Document NGRBZ2Qa4LVnmzD4R5DQLK4yb

Colgate-Palmolive Company Research and Development Department Piscataway, New Jersey "* ,' ' August 15, 1973 Q Research Report 2675 (Analytical Method) - DETERMINATION OP CHRYSOTILE ASBESTOS IN TALC BY X-RAY DIFFRACTION Author: Pasquale Brscese Analytical Section PC U7 RPA 62130 Referenced Lab Notebook: 5075 Previous Research Report: None f PLAINTIFFS EXHIBIT WCD-148 QE-CPC00005063 iii J ABSTRACT An x-ray diffraction technique for the determination of chrysotile asbestos in talc is described. Quantitative analysis is made by measuring the area under a selected diffraction peak using the step-scan procedure. The (002) chrysotile peak d = 7.3 A is ideal for this measurement; however, the talc (N.C. Regal Talc used in this study) contains Kaolinite (001~) line d = 7*18 A ,ps a contaminant which interferes with this chrysotile line. Therefore, the {OOU) line, d = 2.6k A , of chrysotile was used. To compensate for its weaker intensity, a longer exposure for each step was used. This was statistically calculated9 to be 80 seconds. The method is estimated to have a lower limit of detection of 0.2$ chrysotile in talc. QE-CPC00005064 iv TABLE OF CONTENTS -- ------ " ABSTRACT...... ............... ....................... iil LIST OF ILLUSTRATIONS...... ........... . v . LIST OF TABLES..................................... v DIGEST OF REPORT............ 1 EXPERIMENTAL DETAILS....... 2 1. Instrumental Conditions..... ........... 2 2. Estimation of Expected Intensities..... . 2 3 Procedure............. ... ... ............. h h . Calibration Curve........ 1* 5. Analytical Error Dueto Counting Statistics 5 6. Variation of Standard Deviation with Counting Time............ 7 7. Lover Limit of Detection ( L . L . D . . 9 RESULTS.............. 10 1. Reproducibility and Precision of the Instrument.... ....................... 2 Recovery Study,.................... 10 .10 DISCUSSION.............. 11 CONCLUSION iND RECOMMENDATIONS......... 12 INDEX TERMS.......................................... 13 REFERENCES......................... lU C c QE-CPC00005065 V* LIST OF ILLUSTRATIONS Figure 1 Working Curve: Intensity Net Counts in O.Up Angle vs. Concentration, Weight % Chrysotile Figure 2 Variation of Standard Deviation With Counting Time LIST OF TABLES Table 1 Standard Components*' Weights in Grams Table 2 Results: Intensity-Net Counts in 0.h Angle vs. Concentration Weight % Chrysotile Table 3 Analytical Error Due to Counting Statistics Table h Reproducibility and Precision of the Instrument Table 5 Recovery Study C c r c QE-CPC00005066 DIGEST OF REPORT Introduction The characteristics of x-ray diffraction patterns provide a specific method for the identification of crystalline compounds. This technique can be applied either qualitatively or quantitatively to the examination of solid materials. The allegation that commercial samples of talc contain asbestos minerals contaminants which could be hazardous to health when inhaled led to the development of this method, '' Major interest is focused on chrysotile asbestos, a fibrous variety of serpentine, which shows major diffraction peaks at d = 7.3 A and d - 3-64 A while the amphibole group, another variety of asbestos, shows a maximum at d = 8.1+ A. (l,2) This report presents details for the quantitative analysis hy x-ray diffraction of chrysotile asbestos in talc at the (00^) line corresponding to the major diffraction peak at d = 3 -6k A 0 . r QE-CPC00005067 * EXPERIMENTAL DETAILS 1. ' Instrumental Conditions Apparatus: Philips Electronics Instruments x-ray generator, type No. 12215/0, was used in combination with a high angle vertical goniometer, scintillation counter and step-scanner, GuK^ radiation, Nickel filtered, generated at 35 kv and 18 Ma, Slit system: divergence scatter receiving "*1 D 0.006 inch Io Signals from the detector were fed through a pulse height descriminator and the integrated counts per step printed out on a