Acquisition and Analysis of Groundwater/Aquifer Samples: Current Technology and the Trade Off Between Quality Assurance and Practical Considerations

Abstract

As part of its mission to protect groundwater quality, the U.S. Environmental Protection Agency regulates the land disposal of solid wastes. Mathematical models such as MINTEQAI, a thermodynamic equilibrium model for metal speciation, are used to predict the concentrations of harmful pollutant species at potential exposure points, and thus determine the requirements for waste treatment and disposal. The Environmental Research Laboratory, Athens, GA, is engaged in a bench-scale testing project for the attenuation processes currently in MINTEQAI.

In the migration of a high organic carbon content landfill leachate through the subsurface environment, the mobility of inorganic contaminants can be seriously influenced by oxidation-reduction, complexation, precipitation and adsorption processes. These processes in turn depend on the dissolved major (and minor) element composition, dissolved gas content, degree of equilibrium and the nature of the aquifer surfaces exposed to groundwater. ERL-Athens has been collecting groundwater, acquifer material and municipal landfill leachate samples from various locations within the continental United States. These samples have been characterized in terms of elemental composition, pH, Eh, dissolved gases and solid phase analyses (Specific Surface Area, CEC, extractable amorphous components, identifiable crystalline components, etc.). Batch distribution behavior studies have been performed with these samples with 14 potential metals and metalloids of concern to the EPA. Of more interest to the analytical chemist, however, are the manifold sampling, analytical and interpretative problems encountered: (1) What are the major sources of error in terms of the necessary expertise and equipment for sample acquisition? (2) Can samples be collected in an unperturbed manner and what is the best way to collect them? (3) How meaningful are field pH, Eh, dissolved oxygen, and alkalinitiy measurements? How stable are these values? (4) Are current commonly available experimental procedures sufficient for modeling attenuation processes? These and other problems persisting at the state-of-the-art will be discussed, as well as trade-offs necessary to achieve adequate quality with reasonable cost.     

Membrane technologies for water treatment and agroindustrial sectors

Although water is essential for human survival and progress, it is distributed very unevenly and with a different purity over the surface of the earth. A variety of contaminants can be present in raw water, depending on its origin. The size of these contaminants ranges from the micrometer (e.g. bacteria) to the tenths of a nanometer order (ions). Membrane processes like microfiltration, ultrafiltration, nanofiltration and reverse osmosis could be a solution for an advanced physical treatment of water for drinking purposes as well as for agroindustrial sectors. Many applications are well assessed and are expanding very quickly; however, to obtain an ever-growing performance, it is necessary to prepare membranes with tailored structure and transport properties. Characterisation methods play also a role of paramount importance for the selection of the more appropriate membrane for the above-mentioned applications. In this work the main membrane preparation techniques and characterisation methods will be reviewed and discussed.     

Reactions of Dichlorothionitronium Hexafluoroarsenate(V) with Alkynes & Alkenes

Abstract

The dithionitronium cation (SNS⁺) has been shown to undergo completely general, concerted cycloadditions with a wide variety of unsaturated main-group species to give heterocyclic products in quantitative yields. The isolobality of the frontier molecular orbitals of the dichlorothionitronium cation (ClSNSCl⁺) with those of SNS⁺ led us to predict that this cation would undergo concerted cycloadditions under similar conditions. This has been confirmed in its reactions with acetylene and ethylene. Dichlorothionitronium hexafluoroarsenate(V) (ClSNSCl⁺AsF₆ ^-) reacts with acetylene in liquid sulphur dioxide to produce 1,3,2-dithiazolium hexafluoroarsenate(V) quantitatively via initial cycloaddition followed by SO₂-mediated chlorine abstraction and aromatisation. Analogously, cycloaddition also occurs with ethylene, though without subsequent chlorine abstraction. This has enabled a novel 1,3-dichloro-1,3,2-dithiazolidinium salt to be isolated in quantitative yield. The characterisation of this product by a variety of spectroscopic techniques will be discussed, together with recent developments in the chemistry of this and related systems.     

