Document bOxy41eYyxbDj8J92qo3GVeYk

Page Two October 8, 1974 Although the specific details of the analytical methods have not been identified our current best judgment is that the personal monitoring procedure will be a charcoal tube sample collection and a gas chromatographic analysis similar to the enclosed NIOSH #178. Personal monitoring will be required for those employees working in areas where VCM can exceed the "Action Level" (0.5 ppm averaged over an 8 hour day). Personal monitoring must be repeated monthly for employees exposed in excess of the "Permissible Limit" (1.0 ppm for 8 hours or 5.0 ppm for 15 minutes). Continuous monitoring is required in areas where VCM levels may exceed the allowable concentration for "the devices in use". Our current inquiry to OSHA has included a request for clarification of this statement. LBC/ch Distribution *A. W. Clements *C. B. CooperCOPY FOR A. M. Fairlie *R. J. Fawcett *C. R. Flynn E. W. Harrington *M. N. Johnson *E, B. Katzenmeyer, Jr. F. E. Krause R. M. Kreager *P. H. Lawrence R. W. MacCuspie J. F. Malone J. L. Nelson H. R. Rex *R. N, Rylands *G. D. Schaaf E. G. Schwaegerle R. D. Scott *R. W. Strassburg R. L. Toole A. Vittone *P. J. Weaver *A. R. Webber W. J. Wilcox *C. L. Woods *B. M. G. Zwicker R. J. Coffey W. M. Smith *P. M. Zakriski A. L. Schultz C. H. Lufter *J. A, Klupar LBC/File ^Enclosures: (1) Index to NIOSH Manual (2) NIOSH Procedure #127 (3) NIOSH Procedure #178 L. B. Crider NGC 03424 NIGSH MANUAL OF ANALYTICAL METHODS Physical and Chemical Analysis Branch Division of Laboratories and Criteria Development 1014 Broadway, Cincinnati, Ohio 45202 U.S. DEPARTMENT OP HEALTH. EDUCATION, AND WELFARE Public Health Service Center for Disease Control National Institute for Occupational Safety and Health 1974 NGC 03425 TABLE OE CONTENTS P & C:AM No. 101 102 103 105 (06 107 108 109 1 10 112 114 1 16 117 118 121 123 125 126 127 1 39 140 141 142 146 151 152 153 1 55 158 159 160 163 165 Paces 16 1-9 1-5 1-5 1 -7 1-6 1-12 1-7 1-6 1-5 1-5 1-6 1-6 1-6 1-6 1-8 1-9 1-13 Ml 1-8 1-7 . 1-8 1-7 1-7 1-5 1-5 1-6 15 1-9 1-5 1-10 1-7 1-7 Tide Lead in Blood and Urine Lead in Blood and Urine Mercury in Urine Mercury in Blood Colorimetric Method for Free Silica Antimony in Urine Nitrogen Dioxide in Air Free Silica (Quartz, Cristobalite, Tridyrnite) in Atmospheric Dust Quartz in Coal Dust by Infrared Spectroscopy Carbon Monoxide in Air Fluoride in Urine Cyanide in Air Fluoride and Hydrogen Fluoride in Air Acrolein in Air Beryllium in Air Beryllium in Air Formaldehyde in Air Hydrogen Sulfide in Air Organic Solvents in Air Arsenic in Urine and Air Arsenic in Urine and Air 2,4-Toluenediisocyarate (TDI) in Air p.p-Dipbenylmethanediisocyanale (MDI) in Air Sulfur Dioxide in Air Cadmium in Air Total Particulate Chromium in Air Ozone in Air Lead in Air Parathion in Air Oil Mist in Air Sulfur Dioxide in Air Sulfur Dioxide in Air Mercury in Urine v NGC 03426 TABLE OF CONTENTS (Continued) P & CAM No. Pages Title 167 1-8 Mercury in Blood 168 1-11 Aromatic Amines in Air 169 1-6 Chromic Acid Mist in Air 173 1-8 General Procedure for Metals 175 1-15 Mercury in Air Appendix A Description, Installation, and Operation of Two Stage Thermal Desorption Unit for the Mercury Determination vi iVGC 03427 INDEX OF METHODS ARRANGED ACCORDING TO ANALYTE Analyte Acrolein Antimony Aromatic Amines Matrix Air Urine Air Arsenic Arsenic Beryllium Beryllium Cadmium Carbon Monoxide Chromic Acid Mist Chromium (Particulate) Cyanide Air, Urine Air, Urine Air, Settled Dust Ore, Swipe Samples Air, Settled Dust Ore, Swipe Samples Air Air Air Air Air Diphcnylmethanediiso cyanalc Fluoride Air Urine Fluorides and Hydrogen Fluoride Formaldehyde Air Air Procedure Sampling Analysis Impingcr Silica gel Adsorption Membrane Filter Membrane Filler Membrane Filter Colorimetric Colorimetric GC AA Colorimetric AA P & CA M_F 1 I8 107 168 139 140 121 Membrane Filter Emission Spectroscopy 1 23 Membrane Filter Grab-bag Membrane Filter Membrane Filter Impingcr Impinger AA IR Colorimetric AA Ion-Specific Electrode Colorimetric Impingcr Impinger Ion-Specific Electrode Ion-Specific Electrode Colo rimetric 151 1 12 169 152 116 142 I 14 117 1 25 Vll NGC 03428 Analyte Hydrogen SulHcle Lead Lead Lead Mercury (Partic ulate. Metallic, Organic Vapor) Mercury Mercury Mercury Mercury Metals (General Procedure) Nitrogen Dioxide Oil Mist Organic Solvents Ozone Parathion Quartz Silica (Quart/ ) Silica (Quart/., Cristobalitc, Tridymite) Sulfur Dioxide Sulfur Dioxide Matrix Procedure Sampling Analysis Air Impinger Colorimetric Air Membrane Filter AA Blood, Urine Blood, Urine Air Blood Blood Vacutainers Vacutainers Three Section Solid Phase Sampler Vacutainers Vacutainers AA Colorimetric Flameless A A Flameless AA Flameless AA Urine Urine Industrial Hygiene Samples Air Membrane Filter Impinger Flameless