Comparaison de Differentes Methodes Analytiques Appliquees au Dosage des Hydrocarbures Dissousdans L'Eaua L'etatde Traces

Abstract

Many physical-chemical methods are employed for the evaluation of trace hydrocarbons dissolved, in underground or surface waters.

Comparison is done of three techniques chosen amongst the most commonly used in the studies conducted on water pollution caused by oil products:

infrared spectroscopy;

ultraviolet spectrofluorimetry;

gas chromatography.

To enable the application of these techniques to very low concentrations of hydrocarbon all these techniques require a concentration step.

This can be carried out, either by the liquid-liquid extraction of the hydrocarbons with the assistance of an organic solvent and in this case, the concentration ratios are poor, or by the trapping technique, where the hydrocarbon concentration is effected by adsorption on a resin, followed by desorption by a relatively small amount of an appropriate organic solvent. The water amounts so treated can be 10 to 100 larger than those treated by a liquid-liquid extraction.

A trapping system is described which has been used in an initial phase for the detection and quantitation of aromatic hydrocarbons up to C₉. The operational conditions are described for the measurement of heavier hydrocarbons (sampled water quantity and flow, desorption solvent, amount of resin).

The importance of the concentration method and of the sensitivity of the analytical techniques chosen for the definition of the detection threshold of the dissolved hydrocarbons is pointed out.

In addition to the detection level problems for certain types of hydrocarbons, the selectivity of these techniques is considered.

In conclusion, the various methods are compared amongst themselves from the point of view of their application, of the quality of the results which are obtained and of their applicability to the different real water samples polluted by hydrocarbons.     

A Reverse Phase Technique for Separating the Linearc Furano Coumarins in Celery

Abstract

A reverse phase method for separating the four linear furanocoumarins psoralen, xanthotoxin, bergapten, and isopimpinellin in celery is described. The photosensitizing compounds, psoralen, xanthotoxin, and bergapten were also quantified in celery blades and leaves. The method utilizes a phenyl-bonded HPLC column with a methanol-water solvent system. This system allows the use of a detection wavelength (225 nm) more appropriate for these linear furanocoumarins than is currently used with normal phase systems.     

Microdetermination of Bile Acids by High-Performance Liquid Chromatography Equipped with a High Sensitive Conductance Detector

Abstract

Conductimetric detection of bile acids in reversed phase high-performance liquid chromatography is described. The solvent system of the mixture of water and organic solvent containing small amount of basic salts such as ammonium carbonate is found useable by removing the cation with the cation exchange column inserted between the ODS column and the conductance detector. Thus, a few ng of tauro-and glyco-conjugated bile acids can be detected without tedious derivatization and hydrolysis.     

Determination of Airborne Nicotine by Automatic Two-Stage Thermal Desorption Gas Chromatography

Abstract

An automated two-stage thermal desorption technique has been developed for the determination of airborne nicotine. Pumped samples are collected on adsorbent tubes and analysed by capillary gas chromatography using flame ionisation detection. The preconcentration effect of the adsorbent compared to solvent trapping or solvent desorption methods permits shorter sampling times and precludes the need for a selective detector.

By use of a basic program all exposure volumes and component details are entered into a method run table and after analysis exposure levels are automatically calculated and printed in report form by the data handling system. Consequently a large throughput samples may be analysed automatically and efficiently with minimal analyst involvement or sample preparation.

The technique described was originally developed to sample airborne nicotine in workplace environments where tobacco is processed. Comparison between this technique and the standard NIOSH method for airborne nicotine is discussed.     

Quantitation of Meclizine Dihydrochloride in Serum by Reversed Phase Ion Pair High Performance Liquid Chromatography

Abstract

A specific and sensitive HPLC method has been developed for the assay of meclizine dihydrochloride in dog serum using an internal standard technique with a single step extraction. The extracts are injected into a reversed phase ion pair HPLC system using a solvent containing camphorsulfonate as paring anion. The detection limit is 5 ng/ml and the range of linearity is 5–250 ng/ml. The method has been used to quantitate meclizine dihydrochloride levels in bioavailability and pharmacokinetic studies in dogs.     

Optimization of An On-Line Precolumn Preconcentration Method for the Determination of Polycyclic Aromatic Hydrocarbons (PAHs) in Water Samples (River and Sea Water)

Abstract

A new on-line precolumn preconcentration method for the determination of EPA priority pollutants (PAHs) in river and sea water has been developed. The retention time for each PAH in the precolumn has been determined for several percentages of organic solvent (acetonitrile) in the sample. This is very important because recoveries show a great dependence on this parameter.

