CORESTA Agrochemicals Analysis Sub-Group response to ISO Resolution No. 94 (2018)

 

To: ISO

From: CORESTA Agrochemicals Analysis Sub-Group

CORESTA Ref: AA-196-CXP

Date: 12 October, 2018

Subject: The current work of CORESTA Agrochemicals Analysis Sub-Group (AA-SG) in response to ISO Resolution No. 94 on maleic hydrazide (MH)

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Resolution No 94: ISO 4876:1980 “Tobacco and tobacco products - Determination of maleic hydrazide residues”

ISO/TC 126/SC 2 mentions the Resolution No: 88 of the 19th meeting of SC 2* and decides to wait for the work of CORESTA Agrochemicals Analysis Sub-Group prior to initiate a new work item proposal.

ISO/TC 126/SC2, Bordeaux, France, May 2018

 

*Resolution No 88: ISO 4876:1980 Tobacco and tobacco products - Determination of maleic hydrazide residues

ISO/TC 126/SC 2 decides to wait for the clarification of the work of CORESTA Agrochemicals Analysis Sub-Group before considering the initiation of a new work item proposal.

ISO/TC 126/SC2, Osaka, Japan, October 2016

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Current CORESTA AA-SG activities

2015  (54th meeting in Zimbabwe)

Due to the complexity of the distribution of maleic hydrazide (MH) throughout the tobacco plant, the AA-SG decided to conduct a Joint Experiment Technical Study (JETS) to assess how to analyze it correctly. JETS 16/2 was planned as a mini-proficiency test to evaluate the capacity of different methods to properly measure MH content in both artificially spiked and naturally incurred tobacco samples.

2016  (55th meeting in Thailand)

The results of the JETS 16/2 were shown and reviewed. AA-SG members focused on YC/T method (China) and Renaud method (Brazil). The obtained results showed some indications that the YC/T method, which had been already submitted to ISO as a possible replacement to the current ISO method, had a better ability to detect residues in both spiked and incurred samples than the other methods evaluated. However, the limited number of laboratories applying the same method weakened the statistical analysis in achieving conclusive findings. In order to get conclusive findings, another JETS (JETS 17/1) with a larger number of participating laboratories applying the YC/T method was strongly recommended.

2017  (56th meeting in Argentina)

JETS 17/1 compared the current ISO method to the YC/T method. The results of the JETS were shown and discussed. A statistical comparison of the ISO method results and the YC/T method was done, but it showed that the results were not comparable. It was noted that the analytical results with the YC/T methods were lower than those with the ISO method in incurred samples. Therefore, this result might indicate that the ISO method can extract both free and bound MH, but YC/T method cannot extract bound MH.

2018  (57th meeting in Sweden)

Japan Tobacco Inc. conducted a tobacco plant metabolism study with 14C-MH to identify and characterize the profile of MH and its metabolites in a tobacco plant. The results were shared and discussed.

  • From the fresh and cured samples treated with 14C-MH, radioactive compounds were extracted using a methanol/water extraction, and further extracted using the current ISO and the YC/T methods separately.
  • When results for all three extractions were compared, it was concluded that ISO and YC/T methods showed satisfactory extraction efficiencies (90.6 % and 93.8 % respectively) similar to the methanol/water method (93.8 %). However, MH metabolites determined by the methanol/water extraction were not detected by the ISO and YC/T methods. This result suggested that the MH metabolites are thought to be converted to MH via hydrolysis during the ISO and the YC/T extractions.
  • It was concluded that the target analytes were identified by the respective methods, and the YC/T method seemed comparable to ISO method in terms of extraction efficiency. Therefore, the difference of analytical results between the ISO and the YC/T method should be discussed from different angles.

Based on the above findings with 14C-MH, AA-SG members returned to the JETS 17/1 study and discussed possible additional collaborative study.

  • Considering the long history of AA-SG, history may repeat itself even though additional collaborative study would be conducted. Various Joint Experiments were conducted in 1980s in order to develop an alternative to ISO method reducing its disadvantages (low sample throughput, safety concerns related to the use of caustic reagents at a high temperature, etc.). However, the work was terminated by AA-SG without proposing any alternative.
  • It seems difficult to collect robust dataset for the statistical comparison of the YC/T method with the ISO method because many laboratories do not use ISO method due to its disadvantages, even though it is a well-validated method.
  • Furthermore, one of the possible causes why the YC/T method provided lower results than the ISO method could be that the ISO method may lack in specificity and is possibly subject to interference from tobacco constituents.
  • In conclusion, members determined that the new method, the YC/T method, did not compare to the ISO method statistically in JETS 17/1 and needed further development. In addition, it was agreed that members would compile the current findings, with their comments about the method, to submit to ISO since this is the original goal and not to develop a new method at this time.
  • AA-SG meetings can be held once a year. Besides, members have to cover laborious tasks and discuss many issues other than an alternative to ISO method. Therefore, it seems difficult to come to a conclusion on this matter in a short run. Nevertheless, further development, more evidence, and probably more appropriate evaluation approach between proposed method and ISO method are anticipated in the future.

 

Related documents

CRM 4 - Determination of Maleic Hydrazide Residues in Tobacco (September 1976)

Report - Joint Experiment Technical Study (JETS) Report 16/2 Maleic Hydrazide in Tobacco (March 2017)

Report - Joint Experiment Technical Study (JETS) Report 17/1 Maleic Hydrazide in Tobacco (July 2018)