3.1 Apparatus

3.1.1 A GC equipped with a flame ionization detector (FID). A Hewlett-Packard Model 5890 Series II GC equipped with a ChemStation, an automatic sample injector, and an FID were used in this evaluation.

3.1.2 A GC column capable of separating MEK and MIBK from the extraction solvent, internal standards, and potential interferences. A J&W Scientific 60-m × 0.32-mm i.d. DB-Wax (0.5-µm df) capillary column was used in this evaluation.

3.1.3 An electronic integrator or other suitable means of measuring GC detector response. A Waters Millennium Chromatography Manager system was used in this evaluation.

3.1.4 Two and four-milliliter glass vials with PTFE-lined septum caps.

3.1.5 One and two-milliliter volumetric pipets.

3.1.6 An SKC Desorption Shaker with rack (226D-03K) was used to extract SKC 575-002 Passive Samplers in this evaluation.

3.2 Reagents

3.2.1 2-Butanone (methyl ethyl ketone, MEK) [CAS no. 78-93-3], reagent grade or better. The MEK used in this evaluation was 99+% A.C.S. Reagent grade (lot no. 11619CX) purchased from Aldrich (Milwaukee, WI).

3.2.2 Hexone (methyl isobutyl ketone, MIBK) [CAS no. 108-10-1], reagent grade or better. The MIBK used in this evaluation was Analytical Reagent grade (lot no. CVT) purchased from Mallinckrodt (St. Louis, MO)

3.2.3 Carbon disulfide (CS₂), [CAS no. 75-15-0], reagent grade or better. The carbon disulfide used in this evaluation was 99.9+% low benzene content grade (lot no. 1054JQ) purchased from Aldrich (Milwaukee, WI).

3.2.4 N,N-Dimethyl formamide (DMF) [CAS no. 68-12-2], reagent grade or better. The DMF used in this evaluation was Certified A.C.S. grade (lot no. 902902) purchased from Fisher (Fair Lawn, NJ).

3.2.5 1-Phenylhexane (hexylbenzene) [CAS no. 1077-16-3], reagent grade or better. The 1-phenylhexane used in this evaluation was 97% reagent grade (lot no. 03006PZ) purchased from Aldrich (Milwaukee, WI).

3.2.6 The extraction solvent used for this evaluation consisted of 1% DMF in CS₂. 1-Phenylhexane (1 µL/mL) was added to the solution for use as an internal standard. Other internal standards can be used provided they are fully tested.

3.3 Standard preparation

3.3.1 Prepare concentrated stock standards by weighing 3 mL of MEK and/or 2 mL of MIBK into a 5-mL volumetric flask, and diluting to the mark with CS₂. Obviously, no CS₂ addition is necessary if both MEK and MIBK are added to the same flask. Prepare working analytical standards by injecting microliter amounts of concentrated stock standards into vials containing either 1 or 2 mL of extracting solution delivered from the same dispenser used to extract samples. For example, to prepare a target level standard to analyze SKC Anasorb CMS sampling tubes, inject 15 µL of a stock solution containing 480 mg/mL of MEK and 320 mg/mL MIBK into 1 mL of extracting solution.

3.3.2 Bracket sample concentrations with standard concentrations. If, upon analysis, sample concentrations fall outside the range of prepared standards, prepare and analyze additional standards to confirm instrument response, or dilute high samples with extraction solvent and reanalyze the diluted samples.

3.4 Sample preparation

3.4.1 SKC Anasorb CMS sampling tubes

Remove the plastic end caps from the sample tube and carefully transfer each section of the adsorbent to separate 2-mL vials. Discard the glass tube and glass wool plugs.

Add 1.0 mL of extracting solution to each vial and immediately seal the vials with polytetrafluoroethylene-lined caps.

Shake the vials vigorously several times during the 60 min extraction time.

3.4.2 SKC 575-002 Passive Samplers (In general, follow the manufacturer's instructions.)

Cut off the ends of the two protruding tubes (ports) of each sampler with a razor blade or sharp knife.

Slowly and carefully add 2.0 mL of extraction solvent through the protruding tube (port) nearest the outside edge of the sampler.

Immediately insert plugs into the ports.

Mount the samplers in the sampler rack (SKC Cat. No. 226-04-5) of a specialized shaker (SKC Cat. No. 226D-03-1) and shake the samplers for 1 hour.

Do not leave the extracted sample in the sampler. Transfer each extracted sample by removing the plugs from the sampler ports, firmly inserting the tapered end of a supplied PTFE tube into the outer port, and carefully pouring the solution through the PTFE tube into a labeled autosampler vial. Immediately cap each vial.

3.4.3 3M 3520 OVMs (In general, follow the manufacturer's instructions.)

Remove both sampler sections from the metal cans, along with the sections of PTFE tubing. Assure that the closure caps are firmly snapped to the primary and secondary sections of all the samplers. Also assure that all cap plugs are firmly seated in the cap ports. Any deviations must be noted.

Prepare one section of the sampler at a time by temporarily removing the cap plugs from the ports and adding 2.0 mL of extraction solvent through the center port.

Allow the sampler sections to extract for one hour. Apply gentle agitation to the sampler sections, periodically, during the extraction period.

Do not leave the extracted sample in the sampler. Transfer the solution from each sampler section by removing both plugs from the ports, firmly inserting a decanting spout (a small section of PTFE tubing) into the outer port and carefully pouring the liquid through the spout into a labeled autosampler vial. Immediately cap each vial.

3.5 Analysis

3.5.1 Analytical conditions

GC conditions
column temperature:	initial 40°C, hold 1 min, program at 4°C/min to 140°C, hold until column is clear.
zone temperatures:	220°C (injector) 220°C (detector)
run time:	26 min
column gas flow:	4.9 mL/min (hydrogen)
septum purge:	3.3 mL/min (hydrogen)
injection size:	1.0 µL (26:1 split)
column:	60-m × 0.32-mm i.d. capillary J&W DB-Wax (0.5-µm df)
retention times:	4.1 min (MEK) 6.3 min (MIBK) 23.4 min (1-phenylhexane)
FID conditions
hydrogen flow:	35 mL/min
air flow:	450 mL/min
nitrogen makeup flow:	37 mL/min

Figure 3.5.1. Chromatogram obtained at the target concentrations with the recommended conditions. (1- CS2; 2- MEK; 3- MIBK; 4- DMF; 5- 1-phenylhexane)

3.5.2 An internal standard (ISTD) calibration method is used. A calibration curve can be constructed by plotting ISTD-corrected response of standard injections versus micrograms of analyte per sample. Bracket the samples with freshly prepared analytical standards over a range of concentrations.

Figure 3.5.2.1. Calibration curve for MEK

Figure 3.5.2.2. Calibration curve for MIBK

3.6 Interferences (analytical)

3.6.1 Any compound that produces an FID response and has a similar retention time as the analyte or internal standard 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 of an analyte peak can be confirmed with additional analytical data (Section 4.9).

