Determination of Irgarol 1051 in Western Mediterranean sediments. Development and application of supercritical fluid extraction–immunoaffinity chromatography procedure

A supercritical fluid extraction (SFE) procedure for Irgarol 1051 (i.e. 2-(tert-butylamino)-4-(cyclopropylamino)-6(methylthio)-1,3,5-triazine) determination in marine sediments, which minimises the solvent usage, is developed and compared to a conventional extraction technique (i.e. sonication). First, the use of methanol (MeOH) in the presence of trifluoroacetic acid (TFA) as secondary modifier of supercritical carbon dioxide was evaluated. Extraction efficiency was strongly dependent on the modifier content but lesser on pressure (100–410 bar) and temperature (60–200°C). In the selected extraction conditions (20% MeOH/TFA 0.65 M, 370 bar, 150°C) recoveries higher than 87% were obtained and the limit of detection was 3 ng g^-1 and the relative standard deviation of 10% (N=3) by GC coupled to mass spectrometry (GC-MS) in the electron impact mode. The developed SFE procedure is more convenient to extract Irgarol 1051 than the agitation plus sonication methods concerning on solvent usage (1.5 vs. 20 mL) being compatible with immunochemical procedures avoiding any solvent transfer step. The developed SFE combined with immunoaffinity chromatography (IAC) is highly selective allowing the determination of Irgarol by gas chromatography with nitrogen–phosphorus detection or in sediments at low ng g^-1 level (11–35 ng g^-1) from Mediterranean marina and harbour sediments.