Determination of Benzo(a)Pyrene and other Polynuclear Aromatic Hydrocarbons in Airborne Particulate Material by Ultrasonic Extraction and Reverse Phase High Pressure Liquid Chromatography

Abstract

Ultrasonic extraction of airborne particulate material on Hi-Vol filters is described. Almost all of the polar compounds are removed during the extraction by adsorption on the surface of the shredded glass fibers and controlled pore glass powder (CPG). The non-polar polynuclear aromatic hydrocarbons (PAH) in the extract are separated at room temperature by high pressure liquid chromatography (HPLC) on reverse phase Vydac using acetonitrile:water (70:30 v/v) as the chromatographic solvent. There is baseline separation of benzo(a)pyrene (BaP), benzo(k)fluoranthene (BkFt) and of benzo(e)pyrene (BeP), benzo(b)fluoranthene and perylene, the latter three present in one band. Extracts of airborne particulates show the same peaks. BaP elutes in approximately 14 minutes. Precision and accuracy measurements indicate full recovery of PAH and good extraction reproducibility. The detection limit of BaP at F 290/389 is less than 10 pg. Total analysis time is approximately 1 1/2 hr, most of which is waiting time.     

Increased Flexibility in Multicolumn Chromatography (MC[sbnd]HPLC) via On-line Effluent Mixing Technique

Abstract

In continuation of our work dealing with multicolumn HPLC (MC[sbnd]HPLC) we describe in this paper an on-line on-column fraction trapping technique based on effluent mixing.

To a normal two-column switching set-up (in this case with two RP columns) an additional high-pressure pump gets inserted into the connection line between column A and column B via a low dead volume mixing tee. The in-line respectively off-line switching of pump B and the mobile phase B is time controlled by using a high pressure switching valve. With this set-up it is possible to mix on-line an effluent fraction from column A and transferred onto column B with a highly polar and pH-controlled (e.g. aqueous buffer) new effluent, to reduce or adjust significantly the overall elution strength of this mixed transferred solvent. Thus, several chromatographically effective possibilities can be created in a simple manner, which are for example: (a) pronounced peak compression respectively on-column concentration on column B; (b) due to low elution strength and/or pH adjustment during the trapping period on column B, increments to the overall selectivity of the column switching set-up can be added creating multidimensionality via mobile phase switching; (c) combining the heart cut with the effluent mixing technique enables analysis of trace peaks eluted on the back flank of an overloaded main peak.     

The Use of Decanol for Improving Chromatographic Stability in Isocratic Non-Aqueous Reversedphase Analysis of Carotenoids by High-Pressure Liquid Chromatography

Abstract

A non-aqueous isocratic solvent system for reversed-phase analysis of a full range of carotenoids from polar to non-polar is described. The major advance in the method is the use of n-decanol added at 0.1% by volume as modifier to a mobile phase of ethyl acetate-acetonitrile. The presence of the modifier rapidly conditions new columns and avoids problems with trace solvent impurities, both of which would otherwise give unsatisfactory chromatographic behaviour. In the absence of n-decanol, activation of residual silanol groups in the reversed-phase packing can cause a drastic deterioration in column behaviour. The method is rapid, versatile and simple. Information on separation conditions, solvent effects, column conditioning and carotenoid response curves is given.     

Solvent Influence on the Transformation of Intramolecular Hydrogen Bonds in 2-Hydroxy-5-Methyl-3-Nitroacetophenone

DFT (B3LYP/6-31+G(d,p)) calculations performed on 2-hydroxy-5-methyl-3-nitroacetophenone (I) indicate that the isomer with the intramolecular hydrogen bond (IMHB) to the nitro group (Ia) is more stable by 7.3 kJ-mol⁻¹ than that with the H-bond to the acetyl group (Ib). The calculated polarities of both isomers are quite different with the dipole moment of Ib being five times higher. Dipole moment and infrared studies of the Ia ⇌ Ib conformational equilibrium in different solvents show that the IMHB transformation is controlled by the solvent polarity. In polar dichloromethane and acetonitrile the Ia ⇌ Ib equilibrium is strongly shifted towards the polar Ib isomer. The simple continuum dielectric model for a heterogeneous medium and polarizable solute allows a quantitative explanation of the influence of the solvent on the Ia ⇌ Ib equilibrium.     

