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Related Information: Chemical Sampling - m-Xylene-a,a'-Diamine, p-Xylene-a,a'-Diamine
Organic Methods Evaluation Branch1. General Discussion
OSHA Salt Lake Technical Center
Salt Lake City, UT 84165-0200
There were no methods found in the literature for the determination of airborne levels of xylylenediamines. Sampling procedures evaluated at the OSHA Salt Lake Technical Center (SLTC) for a number of other aromatic amines involve collection with sulfuric acid-treated glass fiber filters. (Refs. 5.1-5.7) For those amines where the target concentrations were in the ppb range, quantitation was performed by analyzing the heptafluorobutyric acid anhydride derivatives by gas chromatography using an electron capture detector in order to achieve high sensitivities. Before the derivatization step is performed, the free amines are extracted from an aqueous system into toluene. Extraction of the xylylenediamines into toluene proved to be impossible because they are too water soluble. Analysis was thus performed by HPLC using paired-ion chromatography. Adequate sensitivity was obtained using an ultraviolet detector. Ion-pairing is necessary because the polar analytes are not otherwise sufficiently retained. A column designed for analysis of basic compounds proved useful in producing symmetrical peaks.
A target concentration of 0.1 mg/m3 with a 15-minute ceiling was chosen for both analytes because of the ACGIH TLV for m-xylene- α, α'-diamine (mXDA). (Ref. 5.8) The analytical procedure has adequate sensitivity for 15-minute samples (15-L, 1 L/min), but if desired, long-term sampling can be also done because the sampler has ample capacity. Samples are stable for at least 15 days, even when stored at room temperature.
1.1.2 Toxic effects (This section is for information only and should not be taken as the basis of OSHA policy.)
Both mXDA and pXDA are harmful if swallowed, inhaled, or absorbed through the skin. They are extremely destructive to tissue of the mucous membranes and upper respiratory tract, eyes and skin. Symptoms of exposure may include burning sensation, coughing, wheezing, laryngitis, shortness of breath, headache, nausea and vomiting.
The following paragraphs are taken directly from the ACGIH Documentation of the Threshold Limit Values concerning the TLV for mXDA. (Ref. 5.8)
Two studies have indicated mXDA to have a rather low oral acute toxicity to the rat (1500 and 930 mg/kg, respectively), however to be strongly irritating to the skin. A dermal LD50 of 2000 mg/kg was found for rabbits. The undiluted compound was corrosive to the skin of guinea pigs, and a 50% emulsion in an acetone-dioxane mixture was severely irritating, but little effect was produced by a concentration of 10%. A 10% aqueous solution, however, caused severe erythema and irritation, yet repeated application of a 5% concentration was needed to produce swelling and redness.
In one study evidence of mild sensitization was found following repeated application to guinea pig skin, but this finding was not duplicated in the second investigation.
Exposure of rats for one hour to an aerosol of mXDA, at measured concentrations ranging from 1.74 to 6.04 mg/liter, resulted in eye irritation, lacrimation and labored breathing. No deaths occurred during exposure, but several animals died within 48 hours, and a few more later, up to 14 days, the end of the observation period. Of the animals which survived, female rats showed reduced weight gain, while that of males was near normal.
At necropsy macroscopic abnormalities were found chiefly in the lungs, however changes in liver and kidneys were also noted. The LC50 for a one-hour exposure and 14-day observation period was 3.75 mg/L, or about 700 ppm.
In comparison with the better known phenylene diamine (q.v.), the dermal effects of mXDA seem similar, but the oral toxicity appears less. By analogy, a ceiling limit of 0.1 ppm [sic], with a skin notation, is retained for the present, however, the Committee is currently reviewing this compound. At this concentration, the compound should be largely in the vapor state.
1.1.3 Workplace exposure
mXDA is used to make polyamide fibers and resins and as a curing agent for epoxy resins. It is also a source of m-xylene diisocyanate. (Refs. 5.8, 5.11) It is assumed that pXDA can be used similarly in industry. In one case an experimental nylon derived from pXDA was tested to improve the flat spotting performance of bias and bias-belted tires. (Ref. 5.12)
1.1.4 Physical properties (Ref. 5.9-5.10)
The analyte air concentrations throughout this method are based on the recommended sampling and analytical parameters.