3.7 Calculations

3.7.1 SKC Anasorb CMS sampling tubes

The amount of MEK and/or MIBK per sample is obtained from the appropriate calibration curve in terms of micrograms per sample, uncorrected for extraction efficiency. The back section is analyzed primarily to determine the extent of sampler saturation. If any analyte is found on the back section, it is added to the amount on the front section. 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.

CM =   M VEE	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
CV =   VMCM Mr	where:   CV   is concentration by volume (ppm) VM is molar volume at 25°C and 760 mmHg (NTP) CM is concentration by weight Mr is molecular weight (MEK = 72.10, MIBK = 100.16)

3.7.2 Diffusive samplers

Table 3.7.2 Sampling Rates (mL/min) at 760 mmHg and 298.2 K (NTP)
	MEK	MIBK
SKC 575-002 3M 3520	16.88 32.59	13.62 27.00

The amount of MEK and/or MIBK for the samples is obtained from the appropriate calibration curve in terms of micrograms per sample, uncorrected for extraction efficiency. The 3M 3520 is a two-section sampler and the back section is analyzed primarily to determine the extent of sampler saturation. If any analyte is found on the back section, the amount is multiplied by 2.2 (as per manufacturer's instructions) and then added to the amount on the front section. The 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.

RSS = RNTP ( Tss ) 3/2 ( PNTP ) TNTP PSS	where   RSS is the sampling rate at sampling site RNTP is the sampling rate at NTP TSS is the sampling site temperature in K TNTP is 298.2 K PSS is the sampling site pressure in mmHg PNTP is 760 mmHg
CM =   M tRSSEE	where   CM is concentration by weight (mg/m3) M is micrograms per sample RSS is the sampling rate at the sampling site t is the sampling time EE is extraction efficiency, in decimal form
CV =   VMCM Mr	where   CV is concentration by volume (ppm) VM is molar volume at NTP CM is concentration by weight Mr is molecular weight (MEK = 72.10, MIBK = 100.16)

If the sampling site temperature is not provided, assume that it is 22.2 °C. If the sampling site atmospheric pressure is not given, calculate an approximate value based on the sampling site elevation from the following equation.

PSS = AE2 - BE + 760.0

where   PSS is the approximate atmospheric pressure E is the sampling site elevation, ft A is 3.887×10-7 mmHg/ft2 B is 0.02748 mmHg/ft

4.1 Detection limit of the analytical procedure (DLAP)

DLAP is measured as the mass of analyte introduced onto the chromatographic column. Ten analytical standards were prepared with equal increments with the highest standard containing 475 ng/mL of MEK and 553 ng/mL of MIBK. These are concentrations that would produce peaks approximately 10 times the response of a reagent blank near the elution times of the analytes. These standards, and the reagent blank were analyzed with the recommended analytical parameters (1-µL injection with a 26:1 split), and the data obtained were used to determine the required parameters (standard error of estimate and slope) for the calculation of the DLAP. The DLAP for MEK was 4.90 pg and it was 3.13 pg for MIBK.

Table 4.1.1 Detection Limit of the Analytical Procedure for MEK concentration (ng/mL) mass on column (pg) area counts (µV-s) 0 48 95 142 190 238 285 332 380 428 475 0 1.8 3.6 5.5 7.3 9.2 11.0 12.8 14.6 16.5 18.3 0 16 28 35 43 60 40 70 74 83 96	Figure 4.1.1 Plot of data used to determine the DLAP for MEK.
Table 4.1.2 Detection Limit of the Analytical Procedure for MIBK concentration (ng/mL) mass on column (pg) area counts (µV-s) 0 33 98 163 228 293 358 390 423 488 553 0 1.3 3.8 6.3 8.8 11.3 13.8 15.0 16.3 18.8 21.3 0 12 23 45 55 68 90 90 92 99 132	Figure 4.1.2 Plot of data used to determine the DLAP for MIBK.

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

DLOP is measured as mass per sample and expressed as equivalent air concentrations, based on the recommended sampling parameters. Ten samplers were spiked with descending increments of analyte. The highest amount shown in the following tables is the amount spiked on a sampler that would produce a peak approximately 10 times the response of a sample blank. These spiked samplers, and the sample blanks were analyzed with the recommended analytical parameters, and the data obtained used to calculate the required parameters (standard error of estimate and the slope) for the calculation of the DLOP.

Table 4.2 Detection Limits of the Overall Procedure
	MEK				MIBK
sampler	ng	ppb	µg/m3		ng	ppb	µg/m3
SKC CMS SKC Anasorb 747 SKC 575-002 3M 3520	244 291 388 230	7 8 33 10	20 24 96 29		129 329 376 281	3 7 28 11	11 27 115 43

Table 4.2.1 DLOP/RQL for MEK Collected on SKC CMS Sampling Tubes mass per sample (ng) area counts (µV-s) 0 48 142 238 332 428 522 570 618 713 808 0 26 14 31 44 47 54 58 66 66 94		Figure 4.2.1 Plot of data to determine the DLOP/RQL for MEK collected on SKC CMS sampling tubes.
Table 4.2.2 DLOP/RQL for MIBK Collected on SKC CMS Sampling Tubes mass per sample (ng) area counts (µV-s) 0 65 130 195 260 325 358 390 455 520 553 0 0 16 22 28 32 40 43 66 64 61		Figure 4.2.2 Plot of data to determine the DLOP/RQL for MIBK collected on SKC CMS sampling tubes.
Table 4.2.3 DLOP/RQL for MEK Collected on SKC Anasorb 747 Sampling Tubes mass per sample (ng) area counts (µV-s) 0 190 380 570 665 760 855 1045 1235 1425 1615 0 11 18 25 31 36 42 46 57 68 93		Figure 4.2.3 Plot of data to determine the DLOP/RQL for MEK collected on SKC Anasorb 747 sampling tubes.
Table 4.2.4 DLOP/RQL for MIBK Collected on SKC Anasorb 747 Sampling Tubes mass per sample (ng) area counts (µV-s) 0 130 260 390 455 520 585 715 845 975 1105 0 13 24 40 33 35 42 53 57 76 110		Figure 4.2.4 Plot of data to determine the DLOP/RQL for MIBK collected on SKC Anasorb 747 sampling tubes.
Table 4.2.5 DLOP/RQL for MEK Collected on SKC 575-002 Passive Samplers mass per sample (ng) area counts (µV-s) 0 190 38 570 665 760 855 1045 1235 1425 1615 0 24 34 40 47 46 46 59 70 90 82		Figure 4.2.5 Plot of data to determine the DLOP/RQL for MEK collected on SKC 575-002 Passive Samplers.
Table 4.2.6 DLOP/RQL for MIBK Collected on SKC 575-002 Passive Samplers mass per sample (ng) area counts (µV-s) 0 130 260 390 455 520 585 715 845 975 1105 0 11 21 28 29 40 39 66 77 55 79		Figure 4.2.6 Plot of data to determine the DLOP/RQL for MIBK collected on SKC 575-002 Passive Samplers.
Table 4.2.7 DLOP/RQL for MEK Collected on 3M 3520 OVMs mass per sample (ng) area counts (µV-s) 0 95 285 475 665 855 1045 1140 1235 1425 1615 0 6 24 29 42 49 58 65 79 80 86		Figure 4.2.7 Plot of data to determine the DLOP/RQL for MEK collected on 3M 3520 OVMs.
Table 4.2.8 DLOP/RQL for MIBK Collected on 3M 3520 OVMs mass per sample (ng) area counts (µV-s) 0 65 195 325 455 585 715 780 845 975 1105 0 4 14 18 24 44 43 48 54 81 70		Figure 4.2.8 Plot of data to determine the DLOP/RQL for MIBK collected on 3M 3520 OVMs.

