on a β-type zeolite modified glassy carbon electrode without the commonly used bovine serum albumin-glutaraldehyde. The intermolecular interaction between enzyme and zeolite matrix was investigated using FT-IR. The cyclic voltammetry and amperometric measurement demonstrated that methylene blue co-immobilized with HRP in this way displayed good stability and could efficiently transfer electrons between immobilized HRP and the electrode. The sensor responded rapidly to H2O2 in the linear range from 2.5 × 10–6 to 4.0 × 10–3 M with a detection limit of 0.3 μM. The sensor was stable in continuous operation.
Determination of carbaryl and biphenyl through optical fiber ccd-assisted flash lamp induced room temperature phosphorescence by A. Ghauch (pp. 545-550).
A fiber-optic sensor for solid surface room temperature phosphorescence of carbaryl and biphenyl pesticides was designed. A xenon flash lamp was used as excitation source, and a cooled two-dimensional charge coupled device was employed as the detector. Room temperature phosphorescence spectra of carbaryl and biphenyl were recorded by an imaging spectrograph. Limits of detection at the picogram/spot level were obtained for the investigated compounds. The linear dynamic range extended over three orders of magnitude. The standard addition method and the internal standard method were employed to analyze the studied compounds in mixtures. The feasibility of the SS-RTP apparatus developed was evaluated by the identification of carbaryl in a real sample.
Bulk acoustic wave sensor for herbicide assay based on molecularly imprinted polymer by Chengdu Liang; Hui Peng; Lihua Nie; Shouzhuo Yao (pp. 551-555).
A novel molecularly imprinted polymer (MIP) coated bulk acoustic wave (BAW) sensor was fabricated for liquid phases. It can be used as a sensitive portable implement for the assay of 2,4-dichlorophenoxyacetic acid. A logarithmic response relationship between 2.0 × 10–7 M and 5.0 × 10–4 M was found. The detection limit was 1.0 × 10–7 M. Recoveries were 93.2–108.7%. Influencing factors were investigated in detail and optimized.
Fourier transform infrared determination of CO2 evolved from carbonate in carbonated apatites by A. R. Cassella; R. C. de Campos; S. Garrigues; M. de la Guardia; A. Rossi (pp. 556-561).
A quantitative method based on FTIR has been developed to determine carbonate in synthetic apatites. The method measures the evolved CO2 after reaction of 50 mg apatite with 2 mL of hydrochloric acid (0.5 M) in a reaction vessel, heated to 40 °C. The CO2 evolved was swept by a carrier of nitrogen to a laboratory-made infrared gas cell of 39 mm pathlength and 490 μL volume. The signals were recorded as a function of time and the areas of the chemigram peaks obtained from the measurements in the wavenumber range of 2500–2150 cm–1, were interpolated using a calibration curve. The method can be used to study apatites with carbonate contents below 0.2% with a sampling frequency of 8 h–1.
Amberlite XAD-7 impregnated with Xylenol Orange: a chelating collector for preconcentration of Cd(II), Co(II), Cu(II), Ni(II), Zn(II) and Fe(III) ions prior to their determination by flame AAS by P. K. Tewari; A. K. Singh (pp. 562-567).
A new chelating resin, Xylenol Orange coated Amberlite XAD-7, was prepared and used for preconcentration of Cd(II), Co(II), Cu(II), Fe(III), Ni(II) and Zn(II) prior to their determination by flame atomic absorption spectrophotometry. The optimum pH values for quantitative sorption of Cd(II), Co(II), Cu(II), Fe(III), Ni(II) and Zn(II) are 4.5–5.0, 4.5, 4.0–5.0, 4.0, 5.0 and 5.0–7.0, respectively, and their desorptions by 2 mol L–1 HCl are instantaneous. The sorption capacity of the resin has been found to be 2.0, 2.6, 1.6, 1.6, 2.6 and 1.8 mg g–1 of resin for Cd, Co, Cu, Fe, Ni and Zn, respectively. The tolerance limits of electrolytes, NaCl, NaF, NaI, NaNO3, Na2SO4 and of cations, Mg2+ and Ca2+ in the sorption of the six metal ions are reported. The preconcentration factor was between 50 and 200. The t1/2 values for sorption are found to be 5.3, 2.9, 3.2, 3.3, 2.5 and 2.6 min for the six metals, respectively. The recoveries are between 96.0 and 100.0% for the different metals at preconcentration limits between 10 to 40 ng mL–1. The preconcentration method has been applied to determine the six metal ions in river water samples after destroying the organic matter (if present in very large amount) with concentrated nitric acid (RSD ≤ 8%, except for Cd for which it is upto 12.6%) and cobalt content of vitamin tablets with RSD of ∼ 3.0%.
Gas-chromatographic determination of chlorostyrene and dichlorostyrene isomers in workplace air by Ivan Makhniashvili; Ewa Kozieł (pp. 568-571).
Conditions for a gas-chromatographic determination of vapors and aerosols of p-chlorostyrene and 2,6-dichlorostyrene contained in workplace air samples were determined. The method is based on the adsorption of p-chlorostyrene and 2,6-dichlorostyrene on activated charcoal and fiberglass, desorption with toluene and analysis of the obtained solution by capillary gas chromatography with flame ionization detection (FID). The determination limit of the method is 5 mg m–3 for each substance.
Supercritical fluid extraction of polycyclic aromatic hydrocarbons from liver samples and determination by HPLC-FL by S. González Amigo; M. S. García Falcón; M. A. Lage Yusty; J. Simal Lozano (pp. 572-578).
