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Related Information: Chemical Sampling - Resorcinol

Method number: PV2053
 
Matrix: Air
 
Target concentration: 10 ppm (45 mg/m3) OSHA TWA PEL
20 ppm (90 mg/m3) OSHA STEL
(Note: These are the 1989 levels which have subsequently been rescinded.)
 
Procedure: Samples are collected by drawing a known volume of air through an OVS-7 tube. Samples are desorbed with methanol and analyzed by gas chromatography with a flame ionization detector (GC-FID).
 
Air volume and sampling rate studied: 60 liters at 1.0 Lpm
 
Status of method: Stopgap method. This method has been only partially evaluated and is presented for information and trial use.
 
Date: March, 1992
Revised: March, 1994
Chemist: Mary E. Eide

Organic Service Branch I
OSHA Salt Lake Technical Center
Salt Lake City, Utah 84115-1802

1. General Discussion

1.1. Background

1.1.1. History of procedure

The OSHA Technical Center has received many requests for a sampling and analytical procedure for resorcinol. OSHA promulgated an exposure standard for resorcinol in January, 1989, at a level of 10 ppm TWA, and 20 ppm STEL. OSHA method 32 recommends collection of phenol and cresol on XAD-7 tubes and desorption with methanol (Ref. 5.1.). Resorcinol is related to these compounds, and resorcinol occurs as a particulate as well as a vapor, so an OVS-7 tube was tried. An OVS-7 tube is a glass fiber filter in front of a 270 mg section of XAD-7 resin followed by a 140 mg section of XAD-7 resin. The desorption, retention and storage studies all had good recoveries.

1.1.2. Potential workplace exposure (Ref. 5.2.)

Resorcinol is used in the tanning and dyeing industries; in the manufacture of resins and resin adhesives, explosives, hexyl resorcinol, p-aminosalicylic acid, cosmetics, and as an antiseptic and topical antipruritic.

1.1.3. Toxic Effects (This section is for information purposes and should not be taken as the basis for OSHA policy.)(Ref. 5.3.)

Resorcinol is a skin, eye, and mucous membrane irritant. Exposure to resorcinol causes, with increasing exposure, skin burns, cyanosis, methemoglobinemia, convulsions, and death. It was found to be less toxic than phenol, but with similar toxic effects.

1.1.4. Physical properties (Ref. 5.2.):

Compound: molecular structure
Synonyms: 1,3-Benzenediol; Resorcin; m-Dihydroxybenzene; C.I. 76505; C.I. Developer 4; C.I. Oxidation base 31; Developer O; Developer R; Developer RS; Fouramine RS; Durafur developer G; Fourrine 79; Fourrine EW; m-Hydroquinone; 3-Hydroxycyclohexadiene-l-one; m-Hydroxyphenol
Molecular weight:     110.11
Melting point: 110°C
Boiling point: 280°C
Flash point: 127°C (261°F)(closed cup)
Odor: phenolic
Color: white, turns pink on exposure to light or air
Molecular formula: C6H6O2
CAS: 108-46-3
IMIS: 2221
RTECS: VG962500; 76367
DOT: UN2876 (Poison)

1.2. Limit defining parameters

1.2.1. The detection limit of the analytical procedure is 8 µg resorcinol. This is the smallest amount that could be detected under normal operating conditions.

1.2.2. The overall detection limit is 0.0889 ppm. (All ppm amounts in this study are based on a 20 L air volume.)

1.3. Advantages

1.3.1. The sampling procedure is convenient.

1.3.2. The analytical method is reproducible and sensitive.

1.3.3. Reanalysis of samples is possible.

1.3.4. It may be possible to analyze other compounds at the same time.

1.3.5. Interferences may be avoided by proper selection of column and GC parameters.

1.4. Disadvantages

none known

2. Sampling procedure

2.1. Apparatus

2.1.1. A calibrated personal sampling pump, the flow of which can be determined within ± 5% at the recommended flow.

2.1.2. An OVS-7 tube is a 13 mm glass fiber filter in front of a 270 mg section of XAD-7 resin followed by a 140 mg section of XAD-7 resin 15/50 mesh, with foam plugs before and after the back XAD-7 section. The ends are sealed with plastic caps.