A A Flameless AA AA Colorimetric P & CAM N 126 155 101 102 175 105 167 103 165 173 108 Air Air Air Air Coal Dust Air, Dust Biological Tissue Air Membrane Filter Charcoal Adsorption Impinger Impinger Membrane Filter Membrane Filter Membrane Filler Fluorescence GC Colorimetric GC Infrared Colorimetric X-Kay Diffraction 159 127 153 158 110 106 109 Air Impinger Titration 146 Air Impinger Colorimetric 160 vi 11 NGC 03429 Analyte Sulfur Dioxide 2,4-Toluenediisocyanate Matrix Air Air Procedure Sampling Analysis Impinger Titration P&_CAM No 163 lmpinger Colorimetric 1A\ IX NGC 03430 ORGANIC EVENTS IN ATR Physical and Chemical Analysis Branch Amity l i ca.l Method Analyte: Organic Solvents (See Table 1) Matrix: Air Procedure: Adsorption on charcoal desorption with carbon disulfide, GC Date Issued: 9/15/72 Date Revised: 7/15/74 Method No: Range: P&CAM 127 For the specific compound, refer to Tables I&II Precision: 10.5% RSD Classification: See Table 1 1. Principle of the Method 1.1 A known volume of air is drawn through a charcoal tube to trap the organic vapors present. 1.2 The charcoal in the tube is transferred to a small, graduated test tube and desorbed with carbon disulfide. 1.3 An aliquot of the desorbed sample is injected into a gas chromato graph . 1.4 The area of the resulting peak is determined and compared with areas obtained from the injection of standards. 2. Range and Sensitivity The lower limit in mg/sample for the specific compound at 16 x 1 attenuation on a gas chromatograph fitted with a 10:1 splitter is shown in Table 1. This value can be lowered by reducing the attenuation or by eliminating the 10:1 splitter. 3. Interferences 3.1 Wien the amount of water in the air is so great that condensation actually occurs in the tuba, organic vapors will not be trapped. Preliminary experiments indicate that high humidity severely decreases the breakthrough volume. 3.2 Wien two or more solvents are known or suspected to be present in the air, such information including their suspected identities, should be transmitted with the sample; since with differences in polarity, one may displace another from the charcoal. 127-1 NGC 03431 3.3 It must be emphasized that any compound which has the same retention time as the specific compound under study at the operating conditions described in this method is an inter ference. Hence, retention time data on a single column, or even on a number of columns, cannot be considered as proof of chemical identity. For this reason it is important that a sample of the bulk solvent(s) be submitted at the same time so that identity(ies) can be established by other means. 3.4 If the possibility of interference exists, separation conditions (column packing, temperatures, etc.) must be changed to circum vent the problem. Precision and Accuracy 4.1 The mean relative standard deviation of the analytical method is 8%. (Ref. 11.4). 4.2 The mean relative standard deviation of the analytical method plus field sampling using an approved personal sampling pump is 10% (Ref. 11.4). Part of the error associated with the method is related to uncertainties in the sample volume collected. If a more powerful vacuum pump with associated gas-volume integrating equipment is used, sampling precision can be improved. 4.3 The accuracy of the overall sampling and analytical method is 10% (HIOSH's unpublished data) v?hen the personal sampling pump is calibrated with a charcoal tube in the line. Advantages and Disadvantages of the Method 5.1 The sampling device is small, portable, and involves no liquids. Interferences are minimal, and most of those which do occur can be eliminated by altering chromatographic conditions. The tubes are analyzed by means of a quick, instrumental method. The method can also be used for the simultaneous analysis of two or more solvents suspected to be present in the same sample by simply changing gas chromatographic conditions from isothermal to a temperatureprogrammed mode of operation. 5.2 One disadvantage of the method is that the amount; of sample which caii be taken is limited by the number of milligrams that the tube will hold before overloading. When the sample value obtained for the backup section of the charcoal trap exceeds 25% of that found on the front section,__Ue possibility of sample loss exists. During sample storage the more volatile compounds will migrate throughout the tube until equilibrium is reached (33% of the sample on the backup section). 