Internal quality control (IQC) is essential to ensure the reliability of the results of chemical analysis. In this study, we propose a novel method of IQC for multiresidue analysis of pesticides. A total of seven stable isotope labeled compounds (SILC) were added to analytical samples and were used to monitor and evaluate the quality of analytical results. In contrast to conventional IQC method in which only a limited number of control materials were analyzed to ensure the reliability of the results for an entire batch, the developed method can monitor the analytical quality of all the samples in the batch. It was shown that the developed method could achieve better performance than that of conventional method. Therefore, the developed method is considered to be promising for practical applications.

(Received January 27, 2022; Accepted July 4, 2022)

This study examined the frequency of worsening clinical test values related to supplement use using a nationwide online survey, with a focus on liver function markers, and clarified the differences between outcome indices of diarrhea or skin manifestations. A nationwide online survey was conducted with 73,010 supplement users from the previous year. Of these, 221 individuals with worsening clinical test values responded to the full-scale survey. To compare surveys with different outcome indices, we used previously reported data from similar surveys.

Only 0.5% of individuals who self-reported worsening of clinical test values caused by supplement use recognized an almost certain causal relationship. Among the test items, blood lipids were the most frequently reported. The frequency of worsening liver function markers was 0.2% in supplement users. Among those who experienced worsening clinical test values, 56.1% received no treatment and 82.4% did not report the incidence of worsening clinical test values anywhere. The ingredient-based classification of products revealed more “Peptides or animal by-products” and “Combination products/not classifiable products” than those associated with other categories. Compared to the results of the survey about the experience of diarrhea or skin manifestations, those who experienced worsening clinical test values were predominantly men, frequent and long-term users, and individuals whose products could not be identified.

Few supplement users experience worsening of liver function markers, which does not seem serious. However, it is difficult for supplement users to recognize abnormal changes by themselves. Thus, it is important to record product information, usage, and changes in physical condition.

A liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based method was developed for determining quinclorac in livestock products. Quinclorac was extracted from the samples using a solution of acetone and hydrochloric acid mixed in a 99 : 1 ratio. The crude extract was purified with ethyl acetate under basic conditions, followed by quinclorac extraction with ethyl acetate under acidic conditions and analysis using LC-MS/MS. The average recoveries of quinclorac from five livestock products (n=5) fortified at the maximum residue limits or 0.01 mg/kg ranged from 85.6 to 93.5%, with the precision of repeatability ranging from 1.7 to 6.8%. The quantification limit in this analytical method was 0.01 mg/kg. These results suggest that the developed method is useful for analyzing quinclorac in livestock products.

Incidents of food poisoning associated with tetrodotoxin (TTX) contamination occur every year throughout Japan. Here, we determined TTX levels in leftover foods and serum and urine samples from eight food poisoning incidents associated with TTX contamination in Nagasaki, Japan, from 2011 to 2017.

Seven food samples associated with four of these food poisoning incidents were classified as weakly toxic (four samples), moderate-to-strongly toxic (two samples), and strongly toxic (one sample).

In comparison with previous reports, TTX was detected at harmful levels in the urine samples, but the grade of poisoning symptoms varied.

The patients’ time to maximum serum TTX levels (T_max) was estimated to be 12–24 h after ingestion of TTX-containing foods. Additionally, serum TTX levels of 19.5 ng/mL or higher within 24 h after ingestion indicated Grade 3 poisoning associated with respiratory abnormalities.

These conditions were considered indicators of severe symptoms, while TTX levels of 1–3 ng/mL relate to the onset and disappearance of symptoms. A negative correlation was found between the logarithm of serum TTX concentration and the time after ingestion for two patients, indicating that the TTX serum levels decreased logarithmically. Furthermore, the TTX serum half-lives (T_1/2) were 17.5 and 23.7 h.

The results of this study enhance our understanding of TTX food safety and contribute to TTX risk assessment.

Ciguatera fish poisoning (CFP) is recognized as the most frequent seafood poisoning due to the consumption of fish containing the principal toxins, ciguatoxins (CTXs). In Japan, CFP events have been reported annually from Okinawa and Amami Islands, locating subtropical regions. In addition, there have been reported several outbreaks due to consumption of the fish caught from the Pacific coast of the Mainland and they were often caused by the matured spotted knifejaw, Oplegnathus punctatus. As part of our research on CFP in Japan, we investigated CTXs analysis by LC-MS/MS on 176 individuals of O. punctatus (weight: 100–6,350 g, standard length: 13–60 cm) from the coast of the Mainland (Honshu, Shikoku, and Kyushu), Amami, Okinawa, and Ogasawara (Bonin) Islands. CTXs were detected from only two specimens collected from Okinawa. Total CTXs levels of the two specimens were at 0.014 and 0.040 μg/kg, respectively, exceeding FDA guidance level at 0.01 μg CTX1B equivalent/kg. However, they might be little risk of CFP because consuming over 1.5 kg of flesh is needed to develop intoxication. The toxins consisted of CTX1B analogs including CTX1B, 52-epi-54-deoxyCTX1B, CTX4A, and CTX4B, and no CTX3C analogs, supporting the finding that ciguatoxic fishes in Okinawan Waters containing only CTX1B analogs.