1.2 Detection limit of the overall procedure (DLOP) and reliable quantitation limit (RQL)

The DLOP is measured as mass per sample and expressed as equivalent air concentrations, based on the recommended sampling parameters. Ten samplers were spiked with equal descending increments of analyte, such that the highest sampler loading was 9.9 µg of IPAM. This is the amount spiked on a sampler that would produce a peak at least 10 times the response for a sample blank. These spiked samplers were analyzed with the recommended analytical parameters, and the data obtained used to calculate the required parameters (standard error of estimate (SEE) and slope) for the calculation of the DLOP. The slope was 2.76×10⁴ and the SEE was 3000. The RQL is considered the lower limit for precise quantitative measurements. It is determined from the regression line parameters obtained for the calculation of the DLOP, providing 75% to 125% of the analyte is recovered. The DLOP and RQL were 0.326 µg and 1.087 µg, respectively. The recovery at the RQL was 99.4%.

Table 1.2 Detection Limit of the Overall Procedure for IPAM mass per sample (µg) area counts (µV-s) 0.00 0.99 1.98 2.97 3.96 4.95 5.94 6.93 7.92 8.91 9.90 9284 32822 61744 90771 120847 147310 174654 196427 223071 258584 281776

Figure 1.2.1  Plot of data to determine the DLOP/RQL for IPAM at 254 nm using a TO-11. (y = 27600x + 8519; SEE = 300)

 
Below is the chromatogram of the RQL level.
 

Figure 1.2.2  Chromatogram of the IPAM peak in a standard near the RQL at 254nm using a TO-11 column. (Key: (1) IPAM; (2) interference in NITC)

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 × 4-mm i.d. × 7-mm o.d. glass sampling tubes packed with two sections (80/40 mg) of XAD-2 resin coated with 10% by weight 1-naphthylisothiocyanate. The sections are held in place and separated with a glass wool plugs. For this evaluation, commercially prepared sampling tubes were purchased from SKC, Inc. (catalog no. 226-30-18).

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 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 the 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 spiking NITC-coated XAD-2 tubes with IPAM at 0.1 to 2 times the target concentration. These samples were stored overnight at ambient temperature and then extracted for 30 minutes with shaking, and analyzed. The mean extraction efficiency over the studied range was 99.5%. The wet extraction efficiency was determined at 1 times the target concentration by spiking the analyte onto NITC-coated XAD-2 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 immediately before spiking. The mean recovery for the wet samples was 99.6%.

Table 2.4 Extraction Efficiency (%) of IPAM
level				sample number
× target concn	µg per sample	1	2	3	4	5	6	mean
0.1 0.25 0.5 1.0 1.5 2.0 1.0 (wet)	22.2 55.5 111 222 333 444 222	100.9 99.7 99.9 100.4 99.0 100.3 100.3	99.5 99.5 97.5 100.7 100.1 100.2 99.9	98.8 100.1 100.3 98.8 98.9 98.3 98.7	97.1 99.1 100.1 100.5 100.1 99.0 99.9	98.7 98.3 99.0 98.3 99.0 100.1 99.2	99.5 99.6 98.9 100.2 100.4 100.0 99.8	99.1 99.4 99.3 99.8 99.6 99.7 99.6

2.5 Retention efficiency

Six NITC-coated XAD-2 tubes were spiked with 444 µg (9.2 ppm) of IPAM and allowed to equilibrate for 4 h. Each spiked tube was placed in series with a second NITC-coated XAD-2 tube. Each sampling train 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 recovery was 99.6%. There was no analyte found on the back-up section of any of the tubes or on the second, back-up tube.