127-2 NGC 03432 5.3 Furthermore, the precision of the method is limited by the reproducibility of the pressure drop across the tubes. This drop will affect the flow rale and cause the volume to be imprecise, because the pump is usually calibrated for one tube only. Apparatus 6.1 An approved and calibrated personal-sampling pump for personal samples. For an area sample any vacuum pump whose flow can be determined accurately at 1 liter per minute or less. 6.2 Charcoal tubes: glass tube with both ends flame sealed, 7 cm long with a 6-mm O.D. and a 4-mm I.D., containing 2 sections of 20/40 mesh activated charcoal separated by a 2-mm portion of urethane foam. The activated charcoal is prepared from coconut shells and ia fired at 600C prior to packing. The absorbing section contains 100 mg of charcoal, the backup section 50 mg. A 3-mm portion of urethane foam is placed between the outlet end of the tube and the backup section. A plug of silylated glass wool is palced infront of the absorbing section. The pressure drop across the tube must be le6S than one inch of mercury at a flow rate of 1 ipm. 6.3 Gas chromatograph equipped with a flame ionization detector. 6.4 Column (20 ft x 1/8 in) with 10% FFAP stationary phase on 80/100 mesh, acid-washed DMCS Chromosorb W solid support. Other columns capable of performing the required separations may be used. 6.5 A mechanical or electronic integrator or a recorder and some method for determining peak area. 6.6 Glass stoppered micro tubes. tubes are recommended. The 2.5-mi graduated microcentrifuge 6.7 Hamilton syringes: standards. 10 pi, and convenient sizes for making 6.8 Fipets: 0.5 mi delivery pipets or 1.0 mi type graduated in 0.1 mi increments. 6.9 Volumetric flasks: solutions. 10 mi or convenient sizes for making standard Reagents 7.1 Spectroquality carbon disulfide (Matheson Coleman and Bell) 127-3 NGC 03433 7.2 Sample of the specific compound under study, preferably chromatoquality grade. 7.3 Bureau of Mines Grade A helium. 7.A Prepurified hydrogen. 7.5 Filtered compressed air. Procedure 8.1 Cleaning of Equipment. All glassware, used for the laboratory analysis should be detergent washed and thoroughly rinsed with tap water and distilled wafer. 8.2 Calibration of Personal Pumps. Each personal pump must be calibrated with a representative charcoal tube in the line. This will minimize errors associated with uncertainties in the sample volume collected. 8.3 Collection and Shipping of Samples 8.3.1 Immediately before sampling, the ends of the tube should be broken to provide an opening at least one-half the internal diameter of the tube (2mm). 8.3.2 The smaller section of charcoal is used as a back-up and should be positioned nearest the sampling pump. 8.3.3 The charcoal tube should be vertical during sampling. 8.3.4 Air being sampled should not be passed through any hose or tubing before entering the charcoal tube. 8.3.5 The flow, time, and/or volume roust be measured as accurately as possible. The sample should be taken at a flow rate of 1 1pm or less to attain the total sample volume required. The minimum and maximum sample volumes that should be collected for each solvent are shown in Tabic 1- The minimum volume quoted must be collected if the desired sensitivity is to be achieved. 8.3.6 The temperature and pressure of the atmosphere being sampled should be measured and recorded. 8.3.7 The charcoal tubes should he capped with the supplied plastic caps immediately after sampling. Under no circumstances should rubber caps be used. 127-4 NGC 03434 8.3.8 One tube should be handled in the same manner as the sample tube (break, seal, and transport), except that no air is sampled through this tube. This tube should be labeled as a blank. 8.3.9 Capped tubes should be packed tightly before they are shipped to minimise tube breakage during shipping. 8.3.10 Samples of the suspected solvent(s) should be submitted to the laboratory in containers furnished by NIOSH for such purpose. These liquid bulk samples should not be transported in the same container as the samples or blank tube. If possible, a bulk air sample (at least 502. air drawn through tube) should be shipped for qualitative identification purposes. 8.A Analysis of Samples 8.4.1 Preparation of Samples. In prepration for analysis, each charcoal tube is scored with a file in front of the first section of charcoal and broken open. The glass wool is removed and discarded. The charcoal in the first (larger) section is transferred to a small stoppered test tube. The separating section of foam is removed and discarded; the second section is transferred to another test tube. These two sections are analysed separately. 8.4.2 Desorption of Samples. Prior to analysis, one-half ml of carbon disulfide is pipetted into each test tube. (All work with carbon disulfide should be performed in a hood because of its high toxicity.) Tests indicate that desorption is complete in 30 minutes if the sample is stirred occasionally during this period. The use of graduated glass-stoppered, microeentrifuge tubes is recommended so that one can observe any apparent, change in volume during the desorption process. Carbon disulfide is a very volatile solvent, so volume changes can occur during the desorption process depending on the surrounding temperature. The initial volume occupied by the charcoal plus the 0.5 m2. CS2 should be noted and corres ponding volume adjustments should be made whenever necessary just before GC analysis. 