An extraction/clean-up procedure by SFE was developed for isolating PAHs from liver samples for subsequent HPLC-FL determination of ten PAHs in the enriched extract. Recoveries (90–115%) and RSD % (≤ 7.7) were satisfactory. When applied to 11 samples of bird of prey (Tyto alba) protected species and classified of special interest, from the Galicia (Northwest to Spain), benzo[ghi]perylene and indeno[1,2,3-cd]pyrene were undetectable; chrysene and benzo[a]pyrene are only detected in one sample; benzo[a]anthracene and benzo[k]fluoranthene are only quantified in one sample and benzo[b]fluoranthene in two samples. The other PAHs, anthracene, fluoranthene and pyrene are present in almost all the samples.
Spatial determination of elements in green leaves of oak trees (Quercus robur) by laser ablation-ICP-MS by E. Hoffmann; C. Lüdke; J. Skole; H. Stephanowitz; E. Ullrich; D. Colditz (pp. 579-585).
Laser ablation inductively coupled plasma mass spectrometry (laser ablation-ICP-MS) has been applied to the spatially resolved determination of the elements Mg, Ca, Cu, Ni, Ba, Al, Pb, Sr and Mn in green leaves of oak trees. Instrument operating parameters such as the laser wavelength and the pulse energy have been optimized to provide the sensitivity and reproducibility required for the analysis. The method provides spatial resolution down to 300 μm with the use of the 355 nm wavelength (3rd harmonic of the 1064 nm Nd:YAG laser wavelength) and the pulse energy of 50 mJ. Plant standards and cellulose, doped with multi element solution standards, dried and pressed to pellets were used as calibration samples. To compensate for signal fluctuations caused by the variation of the ablated sample mass 13C was used as a “natural” internal standard. The accuracy of the calibration was verified with selected samples analyzed by ICP-MS (high pressure digestion, 170 °C, 107 Pa, HNO3, 2 h) and by laser ablation-ICP-MS. Recovery rates between 93% (Cu) and 108% (Mn) were obtained. Leaves taken from oak trees (Quercus robur) were analyzed.
Classification of ancient Roman glazed ceramics using the neural network of Self-Organizing Maps by A. Lopez-Molinero; A. Castro; J. Pino; J. Perez-Arantegui; J. R. Castillo (pp. 586-589).
Artificial neural networks with unsupervised learning strategy known as Self-Organizing Maps were applied to classify ancient Roman glazed ceramics. Their clay ceramic bodies were analyzed by Inductively Coupled Plasma-Atomic Emission Spectroscopy and the chemical composition obtained was processed by this neural algorithm. The results obtained provide two types of information: firstly, classification of ceramic samples with identification of several groups and secondly, differentiation between the elemental chemical information. It was found that there are certain chemical elements which can be considered as principal and which can serve to differentiate between ceramics, whereas other elements give redundant information and do not contribute to sample differentiation. Seven chemical elements were considered principal and provide the necessary information. Two types of element were identified: 1 – a group formed by common elements, such as: Ca, Fe, Mg, Mn and 2 – another formed by optional elements: K or Na and Ba or Sr and Al or Ti.
Flow injection spectrophotometric determination of ultra trace amounts of oxalic acid by A. A. Ensafi; A. Kazemzadeh (pp. 590-592).
A new simple, sensitive and rapid catalytic-spectrophotometric method for the determination of oxalic acid has been described based on its catalytic effect on the redox reaction between dichromate and Brilliant cresyl blue in acidic media by means of a flow injection analysis method. The color change of Brilliant cresyl blue due to its oxidation was monitored spectrophotometrically at 625 nm. The calibration graph was linear in the range of 0.020–4.70 μg/mL oxalic acid with a limit of detection 0.005 μg/mL of oxalic acid. The relative standard deviation for ten replicate measurements of 0.020 μg/mL and 0.900 μg/mL was 2.2% and 1.7%, respectively. No serious interference was identified. Oxalic acid was determined in wastewater and in spinach by the proposed method with satisfactory results.
Ferrocenecarboxaldehyde labeled DNA probe for the study on DNA damage and protection by C. Xu; H. Cai; P. He; Y. Fang (pp. 593-595).
A ferrocenecarboxaldehyde (FCA) labeled DNA probe is used for the first time in the study of DNA damage and protection. The electrochemically active reagent FCA was labeled successfully on to a denatured calf-thymus DNA by ¶1-ethyl-3- (3-dimethyl-aminopropyl) carbodiimide (EDC). The FCA labeled DNA probe was used to hybridize with the sample DNA sequence accumulated on the surface of a graphite electrode. The anodic peaks of the FCA bound to the double-stranded DNA (dsDNA) by differential pulse voltammetry (DPV) were used for the detection of DNA damage and protection. Thiourea, sodium benzoic acid and isopropanol can decrease DNA damage by hydroxyl radicals, and their protection efficiencies are discussed.
Determination of paracetamol (acetaminophen) in different body fluids and organ samples after solid-phase extraction using HPLC and an immunological method by E. Pufal; M. Sykutera; G. Rochholz; H. W. Schütz; K. Sliwka; H.-J. Kaatsch (pp. 596-599).
A solid-phase extraction method routinely used for serum samples was improved and applied to the qualitative and quantitative determination of paracetamol in different body fluids, e.g. blood, urine, cerebrospinal fluid, synovial fluid, vitreous humor, and in tissue samples. A very simple method showed best results: Body fluids were mixed with phenacetine as internal standard and phosphate buffer (pH 6.8). Then protein was precipitated using acetonitrile. After strong centrifugation the supernatant was transferred to a preconditioned Bakerbond C18-SPE-column. Elution with methanol without a prior washing step showed best recovery rates. The extracts were investigated using high-performance liquid chromatography with ultraviolet detection, a photometrical and an immunochemical method.