Studies of the Photochemical Degradation Kinetics of BaP on Different Substrates: Formation of Oxygenated Compounds

Abstract

The rate constant for BaP decomposition induced by exposure to UV rays and rate constants for BaP1,6; 3,6; 6,12 diones formation were determined. Experiments were conducted by depositing the BaP on clean glass fiber-filter and on airborne paniculate collected by filter. The BaP half-life appears to be positively correlated with filter loading and airborne particulates protect BaP from UV degradation. Our results suggest that BaP1,6dione, BaP3,6dione, BaP6,12dione are not the main by-products of BaP photodegradation induced by UV.     

Analysis of Thyroidal Amino Acids in Pharmaceutical Preparations. I - Reverse Phase High Pressure Liquid Chromatography Analysis of Sodium Liothyronine from Tablets

Abstract

A simple, sensitive and specific assay method was developed for the assay of sodium liothyronine (T₃Na) from tablets. Sodium liothyrorn'ne was extracted from powdered tablets with a solvent system consisting of butanol and dilute hydrochloric acid. The solvent was removed under vacuum and the residue was dissolved in ammonical methanol. An aliquot of this solution was injected on a μBondapak C₁₈ column and the elution was carried out with a mobile phase consisting of methanol:water:phosphoric acid (55:45: 0.1). The effluent was monitored by U. V. detection at 254 nm. A linear calibration curve was obtained in the range of 10 to 250 ng on column with a precision of ±4% (C. V.). The internal standard consisted of 3, 3′, 5-triiodothyronine (T3′ or RT₃). The usefulness of an alternate compound, 3, 5-diiodo-3′, 5′-dibromothyronine, which is not endogenous, was also demonstrated as an internal standard.     

Studies on fluorescent species of spiro-indolinonaphthooxazines and their fluorescence spectra

Photophysical behavior of spiro[1,3,3-trimethylindolino-2,3′-naphtho[2,1-b]-1,4-oxazine] (SP1) and spiro[1,3,3,2′-tetramethylindolino-2,3′-naphtho[2,1-b]-1,4-oxazine] (SP2) were studied. The fluorescent species and their spectra of SP1 and SP2 in polar solvents (acetonitrile and methanol) and non-polar solvent (cyclohexane) were investigated. The fluorescence decay in polar solvents was studied by picosecond time-correlated single photon counting. In most cases, fluorescence decay obeyed triexponential decay kinetics. The major fluorescent species is an excited intermediate which has similar conformation as its precursor (¹ SP ^*) formed after the bond cleavage between spirocarbon and oxygen in oxazine ring. The effects of molecular structure and solvent polarity on fluorescence spectra and fluorescence decay lifetime were studied.     

High Pressure Liquid Chromatographic Determination of Mecillinam in Human Plasma and Urine

Abstract

A simple, specific, rapid and sensitive method for the analysis of mecillinam in plasma and urine using high pressure liquid chromatography is described. The assay is performed by direct injection of a plasma protein free supernatant or a dilution of urine. A μBondapak phenyl column with an eluting solvent of 16% CH₃CN-0.2% H₃PO₄ was used, with UV detection of the effluent at 220 nm. Desacetyl-cephalothin was used as the internal standard and quantitation was based on peak height ratio of mecillinam to that of the internal standard. The lowest concentration detectable without extraction was 0.25 μg/ml for plasma and 8.9 μg/ml for urine. No interference from plasma and urine was noted.     

Influence of Solvent Polarity on Elution Volume in the Case of Polar Polymers

Abstract

The influence of solvent polarity on elution volume has been studied in the case of polar polymers such as homopoly-2-vinylpyridine and polystyrene-poly-2-vinylpyridine block or graft copolymers eluted on crosslinked polystyrene gels in tetrahydrofuran or dimethylformamide medium.     

