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For problems with accessibility in using figures, illustrations and PDFs in this method, please contact the SLTC at (801) 233-4900.
These procedures were designed and tested for internal use by OSHA personnel. Mention of any company name or commercial product does not constitute endorsement by OSHA.

2,2,4-Trimethyl-1,3-Pentanediol Diisobutyrate

Method number:  PV2002
 
Control number:  T-PV2002-01-9912-M
 
Target concentration: 100 ppm (1170 mg/m)
 
Procedure: Samples are collected by drawing a known volume of air through glass sampling tubes containing Chromosorb 106. Samples are extracted with carbon disulfide and analyzed by GC using a flame ionization detector.
 
Recommended sampling time and sampling rate: 100 min at 0.1 L/min (10 L)
 
Reliable quantitation limit: 11.3 ppb
 
Status of method: Partially evaluated method. This method has been subjected to established evaluation procedures of the Methods Development Team and is presented for information and trial use.
 
Date: December 1999
 
Chemist:

Mary E. Eide



Methods Development Team
Industrial Hygiene Chemistry Division
OSHA Salt Lake Technical Center
Salt Lake City UT 84115-1802

1. General Discussion
1.1 Background
1.1.1 History

Air samples were received at SLTC collected on Chromosorb 106 tubes requesting analysis for 2,2,4-trimethyl-1,3-pentanediol diisobutyrate. Analysis by gas chromatography with a flame ionization detector was chosen, because this compound is a liquid at room temperature. Carbon disulfide was selected for the extraction solvent and was found to give an extraction efficiency of 100.1%. The analyte was found to be well retained on the Chromosorb 106 tubes, with a retention efficiency recovery of 100.4% and the storage stability recovery of 99.5% on Day 14 of ambient storage. Along with these studies, charcoal tubes were also explored. The extraction efficiency on charcoal tubes using carbon disulfide as a solvent showed non-linear extraction, with an extraction efficiency of 98.1% for a loading of 23.34 mg to 88.6% for a loading of 1.167mg. The extraction efficiency with 99:1 carbon disulfide:dimethyl formamide averaged 100.8% over the range of 1.167 to 23.34 mg. The retention efficiency averaged 99.8%. The storage at ambient temperature was 98.2% on Day 14, indicating that charcoal tubes are a good alternative to the Chromosorb 106 tubes.

1.1.2 Toxic effects (This section is for information only and should not be taken as the basis of OSHA policy.)1

2,2,4-Trimethyl-1,3-pentandiol diisobutyrate is a contact irritant affecting the skin and mucous membrane.

1.1.3 Workplace exposure2,3

2,2,4-Trimethyl-1,3-pentanediol diisobutyrate is used as an intermediate in the manufacture of plasticizers, surfactants, pesticides, and resins. It is used as a viscosity control agent in plastisol, rotomolding, and rotocasting operations. It is used in the production of vinyl flooring as a hardening agent. Production exceeds one million pounds annually.

1.1.4 Physical properties and other descriptive information4

CAS number: 6846-50-0    
RTECS number: SA1420000 molecular weight: 286.41
melting point: -70 C boiling point: 280 C
appearance: clear liquid molecular formula: C16H30O4
odor: musty flash point: 109 C (230 F)(cc)
auto ignition   density: 0.941
temperature: 423 C    
synonyms: Isobutyric acid, 1-isopropyl-2,2-dimethyltrimethyl ester; Kodaflex TXIB; 2,2,4-trimethylpentanediol-1,3-diisobutyrate; TXIB
solubility: acetone, alcohol, benzene, and carbon tetrachloride
IMIS:5 T350    
structural formula: structural formula. For problems with accessibility in using figures, illustrations and PDFs in this method, please contact the SLTC at (801) 233-4900.

This method was evaluated according to the OSHA SLTC Evaluation Guidelines for Air Sampling Methods Utilizing Chromatographic Analysis6. The Guidelines define analytical parameters, specify required laboratory tests, statistical calculations and acceptance criteria. The analyte air concentrations throughout this method are based on the recommended sampling and analytical parameters.
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 10.35 g of 2,2,4- trimethyl-1,3-pentanediol diisobutyrate. This is the amount spiked on a sampler that would produce a peak approximately 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 and slope) for the calculation of the DLOP. The slope was 770.3 and the SEE was 101.8. 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 0.397g and 1.32 g respectively.