2.2. Sampling technique

2.2.1. Open the ends of the OVS-7 tubes immediately before sampling.

2.2.2. Connect OVS-7 tubes to the sampling pump with flexible tubing.

2.2.3. Place the tubes in a vertical position to minimize channeling, with the smaller section towards the pump.

2.2.4. Air being sampled should not pass through any hose or tubing before entering the OVS-7 tubes.

2.2.5. Seal the OVS-7 tubes with plastic caps immediately after sampling. Seal each sample lengthwise with OSHA Form-21 sealing tape.

2.2.6. With each batch of samples, submit at least one blank tube from the same lot used for samples. This tube should be subjected to exactly the same handling as the samples (break ends, seal, & transport) except that no air is drawn through it.

2.2.7. Transport the samples (and corresponding paperwork) to the lab for analysis.

2.2.8. Bulks submitted for analysis must be shipped in a separate container from other samples.

2.3. Desorption and Extraction efficiency

2.3.1. Six glass fiber filters were spiked at loadings of 0.298 mg (1.10 ppm), 1.49 mg (5.51 ppm), 2.98 mg (11.0 ppm), and 5.96 mg (22.1 ppm) resorcinol. They were allowed to equilibrate overnight at room temperature. They were opened, desorbed with 2 mL of methanol for 30 minutes with shaking, and analyzed by GC-FID. The overall average was l00%. (Table 1)

Table 1
Extraction Efficiency of Glass Fiber Filters

Filter# % Recovered
0.298 mg 1.49 mg 2.98 mg 5.96 mg

1 102 96.8 99.3 99.6
2 98.9 99.4 98.8 100
3 102 96.8 102 98.8
4 101 101 98.9 99.8
5 97.6 103 99.8 102
6 102 103 100 100
average 101 100 99.8 100
overall average 100
standard deviation ± 1.78

2.3.2. Six front portions of XAD-7 resin from the OVS-7 tubes were spiked at loadings of 89.9 µg (0.333 ppm), 450 µg (1.67 ppm), and 899 µg (3.33 ppm) resorcinol. They were allowed to equilibrate overnight at room temperature. They were opened, each section placed into a separate 2 mL vial, desorbed with 2 mL of methanol for 30 minutes with occasional shaking, and analyzed by GC-FID. The overall average was 100%. (Table 2)

Table 2
Desorption Efficiency of XAD-7

Tube# % Recovered
89.9 µg 450 µg 899 µg

1 101 98.3 100
2 98.0 96.8 101
3 99.4 100 102
4 102 101 99.2
5 97.3 102 99.6
6 102 102 101
average 100 100 100
overall average 100
standard deviation ± 1.71

2.4. Retention efficiency

Nine OVS-7 tubes had the glass fiber filter (GFF) removed and placed above the Teflon spacer 1/2" above the front XAD-7 resin section. The glass fiber filters were liquid spiked with 5.96 mg (22.1 ppm) resorcinol, allowed to equilibrate overnight, and then six tubes had 60 liters humid air (91% RH at 22°C) and three had 180 liters humid air (87% RH at 21°C) pulled through them. They were opened, desorbed and analyzed by GC-FID. The retention efficiency averaged 99.7%. There was no resorcinol found on the backup portions of the tubes. (Tables 3 and 4)

Table 3
Retention Efficiency with 60 liters Humid Air

Tube # % Recovered % Recovered % Recovered Total
GFF Front XAD-7 Back XAD-7

1 96.9 2.4 0.0 99.3
2 98.6 2.6 0.0 101
3 94.1 5.7 0.0 99.8
4 96.8 2.8 0.0 99.6
5 95.6 2.9 0.0 98.5
6 97.5 2.4 0.0 99.7
average 99.7