8.4.3 CC Conditions. The typical operating conditions for the gas chromatograph are: 1. 85 cc/min. (70 psig) helium carrier gas flow. 2. 65 cc/min. (24 psig) hydrogen gas flow to detector. 3. 500 cc/min. (50 psig) air flow to detector. 4. 200C injector temperature. 127-5 NGC 03435 5. 200C manifold temperature (detector) 6. Isothermal oven or column temperature - refer to Table 1 for specific compounds. 8.4.4 Injection. The first step in the analysis is the injection of the sample into the gas chromatograph. To eliminate difficulties arising from blowback or distillation within the syringe needle, one should employ the solvent flush injection technique. The 10 pt syringe is first; flushed with solvent several times to wet the barrel and plunger. Three microliters of solvent are drawn into the syringe to increase the accuracy and reproducibility of the injected sample volume. The needle is removed from the solvent, and the plunger is pulled back about 0.2 pi to separate the solvent flush from the sample with a pocket of air to be used as a marker. The needle is then immersed in the sample, and a 5-p2- aliquot is withdrawn, taking into consideration the volume of the needle, since the sample in the needle will be completely injected. After the needle is removed from the sample and prior to injection, the plunger is pulled back a short distance to minimize evap oration of the sample from the tip of the needle. Duplicate injections of each sample and standard should be made. No more than a 3% difference in area is to be expected. 8.4.5 Measurement of area. The area of the sample peak is measured by an electronic integrator or some other suitable form of area measurement, and preliminary results arc read from a standard curve prepared as discussed below. 8.5 Determination of Desorption Efficiency 8.5.1 Importance of determination. The desorption efficiency of a particular compound can vary from one laboratory to another and also from one batch of charcoal to another. Thus, it is necessary to determine at least once the percentage of the specific compound that is removed in the desorption process for a given compound, provided the same batch of charcoal is used. The Physical and Chemical Analysis Branch of NIOSH has found that the desorption efficiencies for the compounds in Table 1 are between 81!? and 100% and vary with each batch of charcoal. 8.5.2 Procedure for determining desorption efficiency. Activated charcoal equivalent to the amount in the first: section of the sampling tube (100 mg) is measured into a 5cm, 4-ron 1.1). glass tube, flame-sea It'd at one end (similar to commercially available, culture tubes) . This charcoal must be from the same batch as that used in obtaining the samples and can be obtained from unused charcoal tubes. The open end is capped 127-6 NGC 03436 vii th Parafilm. A known amount of the. compound is injected directly into the activated charcoal with a mieroliter syringe, and the tube is capped with more Parafilm. The amount injected is usually equivalent to that present in a 10-liter sample at a concentration equal to the federal standard. At least five tubes are prepared in this manner and allowed to stand for at least overnight to assure complete abosrption of the specific compound onto the charcoal. These five tubes are referred to as the samples. A parallel blank tube should be treated in the same manner except that no sample is added to it. The sample and blank tubes are desorbed and analyzed in exactly the same manner as the sampling tube described in Section 8.3. Two or three standards are prepared by injecting the same volume of compound into 0.5 mi of CS2 with the same syringe used in the preparation of the sample. These are analyzed with the samples. The desorption efficiency equals the difference between the average peak area of the samples and the peak area of the blank divided by the average peak area of the standards, or desorption efficiency Area sample - Area blank Area standard Calibration and Standards It is convenient to express concentration of standards in terms of mg/0.5 mi CS2 because samples are desorbed in this amount of CS2 To minimize error due to the volatility of carbon, disulfide, one can inject 20 times the weight into 10 m& of CS7. For example, to prepare a 0.3 mg/ 0.5 m2, standard, one would inject 6.0 mg into exactly 10 m2, of CS9 in a glass-stoppered flask. The density of the specific compound is used to convert 6.0 mg into microliters for easy measurement with a mieroliter syringe. A series of standards, varying in concentration over the range of interest, is prepared and analyzed under the same GC conditions and during the same time period as the unknown samples. Curves are estab lished by plotting concent ration in mg/0.5mi versus peak area. NOTE: Since no internal standard is used in the method, standard solution must be analyzed at the same time Lhnt the sample analysis is dene. This will minimize the effect of known day-to-day variations and variations during the same day of the FID response. 