Anion-specificity at water-air interface probed by total reflection X-ray fluorescence (TRXF)

► Br− adsorbed amounts in Stern and diffuse parts of EDL are determined. ► Br− is used as a probe for studying surface affinity of anions from Hofmeister series. ► Anions from bulk are capable of replacing Br− from the surface layer of CTAB. ► Hofmeister effect is observed in surface affinities of anions. ► ClO4− and I− show the highest surface affinity, while F− - the lowest.