Highly sensitive and selective fluorescence optosensor to detect and quantify benzo[a]pyrene in water samples

We describe here a method for detecting and quantifying the highly carcinogenic polycyclic aromatic hydrocarbon (PAH) benzo[a]pyrene (BaP) in water, based on a flow-trough optical sensor. The technique is fast (response time of 40 s) and simple and at the same time meets the standards of sensitivity and selectivity required by the European Guidelines on Water for Human Consumption. The optosensor is based on the on-line immobilization of BaP on a non-ionic resin (Amberlite XAD-4) solid support in a continuous-flow system. BaP was analyzed in a 15 mM H₂PO₄⁻/HPO₄²⁻ buffer solution with 25% (v/v) 1,4-dioxane at pH 7. Fluorescence intensity was measured at λ_ex/em=392/406 nm. The experimental conditions (reagent phase, pH, type and concentration of buffer solution and organic solvent) and flow-injection values (flow rate and injection volume) were carefully controlled. Under these conditions the optosensor was sensitive to a linear concentration range of between 3.0 and 250.0 ng l⁻¹ with a detection limit of 3.0 ng l⁻¹ and a standard deviation of 1.5% at 150 ng l⁻¹. The optosensor was applied to the quantification of BaP in drinking and waste water samples (95-105% recovery) in presence of the other 15 EPA PAHs at 1000 ng l⁻¹ concentration level. The influence of other fluorescent polycyclic aromatic hydrocarbons and potential interference from ions usually present in water was also evaluated.     

Chromatographic Purification and Identification of Polar Metabolites of Benazolin-Ethyl from Soybean

Abstract

The metabolism of benazolin-ethyl (4-chloro-2-oxobenzothiazolin-3-ylacetic acid ethyl ester), a post emergence herbicide, has been studied in soybean using (¹⁴C)-phenyl labelled compound. Preliminary studies were performed on excised soybean leaves. Following hydrolysis of the ethyl ester to benazolin acid (4-chloro-2-oxobenzothiazolin-3-ylacetic acid), extensive metabolism to polar conjugates was observed. The polar fraction from a Bligh-Dyer extraction was purified by solvent partitioning, preparative TLC and reverse phase HPLC with ion suppression. The two major metabolites were characterised by fast atom bombardment mass spectrometry with accurate mass determination as an aspartate conjugate and a malonyl-β-glucose ester of benazolin acid. Subsequent experiments were performed by spraying intact plants at growth stage V4. The major polar metabolite isolated one month after treatment was identified as the aspartate conjugate by mass spectrometry and high resolution nuclear magnetic resonance spectroscopy.     

Picosecond solvation of electronically excited solutes in alcoholic solvents: non-debye behaviour of the time-dependent fluorescence shift related to h

Time-dependent fluorescence shifts (TDFS) of polar compounds in a series of alcoholic solvents have been studied on a pico-second time scale. A non-exponential TDFS kinetic behaviour is observed, particularly at short times (0<t< 50 ps). It cannot be represented by a sum of decreasing exponentials. The effects of solute-solvent interactions on the kinetics of TDFS have been analysed. It is shown that the non-standard kinetics is due to hydrogen bonding in the solvent, particularly to the presence of alcoholic hydrogen-bonded aggregates. Following electronic excitation of the polar solute reorganization of solvent aggregates controls the TDFS time development. Our results show that a simple Debye model is inadequate to explain such a process.     

Rapid Purification of Synthetic Bombesin by Countercurrent Chromatography on the Multi-Layer Coil Planet Centrifuge

Abstract

A temperature-controlled multi-layer coil planet centrifuge rapidly yields highly efficient preparative separations of polar compounds. Capability of the method was demonstrated on a one-step purification of crude synthetic bombesin with a two-phase solvent system composed of n-butanol/dichloroacetic acid/water (100:1:100). Under an elevated temperature at 45°C to 50°C, the bombesin peak was eluted within two hours. Reversed phase HPLC analysis of the bombesin fractions showed over 98% purity. The method may be applicable to many other peptides and polar compounds.     

Solvent and Zn2+ Binding Effects on the Photo-physical Properties of (Dibenzoylmethanato)boron Difluoride

Absorption and emission spectroscopic studies of (dibenzoylmethanato)boron difluoride (1bf) in various polar and non-polar, protic and aprotic solvents are reported. The solvatochromic shifts of the spectral bands were examined in terms of solvent properties, including donor and acceptor numbers, followed by multilinear regression in which several solvent parameters were simultaneously analyzed. This π-conjugated positively charged system exhibits excellent solvatochromism. Variations in the electronic absorption spectral characteristics of 1bf were studied in solution in the presence of zinc perchlorate. Absorption spectral studies indicate stable complex formation between the zinc ion and 1bf in the ground state in aprotic dipolar benzonitrile rather than in protic polar solvent methanol. Zinc ion binding of 1bf was theoretically rationalized through frontier molecular orbital interaction.     

