At the risk of causing drug resistance, the antiviral drugs amantadine and rimantadine used to treat influenza A, have been banned in poultry farming in China and the USA. Despite these legislations, these drugs are still used illegally in China.
Yan et al. developed a novel sample pretreatment methodology to detect amantadine and rimantadine using ultra high performance liquid chromatography coupled with high resolution LTQ Orbitrap mass spectrometer using an LTQ Orbitrap system (UHPLC-LTQ Orbitrap MS,Thermo Scientific).1
The team designed sample extraction on a modified QuEChERS method. They chose acetonitrile (1% acetic acid, v/v) as an extraction solution and C18 sorbent for clean-up since it gave the best recoveries for both drugs (over 60%). They also determined that adding 1% HAc-ACN and 1% NH3·H2O-CAN to the acetonitrile solution increased the recoveries to over 70%.
UHPLC-LTQ Orbitrap MS was chosen based on an excellent track record in previous studies to consistently and reliably analyze chemical residues in animal tissues. Some of the unique features of LTQ Orbitrap MS include a high resolving power (up to 100,000 FWHM) and the ability to estimate the accurate mass of the target compounds within less than 1 mDa.To determine amantadine and rimantadine, the authors followed the recommendation of previous work that relied on a mass assignment (<2 ppm) and a high resolving power (>50,000).2
Using optimized conditions for LTQ Orbitrap MS, the team detected amantadine and rimantadine in spiked chicken muscle at three concentration levels (5.0, 10.0, and 20.0 ug/kg) based on six replicates.They were able to detect pseudomolecular ions [M+H]+ of amantadine and rimantadine at m/z 152.14342 and 180.17464 with an accuracy within 1 mDa.
They successfully applied the working protocol to analyze in 100 chicken muscle samples for the presence of amantadine and rimantadine. Out of the 100 samples surveyed, amantadine was detected in 3 chicken muscle samples with concentrations of 4.25, 37.3 and 86.0 g/kg. No additional amantadine or rimantadine residue was detected in any other samples.
The authors maintain that the use of QuEChERS along with UHPLC-LTQ Orbitrap MS to detect amantadine and rimantadine is sensitive, with excellent intra- and inter-day accuracy.
1. Yan, H. et al. (2013) “Determination of amantadine and rimantadine in chicken muscle by QuEChERS pretreatment method and UHPLC coupled with LTQ Orbitrap mass spectrometry.” Journal of Chromatography B: Analytical Technologies in the Biomedical Life Sciences,. Nov 1; 938:8-13. doi: 10.1016/j.jchromb.2013.08.020. Epub 2013 Aug 27.
2. Kellmann, M. (2009) “Full scan MS in comprehensive qualitative and quantitative residue analysis in food and feed matrices: How much resolving power is required?”, Journal of the American Society for Mass Spectrometry, August 2009, Volume 20, Issue 8, (pp 1464-1476) Date: 27 May 2009