PENTAMIDINE ISETHIONATE: METHOD 5032, Issue 2, dated 15 August 1994 - Page 4 of 4 CALCULATIONS: 18.
19.
Determine the mass, ng (corrected for R), of pentamidine isethionate found on the filter (W f), on the average media blank (B f), and the mass, ng, of pentamidine isethionate found on the interior surface of the cassette filter holder (W c) and on the interior surface of a blank cassette filter holder (B c). Calculate concentration, C, of pentamidine isethionate in the air volume sampled, V (L):
EVALUATION OF METHOD: Average recoveries after fortification of 37-mm PVC membrane filters with 50-, 99.9-, 300-, and 8816-ng quantities of pentamidine isethionate were 0.76, 0.81, 0.84, and 0.91, respectively; precision ( Sr) was 0.065 (24 samples, pooled). The average recovery of 324-ng quantities of pentamidine isethionate from PVC filters after 27 days of storage at room temperature in the dark was 0.97; s r was 0.045 (6 samples). This method was not evaluated with generated atmospheres in a laboratory. However, the method was employed for measurement of pentamidine isethionate in air in a hospital [1]. Significant quantities [10 3,810 ng (3 - 11% of the totals)] of pentamidine isethionate were found on interior surfaces of the front pieces of eight cassette filter holders. The LOD of pentamidine isethionate in solution was 7 ng per 3 mL. According to a curve of average recovery of pentamidine isethionate from PVC filters versus average concentration in solution, a conservative estimate of recovery was 0.40 when the concentration in solution was at the LOD. Thus, the LOD for pentamidine isethionate on a PVC filter was 18 ng (7 ng divided by 0.4). The LOQ for pentamidine isethionate on a PVC filter (50 ng) was the lowest level at which recovery was acceptable (>75%). The LOD and LOQ for pentamidine isethionate on the interior surface of the front piece of a cassette filter holder were 7 and 24 ng, respectively. A standard solution of pentamidine isethionate in eluent at a concentration of 100 ng/mL was stable for a period of more than 3 months during storage at 0 °C in the dark. Smith states that for killing wet and dry tuberculosis bacteria, 95% ethanol and 50% ethanol, respectively, are most active . Also, perhaps 70% ethanol would be the best single solution for all purposes [4]. However, injection of a solution of pentamidine isethionate in 70% ethanol resulted in poor chromatography. Consequently, a 50% ethanol solution was selected for recovery of pentamidine isethionate from PVC filters.
REFERENCES: [1] Tucker, S.P., B.R. Belinky, T.A. Seitz, and G.D. Foley, American Industrial Hygiene Association Journal 54 (10), 628-632 (1993). [2] Lin, J. M.-H., R. J. Shi, and E. T. Lin, Journal of Liquid Chromatography , 9 (9), 2035-2046 (1986). [3] Biosafety in Microbiological and Biomedical Laboratories, 2nd ed., Appendix A, U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and National Institutes of Health, Washington, D.C. (1988); HHS Publication No. (NIH) 88-8395. [4] Smith, C. R. Public Health Reports (U.S.), 62, 1285-1295 (1947). METHOD WRITTEN BY: Samuel P. Tucker, Ph.D., NIOSH/DPSE. NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94
