On-line analysis of carbonyl compounds with derivatization in aqueous extracts of atmospheric particulate PM10 by in-tube solid-phase microextraction coupled to capillary liquid chromatography

A new device for carbonyl compounds based on coupling on-line and miniaturizing both, sample pretreatment and chromatographic separation, is reported. Two capillary columns, a GC capillary column (95% methyl-5% phenyl substituted backbone, 70 cm × 0.32 mm i.d., 3 μm film thickness) in the injection valve for in-tube solid-phase microextraction (IT-SPME) and a Zorbax SB C18 (150 mm × 0.5 mm i.d., 5 μm particle diameter) LC capillary column were employed. Different combinations of IT-SPME and derivatization using 2,4-dinitrophenylhydrazine (DNPH) were examined for mixtures containing 15 carbonyl compounds (aliphatic, aromatic and unsaturated aldehydes and ketones). A screening analysis of aqueous extracts of atmospheric particulate PM(10) was carried out. Moreover, the possibility of coupling IT-SPME and conventional liquid chromatography is also tested. Derivatization solution and IT-SPME coupled to capillary liquid chromatography provided the best results for achieving the highest sensitivity for carbonyl compounds in atmospheric particulate analysis. Detection limits (LODs) using a photodiode array detector (DAD) were ranged from 30 to 198 ng L(-1), improving markedly those LODs reported by conventional SPME-LC-DAD.     

Odour-causing organic compounds in wastewater treatment plants: evaluation of headspace solid-phase microextraction as a concentration technique

Odorous emissions from wastewater collection systems and treatment facilities affecting quality of life have given local populations reasons to complain for decades. In order to characterise the composition of such malodorous emissions, a method based on headspace solid-phase microextraction (HS-SPME) and gas chromatography coupled to mass spectrometry (GC-MS) has been developed to determine a list of compounds belonging to different chemical families, which have been previously described as potentially responsible for odour complaints, in wastewater matrices. Some parameters affecting the chromatographic behaviour of the target compounds were studied (e.g. splitless time). Experimental conditions affecting the extraction process (temperature, time and salt content) were evaluated by applying a factorial design at two levels. Using a DVB/CAR/PDMS fibre and the optimised HS-SPME conditions, calibration curves were constructed with detection limits in the range of 0.003-0.6 μg L(-1). Recovery values higher than 70% and relative standard deviation values between 5 and 16% (n=5) were obtained for all compounds and found to be satisfactory. In wastewater samples, a decrease in the concentration of the analysed compounds through the different treatments was observed. Most of the target analytes were found in influent samples while only octanal and carvone were detected in samples from the plant effluent.     

Problems caused by the activity of Al2O3-PLOT columns in the capillary gas chromatographic analysis of volatile organic compounds

Summary Al₂O₃-PLOT columns are used with great advantage for the analysis of volatiles, because of the increased capacity ratio and selectivity compared to WCOT-columns. Their applicability is limited to relatively non-polar components with relatively low boiling points i. e. eluting before n-decane.In the analysis of the halocarbons in stratospheric air, the decomposition of certain compounds was observed. In this study the stability of a number of volatile organic compounds was determined in function dependence of the column temperature using a two-dimensional GC-system.A possible reaction mechanism for the decomposition is proposed and confirmed for several chlorinated ethanes.     

A pre-enrichment procedure using diethyldithiocarbamate-modified TiO2 nanoparticles for the analysis of biological and natural water samples by ICP-AES

In this article, a new method that utilizes a diethyldithiocarbamate-modified nanometre TiO₂ (TiO₂–DDTC) as solid-phase extractant has been developed for simultaneous preconcentration of trace Cu(II), Pb(II), Zn(II), and Cd(II) prior to measurement by inductively coupled plasma atomic emission spectrometry (ICP-AES). The separation/preconcentration conditions of analytes, which include the effects of pH, sample flow rate and volume, elution conditions, and interfering ions on the recovery of the analytes, were investigated. At pH 5, the adsorption capacity of modified nanometre TiO₂–DDTC was found to be 6.2, 19, 4.7, and 6.0?mg/g for Cu(II), Pb(II), Zn(II), and Cd(II), respectively. According to the definition of IUPAC, the detection limits (3σ) of this method for Cu(II), Pb(II), Zn(II), and Cd(II) were 0.41, 1.7, 0.39, and 0.52?ng/mL, respectively. The proposed method achieved satisfied results when applied to the determinations of trace Cu(II), Pb(II), Zn(II), and Cd(II) in biological and natural water samples.     

