A simultaneous method using liquid chromatography coupled with electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) was developed for the determination of pesticide residues in crops. Mass spectral acquisition was performed in the positive mode by applying multiple reaction monitoring. In LC separation, an Atlantis dC18 Column was used with acetic acid-ammonium acetate-acetonitrile as the mobile phase. Pesticide residues in crops were extracted with acetone, and cleaned up by liquid-liquid separation with saturated salt solution and hexane, followed by an ENVI-Carb cartridge. The quantification limits of compounds in crops were below 5 ng/g. Eighty compounds were obtained with recoveries ranging from 60 to 130% at the level of 50 ng/g with RSD (%) of less than 15%. Fifty crop samples were analyzed by the developed method. Seven pesticide residues were detected in nine crops.
A screening method is described for determining 200 pesticides, except dimethipin, divided into four groups by means of gas chromatography/tandem mass spectrometry (GC/MS/MS) using an ion trap mass spectrometer equipped with automated gain control (AGC). The quantitation limit for 194 pesticides was 0.01 mg/kg on a crop basis, except for allidochlor, dimethoate, hexythiazox, methamidophos and triadimenol. The calibration curve of each pesticide was linear in the range of 0.04-5.0 μg/mL. One hundred and ninety-nine pesticides were added to matrix of potato, spinach, cabbage, apple, orange, soybean and unpolished rice at twice the limits of quantitation. The recoveries of 194 pesticides from all crops were satisfactory (50-150%) for screening purposes. Although some pesticides in apple and orange were not determined by selected ion monitoring (SIM) analysis at the limits of quantitation, all of them were identified by ion-trap GC/MS/MS at the same concentration. Thus, the ion trap GC/MS/MS technique is useful for the screening of residual pesticides present at low levels in agricultural products.
The Japanese Government has prohibited the use of seafood protein, as well as mammalian protein, in ruminant feed. There is an official method to detect meat and bone meal, but no method is yet available to detect fishmeal in ruminant feed. We tried to develop a suitable method to detect fishmeal in ruminant feed, similar to the official method “PCR detection of animal-derived DNA in feed”. Our previously reported primers (fishcon5 and fishcon3-1) showed low sensitivity, so we designed new primers based on a DNA sequence from yellowfin tuna mitchondrial DNA. Among the primers, FM5 and FM3 specifically detected fish DNA (sardine, yellowfin tuna, skipjack tuna, chub mackerel, Pacific saury, salmon, rainbow trout, Japanese anchovy, codfish and Japanese horse mackerel) from fish meat, and did not amplify DNA from animals and plants. The sensitivity for detection of the presence of fishmeal in ruminant feed was 0.01-0.001%.
The applicability of GC, GC/MS and liquid chromatography with tandem mass spectrometry (LC/MS/MS) to screening for 140 pesticides in agricultural products was examined. Validation of multi-residue screening methods for the determination of 88 pesticides in 12 crops (asparagus, cauliflower, burdock, carrot, broccoli, spinach, matsutake mushroom, orange, soybean, sesame, millet and tea) was done by GC and GC/MS. Of the 88 pesticides, 63 were obtained with recoveries in the range from 50 to 150% at the 0.1 μg/g level in the 12 crops. Applicability of the official methods in Japan to 74 pesticides, including 22 pesticides with low recovery (<50%) by GC or GC/MS analysis, was also examined by LC/MS/MS. LC/MS/MS acquisition parameters were established for 67 pesticides in positive and negative electrospray ionization (ESI) modes. Of 67 pesticides validated in 7 crops using LC/MS/MS at the 0.1 μg/g level, 44 showed recoveries in the range from 50 to 150%. The occurrence of matrix interference in LC/MS/MS can lead to false-positive detection of MCPA in spinach, cabbage and orange and false-negative detection of four pesticides in orange, spinach, apple and unpolished rice. Good linearity was observed in the studied ranges by GC, GC/MS (r>0.990) and LC/MS/MS (r>0.995). Of the total of 140 pesticides validated by GC, GC/MS and LC/MS/MS, 107 were newly recognized as suitable subjects for screening.
The infrared absorption (IR) spectrum is often used as a standard reference in identification tests of food additives in Japan. In the case of betaine, many different IR spectra have been reported and, therefore, it is necessary to establish an IR spectrum that is reproducible and reliable enough to be used as a standard for identification. In the present study, suitable conditions to obtain a standard IR spectrum were examined from various viewpoints, including pretreatment, selection of method, and measuring technique. The KBr disk method, which has generally been used to identify betaine, was found to be humidity-dependent, and there was also an interaction between betaine and KBr. A reproducible IR spectrum suitable as a standard could be obtained by drying betaine at 105°C for 3 hours over phosphorus pentoxide, and then measuring the IR spectrum by the liquid paraffin (Nujol) paste method.
Accidents caused by the bursting of capped PET bottles with leftover contents have increased in Japan. Therefore, the bursting risk of capped PET bottles with leftover contents was investigated. The ratios of distension, after 10 days at 25°C, of capped PET bottles with leftover orange juice were approx. 70% in the case of drinking while eating Kimuchi, and approx. 6% in the case of drinking but not eating. Among 58 distended bottles, none burst spontaneously, but 4 bottles (6.9%) burst upon physical shock (dropping onto a concrete floor from 1.5 m height). The greatest distensions of capped PET bottles were observed with leftover orange juice, apple juice and soured milk after 10 days at 25°C. No distensions were observed in bottles containing leftover sports drink and green tea under the same conditions. Identified organisms from distended bottles were almost all Candida spp. When those Candida spp. strains were inoculated individually into PET bottles half full of orange, apple or sour milk, all bottles were distended after 7 days at 25°C. From the above results, it appears that there is a risk that capped PET bottles with leftover contents, especially sour fruit juice or soured milk, may burst owing to high gas pressure caused by yeast growth during storage at room temperature for over 1 week.