EN 17424-2020 pdf download.Foodstuffs – Determination of aflatoxins in spices other than paprika by IAC clean-up and HPLC-FLD with postcolumn derivatization.
6.13.6 System for derivatization with electrochemically generated bromine, e.g. KOBRA CELL3 (only to be used with mobile phase B (5.30)) and PTFE reaction tubing of 34 cm minimum and 0,5 mm internal diameter.
6.13.7 Alternative System for derivatization by photochemical reaction, e.g. Photochemical Reactor for Enhanced Detection (PHREDTM4), only to be used with mobile phase A (5.29). The photochemical reactor is inserted between the HPLC column and the detector inlet The knitted reactor consists of PTFE tubing of 20 m and 0.25 mm internal diameter.
6.13.8 Fluorescence detector.
Recommended settings for adjustable detectors are wavelengths of A = 364 nm (excitation), A = 440 nm (emission) and a bandwidth of 18 nm.
613.9 Data evaluation system
7 Procedure
7.1 Extraction of aflatoxins from the sample
All samples shall be extracted and cleaned-up with the IAC on the same day as analysis due to lack of stability of the analytes in extracted samples.
NOTE During method development and validation lower recovery values were observed for sample extracts that were not cleaned-up on the same day.
Weigh a test portion of 25 g [ms.] to the nearest 0,1 g into a 250 ml centrifugation bottle (6.3). Add 5,0 g of sodium chloride (5.10). A larger sample weight may be used provided the sample or extraction solvent volume or sodium chloride weight ratio is maintained.
Add 100 ml WeJ of the extraction solution (5.17) and blend for approximately 3 mm to 5 mm with a blender (6.6). Alternatively, shake vigorously by hand for approximately 15 s to 30 s and then for approximately 30 mm with a shaker (6.7). For various types of shakers (e.g. horizontal platform shaker or vertical wrist shaker) the motion speed shall be adjusted to obtain maximum agitation of the extraction mixture.
After extraction, place the bottles in a centrifuge (6.4) and centrifuge for approximately 10 mm at approximately 2 000g to 2 SOOg, and then titter the supernatant through fitter paper (6.9).
Add 59 ml of PBS/polysorbate 20 solution (5.16) and 1.0 ml of the filtrate into a conical flask (or similar). Shake well by hand. Check the pH of the diluted extract and adjust if necessary to pH 7,4 with sodium hydroxide solution (5.5). Use an aliquot of the diluted sample extract for IAC clean-up (7.3).
7.2 Determination of recovery
To determine the recovery rate by surrogate spike, add 125 itI of the mixed stock solution (5.25) to a known blank sample prior to extraction (corresponds to a mass fraction of S pg/kg aflatoxin B1 and G1 and 2,5 pg/kg aflatoxin B2 and G2 in the sample) and leave for approximately 30 mm at room temperature.
Follow the procedure according to 7.1 and 7.3 for the spiked and unspiked samples.
Where available, a suitable reference material may be used to determine the recovery rate.
7.3 IAC clean-up
The use of TAC can vary slightly from one manufacturer to another. Follow the manufacturers’ instructions.
Pass 30 ml of the diluted filtrate, (this contains 0,5 ml of the original extract, V) through the IAC (5.31) at a flow rate of approximately 3 mI/mm (i.e. a dropping speed of approximately I drop/s) or by gravity. Do not exceed a flow rate of 5 mI/mm.
After the filtrate has passed through the column, wash the column with approximately 20 ml of PBS
(5.14) at a flow rate of maximum 5 mI/mm and dry by applying little vacuum for approximately 5 s to
10 s or passing air through the IAC by means of a syringe (6.11) for approximately 10 s.
Elute the allatoxins in a two-step procedure. Apply 0,50 ml of methanol (5.1) on the column and let it pass through by gravity. Collect the eluate in a 4 ml vial that can be capped. Apply a second portion of 1,0 ml of methanol (5.1). Use a syringe to pass air through the column to collect the last few drops.
Pass 1,5 ml of water through the column and collect this in the same glass vial, to give a final volume of 3,0 ml (Vfin?J). Cap the 4 ml vial and mix for approximately 5 s. lithe solution is clear it can be used directly for IIPLC analysis. If the solution is not clear, filter through a syringe filter (6.12) prior to IIPLC injection.
7.4 HPLC-FLD analysis
7.4.1 General
The aflatoxins are separated by isocratic reversed-phase 1-IPLC with a reversed-phase column (6.13.3) and an appropriate mobile phase A (5.29) or B (5.30).
Adjust the flow rate according to the column dimension.
The recommended flow rate is 1,0 mI/mm for a column with an inner diameter of 4,6 mm.
The aflatoxins elute in the order G2, G1, B2 and B1 with retention times of approximately 9 mm, 10 mm, 12 mm and 15 mm respectively, and should be baseline-resolved. EN 17424-2020 pdf download.

Share on Facebook

Post on X

Follow us

Save