Analysis of HMF by HPLC

Transcription

1 COST Action 927 Training School Building Skills on the Analysis of Thermal Process Contaminants in Foods October 2007, Ankara Analysis of HMF by HPLC Vural Gökmen O O OH

2 Background O COOH O R 2 Carbonyl compound COOH OH At lower temperature processes, Maillard reaction is mainly responsible for HMF formation. R 1 NH 2 Amino compound R 1 N H R 2 N-Glycosylated OH H 2 O R 1 COOH N H O CO 2 R 2 Schiff base At higher temperature processes, hexose dehydration is mainly responsible for HMF formation. High acidity accelerates the formation. R 1 N H O Decarboxylated Schiff base R 2 R 1 N H O R 2 Hexose dehydration HO OH OH Maillard reaction O O OH Hydroxymethylfurfural HO OH O -D-Glucofuranose - 3H 2 O O O OH Hydroxymethylfurfural

3 It forms during thermal process and storage! Amino acids & Sugars Thermal Process / Storage HMF

4 Some facts on HMF No need to heat at elevated temperatures to form HMF as in the case of acrylamide. All the foods at which acrylamide is present contains certain levels of HMF. Even more foods (jams, jellies, fruit juices, honey, etc) contain HMF. Its level tends to increase during storage. Foods having high sugars are at high risk.

5 Molecule Properties Chemical structure Aldehyde Alcohol Furan ring Soluble in water, alcohols MW=126 [M+H] m/z 127, [-OH+H] m/z 109 Absorbs well λ max = 285 nm O O OH

6 Thermally Processed Food Proximate Composition Carbohydrates Sugars (up to 20 %) Polysaccharides Starch (up to 20 %) Proteins (up to 15 %) Lipids (up to 40 %) HMF (mg/g levels) WATER

7 PART I AQUEOUS EXTRACTION without SOLID PHASE EXTRACTION

8 Case Study Aqueous Extraction Carrez Clarification Cold Centrifugation (~0 o C) SPE Cleanup hydrophobic & cation exchange action LC/UV Detection 285 nm LC/MS Detection APCI+, m/z 127, m/z 109

9 Scheme for HMF Analysis Representative Sampling Homogenization Water / Organic Solvent Carrez clarificaion SPE LC/UV LC/MS Extraction Extract Cleanup Detection

10 Equipments Solid sample grinder Analytical balance Wortex mixer Ultra Turrax homogenizer Centrifuge with cooling HPLC LC/MS Agilent 1100 HPLC Diode Array Detector

11 Chemicals and Consumables Water Methanol Acetonitrile Formic or acetic acid Carrez I & Carrez II Disposables tube, syringe, eppendorf, tip, vial, filter SPE cartridge Waters Oasis HLB

12 Sample Homogenization 4 o C

13 Extraction Vortex for 3 min 1.0 g 9 ml 10 mm water 0.5 ml Carrez I & II Raw extract recentrifuge Fat layer Solid Centrifuge 5000 rpm x 10 min (~ 0 o C)

14 SPE Cleanup Strategy for HMF Sample Load 1.0 ml Condition Water Wash 0.5 ml Diethylether Elution Co-extractives HMF Dry cartridge under N 2 Redissolve in water Discard Evaporate under N 2

15 LC/UV Analysis LC

16 LC/UV Chromatogram mau 50 UV detection at 285 nm Crisp bread 10 1 µg/ml standard min Figure. LC-UV chromatogram of crisp bread containing 21.5 mg/kg of HMF. Chromatographic conditions; column Atlantis dc18 (4.6 x 250 mm, 5 µm), mobile phase mixture of 0.1% formic acid and acetonitrile (90:10, v/v) at a flow rate of 1.0 ml/min at 25 o C, detection 285 nm

17 Low concentrations mau min Figure. Chromatogram of a snack with low HMF content (1.1 mg/kg). Chromatographic conditions; column Atlantis dc18 (4.6 x 250 mm, 5 µm), mobile phase mixture of 0.1% formic acid and acetonitrile (90:10, v/v) at a flow rate of 1.0 ml/min at 25 o C, detection 285 nm

18 Some comments Presence of interfering co-extractives may cause over-estimation of HMF in foods. This is specifically important for the samples with lower HMF concentrations. In this case, better sample preparation approaches, which is able to eliminate interfering co-extractives, are required.

