Nanoelectrospray with ion-trap mass spectrometry for the determination of beta-casomorphins in derived milk products.
Beta-casomorphins (b-CMs) are bioactive peptides derived from casein with opioid agonist effects similar to morphine. The use of electrospray (ESI) with quadrupole ion-trap mass spectrometry (QIT-MS) for these compounds in two matrices, cheese and milk, was examined. It was compared to a liquid chromatography (LC) coupled to mass spectrometry (LC-MS), and a "soft" ionisation technique, NanoMate, with selected ion monitoring (SIM), which are unreliable for the determination of trace casomorphins in derived milk products. b-CM mass fragmentation pathways were done for the four most common b-CMs: beta-casomorphin (1-5) bovine (b-CM-5), beta-casomorphin (1-7) bovine (b-CM-7), [D-Ala2, D-Pro4,Tyr5]-beta-casomorphin (1-5) amide (b-CM-10) and beta-casomorphin (1-5) amide [D-Ala2,Hyp4,Tyr5] (b-CM-11). The major product ions obtained in QIT-MS were used to construct fragmentation pathways for b-CMs. The different collision energies using automated nanoelectrospray ion source NanoMate and conventional LC in QIT-MS were studied. Calibration data for b-CMs, using spiked milk or cheese samples (10 g or 10 mL), were: NanoMate/MS (25-1000 microg/L), r(2)=0.998; NanoMate/MS(2) (5-1000 microg/L), r(2)=0.9992; NanoMate/MS(3) (2.5-1000 microg/L), r(2)=0.9998. Reproducibility data (% RSD, N=5) for NanoMate/MS(n) mode ranged between 2.0 at 500 microg/L and 7.0 at 10 microg/L.
Laboratori de Bromatologia i Toxicologia, Facultat de Farmàcia, Universitat de València, 46100 Burjassot, València, Spain. ana.juan@uv.es
Ana
A
Juan-García
Guillermina
G
Font
Cristina
C
Juan
Yolanda
Y
Picó
D000818:Animals; D002417:Cattle; D002611:Cheese / Q000032:analysis; D002853:Chromatography, Liquid; D003611:Dairy Products / Q000032:analysis*; D004723:Endorphins / Q000032:analysis* / Q000737:chemistry; D013058:Mass Spectrometry / Q000379:methods; D008892:Milk / Q000737:chemistry; D015394:Molecular Structure; D036103:Nanotechnology / Q000379:methods*; D015203:Reproducibility of Results; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D013237:Stereoisomerism
D004723:Endorphins; C021968:beta-casomorphins