[Enhancement of Pesticide Peak Response in GC-MS in the Presence of Multiple Co-Existing Reference Pesticides].

We carried out a collaborative study in six laboratories to confirm the universality of the enhancing effect of co-existing reference pesticides on the GC-MS peak response to a target pesticide (malathion, procymidone, or flucythrinate). First, we confirmed the response enhancement of the target pesticides with increasing numbers of co-existing reference pesticides in solution. Then, using diluted green soybean matrix, we analyzed the target pesticides with two types of matrix-matched calibration, containing the target pesticides or 166 other pesticides. In both cases, the response-enhancing effect of co-existing pesticides was confirmed in all laboratories. The enhancement was reduced by addition of green soybean matrix to the sample and calibration solutions. Our results show that it is necessary to estimate the peak response-enhancing effect of co-existing pesticides in the calibration solution to obtain accurate results with GC-MS determination. The enhancing effect could be reduced by addition of food matrix to the sample and calibration solutions.

[Simultaneous analysis of residual pesticides in fruit, vegetables, brown rice, and oolong tea by LC-MS/MS].

According to "The validity evaluation guideline of the testing methodology on the residual pesticides in food" of the Ministry of Health, Labour and Welfare of Japan, we carried out validity evaluation of a simultaneous analysis method for residual pesticides in various products with the QuEChERS method using a C18 mini column and/or an EnviCarb/PSA mini column for purification. Multi-ingredient simultaneous analysis with high sensitivity in a short time was achieved with LC-MS/MS. Validation was achieved for 269 pesticides among 302 pesticides in eight kinds of fruit, vegetables, and brown rice and 204 pesticides among 233 pesticides in oolong tea. Finally, 151 pesticides in oolong tea and from 234 to 259 pesticides in fruit, vegetables, and brown rice met the values specified in the guideline.

Monitoring of radioactive substances in foods distributed in Kyoto, Japan (1991-2011). - Comparison of detection rates and concentrations before and after the Fukushima Daiichi Nuclear Power Plant accident - .

Since the Chernobyl Nuclear Power Plant accident, radioactive substances have been continually monitored in foods collected in the city of Kyoto, Japan. The importance of the monitoring was increased by the Fukushima Daiichi Nuclear Power Plant accident in March 2011. Here, the detection rates and concentrations of radioactive substances were compared among food samples collected before and after the accident in Fukushima prefecture. Before the accident, (137)Cs was the only radioactive substance detected in foods. The detection rate was 70% for fish and shellfish samples and the highest concentration was 1.7 Bq/kg. It was also 83% for fresh mushroom samples and the highest concentration was 7.5 Bq/kg. In contrast, the detection rate was low for vegetables and the concentrations were also lower than those of the above samples. On the other hand, after the accident, (131)I was detected in food produced in the Tohoku and Kanto areas. Actually, (131)I (3,400 Bq/kg), (134)Cs (280 Bq/kg), and (137)Cs (280 Bq/kg) were detected in mizuna, a leaf vegetable, on March 23, 2011. These radioactive substances were detected in all leaf vegetable samples examined in March and April 2011, but they were not detected in samples examined in November 2011. (131)I was not detected in any food sample examined after May 2011. However, (137)Cs (average=7.9 Bq/kg) was consistently detected in fish and shellfish samples until November, although the concentrations were less than the regulatory limits. It appears unlikely that foods containing radioactive substances over the regulatory limits are currently being distributed in Kyoto.