The proposed procedure, combined with HPLC and spectrofluorimetric detection, reaches very low detection limits (subnanograms per liter) and it has been applied to river and sea water samples with good results.     

Simple Multisample Solvent Evaporation Assembly

Abstract

The design, construction and performance of an inexpensive multisample solvent evaporator assembled from readily available parts is described. Tubes containing solvent are heated in aluminum blocks under inert gas flow from a gas-divider manifold. The efficiency and uniformity of evaporation is satisfactory, and no substantial amounts of contaminants were observed in 100-fold solvent concentrates by gas chromatography with FID, FPD, and ECD detection. The assembly provides for an easy introduction of adsorbent trapping materials in the gas stream to remove any contaminants present in the gas.     

Analysis of Trace Levels of Volatile Organic Contaminants in Municipal Drinking Water by Glass Capillary Gas Chromatography Using Simultaneous Flame Ionization and Electron Capture Detection

Abstract

A glass capillary gas chromatographic system using simultaneous flame ionization (FID) and electron capture (ECD) detection has been employed for the analysis of trace volatile organic pollutants in a municipal drinking water supply. The use of dual detectors with glass capillary columns allows resolution and detection of both halogenated and non-halogenated compounds simultaneously at less than microgram per liter (ppb) concentrations. By using diethyl ether as a solvent in preparing standard solutions of volatile organic compounds, standardization is made more accurate due to a reduction in solvent masking of early eluting peaks of interest. Additionally, ether shows promise for use in an internal standard method for quantification of VOA. These techniques were found to alleviate problems previously encountered in the analysis of purgeable organics and are described.     

Use of an Infrared Laser in a Detection System for Liquid Chromatography

Abstract

A liquid chromatography detection system based on an infrared laser has been constructed and some tentative evaluations of its performance have been made. Although restricted to use with a very few solvents (mainly halocarbons), this system should be applicable whenever chloroform or a halocarbon solvent of lower strength (polarity) can be used. Injected sample quantities as small as one microgram have been detected on elution.     

Determination of Water Soluble Vitamins in Pharmaceutical Preparations Using Liquid Chromatography

Abstract

A liquid chromatography procedure is described for the simultaneous separation of seven water soluble vitamins in pharmaceutical pteparations. The vitamins are separated on a CR bonded-phase column and eluted with a gradient solvent program. A microprocessor controlled variable wavelength ultraviolet detector is used to automatically change detection wavelength to optimize detection of each vitamin. Pharmaceutical preparations are briefly sonicated in a dimethyl sulfoxide-water mixture, centrifuged, and an aliquot injected directly onto the column.     

A Crystalline Quartz,Laser-Excited Fluorescence,Photoacoustic, and Two-Photon Photoionization Detector for HPLC

Abstract

A crystalline quartz flow cell has been developed for simultaneous fluorescence, photoacoustic effect, and two-photon photoionization detection of aromatic compounds in HPLC eluents. Excimer laser-excited three mode detection of naphthalene, 7,8-benzoflavone, N-ethylcarbazole, and anthracene in 70/30 v/v acetonitrile/water is exhibited. The flow cell is suitable for use with deoxygenated solvent systems and is orientation independent.     

Revised Method for Determination of Aspirin and Salicylic Acid in Human Plasma by High Pressure Liquid Chromatography

Abstract

The method for the analysis of aspirin and salicylic acid in human plasma has been updated to include advances in column technology, extraction procedures and absorbance detection. Aspirin and salicylic acid are extracted from acidified plasma into an organic solvent system containing internal standard. Following controlled evaporation under partial vacuum of the organic extract, the dried down-residue is reconstituted with mobile phase. Chromatography is ion suppression reverse phase on a 5 μm O.D.S. column with detection by absorbance at 237 nm and optional fluorescence. Concentration of aspirin as low as 0.20 μg/ml and salicyclic acid as low as 0.50 μg/ml can be quantitated.     