The RQL is considered the lower limit for precise quantitative measurements. It is determined from the regression line parameters obtained for calculation of the DLOP, providing the extraction efficiency (E_E) is 75% to 125%.

Table 4.2.9 Reliable Quantitation Limits
	MEK					MIBK
sampler	ng	ppb	µg/m3	EE		ng	ppb	µg/m3	EE
SKC CMS SKC Anasorb 747 SKC 575-002 3M 3520	813 971 1295 766	23 27 109 33	68 81 320 98	98.5 101.5 90.4 105.3		430 1097 1255 937	9 22 94 35	36 91 384 144	111.7 98.2 81.0 86.4

Figure 4.2.9 Chromatogram of the RQL for MEK extracted from SKC Anasorb CMS sampling tubes. Peak 1 is MEK.		Figure 4.2.10 Chromatogram of the RQL for MIBK extracted from SKC Anasorb CMS sampling tubes. Peak 1 is MIBK.
Figure 4.2.11 Chromatogram of the RQL for MEK extracted from SKC Anasorb 747 sampling tubes. Peak 1 is MEK.		Figure 4.2.12 Chromatogram of the RQL for MIBK extracted from SKC Anasorb 747 sampling tubes. Peak 1 is MIBK.
Figure 4.2.13 Chromatogram of the RQL for MEK extracted from SKC 575-002 Passive Samplers. Peak 1 is MEK.		Figure 4.2.14 Chromatogram of the RQL for MIBK extracted from SKC 575-002 Passive Samplers. Peak 1 is MIBK.
Figure 4.2.15 Chromatogram of the RQL for MEK extracted from 3M 3520 OVM. Peak 1 is MEK.		Figure 4.2.16 Chromatogram of the RQL for MIBK extracted from 3M 3520 OVM. Peak 1 is MIBK.

4.3 Instrument Calibration

The standard errors of estimate were determined from the linear regressions of data points from standards over a range that covers 0.25 to 2 times the target concentrations for SKC CMS sampling tubes. This was the sampler with the highest mass loadings. Calibration curves were constructed and shown in Section 3.5.2 from the injections of the fifteen standards. The standard errors of estimate are 64 µg/sample for MEK and 47 µg/sample for MIBK.

Table 4.3.1 Instrument Calibration for MEK
standard concn (µg/sample)		area counts (µV·s)
1900 3800 7125 10450 14250		209059 382186 711627 1030541 1410615	203442 383631 702855 1028461 1414645	194603 389559 701446 1025964 1406129

Table 4.3.2 Instrument Calibration for MIBK
standard concn (µg/sample)		area counts (µV·s)
1300 2601 4876 7152 9753		171450 313431 584366 845491 1157297	166556 313539 575873 842971 1161587	158962 319156 576681 839986 1153280

4.4 Precision (overall procedure)

4.4.1 SKC CMS sampling tubes

The precision at the 95% confidence level is obtained by multiplying the standard error of estimate by 1.96 (the z-statistic from the standard normal distribution at the 95% confidence level). In Section 4.5, 95% confidence intervals are drawn about their respective regression lines in the storage graph figures. Each precision includes an additional 5% for sampling error. The precisions of the overall procedure at the 95% confidence interval for the ambient temperature 15-day storage tests (at the target concentration) for MEK and for MIBK were ±11.7% and ±11.5%, respectively. These values are from the standard error of estimates shown in Figures 4.5.1.1 and 4.5.1.3.

4.4.2 Diffusive samplers

The precisions of the overall procedure at the 95% confidence level for the ambient temperature 15-day storage tests (at the target concentration) are shown in Table 4.4.2. There are different values given, depending on whether both, either, or neither temperature (T) or atmospheric pressure (P) at the sampling site are known. If the sampling site temperature is unknown, it is assumed to be 22.2 ± 15°C (72 ± 27°F) and a variability of ±7.7% is included. If the atmospheric pressure is not known, it is estimated from the sampling site elevation and a variability of ±3% is included. Each 3M precision value includes an additional 7.4% for sampling rate variation, and each SKC value an additional 8.7%, also for sampling rate variation ¹².

4.5 Storage tests

4.5.1 Active samples

Storage samples for MEK and MIBK were generated by sampling controlled test atmospheres with SKC CMS and with SKC Anasorb 747 sampling tubes at 50 mL/min for four hours. The analyte concentrations of the test atmospheres were the target concentrations with an absolute humidity of 14.3 milligrams of water per liter of air (77.2% at 21.1°C). Thirty-three storage samples were collected with each sampler. Three of each sampler were analyzed on the day of generation. Fifteen of each sampler were stored at reduced temperature (about 4°C) and the other fifteen were stored in a closed drawer at ambient temperature (about 22°C). Three samples were selected from each of the storage sets and analyzed at 2-4 day intervals. Sample results were not corrected for extraction efficiency.

Table 4.5.1.1 Storage Tests for MEK on SKC CMS Sampling Tubes
time (days)	ambient storage recovery (%)				refrigerated storage recovery (%)
0 2 5 8 12 15	95.0 90.7 88.2 92.3 92.2 85.8	94.4 89.2 83.7 89.7 86.3 80.4	90.8 96.4 88.0 91.5 87.3 82.7		95.0 96.3 93.0 96.2 94.0 92.6	94.4 95.9 92.7 94.3 94.1 94.2	90.8 96.4 92.0 95.1 93.3 88.8

Table 4.5.1.2 Storage Tests for MIBK on SKC CMS Sampling Tubes
time (days)	ambient storage recovery (%)				refrigerated storage recovery (%)
0 2 5 8 12 15	96.1 92.7 91.0 96.6 96.7 95.1	95.3 91.4 89.7 94.6 94.4 88.5	92.6 97.5 88.0 96.5 95.1 90.6		96.1 96.3 95.2 96.3 95.3 95.5	95.3 96.1 94.6 96.4 95.9 97.2	92.6 95.9 93.1 97.0 96.0 96.0