1.2.1 Detection limit of the analytical procedure
The detection limits of the analytical procedure are 24.4 and 30.7 pg for mXDA and pXDA respectively. These are the amounts of each analyte that will give responses that are significantly different from the background response of a reagent blank. (Sections 4.1 and 4.2)
1.2.2 Detection limit of the overall procedure
The detection limits of the overall procedure are 4.1 ng per sample (0.27 µg/m3) and 5.0 ng per sample (0.33 µg/m3) for mXDA and pXDA respectively. These are the amounts of each analyte spiked on the sampler that will give responses that are significantly different from the background response of a sampler blank. (Sections 4.1 and 4.3)
1.2.3 Reliable quantitation limit
The reliable quantitation limits are 13.6 ng per sample (0.91 µg/m3) and 16.8 ng per sample (1.12 µg/m3) for mXDA and pXDA respectively. These are the amounts of each analyte spiked on a sampler that will give signals that are considered the lower limits for precise quantitative measurements. (Section 4.4)
1.2.4 Precision (analytical procedure)
The precisions of the analytical procedure, measured as the pooled relative standard deviations over a concentration range equivalent to 0.5 to 2 times the target concentration, are 0.37% and 0.93% for mXDA and pXDA respectively. (Section 4.5)
1.2.5 Precision (overall procedure)
The precision of the overall procedure at the 95% confidence level for the ambient temperature 15-day storage test (at the target concentration) is ±10.0% for both mXDA and pXDA. (Section 4.6). These include an additional 5% for sampling error.
The recovery of analyte from samples used in a 15-day storage test remained above 95% and 97% for mXDA and pXDA respectively when the samples were stored at ambient temperatures. (Section 4.7)
Six samples spiked by liquid injection, with a draft copy of this procedure, were submitted to an SLTC service branch for analysis. The samples were analyzed after nine days of storage at 0°C. No individual sample result deviated from its theoretical value by more than the precision reported in Section 1.2.5. (Section 4.8)
2.1.1 Samples are collected using a personal sampling pump calibrated, with a sampling device attached, to within ±5% at the recommended flow rate.
2.1.2 Samples are collected closed-face using a sampling device consisting of two sulfuric-acid treated 37-mm Gelman type A/E glass fiber filters contained in a three-piece polystyrene cassette. The filters are prepared by soaking each filter with 0.5 mL of 0.26 N sulfuric acid. (0.26N sulfuric acid can be prepared by diluting 1.5 mL of 36 N sulfuric acid to 200 mL with deionized water.) The filters are dried in an oven at 100°C and then assembled into three-piece
2.3.1 Remove the plastic end plugs from the sampling device immediately before sampling.
2.3.2 Attach the sampling device to the sampling pump with flexible tubing and place the device in the employee's breathing zone. Position the sampler so it does not impede work performance or safety.
2.3.3 Do not pass the sampled air through any hose or tubing before it enters the sampling device.
2.3.4 Immediately after sampling, seal the sampling device with plastic end plugs and seal and identify with an OSHA Form 21.
2.3.5 Submit at least one blank with each sample set. Blanks should be handled in the same manner as samples, except no air is drawn through them.
2.3.6 Record sample volumes (in liters of air) for each sample. Also list any compounds considered potential interferences that could be present in the sampling area.
2.3.7 If any bulk samples are submitted for analysis, ship them in separate containers from the air samples.
2.4 Sampler capacity
Collection efficiency studies were conducted by drawing humid air through a sampling device that was attached to a glass U-tube immersed in an oil bath heated to 40°C. Milligram amounts of mXDA and pXDA were added to the U-tube. The inlet of the U-tube was attached to a humid air generator so air at approximately 80% relative humidity could be drawn through it. Tests were done by drawing air for 15 minutes at 1.0 L/min and also for 200 minutes at 1.0 L/min. After sampling, the filters were analyzed. None of the amines were found on any of the back filters for any of the tests. There was an average of 7.4 µg of mXDA and 5.6 µg of pXDA found on the front filters for the 15-L samples, and 37.9 µg of mXDA and 26.1 µg of pXDA for the 200-L samples.
2.5 Extraction efficiency
2.5.1 The average extraction efficiency over the range of 0.5 to 2 times the target concentration is 98.8% and 98.6% for mXDA and pXDA respectively. (Section 4.9.1)
2.5.2 The extraction efficiency at 0.05, 0.1, and 0.2 times the target concentration was found to be 96.6%, 98.2%, and 96.7% respectively for mXDA and 97.6%, 98.6%, and 97.0% respectively for pXDA. (Section 4.9.1)
2.5.3 Extracted samples remain stable for at least 24 h. (Section 4.9.2)
2.6 Recommended air volume and sampling rate
2.6.1 For short-term and ceiling samples, sample 15 L of air at 1 L/min (15-min samples). 2.6.2 For long-term samples, sample 100 L of air at 1 L/min.
2.7 Interferences (sampling)
2.7.1 It is not known if any compounds will severely interfere with the collection of the analytes on sulfuric acid treated filters.