Table 4
Retention Efficiency with 180 liters Humid Air

Tube # % Recovered % Recovered % Recovered Total
GFF Front XAD-7 Back XAD-7

1 91.8 7.8 0.0 99.6
2 92.0 7.4 0.0 99.4
3 93.0 7.2 0.0 100
average 99.7

2.5. Storage

Tubes were spiked with 899 µg (9.98 ppm) resorcinol and stored at room temperature until opened and analyzed. Since resorcinol may decompose in light, half of the tubes were stored under room light, and half were stored in darkness. The samples were found to be stable, for the 14 days stored, under both conditions. The recoveries averaged 98.5%. (Table 5)

Table 5
Storage Study

Day % Recovered light % Recovered dark

7 101 101
7 98.1 96.1
7 lost 99.0
14 102 98.5
14 97.9 94.7
14 101 94.2
overall average 98.5

2.6. Precision

The precision was calculated using the area counts from six injections of each standard at concentrations of 89.9, 450, 899, and 1798 µg/mL resorcinol in the desorbing solution. The pooled coefficient of variation was 0.00924. (Table 6)

Table 6
Precision Study

Injection
Number 89.9 µg/mL 450 µg/mL 899 µg/mL 1798 µg/mL

1 15459 84017 157575 300122
2 15037 84092 157999 298006
3 15436 83171 156893 300985
4 15610 82527 158541 298940
5 15068 82572 156349 299382
6 15323 82670 158489 300375
Average 15322 83175 157641 299635
Standard
Deviation ± 228 720 882 1078
CV 0.0149 0.00866 0.00560 0.00360
Pooled CV 0.00924

where:

formula for pooled coefficient of variation

A(1), A(2),A(3),A(4) = # of injections at each level
CVl, CV2, CV3, CV4 = Coefficients at each level

2.7. Air volume and sampling rate studied

2.7.1. The air volume studied is 60 liters.

2.7.2. The sampling rate studied is 1.0 liters per minute.

2.8. Interferences

Suspected interferences should be listed on sample data sheets.

2.9. Safety precautions

2.9.1. Sampling equipment should be placed on an employee in a manner that does not interfere with work performance or safety.

2.9.2. Safety glasses should be worn at all times in designated areas.

2.9.3. Follow all safety practices that apply to the workplace being sampled.

3. Analytical method

3.1. Apparatus

3.1.1. Gas chromatograph equipped with a flame ionization detector. A HP5890 gas chromatograph was used in this study.

3.1.2. GC column capable of separating the analyte and an internal standard from any interferences. The column used in this study was a 30 meter DB-225 capillary column, 0.25 µ d.f., 0.32 mm I.D. An alternate column is a 60 meter DB-1 capillary column, 1.0 µ d.f., 0.32 mm I.D.

3.1.3. An electronic integrator or some other suitable method of measuring peak areas.

3.1.4. Two milliliter vials with Teflon-lined caps.

3.1.5. A 10 µL syringe or other convenient size for sample injection.

3.1.6. Pipets for dispensing the desorbing solution. The Glenco 1 mL dispenser was used in this method.

3.1.7. Volumetric flasks - 5 mL and other convenient sizes for preparing standards.

3.2 Reagents

3.2.1. Purified GC grade nitrogen, hydrogen, and air.

3.2.2. Resorcinol, Reagent grade

3.2.3. Methanol, HPLC grade

3.2.4. Dimethyl formamide, Reagent grade

3.2.5. Desorbing solution is methanol with 1 µL/mL dimethyl formamide used as an internal standard.

3.3. Sample preparation

3.3.1. Sample tubes are opened and the glass fiber filter, front, and back sections of each tube are placed in separate 4 mL vials. If particulate analysis is not desired the glass fiber filter is added to the vial containing the front section.

3.3.2. Each section is desorbed with 2 mL of the desorbing solution.

3.3.3. The vials are sealed immediately and allowed to desorb for 30 minutes with occasional shaking.

3.3.4. An aliquot was removed and placed into 2 mL vials for analysis with the autosampler. This step may not be necessary, depending on the type of instrumentation used for analysis.