Table 1.2
Detection Limit of the Overall Procedure for 2,2,4-Trimethyl-1,3-pentanediol diisobutyrate

mass per sample
(g)
area counts
(V-s)

0.00
1.04
2.07
3.11
4.14
5.18
6.21
7.25
8.28
9.32
10.35
0
638
1368
2265
3170
3966
4640
5620
6409
7029
7767
Figure 1.2. Plot of data to determine the DLOP/RQL for 2,2,4-trimethyl-1,2-pentandiol diisobutyrate. (Y = 770X - 90.8). For problems with accessibility in using figures, illustrations and PDFs in this method, please contact the SLTC at (801) 233-4900.  
Figure 1.2.1. Plot of data to determine the DLOP/RQL for 2,2,4-trimethyl-1,2-pentandiol diisobutyrate. (Y = 770X - 90.8)

Below are chromatograms of the RQL level.

Figure 1.2.1 Chromatogram of the RQL of 2,2,4-trimethyl-1,3-pentanediol diisobutyrate. (1 = carbon disulfide; 2 = benzene (contaminant in the carbon disulfide); 3 = p-cymene; and 4 = 2,2,4-trimethyl-1,3-pentanediol diisobutyrate). For problems with accessibility in using figures, illustrations and PDFs in this method, please contact the SLTC at (801) 233-4900. Figure 1.2.2 Chromatogram of the 2,2,4-trimethyl-1,3-pentanediol diisobutyrate peak in the standard near the RQL.
Figure 1.2.2. Chromatogram of the RQL of 2,2,4-trimethyl-1,3-pentanediol diisobutyrate. (1 = carbon disulfide; 2 = benzene (contaminant in the carbon disulfide); 3 = p-cymene; and 4 = 2,2,4-trimethyl-1,3-pentanediol diisobutyrate) Figure 1.2.3. Chromatogram of the 2,2,4-trimethyl-1,3-pentanediol diisobutyrate peak in the standard near the RQL.
2. Sampling Procedure

All safety practices that apply to the work area being sampled should be followed. The sampling equipment should be attached to the worker in such a manner that it will not interfere with work performance or safety.

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 (100/50 mg) of Chromosorb 106. The sections are held in place and separated with a glass wool plug and two urethane foam plugs. For this evaluation, commercially prepared sampling tubes were purchased from SKC, Inc. (catalog no. 226- 110).
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 sampler 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 (mL/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 Chromosorb 106 with 2,2,4-trimethyl- 1,3-pentandiol diisobutyrate 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 100.1%. The wet extraction efficiency was determined at 1 times the target concentration by liquid spiking the analyte onto Chromsorb 106 tubes which had 10-L humid air (absolute humidity of 15.9 mg/L of water, about 80% relative humidity at 22.2C) drawn through them immediately before spiking. The mean recovery for the wet samples was 99.8%.


Table 2.4
Extraction Efficiency (%) of 2,2,4-Trimethyl-1,3-pentandiol diisobutyrate

level sample number
target
concn
mg per
sample
1 2 3 4 5 6 mean

0.1
0.25
0.5
1.0
1.5
2.0

1.0 (wet)
1.17
2.92
5.83
11.7
17.5
23.3

11.7
97.4
99.9
99.3
100.9
100.1
99.2

99.8
100.0
100.4
99.2
101.2
100.4
100.3

100.1
101.6
100.8
99.7
102.0
99.5
98.7

99.1
99.6
99.7
100.5
101.8
99.3
100.2

100.4
100.6
100.4
100.0
98.9
99.9
100.1

99.5
99.6
100.3
101.4
99.1
100.1
99.9

99.9
99.8
100.3
100.0
100.7
99.9
99.7

99.8

2.5 Retention efficiency

Six Chromosorb 106 tubes were spiked with 23.34 mg (199.2 ppm) of 2,2,4-trimethyl-1,3- pentanediol diisobutyrate and allowed to equilibrate for 6 h. The tubes had 10 L humid air (absolute humidity of 15.9 mg/L of water, about 80% relative humidity at 22.2C) pulled through them at 0.1 L/min. The samples were extracted and analyzed. The mean recovery was 100.4%. There was no analyte found on the backup section of any of the tubes.


