Development of new methods for the analysis of carboxylic acids and carbonyl compounds in size classified raindrops by CE for application in modelling atmospheric processes

Summary At the present time the formation processes of clouds and precipitation are not totally understood. Because cloud- and raindroplets are major sinks for chemical species in the atmosphere it is important to understand the physical and the chemical processes which occur during precipitation. The development of models is hindered by the scarcity of information about the scavenging of gases or aerosol particles by raindrops of different sizes. These processes can only be investigated by field experiments using microanalytical methods and analysing single raindrops as well as size-classified raindrop samples. Raindrops were collected according to their size by freezing them in liquid nitrogen (“Guttalgor” method). Sample volumes of the smallest raindrop sizes (radius <200μm) were usually smaller than 2 μL. The analysis of microvolumina in the size range of μL down to pL required the development of methods designed especially for this purpose. Analysis of rain samples was carried out by capillary electrophoresis. Organic acids were determined using a new electrolyte system for indirect detection. With this system it was possible to determine monocarboxylic acids (C₁−C₄) dicarboxylic acids (C₂−C₄, C₉) and inorganic anions (Cl⁻, NO₃ ⁻, SO₄ ²⁻) in the rain samples. Carbonyl compounds were analysed after derivatisation with dansylhydrazine using direct UV-detection. The system allows the identification of aliphatic carbonyl compounds (C₁−C₃, C₅) as well as benzaldehyde. It was found that carbonyl compounds and carboxylic acids showed concentration maxima at different raindrop radii. These concentration maxima are a consequence of particle scavenging. By using the results of a former experiment we concluded that the two species are located on different aerosol particle sizes. Reasons for the different particle sizes where these species are located are discussed. Presented at the 21^st ISC held in Stuttgart, Germany, 15^th–20^th September, 1996     

Determination of benzoate by paper chromatography with visualization due to its inhibitory activity in the reaction of the photosensitized autooxidation of pyrogallol A

The oxidation of 1,2,4-triacetoxybenzene (Pyrogallol A) and 3,3′,5,5′-tetramethylbenzydine by air oxygen in presence of tris-(2,2′-dipyridyl)ruthenium(II) as a photosensitizer is studied upon irradiation by visible light. The photooxidation of pyrogallol A was inhibited selectively by benzoate at pH 9–11. The rate of the reaction was not affected by other carboxylic acids but was influenced by short-chained aliphatic amines and transition metals. We developed a semiquantitative procedure for the determination of benzoate by paper chromatography. Therein, a common solution of pyrogallol A and a photosensitizer were used for the visualization followed by irradiation with an incandescent bulb. Benzoate was detected as a light spot with R _f ∼ 0.3 against a brown background. The measurement of reflectance intensity for the spot by reflectometry allowed the determination of 1 × 10⁻⁵–0.01 M benzoate within a precision of half-order of magnitude. The procedure was validated by comparison to the data of capillary electrophoresis and used to test beverages containing benzoate at levels of 10⁻⁴–10⁻³ M.     

Liquid chromatographic determination of aliphatic amines in water using solid support assisted derivatization with 9-fluorenylmethyl chloroformate

Summary A simple and sensitive method has been developed for the liquid chromatographic determination of short-chain aliphatic amines in water. Analytes are retained in solid-phase extraction (SPE) cartridges, and then derivatized by drawing an aliquot of the fluorogeneic reagent 9-fluorenylmethyl chloroformate (FMOC) through the cartridges. After a certain reaction time the derivatives formed are desorbed with acetonitrile. The collected extracts are then chromatographed on a LiChrospher 100 RP₁₈ 125 mm×4 mm i.d., 5 μm, column using an acetonitrile-water gradient. The influence of experimental conditions (SPE material, volume of sample, concentration of FMOC, time of reaction and pH) has been investigated. Optimal results have been obtained with C₁₈ SPE cartridges using a sample volume of 5.0 mL. For derivatization, 0.25 mL aliquots of 25 mM FMOC have been used, the reaction time being only 2 min. The method has been applied to the quantification of several aliphatic amines: methylamine, ethylamine, dimethylamine,n-butylamine,n-pentylamine andn-hexylamine. Under the proposed conditions the percentages of analytes retained plus derivatized were of about 54–107% compared to those obtained with direct solution derivatization. The method provided good reproducibility, linearity and accuracy within the 0.050–1.0 mg L⁻¹ concentration range. The limits of detection were in the 0.25–5.0 μg L⁻¹ range. The utility of the described approach has been tested by analysing tap water, river water and industrial waste water.     

