La 135
18.9 h
+ 0.18)
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 a tiny β+ decay branch with 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 γ-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 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.)

Production routeBa-135(p,n)La-135
DaughterDecays to stable Ba-135: 99.993% EC, 0.007% β+
Half-life18.91 h
ProcessingMulti-step ion exchange chromatography
Primary Container2.5 mL borosilicate glass V-vial with silicon rubber screw cap
Product Graden.c.a.
Physical FormLiquid
Chemical FormLa3+ ion in 0.1 M HCl solution (1-2 ml)
Radioactive Concentration (gamma spectrometry)n.a.
AppearanceClear colourless solution
Radionuclide identification (gamma spectrometry)481 keV and 875 keV gamma lines present
Radionuclidic Purity (gamma spectrometry)>99%
Chemical purity (ICP-OES)Metal 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)
Molar activity (ICP-OES)Typical 1000 GBq/µmol La at End Of Chemistry (>15% of theoretical maximum)
Apparent Molar Activityn.a.
Microbiological qualityBioburden and endotoxin burden can be analysed post release, upon request.
Bacterial endotoxinBioburden and endotoxin burden can be analysed post release, upon request.
pH (pH strips)1
Additional information
Activity available< 1 GBq upon request
Activity limit for UN2910 (excepted package) shipment20 MBq in dry state or 2 MBq in liquid form
Other information


  • Auger

Point of supply

  • Risø, Denmark

Involved production facilities

DTU, Denmark