Separation and Quantitation of Urinary Phthalates by HPLC

Abstract

A method was developed for the separation and quantitation of plasticizers and their metabolites from human urine using HPLC, Urine was diluted with an equal volume of water and extracted at pH 2.0 with diethyl ether, The extract was dried, the solvent vacuum stripped, and the residue dissolved in methanol for injection into the chromatograph. A C₁₈ reverse phase column containing 10 μ particles was used for the analysis. Ionic suppression, 0.5% acetic acid in water, at pH 3.0 was used to resolve the acidic components. A step gradient of acetonitri1e:water (containing acetic acid) was used to elute the polar metabolites as well as the non-polar plasticizers. Mass spectrometry was used t o identify the compounds in the HPLC fractions. From the HPLC fractions of the urine extract collected, phthalic acid, MEHP, DEHP and normal urinary constituents (e.g., hippuric and benzoic acid derivatives) were identified     

Isolation of Stable Mutagenic Photodecomposition Products of Benzo(a)pyrene by Thin-Layer Chromatography

Abstract

Polycyclic aromatic hydrocarbons (PAH) are widespread in the atmosphere, the soil, waterways and oceans, as well as in the food chain. Major sources of PAH include emissions from transportation systems, heat and power generating plants, refuse burning and industrial processes (1,2,3). A significant number of these PAH are known to be carcinogenic (2,4,5). Epidemiological studies indicate that the environment is a significant factor in the incidence of human cancer, although many of the specific causal agents remain to be identified. One widely studied PAH i s benzo(a)pyrene (BaP), which is a carcinogen, and one of the most common PAH contaminants of the environment (6). Occupational exposure t o BaP has been documented (4). Mailath and Morik (7) studied the effect of sunlight and dark-room storage on BaP and reported that six and eight compounds, respectively, were observed when BaP was exposed to sunlight or left in the dark. There have been several reports of the degradation of BaP adsorbed on soot or smoke particles (8,9,10).     

Studies on the Kinetics of Polymerization of Styrene Initiated by Arsenic Trichloride

Abstract

The cationic polymerization of styrene initiated by arsenic trichloride (AsCl₃) in the presence of traces of acetic acid (co-catalyst) at -8, -4, and 0°C for 100 min using the dilatometric technique in an inert atmosphere yielded low molecular weight polymer. The rate of polymerization (R_p) is a direct function of the concentration of AsCl₃, monomer, and polar solvent, but inversely proportional to the polymerization temperature and nonpolar solvent. Hydroquinone has no effect on R_p Various kinetic parameters have been evaluated and a kinetic scheme is proposed.     

Novel Surface-Enhanced Fluorescence D Etection of Polynuclear Aromatic Hydrocarbons Separated by Paper Chromatography

Abstract

Amorphous famed silica was used to enhance the fluorescence signal of a mixture of polynuclear aromatic (PMA) compounds separated by paper chromatography. Benzo[a]pyrene-r-7, t-8, 9, 10-tetrahydrotetrol (BPT) and benzo[a]pyrene (BaP) were well resolved by paper chromatography using a 50% (v/v) mixture of acetonitrile and 5 mM pH 7.0 phosphate buffer as the chromatographic solvent. A 200–400% enhancement of the fluorescence intensity was observed when fumed silica was applied to the chromatographic paper prior to separation. the results demonstrate that paper chromatography using fumed silica treated paper offers a simple, cost-effective method to improve sensitivity for fluorescence detection of PNA components in environmental samples relative to untreated paper.     

Estimation of Adsorption Layer Capacity by Sandwich Thin-Layer Chromatography

Abstract

The use of sandwich tanks with a capillary solvent delivery system permits the determination of the volume of the developing solvent in the adsorbent layer as well as the position of the solvent demixing front. Therefore, the adsorption isotherms of polar solvents from solutions in nonpolar diluents and the adsorption layer capacities can be determined in a simple manner, analogous to the column technique: Instead of determination of breakthrough volume, the solvent demixing front on the thin layer is localized by means of a series of test dyes whose spots flatten and merge on the steep solvent composition gradient. The method is illustrated for nine aliphatic ketones adsorbed from heptane and benzene solutions. The experimental results indicate different modes of adsorption from solutions in the two diluents; the surface areas corresponding to one solute molecule are also different for symmetrical dialkyl ketones and isomeric methyl-alkyl ketones.