3.4. Standard preparation

3.4.1. Standards are prepared by diluting a known quantity of resorcinol with the desorbing solution.

3.4.2. At least two separate stock standards should be made, and dilutions bracketing the samples are prepared. In this study, the analytical standards ranged from 8 to 5960 µg/mL resorcinol in the desorbing solution.

3.5. Analysis

3.5.1. Gas chromatograph conditions DB-225 capillary column.

Flow rates (mL/min) Temperature (°C)
Nitrogen(makeup) :30 Injector :240
Hydrogen(carrier) :1.5 Detector :240
Air :450 Column :110°-1 min
Hydrogen(detector) :30 4°C/min-160°C
Injection size :1 µL
Elution time :22.566 min
Chromatogram :(See Figure 1)

3.5.2. Gas chromatograph conditions DB-1 capillary column.

Flow rates (mL/min) Temperature (°C)
Nitrogen(makeup) :30 Injector :220
Hydrogen(carrier) :1.5 Detector :240
Air :450 Column :80°-0 min
Hydrogen(detector) :30 10°C/min-220°C
Injection size :1 µL
Elution time :14.077 min
Chromatogram :(See Figure 2)

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

3.6. Interferences (analytical)

3.6.1. Any compound having the general retention time of the analyte or the internal standard used is an interference. Possible interferences should be listed on the sample data sheet. GC parameters should be adjusted if necessary so these interferences will pose no problems.

3.6.2. Retention time data on a single column is not considered proof of chemical identity. Samples over the target concentration should be confirmed by GC/Mass Spec or other suitable means.

3.7. Calculations

3.7.1. A curve with area counts versus concentration is calculated from the calibration standards.

3.7.2. The area counts for the samples are plotted with the calibration curve to obtain the concentration of resorcinol in solution.

3.7.3. To calculate the concentration of analyte in the air sample the following formulas are used:

(µg/m) (desorption volume)
(desorption efficiency)
= mass of analyte in sample

(mass of analyte in sample)
molecular weight
= number of moles of analyte

(number of moles of analyte) (molar volume at 25°C & 760mm) = volume the analyte will occupy at 25°C & 760mm

(volume analyte occupies) (106)*
(air volume)
= ppm

* All units must cancel.

3.7.4. The above equations can be consolidated to form the following formula. To calculate the ppm of analyte in the sample based on a 20 liter air sample:

(µg/mL)(DV)(24.45)(106)
(60 L)(DE)(MW)
× (g)
(1000 mg)
× (mg)
(1000 µg)
= ppm

µg/mL = concentration of analyte in sample or standard
24.45 = Molar volume (liters/mole) at 25° and 760 mm Hg.
MW = Molecular weight (g/mole)
DV = 2 mL Desorption volume
60 L = 10 liter air sample
DE = Desorption efficiency

3.7.5. This calculation is done for each section of the sampling tube and the results added together.

3.8. Safety precautions

3.8.1. All handling of solvents should be done in a hood.

3.8.2. Avoid skin contact with all chemicals.

3.8.3. Wear safety glasses, gloves and a lab coat at all times.

4. Recommendations for further study

A collection study should be performed.

An analytical standard of 450 µg/mL resorcinol in methanol with 1 µL/mL dimethyl formamide internal standard

Figure 1. An analytical standard of 450 µg/mL resorcinol in methanol with 1 µL/mL dimethyl formamide internal standard.

An analytical standard of 450 µg/mL resorcinol in methanol with 1 µL/mL dimethyl formamide internal standard

Figure 2. An analytical standard of 450 µg/mL resorcinol in methanol with 1 µL/mL dimethyl formamide internal standard.

5. References

5.1. Cummins,K., Method 32, "Phenol and Cresol", Organic Methods Evaluation Branch, OSHA Salt Lake Technical Center, 1986.

5.2. Windholz, M., "The Merck Index", Eleventh Edition, Merck & Co., Rahway N.J., 1989, p. 1176.

5.3. "Documentation of the Threshold Limit Values and Biological Exposure Indices", Fifth Edition, American Conference of Governmental Industrial Hygienists Inc., Cincinnati, OH, 1986, p. 511.