2.7.2 Suspected interferences should be reported to the laboratory with submitted samples.
2.8 Safety precautions (sampling)
2.8.1 Attach the sampling equipment to the employee so that it will not interfere with work performance or safety.
2.8.2 Follow all safety procedures that apply to the work area being sampled.
3.1.1 An HPLC system equipped with an ultraviolet detector. A Hewlett-Packard 1050 Series HPLC consisting of a pumping system, programmable variable wavelength detector and an autosampler was used in this evaluation.
3.1.2 An HPLC column capable of separating the analyte of interest from any interferences. A 15-cm × 4.6-mm i.d. Supelcosil LC-ABZ column (Supelco, Inc., Bellefonte, PA, Catalog no. 5-9140) was used in this evaluation. It is critical that if this particular column will not be used for more than 6 h, it should be rinsed with water to remove any buffer salts and ultimately flushed with acetonitrile.
3.1.3 An electronic integrator or some other suitable means of measuring peak heights or areas. A Waters 860 Networking Computer System was used in this evaluation.
3.1.4 Glass vials with Teflon®-lined caps capable of holding 4 mL.
3.1.5 A dispenser capable of delivering 2.0 mL of extraction solvent to prepare standards and samples. If a dispenser is not available, a 2.0-mL volumetric pipet may be used.
3.1.6 A test tube rocker to gently mix the samples during the extraction step. A Vari-Mix mixer (Thermolyne, Dubuque, IA) was used in this evaluation.
3.1.7 A laboratory centrifuge.
3.2.1 m-Xylylenediamine (mXDA) and p-xylylenediamine (pXDA), reagent grade. Aldrich Chemical (Milwaukee, WI) Lot KY00202DP mXDA and Lot PF10421AF pXDA were used in this evaluation. Both of these compounds are corrosive and must be stored under a blanket of nitrogen.
3.2.2 Acetonitrile, methanol, and water, HPLC grade. The acetonitrile and methanol used in this evaluation were "Optima" brand from Fisher Chemical (Fair Lawn, NJ) and the water was from a Millipore Milli-Q water purification system.
3.2.3 Sodium phosphate, monobasic monohydrate (NaH2PO4·H2O), reagent grade. Fisher Lot 704979 was used in this evaluation.
3.2.4 1-Heptanesulfonic acid, sodium salt, HPLC grade. Aldrich Lot HF06915BF was used in this evaluation.
3.2.5 Phosphoric acid, reagent grade.
3.2.6 Extraction solvent/mobile phase. The extraction solvent is the same as the mobile phase used in the HPLC analysis. It consists of 50 mM of 1-heptanesulfonic acid and 50 mM of NaH2PO4·H2O in 75/25, water/acetonitrile adjusted to pH 3.0 with phosphoric acid. To prepare 1 L of the extraction solvent/mobile phase, dissolve (expedite using sonication) 10.1 g of 1-heptanesulfonic acid, sodium salt and 6.9 g of NaH2PO4·H2O into 750 mL of HPLC grade water and adjust the pH of the solution to 3.0 with phosphoric acid. Add, with thorough mixing, 250 mL of acetonitrile to the pH-adjusted aqueous solution.
3.3 Standard preparation
3.3.1 Prepare concentrated standards by accurately weighing approximately 20 mg of each amine into a 25-mL volumetric flask. Dissolve the amines with methanol. Dilute to the mark with additional methanol and thoroughly mix the solution. Stock standards are stable for at least 6 months when stored in brown bottles.
3.3.2 Prepare analytical standards by injecting microliter amounts of stock standards into 4-mL vials containing 2.0 mL of extraction solvent delivered from the same dispenser or pipet used to extract samples.
3.3.3 Bracket sample concentrations with analytical standard concentrations. If samples fall outside of the concentration range of prepared standards, prepare and analyze additional standards at the appropriate concentrations to ascertain the linearity of response.
3.4 Sample preparation
3.4.1 Transfer front and back filters to individual 4-mL vials.
3.4.2 Add 2.0 mL of extraction solvent to each vial using the same dispenser or pipet as used for preparation of standards.
3.4.3 Cap the vials and gently rock them for 15 min.
3.4.4 Centrifuge the sample vials for 10 min at 2000 rpm. Analyze the samples by making direct injections of the centrifuged extracts.
3.5.1 HPLC conditions
Figure 3.5.1. Chromatogram at the target concentrations.
Key: (1) pXDA, (2) mXDA.
3.5.2 Peak heights or areas are measured by an integrator or other suitable means.
3.5.3 An external standard (ESTD) calibration method is used. Calibration curves are prepared by plotting micrograms of analyte per sample versus peak heights or area counts of the standards. Sample concentrations must be bracketed by standards.
Figure 18.104.22.168. Calibration curve from the data in Table 4.5.1.