Isolation of Lipophilic Persistent Organic Pollutants From Human Breast Milk

Background: Lipid removal from biological samples can be achieved by addition of concentrated sulfuric acid. However, certain persistent organic pollutants (POPs) such as chlorophenols are decomposed by sulfuric acid treatment and, thus, a more gentle lipid reduction method is needed for extraction of many environmental contaminants from biological samples. Membrane dialysis extraction (MDE) is a non-disruptive method to extract POPs from biological matrices.

Methods: Human breast milk samples were spiked with radiolabelled p,p′-dichlorodiphenyl trichloroethane ([C-14]-DDT) as a POP proxy and extracted using solid phase extraction (SPE). The extracts obtained were dialyzed by MDE in low-density polyethylene tubings containing a mixture of n-hexane and dichloromethane for 24 h, 48 h, or 72 h.

Results: The lipid content was reduced by 86.2% after one dialysis cycle of 24 h using MDE, and 87.1% recovery of the [C-14]-DDT standard was obtained. The DDT recovery could be further increased up to 96.3% and 98.1% by repeating the dialyses for one or two more cycles, respectively. However, the increased [C-14]-DDT recovery includes a concomitant increase in lipid carryover from 13.8% with one dialysis cycle to 22.1% with three cycles.

Conclusion: An SPE procedure for extracting POPs from breast milk and dialytic conditions for isolation of the extracted POP with minimal lipid carryover was established. The method is nondestructive and acceptable recoveries can be obtained within a single solvent shift as demonstrated by spiking standards. The lipid carryover was minimized, and the method may be considered for lipid removal before HPLC or GC analysis of environmental contaminants.     

Broad Spectrum Analysis of Ionic and Non-Ionic Organic Contaminants in Urban Wastewaters and Coastal Receiving Aquatic Systems

Abstract

A comprehensive analytical protocol for the qualitative and quantitative assessment of ionic and non-ionic organic contaminants in urban wastewaters, coastal seawater, and sediments is outlined. Liquid-liquid extraction (LLE) and adsorption onto polymers (polyurethane foam) or macroreticular resins (Amberlite, XAD-2) for the extraction of a wide variety of dissolved contaminants are evaluated. Organic extracts are resolved into fractions of increasing polarity by a combination of silica-alumina adsorption and gel permeation chromatography. HRGC-MS analysis of these fractions, using different ionization techniques, namely electron impact (EI), positive (PICI) and negative ion chemical (NICI) ionization, and the direct use of FAB-MS on the original extracts enabled the identification of a broad spectrum of anthropogenic compounds (290) in the different aquatic compartments. The decoupling of these contaminants between the water-dissolved and particulate phases is discussed.     

CHITIN AND CHITOSAN FOR VERSATILE APPLICATIONS

ABSTRACT

Chitin and chitosan are versatile polymers, where the interest in chitosan is due to the large variety of useful forms that are commercially available or can be made available. Chitin basically is obtained from prawn/crab shells; chemical treatment of chitin produces chitosan. This article surveys applications of chitin and chitosan in various industrial and biomedical fields.     

NEW RADIOHALOGENATED ALKENYL TELLURIUM FATTY ACIDS

Abstract

Radiolabeled long-chain fatty acids have diagnostic value as radiopharmaceutical tools in myocardial imaging. Some applications of these fatty acids are limited due to their natural metabolic degradation in vivo with subsequent washout of the radioactivity from the myocardium. The identification of structural features which will increase the myocardial residence time without decreasing the heart uptake of long-chain fatty acids is of interest. Fatty acids containing the tellurium heteroatom were the first modified fatty acids developed and show unique prolonged myocardial retention and low blood levels. Our detailed studies with radioiodinated vinyliodide substituted tellurium fatty acids demonstrate that heart uptake is a function of the tellurium position. New techniques of tellurium and organoborane chemistry have been developed for the synthesis of a variety of radioiodinated iodoalkenyl tellurium fatty acids.     

CONVENIENT SYNTHETIC METHODS FOR THE PREPARATION OF N-FLUOROALKYLHYDROXAMIC ACIDS

ABSTRACT

Polyhydroxamate chelators containing fluoro substituents are of interest as potential extractants for actinides in separations involving supercritical carbon dioxide. In this context, we have developed three new reagents 1, 2, and 3, that allow the efficient incorporation of an N-fluoroalkyl hydroxamate moiety onto a variety of substrates using acylation, alkylation, and Michael addition strategies.     

