A simple and rapid method was developed for the screening of 82 pesticides/metabolites in a wide variety of crops, using solid-phase extraction and liquid chromatography with tandem mass spectrometry (LC/MS/MS). After extraction with methanol, the filtered extracts were made up to 100 mL and a 2 mL aliquot was subjected to solid-phase extraction. Co-extractives were removed with a C18 mini-column, while pesticides were retained on 3 kinds of mini-columns (HLB, SAX, activated carbon), and then eluted with acetonitrile. Analysis was performed by LC/MS/MS, and MS acquisition parameters were established in positive and negative ESI modes. The utility of the method was demonstrated by the analysis of 6 crops (carrot, cabbage, onion, spinach, lemon, brown rice) and one mixed vegetable juice. Of 82 compounds tested, 75 in carrot and 62 in lemon were obtained with recoveries ranging from 70-120%. For all samples tested, 75 compounds could be obtained with recoveries of over 50%, and the detection limits of most compounds were lower than 0.01 μg/g. This method provides acceptable performance for analysis of these 75 compounds. Further, by using aliquots of the extracts with small-scale mini-columns, purified samples could be obtained. This proposed method with small matrix effects, is effective and suitable for screening of multiple residual pesticides by using LC/MS/MS.
Jojoba wax is a natural gum base used as a food additive in Japan, and is obtained from jojoba oil with a characteristically high melting point. Although the constituents of jojoba oil have been reported, the quality of jojoba wax used as a food additive has not yet been clarified. In order to evaluate its quality as a food additive and to obtain basic information useful for setting official standards, we investigated the constituents and their concentrations in jojoba wax. LC/MS analysis of the jojoba wax showed six peaks with [M+H]+ ions in the range from m/z 533.6 to 673.7 at intervals of m/z 28. After isolation of the components of the four main peaks by preparative LC/MS, the fatty acid and long chain alcohol moieties of the wax esters were analyzed by methanolysis and hydrolysis, followed by GC/MS. The results indicated that the main constituents in jojoba wax were various kinds of wax esters, namely eicosenyl octadecenoate (C20 : 1-C18 : 1) (I), eicosenyl eicosenoate (C20 : 1-C20 : 1) (II), docosenyl eicosenoate (C22 : 1-C20 : 1) (III), eicosenyl docosenoate (C20 : 1-C22 : 1) (IV) and tetracosenyl eiosenoate (C24 : 1-C20 : 1) (V). To confirm and quantify the wax esters in jojoba wax directly, LC/MS/MS analysis was performed. The product ions corresponding to the fatty acid moieties of the wax esters were observed, and by using the product ions derived from the protonated molecular ions of wax esters the fatty acid moieties were identified by MRM analysis. The concentrations of the wax esters I, II and III, in jojoba wax were 5.5, 21.4 and 37.8%, respectively. In summary, we clarified the main constituents of jojoba wax and quantified the molecular species of the wax esters without hydrolysis by monitoring their product ions, using a LC/MS/MS system.
Fungi growing on domestic rice were examined from April to June, 2003. One hundred samples of rice, which had been harvested in the autumn of 2002, were collected from the local market, and 15 samples of stored rice, which had been harvested in 2001 and stored in warehouses under government control, were used as samples. From each sample, 50 grains (100 grains in total) were plated on potato-dextrose agar (PDA) and malt yeast 40% sucrose agar (M40YA) containing chloramphenicol after being washed with sterile distilled water to remove any microorganisms on the surface, and incubated at 25°C for a week. For most of the rice samples harvested in the preceding year, the proportion of grains infected with fungi was less than 20% of the total grains tested. In about half the samples of rice stored for one and half years, more than 80% of the grains were infected with fungi that grew on M40YA. The major genera of fungi isolated from the rice harvested in the preceding year were Penicillium and Alternaria, and those from the rice stored for one and a half years were Aspergillus, Penicillium and Eurotium. P. islandicum, A. versicolor, A. ochraceus and others were isolated as possible mycotoxin-producers in the mycoflora of domestic rice. P. islandicum was isolated from 3 samples, and 82% of the grains were infected with this fungus in one sample. All three isolates from these samples appeared to produce luteoskyrin on Czapek yeast extract agar, based on TLC and HPLC analysis.
Tabletop dry ice coolers (three types; dome model, cap model and tripod model), which are used in kitchens and hotel banquet halls to refrigerate fresh seafood, were investigated to determine whether growth of Vibrio parahaemolyticus was inhibited by their use. On TSA plates containing 1.8% NaCl and fresh seafood (fillets of squid, pink shrimp and yellowtail), V. parahaemolyticus (O3 : K6, TDH+) inoculated at 4 to 5 log CFU/sample and left at ambient temperature (25°C) grew by 1.0 to 2.8 orders in 4 hours. In contrast, with tabletop coolers no significant increase in viable count occurred in 3 to 4 hours, confirming that tabletop coolers inhibited the growth of V. parahaemolyticus. The temperature in each tabletop cooler was kept below 10°C for 80 to 135 min, though the CO2 gas concentration in them remained high for only a short time (0 to 75 min). It was presumed that the refrigeration function mainly contributed to growth inhibition. Our results indicate that tabletop dry ice coolers are helpful for prevention of food-borne disease due to V. parahaemolyticus in food-service locations, such as kitchens and banquet halls.
Formaldehyde (FA), acetaldehyde (AA) and oligomers in recycled polyethylene terephthalate (PET) were analyzed by HPLC. All of the physically recycled PET contained detectable levels of FA, AA and oligomers, and the levels were almost the same as in used bottles. Most superclean-like and chemically recycled PET contained lower levels than new pellets. These compounds showed no decrease upon physical recycling, but showed a marked decrease upon superclean-like recycling. In PET sheets made using physically recycled PET, FA was decreased, though AA was increased by the sheeting process as same as new one. FA, AA and oligomers originated from PET resin and their levels in recycled products were almost equivalent to those in new products. It was concluded that there is no particular safety concern about their presence in recycled PET.
To validate a modified version of AOAC official method of analysis 995.10 as an official standard in Japan for determination of patulin in apple juice, an inter-laboratory study was performed in 11 laboratories using a non-contaminated sample, 2 naturally contaminated samples and 2 spiked samples of apple juice. For naturally contaminated apple juices, the relative standard deviations for repeatability and reproducibility were 3.2, 7.1% and 10.0, 21.7%, respectively. HORRAT values were 0.4, 0.9. The average recovery of patulin from spiked sample was 83.7%. The limit of quantification was calculated as 10 μg/kg. From these results, the method was thought to be suitable as an official standard for determination of patulin in apple juice in Japan.
Suitable liquid chromatography/mass spetrometry (LC/MS) conditions were examined for Amaranth, Red 2G (R2G), Azo Rubine (Azo), Fast Red E (FRE) and Brilliant Blue FCF, which were detected in Akasu, a red vinegar made in Hong Kong from sake lees, on both thin layer chromatography (TLC) and photodiode array high-performance liquid chromatography (PDA-HPLC). Molecular-related ions for each dye were detected with excellent sensitivity by LC/MS using electro-spray ionization with negative ion mode, capillary voltage 3.00 kV, cone voltage 50 V and desolvation temperature 400°C. LC/MS analysis of refined Akasu under these conditions enabled us to obtain clear mass spectra of R2G, Azo and FRE, which were present at trace levels in the Akasu. The results were consistent with those from TLC and PDA-HPLC. These experiments suggested that LC/MS analysis is applicable for confirmation of dyes in food.