Table 2.5 Retention Efficiency (%) of IPAM
			sample number
section	1	2	3	4	5	6	mean
front of spiked tube rear of spiked tube front of series tube back of series tube total	99.9 0.0 0.0 0.0 99.9	98.6 0.0 0.0 0.0 98.6	99.0 0.0 0.0 0.0 99.0	100.3  0.0 0.0 0.0 100.3	99.5 0.0 0.0 0.0 99.5	100.4  0.0 0.0 0.0 100.4	99.6 0.0 0.0 0.0 99.6

2.6 Sample storage

Fifteen NITC-coated XAD-2 tubes were each spiked with 222 µg (4.6 ppm) of IPAM. They were allowed to equilibrate for 4 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 23°C), was drawn through them. Three samples were analyzed immediately, and the rest were sealed. Six were stored at room temperature (23 °C), while the other six were stored at refrigerated temperature (4 °C). Three samples stored at room temperature and three samples stored at refrigerated temperature were analyzed after 7 days and the remaining three after 14 days. The amounts recovered, indicate good storage stability for the time period studied.

Table 2.6 Storage Test for IPAM
time (days)	ambient	storage	recovery (%)		refrigerated	storage	recovery (%)
0 7 14	99.6 98.5 99.8	98.7 99.4 98.3	100.3 99.9 99.6		99.6 99.3 99.1	98.7 99.9 98.9	100.3 99.0 99.8

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 which will severely interfere with the collection of IPAM. Other primary and secondary amines will collect on this media, and form derivatives with the NITC, affecting the ability of the tube to collect IPAM, so sampling time should be adjusted if high concentrations of amines are expected.

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

3.1 Apparatus

3.1.1 A liquid chromatograph equipped with a UV detector. For this evaluation, a Waters 600 Controller and pump were used, with a Waters 2487 Dual wavelength absorbance Detector, and a Waters 717 plus Autosampler was used in this evaluation.

3.1.2 An LC column capable of separating IPAM from the desorption solvent and any potential interferences. A 4.6 × 250-mm column packed with 5µ Bakerbond cyanopropyl (JT Baker, Phillipsburg, NJ), and a 4.6 × 250-mm column packed with 5µ Pinnacle TO-11 (Bellefonte, PA) were used in the evaluation.

3.1.3 An electronic integrator or some other suitable means of measuring peak areas. A Waters Millennium³² Data System was used in this evaluation.

3.1.4 Glass vials with poly(tetrafluoroethylene)-lined caps. For this evaluation 4-mL vials were used.

3.1.5 A dispenser capable of delivering 2.0 mL of desorbing solvent to prepare standards and samples. If a dispenser is not available, a 2.0-mL volumetric pipet may be used.

3.1.7 Volumetric flasks - 10-mL and other convenient sizes for preparing standards.

3.2 Reagents

3.2.1 Isopropylamine, reagent grade. Aldrich lot 16828HA 99.5% was used in this evaluation.

3.2.2 N,N-Dimethyl formamide, reagent grade. Fisher 99.5%+ (lot 933764) was used for this evaluation.

3.2.3 1-Naphthylisothiocyanate, reagent grade. Aldrich 95%+ (lot 09925MY) was used in this evaluation.

3.2.4 Isopropyl alcohol, HPLC grade. Fisher 99.9% (lot 022995) was used in this evaluation.

3.2.5 Isooctane, HPLC grade. Fisher 99.0%+ (lot 025050) was used in this evaluation.

3.2.6 Acetonitrile, HPLC grade. Fisher 99.9%+ (lot 023721) was used in this evaluation.

3.2.7 Deionized water (DI water), 18 megaohm. A Barnstead NANOpure Diamond water deionizer was used in this evaluation.

3.2.8 Phosphoric acid, Baker Analyzed Reagent grade. Baker 85.9% (lot D25821) was used in this evaluation.

3.2.9 Mobile phase was 90:10 isooctane:isopropyl alcohol with the Bakerbond CN column.

3.2.10 Mobile phase was 55:45:0.2 acetonitrile:water:phosphoric acid with the Pinnacle TO-11 column.

3.3 Standard preparation

3.3.1 Prepare two stock standards. A stock standard of a concentration of 2 mg/mL may be prepared by weighing out about 50 mg of NITC in a 10-mL flask, then weigh out 20 mg IPAM placing the drops on top of the NITC in the flask, then weigh out about 50 mg more NITC on top of the IPAM. Allow the amine to react with the NITC for 1 hour. Partially fill the volumetric flask with DMF and allow to sit at least 30 minutes to dissolve the derivative, swirl to dissolve, and fill to the mark with DMF. Do not place the flask in a sonic bath to try to get the derivative to go into solution, as this will destroy the derivative. There must always be an excess of the NITC for the derivative to be completely formed. There is one amine group which will react with the NITC, so this mole ratio must be used in calculating the amount of NITC to be added. For example, the amount of NITC needed for the above stock standard would be calculated:

20 mg IPAM × (NITC MW=185.25/IPAM MW=59.08) = 62.7 mg NITC

In the above stock standard preparation a total of 100 mg NITC was weighed out so that an excess of NITC was present.