On-line preconcentration and separation of Co, Ni and Cd via capillary microextraction on ordered mesoporous alumina coating and determination by inductively plasma mass spectrometry (ICP-MS)

In this paper, an ordered mesoporous alumina coating was prepared and applied to capillary microextraction (CME) of trace Co, Ni and Cd for the first time. The coated capillary was used for on-line coupling CME with inductively plasma mass spectrometry (ICP-MS) for the determination of trace metals of Co, Ni and Cd. The porous structure of Al₂O₃ coating was examined by SEM and TEM. The effects of the extraction parameters including pH, sample flow rate and volume, elution solution and interfering ions on the recovery of analytes have been investigated and optimized. Under the optimized conditions, the limits of detection were 0.33, 1.5 and 1.4 ng L⁻¹ for Co, Ni and Cd, respectively, with a preconcentration factor of 10 times. The precisions for all investigated elements were 2.7, 4.1 and 2.5% (c = 0.05 ng L⁻¹, n = 7), for Co, Ni and Cd, respectively, and the sample frequency was 8 h⁻¹.The proposed method was successfully applied for the analysis of trace metals in water, rice and urine samples with the recovery of 94-105%. In order to validate the proposed method, two certified reference materials of GBW 0913 human urine and NIES No.10-b rice flour were analyzed, and the determination values are in good agreement with the certified values. The ordered mesoporous Al₂O₃ coated capillary can be used more than 20 times without decreasing the extraction efficiency.     

Application of the Composite of TiO2 Nanoparticles and Carbon Nanotubes to the Photo-Reduction of Cr(VI) in Water

The composite of carboxyl-modified multi-walled carbon nanotubes (MWNT-COOH) and TiO₂ nanoparticles was prepared in a solvothermal process. The x-ray diffraction (XRD), transmission electron microscope (TEM) and UV-vis spectrum were used to characterize the products. The results showed that the MWNT-COOH was dispersed uniformly in the composite and coated with TiO₂ nanoparticles. The photo-reduction of Cr(VI) to Cr(III) in water catalyzed by the composite was investigated at room temperature. The photocatalytic activity of the composite markedly increased by a factor of approximately 2.2 in comparison with pure TiO₂ (P25). Furthermore, the mechanism of the photocatalytic activity enhancement of the MWNT-COOH/TiO₂ nanoparticles composite for the photo-reduction of Cr(VI) was discussed.     

A rapid microwave-assisted acid extraction method based on the use of diluted HNO3-H2O2 followed by ICP-MS analysis for simultaneous determination of trace elements in coal samples

Before coal processing such as pyrolysis, liquefaction, gasification and combustion, it is very crucial to monitor the trace element concentration levels as that determines the coal quality. Therefore, the current study describes the development of microwave-assisted acid extraction (MW-AAE) method for extraction of 15 trace elements in coal samples prior to their determination using inductively coupled plasma-mass spectrometry. Diluted HNO₃-H₂O₂ was used in order to reduce reagents amount used, eliminate matrix interferences caused by concentrated acids and to decrease waste produced in analytical laboratories. The optimisation of the proposed extraction method was carried out by using a full factorial design (2⁴) involving four factors; that is, temperature, extraction time, HNO₃ and H₂O₂ concentrations. The optimum conditions for the MW-AAE procedure were found to be 200°C, 5 min, 5 mol L^?1 and 2 mol L^?1 for temperature, extraction time, HNO₃ and H₂O₂ concentrations, respectively. Under optimum conditions, the accuracy of the MW-AAE method was examined by analysing three coal certified reference materials (SARM 18, 19 and 20) and recoveries of 80–115% were achieved for V, Mn, Co, Ni, Cu, Zn, Ga, Ge, As, Sr, Zr, Cs, Ba, Pb and U, except for Ti (10–25%) and Hf (27–70%). In addition, the precision of the proposed method, expressed in terms of relative standard deviation (SD) (n = 15), was within the accepted range (≤3.5%). The method detection limits of 0.001–0.57 µg g^?1 for all trace elements under the investigation were similar to the literature reported work, except for Ti (4.00 µg g^?1).     

