Document VEZvL2NZ9zg5xrY2OZL2D9Mw

/ 'r r .4/moj/>/im'r L'nrirammni Pcriamon l"icss Iy7ti. Vnl. pf>. W.7 f.7U. I'riiucd in Cirijt 1111 u i n. PLAINTIFF'S V.XMlltlT l`l>-77 DETERMINATION Ol- CHRYSOTILE JN AIRHORN ASBESTOS BY AN INI RA-RED SI'ECTROMIiTKIC TECHNIQUE J. A. Ciadsdi.n. i. 1`amkik and W. L. Smith Warren Spring Laboratory. MinLtry of 7 cclinoloyy, StCM-naye, Herts., l.'.K, 1ins! i'i'ctmti/ 1 Jttnr I*>71) anti in Jittul Jurm If) Anvnn |y7o) Abstract--A new method of itcu-rninuiir. chrysolite in airborne ashestos usinc infra nil absorption at 2-77 |im is described. *1 tic tecbniitue is rapid. simple amt allo-as delceti-m ni chrysolite down to about 20 p;: in the sample, provided that the serpentine minerals of related structure (e g. Kaolinitc) are absent. is ruonuci ion Increasing attention is now being paid to the health hazards arising front the in halation of airborne asbestos (ll.M. Factory Insi'pctoraic, I96Ki. and in conse quence of this, improved methods for the determination of chrysolilc and other asbestos minerals in airborne dusts arc of wide interest. Recently Onouiii u> and Martindalc (1968) have reported an X-ray diffraction technique which possesses a number of advantages, but which needs about 30 mg of sample. In this note we describe an i.r. spcctromctric method used in this Laboratory for the determination of chrysolilc. The technique is rapid, simple and allows detection of chrysolilc down to about 20 /ig in the sample. The method suffers from the disadvantage of being non specific within the serpentine class of minerals. Jn the absence of other serpentine minerals e.g. kaolinitc, as was usually the case, the method is specific for chrysolilc asbestos, the form of asbestos most used commercially. .-:. * icr-'Y EXPERIMENTAL TECHNIQUE Chrysotile in common with other serpentine minerals possesses a sharp i.r. absorp tion band at 2-72 pm which is associated with the stretching vibration of the lattice hydroxyl groups present in the layer silicate structure. The band is fairly well .\epnraicd from the broad absorption arising from the free or weakly adsorbedwater molecules present in most solid samples (see Fie. 1). The analogous bands in the amphibolc asbestos minerals (amosite, crocidolite, etc.) are considerably weaker and are not Ti-irK1' suitable as the basis for an analytical technique. ... - In this work potassium bromide discs containing known amounts of chrysotile in the range 0-04-0-65 mg were prepared by the standard procedure (sec, for example. Martin, 1966). Values of extinction log,t>J0/f, where J0 and / are the incident and emergent intensities of radiation respectively, measured at the peak of the 2-72 /<n> %l ;.. band, were determined from spectra recorded on a Grubb-Pursons "Spectromaster" l.T. spectrometer, and were found to be proportional to the mass of chrysotile present in the disc (Fio. 2). The sensitivity of the method is such that at the lowest levels of chrysotile content (< 100 /rg) difficulties arose in preparing standard discs containing such small amounts of material; however, the calibration graph is sufficiently linear !.. to allow a reasonable extrapolation, and indicates a lower limit of detection of ~ 20pg. <7 SCF-FA-6312 PROW TOFTY pv crtt>r,