In spite of the current prevalence of the CVD-based processes,the electric arc remains an interesting process for the synthesis of carbon nanoforms,thanks to its versatility,robustness and easiness.It also allows performing in-situ substitution of carbon atoms by hetero-elements in the graphene lattice.Our work aims to establish a correlation between the plasma properties,type and chemical composition(and the substitution rate) of the obtained single-wall carbon nanotubes.The plasma was characterized by optical emission spectroscopy and the products were analyzed by high resolution transmission electron microscopy and core level Electron Energy-Loss Spectroscopy(EELS).Results show that a high boron content leads to a plasma temperature decrease and hinders the formation of nanotubes.This effect can be compensated by increasing the arc current and/or yttrium content.The optimal conditions for the synthesis of boron- and/or nitrogen-substituted nanotubes correspond to a high axial plasma temperature associated to a strong radial gradient.EELS analysis confirmed that the boron incorporates into the grapheme lattice. In spite of the current prevalence of the CVD-based processes, the electric arc remains an interesting process for the synthesis of carbon nanoforms, thanks to its versatility, robustness and easiness. It also allows performing in-situ substitution of carbon atoms by hetero- elements in the graphene lattice. Our work aims to establish a correlation between the plasma properties, type and chemical composition (and the substitution rate) of the obtained single-wall carbon nanotubes. plasma was characterized by optical emission spectroscopy and the products by high resolution electron microscopy and core level Electron Energy-Loss Spectroscopy (EELS). Results show that a high boron content leads to a plasma temperature decrease and hinders the formation of nanotubes. This effect can be compensated by increasing the arc current and / or yttrium content. The optimal conditions for the synthesis of boron- and / or nitrogen-substituted nanotubes correspond to a high axial plasma temperature associated to a strong radial gradient. EELS analysis confirmed that the boron incorporates into the grapheme lattice.