127-7 NGC 03^37 10. Calculations 10.1 The weight, in mg, corresponding to each peak area is read from the standard curve for the particular compound. No volume corrections are needed, because the standard curve Is based on mg/0.5 rat CS2 end the volume of sample injected is identical to the volume of the standards injected. 10.2 Corrections for the blank must be made for each sample. Correct mg mgs - mgb where: mgs = mg found in front section of sample tube ~ mS found in front section of blank tube A similar procedure is followed for the backup sections. 10.3 The corrected amounts present in the front and backup sections of the same sample tube are added to determine the total measured amount in the sample. 10.4 This total weight is divided by the determined desorption efficiency to obtain the total mg per sample. 10.5 The volume of air sampled is converted to standard conditions of of 25C and 760 mm Hg. P vs " v x 760 298 T+273 where: V = volume of air in liters at 25C and 760 mm Hg s V = volume of air in liters as measured P - Barometric pressure in run Hg T = Temperature of air in degree centigrade 10.6 The concentration of the organic solvent in the air sampled can be expressed in mg per m^, which is numerically equal to yg per liter of air , mg/m-> pg/fi. total mg (Section 10.A) x 1000 (pg/ing) --------------------------------------------------------------------------- Vs 10.7 Another method of expressing concentration is ppm, defined asuiof compounds per liter of air where: ppm " pfi. of compound/V6 of compound ppm - *--------------------------- Vs 24.45 x------------ MW 24.45 = molar volume at 25C and 760 turn Hg MVf = molecular weight of the compound (Table 1) 127-8 NC.C 03438 11. References 11.1 White, L.D., T).G. Taylor, P.A. Mauer, and R.E. Kupel, "A Convenient Optimized Method for the Analysis of Selected Solveni Vapors in the Industrial Atmosphere," Anicr. Ind. Hijcj. Assoc. J.r 31:225 (1970). 11.2 Young, D.M. and A.D. Crowell, Physical Adsorption of Gases, Butterworths, London, 1962, pp. 137-146. 11.3 Federal Register, 37 (#202), 22139-22142 (October 18, 1972). 11.4 NIOSH Contract HSM-99-72-98, Scott Research Laboratories, Inc., "Collaborative Testing of Activated Charcoal Sampling Tubes for Seven Organic Solvents," pp. 4-22, 4-27 (1973). 127-9 NGC 03439 TABLE I PARAMETERS ASSOCIATED WITH P&CAB ANALYTICAL METHOD NO. 127 Organic Solvent Acetone Benzene Carbon tetrachloride Chloroform Dichloromethane p-Dioxane Ethylene dichloride Methyl ethyl ketone Styrene Tetrachloroethylene 1,1,2-trichloroethane 1,1,1-trichloroethane (Methyl Chloroform) Trichloroethylene Toluene Xylene Method Detection limit Classification (mg/sample) Sample Volume () Minimum^ Maximum^ GC Column Temperature(C) D _ 0.5 A 0.01 0.5 A 0.20 10 A 0.10 0.5 D 0.05 0.5 A 0.05 1 D 0.05 1 B 0.01 0.5 n 0.10 1.5 B 0.06 1 B 0.05 10 B 0.05 0.5 A 0.05 1 B 0,01 0.5 A 0.02 0.5 __________________________l 7.7 55 60 13 3.8 18 12 13 34 25 97 13 17 22 31 60 90 60 80 85 100 90 80 150 130 150 150 90 120 100 Molecular Weight 58.1 78.1 154.0 119 84.9 88.1 99.0 72.1 104 166 133 133 131 92.1 106 (a) Minimum volume, in liters, required to measure 0.1 times the OSHA standard (b) These are breakthrough volumes calculated with data derived from a potential plot (reference 11.2) for activated coconut charcoal. Concentrations of vapor in air at 5 times the OSHA standard (reference 11.3) or 300 ppm, whichever is lower, 25C, and 760 torr were assumed. These values will be as much as 50% lower for atmospheres of high humidity. The effects of multiple contaminants have not been investigated, but it is suspected that less volatile compounds may displace more volatile compounds (See 3.1 and 3.2) NGC 03440 TABLE II CHEMICALS WHICH HAVE GREATER THAN 80/S DESORPTION EFFICIENCY BUT HAVE NOT BEEN THOROUGHLY TESTED EY NIOS11 Class E (Proposed) Acrylonitrile Allyl glycidyl ether n-Amyl acetate 2-Butoxyethanol n-Butyl acetate n-Butyl alcohol n-Butylglycidyl ether Chlorobenzene Cyclohexane Cyclohexanone o-Dichlorobenzene p-Dichlorobenzene Diethyl ether N,N-Dimethyl aniline Epichlorohydrin 2-Ethoxylethyl acetate Ethyl acetate Ethylbenzene Ethyl butyl ketone Fufural Heptane Hexane Isoamyl acetate Tsobutyl acetate Isobutyl alcohol Isoctane Isophorone Isopropyl acetate Isopropyl glycidyl ether 2,6-I.utidine Methyl acetate Methyl