Table 4.5.1.3 Storage Tests for MEK on SKC Anasorb 747 Sampling Tubes
time (days)	ambient storage recovery (%)				refrigerated storage recovery (%)
0 2 5 8 12 15	89.3 82.8 75.9 76.7 74.2 73.3	90.7 82.6 77.1 76.6 73.2 74.0	90.8 84.0 78.4 76.9 70.6 70.4		89.3 88.9 86.5 82.3 81.2 79.3	90.7 88.5 87.1 81.5 80.5 81.1	90.8 87.1 85.8 83.1 78.7 80.4

Table 4.5.1.4 Storage Tests for MIBK on SKC Anasorb 747 Sampling Tubes
time (days)	ambient storage recovery (%)				refrigerated storage recovery (%)
0 2 5 8 12 15	93.6 93.8 91.8 93.4 92.4 93.5	93.9 93.4 93.8 93.7 91.5 93.0	94.4 94.6 92.9 93.3 88.5 89.2		93.6 93.1 93.9 92.4 92.9 92.4	93.9 94.5 91.2 92.2 93.1 93.6	94.4 92.9 93.0 91.6 91.3 93.8

Figure 4.5.1.1 Ambient Storage for MEK collected on SKC CMS sampling tubes.		Figure 4.5.1.2 Refrigerated Storage for MEK collected on SKC CMS sampling tubes.
Figure 4.5.1.3 Ambient Storage for MIBK collected on SKC CMS sampling tubes.		Figure 4.5.1.4 Refrigerated Storage for MIBK collected on SKC CMS sampling tubes.
Figure 4.5.1.5 Ambient Storage for MEK collected on SKC Ansasorb 747 sampling tubes.		Figure 4.5.1.6 Refrigerated Storage for MEK collected on SKC Anasorb 747 sampling tubes.
Figure 4.5.1.7 Ambient Storage for MIBK collected on SKC Anasorb 747 sampling tubes.		Figure 4.5.1.8 Refrigerated Storage for MIBK collected on SKC Anasorb 747 sampling tubes.

4.5.2 Diffusive samplers

Storage samples for MEK and MIBK were generated by sampling controlled test atmospheres with SKC 575-002 Passive Samplers and with 3M 3520 OVMs for four hours. The analyte concentrations of the test atmospheres were the target concentrations with an absolute humidity of 14.3 milligrams of water per liter of air (77.2% at 21°C). Thirty-three storage samples were collected with each sampler. Three of each sampler were analyzed on the day of generation. Fifteen of each sampler were stored at reduced temperature (about 4°C) and the other fifteen were stored in a closed drawer at ambient temperature (about 22°C). Three samples were selected from each of the storage sets and analyzed at 2-4 day intervals. Sample results were not corrected for extraction efficiency.

Table 4.5.2.1 Storage tests for MEK on SKC 575-002 Passive Samplers
time (days)		ambient storage recovery (%)				refrigerated storage recovery (%)
0 2 5 8 12 15		96.6 95.5 90.2 83.6 84.1 79.3	98.9 95.7 90.5 86.0 84.3 79.5	89.2 98.5 87.2 89.9 83.0 78.8		96.6 94.6 95.9 90.5 91.2 91.3	98.9 97.7 96.8 92.0 91.2 90.3	89.2 99.5 95.8 93.8 93.2 93.7

Table 4.5.2.2 Storage tests for MIBK on SKC 575-002 Passive Samplers
time (days)		ambient storage recovery (%)				refrigerated storage recovery (%)
0 2 5 8 12 15		96.9 96.6 92.1 89.9 89.3 84.8	99.2 95.9 93.2 93.0 89.7 85.1	89.8 97.0 88.1 92.5 89.3 85.7		96.9 94.3 95.2 86.7 89.9 87.5	99.2 96.7 95.0 91.4 89.6 87.6	89.8 98.4 93.9 93.0 90.5 89.4

Table 4.5.2.3 Storage Tests for MEK on 3M 3520 OVMs
time (days)		ambient storage recovery (%)				refrigerated storage recovery (%)
0 2 5 8 12 15		96.9 96.5 98.7 89.2 94.0 99.8	101.3 96.6 92.9 100.5 92.8 96.2	92.8 89.5 92.4 92.7 100.2 98.0		96.6 96.9 101.8 92.7 104.1 98.8	101.3 93.5 97.6 97.6 91.5 93.9	92.8 94.6 97.5 92.3 95.1 102.8

Table 4.5.2.4 Storage Tests for MIBK on 3M 3520 OVMs
time (days)		ambient storage recovery (%)				refrigerated storage recovery (%)
0 2 5 8 12 15		101.2 101.8 103.7 95.3 99.7 105.5	104.9 101.2 100.1 105.8 100.9 103.3	100.5 94.9 98.7 99.2 105.0 103.0		101.2 102.4 109.4 97.8 108.5 103.1	104.9 99.4 103.3 105.3 97.3 98.7	100.5 100.5 102.1 96.9 101.8 106.9

Figure 4.5.2.1 Ambient Storage for MEK collected on SKC 575-002 Passive Samplers.		Figure 4.5.2.2 Refrigerated Storage for MEK collected on SKC 575-002 Passive Samplers.
Figure 4.5.2.3 Ambient Storage for MIBK collected on SKC 575-002 Passive Samplers.		Figure 4.5.2.4 Refrigerated Storage for MIBK collected on SKC 575-002 Passive Samplers.
Figure 4.5.2.5 Ambient storage for MEK collected on 3M 3520 OVMs.		Figure 4.5.2.6 Refrigerated storage for MEK collected on 3M 3520 OVMs.
Figure 4.5.2.7 Ambient storage for MIBK collected on 3M 3520 OVMs.		Figure 4.5.2.8 Refrigerated storage for MIBK collected on 3M 3520 OVMs.

4.6 Reproducibility

Six samples for each of the three samplers evaluated in this method were collected from a controlled test atmosphere and were submitted to OSHA SLTC for analysis. The concentration of the test atmosphere was 593.46 mg/m³ for MEK and 393.68 mg/m³ for MIBK. The absolute humidity was 16.9 milligrams of water per liter of air (77.8% RH at 24°C). The face velocity of the sampled air was 0.4 m/s. The samples were analyzed utilizing a draft copy of this procedure for analyst instruction. The samples were analyzed after being stored for 2 days at 4°C. Sample results were corrected for extraction efficiency. No sample result for either analyte had a deviation greater than the precision of the overall procedure determined in Section 4.4.

4.7 Sampler capacity

4.7.1 SKC Anasorb CMS sampling tubes

The sampling capacity of the front section of SKC Anasorb CMS sampling tubes was tested by sampling from a dynamically generated test atmosphere of 1131 mg/m³ (384 ppm) MEK and 774 mg/m³ (189 ppm) MIBK with an absolute humidity of 13.9 milligrams of water per liter of air (74% relative humidity at 22°C). Four samples were collected at about 50 mL/min. CMS sampling tubes were placed in-line behind the front test sections and they were changed every 15 min after initial collection for four hours. Five-percent breakthrough for MEK occurred after 15 L of air had been sampled. This air volume is that which would be collected in a 5-h air sample. Breakthrough of MIBK was never observed in any of the sampler capacity tests in which samples were collected for as long as ten hours. The recommended sampling time for SKC Anasorb CMS sampling tubes is 4 hours. This sampling time provides a considerable capacity safety margin for MEK because of the presence of MIBK in the test atmosphere.