19 Case Study-1 Analysis of HMF in crisp bread Portions of ground sample are ready for analysis.

20 PART II AQUEOUS EXTRACTION with SOLID PHASE EXTRACTION

21 Advanced analysis of HMF EXTRACTION SPE CLEANUP LC/UV/MS DETECTION

22 LC/UV/MS Analysis UV detection at 285 nm MS detection in SIM mode APCI+ m/z 127 and m/z 109 Rapid resolution chromatography Atlantis dc18, 2.1 x 150 mm (3 µm) Mobile phase 10 mm Formic Acid : Acetonitrile (95:5, v/v) 0.2 ml/min at 30 o C

23 Good linearity mau nm ppb min SIM m/z ppb min

24 Over-estimation of HMF mau overestimates 80% Before SPE Cleanup After SPE Cleanup 285 nm Sample : Cookie 2.5 mg/kg HMF min Figure. Chromatogram of a cookie sample. Chromatographic conditions; column Atlantis dc18 (2.1 x 150 mm, 3 µm), mobile phase mixture of 10 mm formic acid and acetonitrile (95:5, v/v) at a flow rate of 0.2 ml/min at 25 o C, detection 285 nm

25 Over-estimation of HMF Before SPE Cleanup overestimates 45% SIM m/z 127 nm Sample : Cookie mg/kg HMF After SPE Cleanup min Figure. Chromatogram of a cookie sample. Chromatographic conditions; column Atlantis dc18 (2.1 x 150 mm, 3 µm), mobile phase mixture of 10 mm formic acid and acetonitrile (95:5, v/v) at a flow rate of 0.2 ml/min at 25 o C, detection SIM m/z 127

26 Peak Purity Check after SPE

27 With SPE Cleanup mau INFANT FORMULAE 1.4 mg/kg HMF 1 µg/ml 285 nm Sample min Figure. Chromatogram of a infant formulae with low HMF content (1.4 mg/kg). Chromatographic conditions; column Atlantis dc18 (2.1 x 150 mm, 3 µm), mobile phase mixture of 10 mm formic acid and acetonitrile (95:5, v/v) at a flow rate of 0.2 ml/min at 25 o C, detection 285 nm

28 With SPE Cleanup INFANT FORMULAE 1.4 mg/kg HMF SIM m/z µg/ml Sample min Figure. Chromatogram of a infant formulae with low HMF content (1.4 mg/kg). Chromatographic conditions; column Atlantis dc18 (2.1 x 150 mm, 3 µm), mobile phase mixture of 10 mm formic acid and acetonitrile (95:5, v/v) at a flow rate of 0.2 ml/min at 25 o C, MS detection at m/z 127 & m/z 109

29 Reproducible SPE results mau 1.6 INFANT FORMULAE 285 nm min Figure. Chromatogram of a infant formulae with low HMF content (1.5 mg/kg). Chromatographic conditions; column Atlantis dc18 (2.1 x 150 mm, 3 µm), mobile phase mixture of 10 mm formic acid and acetonitrile (95:5, v/v) at a flow rate of 0.2 ml/min at 25 o C, MS detection at m/z 127 & m/z 109

30 LC/UV/MS CRISP BREAD 285 nm SIM m/z min Figure. Chromatogram of crisp bread (24 mg/kg). Chromatographic conditions; column Atlantis dc18 (2.1 x 150 mm, 3 µm), mobile phase mixture of 10 mm formic acid and acetonitrile (95:5, v/v) at a flow rate of 0.2 ml/min at 25 o C, MS detection at m/z 127 & m/z 109, and UV detection at 285 nm

31 Case Study-2 Analysis of HMF with SPE Portions of ground sample are ready for analysis.

32 Further readings