acrylate Methyl n-butyl ketone Methyl ethyl ketone Methyl isobutyl ketone Methyl methacrylate a-Methyl styrene p-Methyl styrene n-Octane 3-0ctanone Pentane 2-Pentanone a-pinene n-Propyl acetate 1,1,2,2-Tetrachloroethane Tetrahydrofuran Trichlorotriflnoroethane (Preen 113) Recommended Sample Size = 10fc 127-11 NGC 03441 \* VINYL CHLORIDi: IN AIR Physical and Chemical Analysis Branch Analytical Method , Analyte: Matrix: Vinyl Chloride (Chloroetheue, Chloroethylone) Air Method No,: Range: P&CAM //178 0.2-1500 ng per injection Procedure: Adsorption on charcoal, desorption with carbon disulfide, GC Date Issued: 9/3/74 Precision: Unknown Dcite Revised: Classification: D (Operational) 1. Principle of the Method 1.1 A lcnown volume of air is drawn through a charcoal tube to trap the vinyl chloride present. 1.2 The charcoal in the tube is transferred to a small vial containing carbon disulfide where the vinyl chloride is desorbed. 1.3 An aliquot of the desorbed sample is injected into a gas chroma tograph. 1.4 The area of the resulting peak is determined and compared with areas obtained from the injection of standards. 2. Range and Sensitivity 2.1 The minimum detectable amount of vinyl chloride was found to be 0.2 nanograms per injection at a 1 x 1 attenuation on a gas chromatograph. 2.2 At the recommended sampling flow rate of 50 ral/min, the total volume to be sampled should not exceed 5.0 liters. This value is the volume which the front section of the charcoal Lube.will hold at 200 ppm before a significant amount of vinyl chloride is found on the backup section. (The charcoal, tube consists of two sections of activated charcoal separated- by a section of urcthan foam. [See Section 6.2.]) If a particular atmosphere 178-1 NGC 03442 I j: ie suspected of containing a high concentration of contaminants ond/or a high humidity is suspected, the sampling volume should be reduced by 50X. 3. -Interferences 3.1 When the amount of water in the air is so great that, condensation actually occurs in the tube, organic vapors will not be trapped. Preliminary experiments indicate that high humidity severely decreases the capacity of the charcoal for organic vapors. 3.2 When two or more substances are known or suspected to be present in the air, such information,, including their suspected identities, should be transmitted with the sample since these compounds may interfere with the analysis for vinyl chloride. 3.3 It must be emphasized that any compound which has the same retention time as vinyl chloride at the operation conditions described in this method is an interference. Hence, retention time data on a single column, or even on a number of columns, cannot be considered as proof of chemical identity. For this reason it is important that a sample of: the bulk material be submitted at the same time so that identity(ies) can be established by other means. 3.4 If the possibility of interference exists, separation conditions (column packing, temperature, etc.) must be changed to circumvent the problem. 4. Precision and Accuracy The precision and accuracy of the total sampling and analytical method have not been determined. 5. Advantages and Disadvantages of the Method 5.1 The sampling device is small, portable, and involves no liquids. Interferences are minimal, and most of those which do occur can be eliminated by altering chromatographic conditions. The tubes are analyzed by means of a quick, instrumental method. The method can also be used for the simultaneous -analysis of tvo or s-.ore components suspected to be present in the same cample by simply changing gas chromatographic conditions from isothermal to a temperature-programmed mode of operation. 178-2 JNGC 03443 5.2 One disadvantage of the method is that the. amount of sample which can be taken is limited by the number of milligrams that the tube will hold before overloading. Wien the sample value obtained for the backup section of the charcoal trap exceeds 20% of that found on the front section, the possibility of sample loss exists. During sample storage, volatile compounds such as vinyl chloride Will migrate throughout the tube until equilibrium is reached. At this time ~33% of this compound will be found in the backup section. This may lead to some confusion as to whether breakthrough has occurred. This migration effect can be considerably decreased by shipping and storing the tubes at -20. 5.3 The precision of the overall method is limited by the reproduci bility of the pressure drop across the tubes. This drop will affect the flow rate and cause the volume to be imprecise, because the pump is usually calibrated for one tube only. 6. Apparatus 6.1 An approved, and calibrated personal sampling pump for personal and area samples whose flow can be determined accurately at 50 milliliters per minute. 