Figure 4.7.1 Five percent breakthrough air volume for MEK from SKC Anasorb CMS

Table 4.7.1 Breakthrough of MEK from SKC Anasorb CMS
test no.	air vol. (L)	sampling time (min)	downstream concn (mg/m3)	breakthrough (%)
1	11.97 12.72 13.47 14.22 14.96 15.71 16.46 17.21 17.96	240 15 15 15 15 15 15 15 15	0.0 0.0 0.0 6.7 25.8 73.4 212.3 493.1 915.6	0.0 0.0 0.0 0.6 2.3 6.5 18.8 43.6 81.0
2	11.70 12.43 13.17 13.90 14.63 15.36 16.09 16.82 17.55	240 15 15 15 15 15 15 15 15	0.0 0.0 0.0 0.0 7.7 33.3 117.9 286.4 625.8	0.0 0.0 0.0 0.0 0.7 2.9 10.4 25.3 55.3
3	12.09 12.84 13.60 14.35 15.11 15.86 16.82 17.37 18.13	240 15 15 15 15 15 15 15 15	0.0 0.0 9.2 44.3 11.5 211.5 360.6 613.2 879.8	0.0 0.0 0.8 3.9 1.0 18.7 31.9 54.2 77.8
4	11.21 11.91 12.61 13.31 14.01 14.71 15.41 16.11 16.81	240 15 15 15 15 15 15 15 15	0.0 0.0 4.2 12.0 35.7 84.9 153.1 326.8 598.4	0.0 0.0 0.4 1.1 3.2 7.5 13.5 28.9 52.9

4.7.2 Diffusive samplers

Sampling rate and sampler capacity were determined using SKC and 3M samplers that were exposed to a controlled test atmosphere for increasing time intervals. Three of each sampler were exposed for each time interval. Sampler capacity is defined as exceeded when the sampling rate appears to decrease, as was the case for MEK collected on 3M 3520 OVMs. The concentration of the test atmospheres was about two times the target concentration with an absolute humidity of about 16.4 milligrams of water per liter of air (80% RH at 23°C). Preliminary sampling rates were determined by averaging the values for the 0.5, 1 and 2 h samples. Horizontal lines were placed 10% above and 10% below the preliminary sampling rates. Sampling rates were calculated by averaging all the individual sampling rates that were between the two horizontal lines. Sampling rates, RSDs of individual runs, and RSDs of average sampling rates are shown in Table 4.7.2.1. Data shown in Table 4.7.2.1 are for the front section of the 3M samplers. A five-hour experiment was performed for the 3M sampler because its capacity for MEK was exceeded before six hours. The recommended sampling time is four hours.

Figure 4.7.2.1 Sampler capcity Data for MEK collected on SKC 575-002 Passive Sampler.		Figure 4.7.2.2 Sampler capcity Data for MIBK collected on SKC 575-002 Passive Sampler.
Figure 4.7.2.3 Sampler capcity Data for MEK collected on 3M 3520 OVM.		Figure 4.7.2.4 Sampler capcity Data for MIBK collected on 3M 3520 OVM.

Sampling rate is normally calculated using only the front section of two-section samplers. The 3M 3520 OVM is a two-section sampler. When MEK collected on the back section was included in the total amount, the resultant MEK sampling rates were comparable with those obtained above. This data should not be used to justify sampling times longer than four hours, but it does show the value of a two-section sampler.

Table 4.7.2.2 MEK Sampling Rates for 3M 3520 OVM With Back Section Included
time (h)	mL/min	RSD (%)
6 8 10	31.54 32.84 32.29	4.0 0.7 1.5

4.8 Extraction efficiency and stability of extracted samples

A summary of extraction efficiencies (at concentrations near the RQL to 2 times the target concentration) for all the sampling media used in this work is shown in Table 4.8. The extraction efficiency is dependent on the extraction solvent as well as the internal standard. Other extraction solvents or internal standards may be used provided they are tested as described below.

Table 4.8 Extraction Efficiency Summary
medium	MEK (%)	MIBK (%)
Anasorb CMS Anasorb 747 SKC 575-002 3M 3520 OVM	100.3 97.9 92.2 98.0	102.3 99.0 92.9 96.5

4.8.1 SKC Anasorb CMS sampling tubes

Extraction efficiency

The extraction efficiencies of MEK and MIBK were determined by liquid-spiking 150 mg portions of Anasorb CMS with the analytes at concentrations from the RQL to 2 times the target concentration. These samplers were stored overnight at ambient temperature and then analyzed. The mean extraction efficiency over the working range of the RQL to 2 times the target concentration is 100.3% for MEK and 102.3% for MIBK. The extraction efficiency for MEK from wet samplers was lower than for dry samplers. These results were expected because of the instability of MEK on wet carbon-based sorbents. The extraction efficiency for the wet samplers was not included in the overall mean because it would bias the results. Wet sampling media used in extraction efficiency tests were all prepared by sampling contaminant-free, humid air (about 80% relative humidity at 22°C) for four hours at the recommended sampling rate.

Table 4.8.1.1 Extraction Efficiency of MEK from Anasorb CMS (%)
level		sample number
× target concn	µg per sample	1	2	3	4	mean
RQL 0.25 0.5 1.0 1.5 2.0 1.0 (wet)	0.808 1781 3562 7125 10450 14250 7125	100.7 98.4 99.7 104.0 101.8 101.3 89.9	101.6 98.1 101.0 96.9 101.1 100.6 86.3	92.8 98.4 98.2 104.7 101.8 99.5 87.1	98.7 98.7 100.6 104.4 99.6 103.5 91.5	98.5 98.4 99.9 102.5 101.1 101.2 88.7

Table 4.8.1.2 Extraction Efficiency of MIBK from Anasorb CMS (%)
level		sample number
× target concn	µg per sample	1	2	3	4	mean
RQL 0.25 0.5 1.0 1.5 2.0 1.0 (wet)	0.423 1219 2438 4876 7152 9753 4876	111.0 98.6 98.0 103.7 101.4 100.8 98.6	111.9 98.7 99.8 98.0 102.3 100.4 95.4	114.5 98.7 97.8 104.1 101.8 99.6 96.2	109.3 98.4 99.1 103.6 100.4 102.7 99.5	111.7 98.6 98.7 102.4 101.5 100.9 97.4

Stability of extracted samples

The stability of extracted samples was investigated by reanalyzing the target concentration samples a day after the initial analysis. After the original analysis was performed two vials were recapped with new septa while the remaining two retained their punctured septa. The samples were reanalyzed with fresh standards. Each septum was punctured 6 times for each injection.