The equation of the line is Y=36419X.
Figure 22.214.171.124 Calibration curve from the data in Table 4.5.2.
The equation of the line is Y=40879X.
3.6 Interferences (analytical)
3.6.1 Any compound that produces a response on a UV detector at 208 nm and has the same general retention time of any of the analytes of interest is a potential interference. Possible interferences should be reported to the laboratory with submitted samples by the industrial hygienist. These interferences should be considered before samples are extracted.
3.6.2 HPLC parameters may be changed to possibly circumvent interferences.
3.6.3 When necessary, the identity or purity of an analyte peak may be confirmed with additional analytical data, such as wavelength ratioing. As an aid in choosing appropriate wavelengths to ratio, the UV spectra for both analytes is given in Section 4.10.
The analyte concentration for samples is obtained from the appropriate calibration curve in terms of micrograms of analyte per sample. The back filter of each sampler is analyzed primarily to determine if there was any breakthrough from the front filter during sampling. If a significant amount of analyte is found on the back filter (e.g., greater than 25% of the amount found on the front filter), this fact should be reported with sample results. If any analyte is found on the back filter, it is added to the amount found on the front filter. 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 formula.
mg/m³ = (µg of analyte per sample)/[(L of air sampled)(extraction efficiency)]
3.8 Safety precautions (analytical)
3.8.1 Adhere to the rules set down in your Chemical Hygiene Plan.
3.8.2 Avoid skin contact and inhalation of all chemicals.
3.8.3 Wear safety glasses and a lab coat at all times while in the lab area.
Detection limits (DL), in general, are defined as the amount (or concentration) of analyte that gives a response (YDL) that is significantly different (three standard deviations (SDBR)) from the background response (YBR).
YDL - YBR = 3(SDBR)
The direct measurment of YBR and SDBR in chromatographic methods is typically inconvenient and difficult because YBR is usually extremely low. Estimates of these parameters can be made with data obtained from the analysis of a series of analytical standards or samples whose responses are in the vicinity of the background response. The regression curve obtained for a plot of instrument response versus concentration of analyte will usually be linear. Assuming SDBR and the precision of data about the curve are similar, the standard error of estimate (SEE) for the regression curve can be substituted for SDBR in the above equation. The following calculations derive a formula for DL:
At point YDL on the regression curve
YDL = A(DL) + YBR A = analytical sensitivity (slope)
4.2 Detection limit of the analytical procedure (DLAP)
The DLAP is measured as the mass of analyte introduced into the chromatographic column. Ten analytical standards were prepared in equal descending increments with the highest standard containing 14.16 and 14.31 ng/mL of mXDA and pXDA respectively. These concentrations produce peaks approximately 10 times the baseline noise of a reagent blank. These standards, plus a solvent blank, were analyzed and the data obtained were used to determine the required parameters (A and SEE) for the calculation of the DLAPs. Values of 5.78 and 6.84 for A and 47.0 and 69.9 for SEE were obtained for mXDA and pXDA respectively. DLAPs were calculated to be 24.4 and 30.7 pg for mXDA and pXDA respectively.
5.2. ibid. Method 65: Benzidine, 3,3'-Dichlorobenzidine, 2,4- and 2,6-Toluenediamine.
5.3. ibid. Method 71: o-Dianisidine, 4,4'-Methylenebis(o-chloroaniline), o-Tolidine.
5.4. ibid. Method 73: o-, m-, and p-Toluidine.
5.5. ibid. Method 78: Diphenylamine, N-Isopropylaniline.
5.6. ibid., Vol. 4, Method No. 87; m-, o-, and p-Phenylenediamine.
5.7. ibid. Method No. 93; 4-Aminobiphenyl, 1-Naphthylamine and 2-Naphthylamine.
5.8. "American Conference of Governmental Industrial Hygienists: Documentation of the Threshold Limit Values"; 5th ed., p. 638, Cincinnati, OH (1986).
5.9. Material Safety Data Sheet: m-xylylenediamine, Aldrich Chemical Co., Milwaukee, WI, June 1989.
5.10. Material Safety Data Sheet: p-xylylenediamine, Aldrich Chemical Co., Milwaukee, WI, November 1990.
5.11. Lewis, R.J., Sr., Ed. "Sax's Dangerous Properties of Industrial Materials", 8th ed., vol 3; Van Nostrand Reinhold Co.: New York, NY, 1992.
5.12 Bell, A.; Smith, J.G.; Kibler, C.J. J. Polym. Sci. A1, 19 (1965) in "Polyamide Fibers" in Encyclopedia of Chemical Technology 3rd ed., Vol. 18, p. 400, by J. H. Saunders, Monsanto Company.