The Use of the PREPTM System for Handling of Body Fluids

Abstract

The Du Pont PREP^TM automated sample processor is a centrifugally based, microprocessor controlled instrument that was designed for extraction of samples from biological fluids. Extraction takes place in cartridges containing either organic resins or bonded silica packings as extraction sorbants. This paper will discuss the application of several lipophilic and ion exchange sorbants to the extraction of biological samples from body fluids. The advantages of these different types of sorbants will be compared and their performance with automated sample preparation will be shown. A variety of applications including the extraction of benzodiazepine, barbiturate, aminoglycoside and anticonvulsant drugs and their metabolites from serum, urine, and tissue homogenates will be discussed.     

Identification of Organic Compounds Solvent Extracted from Paper and Glass Soxhlet Thimbles

Abstract

Organic compounds leached from paper and glass soxhlet thimbles have been identified by computerized high resolution gas chromatography /mass spectrometry. Nineteen specific organics have been tentatively identified from paper thimbles. The analysis of glass thimbles have not demonstrated these contaminants. The use of glass thimbles as a substitute for paper is advantageous in preparation of samples for trace organic analysis. This is an improvement but not a panacea as cross-contamination must still be evaluated by the analytical chemist.     

Production of certified reference materials for mycotoxins: IRMM’s view on the assessment of uncertainties

Analytical difficulty and the economic importance of controlling mycotoxin levels in food and feed led the Community Bureau of Reference (BCR) to prepare a series of certified reference materials (CRM) for various mycotoxins. Because of the wide acceptance of these CRM and the need to ensure the comparability and traceability of measurements in the future it is necessary to prepare and certify new batches of mycotoxin reference materials (RM). In the following text two different approaches for evaluation of the characterisation uncertainty of CRM will be compared using the certification of aflatoxin M₁ (AfM₁) in milk powder as an example. The conventional approach is based on evaluation of characterisation exercise data; the alternative approach is based on measurement uncertainties of the employed analytical methods. Because laboratories are using totally different approaches to estimate the measurement uncertainties, combination of the uncertainties obtained from the participating laboratories was not recommended. Therefore, a new integrated approach for assessment of the measurement uncertainties of the analytical methods on the basis of additional data collected during the characterisation exercise will be described. The conventional approach was found to be the most appropriate and economical approach to evaluate the characterisation uncertainty as a characterisation exercise must be performed anyway to establish the property values of candidate (C)RM, irrespective of whether or not reliable measurement uncertainties can be provided by the laboratories. An integrated approach for assessment of measurement uncertainties based on additional characterisation data as applied here to enable use of an uncertainty-based approach provides more information but is too time-consuming and cost-intensive to become common practice.     

Co-ordination Chemistry of ButCP,Mono-and Diphospha-allenes (R1P=C=CR2 and R1P=C=PR1) and 1,3-Diphosphacyclobutadiene

Abstract

A variety of novel coordination complexes derived from phospha-alkynes, and mono- and diphospha-allenes will be described.     

Hyphenated analytical techniques for multidimensional characterisation of submicron particles: a review

The stakes concerning the characterisation of particles ranged in the size from 1 to 1000 nm, namely submicron particles, are today more and more important. Because of the variety of particles even inside a given sample in terms of dimension, mass, charge or chemical composition a characterisation as complete as possible is needed. The possibility of obtaining a multidimensional information by relevant analytical methods is then of the greatest interest. One very interesting strategy consists in using hyphenated techniques, which are intrinsically capable to provide rapidly and accurately such information. This paper summarises the different hyphenated techniques that can be used to characterise submicron particles and is focussed on their main applications to illustrate their current and potential uses. In order to have a relevant overview various on-line separation techniques are considered in a comparative way. In the same way various on-line detectors are then presented. Finally the concepts of multidetection and multidimensional analysis are discussed and their interest showed through different typical examples of hyphenated techniques illustrating submicron particle characterisation in fields of applications such as environmental and nanomaterial sciences.     

