Abstract
During sample preparation and analysis, samples are coming in contact with different labware materials. By four unrelated analytical (phytochemical and pharmaceutical) case-studies and employing different analytical techniques, we demonstrated the potential misinterpretation of analytical results due to the use of contaminants-leaching labware during sample handling. Oleamide, a common polymer lubricant and a bioactive compound, was identified as a main analytical interference, leaching from different labware items into solvents, recognised as chemically compatible with the tested polymer material. Moreover, anti-inflammatory effect of oleamide at 100 μg mL−1 and considerable pro-inflammatory effect of the plastic syringe extractables (containing oleamide) at the same level were shown in a TLR4-based bioassay. Taking these results into account, together with the fact that oleamide can be a compound of natural origin, we would like to notify the professional public regarding the possible erroneous oleamide-related analytical and bioassay results due to the use of oleamide-leaching labware. Researchers are alerted to double check the real source of oleamide (labware or natural extract), which will prevent further reporting of false results. Analysis of procedural blanks with de-novo developed UHPLC-ESI-MS method is, among some other strategies, proposed for detection of oleamide interference and avoidance of misleading results of certain analyses.
Highlights
During sample preparation and analysis, samples are coming in contact with different labware materials
HPTLC chromatogram obtained by the in-house method for separation of lipid classes (Fig. 1) showed intensive bands of impurities after derivatisation with molybdophosphoric acid reagent (MoP) at RF zones of acetone mobile polar lipids (AMPL; RF = 0.07 and RF = 0.10) for extracts of different membrane filters attached to plastic syringes
Different labware was tested by this method and the results summarized in Table 1 under the label ‘LC-MS’ show that oleamide migrates into the extraction media from some plastic labware and surprisingly from some non-plastic labware either after single or multiple extraction procedures
Summary
During sample preparation and analysis, samples are coming in contact with different labware materials. Anti-inflammatory effect of oleamide at 100 μg mL−1 and considerable pro-inflammatory effect of the plastic syringe extractables (containing oleamide) at the same level were shown in a TLR4-based bioassay Taking these results into account, together with the fact that oleamide can be a compound of natural origin, we would like to notify the professional public regarding the possible erroneous oleamide-related analytical and bioassay results due to the use of oleamide-leaching labware. We would like to alert analytical chemists about the need to double check the real origin of oleamide, preventing misinterpretation of analytical results and at the same time notify labware manufacturers regarding this issue This will prevent future publication of erroneous data and aid to the quality and reliability of the future studies. Oleamide can be present in labware itself, mostly made of plastic, and only careful analytical approach could eliminate this interference, as discussed in this paper
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