Ca Method 4-1 Asbestiform Amphibole Minerals in Cosmetic Talc Part l: X-ray Diffraction Method Part ll: Optical Microscopy and Dispersion-Staining Method Introduction The method which has been adopted for the detection of amphibole minerals in cosmetic talc is the generally accepted method of x?ray diffraction. Methods which appear in the literature for the detection of fibrous amphibole, such as transmission electron microscopy with selected area diffraction1 and electron microprobe,2 have also been considered since they are capable of a lower level of detection than by may diffraction. However. they have not been adapted since they suffer from the drawbacks, that the amount of material under examination is quite small (less than a microgram) and the time for analysis, expertise required, and expense of equipment eliminates them as routine methods. The methodology presented is the most practical available, based on current technology. The use of Transmission Electron Microscopy with Selected Area Electron Diffraction offers greater sensitivity, but is not presented since it is unsuitable for normal quality control application. Enrichment or concentration techniques using flotation cells have been tried as a means of improving the detection level; however, all efforts solar have been unsuccessful. Principle The x-ray diffraction method is based upon the principle that when a material is placed in an x-ray beam, a portion of the x-rays are diffracted by each set of atomic planes within the The diffracted rays strike a scintillation counter as the sample is scanned through a prescribed angle with the resulting development of peaks corresponding to each interplanar distance A peak with value in the range of 8.04 to 8.85A for a sample talc is strong evidence for the presence of amphibole in that talc. The level of detection of amphibole by this method is 0.5% and above. The variability of detection is caused by such factors as age and manufacturer of x-ray dlifractometers, sample homogeneity. specific amphibole mineral present, morphology of amphibcle. particle size, preferred orientation. etc. For these reasons the level of detection should be reported for levels above since below this level the data has been found to be not reproducible. If a statistically significant peak is found of intensity equal to or greater than that obtained for the 0.5% standard in the range for amphibole, described above, then the sample must be put through the following confirming scheme: X-ray Optical Microscopy Stop (Amphibole absent) (Acid Leach) and Dispersion-Staining Color - Stop (Amphibole absent) Fibrous Morphology Slop (Asbestiform Amphibole absent) (4-) Stop (Asbestiforrn Amphibole present) The Cosmetic, Toiletry and Fragrance Association C- Method 4?1 Page 2 Part I: Minerals by X-ray Diffractornetry Apparatus 1. X-ray employing nickel-filtered copper K-a radiation, horizontal or vertical goniometer with variable scan speed capability, suitable talc pellet sample holder, variable speed recorder, electronic panel including raterneter and variable attenuation and time constant settings Hydraulic press, capable of attaining a pressure of 15,000 to 24,000 lb calculated on a 3" ram Mortar and pestle or grinding mill (Note 1) Waring Blendor,* or equivalent blender Spex Mixer/Mill,* or equivalent mechanical mixer Sieve, 325-mesh Optical microscope (Note 2) 1 pellet press Reagents 1. Standard talc sample. containing no detectable amphibcle minerals 2. Standard tremolite sample, at least 80% pure 3. Denatured ethanol 4. Boric acid Procedure The procedure consists of slow-scanning, under previously determined conditions, a compressed pellet of the sample talc in the 11.0 to 10.0% (8.85 to 8.04 A) region for the presence of an amphibole peak. There are timestwhen it is difficult to discriminate a possible peak for amphibole over the background noise level. Should the presence of a small amphibole peak above the background ?noise" be in question, it will be necessary to statistically evaluate the scan. A timer/scalar is required on the electronic panel of the x-ray di?ractometer. In order for a peak to be statistically significant, the peak intensity must equal or exceed three standard deviations (30) above the average background intensity (N): *Registered Trademark The Cosmetic, Toiletry and Fragrance Association C. Method 4-1 Page 3 Where So minimum peak intensity average background count 0 "Peak" I l' I 10.0 10.2 10.4 10.6 10.8 1L0 ?26 Figure 1. Determine the region of the scan in question: in the Figure 1 scan, a peak appears to be present in the ?0.40 to region. Slow scan with cumulative pulse counting through the peak region three separate