CH RO MIUM , HEX AVA LEN T: Me thod 7605, Issue 1 dated 15 M arch 200 3 - Page 4 o f 5 CALCULATIONS: 12. From the calibration graph, determine the mass of C r(VI) in e ach sam ple, W (:g), and in the average blank, B (:g). 13. Ca lculate con cen tration, C (m g/m 3), of Cr(VI) in the air volume sam pled, V (L):
NO TE : :g/L = m g/m 3
EVALUATION OF METHOD: This method was evaluated in the laboratory with spiked filters and a certified reference material containing a known loading of Cr(VI). This c ertified reference material (CRM ) is European Comm ission, Institute for Reference Materials and Measurements EC/IRMM) CRM 545, Cr(VI) and Cr(total) in welding dust loaded on a glass fiber filter [12]. This method was evaluated for extraction efficiency over the concentration range of 0.15 - 5 :g/sample testing two brands of filters, SILICAL® and G LA-5000™[3]. In these experiments, test atmospheres were no t generate d; inste ad, C r(VI) as the dichromate was fortified on the face of the sam ple filters, then 240 L of air with 35% relative humidity was pulled through at 1 L/min. A 30-day storage study using both types of filters was conducted at 1.5 :g/sample (30x LOQ) at ambient room temperature and 4 °C. The average recovery of the sto red sam ples w as 94.8% . The estim atio n of the lim it of detec tion and lim it of quantitation (LO D/LOQ ),were de term ined ana lyzing a se ries of liquid sta nda rds . The LO D and L OQ , 0.02
- g/sample and 0.07 :g/sa m ple respe ctively were ca lculated by Burk art's m etho d [13].
To fully evalua te this m etho d, a field-stud y was con duc ted in w hich side-by-side sam ples were tak en to m easure exposures to Cr(VI) during spray-painting and electroplating operations. Th ese sam ples were analyzed subsequently by 4 different methods (NIOSH Method 760 5, 7703, 7300 and OS HA ID-215) [1 ]. NIOSH m etho d 73 00 w as u sed to measure total chromium. The results from the other 3 methods correlated very well showing no statistical difference among the 3 methods. Recoveries of 98.4 (+ 3.4) % were obtained for C RM 545 (n = 6) [2].
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NIOSH Manual of Analytical Methods (NMAM), Fourth Edition