Reactions of nucleophilic addition of primary amines to the nitrilium derivative of the <Emphasis Type="Italic">closo</Emphasis>-decaborate anion [2-B<Subscript>10</Subscript>H<Subscript>9</Subscript>(N≡CCH<Subscript>3</Subscript>)]<Superscript>−</Superscript>

Compounds (Bu₄N)[2-B₁₀H₉{NH=C(NHR)CH₃}]⁻ are obtained by reactions of the tetrabutylammonium salt of the [2-B₁₀H₉(N≡CCH₃)]⁻ anion with aliphatic and aromatic primary amines RNH₂ (R = n-C₃H₇, n-C₄H₉, cyclo-C₅H₉, C₆H₅, cyclo-C₆H₁₁, n-C₆H₁₃, C₇H₇, C₈H₈NH₂, C₆H₄NO₂, and C₁₈H₃₇) and identified by IR, ESI/MS, and NMR (¹H, ¹¹B, and ¹³C) spectroscopy. The structures of the amidine-type derivatives [2-B₁₀H₉{Z-NH=C(NH-cyclo-C₅H₉)CH₃}]⁻ and [2-B₁₀H₉{Z-NH=C(NH-C₇H₇)CH₃}]⁻ are determined by X-ray diffraction.     

Evaluation of capillary gas chromatography for the measurement of hydrocarbons by participating in an intercomparison experiment

Summary By participating in an International Hydrocarbons Intercomparison Experiment, a method for the determination of nonmethane hydrocarbons was evaluated. The method involves Tenax-TA sampling, thermal desorption and preconcentration combined with capillary gas chromatography with flame ionization detection. Sixty target compounds from C₂ to C₁₁ were separated by using a megabore capillary column with a thick film of bonded nonpolar siloxane stationary phase (5 μm, Rtx-1). The unusually thick film in the column was an advantage for resolving light hydrocarbons (C₂−C₃) at room temperature. The percent difference between the National Institute of Standards and Technology (NIST) and our laboratory in the intercomparison experiment is in the range of 0.99%–19.70%.     

Reaction of a naphthalene complex C10H8Yb(THF)2 with cyclopentadienyl-substituted alcohols and amines as a convenient synthetic route to the half-sandwich complexes of divalent ytterbium

The reactions of ytterbium naphthalene complex C₁₀H₈Yb(THF)₂ with 2-cyclopentadienylethanol, 1-cyclopentadienylpropan-2-ol, 3-cyclopentadienyl-1-butoxypropan-2-ol, and cyclopentadienyldimethylsilyl-tert-butylamine were studied. The bivalent ytterbium complexes with chelate bifunctional cyclopentadienyl ligands [(η⁵−C₅H₅)CH₂CH₂(η¹−O)]Yb(THF), [(η⁵−C₅H₅)CH₂CH₂(η¹−O)]Yb(DME). [(η⁵−C₅H₅)CH₂CH(Me)(η¹−O)]Yb(THF), [(η⁵−C₅H₅)CH₂CH(CH₂OC₄H₉)(η¹−O)]Yb(THF), and [(η⁵−C₅H₅)SiMe₂(η¹−N(Bu¹))]Yb(THF) were obtained and characterized. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 742–745, April, 2000.     