teletypewriter. The step-scanning arrangement permitted the measurement of small integrated areas of 0.01 per step, A total of kO steps covering an angle of 0.k 2 theta from 2k,20 up to 2k.60 was used for peak area, and an angle of 0.2 2 theta from 23-50 up to 23.70 and 26.15 up to 26.35 was used .or background. J In every sample prior /to counting for quantitative analysis, a qualitative scan is necessary over the angle from 23 up to 27 2 theta to ensure than the area considered for background is free from interferences, , ' /! Counting time per step was 80 seconds and total counting time 80 x ';0 = 3,200 secrhds for peak area and 3,200 seconds for background. (6) y ,. Reagents*: I i North arolina Regal Talc from Charles Mathiew, Inc. Chrysotile Asbestos i,4j_0 obtained from Whittaker, 01a*k and Daniels, Inc. . * Both materials were supplied through the help of the Skin Products Section. / t 2. Estimation of pcpected Intensities Talc, a natural hydrous magnesium silicate with the formula Mg Si^O-^iOH) , crystallographically is monoclinic and triclinic 'in form. Geologically, the mineral occurs in rock masses and co-exists with; a large number of other hydrated magnesium mineral . species-,-- -- - .0 QE-CPC00005068 Chrysotiie, a naturally-fibrous mineral, la a hydrated silicate of magnesium which approximates In composition the formula H^Mg^Si 0 . The structure is nonoclinics four molecules of H.Mg Si?0 inJthe ^ unit cell. Each silicon atom is surrounded by four oxygen atoms arranged at the point of a tetrahedron. Together these groups form chains extending parallel to the vertical axis. The binding forces between these chains are weak, thus accounting for the fibrous Structure. It includes most of the silky amianthus of serpentine rocks and much of what is popularly called asbestos, (k) Qualitative examination by x-ray diffraction of N.C. Regal Talc Shoved mainly talc, with the following minor constituents: chlorite, kaolinite , phlogopite, dolomite and alpha quartz. Ho detectable quantities of asbestiform minerals, either the amphibole or serpentine group were seen, (2) , Of the above constituents, none absorbed Copper radiation strongly in relation to talc, this is known from study of the appropriate chemical elements constituent to each compound. So, absolute counts versus concentration of qhrysotile Bhould give a straight line. The intensity of the (OOU) line of pure chrysotiie d = 3.6k A gave counts/second net by step-scanning. (In terms of counts per second per percent ,his = 5>k0 c /b /%.) Calculation of mass absorption coefficients for Cu K radiation gave 32,07 for tale and 29.88 for {chrysotiie. The following equation gives the c/s/3E expected in a mixture of tale and chrysotiie. z/b /% m - x 2p.88 3.0 ,0 7 _ 5,03 v-nd 5.03 tj.n ' X 100 " 9 ^% Practically no corr ction is needed due to absorption in the mixture of talc and chrysotiie. (3,5) . The value obtained for the mass absorption coefficients are based on the formulas for talc, Mg Si.O n (0H),,, and chrysotiie Mg Si 0 (OH), . (Card Ho. 19-770 fOr talc an* 9 - k U for chrysotiie edited vy the Joint Committee on Powder Diffraction Standards.)* 'i f. Joint Committee on JCPDS Powder Diffraction Standards 'i l601 Park Dane, Swarthmore, Pennsylvania 19081 c c QE-CPC00005069 - k- 3. Procedure No special sample preparation was necessary for the talc. North Carolina Regal talc is already finely-ground to pass a 325 jresh sieve, 1*1+ microns opening, as received. The chrysotile asbestos obtained from Whittaker, Clark & Daniels, Inc., #LlO, was partially ground and needed further grinding to diminish the particle size to an average of 50 microns. This was accomplished by 2 hours grinding in a Waring Blender.