La 135
18.9 h
ε, (β+), e-
γ 481

Chemical properties

La-135 is a radiolanthanide, usually in trivalent state. La3+ can be chelated e.g. with DTPA or DOTA. The ionic radius of La3+ is 103 pm, i.e. the largest among the lanthanides and close to that of Ac3+ which has 112 pm. It might thus serve as close surrogate for Ac-225 labelling studies.

Nuclear properties

La-135 decays by electron capture decay with a half-life of 18.9 hours to stable Ba-135. It has also tiny positron emission of only 0.007%.

La-135 emits X-rays, notably Kα at ≈32 keV (61.3(10)%) and Kβ at ≈37 keV (13.4(19) %). These energies make La-135 suitable for SPECT imaging with low-energy detectors. La-135 emits only few gamma-rays, namely at 480.5 keV (1.52%).

The mean photon energy per decay is 35 keV and the mean electron energy emitted per decay is 5 keV . Most electrons are short-range Auger electrons with <0.6 µm and <13 µm respectively . La-135 has therefore been proposed as therapeutic Auger electron emitter.


La-135 is produced by proton irradiation of enriched Ba-135 carbonate targets at the PRISMAP facility Hevesy Laboratory at DTU. After decay of short-lived co-produced activities a La/Ba separation is performed by multi-step ion exchange.


Activity will be shipped from Hevesy Laboratory (DTU, Risø, Denmark) to the users in form of La3+ solution.

Purity grades available


No carrier added (n.c.a.)

Half-life18.91 h
DaughterStable Ba-135
Branching Ratio/Decay99.993% EC, 0.007% β+
Purificationmulti-step ion exchange
Chemical FormLa3+ ion in 0.1 M HCl solution (1-2 ml)
Specific Activitytypical 1000 GBq/µmol La at End Of Chemistry
Radionuclidic Purity>99%
Radiochemical Purityt.b.d.
Chemical PurityMetal impurities determined by ICP-OES for each batch. Typical 25 nmol Al, 5 nmol Ba, 1-2 nmol Fe, Zn per batch (subject to revision).
Identification480.5 keV and 874.5 keV gamma lines present
AppearanceClear colourless solution
Activity available<1 GBq
AvailabilityUpon request
GradeResearch grade, n.c.a.
Other informationBioburden and endotoxin burden can be analysed post release, upon request.


  • Auger

Point of supply

  • Risø, Denmark

Involved production facilities

DTU, Denmark