THIOPHANATE-METHYL in air: METHOD 5606, Issue 1, dated 15 March 2003 - Page 4 of 6
when the samples were stored at refrigerator temperatures. Calibration standards have been prepared and evaluated up to a level of 324 µg/ml. This amount equates to 648 µg/sample for field samples.
This method was developed to be used in conjunction with NMAM 5601 for the analysis of thiophanate-methyl, carbendazim, and captan. In laboratory prepared samples, it was found that the recoveries of thiophanate-methyl may decrease and those of carbendazim may increase due to chemical interactions and the decomposition of thiophanate-methyl to carbendazim [2].
NOTES:
- There are no established RELs or PELs for thiophanate-methyl. A REL of 5 mg/m³ was assumed for the sampling requirements of this analyte. This method can comfortably measure thiophanate-methyl in solution at 5 µg/mL.
- Thiophanate-methyl has an ultraviolet absorption maximum at 266 nm that may be a more appropriate wavelength for analysis. However, this method was developed to analyze several other fungicides concurrently with the thiophanate-methyl. One of these analytes has an absorption maximum at 195–200 nm, and 200 nanometers was selected as the wavelength of choice for this analysis. If it is known that the only analyte present in the sample is thiophanate-methyl, then it would be more advantageous to use a detector wavelength of 266 nm.
- The major part of this work was performed on a Phenomenex® KingSorb™ C-18, 5 µm, 250 × 2 mm column. However, a direct replacement column, the Phenomenex® Synergi™, 4 µm, Hydro-RP, 250 × 2 mm column, was suggested by the manufacturer, which would provide better separation and resolution. Retention times on the Synergi™ column are similar to those on the KingSorb™ column. (See Figures 1 & 2.) A small adjustment to the mobile phase gradient was all that was required to achieve the same separation and retention time. The Synergi™, Hydro-RP column was also able to resolve carbendazim (another fungicide included in the same overall project) from imidaclorpid, a potential interference in the field samples. The KingSorb™ column was not able to separate these two materials under any conditions that would not severely impact any of the other analytes.
REFERENCES:
1 NIOSH [1998]. Method 5601: Organonitrogen Pesticides. In: Cassinelli ME, O'Connor PF, eds. NIOSH Manual of Analytical Methods (NMAM), 4th ed, 2nd supplement. Cincinnati, OH: National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 98-119.
2 Jaycox, LB, Andrews RN [2003]. Thiophanate-methyl in Air Backup Data Report. Cincinnati, OH: National Institute for Occupational Safety and Health,Division of Applied Research and Technology (unpublished, May).
3 Lin J, Reynolds JM, Perkins JB [1996]. Backup Data Report Carbamate, Urea, and Sulfenimide Pesticides, unpublished.
AUTHORS:
Larry B. Jaycox, Ph.D., NIOSH/DART
Ronnee N. Andrews, NIOSH/DART.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition
