Abstract
We report on the hyphenation of the modern flow techniques Lab-In-Syringe and Lab-On-Valve for automated sample preparation coupled online with high-performance liquid chromatography. Adopting the bead injection concept on the Lab-On-Valve platform, the on-demand, renewable, solid-phase extraction of five nonsteroidal anti-inflammatory drugs, namely ketoprofen, naproxen, flurbiprofen, diclofenac, and ibuprofen, was carried out as a proof-of-concept. In-syringe mixing of the sample with buffer and standards allowed straightforward pre-load sample modification for the preconcentration of large sample volumes. Packing of ca. 4.4 mg microSPE columns from Oasis HLB® sorbent slurry was performed for each sample analysis using a simple microcolumn adapted to the Lab-On-Valve manifold to achieve low backpressure during loading. Eluted analytes were injected into online coupled HPLC with subsequent separation on a Symmetry C18 column in isocratic mode. The optimized method was highly reproducible, with RSD values of 3.2% to 7.6% on 20 µg L−1 level. Linearity was confirmed up to 200 µg L−1 and LOD values were between 0.06 and 1.98 µg L−1. Recovery factors between 91 and 109% were obtained in the analysis of spiked surface water samples.
Highlights
Nonsteroidal anti-inflammatory drugs (NSAIDs) are known for their effectiveness in treating pain, fever, and inflammation
We explore the combination of LOV-bead injection (BI) with the flow-batch technique Lab-In-Syringe (LIS) [42,43] as a proof-of-concept
Sorbents of particle sizes of >100 μm are used for BI due to the resulting low flow resistance
Summary
Nonsteroidal anti-inflammatory drugs (NSAIDs) are known for their effectiveness in treating pain, fever, and inflammation. NSAIDs can be purchased without prescription and are used in livestock breeding [3] so they are some of the most consumed drugs today. Apart from improper disposal of outdated drugs via domestic waste and drainage, the biotransformation of NSAIDs is only partial [4,5]. The accumulation of NSAIDs can have severe adverse effects on aquatic organisms and be toxic to various animals [9]. For these reasons, DCF was included in the watchlist of substances in the EU (2013/29/EU directive) [10] and DCF, IBU, and NAP were classified as emerging organic pollutants
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