Flow-injection analysis for the determination of total inorganic carbon and total organic carbon in water using the H2O2–luminol–uranine chemiluminescent reaction

In the presence of carbonate and uranine, the chemiluminescent intensity from the reaction of luminol with hydrogen peroxide was dramatically enhanced in a basic medium. Based on this fact and coupled with the technique of flow-injection analysis, a highly sensitive method was developed for the determination of carbonate with a wide linear range. The method provided the determination of carbonate with a wide linear range of 1.0 × 10⁻¹⁰–5.0 × 10⁻⁶ mol L⁻¹ and a low detection limit (S/N = 3) of carbonate of 1.2 × 10⁻¹¹ mol L⁻¹. The average relative standard deviation for 1.0 × 10⁻⁹–9.0 × 10⁻⁷ mol L⁻¹ of carbonate was 3.7% (n = 11). Combined with the wet oxidation of potassium persulfate, the method was applied to the simultaneous determination of total inorganic carbon (TIC) and total organic carbon (TOC) in water. The linear ranges for TIC and TOC were 1.2 × 10⁻⁶–6.0 × 10⁻² mg L⁻¹ and 0.08–30 mg L⁻¹ carbon, respectively. Recoveries of 97.4–106.4% for TIC and 96.0–98.5% for TOC were obtained by adding 5 or 50 mg L⁻¹ of carbon to the water samples. The relative standard deviations (RSDs) were 2.6–4.8% for TIC and 4.6–6.6% for TOC (n = 5). The mechanism of the chemiluminescent reaction was also explored and a reasonable explanation about chemical energy transfer from luminol to uranine was proposed. Figure Chemiluminescence profiles in batch system. 1, Injection of 100 μL of K₂CO₃ into 1.0 mL luminol-1.0 mL H₂O₂ solution; 2-3 and 4-5, Injection in sequence of 100 μL of K₂CO₃ and 100 μL of uranine into 1.0 ml luminol-1.0 mL H₂O₂ solution; C_luminol = 1.0 × 10⁻⁷ mol/L, C_H2O2 = 1.0 × 10⁻⁵ mol/L, C_uranine = 1.0 × 10⁻⁵ mol/L, C_K2CO3 = 1.0 × 10⁻⁷ mol/L except for 4-5 where C_K2CO3 = 1.0 × 10⁻⁴ mol/L     

Oxidation of primary and secondary alkanols with the CeIII-LiBr-H2O2 system

Action of a novel oxidation system, Ce(NO₃)₃·6H₂O (cat.)-LiBr (cat.)-H₂O₂ (stoichiometric oxidant) on primary aliphatic C₆–C₉ alcohols gives selectively esters, whereas secondary aliphatic C₅–C₉ alcohols are converted into ketones. Selectivity of these transformations is provided by slow addition of H₂O₂ to the other reactants.     

Asymmetric synthesis of α-substituted alkylphosphonates based on symmetrical dialkyl phosphites

Chiral C₂-symmetrical dialkyl phosphites and C₃-symmetrical trialkyl phosphites, derived from (−)-borneol, (−)-menthol, and 1,2∶5,6-di-O-isopropylidene-α-d-glucofuranose, were studied as the starting reagents for the preparation of chiral organophosphorus compounds. The reactions of C₂-symmetrical dialkyl phosphites and C₃-symmetrical trialkyl phosphites with aldehydes and amines or aldehydes are accompanied by asymmetrical induction at the α-carbon atom to yield optically active α-aminoalkylphosphanates or α-hydroxyalkylphosphonates, respectively. The stereoselectivity of the reaction depends on the structure of the starting compounds and the reaction conditions. Translated fromIzvestiya Akademii, Nauk, Seriya Khimicheskaya, No. 8, pp. 1588–1593, August, 1999.     

On-line gas chromatographic analysis of light Fischer-Tropsch synthesis products

Summary A simple gas chromatographic system has been developed for the rapid on-line analysis of light Fischer-Tropsch products. This involves a single chromatography fitted with two columns, a porous-layer open-tubular column coated with KCl deactivated alumina and a packed Porapak-Q column. The capillary column separates the 16 most common C₁−C₄ hydrocarbons and permits a reasonable analysis of the hydrocarbons in the C₅−C₇ range. The packed column is used for the separation of methane, carbon monoxide, carbon dioxide, water and methanol. Retention characteristics for the analysis on the capillary column are presented. The total analysis cycle is 30 minutes.     

