5 Conclusions
When it comes to implementing protective legislation, there is a need for rapid and accurate methods of detection in order to minimise the potential impacts of PAHs and pesticides on the environment and human health. Risk assessment requires similarly precise results but would ideally need to be performed over a broad range of concentrations, in different matrices and with multiple residues simultaneously; analytical methods should be compatible with a high sample throughput to obtain suffi cient data.
Techniques like UHPLC-MS/MS can carry out rapid analyses without compromising data quality. Fast, multi-screening capabilities will have benefi ts not only for the environment, but will promote human health and safety through the robust detection and analysis of residues. Analytical laboratories now have the ability to analyse hundreds of pollutants, like PAHs or pesticides in a single sample.
References
[1] G. M. Watson, O. K. Andersen, T. S. Galloway, and M. H. Depledge, “Rapid assessment of polycyclic aromatic hydrocarbon (PAH) exposure in decapod crustaceans by fl uorimetric analysis of urine and haemolymph,” Aquat. Toxicol., vol. 67, no. 2, pp. 127–142, 2004.
Figure 1. Extracted ion chromatograms of pesticides in strawberry matrix extract applying a gradient length of 15 and 5 min. Conditions: Accucore™ aQ column (100 x 2.1 mm, 2.6 µm), mobile phase A) Water/Methanol (98:2, v/v, %) with 5 mM ammonium formate and formic acid 0.1% (v/v, %), and B) Water/Methanol (2:98, v/v, %) with 5 mM ammonium formate and formic acid 0.1% (v/v, %). Column temperature 25 ºC.
The UHPLC system used in this research showed an outstanding retention time precision from run-to-run and from sample-to-sample, which was the key factor for the development of the ultrafast UHPLC-MS method with very narrow SRM scan window [9, 10]. The run-to-run retention time repeatability was evaluated by seven consecutive injections for 50 compounds detected in all three matrices at 5 ppb level and revealed SD below 0.3 s.
The 15 minute and 5 minute LC-MS methods were validated based on four key criteria: accuracy, estimated at three different levels in the three different matrices; limits of quantifi cation (LOQs), based on RSD ≤ 15% and ion ratios; repeatability (%), based on RSDs %; and linearity, measured as squared correlation coeffi cient. With this in mind, the results can be interpreted according to how they performed across these criteria. The results obtained with the 5 minute UHPLC-MS method in terms of accuracy, LOQs, and repeatability were compared with the 15 minute method (Figure 2). The data showed that not only does the 5 minute UHPLC method produce similar results to the 15 minute method, it results in a 67% saving of analysis time.
[2] T. Wenzl, R. Simon, E. Anklam, and J. Kleiner, “Analytical methods for polycyclic aromatic hydrocarbons (PAHs) in food and the environment needed for new food legislation in the European Union,” TrAC - Trends Anal. Chem., vol. 25, no. 7, pp. 716–725, 2006.
[3] N. Berrojalbiz, S. Lacorte, A. Calbet, E. Saiz, C. Barata, and J. Dachs, “Accumulation and cycling of polycyclic aromatic hydrocarbons in zooplankton,” Environ. Sci. Technol., vol. 43, no. 7, pp. 2295–2301, 2009.
[4] European Commission, “Opinion of the Scientifi c Committee on Food on the risks to human health of Polycyclic Aromatic Hydrocarbons in food,” no. December, pp. 1–84, 2002.
[5] J. Popp, K. Peto, and J. Nagy, “Pesticide productivity and food security. A review,” Agronomy for Sustainable Development, vol. 33, no. 1. pp. 243–255, 2013.
[6] United States Environmental Protection Agency, “Appendix a To Part 136 Methods for Organic Chemical Analysis of Municipal and Industrial Wastewater Method 610— Polynuclear Aromatic Hydrocarbons,” 1995.
[7] European Commission, “COMMISSION RECOMMENDATION on the further investigation into the levels of polycyclic aromatic hydrocarbons in certain foods,” 2005.
[8] J. Wang, C. Yang, J. Beck, J. Massi, D. Ghosh, and M. Blackburn, “Analysis of 200+ Pesticides at 500 SRMs/s using a Non-Timed SRM MS Method and a Short LC Method on TSQ Endura MS.” 2014.
[9] Thermo Fisher Scientifi c, “How Solvent Delivery Technology Can Improve Confi dence in Peak Identifi cation and Quantifi cation,” Thermo Fisher Scientifi c Product Spotlight, 2014. [Online]. Available:
http://www.thermoscientifi
c.com/content/ dam/tfs/ATG/CMD/cmd-documents/bro/bro/chrom/lc/sys/SP-71188-Solvent- Delivery-Highest-Confi dence-Peak-Identifi cation-Quantifi cation-SP71188-EN. pdf?elqaid=1619&elqat=2&elqTrackId=97d9450580d44d908c72085db85bcb95. [Accessed: 01-Aug-2015].
[10] P. Carsten, M. De Pra, M. Martin, E. J. Sneekes, B. Bailey, and F. Steiner, “Is Retention Time Precision Only Affected by the LC Pump?” 2014.
Figure 2. The 15 min and 5 min LC-MS methods provide comparable data quality in all three food matrices.
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Benchtop NMR Spectrometer Used for Undergraduate Teaching at Virginia Commonwealth University
Magritek, a leading provider of compact NMR and MRI instruments, report on the use of their Spinsolve Benchtop NMR spectrometer in the Chemistry Department of Virginia Commonwealth University. It is being used in the undergraduate teaching program under the supervision of Ms Meredith Moses.
Ms Lucy (Meredith) Moses is a member of the Faculty in the Chemistry Department and is an Assistant Professor at Virginia Commonwealth University (VCU). She teaches a hands-on approach to enable students to understand and run analytical techniques rather than to rely solely on text books and second-hand spectra. Her group is using the Magritek Spinsolve benchtop NMR spectrometer.
The Spinsolve is used in the teaching laboratories for Organic Chemistry Lab. It is integrated mostly for second semester students but is also used for the Honors section of the fi rst semester. Ms Moses said: “We use the NMR so that the students know and understand about NMR. If they go to grad school or industry, they need to be familiar with it. Also, they are expected to be able to analyse spectra for their second semester (lecture) fi nal exam. I like them to produce spectra of their own compounds so they know if they got the right product or not. Some instructors just hand out spectra of one groups’ sample or use literature spectra, but that somewhat defeats the purpose of a practical course. Students should know how good their product is.”
The Magritek Spinsolve benchtop NMR spectrometer is supplied worldwide to academics in teaching and research; to industry for research and reaction monitoring through to product quality control. To obtain full details of the Spinsolve benchtop NMR spectrometer and the full range of analytical products from Magritek, visit
www.magritek.com
36968pr@reply-direct.com
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