Page:NIOSH Manual of Analytical Methods - 5600.pdf/4

 ORGANOPHOSPHORUS PESTICIDES: METHOD 5600, Issue 1, dated 15 August 1994 - Page 4 of 20 g. h.

Prepare a graph of desorption efficiency (DE) vs. µg of analyte. Acceptable desorption criteria for 6 replicates is >75% average recovery with a standard deviation of <±9%.

MEASUREMENT: 12.

13.

Set gas chromatograph according to manufacturer’s recommendations and to conditions listed in Table 6 and on page 5600-1. Inject sample aliquot manually using solvent flush technique or with autosampler. See Table 7 for retention times of selected analytes. NOTE: If peak area is greater than the linear range of the working standards, dilute with desorbing solution or with desorbing solution (containing internal standard) and reanalyze. Apply the appropriate dilution factor in calculations. Measure peak area of analyte and of internal standard.

CALCULATIONS: 14.

15.

Determine the mass in µg (corrected for DE) of respective analyte found in the sample front (W and back (W b) sorbent sections, and in the media blank front (B f) and back (B b) sorbent sections. NOTE: The filter is combined with the front section. If W b > W f/10, report breakthrough and possible sample loss. Calculate concentration, C, of analyte in the air volume sampled, V (L):

CONFIRMATION: 16.

Whenever an analyte is detected, and its identity is uncertain, confirmation may be achieved by analysis on a second column of different polarity. If primary analysis was performed using a non-polar or weakly polar column (DB-1 or DB-5), confirmation should be accomplished by reanalysis on a polar column (DB-1701 or DB-210). See Table 7 for approximate retention times for each column type. Fewer analytes co-elute on DB-210 than on DB-1701. Relative retention times are more convenient for the identification of unknown analytes. If Parathion is not used as the retention time reference compound, then another related compound such as tributyl phosphate, Ronnel, or triphenyl phosphate may be substituted.

EVALUATION OF METHOD: This method was evaluated over the ranges specified in Table 5 at 25 °C using 240-L air samples. Sampler tubes were tested at 15% and 80% relative humidity and at 10 °C and 30 °C. In these tests, test atmospheres were not generated; instead, analytes were fortified on the face of the sampler filters. This was followed by pulling conditioned air at 1 L/min. for 4 hours. No difference in sampler performance was noted at any of these temperature/humidity combinations. Evaluations of sampler precision and stability were conducted at 30 °C and 15% relative humidity. Overall sampling and measurement precisions, bias, accuracy, and average percent recovery after long-term storage are presented in Table 5. No breakthrough was detected after 12 hours of sampling at 1 L/min with a sampler fortified with the equivalent of 4x the NIOSH REL. Malathion and Ronnel were tested at 1/40 x REL, Sulprofos at 1/20 x REL (See Table 5, note 4). All criteria [9] were met.

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94

f

)