A novel, cheap and simple method for the determination of 10B and 11B mole fractions in 10B enriched boron compounds by capillary zone electrophoresis with indirect UV detection was developed. The background electrolyte contained 35 mM phenylalanine adjusted to pH of 8.8 with putrescine. The running conditions were + 25 kV at 34° C. Indirect photometric detection was performed at 210 nm. The analysis time was less than 17 min. The interday RSD of migration times and peak areas were less than 0.9% and 2.3%, respectively (n = 18). Linearity was demonstrated in the range 0.3–15 mM for both isotopes. Analysis of boron compounds with mole fraction of 10B ranging from 19.8 (natural abundance) up to 90.0% was successfully demonstrated.