Study of the Fluorescence Enhancement of Eu-Y-DEM-Dibenzoylmethane-Ammonia System

Abstract

The fluorescence enhancement and solvent effect of Eu-dibenzoylmethane-ammonia system was studied. The fluorescence intensity of the system can be greatly increased by y³⁺. The maximum fluorescence intensity was obtained at pH 8.9 – 9.5. The fluorescence intensity is a linear function of Eu²⁺ in the range of 1.0x10^?9 M -4.0x10^?8 M. The detection limit is 1.1x10^?10 M. The optimized procedure is applied to the determination of europium in lanthanide oxide samples.     

Proton Magnetic Resonance Studies of Binary Aqueous Solvent - Dowex 50W Systems

Abstract

Pmr is used to evaluate solvent selectivity and to furnish an indication of water structure in binary aqueous solvent - ion exchange resin systems. The hydrogen form of Dowex 50W-X8 equilibrated with binary aqueous solvents exhibits pmr peaks for internal water which are shifted downfield relative to the water - ion exchanger system. The greater the mole fraction of organic solvent in the system, the greater the downfield shift.     

Photochehical Fluorimetric Determination of Primaquine in a Flowing Solvent with Application to Blood Serum

Abstract

Primaquine in a flowing solvent is photolyzed with a 200 W Xe-Hg arc lamp and the intensely fluorescent photochemical product is measured in a fluorimeter. The effect of solvent composition and pH, irradiation time, and excitation conditions are evaluated. Primaquine in blood serum is measured by introducing a sample of blood serum into the flowing stream and performing the photochemical-fluorescence measurement. The fluorescence background of blood serum was very low allowing a detection limit of less than 0.1 μg/mL. Excellent recoveries were obtained.     

Efficient Separation of Dolaproine Stereoisomers by Optimization of a Three Component Chromatographic Solvent System

Abstract

A solvent system composed of n-hexane-chloroform-acetone was selected (by TLC) for resolving a difficult to separate mixture of protected dolaproine stereoisomers. A set of points representing solvent ratios was generated by an application of statistical methods. From thin layer chromatography data semifinal solvent ratios were selected. By applying simplex optimization, the solvent ratio was found to be 32.3 : 53.4 : 14.3 respectively for the preceding solvent system.     

Electrochemical Detection of Retinoids Using Normal Phase HPLC

Abstract

Non-aqueous electrochemical (EC) detection of 13-cis-retinoic acid, all-trans retinoic, acitretin and vitamin A palmitate in non-aqueous solvents are reported.

Non-aqueous (EC) detection allows for normal-phase chromato-graphy of these compounds prior to detection. The normal phase system used a mobile phase of HEX/THF/AcOH for the separation of all four compounds. The stationary phase was either silica or PVA-sil. The lipophilic salts, t-butylammoniumtetrafluoroborate or t-butyl-ammoniumhexafluorophosphate necessary for EC detection were added post-column.

The limit of detection (LOD) for EC detection of these compounds is approximately 1 ng on column compared with an LOD by UV absorption of 2 ng on column.

The linear detection for these compounds with the EC detector was about two orders of magnitude.     

A Simple,Quick, and Precise Procedure for the Determination of Water in Organic Solvents

Abstract

A procedure for the UV/VIS-spectroscopic determination of water by the use of a solvatochromic pyridiniumphenolate betaine is given. The water content of organic solvents is calculated by a two parameter equation from λ_max of the dye. A typical, detection limit is of the order of 1 mg in 1 ml solvent for routine spectrometers. The parameters for the determination of water are given for a number of commonly used solvents.     

Analysis of Dehydroabietic Acid in Kraft Mill Effluents by High-Performance Liquid Chromatography

Abstract

A rapid high-performance liquid chromatographic method for the determination of dehydroabietic acid in kraft mill effluent is described. Selective solvent extraction of the samples with dichloromethane was performed. The samples were isocratically analysed on a Rad-Pak C18 column using 75% acetonitrile in water (0.1% acetic acid added). Detection was carried out at 220 nm and 267 nm on a variable wavelength detector with a detection limit of 0.01 mg/L.     

Simultaneous Determination of Tolbutamide and its Metabolites in Biological Fluids

Abstract

A_pH dependent solvent extraction system has been developed to separate tolbutamide and its two known metabolites formed in man. The separated components are quantitatively converted into N-butyl-2, 4-dinitroaniline and can be measured either colorimetrically, when the concentrations are greater than 10 μg/ml of biological fluid, or via gas chromatography with electron capture detection, when the concentrations are less than 10 μg/ml. Plasma concentrations and excretion rates of drug and metabolites following intravenous administration of 1.0 g tolbutamide to man is reported.