Stefan A. Huber

Characterisation of aquatic humic and non-humic matter with size-exclusion chromatography – organic carbon detection – organic nitrogen detection (LC-OCD-OND)

Size-exclusion chromatography in combination with organic carbon detection (SEC-OCD) is an established method to separate the pool of NOM into major fractions of different sizes and chemical functions and to quantify these on the basis of organic carbon. One specific approach, also known as LC-OCD-OND, is based on the Gräntzel thin-film UV-reactor. This approach is described with recent improvements in fraction assignation (humic substances, biopolymers, building blocks, low molecular weight organic acids and neutrals, hydrophobic organic carbon), the coupling of a novel organic nitrogen detector (OND), and an improved diagram for the characterisation of aquatic humic substances (HS-diagram). The diagram replaces the operational distinction between humic and fulvic acids by a continuum ranging from aquagenic fulvic acids to pedogenic humic acids.

Direct Gel Chromatographic Characterization and Quantification of Marine Dissolved Organic Carbon Using High-Sensitivity DOC Detection.

A special issue of Marine Chemistry on the analysis of dissolved organically bound carbon (DOC) and dissolved organically bound nitrogen (DON) in seawater (1) has motivated us to apply a high-sensitivity gel filtration liquid chromatographic system with continuous DOC detection for the characterization and quantification of DOC in seawater. The advantages of on-line chromatographic DOC detection are obvious: analysis of organic matter is virtually carried out matrix-free because the gel filtration mechanism separates the inorganic salts from the organic matter to a large extent. Interferences occur only for that small organic fraction that coelutes with the inorganic salts. The different organic fractions reflect groups of compounds with distinct chemical properties. This can be used for the characterization of organic matter. The system allows the direct chromatographic analysis of organic matter in 1 mL of seawater without pretreatment. In 1983, an older design of the DOC detector-but without chromatographic fractionation-was used for the direct analysis of seawater DOC (2).

A liquid chromatographic system with multi-detection for the direct analysis of hydrophilic organic compounds in natural waters

SummaryA combined analytical LC/HPLC system was developed which allows the direct and continuous determination of organic carbon (OC), inorganic carbon (IC), UV-Vis, fluorescence, and organically bound nitrogen in aqueous solutions in the low μg/l concentration range. The arrangement is well suited as detector for the direct chromatographic characterisation of organic constituents in natural surface- and groundwaters without any sample pretreatment.

A New Method for the Characterization of Organic Carbon in Aquatic Systems

Abstract Some problems in organic carbon characterization are briefly discussed. A new chromatographic multi-method for the direct characterization of organic matter in original waters with the simultaneous determination of UV-Vis, fluorescence, DOC, TIC, and organically bound nitrogen (DON) is described. Some applications with UV-Vis and DOC (“CODOC”) detection are presented.

Identification of diffuse and point sources of dissolved organic carbon (DOC) in a small stream (Alb, Southwest Germany), using gel filtration chromatography with high-sensitivity DOC-detection

Using gel filtration chromatography and high-sensitivity UV and organic carbon (OC) detection, the quality and quantity of organic matter in a stream (the Alb, Southern Germany) has been studied in the winter season. In the catchment area and upstream of two sewage plant effluents the organic load has been low (below 1 mg/l TOC) and has been dominated by humic substances (more than 80%). Downstream of the sewage plants, TOC increased up to 5 mg/l while humic constituents decreased down to 30%. A detailed analysis showed that in the catchment area the humic fraction has been composed of fulvic acids with relatively high amounts of aliphatic structures. Downstream of the sewage plants, the humic fraction has been composed of fulvic acid precursors with associated non-humic matter. It is concluded that the quality and quantity of organic constituents in the stream has been dominated by the secondary effluents.

Liquid chromatographic characterization of refractory organic acids

Abstract Liquid chromatography (LC) in the high and medium pressure mode in association with sensitive detection systems [UV-vis, diode array detector (DAD), fluorescence, dissolved organic carbon (DOC)] is used for the characterization of dissolved organic matter in aqueous samples. Even though the chromatographic mechanisms for the fractionation of humic-type organic substances are not fully known, the use of different columns (gel, C-18 phases, etc.) adds significantly to the understanding of the functionality of the organics. The chromatograms show that there are larger differences between the isolated fulvic acids (FAs) and the organics in unaltered water samples than between FAs from different origin but isolated using the same method. The influence of the isolation procedure is demonstrated on soil extracts. For the first time an on-line DOC detection system is used to trace the liquid chromatogram of a tap water sample.

The Role of Organic Matter in Natural Aquatic Systems: Analytical Constraints

Abstract The dissolved organic matter in aquatic systems consists of a heterogeneous mixture of compounds with wide ranging chemical properties and diverse origins. the presence of organic matter (OM) in surface and ground waters has important implications with regard to the mobility and therefore fate of many potential organic and inorganic pollutants. the majority of the analytical approaches in current use require exhaustive pre-treatment steps which may lead to the formation of artefacts within the sample. an analytical technique based upon gel permeation chromatography is proposed as a more reliable procedure for the characterisation of naturally occurring dissolved organic matter.