October Analytical Method of Cereulide in Processed Cereal-Based Foods and Milk Powder by LC-MS/MS

Transcription

1 October LC-MS/MS Analytical Method of Cereulide in Processed Cereal-Based Foods and Milk Powder by LC-MS/MS Yoh-ichi Y6IHJ@6L6, Hanako I>96, Kazuko N6<6I6, Masashi M>N6BDID, Takahiro M6IHJ96, Hironobu IID, Munetomo N6@6BJG6 and Kazuhiro FJ?>I6 Saito Laboratory, Japan Food Research Laboratories: Saitoasagi, Ibaraki-shi, Osaka , Japan; Corresponding author An LC-MS/MS method for analysis of cereulide, an emetic toxin produced by Bacillus cereus, was developed. Cereulide was extracted from samples, fried rice, pan-fried noodles, red bean paste and baby formula, with methanol and purified using Oasis HLB cartridges. LC separation was performed on a C18 column with a mixture of formic acid solution and methanol containing ammonium formate as a mobile phase, and the mass spectrometer was operated in the positive electrospray ionization mode. Performance evaluation showed that trueness was higher than 70 and repeatability and reproducibility were within 10. The limits of quantification were lower than 1 g/kg. (Received April 1, 2011) Key words: cereulide; valinomycin; - LC-MS/MS; Bacillus cereus emetic toxin (CER) 1) 2) 2) CER CER ) NMR 4) (VAL) CER HEp-2 5) 8) yatsukaway@jfrl.or.jp CER LC-MS (/MS) 9) 14) CER CER Bauer 13) CER 13 C Biesta- Peters 14) CER LC-MS (/MS) CER CER Bauer 13) g/kg CER CER (10 1,280 g/kg) 8) CER 1 g/body 15) CER VAL LC-MS/MS CER

2 CER CER 1 mg /ml VAL 92.4 CER HEp-2 CER 2 LC-MS CER VAL 10 9) CER 100 VAL ) CER VAL 1 : VAL VAL CER CER CER (10 g/ml) VAL VAL 10 mg 100 ml (100 g/ml) 5 LC-MS Millipore Milli-Q ADVANTEC GA-55 Waters Oasis HLB 3 cc (60 mg) Millipore Millex-LG 0.20 m 3. LC-20 AB Sciex 4000 Q TRAP 4. Mightysil RP-18 GP (3 m, 50 mm 2 mm i.d.) 40 A 2 mmol/l 0.1 B 2 mmol/l B Table ml/min 10 L Table 1 5. (IS) VAL 10 ng/ml 0.5, 1, 5, ng/ml CER 10 L LC-MS/MS IS g 2.5 g IS 25 ng (50 ng/ml 500 L) 30 ml 30 3,500 rpm, ml 10 5mL 40 3mL Oasis HLB 8mL 40 6mL 4mL 3mL 60 3mL Oasis HLB 70 3mL 90 5mL ml 10 L LC-MS/MS Operating conditions of MS/MS Ionization ESI, positive Curtain gas 20 psi Ion spray voltage 5,500 V Ion spray temperature 450 Ion source gas 1 50 psi Ion source gas 1 60 psi Collision gas 6 Declustering potential 166 V Entrance potential 10 V Analyte Transition (m/z) Collision energy (V) Collision exit potential (V) CER 1, , VAL 1, Daughter ion for quantitation Vol. 52, No LC-MS/MS (100 ng/ml) MS CER VAL (Fig. 1) 0.1 (1 : 9, v/

3 Fig. 1. MS spectra of CER (A, B) and VAL (C, D) obtained by direct infusion of standard solution (100 ng/ml) prepared in 0.1 formic acid methanol (1 : 9, v/v) mixture (A, C) or 0.1 formic acid methanol mixture (1 : 9, v/v) containing 2 mmol/l ammonium formate (B, D) October 2011 LC-MS/MS 289

4 290 Vol. 52, No. 5 Fig. 2. MRM chromatograms of CER standard solution (1 ng/ml) containing 10 ng/ml of VAL v) CER [M K ] [M NH 4 ] VAL IS CER [M K ] CER 1 CER VAL [M NH 4 ] 2 mmol/l 0.1 (1 : 9, v / v) CER VAL [M NH 4 ] LC-MS/MS 2 mmol/l mmol/l LC-MS/MS CER VAL (Fig. 2). 0.5, 1, 5, ng/ml ml/ng, y CER Oasis HLB 2) Oasis HLB 3 cc (60 mg) Oasis HLB CER VAL 70, 80, Oasis HLB (Table 2) Table 2. MeOH ( ) Elution pattern of CER and VAL (25 ng) from the Oasis HLB cartridge with 10 ml of elution solution CER Recovery ( ) VAL Percentage of MeOH in the elution solution 90 CER 94.3, VAL CER 40.3, VAL 72.5 CER VAL Oasis HLB Oasis HLB Oasis HLB Oasis HLB 2 Oasis HLB 3. CER

5 Fig. 3. MRM chromatograms of (A) blank fried rice; (B) fried rice fortified with 1 g/kg of CER; (C) blank pan-fried noodles; (D) pan-fried noodles fortified with 1 g/kg of CER; (E) blank red bean paste; (F) red bean paste fortified with 1 g/kg of CER; (G) blank baby formula; (H) baby formula fortified with 1 g/kg of CER Arrow: Expected retention time of CER October 2011 LC-MS/MS 291