Capillary electrophoresis procedure for the simultaneous analysis and stoichiometry determination of a drug and its counter-ion by using dual-opposite end injection and contactless conductivity detection: Application to labetalol hydrochloride

In this work, a capillary electrophoresis (CE) procedure was developed for the simultaneous determination of a pharmaceutical drug and its counter-ion, namely labetalol hydrochloride. For this purpose, an uncoated fused-silica capillary, a low conductivity background electrolyte (BGE) and a capacitively coupled contactless conductivity detector (C⁴D) were employed. This detection system is highly sensitive and enables detection of inorganic as well as organic ions unlike with direct UV detection. Moreover, to be able to simultaneously analyze the cationic drug (labetalol⁺) and its anionic counter-ion (Cl⁻) in the same electrophoretic run without the need of a coated capillary, a dual-opposite end injection was performed. In this technique, the sample is hydrodynamically injected into both ends of the capillary. This method is simple and easy to perform since the different injection steps are automated by the CE software.This novel CE-C⁴D procedure with dual-opposite end injection has been successfully validated and applied for the analysis of chloride content in an adrenergic antagonist (labetalol hydrochloride). Thus, the hereby developed method has been shown to enable fast (analysis time < 10 min), precise (repeatability of migration times < 0.7% and of corrected-peak areas < 3.3%; n = 6) and rugged analyses for the simultaneous determination of a pharmaceutical drug and its counter-ion.     

Degradation of organic compounds on TiO<Subscript>2</Subscript> photocatalysts prepared by a hydrothermal method in the presence of NH<Subscript>4</Subscript>F

TiO₂ photocatalysts were synthesized by a hydrothermal method from tetraisopropyl orthotitanate (TPOT) in the presence of NH₄F with different NH₄F/Ti molar ratios (0, 0.25, and 1). The formation of a well-crystallized anatase phase of TiO₂ and the suppression of phase transition to rutile were observed, even at high calcination temperature, owing to the effects of NH₄F. The TiO₂ synthesized hydrothermally with NH₄F exhibited absorption with a shift to the longer wavelengths of the visible-light region. The hydrothermally synthesized TiO₂ with a moderate amount of NH₄F exhibited high photocatalytic activity for the degradation of alcohol diluted in water under both UV-light and visible-light irradiations.     

Liquid chromatography coupled to on-line post column derivatization for the determination of organic compounds: A review on instrumentation and chemistries

Analytical derivatization either in pre or post column modes is one of the most widely used sample pretreatment techniques coupled to liquid chromatography. In the present review article we selected to discuss the post column derivatization mode for the analysis of organic compounds. The first part of the review focuses to the instrumentation of post-column setups including not only fundamental components such as pumps and reactors but also less common parts such as static mixers and back-pressure regulators; the second part of the article discusses the most popular “chemistries” that are involved in post column applications, including reagent-less approaches and new sensing platforms such as the popular gold nanoparticles. Some representative recent applications are also presented as tables.     

Sensitive determination of verticine and verticinone in Bulbus Fritillariae by ionic liquid assisted capillary electrophoresis-electrochemiluminescence system

CE/Ru(bpy)₃²⁺ electrochemiluminescence (ECL) system with the assistance of ionic liquids (ILs) was successfully established for sensitive determination of verticine and verticinone in Bulbus Fritillariae for the first time. Migration behavior of alkaloid largely relies on the hydrogen bonding interactions between alkyl imidazolium cations in ILs and the alkaloids. Running buffer containing 40 mmol/L 1-butyl-3-methylimidazolium tetrafluoroborate (BMImBF₄) IL-8 mmol/L phosphate resulted in significant changes in separation selectivity for alkaloids with similar structures. The highest sensitivity of the detection was obtained by maintaining the detection potential at 1.2 V. Under the optimized conditions, relative standard derivations of the ECL intensity and the migration time were 3.27 and 2.84% for verticine and 4.42 and 1.69% for verticinone, respectively. The standard curves were linear between 1 × 10⁻⁸ and 1 × 10⁻⁶ mol/L for verticine and between 5 × 10⁻⁸ and 1 × 10⁻⁶ mol/L for verticinone, respectively. Detection limits of 1.25 × 10⁻¹⁰ mol/L for verticine and 1 × 10⁻¹⁰ mol/L for verticinone were obtained (S/N = 3). Developed method was successfully applied to determine the amounts of alkaloids in Bulbus Fritillariae.     

