Preliminary theoretical studies revealed the selective complexation of bis (2-mercaptoanil) diacetyl (BMDA) with La3+ over several alkali, alkaline earth and heavy metal ions. Thus, novel PVC-based membrane (PBM) and coated graphite membrane (CGM) sensors for La(III) based on BMDA were prepared. The electrodes display Nernstian behavior over wide concentration ranges (i.e., 1.0×10−5–1.0×10−1 M for PBM and 1.0×10−6–1.0×10−1 M for CGM). The potential response of sensors was pH independent in the range of 4.0–8.0. The sensors possess satisfactory reproducibility, fast response time (