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Molecular formulas have been assigned for 4626 individual Suwannee River fulvic acids based on accurate mass measurements from ions generated by electrospray ionization and observed by ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS). Formula assignments were possible because of the mass accuracy of FTICR MS at high field (9.4 T) and the regular mass spacing patterns found in fulvic acid mixtures. Sorting the 4626 individually observed ions according to Kendrick mass defect and nominal mass series (z* score) revealed that all could be assigned to 1 of 266 distinct homologous series that differ in oxygen content and double bond equivalence. Tandem mass spectrometry based on infrared multiphoton dissociation identified labile fragments of fulvic acid molecules, whose chemical formulas led to plausible structures consistent with degraded lignin as a source of Suwannee River fulvic acids.

Electrospray ionization (ESI) was combined with ultrahigh-resolution Fourier transform-ion cyclotron resonance mass spectrometry (FTICR MS) to characterize complex humic and fulvic acid mixtures. Lower than expected molecular weight distributions previously observed for humics when analyzed by ESI-MS have fueled speculation about a bias in favor of low molecular weight. Multiply charged ions, ionization suppression, and sample fragmentation have all been suggested as sources of this low molecular weight bias. In this work, resolution of the individual components of humic mixtures within a 1 mass-to-charge unit window was accomplished by FTICR MS at 9.4 T. At mass resolving powers between 60 000 (high mass) and 120 000 (low mass), it was possible to determine that virtually all ions present in spectra of Suwannee River fulvic and humic acid are singly charged, thus eliminating inadequate accounting for multiply charged ions as a primary source of any low molecular weight bias. The high-resolution mass spectra also revealed the presence of molecular families containing ions that differ from each other in degree of saturation, functional group substitution (primarily CH vs N and C[H.sub.4] vs O), and number of C[H.sub.2] groups, Ionization suppression and ion fragmentation were addressed for humic and fulvic acid mixtures and well-characterized poly(ethylene glycol) (PEG) mixtures with average molecular weights of 8000 and 10 000. Although these high molecular weight PEG mixtures fragment extensively under traditional positive-ion mode ESI conditions, similar fragmentation could not be confirmed for humic and fulvic acid mixtures.

A method for the selective concentration of dissolved organic phosphorus (DOP) from complex surface water samples for the first time allows mass spectral characterization of individual DOP compounds in phosphorus-limited ecosystems. The entire dissolved organic matter (DOM) pool is first separated according to molecular weight by tangential cross-flow ultrafiltration (CFF). DOP is selectively isolated and concentrated from CFF fractions by a barium precipitation procedure. The DOP precipitate is then reconstituted in distilled water and excess barium, and other cations are removed with an ion-exchange resin. The DOP isolation/concentration step can provide up to 15-fold concentration and 300-fold concentration of high molecular weight DOP when combined with the inherent concentration provided by CFF. The procedure also removes cations and most of the background DOM, leaving DOP in a matrix suitable for electrospray ionization and mass spectral characterization. Model organic phosphate standards representative of DOP species expected in aquatic environments were used to evaluate the technique. It was then applied to a series of high molecular weight (> 1000) CFF retentates isolated from sites within the Everglades Nutrient Removal (ENR) treatment wetland. The elemental compositions of several individual DOP compounds observed at different sites within the ENR were determined by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry.

A review of published literature on liquid chromatography for the period Oct 1995 to Oct 1997 is presented. The papers covered topics on peak purity, deconvolution, solute retention, mobile-phase studies, capillary electrochromatography, support activation and affinity ligand immobilization. Papers on stationary-phase studies, ion chromatography, ion pairing, optical isomers and postcolumn derivatization were also included in the review.

A fundamental review of liquid chromatography literature addresses major changes for the time period of Oct. 1993 to Oct. 1995. Most publications are gathered from on-line CAS database with additions from personal data gathering by the reviewers. The subject matter is generally treated in Scott's Liquid Chromatography for the Analyst, Riley's Pharmaceutical and Biomedical Applications of Liquid Chromatography, and Subramanian's Process Scale Liquid Chromatography.

The inefficiency of gas chromatography techniques to handle polar and high molecular weight compounds led to the development of bonded-phase liquid chromatography. The technique, which allows higher retention of silica materials, has since then the primary method used by chemists in their manufacturing processes. However, despite the advances in these method, problems with regard to high- and low-pH conditions remain to be solved.

A review of selected literature on the chemistry of the separation process in liquid chromatography (LC), published during Dec. 1991-Dec. 1993, is presented. The review covers research and application papers involving normal-phase LC, reversed-phase LC, biopolymer separations, affinity chromatography, ion chromatography, secondary chemical equilibria, microcolumn and opentubular LC, trace analysis and preparative LC.

Many scientific papers written between Dec 1989, and Dec 1991, indicated that the application of various theoretical and procedural concepts aimed to improve the efficiency and selectivity of liquid chromatography were proven to be successful. New materials and methodologies were tested on the different types of liquid chromatography. The improvements in the technique's performance made it useful and valuable in a number of compounds and analytical experiments.

Phosphorus sequestration in wetland soils is a prerequisite for long-term maintenance of water quality in downstream aquatic systems, but can be compromised if phosphorus is released following changes in nutrient status or hydrological regimen. The association of phosphorus with relatively refractory natural organic matter (e.g., humic substances) might protect soil phosphorus from such changes. Here we used hydrofluoric acid (HF) pretreatment to remove phosphorus associated with metals or anionic sorption sites, allowing us to isolate a pool of phosphorus associated with the soil organic fraction. Solution (31)P and solid state (13)C NMR spectra for wetland soils were acquired before and after hydrofluoric acid pretreatment to assess quantitatively and qualitatively the changes in phosphorus and carbon functional groups. Organic phosphorus was largely unaffected by HF treatment in soils dominated by refractory alkyl and aromatic carbon groups, indicating association of organic phosphorus with stable, humified soil organic matter. Conversely, a considerable decrease in organic phosphorus following HF pretreatment was detected in soils where O-alkyl groups represented the major fraction of the soil carbon. These correlations suggest that HF treatment can be used as a method to distinguish phosphorus fractions that are bound to the inorganic soil components from those fractions that are stabilized by incorporation into soil organic matter., (© 2012 American Chemical Society)