Kinetic and mechanism of alkene polymerization

Triphenylmethyl salts of the very weakly-coordinating borate anions [CN{B(C₆F₅)₃}₂]⁻ (1), [H₂N{(C₆F₅)₃}₂]⁻ and [M{CNB(C₆F₅)₃}₄]²⁻ (M = Ni, Pd) have been prepared in simple one-pot reactions. Mixtures of (SBI)ZrMe₂/1/AlBu ₃ ⁱ (SBI = rac-Me₂Si(Ind)₂) are 30–40 times more active in ethylene polymerizations at 60–100°C than (SBI)ZrCl₂/MAO. The quantification of anion effects on propene polymerization activity at 20°C gives the order [CN{B(C₆F₅)₃}₂]⁻ > [H₂N{(C₆F₅)₃}₂]⁻ ≈ B(C₆F₅) ₄ ⁻ ≫ [MeB(C₆F₅)₃]⁻. The highest productivities were of the order of ca. 3.0 × 10⁸ g PP (mol Zr)⁻¹ h⁻¹ [C₃H₆]⁻¹, about 1.3–1.5 times higher than with B(C₆F₅) ₄ ⁻ as the counter anion. The titanium system CGCTiMe₂/1/AlBu ₃ ⁱ gave activities that were very similar to the zirconocene catalyst. The concentration of active species [C*] as determined by quenched-flow kinetic techniques indicates typical values of around 10%, independent of the counter anion, for both the borate and MAO systems. Pulsed field-gradient spin echo and nuclear Overhauser effect NMR experiments on systems designed to be more realistic models for active species with longer polymeryl chains, (SBI)M(CH₂SiMe₃)(μ-Me)B(C₆F₅)₃ and [(SBI)MCH₂SiMe ₃ ⁺ ...B(C₆F₅) ₄ ⁻ ] (M = Zr, Hf), demonstrated the influence of bulky alkyl chains on the ion pair solution structures: while the MeB(C₆F₅)₃ compound exists as a simple inner-sphere ion-pair, the B(C₆F₅) ₄ ⁻ compound is an outer-sphere ion pair (OSIP), a consequence of the relegation of the anion into the second coordination sphere by the γ-agostic interaction with the alkyl ligand. The OSIP aggregates to ion hextuples (10 mM) or quadruples (2 mM). Implications for the polymerization mechanism are discussed; the process follows an associative interchange (I _a) pathway. The text was submitted by the authors in English.     

Capillary electrophoretic speciation of Cu(II) and Co(III) in the electroless copper plating baths

Summary A capillary electrophoretic method for the determination of Cu(II) and Co(III) chelates with ethylenediamine in electroless copper plating baths has been developed. The influence of carrier electrolyte parameters such as nature of counter-ion and pH were studied and discussed. The optimised separations were carried out in a fused silica capillary (57 cm × 75 μm I.D.) filled with an ethylenediamine sulfate electrolyte (20 mol L⁻¹ ethylendiamine, pH7.0 with H₂SO₄; applied voltage, +25 kV) using direct UV detection at 214 nm. The detection limits for a signalto-noise ratio of 3 and 10s hydrodynamic injection were 5×10⁻⁶ mol L⁻¹ for Cu(II) and 1×10⁻⁶ mol L⁻¹ for Co(III). The relative standard deviations of the peak areas for Cu(II) and Co(III) were found to be 1.5% and 2.4%, respectively, with five consecutive injections of standard solution containing 5×10⁻⁵ mol L⁻¹ of each metal ion. Application of the method to the speciation of Cu(II) and Co(III) complexes in copper plating bath samples is also demonstrated.     