UV-assisted degradation of propiconazole in a TiO2 aqueous suspension: identification of transformation products and the reaction pathway using GC/MS

Photocatalytic degradation of propiconazole, a triazole pesticide, in the presence of titanium dioxide (TiO₂) under ultraviolet (UV) illumination was performed in a batch type photocatalytic reactor. A full factorial experimental design technique was used to study the main effects and the interaction effects between operational parameters in the photocatalytic degradation of propiconazole in a batch photo-reactor using the TiO₂ aqueous suspension. The effects of catalyst concentration (0.15–0.4 gL^?1), initial pH (3–9), initial concentration (5–35 mg L^?1) and light conditions were optimised at a reaction time duration of 90 min by keeping area/volume ratio constant at 0.919 cm² mL^?1. Photocatalytic oxidation of propiconazole showed 85% degradation and 76.57% mineralisation under UV light (365 nm/30 Wm^?2) at pH 6.5, initial concentration 25 mg L^?1 and constant temperature (25 ± 1 °C). The Langmuir–Hinshelwood kinetic model has successfully elucidated the effects of the initial concentration on the degradation of propiconazole and the data obtained are consistent with the available kinetic parameters. The photocatalytic transformation products of propiconazole were identified by using gas chromatography–mass spectrometry (GC/MS). The pathway of degradation obtained from mass spectral analysis shows the breakdown of transformation products into smaller hydrocarbons (m/z 28 and 39).     

Study on photocatalytic oxidation for determination of the low chemical oxygen demand using a nano-TiO2-Ce(SO4)2 coexisted system

A new photocatalytic system, nano-TiO₂-Ce(SO₄)₂ coexisted system, which can be used to determine the low chemical oxygen demand (COD) is described. Nano-TiO₂ powders is used as photocatalyst in this system. The measuring method is based on direct determination of the concentration change of Ce(IV) resulting from photocatalytic oxidation of organic compounds. The mechanism of the photocatalytic oxidation for COD determination was discussed and the optimum experimental conditions were investigated. Under the optimum conditions, a good calibration graph for COD values between 1.0 and 12 mg l⁻¹ was obtained and the LOD value was achieved as low as 0.4 mg l⁻¹. When determining the real samples, the results were in good agreement with those from the conventional methods.     

Some characteristics of a protein-coated ODS column and its use for the determination of drugs by the direct injection analysis of plasma samples

Summary It was found that an ODS column of small pore (120?) which was coated with denatured plasma proteins (protein-coated ODS) no longer adsorbed plasma proteins from aqueous solution but retained the characteristics of native ODS for small hydrophobic molecules. Elemental analysis and nitrogen desorption (BET) analysis showed that the protein-coated ODS contained ca 25 mg proteing⁻¹ dry resin and that the pore diameter or pore volume was similar to that of native ODS. The coated denatured proteins, which seemed to be adsorbed on the external surface of the porous resin, were not eluted under usual reverse-phase elution conditions. Operating as either an analytical column or a pre-column, this protein-coated ODS column was used to analyse spiked-drugs in plasma. The recovery of all the spiked-drugs (such as doxorubicin, methotrexate) was almost quantitative (98–102%) with good reproducibilities (c.v., less than 2%). The present method was useful for the determination of total, that is, free + bound-to-plasma-proteins, hydrophobic drugs in plasma in view of its accuracy and simplicity. Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984     

Development of a methodology for the simultaneous determination of inorganic and organolead compounds using supercritical fluid extraction followed by gas chromatography-mass spectrometry and its application to environmental matrices