* The ground fibers were checked by microscope for size. * The blending assembly can be obtained from Waring Products Service Center, New Hartford, Connecticut 06057> Model No. 5^18. An exactly-known weight of chrysotile was added to the talc. The mixture, tightly closed in a weighing bottle, was placed in another jar and insulated with tape in the jar to avoid breakage. This jar was placed in a mixer/mill* and each sample mixed for 1 hour with the help of two plastic balls. * Spex Model l8lO, Spex Industries, Metuchen, New Jersey. Each sample, after be .;g properly mixed, was loaded in a flat aluminum x-ray sample holder. Care was taken to ensure proper loading of the powderi To minimize orientation effects and to standardize the procedure for each sample, the,following three steps were found necessary: : c 1. Load the sample holder and press the powder with a , spatula. < 2. Remoye the excess with a Gillette razor blade. 3. Make the surface flat and smooth by pressing with a g~ourd glass plate. Finally, place the sample in the x-ray instrument and take counts over the peak and background areas, < C U. iCalibration Curve . ' !- Chrysotile can be detected with a high degree of assurance by a qualitative x-ray scan when present at approximately 51 and higher. Consequently, a calibration curve covering the range from 1 to 5% only was necessary. Samples used for calibration are listed in Table _1,_ ----- ' c C r. | QE-CPC00005070 Table 1 Standard Components'Weights in Grams Talc Chrysotile Total % Chrysotile 2.1+75 2.1+50 2.1+25 2.1+00 2.375 0.025 0.050 0.075 0.100 0.125 2.500 2.500 2.500 2.500 2.500 1.0 2.0 3.0 1+.0 5.0 Results obtained by x-ray analysis are listed in Table 2 and plotted in Figure 1. , Table 2 Results: Intensity Ret Counts in 0.1+ Angle vs. Concentration in Weight % Chrysotile Concentration Weight % Chrysotile Intensity Met Counts 0.1+ Angle 1.0 * 2.0 3.0 i+.O ' 5-0 j 26.1+00 39.100 61.870 86.1+30 102,550 Ret Counts - Total Counts (Peak Area - Background Area) IL Using the method of least squares, the following equation was found for the relationship between intensity and concentration. y = intensity (net counts) x = concentrat ion in vt. % chrysotile v. > ' Equation of the line: y = 3381 + 19-963 x. Analytical Error Due to Counting Statistics (5) A series of measurements for 1, 2, 3, i and 5%' chrysotile in talc 3.ve the following counts. Table 3, columns 2 and 3. ! i 1 'c . c v C o QE-CPC00005071 QE-CPC00005072 -7- The standard deviation () in percent of a measurement involving a given number of counts at peak area Np and a given number of counts at background area Nb is G {%) = 100 Np ~ Nb In Table 3, 2F is shown as counting error and in terms of % chry sotile, columns if and 5- Table 3 * Analytical Error Due to Counting Statistics Concentration Np Counting Error 2 Nb Error 2* % Chrysotile 1% 353,080 326,1+1+0 6.2% 0 .062% 2% 360,7^0 321,61+0 1+.21 0.08k% 3% 386,390 32l+ ,520 2.71 0 .016% h% 1+29,190 31+2,760 2.0% 0.080% 5% 1+33,390 330,81+0 1.7* 0.085# Variation of Standard Deviation With Counting Time (5,6) A series of measurements of a sample containing 1% chrysotile in talc gave a total count 353,000 for the peak area and 326,1+1+0 for the background area, (1+0 steps, 80 seconds per step). . Taking the same number of steps, i.e., 1+0, and different counting time, i.e., 5, 10, 20, 1+0, 60, 80, 100 and 200 seconds per step, the following equations are applicable. ,, Total_Countin_Time x ^^3,080 - Counts for peak area = Np T o t ^ __Cp_|^ oi_ng Time x 326,1+1+0 = Counts for background = Nb,, where: G{%) = 100 3 I l j L Rp - Nb From the data obtained, a curve is constructed in Figure 2 showing the standard deviation as a function of counting time. No great advantage occurs by increasing the counting time above 80 seconds. QE-CPC00005073 uu L QE-CPC00005074 - y- J. Lover Limit of Detection (L.L.D.) (5,6) The lower limit of detection is normally defined as that concen tration which gives a count rate equivalent to a background reading plus twice the standard deviation of the background. This assumption will De correct in 95$ of cases studied (95$ confidence limit). where: Db = 326,UUo net counts of background