6.2 Charcoal tubes: glass tube with both ends flame sealed, 7 cm long with a 6-mm O.D. and a 4-ram I.D., containing 2 sections of 20/40 mesh activated charcoal separated by a 2-ma portion of urethan foam. The activated charcoal is prepared from coconut shells and is fired at 600C prior to packing to remove material possibly absorbed on charcoal. The primary absorbing section contains 100 mg of charcoal, the backup section 50 mg. A 3-mra portion of urethan foam is placed between the outlet end of the tube and the backup section. A plug of silylated glass wool is placed in front of: the absorbing section. The pressure drop across the tube must, be less than one inch of mercury at a flow rate of 1 /min. 6.3 Gas chromatograph equipped with a flame ionization detector. 6.4 Column (20 ft x 1/8 in) with 10% SE-30 stationary phase on 80/100 mesh, Chrcm.osorb U, acid v;ashed, si.lani.zed with dimelhyldichlorosilane solid support. Other columns capable of performing the required separations may be used. 6.5 A mechanical or electronic integrator or a recorder and some method for determining peak area. 6.6 Two-ml vials which can bo sealed with caps containing teflon- lined silicone rubber septa. 6.7 Microlitcr syringes: standards. 10 yt and convenient sizes for making 178-3 NGC 03444 6,8 Gas-Light syringes: 1 mi, with opcn/close valve. 6.9 PipctsJ 0.5-ini delivery pipets or 1.0-mi type graduated in 0.1-mi increments. 6.10 Volumetric flasks: 10-mi or convenient sizes for making standard solutions. It is preferable to have plastic stoppers for the volumetric flasks. Reagents 7.1 Spectroquality carbon disulfide. 7.2 Vinyl chloride, lecture bottle, 99.9% minimum purity. 7.3 Toluene, chromatographic quality. 7.4 Bureau of Mines Grade A helium. 7.5 Prepurified hydrogen. 7.6 Filtered compressed air. Procedure 8.1 Cleaning of Equipment. All glassware used for the laboratory analysis should be detergent washed and thoroughly rinsed with distilled water. 8.2 Calibration of Personal Pumps. Each personal pump must be calibrated with a representative charcoal tube in the line. This will minimize errors associated with uncertainties in the sample volume collected. 8.3 Collection and Shipping of Samples 8.3.1 Immediately before sampling, the ends of the tube are broken to provide an opening at least one-half the . internal diameter of the tube (2 mm). G.3.2 The smaller section of charcoal is used as a backup and is positioned nearest the sampling pump. 8.3.3 The charcoal tube is placed in a vertical position during sampling, ope.n end pointing upward, to prevent "channelling of the charcoal. 8.3.4 Air being sampled is not to be passed through any hose or tubing before entering the charcoal tube. 178-4 jSGC 03445 j i' il 8.3.5 Bulk air samples are taken along with personal camples, i.c*. sample 10-20 liters of the air in the environment using a separate charcoal tube. 8.3.6 The flow, time, and/or volume must be measured as accurately as possible. The sample is taken at a flow rate of 50 ral/min. The maximum-volume to be sampled should not exceed 5.0 liters (See Section 2.2). 8.3.7 The temperature and pressure of the atmosphere being sampled is measured and recorded. 8.3.8 The charcoal tubes are capped with the supplied plastic caps immediately after sampling. Under no circumstances are rubber caps to be used. 8.3.9 One tube is handled in the same manner as the sample tube (break, seal, and transport), except that no air is sampled through this tube. This tube is labeled as a blank. 83.10 Capped tubes are packed tightly before they arc shipped to minimize tube breakage during transport to the laboratory. If the samples will spend a day or more in transit, cooling (e.g., with dry icc.) is necessary to minimize migration of vinyl chloride to the backup section. 8.3.11 Samples received at the laboratory are logged in and immediately stored in a freezer (--20C) until time for analysis. Samples may be stored in this maimer for long periods of Lime with no appreciable loss of vinyl chloride (2 months). It should be pointed out that during long periods of storage (more than 2 weeks), the ' vinyl chloride will equilibrate between the two sections of charcoal, i.e., will migrate to the backup section. This does not constitute breakthrough. 8,4 Analysis of Samples 8.4.1 Preparation and Desorption of Samples. In preparation for analysis, each charcoal tube is scored with a file in front of the first section of charcoal and broken open. Tim glass wool is removed and discarded. The charcoal in the first (larger) section is transferred to a small vial containing 1 ml of carbon disulfide. (Note the addition of the CS2 is important.) The vial :Ls topped vilh a 178-5 NGC 03446 septum cap (See Section 6.6). The separating section of foam is removed and discarded; the second section is transferred to another small vial containing 1 ml of CS2. These two sections are analyzed separately. Tests indicate that desorption is comp]etc in 30 minutes if the sample is stirred occasionally during this period. In any case samples should be analyzed within 60 minutes after addition of CS2. 