Glass classification by linear discriminant analysis of LA-ICP-MS data

The classification of pharmaceutical and common glasses (ampoules, infusion bottles, cylinders, lead crystal and bottle glass) has been performed means by of chemometric methods. For this purpose intensity data of glass examinations received by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) were applied. A Nd:YAG laser with 10 Hz repetition rate in the Q-switch mode at its 4th harmonic (266 nm) was used to get mass spectrometric data of the glasses. 13 isotopes (= variables) were used for measurements (7Li, 11B, 23Na, 24Mg, 27Al, 28Si, 39K, 42Ca, 47Ti, 57Fe, 123Sb, 137Ba, 207Pb). The glass samples represented four types of glasses: 1. borosilicate glass (type "Duran") 2. borosilicate glass (type "Fiolax") 3. soda-lime glass 4. lead glass. Calculations were made by using the SAS statistical software. All results were obtained on the assumption that the underlying data are normally distributed. By applying linear discriminant data analysis a classification of all types of the glasses was possible (13 variables included). The use of the method of "stepwise discriminant analysis" reduced the minimal required number of variables to eight. All types of glasses could be distinguished faultlessly. Besides a graphic system consisting of the isotopes 24Mg-47Ti-137Ba was developed. By means of this system optical distinction of glass classes was possible. The developed method allows to distinguish several types of pharmaceutical and common glasses on the basis of intensity data of mass spectrometric measurement without calibration experiments and linear regression.