3.3.2 Diluted standards are prepared with a solution of 1 mg/mL NITC in DMF, so that an excess of NITC is always present. Bracket sample concentrations with working standard concentrations. If sample concentrations are higher than the concentration range of prepared standards, either analyze higher standards, or dilute the sample. The higher standards should be at least as high in concentration as the highest sample. Diluted samples should be prepared with a solution of 1 mg/mL NITC in the DMF. The range of standards used in this study was from 0.5 to 444 µg/mL.

3.4 Sample preparation

3.4.1 Remove the plastic end caps from the sample tubes and carefully transfer the adsorbent sections to separate 4-mL vials. Discard the glass tube, urethane foam plug and glass wool plug.

3.4.2 Add 2.0 mL of DMF to each vial using the same dispenser as used for preparation of standards.

3.4.3 Immediately seal the vials with poly(tetrafluoroethylene)-lined caps.

3.4.4 Shake the vials on a shaker for 30 minutes.

3.5 Analysis  

3.5.1 Liquid chromatograph conditions.

LC conditions reverse phase column: Restek TO-11 5-µ, 4.6 × 250-mm injection size: 10 µL mobile phase: 1.5 mL/min of 55:45:0.2 acetonitrile:water: phosphoric acid detector UV at 254 & 280 nm run time: 30 min retention times: 4.12 min IPAM 24.2 min NITC

Figure 3.5.1.1 A chromatogram of 222 µg/mL IPAM in DMF with NITC at 254 nm using a TO-11 column. Key: (1) DMF; (2) IPAM; (3) interference in NITC; and (4) NITC.

LC conditions normal phase column: Bakerbond cyanopropyl (CN) column 5-µ, 4.6 × 250-mm injection size: 10 µL mobile phase: 2 mL/min 90:10 isooctane: isopropyl alcohol detector: UV at 254 & 280 nm run time: 15 min retention times: 2.71 min NITC 4.83 min DMF 12.3 min IPAM

Figure 3.5.1.2 A chromatogram of 222 µg/mL IPAM in DMF with NITC at 254 nm using a Bakerbond CN column. Key: (1) NITC; (2) DMF; and (3) IPAM.

3.5.2 Peak areas are measured by an integrator or other suitable means. 3.5.3 An external standard (ESTD) calibration method is used. A calibration curve can be constructed by response of standard injections versus micrograms of analyte per sample. Bracket the samples with freshly prepared analytical standards over a range of concentrations

Figure 3.5.3 Calibration curve of IPAM at 254 nm using a TO-11 column. (Y= 1.57×105 x -1.86×105)

3.6 Interferences (analytical)

3.6.1 Any compound that produces a LC response and has a similar retention time as the analyte is a potential interference. If any potential interferences were reported, they should be considered before samples are extracted. Generally, chromatographic conditions can be altered to separate an interference from the analyte.

3.6.2 When necessary, the identity or purity of an analyte peak may be confirmed by a photodiode array scan of the peak, by wavelength ratioing, or by LC-mass spec.

3.7 Calculations

The amount of analyte per sampler is obtained from the appropriate calibration curve in terms of micrograms per sample, uncorrected for extraction efficiency. This total amount is then corrected by subtracting the total amount (if any) found on the blank. The air concentration is calculated using the following formulas.

	where	CM is concentration by weight (mg/m³) M is micrograms per sample V is liters of air sampled EE is extraction efficiency, in decimal form
	where	CV is concentration by volume (ppm) VM is molar volume at 25°C and 1 atm = 24.46 CM is concentration by weight Mr is molecular weight = 59.08