Table 2.5
Retention Efficiency (%) of 2,2,4-Trimethyl-1,3-pentandiol diisobutyrate

  sample number
section 1 2 3 4 5 6 mean

front
rear
total
100.8
0.0
100.8
100.4
0.0
100.4
99.1
0.0
99.1
102.1
0.0
102.1
100.5
0.0
100.5
99.5
0.0
99.5
100.4
0.0
100.4

2.6 Sample storage

Nine Chromosorb 106 tubes were each spiked with 11.67 mg (99.62 ppm) of 2,2,4-trimethyl-1,3- pentanediol diisobutyrate. They were allowed to equilibrate for 6 h, then 10 L of air, with an absolute humidity of 15.7 milligrams of water per liter of air (about 80% relative humidity at 22.2C), 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. The amounts recovered, which are corrected for extraction efficiency, indicate good storage stability for the time period studied.


Table 2.6
Storage Test for 2,2,4-Trimethyl-1,3-pentandiol diisobutyrate (% Recovery)

sample number
time (days) 1 2 3 mean

0
7
14
100.9
98.0
99.6
101.2
99.1
99.6
101.2
99.1
99.6
100.3
98.6
99.5

2.7 Recommended air volume and sampling rate.

Based on the data collected in this evaluation, 10-L air samples should be collected at a sampling rate of 0.1 L/min for 100 minutes.

2.8 Interferences (sampling)
2.8.1 There are no known compounds which will severely interfere with the collection of 2,2,4- trimethyl-1,3-pentanediol diisobutyrate.

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

Adhere to the rules set down in your Chemical Hygiene Plan. Avoid skin contact and inhalation of all chemicals and review all appropriate MSDSs.

3.1 Apparatus
3.1.1 A gas chromatograph equipped with an FID. For this evaluation, a Hewlett-Packard 5890A Series II Gas Chromatograph equipped with a 7673A Automatic Sampler was used.

3.1.2 A GC column capable of separating 2,2,4-trimethyl-1,3-pentanediol diisobutyrate from the desorption solvent, internal standard and any potential interferences. A 60-m 0.32-mm i.d. capillary DB-WAX with a 0.5-m df (J&W Scientific, Folsom, CA) was 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 2-mL vials were used.

3.1.5 A dispenser capable of delivering 1.0 mL of desorbing solvent to prepare standards and samples. If a dispenser is not available, a 1.0-mL volumetric pipet may be used.

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

3.1.8 Calibrated 10-L syringe for preparing standards.
3.2 Reagents
3.2.1 2,2,4-Trimethyl-1,3-pentandiol diisobutyrate, Reagent grade. Aldrich 99% (lot 08515DS) was used in this evaluation.

3.2.2 Carbon disulfide, Reagent grade. Omni-Solv 99.99% (lot 34279) was used for this evaluation.

3.2.3 p-Cymene, Reagent grade. Aldrich 99% (lot 11703TR) was used in this evaluation.

3.2.4 The extraction solvent was 0.25 L/mL p-cymene in carbon disulfide.

3.2.5 GC grade nitrogen, air, and hydrogen.
3.3 Standard preparation
3.3.1 Prepare working analytical standards by injecting microliter amounts of 2,2,4-trimethyl-1,3- pentanediol diisobutyrate into volumetric flasks containing the extraction solvent. An analytical standard at a concentration of 11.67 mg/mL (12.4 L/mL) is equivalent to 99.61 ppm based on a 10-liter air volume.

3.3.2 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 extracting solvent to obtain a concentration within the existing standard range. The range of standards used in this study was from 0.001 to 28.23 mg/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 2-mL vials. Discard the glass tube, urethane foam plug and glass wool plug.

3.4.2 Add 1.0 mL of extraction solvent 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 vigorously by hand several times during the next 30 minutes.
3.5 Analysis
3.5.1 Gas chromatograph conditions.