times and average the number of counts. Determine a background count by scanning a region equal to 1/2 of the tee region covered by the peak, immediately, before and after the peak. The counting time for each of these background regions wiil equal 1/2 the total counting time used for the peak. Count each background region three times. Then average each region and add the two averages to obtain the background count (N). The Cosmetic, Toiletry and Fragrance Association Co Method 4-1 Page 4 Example: In Figure 1. Region Time (sec) Peak 10.40 to 0.60 120 Background Region A 10.30 to 10.40 60 Region 10.60 to 10.70 60 Background Peak Region A Region 10.401?0 10.60?20 10.30 to 10.40?20 10.60 to 10.70?20 time secs. counts time secs. counts time secs. counts 120 60,332 60 28,784 60 28,508 120 59,870 60 28,943 80 28,368 120 60,105 60 28,634 60 28,204 Average 60,102 28,787 28,359 - 28,?57 28,359 - 57,146 0? - ./57.r46 - 239 3d- 717 3c 57,146 717 57,863 The actual number of counts obtained for the integrated peak intensity was 60,102; therefore. the ?suspect" peak is statistically present in the scan. Standard Preparation Optimal instrument conditions must first be determined with the use of tremolite standards: 0.75%. 0.5% tremolite by weight, prepared in a standard talc which is free of interfering peaks in the 11.0 to 10.o?2e region. Weigh out appropriate amounts of standard talc and tremolite both of which have been ground to pass a 325- mesh sieve. Transfer to a Waring Blender.* Add 100 ml of ethanol to the blender and blend at low speed for 5 minutes. Carefully transfer the contents of the blender, with repeated ethanol washings, into a large beaker. Evaporate the ethanol on a steam bath. Shake the sample in a plastic vial for 5 minutes on a Spex Mixer/Mal" to remove stumps and caked sample resulting from the evaporation of ethanol. Determine by microscopy the homogeneity of the prepared standard previous to the x?ray diffraction analysis. Press the homogeneous standard into a 1 pellet with a backing of boric acid. Transfer 2 (10.2) of standard to the die-holder and evenly distribute on a polished, scratch-free die. Distribute 4 (10.2) of boric acid evenly on the talc layer. Press the mixture into a pellet under conditions suitable for obtaining a smooth planar surface (for example, a pressure of 15.000 to 24,000 lb calculated on a 3" ram has been found-to produce suitable pellets). The resulting pellet must have a talc face which is free of flaws; if not, the pellet must be discarded (Note 3). Prepare two acceptable pellets from each standard. *Begistered Trademark The Cosmetic, Toiletry and Fragrance Association C- Method 4-1 Page 5 Sample Preparation Prepare two peilets from each sample in the manner described for the standard pellets. Make a qualitative scan from 4 to 50?28 on one of these pellets to ascertain the presence of amphiboie above the 2% level or the presence of mineral impurities having interfering peaks in the 11.0 to 10.0?26 {8.85 to 8.04 A) region of the scan. The presence of such interference will eliminate use of the x-ray diffraction method for the sample, and one will have to proceed directly to the microscopical procedure. instrumentation instrumental variables are optimized on the 1% standard. Lower standards are then analyzed under the optimum conditions to determine the lower level of detection. Of major importance in obtaining maximum instrument sensitivity are a slow dittractometer speed combined with compatible recorder speed. and high attenuation combined with a statistically acceptable time constant on the raterneter. Under appropriate instrumental conditions the peak obtained for the 0.5% standard should be detectable above background noise as shown in Figure 2. Typical instrumental conditions employed for the Siemens Diffractometer (Model No. and Counter and Recorder Unit (Type T) are: Radiation: Co with Kb filter at 40 KV and 24 me Divergence slit: 1? Receiving slit: 0.2 mm Goniometer speed: Vows/minute Recorder Speed: 300 mmihour Attenuation: 1 103 impulses/second Time constant: T(s) 4 Statistical error of 1.1% under these conditions Rise Time 0.18 Attenuator 20 The Cosmetic, Toiletry and Fragrance Association C- Method 4-1 Page 6 0.5% Tremolits in Talc 3?0? Mm9.5 10.0 10210.4 10.6 10.0 It!) 11.4 02. Figure 2 X-Ray Diffraction Scans Place the standard or sample pellet in a suitable holder and slowly scan between 11.0 and 10.0?28. Then rotate the pellet 90? with respect to its original position in the goniometer and rescan between 11.0 and 10.0?28 since pellet orientation may affect peak intensity. The presence of a reproducible peak (or peaks) is due to the presence of amphiboie mineral (or minerals): the absence of peaks in this region indicates the absence of amphiboie in the sampie! within the limit of detection of this technique. Report results as ?None detected" or as ?Detected approximatety level." where equals the level detected. The Cosmetic, Toiletry and Fragrance Association C- Method 4-1 Page 7 Part ii: Asbestiform Amphiboie Minerals by Optical Microscopy and Dispersion-Staining Apparatus 1. Polarizing microscope. Best results will be obtained it the instrument includes the following: a. individually centering objectives b. Bertrand lens 0. High-intensity light source d. Centering condenser/substage 2. Dispersion-staining device (Note 4) 3. Vacuum filtration equipment, including either a porcelain cone with glass fiber filter mat or a porous glass bottom cup Reagents Hydrochloric acid. 10% WV 25 2. Cargilie immersion liquid Series HD, nD 1.605 (Note 5) Procedure Acid Treatment Because of the interference caused by Some carbonates calcite) in the detection of asbestitorm amphiboles in talc by optical microscoPWdispersion-staining, it is necessary to first remove these carbonates by a simple acid leaching procedure: Weigh out 2 of the talc into a ?100 mi beaker. Add 25 ml of 10% v/v i-lCl slowly (to prevent excessive evolution of gas it carbonates are present) and heat, with occasional stirring on a steam bath for 30 minutes. Filter with vacuum filtration equipment. and wash several times with hot water. Dry the talc. Optical Microscopy and Dispersion-Staining Carefully disperse 0.1 mg of talc in one drop of Cargiile i-lD liquid. has 1.605, and cover with a clean cover slip. - Examine the sample in the dispersionQStaining central stop mode. The sobstage diaphragm should be almost completely closed. the field diaphragm may be partially closed to enhance color contrast, and the polarizer should be in position. Tremolite, actinolite and presumably other amphiboie minerals, under these conditions, will show the following dispersion~staining colors: yellow changing to blue with rotation of the sample relative to the poiarizer'or yellow changing to orange with rotation. The variation of the color change is due to the fact that the tremoiite may lie in one of two positions relative to its principal optical orientation. The Cosmetic, Toiletry and Fragrance Association Co T-F-A Method 4-1 - Page 8 Examine the sample for asbestiform fibrous amphibole minerals. In order for an amphibole mineral to be considered asbestiform fibrous it must meet the following OSHA definition (Reference 4). 1. Particles must appear to be fibrous rather than as or slivers. 2. The maximum diameter of a fiber to be counted in 3 microns. 3. The maximum length of a fiber to be counted in 30 microns. 4. The length to width ratio must be 5 or more to 1, that is, 5 times or more longer than wide. 5 . The separate or individual fibers must contain fibrils or the ?bundle of sticks" effect, unless they are at a nondivisible stage. A fibril cannot be subdivided and would be counted. if it meets the other criteria. The length to width ratio of 5 or more to 1 is not meant to imply that other particles are not hazardous. Report results as ?Asbestiform Amphibole Present? or as ?Asbestitorm Amphibole Absent.? It is imperative that both dispersion-staining color and fibrous morphology criteria be satisfied before identifying a particle as asbestiform amphiboie, since other substances may show colors similar to those described. Notes 1. Talcs to be analyzed and the tremolite used to prepare standard samples must be finer than 325 mesh (maximum particle size of 44 microns). The Tekmar Analytical Mill (Model A-10) is available from: Tekmar Company PO. Box 37202 Cincinnati, Ohio 45222 2. It is important that the homogeneity of the prepared talc-tremolite standard samples be verified by optical microscopy. 3. This requirement is critical since excessive surface scatter will cause abnormatly high background count 4. The only commercially available dispersion-staining device is available from: Walter C. McCrone Associates, inc. 2820 South Michigan Avenue Chicago. 60616 5. Available from: Ft. P. Cargille Laboratories. inc. Cedar Grove; New Jersey 07009 ?or from laboratory suppliers. References 1. Rohl, A. N., Langer. A. M., Environmental Health Perspectives 9, 95 (1974) Rubin, l. B., Maggiore. O. J., Environmental Health Perspectives 9, 81 (1974) L. S. Birks, X-Flay Spectrochemical Analysis, pages 54- 55, lnterscience Publishers (1959) ?Tremolite and Talc." U. S. Department of Labor, Occupational Safety and Health Administration, Field Information Memorandum #74?92, November 21, 1974 are? 1' ?k The Cosmetic, Toiletry and Fragrance Association