Nitrate levels in domestic vegetables from local markets were determined by high performance liquid chromatography. The nitrate level of spinach harvested in the summer is significantly higher than that harvested in the winter. On the contrary, the nitrate levels of lettuce, sunny lettuce, and daikon radish harvested in the summer are significantly lower than those harvested in the winter. We then estimated the nitrate level contained in 59 commercial processed foods. The nitrate levels of these products are as follows: Juice (n=15), 5.9〜652.5 μg/mL; soup (n=13), 12.1〜437.9 μg/mL; paste (n=3), 46.1〜888.8 μg/mL; tablet (n=13), 4.0〜1373.5 μg/g; powder (n=6), 37.1〜309.7 μg/g; confectionery (n=5), 3.1〜72.6 μg/g; flaked seasoning (n=2), 699.2〜1147.4 μg/g; pasta (n=2), 36.9〜45.6 μg/g. An excessive intake of these foods causes an excess in the acceptable daily intake of nitrate recommended by the Joint FAO/WHO Expert Committee on Food Additives. We believe that this important information about nitrate intake is needed for preventing such health hazards.

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An analytical method for the measurement of bisphenol A (BPA) and related compounds (BPAs) such as bisphenol B (BPB), bisphenol E (BPE), bisphenol F (BPF), bisphenol P (BPP) and bis(4-hydroxyphenyl) sulfone (TDP), in food can samples was improved using stir bar sorptive extraction (SBSE) with in situ derivatization(acetylation) followed by thermal desorption (TDS)-gas chromatography-mass spectrometry (GC/MS). The method indicates good linearity and the correlation coefficients (>0.99) in the range of 0.4-40 ng/mL. Using the acetylated-SBSE-TDS-GC/MS method, BPA in the canned food being marketed by the food maker in Japan was analyzed. As the results, BPA was detected between 0.3-2.8 μg in four cans among seven canned foods tested. Especially, the content of the asparagus canned food was high level as compared with other canned food. Therefore, further analysis was performed with 5 asparagus canned foods. BPA was detected with all asparagus canned food at the range from 0.9 to 19.1 μg. The amount of BPA in these canned foods was evaluated within 5% compared with TDI (10 μg/kg/day by EU SCF). On the other hand, BPAs were also detected in 2 asparagus canned foods not only liquid part but also edible part. However, BPB, BPE, BPP and TDP were not detected in the extract sample from can coating materials. The possibility of food concentration by BPAs was suspected at the stage of the processing before being filled to the canned food. These results suggests that this derivatization (acetylation) SBSE-TDS-GC/MS method can be used in the determination of the BPA and related compounds with which processed food is comtaminated.

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In order to set official analytical method in foods, the method of determining polysorbates(PSs) with rapid screening test by TLC and colorimetric assay were developed. PSs were extracted from processed foods with acetonitrile containing methanol. The extract was cleaned up on an alumina column (aluminum oxide, basic, 10g) and a silica gel cartridge (Sep-Pak Plus Silica, 690mg) to remove food color and other interfering substance. Suitable conditions of TLC to determine PS were as follow: adsorbent, silica gel ; developing solvent, dichloromethane -methanol -acetone -water (100 : 20 : 15 : 3) mixture; color development, Dragendorff reagent. The content of PS was obtained by colorimetric assay - cobalt thiocyanate method with PS80 as a standard substance. The recoveries of PS80 from eleven kinds of foods fortified at the level of 0.1 g/kg were 48.8-76.2% except 24.6% for a freezed dry food. The proposed method was applied to cocoa mix containg PS60. PS was confirmed at 0.26g/kg as PS80.

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In our previous study, we reported a rapid screening test method of polysorbates (PSs) using TLC. Although the method is useful in terms of obtaining characteristic spot pattern of PSs, it is impossible to discriminate each polysorbate (PS20, 40, 60, 80, 65 or 85) and to identify the molecular species in PSs. Thus we developed a new qualitative analytical method of PSs using LC/MS. PSs were separated on a YMC pack C8 column (150 mm × 2.0 mm I.D., 5 μm, 30 nm) by a gradient elution with a mixture of water-methanol containing 0.1% formic acid. PSs were analyzed in selected ion monitoring (SIM) mode, with Na⁺ adducts produced by electrospray ionization. Selected ion was calculated from the molecule consisting of Na⁺ adducts of 20 oxyethylene (EO) sorbitan (So) mono-, di-, or tri-ester of fatty acids (FA) (So-EO(20)-FA(1〜3)), respectively. the SIM peak of each PS was eluted at different retention time by constituent FA and esterification degree of PS and the PS with different length of EO (12〜35) was found in each SIM peak. Using the method we tried to identify the molecular species in the spots obtained by TLC analysis of PS40. Two major spots of TLC prepared by preparative thin layer chromatography (PTLC) were revealed to contain So-EO(20)-monopalmitate or So-EO(20)-dipalmitate by LC/MS. We also analyzed the extract from cocoa mix containing PS60 in SIM mode by LC/MS and found that it contained So-EO(20)-monostearate, tristearate and monopalmitate, the constituents of PS60. These results show that LC/MS analysis in SIM mode using Na⁺ adducts of So-EO(20)-FA(1〜3) as selected ions is useful not only for the analysis of compositional profile of PS itself, but for qualitative analysis of PS in food.

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