| 1. |
- Burestedt, E., et al.
(författare)
-
Optimisation and validation of an automated solid phase extraction technique coupled on-line to enzyme-based biosensor detection for the determination of phenolic compounds in surface water samples
- 1995
-
Ingår i: Chromatographia. - Heidelberg : Springer Berlin/Heidelberg. - 0009-5893 .- 1612-1112. ; 41:3-4, s. 207-215
-
Tidskriftsartikel (refereegranskat)abstract
- A fully integrated screening system for phenolic compounds was developed incorporating on-line solid phase extraction, fractionation and biosensor detection. Two different types of biosensors, solid graphite and carbon paste electrodes incorporating the enzyme tyrosinase, were compared and used in the screening system. Interfacing of the solid phase extraction and fractionation with the biosensor detection was given special attention since the biosensors were not compatible with the organic modifier used for desorption of phenols from the solid phase extraction step. The system was validated with conventional analytical techniques. Surface water samples from the Ebro river were spiked with 1,10, and 25μg L−1 of catechol, phenol,p-cresol, respectively. Three out of seven samples were spiked and the correct samples were identified, containing phenols equivalent to the spiked concentrations. © 1995 Friedr. Vieweg & Sohn Verlagsgesellschaft mbH.
|
|
| 4. |
- Önnerfjord, P., et al.
(författare)
-
On-line solid-phase extraction in liquid chromatography using restricted access pre-columns for the analysis of s-triazines in humic-containing waters
- 1996
-
Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 737:1, s. 35-45
-
Tidskriftsartikel (refereegranskat)abstract
- A coupled-column liquid chromatographic system using solid phase extraction pre-columns for the seven chlorotriazines, atrazine, desethylatrazine, desisopropylatrazine (DIA), propazine, simazine, desethylterbuthylazine and terbuthylazine, using photodiode-array detection (PDAD) was developed. Restricted access (RA), was investigated as a pre- column material, making use of non-adsorptive size exclusion of macromolecules and simultaneous dynamic portioning of the analytes, for the pre-concentration in environmental analysis. The RA phase was characterised and shown to solve problems with difficult matrix effects in humic-containing surface water samples. Other pre-column materials, e.g. reversed-phase C18, mono-functional C18, extraction disk mixture of C18 and styrene- divinylbenzene (PS-DVB) and LiChrolut EN, a polymeric sorbent specially designed for environmental analysis, were investigated and compared for their selectivity and stability, respectively. Comparisons were made with respect to selectivity and efficiency for the SPE columns separately and in combination with analytical columns. Recovery data and matrix dependencies were studied at concentration levels ranging between 0.1-10 μg/l. The RA pre-columns showed superior stability in complex environmental matrices, such as reference humic water and river water, due to the restriction of macromolecules. Retention properties with the RA alkyl-diol-silica were not sufficient for the most polar metabolites. However, efficient sorption/desorption kinetics were found with medium-polar and non-polar compounds. LiChrolut EN was found to strongly retain these polar metabolites as well as medium and non-polar solutes, and was selected for a deeper investigation (e.g. salinity dependence and pH). For a 10 x 2 mm I.D. pre- column, the breakthrough volume for the polar metabolite DIA was at least 150 ml, while for the RA pro-columns it was less than 10 ml. Unfortunately, this polymeric support was strongly effected, in terms of stability, in complex matrices which lead to repeated and expensive exchanging of pre-columns. However, in order to detect even the polar metabolites these pre-columns were finally used on-line together with liquid chromatography PDAD and thermospray mass spectrometry for the determination of triazines in water samples from the Ebro river during different seasons of the year.
|
|