8.4.2 GC Conditions. The typical operating conditions for the gas chromatograph are: 1* 40 cc/min. (80 psig) helium carrier gas flow 2. 65 cc/uin. (20 psig) hydrogen gas flow to detector 3. 500 cc/min. (50 psig) air flow to detector 4. 230C injector temperature 5. 230C manifold temperature (detector) 6. 60C isothermal column temperature (oven). 8.4.3 Injection. The first step in the analysis is the injection of the sample into the gas chromatograph. To eliminate difficulties arising from blowback or distillation within the syringe needle, one should employ the solvent flush injection technique. The 10 pfi. syringe is first flushed with solvent several times to wet the barrel and plunger. Two microliters of solvent are drawn into the syringe to increase, the accuracy and reproducibility of the injected sample volume. The needle is removed from the solvent and the plunger ispulled back about 0.4 \il to separate the solvent flush from the sample with a pocket of air to be used as a marker. The needle is then immersed in the sample, and a 5-paliquot is withdrawn to the 7.4 px mark (2 y solvent 4- 0.4 pE. air + 5 yS, sample = 7.4 p). After the needle is removed from the sample and prior to injection the plunger is pulled back a short distance to minimize evaporation of the sample from the tip of the needle. Duplicate injections of each sample and standard are made. No more than a 27. difference in area is to be expected. 8.4.4 Measurement of area. The area of the sample peak is measured by an electronic integrator or some other suitable form of area measurement, and preliminary results are read from a standard curve prepared as discussed below. 8.5 Determination of Desorption Efficiency 8.5.1 Importance of determination. The desorption efficiency of a particular compound can vary from one laboratory to another and also from one batch of charcoal to another. Thu3, it is necessary to determine at: least once the percentage of vinyl chloride that is removed in the 178-6 ISjGC 03447 desorption process. Desorption efficiency should be determined on the same batch of charcoal tubes used in Rampling. Results indicate that desorption efficiency varies with loading (total vinyl chloride on the tube) particularly at lower values, i.e., 2.5 pg. 8.5.2' Procedure for determining desorption efficiency. Charcoal tubes from the same batch as that used in obtaining samples arc used in this determination. A known volume of vinyl chloride gas is injected into a bag containing a known volume of air. The bag is made of Tedlar (or a material vhich will retain the vinyl chloride and not absorb it) and should have a gas sampling valve and a septum injection port. The concentration of the bag may be calculated at room temperature and presstire. A known volume is then sampled through a charcoal tube with a calibrated sampling pump. At least five tubes are prepared in this manner. These tubes are desorbed and analyzed in the same manner as the samples (See Section 8.4). Samples taken with a gas tight syringe from the bag are also injected into the GC. The concentration in the bag is compared to the concentration obtained from the tubes. The desorption efficiency equals the difference between the average weight of the samples and the weight of the blank divided by the average weight of the vinyl chloride standard gas mixture in the bag or Desorption efficiency " Weight on sample. - Weight on blank Weight in standard gas mixture Calibration and Standards CAUTION: Laboratory Operations Involving Carcinogens Vinyl chloride has been identified as a human carcinogen and appropriate precautions must be taken in handling this gas. Specifically, the Occupational Safety and Health Administration has promulgated regulations for the use and handling of: vinyl chloride. The regulations currently serve as an emergency standard and may be found in 29 C)?l\ 1910.93q (faction 1910.93q in Title 29 of the Code of Federal Regulations available, in the Federal Regis-Ler, Volo 39, Ho. 125, Thursday, June 27, 1974.) Note that the above, is an emergency standard (temporary) and will be replaced by a permanent standard in October of 1974. A Berios of standards, varying in concentration over the range of interesL, are prepared and analyzed under the same GC conditions and during the. sane time period as the unknown samples. Curves are established by plotting concentration in pg/1.0 mi versus peak area. There are two methods of preparing standards and as long as highly purified vinyl chloride is used, both are comparable. 178-7 . NGC0344H XTC