Geology Reports⌕ Search
Home/Archive/USGS

USGS · 70014769

Isolation of nonvolatile, organic solutes from natural waters by zeotrophic distillation of water from N,N-dimethylformamide

J.A. Leenheer·P.A. Brown·E.A. Stiles
View original source ↗Export metadata ↓

Abstract

Nonvolatile, organic solutes that comprise the dissolved organic carbon (DOC) in saline waters were isolated by removal of the water by distillation from a N,N-dimethylformamideformic acid-acetonitrile mixture. Salts isolated with the DOC were removed by crystallization of sodium chloride and sodium sulfate from the solvent mixture, removal of silicic acid by acidification and precipitation, removal of boric acid by methylation and volatilization, and removal of phosphate by zinc acetate precipitation. Chemical alteration of the organic solutes was minimized during evaporative concentration steps by careful control of acid concentrations in the solvent mixture and was minimized during drying by conversion of the samples to pyridinium and sodium salts. Recoveries of various hydrophilic organic standards from aqueous salt solutions and recoveries of natural organic solutes from various water samples varied from 60 to 100%. Losses of organic solutes during the isolation procedure were nonselective and related to the number of salt- and precipitate-washing cycles in the procedure.

Explore related subjects

Analytical ChemistryArticle

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

J.A. Leenheer, P.A. Brown, E.A. Stiles. 2002-05-01. Isolation of nonvolatile, organic solutes from natural waters by zeotrophic distillation of water from N,N-dimethylformamide. https://doi.org/10.1021/ac00136a013

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related USGS reports

USGS2026

Low pH exposure alters mediator-dependent response in poly(o-phenylenediamine)-based molecularly imprinted polymer electrochemical sensors (MIP-ES)

Molecularly imprinted polymer electrochemical sensors (MIP-ES) are a promising approach for detecting less electrochemically active contaminants, such as per- and polyfluoroalkyl substances (PFAS). However, exposure of poly( o -phenylenediamine) [poly( o -PD)]-based MIP films to strongly acidic conditions can alter the polymer environment and complicate the interpretation of electron mediator based electrochemical readout. In this study, we examined how low pH exposure influences the response of the anionic perfluorooctanoic acid (PFOA) templated poly( o -PD) MIP-ES by comparing four commonly used electron mediators with different charge states: ferrocenemethanol, ferrocyanide, ferricyanide, and hexaammineruthenium(III). Apparent association constants ( K A ) and maximum PFOA-dependent current differences (Δ i max ) derived from a fractional response two-parameter Langmuir binding isotherm model, together with ratiometric comparisons of normalized current differences, showed that mediator-dependent trends changed after acidic pH exposure of the polymer. The anionic mediators, ferrocyanide and ferricyanide, exhibited the largest increases in apparent K A and Δ i max , whereas the neutral mediator, ferrocenemethanol, retained a similar apparent K A but exhibited a lower fitted response amplitude. Hexaammineruthenium(III) produced substantial variability that limited Langmuir isotherm interpretation. These results are consistent with the interpretation that changes in the protonation state of the poly( o -PD) film influence mediator access and interactions within the sensing environment, thereby biasing the mediator-based current response. Overall, this work highlights that mediator choice can strongly affect the apparent performance of poly( o -PD)-based MIP-ES after exposure to low pH and should be considered carefully when interpreting sensor response under challenging conditions.

Analytical Chemistry↗
USGS2021

Exploring the potential of electrospray-Orbitrap for stable isotope analysis using nitrate as a model

Widely used isotope ratio mass spectrometers have limited capabilities to measure metabolites, drugs, or small polyatomic ions without the loss of structural isotopic information. A new approach has recently been introduced that uses electrospray ionization Orbitrap to measure multidimensional isotope signatures of intact polar compounds. Using nitrate as a model compound, this study aims to establish performance metrics for comparisons with conventional IRMS at the natural abundance level. We present a framework on how to convert isotopolog intensities to δ values that are commonly used in the isotope geochemistry community. The quantification of seven nitrate isotopologs provides multiple pathways for obtaining the primary N and O δ values including non-mass-dependent O isotope variations, as well as opportunities to explore nonrandom isotopic distributions (i.e., clumping effects) within molecular nitrate. Using automation and the adaptation of measurement principles that are specific to isotope ratio analysis, nitrate δ15NAIR, δ18OVSMOW, and δ17OVSMOW were measured with a long-term precision of 0.4‰ or better for isotopic reference materials and purified nitrate from environmental samples. In addition, we demonstrate promising results for unpurified environmental samples in liquid form. With these new developments, this study connects the two largely disparate mass spectrometry fields of bioanalytical MS and isotope ratio MS, thus providing a route to measure new isotopic signatures in diverse organic and inorganic solutes.

Analytical Chemistry↗
USGS2016

New organic reference materials for hydrogen, carbon, and nitrogen stable isotope-ratio measurements: caffeines, n-alkanes, fatty acid methyl esters, glycines, L-valines, polyethylenes, and oils

An international project developed, quality-tested, and determined isotope−δ values of 19 new organic reference materials (RMs) for hydrogen, carbon, and nitrogen stable isotope-ratio measurements, in addition to analyzing pre-existing RMs NBS 22 (oil), IAEA-CH-7 (polyethylene foil), and IAEA-600 (caffeine). These new RMs enable users to normalize measurements of samples to isotope−δ scales. The RMs span a range of δ 2 H VSMOW-SLAP values from −210.8 to +397.0 mUr or ‰, for δ 13 C VPDB-LSVEC from −40.81 to +0.49 mUr and for δ 15 N Air from −5.21 to +61.53 mUr. Many of the new RMs are amenable to gas and liquid chromatography. The RMs include triads of isotopically contrasting caffeines, C 16 n -alkanes, n -C 20 -fatty acid methyl esters (FAMEs), glycines, and l -valines, together with polyethylene powder and string, one n -C 17 -FAME, a vacuum oil (NBS 22a) to replace NBS 22 oil, and a 2 H-enriched vacuum oil. A total of 11 laboratories from 7 countries used multiple analytical approaches and instrumentation for 2-point isotopic normalization against international primary measurement standards. The use of reference waters in silver tubes allowed direct normalization of δ 2 H values of organic materials against isotopic reference waters following the principle of identical treatment. Bayesian statistical analysis yielded the mean values reported here. New RMs are numbered from USGS61 through USGS78, in addition to NBS 22a. Because of exchangeable hydrogen, amino acid RMs currently are recommended only for carbon- and nitrogen-isotope measurements. Some amino acids contain 13 C and carbon-bound organic 2 H-enrichments at different molecular sites to provide RMs for potential site-specific isotopic analysis in future studies.

Analytical Chemistry↗