Association of Humic Substances: Verification of Lambert‐Beer Law

The precision UV/Vis‐absorption spectra of a naturally occurring aquatic humic substance were measured in the range of concentration 0.003 to 1.4 g/L DOC (dissolved organic carbon). Lambert‐Beer law is well obeyed at low concentrations whereas deviations have been observed for DOC concentrations above 0.1 g/L: they are interpreted in terms of self‐solvation and formation of micelles.     

Approaches to the Immunochemical Analysis of Non-extractable Triazine Residues in Refractory Organic Substances (ROS) and Characterization of ROS

The tendency of several pesticides to form non-extractable residues requires simple and fast screening methods. Immunochemical methods can meet this demand. They are based on selective and highly sensitive antibody binding to pesticide residues exposed on refractory organic substances (ROS). s-Triazines were used as an example to show the feasibility of this approach. It was proven that under laboratory conditions atrazine was bound to ROS. Antibody recognition pointed to the availability of free ethyl and isopropyl groups exposed at the non-extractable s-triazine residue. Therefore, it is suggested on the basis of antibody selectivities that binding of atrazine to ROS may take place by substitution of the chlorine residue. In the next step, aquatic ROS isolated from surface waters located in an agricultural area were examined for non-extractable s-triazines. ROS from a lake were found to contain bound residues, whereas none were detected in the creek samples. As an outlook the feasibility of serological characterization of ROS is discussed. The novel concept of serotyping is based on the fractionation of ROS by electrophoretic techniques followed by an immunoreaction with polyclonal antibodies directed against different ROS. When immunoelectrophoresis is used, precipitation lines can be compared and checked for identity and cross-reactivity. This approach can form the basis for classifying ROS and determine similarities with unknown ROS.     

Changes of Acute Toxicity of Organic Chemicals to Daphnia magna in the Presence of Dissolved Humic Material (DHM)

With a series of substituted anilines, a series of substituted phenols as well as diazinon and tetrabromobisphenol-A alterations of short-term acute toxicity to the waterflea Daphnia magna have been studied in the presence of dissolved humic material (DHM). The results may be categorised as follows: No alteration in acute toxicity occurred with: tetrabromobisphenol-A, o-toluidine, 3,4-dichloroaniline, and pentachlorophenol. Toxicity decreases significantly with: diazinon, 4-chloroaniline, and 4-nitrophenol. Significant toxicity increases were observed with 2,4-dichlorophenol and 2,4,5-trichlorophenol. As demonstrated for diazinon, our study reveals that in the presence of DHM and light the chemical speciation of this chemical is altered and daughter products are produced most likely via photoactive species of DHM. Most probably the toxicity of both the parent and daughter compounds is changed as well. Alterations in acute toxicity of organic chemicals may thus be attributed to the adsorption to DHM as well as to the photoactive species mediated production of daughter products with toxicity different from that of the parent compounds.