Rearrangements of cyclopentadienyl cyanates,isocyanates and their thio-,seleno-, and telluro-analogs

Dynamic NMR spectroscopy revealed that pentaphenylcyclopentadienyl isoselenocyanate undergoes reversible hetero-Cope rearrangement (ΔG ^≠ _{408 K} ∼ 22 kcal mol⁻¹, C₆D₅CD₃) giving isomeric selenocyanate in which 1,5-sigmatropic shifts of the SeCN group along the perimeter of the cyclopentadiene ring occur (ΔG ^≠ _{298 K} = 16.7 kcal mol⁻¹, C₆D₅CD₃). On the contrary, pentaphenylcyclopentadienyl iso(thio)cyanates Ph₅C₅NCO and Ph₅C₅NCS are structurally rigid compounds on the NMR time scale. The energy barrier to the 3,3-shift of the isoselenocyanate group in pentaphenylcyclopentadienyl derivative Ph₅C₅NCSe (ΔG _{298 K} ^≠ = 17.9 kcal mol⁻¹) caclulated using the B3LYP/6-31G** method is 7.6 kcal mol⁻¹ lower than for the unsubstituted analog H₅C₅NCSe.     

Simultaneous determination of cocaethylene and cocaine in blood by gas chromatography with surface ionization detection

Summary Cocaethylene together with cocaine spiked in human whole blood has been found measurable at high sensitivities by capillary gas chromatography with surface ionization detection. The drugs could be rapidly extracted by Sep-Pak C₁₈ cartridges with recovery of more than 60%. The calibration curves for both cocaethylene and cocaine using cocapropylene as internal standard were linear in the range 50–300 pmol mL⁻¹ of whole blood. The detection limits of cocaethylene and cocaine were 5–10 pmol mL⁻¹ (0.1–0.2 pmol on column if recovery is 100%). Cocaethylene could be determined for whole blood obtained from rats (ca. 200 g body wt.), which had received subcutaneous injection of 10 mg cocaine hydrochloride and 2.0 mL of 30% (v/v) ethanol 3 h before sampling; the mean levels of cocaethylene and cocaine were 101 and 1230 pmol mL⁻¹, respectively.     

Sensitive and selective determination of mercury by differential pulse stripping voltammetry after accumulation of mercury vapour on a gold plated graphite electrode

A selective and sensitive method is proposed for the determination of mercury by anodic stripping voltammetry after its preconcentration from the gas phase. Mercury from the sample solution is reduced to elemental Hg by SnCl₂ and volatilized by the bubbles of a carrier gas. The gas containing mercury vapour is dried and passed through a capillary onto a gold coated graphite electrode. An anodic stripping voltam-mogram is recorded from 0.1 mol/1 HClO₄ + 3 × 10⁻³ mol/1 HCl solution. The calibration curve is linear from 1 × 10⁻⁹ to 4 × 10⁻⁸ mol/1 Hg(NO₃)₂. The absolute detection limit is 0.46 ng Hg. The relative standard deviations for 4 × 10⁻⁹ mol/1 and 2 × 10⁻⁸ mol/1 Hg(NO₃)₂ are 9.8% and 6.1%, respectively n = 5).     

Reduction of bis[(2-phosphinoethyl)tetramethyl-cyclopentadienyl]zirconium dichlorides: intramolecular C-H activation <Emphasis Type="Italic">vs.</Emphasis> stabilization of the low-valence metal center