fNb = 571.35 counts for 1(6) 2^Nb = 111+2.70 counts for 2(6) . Equation of the line y = 3381 + 19,967 x -, let y = 0 x = -0.17$ Let y = 11^3 counts = 2(Pabove background x = -0.11$ L.L.D. = = x at y = 11^3 - x at y = 0 = 0.06$ " As a figure of merit, it is better to multiply the L.L.D, by 3, where 3 is a factor which corrects.for instrumental drift. Therefore, L.L.D. = + 0.18$ chrysotile. C. C C QE-CPC00005075 - io - RESULTS X. Reproducibility and Precision of the Instrument The reproducibility of the x-ray instrument vas checked by daily analyses on a standard for 6 consecutive days. The standard used contained 5$ chrysotile. Table It Reproducibility and Precision of l^fe Instrument - Standard: 5$ Chrysotile in Talc Day Intensity: Net Counts 0.1 -Angle $ Chrysotile 1 102,550 2 102,230 3 103,979 h 100,039 5 97,261 6 101,551 5.13$ 5.12$ 5-21$ 5.01$ 1.87$ 5.08$ Av. = 5*07% SD ~ + 0.12 RSD = 2,3$ 2. Recovery Study . A sample of Mb670 #b50 finished product Cashmere Bouquet Talc vas checked for chrysotile with the present method and gave zero % chrysoti]e. Chrysotile vas added to it for a recovery study. The results are listed in Table 5. Table 5 Recovery Study Total Weight in Grams $ Chrysotile $ Chrysotile ' of Talc and Chrysotile Added Found $ Recovery 2.5 0.2 0.33 165 2.5 0.5 0.6l 122 2.5 1.0 0.93 93 2.5 2.0 1.73 86 2.5 5.0 1.9 98 The very high recovery at the 0.2$ level and the more acceptable results at the 0.5$ level, limit the technique to the srder of Q.5$* QE-CPC00005076 - 11 - * DISCUSSION The method presented can be applied satisfactorily to detect chrysotile asbestos in talc. It was developed especially for the evaluation of chrysotile asbestos. In principle, however, it can be applied to any other type of asbestos subject to the limitation of producing suitable calibrations, The lower lir It of detection was calculated as 0.2%. Further improvement of the detection limit for this method will require the use of a more powerful x-ray tube, generator and-improved revolution provided by the use of a crystal monocromator, It was an unfortunate case that talc invariably contains, among other contaminants, kaolinite, making it difficult to use the more intense line (002) of chrysotile due to the proximity of kaolinite, 7-18 A , and chrysotile, 7-3 A lines. An early attempt to use this line after thermally destroying kaolinite at 500C proved that along with kaolinite some chrysotile was also destroyed. (3) Carrying the method furthe. to use the 002 line can be very rewarding for the sensitivity that ean.be attained, calculated to be b6% better. However, this is not without sacrificing a lot of time since the parameters involved are many. i H By looking at the less intense chrysotile line (00U), free of interference, and by selecting the propqr parameters, favorable results were obtained. ' Tetri time required for the analysis of a single sample is estimated at 3-1/2 hours. /' I I. i ' C t C QE-CPC00005077 - 12 * CONCLUSION AND RECOMMENDATIONS X-ray diffraction offers.a specific, accurate and precise method for the deterniination of chrysotile asbestos in talc at 0.5# and above. C ( QE-CPC00005078 13 INDEX TERMS 1, X-ray Diffraction 2, Chrysotile Asbestos 3, Talc o C c QE-CPC00005079 - lit REFERENCES 1 J. V. Crable, Am. Ind. Hygiene Assoc. Journal, p. 293, May-June (1966). 2. Analytical Data on Reference Clay material. "American Petroleum Institute Project Clay Material Standard", Columbia University New York, July 1950. 3- Klug and Alexander, "X-ray Diffraction Procedure" John Wiley &.Sons, Inc., pp. h08-ii09, Appendix V, p, 677* It, Danas, "Textbook of Mineralogy", H h Edition by W. E. Ford, John Wiley & SonsO', Inc. , 19^+2. 3. R. H. Jenkins and B. De Vries, Worked Examples in X-ray Spectrometry, Philips Technical Library Springer-Verlap, New York, Inc., 1970 6. P. Briscese Notes: Practical Applications "X-ray Powder Diffractometry". State University of New York at Albany. C QE-CPC00005080