Table 4.8.1.3 Stability of Samples for MEK Extracted From Anasorb CMS
punctured septa replaced				punctured septa retained
initial (%)	after one day (%)	difference (%)		initial (%)	after one day (%)	difference (%)
104.0 96.9 100.5	100.3 100.2 mean 100.3	-3.7 3.3 -0.2		104.7 104.4 104.6	89.3 84.9 mean 87.1	-15.4 -19.5 -17.5

Table 4.8.1.4 Stability of Samples for MIBK Extracted From Anasorb CMS
punctured septa replaced				punctured septa retained
initial (%)	after one day (%)	difference (%)		initial (%)	after one day (%)	difference (%)
103.7 98.0 100.9	100.8 100.2 mean 100.5	-2.9 2.2 -0.4		104.1 103.6 103.9	96.8 96.8 mean 96.8	-7.3 -6.8 -7.1

The stability test for MEK was repeated with the reanalysis performed 12 hours after the initial analysis. After the original analysis was performed, two vials were recapped with new septa while the remaining two retained their punctured septa. The samples were reanalyzed with fresh standards. Each septum was punctured 6 times for each injection.

Table 4.8.1.5 Stability of Samples for MEK Extracted From Anasorb CMS
punctured septa replaced				punctured septa retained
initial (%)	after 12 h (%)	difference (%)		initial (%)	after 12 h (%)	difference (%)
98.3 97.5 97.9	96.6 96.1 mean 96.4	-1.7 -1.4 -1.6		99.1 99.0 99.1	92.6 94.0 mean 93.3	-6.5 -5.0 -5.8

4.8.2 SKC Anasorb 747 sampling tubes

Extraction efficiency

The extraction efficiencies of MEK and MIBK were determined by liquid-spiking 400 mg portions of Anasorb 747 with the analytes at concentrations from the RQL to 2 times the target concentration. These samplers were stored overnight at ambient temperature and then analyzed. The mean extraction efficiency over the working range of the RQL to 2 times the target concentration is 97.9% for MEK and 99.0% for MIBK. The extraction efficiency for MEK from wet samplers was lower than for dry samplers. These results were expected because of the instability of MEK on wet sorbents. The extraction efficiency for the wet samplers was not included in the overall mean because it would bias the results.

Table 4.8.2.1 Extraction Efficiency of MEK from Anasorb 747 (%)
level		sample number
× target concn	µg per sample	1	2	3	4	mean
RQL 0.25 0.5 1.0 1.5 2.0 1.0 (wet)	0.950 1781 3562 7125 10450 14250 7125	86.5 94.4 94.8 98.8 101.9 92.7 87.3	114.5 94.9 97.1 98.8 99.7 98.7 86.4	104.1 94.5 94.7 99.4 99.1 99.0 86.0	100.7 94.8 95.4 96.7 99.5 98.2 91.7	101.5 94.7 95.5 98.4 100.1 97.2 87.9

Table 4.8.2.2 Extraction Efficiency of MIBK from Anasorb 747 (%)
level		sample number
× target concn	µg per sample	1	2	3	4	mean
RQL 0.25 0.5 1.0 1.5 2.0 1.0 (wet)	0.683 1219 2438 4876 7152 9753 4876	103.6 97.3 96.9 100.2 102.9 96.0 96.3	91.1 96.6 99.6 101.1 101.3 100.7 95.0	100.2 96.6 96.8 101.7 101.0 100.7 94.9	97.8 96.6 97.4 99.5 101.3 100.2 99.6	98.2 96.8 97.7 100.6 101.6 99.4 96.5

Stability of extracted samples

The stability of extracted samples was investigated by reanalyzing the target concentration samples a day after initial analysis. After the original analysis was performed, two vials were recapped with new septa while the remaining two retained their punctured septa. Each septum was punctured 6 times for each injection.

Table 4.8.2.3 Stability of Samples for MEK Extracted From Anasorb 747
punctured septa replaced				punctured septa retained
initial (%)	after one day (%)	difference (%)		initial (%)	after one day (%)	difference (%)
98.8 98.8 98.8	97.8 100.2 mean 99.0	-1.0 1.4 0.2		99.4 96.7 98.1	88.6 84.4 mean 86.5	-10.8 -12.3 -11.6

Table 4.8.2.4 Stability of Samples for MIBK Extracted From Anasorb 747
punctured septa replaced				punctured septa retained
initial (%)	after one day (%)	difference (%)		initial (%)	after one day (%)	difference (%)
100.2 101.1 100.7	100.5 102.1 mean 101.3	0.3 1.0 0.7		101.7 99.5 100.6	98.0 96.0 mean 97.0	-3.7 -3.5 -3.6

The stability test for MEK was repeated with the reanalysis performed 12 hours after the initial analysis. After the original analysis was performed, two vials were recapped with new septa while the remaining two retained their punctured septa. The samples were reanalyzed with fresh standards. Each septum was punctured 6 times for each injection.

Table 4.8.2.5 Stability of Samples for MEK Extracted From Anasorb 747
punctured septa replaced				punctured septa retained
initial (%)	after 12 h (%)	difference (%)		initial (%)	after 12 h (%)	difference (%)
98.5 97.4 98.0	99.0 97.4 mean 98.2	0.5 0.0 0.3		98.9 98.1 98.5	96.0 93.3 mean 94.7	-2.9 -4.8 -3.9

4.8.3 SKC 575-002 Passive Samplers

Extraction efficiency

The extraction efficiencies of MEK and MIBK were determined by liquid spiking SKC 575-002 Passive Samplers with the analytes at concentrations from the RQL to 2 times the target concentration. These samplers were stored overnight at ambient temperature and then analyzed. The mean extraction efficiency over the working range of the RQL to 2 times the target concentration is 92.2% for MEK and 92.9% for MIBK. The extraction efficiency for MEK from wet samplers was lower than for dry samplers. These results were expected because of the instability of MEK on wet sorbents. The extraction efficiency for the wet samplers was not included in the overall mean because it would bias the results.

Table 4.8.3.1 Extraction Efficiency of MEK from SKC 575-002 Passive Samplers (%)
level		sample number
× target concn	µg per sample	1	2	3	4	mean
RQL 0.25 0.5 1.0 1.5 2.0 1.0 (wet)	1.282 594 1188 2375 3800 4750 2375	80.8 92.7 87.4 94.4 89.9 95.1 89.8	101.8 97.2 87.6 92.4 94.1 93.4 85.7	85.5 91.8 90.9 99.4 90.2 91.5 83.7	93.3 95.1 89.3 94.7 95.2 88.5 87.9	90.4 94.2 88.8 95.2 92.4 92.1 86.8

Table 4.8.3.2 Extraction Efficiency of MIBK from SKC 575-002 Passive Samplers (%)
level		sample number
× target concn	µg per sample	1	2	3	4	mean
RQL 0.25 0.5 1.0 1.5 2.0 1.0 (wet)	1.268 325 650 1300 1950 2601 1300	71.6 91.0 94.8 98.2 98.1 98.2 97.0	74.7 92.9 96.6 97.2 97.6 92.1 96.6	94.3 90.0 92.8 99.4 97.0 95.3 97.7	83.3 90.9 94.9 96.0 95.5 97.5 99.5	81.0 91.2 94.8 97.7 97.1 95.8 97.7

Stability of extracted samples

The stability of extracted samples was investigated by reanalyzing the target concentration samples a day after initial analysis. After the original analysis was performed, two vials were recapped with new septa while the remaining two retained their punctured septa. The samples were reanalyzed with fresh standards. Each septum was punctured 6 times for each injection.