GC conditions:
zone temperatures: 100C (column), hold 2 min, ramp at 10C/min to 180C, hold 10 min 250C (injector) 250C (detector)
run time: 20 min
column gas flow: 2.9 mL/min (hydrogen)
septum purge 1.9 mL/min (hydrogen)
injection size: 1.0 L (19:1 split)
column: 60-m 0.32-mm i.d. capillary DB-WAX (0.5-m df)
retention times: 3.98 min (carbon disulfide); 4.61 min (benzene contaminate in the carbon disulfide); 7.41 min (p-cymene); 18.01 min (2,2,4-trimethyl-1,3-pentanediol diisobutyrate)
FID conditions:
hydrogen flow: 38 mL/min
air flow: 450 mL/min
makeup flow: 30 mL/min (nitrogen)

Figure 3.5.1. A chromatogram of 941 g/mL 2,2,4-trimethyl-1,3-pentanediol diisobutyrate in carbon disulfide with 0.25 L/mL internal standard. Key: (1) carbon disulfide; (2) benzene contaminant in the carbon disulfide; (3) p-cymene; (4) 2,2,4-trimethyl-1,3-pentanediol diisobutyrate. For problems with accessibility in using figures, illustrations and PDFs in this method, please contact the SLTC at (801) 233-4900.
Figure 3.5.1. A chromatogram of 941 g/mL 2,2,4-trimethyl-1,3-pentanediol diisobutyrate in carbon disulfide with 0.25 L/mL internal standard. Key: (1) carbon disulfide; (2) benzene contaminant in the carbon disulfide; (3) p-cymene; (4) 2,2,4-trimethyl-1,3-pentanediol diisobutyrate.

3.5.2 Peak areas are measured by an integrator or other suitable means.

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


Figure 3.5.3. Calibration curve of 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (Y = 3.34E5 + 5808). For problems with accessibility in using figures, illustrations and PDFs in this method, please contact the SLTC at (801) 233-4900.
Figure 3.5.3. Calibration curve of 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (Y = 3.34E5 + 5808).
3.6 Interferences (analytical)
3.6.1 Any compound that produces a GC 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 mass spectrometry or by another analytical procedure. The mass spectrum in Figure was from the NIST spectral library.


Figure 3.6.2. The mass spectrum of 2,2,4-trimethyl-1,3-pentanediol diisobutyrate . For problems with accessibility in using figures, illustrations and PDFs in this method, please contact the SLTC at (801) 233-4900.
Figure 3.6.2. The mass spectrum of  2,2,4-trimethyl-1,3-pentanediol diisobutyrate.
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.


CM = M

VEE
where  CM is concentration by weight (mg/m)
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 1 atm = 24.46
CM is concentration by weight
Mr is molecular weight = 286.41
4. Recommendations for Further Study

Collection, reproducibility, and other detection limit studies need to be performed to make this a validated method.



1 Lewis, R, Sax's Dangerous Properties of Industrial Materials, Van Nostrand Reinhold: New York, 1992, p. 3415.

2 Howe-Grant, M., Kroschwitz, J., Ed, Encyclopedia of Chemical Technology, John Wiley & Sons: New York, 1992, vol 4 p. 741.

3 Environmental Defense Fund. http: www.scorecard.org/chemical-profiles/summary.tcl?edf_substance_id=6846-50-0 (accessed 11/16/99).

4 Material Safety Data Sheet: 2,2,4-trimethyl-1,3-pentandiol diisobutyrate, Aldrich Chemical Co., Milwaukee, WI, Oct. 1999.

5 OSHA Chemical Sampling Information. http://www.osha.gov/ChemSamp_data/CH_273990.html (accessed 11/17/99).

6 Burright, D.; Chan, Y.; Eide, M.; Elskamp, C.; Hendricks, W.; Rose, M. C. EVALUATION GUIDELINES FOR AIR SAMPLING METHODS UTILIZING CHROMATOGRAPHIC ANALYSIS; OSHA Salt Lake Technical Center, U.S. Department of Labor: Salt Lake City, UT, 1999.


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