LABORATORY SYNTHESIS OF POLYETHYLENE GLYCOL DERIVATIVES

Abstract

In recent years, derivatives of polyethylene glycol (PEG) have proven valuable in a variety of diverse chemical and biological endeavors. Such applications include peptide synthesis, phase transfer catalysis, pharmaceutical modification, protein and cell purifications, polymer-bound reagents, and binding assays. Because of the great deal of interest surrounding this subject, this review will describe generally applicable laboratory methods for preparing PEG derivatives from the parent PEG. We have largely restricted discussion to this starting material because most research laboratories interested in applications are not equipped to handle complex ethylene oxide polymerizations used in large-scale industrial preparations and because PEG and some of its ethers and esters are the only commonly available polymeric starting materials. For the purpose of this review, PEG is defined as those polyoxyethylenes having hydroxyl endgroups and a molecular weight of 20,000 daltons or less.     

POLY(ASPARTIC ACID) HYDROGEL

ABSTRACT

Stimuli-responsive hydrogels have attracted much interest recently [1]. In this paper, we report a pH- and electrolyte-responsive hydrogel based on a crosslinked poly(aspartic acid). The lightly crosslinked, high molecular weight sodium polyas-partate impart extremely high water absorbency and can be used as a superabsorbent [2], It is derived from a naturally occurring non-toxic amino acid, L-aspartic acid. A hydrogel based on poly(as-partic acid) possesses most of the features of poly(acrylic acid) hydrogels plus improved biodegradability. We expect it to be useful in a variety of applications including personal care and biomedical areas.     

THE CHEMISTRY OF OPTICALLY ACTIVE SULFUR COMPOUNDS PART III

Abstract

The chemistry of optically active sulfur compounds has proven to be one of great interest and challenge as demonstrated by the prolific publications in this area. An ever larger number of different types of compounds with sulfur as center of chirality are being synthesized and it is expected that in future publications additional members of this group will be described. Thus far the following chiral sulfur compounds have been prepared:     

Synthesis of a Zn-salen resorcinarene-based cavitand and its fluorescence response to nitro compounds

The synthesis, spectroscopic characterisation, conformational switching and fluorescence quenching efficiency of a resorcinarene-based cavitand containing Zn-salen (Zn-Cav) are reported. Synthesis of Zn-Cav was accomplished by the condensation of a quinoxaline derivatised with Zn-salen and a resorcinarene-based cavitand containing three quinoxalines. ¹H NMR spectroscopy confirmed that in DMSO, chloroform and acetone Zn-Cav resides in the vase conformation. The molecular geometry of Zn-Cav selectively changes from vase to kite under acidic conditions. Detection by fluorescence quenching of nitro-containing molecules, such as 4-nitrotoluene, 2,4-dinitrotoluene and 2,3-dimethyl-2,3-dinitrobutane was explored by spectrofluorimetry. It was found that the fluorescence of Zn-Cav is efficiently quenched by nitroaromatic compounds.     

The Synthesis of Perfluorocyclohexano-15-crown-5 Ether

Perfluorocyclohexano-15-crown-5 ether, trans- (1) and cis-(2) isomers have been prepared by direct fluorination using the LaMar fluorination technique¹. They have several potential applications and are of special interest in a variety of fields².     

AN APPROACH TO DIRECT EVALUATION OF PI BONDING IN METAL CARBONYLS

Abstract

The extent of π bonding between the metal atom and the ligand atoms in metal carbonyls and substituted metal carbonyls is a matter of great interest and importance and has accordingly been the subject of a great many studies by a variety of methods. In practically all such studies an indirect approach has been taken. The properties measured are not direct manifestations of electronic structure but rather they are properties whose own basis in electronic structure cannot be unambiguously defined.     

The Chemical Characterization of Potential Organic Interferences in Two Commercially Available Polymeric Adsorbents

Abstract

Current use of synthetic adsorbents for the collection of trace organics in environmental samples is quite extensive. It has been suggested that high levels of organic contaminants in these resins may interfere with subsequent analyses, however, the identity of these suspected contaminants has not been reported.

This paper reports a qualitative and quantitative characterization of the residual organics in two polymeric adsorbents.

Both resins are commercially available polymers of styrene divinyl-benzene. The structures of the contaminants were verified by combined gas chromatography/mass spectrometry (GC/MS). High artifact levels are typical for both of the Amberite® resins studied. The majority of these materials, as verified by capillary GC/MS, were alkyl derivatives of benzene, styrene, naphthalene and biphenyl.