Analytica Chimica Acta (v.488, #2)

Room temperature phosphorescence in the liquid state as a tool in analytical chemistry by Jacobus Kuijt; Freek Ariese; Udo A.Th. Brinkman; Cees Gooijer (135-171).
Keywords: Room temperature phosphorescence; Luminescence; Lanthanides; Liquid state; Analytical applications;

Ion imprinted polymer (IIP) materials with nanopores were prepared by formation of ternary complex of palladium imprint ion with dimethylglyoxime (DMG) and 4-vinylpyridine (VP, functional monomer) and thermally copolymerizing with styrene (crosslinking monomer) and divinylbenzene (cross linker) and 2,2′-azobisisobutyronitrile as initiator. The synthesis was carried out with cyclohexanol as porogen and subsequently leached with 50% (v/v) HCl to obtain leached IIP particles. These leached IIP particles can now pick up palladium ions from dilute aqueous solutions. The optimal acidity for quantitative enrichment was 0.2–0.4N HCl and eluted completely by stirring for 15 min with 2×10 ml of 50% (v/v) HCl. The palladium ion imprinting polymer gave 100 times higher distribution ratio than ion recognition (blank) polymer (IRP). Further, percent extraction, distribution ratio and selectivity coefficients of palladium and other selected inorganic ions using IRP and IIP particles were determined and compared. Five replicate determinations of 50 μg of palladium in 1 l of solution gave a mean absorbance of 0.200 with a relative standard deviation of 2.12%. The detection limit corresponding to three times the standard deviation of the blank was 2.5 μg of palladium/l.
Keywords: Ion imprinting polymer particles; Palladium ion; Preconcentration; Separation;

Room temperature ionic liquids (RTILs) have been used as novel solvents to replace traditional volatile organic solvents in organic synthesis, solvent extraction, and electrochemistry. The hydrophobic character and water immiscibility of certain ionic liquids allow their use in solvent extraction of hydrophobic compounds. In this work, a typical room temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate [C4mim][PF6], was used as an alternative solvent to study liquid/liquid extraction of heavy metal ions. Dithizone was employed as a metal chelator to form neutral metal–dithizone complexes with heavy metal ions to extract metal ions from aqueous solution into [C4mim][PF6]. This extraction is possible due to the high distribution ratios of the metal complexes between [C4mim][PF6] and aqueous phase. Since the distribution ratios of metal dithiozonates between [C4mim][PF6] and aqueous phase are strongly pH dependent, the extraction efficiencies of metal complexes can be manipulated by tailoring the pH value of the extraction system. Hence, the extraction, separation, and preconcentraction of heavy metal ions with the biphasic system of [C4mim][PF6] and aqueous phase can be achieved by controlling the pH value of the extraction system. Preliminary results indicate that the use of [C4mim][PF6] as an alternate solvent to replace traditional organic solvents in liquid/liquid extraction of heavy metal ions is very promising.
Keywords: Room temperature ionic liquid; 1-Butyl-3-methylimidazolium hexafluorophosphate; Solvent extraction; Metal ions extraction; Metal ions preconcentration;

The effect of β-cyclodextrin (CD) and hydroxypropyl-β-cyclodextrin (HPCD) in water solutions on the UV-Vis and fluorescence spectra of carbaryl (1-naphthyl-N-methylcarbamate, CY) and carbofuran (2,2-dimethyl,2-3-dihydro-7-benzofuranyl-N-methylcarbamate, CF) was investigated. Host–guest interactions were observed by UV-Vis and spectrofluorimetry and the association constants for the 1:1 complexes (K A, mol−1  dm3) with CD and HPCD were determined. The values obtained were 190±10 and 123±7 mol−1  dm3 for CF and 350±50 and 644±53 mol−1  dm3 for CY, respectively. The values of the fluorescence quantum yield ratios (φ complexed/φ free) were 1.24±0.01 with CD and 1.310±0.007 with HPCD for CY, but much higher for CF being 7.0±0.1 with CD and 9.3±0.4 with HPCD. The limits of detection (LOD) for the fluorimetric determination under the better conditions were 14.5 ng cm−3 for the complex CF:CD and 1.94 ng cm−3 for the complex CY:CD in water, with notable improvement specially in the case of CF. We observed higher analytical sensitivity with the cyclodextrins (CDs) in presence of alcohols but not better LOD. The method is rapid, simple, direct and sensitive and the recovery of CY and CF was found to be between 100 and 112% in fruits and 97 and 109% in tap water. The allowed level of carbamates in banana can be detected by the proposed method.
Keywords: Carbamate pesticides; Carbaryl; Carbofuran; Fluorimetric determination; Cyclodextrin;

