27
Figure 4. Non-targeted identification of fluridone in Pond 43. A database match for fluridone between a modelled chromatographic peak (gray area) and the observed peak (black trace). B. Comparison of a modelled mass spectrum for the proposed pseudomolecular ion [C19
H14 NO]M+H F3 C. Library searching of the observed HRAM CID MS2
(blue) and averaged full-scan observed data (black). spectrum (black)
returns a match to the EFS library entry for fluridone (blue) with a score of 70%.
Initial sampling for non-targeted screening consisted of 0.5 L grab samples collected and field extracted by SPE over two weeks in May 2010. Similarly, 10 mL samples were collected in May 2011 for quantitative analysis. Sample sites were chosen to represent various routes of micropollutant loading into the aquatic environment and potential routes of chemical exposure as detailed in Table 1. Golf course runoff consists of both turf-grass-management chemicals applied to the course and wastewater-derived contami- nants introduced through irrigation.
Broad-Spectrum HPLC-HRMS Screening
Initially a scoping gradient was run to determine which compounds may be present. This was done using coupled to a Thermo Scientific™ LTQ Orbitrap Velos™ MS, with the data analysis being performed using Thermo Scientific™ ExactFinder™, which
found approximately 1000 known compounds based on the available databases. The use of a high resolution mass spectrometer meant that a high degree of confidence could be associated with the identification of these compounds.
Targeted Quantification
Once the screen process had been performed a targeted quantification was performed using the EQuan MAX Plus™ online SPE and HPLC system (Thermo Scientific™, San Jose USA).
There are many different valve configura- tions that can be used for coupling of SPE to LC. In this scenario Figure 2 shows the configuration of a six port vale that is utilised to allow the hyphenation of SPE to LC, where two pumps are used, one is referred to the loading pump where the pump is
used to move the sample onto the SPE column, and the eluting pump which is used to elute the compound from the column to the detector. Specifically there are four steps when utilising this configuration; load, wash, elute and re-equilibration of the column. These steps are very comparable to the four basic steps involved in off-line solid phase extraction (condition, load, wash, elute) and serve comparable purposes. In most cases the loading and washing steps take place simultaneously.
The sample is loaded onto the extraction column in a weak solvent to ensure that retention of the compound is achieved. A wash step uses the same valve position and allows for a stronger wash solvent to be employed compared to the loading solvent is used in some cases. In both the load and the wash configurations, the valve is positioned such that all the eluent goes to the waste
Figure 5. Boxplots depicting the measured contaminant concentrations in storm- and wastewater retention ponds on Kiawah Island. Purple boxes represent the interquartile range and the bar represents the median value. Hashed lines depcit the range of the data and outliers are plotted as open circles.
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48
