RESUMO
An atmospheric pressure chemical ionization mass spectrometry (APCI-MS) method was developed for the direct analysis of triglycerides in edible oils.The edible oil sample was dissolved in acetonitrile.Under the optimal conditions such as positive ion detection,800 μL/h of sample flow rate,250℃ of vaporizer temperature and 5000 nA of corona needle current,the repeatability (RSD) of peak intensity rate of m/z 857.76 to m/z 881.76 was less than 5％.Then,different kinds of oil from different manufacturers were analyzed by the proposed method.After a principal component analysis for the analytical results,the peak intensity rate of m/z 857.76 and m/z 881.76 was selected for oil identification.The adulteration of 5％ lard in corn oil could be recognized directly using the peak intensity rate.Three characteristic triglycerides in edible oil were preliminarily identified by collision induced dissociation (CID) experiments.The method was applied to analyze the swill oil and fried oil samples,and the results showed that the swill oil contained both vegetable oil and animal fat,and the fried oil was also different with commercial vegetable oil.
RESUMO
The ionic liquid butylamine 2,5-dihydroxybenzoate (DHB-BuN) was chosen as the matrix for improving repeatability of oligosaccharides quantitation, and imaging oligosaccharides in soybean and leaf by matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS).Using the ionic liquid matrix methanol solution (20%, V/V) to cover sample slice, and setting MS acquisition parameters including polarity as positive and laser power as 70%, the MS imaging experiment was performed to analyze oligosaccharides and their distribution in soyben and soybean leaf.As a result, the MALDI-MS analysis of 3 kinds of oligosaccharides including sucrose, raffinose and stachyose was performed using the ionic liquid matrix and the reproducibility RSDs were less than 3% for in-spot and less than 4% for spot-to-spot.The standard curves linear correlation coefficients (R2) were all no less than 0.996 between MS peak intensity and oligosaccharides concentraions in the concentration rage of 0.062-1.00 mg/mL, which showed quantitative power in MALDI-MS analysis.The matrix was used for MALDI-MS imaging analysis of soybean chips and soybean leaf surface disaccharide, trisaccharide and tetrasaccharide to obtain the soybean mass spectrum and spatial resolution of 150 μm of the three oligosaccharides imaging.Three kinds of oligosaccharides in the soybean roughly balanced distribution, and the oligosaccharides distribution in the leave was mostly at its tip part.The contents of the 3 kinds of oligosaccharides could be estimated by their MS peak intensity and above standard curve.The result suggested that the ionic liquid DHB-BuN matrix could be well applied in MALDI-MS imaging analysis of oligosaccharides in different sample.