Table 4.8.3.3 Stability of Samples for MEK Extracted From SKC 575-002 Passive Samplers
punctured septa replaced				punctured septa retained
initial (%)	after one day (%)	difference (%)		initial (%)	after one day (%)	difference (%)
94.4 92.4 93.4	93.0 92.7 mean 92.9	-1.4 0.3 -0.6		99.4 94.7 97.1	77.2 83.6 mean 80.4	-22.2 -11.1 -16.7

Table 4.8.3.4 Stability of Samples for MIBK Extracted From SKC 575-002 Passive Samplers
punctured septa replaced				punctured septa retained
initial (%)	after one day (%)	difference (%)		initial (%)	after one day (%)	difference (%)
98.2 97.2 97.7	95.3 97.0 mean 96.2	-2.9 -0.2 -1.6		99.4 96.0 97.7	92.8 87.8 mean 90.3	-6.6 -8.2 -7.4

The stability test for MEK was repeated with the reanalysis performed 12 hours after the initial analysis. After the original analysis was performed, two vials were recapped with new septa while the remaining two retained their punctured septa. The samples were reanalyzed with fresh standards. Each septum was punctured 6 times for each injection.

Table 4.8.3.5 Stability of Samples for MEK Extracted From SKC 575-002 Passive Samplers
punctured septa replaced				punctured septa retained
initial (%)	after 12 h (%)	difference (%)		initial (%)	after 12 h (%)	difference (%)
89.7 90.3 90.0	94.6 93.2 mean 93.9	4.9 2.9 3.9		89.7 94.5 92.1	89.6 86.4 mean 88.0	-0.1 -8.1 -4.1

4.8.4 3M 3520 OVM

Extraction efficiency

The extraction efficiencies of MEK and MIBK were determined by liquid-spiking 3M 3520 OVM charcoal wafers with the analytes at concentrations from the RQL to 2 times the target concentration. These samples were stored overnight at ambient temperature and then analyzed. The mean extraction efficiency over the working range of the RQL to 2 times the target concentration is 98.0% for MEK and 96.5% for MIBK. The extraction efficiency for MEK from wet samplers was lower than for dry samplers. These results were expected because of the instability of MEK on wet sorbents. The extraction efficiency for the wet samplers was not included in the overall mean because it would bias the results.

Table 4.8.4.1 Extraction Efficiency of MEK from 3M 3520 OVM Charcoal Wafers (%)
level		sample number
× target concn	µg per sample	1	2	3	4	mean
RQL 0.25 0.5 1.0 1.5 2.0 1.0 (wet)	0.760 1188 2375 4750 7125 9500 4750	108.6 100.1 97.9 96.4 97.1 89.4 88.2	91.7 93.2 102.1 96.8 95.6 98.8 89.3	107.2 92.4 103.8 94.0 100.9 95.7 90.1	113.7 94.7 98.3 95.0 93.9 94.3 91.4	105.3 95.1 100.5 95.6 96.9 94.6 89.8

Table 4.8.4.2 Extraction Efficiency of MIBK from 3M 3520 OVM Charcoal Wafers (%)
level		sample number
× target concn	µg per sample	1	2	3	4	mean
RQL 0.25 0.5 1.0 1.5 2.0 1.0 (wet)	0.943 650 1300 2601 3901 5201 2601	92.0 98.2 97.2 99.7 98.5 100.7 98.7	87.3 96.1 98.7 98.2 101.3 97.2 97.5	84.8 93.2 98.4 96.8 98.3 103.0 93.8	81.5 97.1 98.9 96.2 100.2 101.3 98.1	86.4 96.2 98.3 97.7 99.6 100.6 97.0

Stability of extracted samples

The stability of extracted samples was investigated by reanalyzing the target concentration samples a day after initial analysis. After the original analysis was performed, two vials were recapped with new septa while the remaining two retained their punctured septa. The samples were reanalyzed with fresh standards. Each septum was punctured 6 times for each injection.

Table 4.8.4.3 Stability of Samples for MEK Extracted From 3M 3520 OVM Charcoal Wafers
punctured septa replaced				punctured septa retained
initial (%)	after one day (%)	difference (%)		initial (%)	after one day (%)	difference (%)
96.4 96.8 96.6	97.2 94.3 mean 95.8	0.8 -2.5 -0.9		94.0 95.0 94.5	84.2 77.9 mean 81.1	-9.8 -17.1 -13.5

Table 4.8.4.4 Stability of Samples for MIBK Extracted From 3M 3520 OVM Charcoal Wafers
punctured septa replaced				punctured septa retained
initial (%)	after one day (%)	difference (%)		initial (%)	after one day (%)	difference (%)
99.7 98.2 99.0	99.4 100.1 mean 99.8	-0.3 1.9 0.8		96.8 96.2 96.5	93.8 96.1 mean 95.0	-3.0 -0.1 -1.6

The stability test for MEK was repeated with the reanalysis performed 12 hours after the initial analysis. After the original analysis was performed, two vials were recapped with new septa while the remaining two retained their punctured septa. The samples were reanalyzed with fresh standards. Each septum was punctured 6 times for each injection.

Table 4.8.4.5 Stability of Samples for MEK Extracted From 3M 3520 OVM Charcoal Wafers
punctured septa replaced				punctured septa retained
initial (%)	after 12 h (%)	difference (%)		initial (%)	after 12 h (%)	difference (%)
100.0 103.5 101.8	95.3 94.9 mean 95.1	-4.7 -8.6 -6.7		102.7 103.6 103.2	94.1 94.4 mean 94.3	-8.6 -9.2 -8.9

4.9 Interferences (sampling)

4.9.1 SKC Anasorb CMS sampling tubes

Retention

The ability of SKC Anasorb CMS sampling tubes to retain MEK and MIBK after collection was tested by sampling an atmosphere containing 1178 mg/m³ MEK and 806 mg/m³ MIBK at an absolute humidity of 14.6 milligrams of water per liter of air (77.8% relative humidity at 21.4°C). Six samplers had contaminated air drawn through them at about 50 mL/min for 60 min. Sampling was discontinued and three samples set aside. The generation system was flushed with contaminant-free air. Sampling was resumed with the other three samples with contaminant-free humid air drawn through them at 50 mL/min for 3 h and then all six samplers were analyzed. Recoveries for the two sets are expressed as percent of theoretical.