6 292 Vol. 52, No. 5 Table 3. Trueness, repeatability and reproducibility Sample Fortified ( g/kg) Trueness ( ) Repeatability (RSD ) Reproducibility (within-laboratory) (RSD ) Fried rice Pan-fried noodles Red bean paste Baby formula Two replicate sample preparations on 5 separate days CER (Fig. 3). 3.2 CER 2 5 CER 200 g CER 1 g 5 g/kg 1/5 1 g/kg g g (Table 3). Fig VAL Oasis HLB 90 VAL CER 6 CER VAL LC-MS(/MS) CER VAL 70 CER VAL Table 4. VAL CER 1 g/kg (SD) ( 10 SD) ( SD) 16) Table 4 1 g/kg Limit of quantitation (LOQ) and limit of detection (LOD) Sample LOQ ( g/kg) LOD ( g/kg) Fried rice Pan-fried noodles Red bean paste Baby formula CER 9), 14) CER VAL CER 2. CER IS VAL [M NH 4 ] LC-MS/MS 3. CER Oasis HLB g/kg CER

7 October 2011 LC-MS/MS 293 1) Turnbull, P. C., Kramer, J. M., Jorgensen, K., Gilbert, R. J., Melling, J. Properties and production characteristics of vomiting, diarrheal, and necrotizing toxins of Bacillus cereus. Am. J. Clin. Nutr., 32, (1976). 2) 2004, p (ISBN ) 3) Agata, N., Mori, M., Ohta, M., Suwan, S., Ohtani, I., Isobe, M. A novel dodecadepsipeptide, cereulide, isolated from Bacillus cereus causes vacuole formation in HEp-2 cells. FEMS Microbiol. Lett., 121, (1994). 4) Suwan, S., Isobe, M., Ohtani, I., Agata, N., Mori, M., Ohta, M. Structure of cereulide, a cyclic dodecadepsipeptide toxin from Bacillus cereus and studies on NMR characteristics of its alkali metal complexes including a conformational structure of the K complex. J. Chem. Soc., Perkin Trans. 1, 7, (1995). 5) Hughes, S., Bartholomew, B., Hardy, J. C., Kramer, J. M. Potential application of a HEp-2 cell assay in the investigation of Bacillus cereus emetic-syndrome food poisoning. FEMS Microbiol. Lett., 52, 7 12 (1988). 6) Andersson, M. A., Mikkola, R., Helin, J., Andersson, M. C., Salkinoja-Salonen, M. A novel sensitive bioassay for detection of Bacillus cereus emetic toxin and related depsipeptide ionophores. Appl. Environ. Microbiol., 64, (1998). 7) Finlay, W. J. J., Logan, N. A., Sutherland, A. D. Semiautomated metabolic staining assay for Bacillus cereus emetic toxin. Appl. Environ. Microbiol., 65, (1999). 8) Agata, N., Ohta, M., Yokoyama, K. Production of Bacillus cereus emetic toxin (cereulide) in various foods. Int. J. Food Microbiol., 73, (2002). 9) Häggblom, M. M., Apetroaie, C., Andersson, M. A., Salkinoja-Salonen, M. S. Quantitative analysis of cereulide, the emetic toxin of Bacillus cereus, produced under various conditions. Appl. Environ. Microbiol., 68, (2002). 10) Chiba, T., Akiba, T., Ibe, A., Arai, T., Ikeuchi, Y., Shibata, M., Yanagawa, Y., Yano, K., Morozumi, S. Study on LC-MS assay for Bacillus cereus emetic toxin. Jpn. J. food microbiol., 23, (2006). 11) Shaheen, R., Andersson, M. A., Apetroaie, C., Schulz, A., Ehling-Schulz, M., Ollilainen, V. M., Salkinoja- Salonen, M. S. Potential of selected infant food formulas for production of Bacillus cereus emetic toxin, cereulide. Int. J. Food Microbiol., 107, (2006). 12) Rau, J., Perz, R., Klittich, G., Contzen, M. Cereulide forming presumptive Bacillus cereus strains from fooddi#erentiating analyses using cultural methods, LC-MS/MS, PCR, and infrared spectroscopy in consideration of thermotolerant isolates. Berl Munch Tierarztl Wochenschr., 122, (2009). 13) Bauer, T., Stark, T., Hofmann, T., Ehling-Schulz, M. Development of a stable isotope dilution analysis for the quantification of the Bacillus cereus toxin cereulide in foods. J. Agric. Food Chem., 58, (2010). 14) Biesta-Peters, E. G., Reij, M. W., Blaauw, R. H., In t Veld, P. H., Rajkovic, A., Ehling-Schulz, M., Abee, T. Quantification of the emetic toxin cereulide in food products by liquid chromatography-mass spectrometry using synthetic cereulide as a standard. Appl. Environ. Microbiol., 76, (2010). 15) , p (ISBN ) 16) Currie, L. A. Nomenclature in evaluation of analytical methods including detection and quantification capabilities. Pure & Appl. Chem., 67, (1995).