A method for the extraction of triethyl lead (TEL⁺), trimethyl lead (TML⁺), and Pb²⁺ from sand was developed using supercritical modified CO₂-CH₃OH extraction and in situ complexation with sodium diethyldithiocarbamate (NaDDTC) using a 2⁵ factorial exploratory design is described. The screened variables were (i) pressure (69-193 bar), (ii) temperature (40-150 °C), (iii) ligand amount (0-100 mg), (iv) methanol volume (0.0-0.5 mL) and (v) static time (0-45 min). The optimum extraction conditions found were as follow: pressure, 193 bar; temperature, 40 °C; amount of NaDDTC, 100 mg; methanol volume, 0.5 mL; static time 45 min; and CO₂ flow rate, 1 mL min⁻¹. Under these conditions the following recoveries were obtained (TML⁺ 97 ± 2%, TEL⁺ 70 ± 5%, and Pb²⁺ 100 ± 4%). The presence of NaDDTC is not necessary for the extraction of TML⁺ and TEL⁺, but it is a very significative parameter for Pb²⁺. A second experimental design 2² + star for temperature and pressure was realized, but the results were not better than those of the first model. SFE extract derivatization was achieved with pentylmagnesium bromide, and target analyte determination was carried out by gas chromatography-mass spectrometry. Detection limits in the full-scan mode were 4, 10, and 39 pg as lead for TMPeL, TEPeL and PbPe₄, respectively. The method was validated with urban dust containing TML⁺ (CRM 605. Pb 7.9 ±1.2 μg kg⁻¹) and river sediment containing inorganic lead (GBW08301. Pb 79.0 ± 12.0 mg kg⁻¹) as reference materials. The proposed method was applied to lead analysis in sand collected from an oil-polluted beach in Chile.     

Coordination compounds with XeF2, AsF3 and HF as ligands to metal ions: a review of reaction systematics, Raman spectra and metal, fluoro-ligand polyhedra

The reactions between Ln(AsF₆)₃ (Ln: lanthanide) and excess of XeF₂ in anhydrous HF (aHF) as a solvent yield coordination compounds [Ln(XeF₂)₃](AsF₆)₃ or LnF₃ together with Xe₂F₃AsF₆ or mixtures of all mentioned products depending on the fluorobasicity of XeF₂ and LnF₃ along the series. XeF₂ in a basic aHF is able to oxidize Pr³⁺ to Pr⁴⁺ besides Ce³⁺ to Ce⁴⁺ and Tb³⁺ to Tb⁴⁺. The tetrafluorides obtained are weaker fluorobases as XeF₂ and are immediately exchanged with XeF₂ yielding Xe₂F₃AsF₆ and LnF₄. The analogous reaction between Ln(BiF₆)₃ and XeF₂ in aHF yields [Ln(XeF₂)₃](BiF₆)₃, Ln: La, Nd. Raman spectra of the compounds [Ln(XeF₂)_n](AF₆)₃ (A: As, Bi) show that no XeF⁺ salts are formed. The interaction of XeF₂ with metal ion is covalent over the fluorine bridge. Analogous reactions of Ln(AsF₆)₃ with AsF₃ in aHF yield [Ln(AsF₃)₃](AsF₆)₃ which are stable in a dynamic vacuum at temperatures lower than 233 K. In reactions between M(AF₆)₂ (M: alkaline earth metal and Pb, A: As, Sb) and XeF₂ in aHF as a solvent, compounds of the type [M(XeF₂)_n](AF₆)₂ were synthesized. Analogous reactions with AsF₃ yield coordination compounds of the type [M(AsF₃)_n](AsF₆)₂. During the preparation of M^x(AsF₆)_x (M: metal in oxidation state x+) by the reaction between metal fluoride and excess of AsF₅ in aHF it was found that HF could also act as a ligand to the metal ions (e.g. Ca(HF)(AsF₆)₂).     