Table 4.9.1 Retention (%) of MEK and MIBK on Anasorb CMS
	1		2		3		mean
set	MEK	MIBK	MEK	MIBK	MEK	MIBK	MEK	MIBK
first second second/first	96.7 92.2	96.1 93.4	96.2 93.1	94.7 93.4	97.2 91.9	96.5 92.5	96.7 92.4 95.6	95.8 93.1 97.2

Low humidity

The ability of SKC Anasorb CMS sampling tubes to collect MEK and MIBK from a relatively dry atmosphere was tested by sampling an atmosphere containing 1203 mg/m³ of MEK and 823 mg/m³ of MIBK at an absolute humidity of 2.7 milligrams of water per liter of air (13.2% relative humidity at 22.6°C). Three samplers had contaminated air drawn through them at 50 mL/min for 240 min. All three samples were immediately analyzed. The sample results were 96.3%, 97.2% and 95.1% of theoretical for MEK; and 98.6%, 99.3%, and 98.2% of theoretical for MIBK.

Low concentration

The ability of SKC Anasorb CMS sampling tubes to collect MEK and MIBK at low concentrations was tested by sampling an atmosphere containing 60.4 mg/m³ of MEK and 41.3 mg/m³ of MIBK at an absolute humidity of 15.5 milligrams of water per liter of air (79.7% relative humidity at 22.3°C). Three samplers had contaminated air drawn through them at 50 mL/min for 240 min. All three samples were immediately analyzed. The sample results were 94.9%, 98.2% and 97.2% of theoretical for MEK and 101.1%, 104.7% and 104.4% of theoretical for MIBK.

Sampling interferences

The ability of SKC Anasorb CMS sampling tubes to collect MEK and MIBK was tested in the presence of potential interferences by sampling an atmosphere containing 578 mg/m³ of MEK and 395 mg/m³ of MIBK at an absolute humidity of 15.6 milligrams of water per liter of air (79.0% relative humidity at 22.23°C) and 553.3 mg/m³ acetone, 253.7 mg/m³ isopropyl alcohol, 190.1 mg/m³ toluene, 92.5 mg/m³ xylene isomers, and 16.3 mg/m³ ethyl benzene. Three samplers had contaminated air drawn through them at 50 mL/min for 240 min. All three samples were immediately analyzed. The sample results were 99.1%, 99.3% and 99.0% of theoretical for MEK; and 102.2%, 103.0% and 102.4% of theoretical for MIBK.

4.9.2 SKC 575-002 Passive Samplers and 3M 3520 OVMs

Reverse diffusion

The ability of SKC 575-002 Passive Samplers and of 3M 3520 OVMs to retain MEK and MIBK after collection was tested by sampling an atmosphere containing 1178 mg/m³ MEK and 806 mg/m³ MIBK at an absolute humidity of 14.6 milligrams of water per liter of air (77.8% relative humidity at 21.4°C). Six of each sampler were exposed to contaminated air for one hour. Sampling was discontinued and three of each sampler were set aside (1^st set). The generation system was flushed with contaminant-free air. Sampling was resumed with the remaining six samplers exposed to contaminant-free humid air for an additional three hours (2^nd set). Results are presented in terms of micrograms of analyte found on the sampler. The means of the second set were 99.3% for MEK and 100.0% for MIBK of the means of the first set for SKC 575-002 Passive Samplers. The means of the second set were 96.0% for MEK and 98.6% for MIBK of the means of the first set for 3M 3520 OVMs.

Table 4.9.2.1 Reverse Diffusion For SKC 575-002 Passive Sampler (µg)
set	1		2		3
	MEK	MIBK	MEK	MIBK	MEK	MIBK
first second	1357.45 1355.55	741.52 739.86	1368.54 1360.50	732.50 737.37	1405.26 1387.31	753.41 750.30
means
first second	1377.08 1367.79	742.48 742.51

Table 4.9.2.2 Reverse Diffusion For 3M OVM (µg)
set	1		2		3
	MEK	MIBK	MEK	MIBK	MEK	MIBK
first second	2700.73 2580.20	1520.43 1471.29	2627.96 2607.50	1464.63 1510.12	2811.44 2628.50	1535.59 1477.16
means
first second	2713.38 2605.40	1506.88 1486.19

Low humidity

Three SKC and three 3M diffusive samplers were used to sample a test atmosphere containing 1203 mg/m³ MEK and 823 mg/m³ MIBK. The absolute humidity of the test atmosphere was 2.7 milligrams of water per liter of air (13.2% relative humidity at 22.6°C). The recoveries (% theoretical) are shown in Table 4.9.2.3.

Table 4.9.2.3 Low Humidity (Recovery, % of Theoretical)
sampler		1			2			3
		MEK	MIBK		MEK	MIBK		MEK	MIBK
SKC 575-002 3M 3520		92.2 95.5	102.5 109.2		94.9 93.9	104.9 102.6		92.8 92.9	103.1 101.0

Low concentration

Three SKC and three 3M diffusive samplers were used to sample a test atmosphere containing 60.3 mg/m³ MEK and 41.3 mg/m³ MIBK. The absolute humidity of the test atmosphere was 15.5 milligrams of water per liter of air (79.7% relative humidity at 22.3°C). The recoveries (% theoretical) are shown in Table 4.9.2.4.

Table 4.9.2.4 Low Concentration (Recovery, % of Theoretical)
sampler		1			2			3
		MEK	MIBK		MEK	MIBK		MEK	MIBK
SKC 575-002 3M 3520		92.2 89.8	101.6 95.0		95.6 93.4	105.2 97.9		90.3 92.2	96.8 98.5

Sampling interferences

Three SKC and three 3M diffusive samplers were used to sample a test atmosphere containing 578 mg/m³ of MEK and 395 mg/m³ of MIBK; and 553.3 mg/m³ of acetone, 253.7 mg/m³ of isopropyl alcohol, 190.1 mg/m³ of toluene, 92.5 mg/m³ of xylene isomers, and 16.3 mg/m³ of ethyl benzene. The absolute humidity was 15.6 milligrams of water per liter of air (79.0% relative humidity at 22.3°C). The recoveries (% theoretical) are shown in Table 4.9.2.5.

Table 4.9.2.5 Sampling Interference (Recovery, % of Theoretical)
sampler		1			2			3
		MEK	MIBK		MEK	MIBK		MEK	MIBK
SKC 575-002 3M 3520		103.2 95.0	108.5 103.1		97.6 93.6	102.2 101.8		101.6 93.5	107.3 102.8

4.10 Qualitative analysis

The identity of suspected MEK or MIBK GC peaks can be confirmed by GC/Mass Spectrometry. Mass spectra for the analytes are shown below.

Figure 4.10.1 Mass spectrum of MEK.

Figure 4.10.2 Mass spectrum of MIBK