2.1 Apparatus

2.1.1 Samples are collected using a personal sampling pump calibrated, with the sampling device attached, to within ±5% of the recommended flow rate.

2.1.2 Samples are collected with 7-cm x 4-mm i.d. x 7-mm o.d. glass sampling tubes packed with two sections (100/50 mg) of coconut shell charcoal. The sections are held in place and separated with glass wool plugs. For this evaluation, commercially prepared sampling tubes were purchased from SKC, Inc. (catalog no. 226-01, lot 2000).

2.2 Reagents

None required

2.3 Technique

2.3.1 Immediately before sampling, break off the ends of the flame-sealed tube to provide an opening approximately half the internal diameter of the tube. Wear eye protection when breaking tube ends. Use tube holders to minimize the hazard of broken glass. All tubes should be from the same lot.

2.3.2 The smaller section of the adsorbent tube is used as a back-up and is positioned nearest the sampling pump. Attach the tube holder to the sampling pump so that the adsorbent tube is in an approximately vertical position with the inlet facing down during sampling. Position the sampling pump, tube holder and tubing so they do not impede work performance or safety.

2.3.3 Draw air to be sampled directly into the inlet of the tube holder. The air being sampled is not to be passed through any hose or tubing before entering the sampling tube.

2.3.4 After sampling for the appropriate time, remove the adsorbent tube and seal it with plastic end caps. Seal each sample end-to-end with an OSHA-21 form as soon as possible.

2.3.5 Submit at least one blank sample with each set of samples. Handle the blank sample in the same manner as the other samples except draw no air through it.

2.3.6 Record sample air volumes (liters), sampling time (minutes) and sampling rate (L/min) for each sample, along with any potential interferences on the OSHA-91A form.

2.3.7 Submit the samples to the laboratory for analysis as soon as possible after sampling. If delay is unavoidable, store the samples at refrigerator temperature. Ship any bulk samples separate from the air samples.

2.4 Extraction efficiency

The extraction efficiency was determined by liquid-spiking front sections of charcoal tubes with kerosene at 0.1 to 2 times the target concentration. These samples were stored overnight at ambient temperature and then extracted for 30 minutes with occasional shaking, and analyzed.

The mean extraction efficiency over the studied range was 98.2 %. The wet extraction efficiency was determined at 1 times the target concentration by liquid spiking the analyte onto charcoal tubes which had 20 L humid air (absolute humidity of 15.9 mg/L of water, about 80% relative humidity at 22.2 °C) drawn through them. The mean recovery for the wet samples was 100.5%.

Table 2.4 Extraction Efficiency (%) of Kerosene
level		sampler number
x target concn	mg per sample	1	2	3	4	5	mean
0.1	0.2	96.0	98.0	93.0	95.0	95.0	95.4
0.2	0.4	97.3	99.0	98.8	100.0	97.3	98.5
0.5	1.0	100.0	100.7	99.6	100.5	99.6	100.1
1.0	2.0	99.5	99.2	99.3	99.2	95.1	98.5
2.0	4.0	101.3	95.2	100.2	100.4	95.4	98.5
1.0 (wet)	2.0	99.4	100.6	100.6	102.4	99.4	100.5

2.5 Retention efficiency

Six charcoal tubes were spiked with 4.0 mg of kerosene in the front section of the tubes and allowed to equilibrate for 6 h. The tubes had 20 L humid air (absolute humidity of 15.9 mg/L of water, about 80% relative humidity at 22.2°C) pulled through them at 0.1 L/min. The samples were extracted and analyzed. The mean retention recovery was 98.6%. There was no analyte found on the backup section of any of the tubes.

Table 2.5 Retention Efficiency (%) of Kerosene
	sample number
section	1	2	3	4	5	6	mean
front of spiked tube	99.8	99.0	99.2	98.6	97.2	97.8	98.6
rear of spiked tube	0.0	00.0	00.	00.0	00.0	00.0	00.0
total	99.8	99.0	99.2	98.6	97.2	97.8	98.6

2.6 Sample storage

Nine charcoal tubes were each spiked with 2.0 mg of kerosene. They were allowed to equilibrate for 6 h, then 20 L of air, with an absolute humidity of 15.7 milligrams of water per liter of air (about 80% relative humidity at 22.2°C), was drawn through them. Three samples were analyzed immediately, and the rest were sealed and stored at room temperature. Three more were analyzed after 7 days of storage and the remaining three after 14 days of storage.

Table 2.6 Storage Test for Kerosene (% Recovery)
sample number
time (days)	1	2	3	mean
0	99.4	100.9	100.6	100.3
7	97.3	98.8	98.0	98.0
14	99.6	96.6	99.5	98.6

2.7 Recommended air volume and sampling rate

Based on the data collected in this evaluation, 20-L air samples should be collected at a sampling rate of 0.1 L/min for 200 minutes.

2.8 Interferences (sampling)

2.8.1 There are no known compounds that will severely interfere with the collection of kerosene.

2.8.2 Suspected interferences should be reported to the laboratory with submitted samples.