Quantification procedures based on the external calibration with total sum content standardization (ECTSCS) and the external calibration with internal standardization (ECIS) were compared in the analysis of glass materials by laser ablation inductively coupled plasma spectrometry (LA-ICP-MS) with a 213 nm Nd:YAG laser ablation device and a quadrupole mass spectrometer. Silicon was used as the internal reference element for ECIS. Applicability of these approaches was statistically tested using both homogeneous and inhomogeneous samples. The former type was represented by the standard reference material NIST 612 and an ancient glass bead (Early Bronze Age), while the latter was a mediaeval glass artefact (8th - 9th century). Homogeneity of samples was examined by EMP analysis. Identical results were obtained by both calibration methods for homogeneous samples, while underestimated contents resulted from quantification with ECIS method in comparison to EMP analyses of the same target area of inhomogeneous glass. Finally, elemental maps of zonal muscovite grain were recorded and quantified using ECTSCS method and verified by EMP analysis.