Reduction of the R₂P-functionalized zirconocene dichlorides [C₅Me₄(CH₂)₂PR₂] (C₅Me₅)ZrCl₂ (R = Me (1) and Ph (2)) and [C₅Me₄(CH₂)₂PMe₂][C₅Me₄(CH₂)₂PR₂]ZrCl₂ (R = Me (3) and Ph (4)) with amalgamated magnesium was studied. In the reduction of compounds 1 and 2, intramolecular C-H activation highly selectively afforded the fulvene hydride complexes Zr(H)(η⁵−C₅Me₅)[η⁵:η²(C,P)−(CH₂)C₅Me₃CH₂CH₂PR₂] (R = Me (7), Ph (8)); in the case of compound 2, the aryl hydride Zr(H)(η₅:C₅Me₅)[η⁵:η¹(C)−C₅Me₄CH₂CH₂PPh(o−C₆H₄)] (9) was also formed. The reduction of complexes 3 and 4 gave the Zr^II derivatives Zr[η⁵:η¹(P)− C₅Me₄CH₂CH₂PMe₂]₂ (12) and Zr[η⁵:η₁(P)−C₅Me₄CH₂CH₂PMe₂][η⁵:η¹(P)−C₅Me₄CH₂ CH₂PPh₂] (14) stabilized by two phosphine groups. The second product in the reduction of compound 4 was the fulvene hydride complex Zr(H)(η⁵−C₅Me₄CH₂CH₂PPh₂)[η⁵:η²(C,P)−(CH₂)C₅Me₃CH₂CH₂PMe₂] (15). The reaction of compound 7 with an excess of MeI resulted selectively in replacement of the hydride ligand by iodide to give the complex ZrI(η⁵−C₅Me₅)[η⁵:η²(C,P)−(CH₂)C₅Me₃CH₂CH₂PMe₂] (10). In contrast, in the reaction of compound 7 with Me₂Si(H)Cl, the Zr-CH₂ bond underwent cleavage to give the chloride hydride complex Zr(H)Cl(η₅−C₅Me₅)[η⁵:η¹(P)−C₅Me₃(CH₂SiMe₂H)CH₂CH₂PMe₂] (11). In the reaction of complex 12 with CO, a phosphine group was replaced by CO to form the complex Zr(CO)(η5−C₅Me₄CH₂CH₂PMe₂)[η⁵:η¹(P)−C₅Me₄CH₂CH₂PMe₂] (13). The results obtained were compared with analogous reduction reactions of MeO-, MeS-, and Me₂N-functionalized zirconocene dichlorides. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 65–74, January, 2008.     

Determination of heterocyclic aromatic amines (HAA) in commercially available meat products and fish by high performance liquid chromatography—Electrospray tandem mass spectrometry (HPLC-ESI-MS-MS)

Summary Ten heterocyclic aromatic amines (HAA) (1)–(10) were analyzed in commercially available meat products and fish. After sample preparation by Extrelut treatment and subsequent solid phase extraction applying propylsulphonic and C₁₈ silica cartridges, HPLC-ESI-MS-MS using selected reaction monitoring (SRM) and d₃-PhIP and d₃-MeIQx as internal and external standards, respectively, revealed the widely distributed presence of PhIP (8) and MeIQx (4), ranging from 0.1 to 5.3 ng g⁻¹ and 0.1 to 5.2 ng g⁻¹, respectively. Lower amounts were found for 4,8-DiMeIQx (5) and 7,8-DiMeIQx (6), ranging from 0.2 to 2.0 ng g⁻¹ and 0.1 to 0.2 ng g⁻¹, respectively. The other HAA under study, i.e. IQ, MeIQ, 4,7,8-TriMeIQx, Glu-P-1, and Glu-P-2 were not determinable under the experimental conditions used (determination limit 0.1 ng g⁻¹).     

Improved HPLC determination of aliphatic amines in air by diffusion and derivatization techniques

Summary Traces of C₁–C₄ aliphatic amines, sampled from ambient air on H₃PO₃-coated annular denuders, are derivatized with m-toluoyl chloride (MTC) in alkaline acetonitrile. The resulting derivatives are determined by reversed phase HPLC with ultraviolet detection at 230 nm. The detection limits of the individual amines are in the 1 to 5 picomole range corresponding to gasphase concentrations lower than 0.1 g m^–3 in air samples collected at 5 Lmin^–1 for one hour.     

Synthesis, characterization and standard molar enthalpy of formation of Nd(C7H5O3)2·(C9H6NO)

The complex from reaction of neodymium chloride six-hydrate with salicylic acid and 8-hydroxyquinoline, Nd(C₇H₅O₃)₂·(C₉H₆NO), was synthesized and characterized by IR, elemental analysis, molar conductance, and thermogravimatric analysis. The standard molar enthalpies of solution of [NdCl₃·6H₂O(s)], [2C₇H₆O₃(s)], [C₉H₇NO(s)] and [Nd(C₇H₅O₃)₂·(C₉H₆NO)(s)] in a mixed solvent of anhydrous ethanol, dimethyl formamide (DMF) and perchloric acid were determined by calorimetry at 298.15 K. Based on Hess’ law, a new chemical cycle was designed, and the enthalpy change of the reaction