Dansyl chloride (DNS-Cl) is a sulfonyl chloride compound which is utilized as a fluorescent probe for quantitative analysis or structural studies of complex molecules. The fluorescent emission was sufficiently strong to permit detection of less than 10 μg of the carboxyl compounds studied here. The dansylation of aromatic carboxyl compounds (i.e. aspirin), aromatic primary amines, and aliphatic carboxyl compounds was accomplished in 1 M Na2CO3 buffer at pH 11. The fluorescent labeled analytes were then isolated by thin layer chromatography (TLC) or the aqueous mixture was pre-extracted with proline (or glycine) to eliminate back-ground emission originating from the hydrolized or sulfonic acid form of DNS-Cl. Fluorescent labeled analytes are clearly discerned under ultraviolet light. Limits of detection for dansylated carboxyl compounds was 1–5 μg, however for amines it was approximately 1 μg. Dansylation of aromatic primary amines proceeded much faster (15 min) than that of carboxyl compounds (≥1.5 h) at 25 °C. Despite the aqueous solubility of analytes, which ranged from less than 0.004–5.30 mg/ml, the dansylation of carboxyl compounds was effective. Various organic solvents for extracting derivatives from aqueous mixture were evaluated.
Keywords: Carboxylic acid; Dansyl chloride; Fluorescence detection;

Liquid chromatographic determination of bisphenols based on intramolecular excimer-forming fluorescence derivatization by Hideyuki Yoshida; Hajime Harada; Hitoshi Nohta; Masatoshi Yamaguchi (211-221).
A highly selective and sensitive fluorometric method for the determination of bisphenols has been developed. This method is based on an intramolecular excimer-forming fluorescence derivatization with a pyrene reagent, 4-(1-pyrene)butyryl chloride (PBC), followed by reversed-phase liquid chromatography (LC). The bisphenols, containing two phenolic hydroxyl groups in a molecule, were converted to the corresponding dipyrene-labeled derivatives by reaction with PBC. The derivatives afforded intramolecular excimer fluorescence (440–520 nm) which can clearly be discriminated from normal fluorescence (360–420 nm) emitted from PBC and monopyrene-labeled derivatives of monophenols. The PBC derivatives of bisphenols could be separated by reversed-phase LC on an octyl column with isocratic elution. The detection limits (signal-to-noise ratio = 3) for bisphenols were 3.0–5.0 fmol, for a 20 μl injection. The method was successfully applied to the determination of bisphenol A in hot water in contact with commercially available baby bottle samples after solid-phase extraction.
Keywords: Excimer fluorescence; Liquid chromatography; Bisphenols; 4-(1-Pyrene)butyryl chloride; Baby bottle;

An improved HPLC-electrochemical detection (ED) method is described for the analysis of hydroxyurea (HU) in human plasma. After extraction process, HU was determined on a C18 column (250  mm×4  mm) by the mobile phase (25 mM sodium acetate–acetonitrile, 97.5:2.5; pH 6.5). The regression equations were linear (r>0.9990). The precision and accuracy of intra- and inter-batches were all below 5% for relative standard deviation (R.S.D.) and relative error (R.E.). Based on 20 μl of plasma, the limit of detection was 0.3 μM for HU (S/N=3, injection 10 μl). This method was applied for the HU drug monitoring of patients with myelofibrosis or polycythemia vera.
Keywords: Hydroxyurea; HPLC-ED; Patients;

In hyphenated chromatography, overlapping chromatographic peaks can be resolved into pure spectra and pure chromatographic profiles by several multivariate deconvolution techniques. In general, these methods require bilinearity, which implies that the spectrum of each analyte is constant. The slow scan speeds normally used in gas chromatography–mass spectrometry (GC–MS) will destroy bilinearity and introduce systematic noise in the data because the concentration in the detector changes during the scan. This effect, described as the scan effect, may hinder successful resolution by multivariate deconvolution. In selected ion monitoring (SIM) GC–MS, the scan effect may be removed by simple transformations of the mass spectra. The effects of different transformations are demonstrated both on pure chromatographic peaks and on difficult resolution problems where there are small differences between the spectra of the analytes.
Keywords: Gas chromatography–mass spectrometry; Multivariate curve resolution; GENTLE; Fatty acid methyl esters; Scan time;

Analyser of chromium and/or cobalt by L.A Tortajada-Genaro; P Campı́ns-Falcó; F Bosch-Reig (243-254).
Two stopped-flow manifolds have been proposed for individual or simultaneous determination of chromium and cobalt in water samples. Automated procedures based on multicommutation systems have emphasised the differences of their catalytic effect in luminol–hydrogen peroxide chemiluminescence reaction. A more rapid decay of signal was observed for Co for both configurations (flow injection or continuous injection). The influence of chemical and hydrodynamic variables has been studied in order to establish the robustness of method. The analysis rate was lower 1.5 min per replicate.Chemometric tools have been employed for the resolution of their contributions. Partial least squares (PLS) and H-point standard additions method (HPSAM) were used as multivariate calibration models. The percentages of explained variance were 97–99% (two factors). PLS and HPSAM obtained similar results. HPSAM provided a simple calibration model contributing to develop an analyser for chromium and/or cobalt.Standard mixtures, spiked samples and a certified reference material validated the proposed strategy. The applicability has been demonstrated by the determination of Cr and Co concentration in different water samples. The best results have been obtained for continuous injection providing more robust predictions. The achieved detection limit was 0.2 μg/l for both metals.
Keywords: Multicommutation; Chromium and cobalt; Simultaneous determination; Chemiluminescence; Water matrix; HPSAM; PLS;

Author Index (255-256).