Chloropropanol is a class of compounds in which the hydroxyl groups on glycerol are replaced by chlorine, including monochloro propylene glycol: 3-chloro-1,2-propanediol (short for 3-MCPD), 2-chloro-1, 3-propanediol (or 2-MCPD) and dichloropropanol: 1, 3-dichloro-2-propanonl (or 1,3-DCP), 2, 3-dichloro-1-propanonl (2,3-DCP). In the chloropropanol series of compounds, the main component of contaminated food is 3-MCPD.
Material and Reagents
HPLC purity of n-hexane and ethyl acetate; analytically grade of sodium chloride and anhydrous sodium sulfate, Heptafluorobutyrylimidazole derivation agent;
3-MCPD standard (> 99% purity): dissolve in ethyl acetate;
D5-3-MCPD internal standard: dissolve in ethyl acetate.
Weigh 4 g milk powder sample and put into a 50 mL centrifuge tube, add 40 μL of 0.8 μg/mL D5-3-MCPD internal standard. Transfer 4 g of 20 % sodium chloride solution, sonicate for 10 min and centrifuge at 8000 rpm for 10 min. If there is no exist of supernatant, add another 4 g of 20 % sodium chloride solution and repeat the sonicate extraction and centrifugation above. Supernate was ready for SPE preparation.
Decant the supernatant into Cleanert MCPD, equilibrate for 10 min. Wash the cartridge with 10mL n-hexane, dispense into waste tray and vacuum the cartridge. Eluted with 15 mL ethyl acetate and blow the extract under nitrogen flow below 30 ℃ to 0.5 mL. Make up to 2 mL with n-hexane followed by derivatization.
Add 0.04 mL of N-Heptafluorobutyrylimidazole to the extract, and seal it immediately. Vortex for 30 s and incubate at 70 ℃ for 20 min, cool the liquid to ambient. Transfer 2 mL of 20% sodium chloride solution, vortex for 1 min, stratify until the aqueous phase is clear. Take the upper n-hexane and add about 0.3 g anhydrous sodium sulfate for water removal. Transfer the supernatant for analysis.
GC column: DA-5MS; 30 m × 0.25 mm × 0.25 µm;
Inlet temperature: 250 ℃, splitless;
Oven program: 50 ℃ (1 min); 2 ℃/min to 90 ℃ (20 min); 40 ℃/min to 270 ℃ (4.5 min); 270 ℃ (5 min);
Carries gas: Helium ( ³ 99.999%), constant flow mode, 1 mL/min;
MS: EI, SIM/scan;
MS temperature: 250 ℃ (source);
Solvent delay: 5 min;
Injection value: 1 µL.
Table 1 MS Ion Parameters
Results and Discussion
GC/MS was used for the identification of 3-MCPD derivative. Figure 2 shows the chromatogram of milk powder sample prepared by the cartridge. The Cleanert MCPD cartridge effectively removed interferences from the sample matrix. As you can see in Figure 3, sharp peaks were observed for 3-MCPD derivative on DA-5MS GC columns. Sharper peaks greatly enhance the height of the signal and therefore provide better signal-to-noise ratios and greater sensitivity. The recovery of the method was evaluated for 3-MCPD derivative spiked at 0.02 mg/kg level. The repeatability was evaluated on three duplicate samples. The spiked samples were treated according to the sample-preparation procedure describe above. The recovery and repeatability data are listed in Table 2. The method resulted in good recoveries (over 90%) and repeatability with RSDs less than 5%.
Table 2 Recovery and Repeatability of 0.02 mg/kg Spiked Samples (n = 3)
Figure 1 Chromagram of 0.04 µg/mL3-MCPD derivative standard and internal standard derivative
Figure 2 Chromagram of blank milk powder sample
Figure 3 Chromagram of 0.02 mg/kg spiked milk powder sample
An efficient solid phase extraction sample preparation procedure was developed for the extraction of 3-MCPD in milk powder sample. The Cleanert MCPD cartridge effectively remove the interfences from the sample matrix for longer uptime of the analysis system. GC/MS is ideal for the rapid analysis of 3-MCPD. Excellent recovery and reproducibilty were obtained in this application note.
Max. load 5 mL sample
Qdaura Automatic SPE System
4 channels, 24 positions
30 m × 0.25 mm × 0.25 µm
1.5 mL vials
Screw neck vials, 12 × 32 mm
Caps and Septa
Screw neck cap, center hole; red silicone/ white PTEE septa, slitted
Syringe Filter (Nylon)
Monofilm, 13 mm, 0.22 μm
Disposable Needle-Free injection systems
2 mL, 100/pk