Proposed Guidelines for Solid Phase Extraction of Suwannee River Dissolved Organic Matter.

This paper proposes improved guidelines for dissolved organic matter (DOM) isolation by solid phase extraction (SPE) with a styrene-divinylbenzene copolymer (PPL) sorbent, which has become an established method for the isolation of DOM from natural waters, because of its ease of application and appreciable carbon recovery. Suwannee River water was selected to systematically study the effects of critical SPE variables such as loading mass, concentration, flow rate, and up-scaling on the extraction selectivity of the PPL sorbent. High-field Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) and proton nuclear magnetic resonance ((1)H NMR) spectroscopy were performed to interpret the DOM chemical space of eluates, as well as permeates and wash liquids with molecular resolution. Up to 89% dissolved organic carbon (DOC) recovery was obtained with a DOC/PPL mass ratio of 1:800 at a DOC concentration of 20 mg/L. With the application of larger loading volumes, low proportions of highly oxygenated compounds were retained on the PPL sorbent. The effects of the flow rate on the extraction selectivity of the sorbent were marginal. Up-scaling had a limited effect on the extraction selectivity with the exception of increased self-esterification with a methanol solvent, resulting in methyl ester groups. Furthermore, the SPE/PPL extract exhibited highly authentic characteristics in comparison with original water and reverse osmosis samples. These findings will be useful for reproducibly isolating DOM with representative molecular compositions from various sources and concentrations and minimizing potential inconsistencies among interlaboratory comparative studies.

Comparison of a fluoroquinolone surface plasmon resonance biosensor screening assay with established methods.

The performance of a previously developed immunochemical biosensor screening method for fluoroquinolone (FQ) antibiotics in poultry muscle, fish and egg was compared with established methods. Blank sample material of the target matrices was individually spiked with the FQs at half maximum residue levels. Homogeneity of the test materials was confirmed by liquid chromatography-mass spectrometry (LC-MS/MS). Identical sets of spiked samples as well as incurred samples from a previous feeding experiment were sent to three independent laboratories and analysed by LC-MS/MS, a microbiological assay and the new biosensor assay. The new method correctly identified all contaminated samples and demonstrated advantages in sensitivity and analysis time compared to the microbiological screening assay.