Sukeji Suzuki

Determination of lycopene, α-carotene and β-carotene in serum by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry with selected-ion monitoring

Abstract A selected-ion monitoring (SIM) determination of serum lycopene, α-carotene and β-carotene by an atmospheric pressure chemical ionization mass spectrometry (APCI–MS) was developed. A large amount of serum cholesterols disturbed the SIM determination of carotenoids by contaminating the segment of interface with the LC–MS. Therefore, separation of carotenoids from the cholesterols was performed using a mixed solution of methanol and acetonitrile (70:30) as the mobile phase on a C 18 column of mightsil ODS-5 (75 mm×4.6 mm I.D.). The SIM determination was carried out by introducing only the peak portions of carotenoids and I.S. (squalene) by means of an auto switching valve. In the positive mode of APCI–MS, lycopene, α-carotene and β-carotene were monitored at m / z 537 and I.S. was monitored at m / z 411. This method was linear for all analytes in the range of 15–150 ng for lycopene, 7–70 ng for α-carotene and 25–50 ng for β-carotene. The detection limit of LC–APCI–MS-SIM for carotenoids was about 3 ng per 1 ml of serum ( S / N =3). The repeatabilities, expressed as C.V.s, were 10%, 8.4% and 5.3% for lycopene, α-carotene and β-carotene, respectively. The intermediate precisions, expressed as C.V.s, were 11. 2%, 8.8% and 6.5% for lycopene, α-carotene and β-carotene, respectively.

Determination of Medium-Chain Triglycerides in Flavor Preparations by GC and GC/CI-MS

A simple GC method was established for the determination of medium-chain triglycerides (MCT) in flavor preparations. GC peaks were confirmed by GC/CI-MS. Pseudo-ion peaks of [M+1]+ were not observed in the mass spectra of GC peaks of MCT, whereas fragment ion peaks of [MH-RCOOH]+ were observed. Out of 5 flavor preparations labelled as containing edible oils or vegetable oils, MCT were found in 4.

On the Atomic Absorption Determination of Arsenic

Analytical optimum condition for the determination of arsenic by introducing arsine into an atomic absorption spectrophotometer system equipped with an argon-hydrogen flame was examined. The optimum concentrations of reagents in the prepared solution were 3-5N hydrochloric acid, 0.5-2.0% potassium iodide and 0.1-1.0% stannous chloride. The addition of 0.8-2.0g of zinc powder to 20ml of prepared solution was enough to obtain the highest absorbance of arsenic under 0.5kg/cm2 of arsine gas pressure. The absorbance of arsenic was decreased according to the acidity raised by sulfuric acid residue in prepared solution, but recovered by neutralization with ammonia water. The absorbance was interfered with over 5μg of Se4+ and over 500μg of Sb3+ added to the 20ml of prepared solution containing 1μg of arsenic.