Validation of a pesticides multi-residue method in spices using QuEChERS by LC-MS/MS: comparison of EMR-lipid and HLB clean-up

Brand I., Kroschwald J., Büttner S., Witt G.
Validation of a pesticides multi-residue method in spices using QuEChERS by LC-MS/MS: comparison of EMR-lipid and HLB clean-up
Poster im Rahmen des European Pesticide Residue Workshops (EPRW 2022), 19. – 23.09.2022

Investigation results showed that some spices are frequently affected with pesticide residues, which also led to MRL exceedances. Especially in cumin, high levels and multiple residues were determinable. A pesticide multi-method was successfully validated using LC-MS/MS for cumin and a cumin-coriander-nutmeg mixture. Matrix effects were also considered [1].
For caraway, coriander and fennel seeds as well as nutmeg and black cumin, a multi-method for 182 pesticide residues was validated using QuEChERS by LC-MS/MS. Two cleaning materials were compared: enhanced matrix removal-lipid (EMR-lipid) and hydrophilic-lipohilic-balance clean-up (HLB). The validation was performed according to the criteria of the SANTE guideline for the concentration levels 0.01 and 0.1 mg/kg using solvent calibration.
The recoveries for the investigated spices were insufficient with HLB compared to EMR-lipid. For black cumin, a recovery range of 70 - 120 % could be achieved using HLB for only 30 % of the analytes. Similar results were obtained for the other spices. EMR-lipid gave a recovery of 70 - 120 % for more than 81 % of the compounds in caraway, coriander, and fennel seeds at 0.01 mg/kg. The relative standard deviation < 20 % was achieved for 98 % of the analytes for caraway, fennel seed and nutmeg. For black cumin, this requirement was fulfilled for only 62 % of the analytes.
Furthermore, matrix effects were considered. For coriander, fennel seed, black cumin and caraway, low matrix effects were determined for 90% of the analytes. A high ion suppression (ME < -20 %) was observed in nutmeg, especially for later eluting analytes (retention time of 17.5 - 24 min), due to the increase of coeluting matrix components. Phoxim showed the strongest signal suppression in nutmeg with 89 %. Metaflumizone showed significant signal enhancement in all spices (coriander 54 %, caraway 100 %, nutmeg 113 %, fennel seed and black cumin > 600 %). Signal enhancement was also observed for novaluron and lufenuron in fennel seed and black cumin. For quantification of these analytes, a standard addition or matrix-matched calibration is necessary.

Literatur
[1] Kroschwald J, Brand I (2021): Kreuzkümmel – Ein Trendsetter für die LC-MS/MS. Deutsche Lebensmittel Rundschau 117 (9):393-401