Modeling the active centers of V<Subscript>2</Subscript>O<Subscript>5</Subscript>/SiO<Subscript>2</Subscript> and V<Subscript>2</Subscript>O<Subscript>5</Subscript>/TiO<Subscript>2</Subscript> supported catalysts. DFT theoretical analysis of optical properties

Within the framework of the density functional theory (DFT), the electronic structure of monooxodioxovanadium functional groups in tetrahedral coordination, which model the active centers (ACs) of fine supported catalysts V₂O₅/SiO₂ and V₂O₅/TiO₂, has been analyzed. The optimal structures of three ACs as possible models of monomeric and polymeric oxovanadium forms on the carriers with low vanadium content were determined. The modified DFT method involving the time dependence of Kohn-Sham equation (TDDFT) was used for the adopted AC models to calculate the energies of the excited states, and optical spectra of the absorption in 25000–60000 cm^?1 region were reconstructed on their base. The spectrum in this region is due to O → V charge transfer. The features of electronic spectra with the charge transfer for V₂O₅/SiO₂ and V₂O₅/TiO₂ catalysts and the vibrational spectra of three AC models corresponding to the monomeric and dimeric oxovanadium forms of the supported catalysts V₂O₅/SiO₂ and V₂O₅/TiO₂ were defined. The detailed interpretation of normal vibration frequencies is given. The frequencies typical of the monomeric and dimeric oxovanadium forms on the carrier surface were identified.     

Simultaneous capillary electrophoretic determination of Sc(III) and Y(III) based on the complex-formation with a lacunary Keggin-type [PW11O39] complex

Trace amounts of Sc(III) and Y(III) can react with [PW₁₁O₃₉]⁷⁻ to form the ternary Keggin-type complexes: [P(Sc^IIIW₁₁)O₄₀]⁶⁻ and [P(Y^IIIW₁₁)O₄₀]⁶⁻ having high molar absorptivities in the UV region. Since the rate of the complex-formation was very rapid and the kinetically stable ternary anions migrated in the capillary with different electrophoretic mobilities, the complex-formation reaction was applied to the simultaneous CE determination of Sc(III) and Y(III) with direct UV detection at 250 nm. For both Sc(III) and Y(III), the pre-column method provided linear calibration curves in the range of 2 × 10⁻⁷ to 1 × 10⁻⁵ M; the respective detection limits were 1 × 10⁻⁷ M (the signal-to-noise ratio = 3). The proposed method was successfully applied to the determination of Sc(III) and Y(III) in river water.     

Experimental design in the optimization of a microwave acid digestion procedure for the determination of metals in biomorphic ceramic samples by inductively coupled plasma mass spectrometry and atomic absorption spectrometry

In the present paper, we have synthesized a biomorphic ceramic material from oak wood as biological template structure and infiltration with zirconia-sol. After the material characterization, we have optimized the sample dissolution by acid attack in an oven under microwave irradiation. Experimental designs were used as a multivariate strategy for the effect's evaluation of varying several variables. This article describes the development by response surface methodology (RSM) of a procedure for zirconium determination, and other ions, such as copper and nickel by inductively coupled plasma mass spectrometry (ICP-MS) and others, such as iron, calcium and magnesium determination by flame atomic absorption spectrometry (FAAS) in the synthesized sample after digestion. A full factorial design (3³) was used to find optimal conditions for the procedure through response surface study. Three variables (time, HNO₃ volume and HF volume) were regarded as factors and as response to the concentration of different metal ions in the optimization study.     

Determination of the stoichiometry and the Yb2+/Yb3+ ratio in YbF x optical IAD films by RBS and in situ XPS analysis

Thin films of YbF₃ are interesting as a possible component in antireflection coatings matching the CO₂ laser radiation. Ion assisted deposition (IAD) techniques for producing high density films were applied to this material and proved to be most successful in optimising the figures of merit for this purpose (low absorption values, high damage thresholds). Our XPS and RBS measurements, however, reveal a deficiency of fluorine in these IAD films that becomes more pronounced with increasing ion bombardment. The deficiency correlates with an increasing Yb²⁺/Yb³⁺ ratio determined by XPS. It can be concluded that the fluorine deficiency is well compensated by a valence state transition of the Yb ion and the formation of a corresponding amount of YbF₂ in the film. This process appears to be essential for avoiding metallic precipitation and achieving good optical film properties. By applying an in situ XPS technique, results have been obtained that are representative for the bulk of the films as has been confirmed by RBS.Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday