Synthesis and spectrophotometric studies of heterocyclic bay-substituted naphthalenediimide colorimetric pH indicators

Four naphthalenediimide colorimetric pH indicators were synthesized with N,N-dimethylethyleneamine at the imide positions and with 5- to 7-membered heterocyclic rings at the bay positions, namely pyrrolidine, morpholine, piperidine and azepane. The pH indicators are constructed in a modular receptor–spacer–fluorophore–spacer–receptor format based on a photoinduced electron transfer (PET) design. The compounds were studied by UV–visible absorption and steady-state fluorescence spectroscopy in 1:1 (v/v) methanol/water. Brilliant colour changes are observed between pH 2 and 4 due to an internal charge transfer (ICT) mechanism. Fluorescence turn-on enhancements range from 10–37 fold; however, the maximum fluorescence quantum yield in the presence of acid is <0.004, which is below naked eye detection. Hence, from the viewpoint of a human observer, these chemosensors function as colorimetric YES logic gates, and fluorimetric PASS 0 logic gates.peer-reviewe

Immobilisation of metals in contaminated landfill material using orthophosphate and silica amendments : a pilot study

Immobilization and encapsulation of contaminants using silica and orthophosphate based chemical treatments are emerging technologies applicable to the management of metal contaminated soil. While the efficacy of orthophosphate treatment is well documented, there is a paucity of research on the application of silica or coupled orthophosphate and silica chemical treatments to metal contaminated soil. This paper presents a pilot scale bench study on the use of silica and coupled orthophosphate-silica treatments for the immobilization of metal contaminants in soil material obtained from the Thala Valley landfill, East Antarctica, which in places has petroleum hydrocarbons mixed with metal-contaminated sediment. The performance of the treatments trialed was assessed by the concentrations of copper, zinc, arsenic and lead released using the Toxicity Characteristic Leaching Procedure. The results of this pilot study demonstrate that the orthophosphate-silica treatment was the most effective and reduced leachable copper, zinc and lead by 95%, 96% and 99%, respectively, relative to the experimental controls. Further development of this technique will require additional research evaluating its long-term performance under a range of environmental conditions. Studies investigating potential adverse effects of silica and orthophosphate-silica treatments are also necessary, to demonstrate the environmental risk and efficacy of these remediation technologies.6 page(s

Recent applications of chemometrics in one‐ and two‐dimensional chromatography

The proliferation of increasingly more sophisticated analytical separation systems, often incorporating increasingly more powerful detection techniques, such as high-resolution mass spectrometry, causes an urgent need for highly efficient data-analysis and optimization strategies. This is especially true for comprehensive two-dimensional chromatography applied to the separation of very complex samples. In this contribution, the requirement for chemometric tools is explained and the latest developments in approaches for (pre-)processing and analyzing data arising from one- and two-dimensional chromatography systems are reviewed. The final part of this review focuses on the application of chemometrics for method development and optimization

Long-Term Persistence of Pesticides and TPs in Archived Agricultural Soil Samples and Comparison with Pesticide Application

For polar and more degradable pesticides, not many data on long-term persistence in soil under field conditions and real application practices exist. To assess the persistence of pesticides in soil, a multiple-compound screening method (log <i>K</i>_ow 1.7–5.5) was developed based on pressurized liquid extraction, QuEChERS and LC-HRMS. The method was applied to study 80 polar pesticides and >90 transformation products (TPs) in archived topsoil samples from the Swiss Soil Monitoring Network (NABO) from 1995 to 2008 with known pesticide application patterns. The results reveal large variations between crop type and field sites. For the majority of the sites 10–15 pesticides were identified with a detection rate of 45% at concentrations between 1 and 330 μg/kg_dw in soil. Furthermore, TPs were detected in 47% of the cases where the “parent-compound” was applied. Overall, residues of about 80% of all applied pesticides could be detected with half of these found as TPs with a persistence of more than a decade