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.
Production
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.
Distribution
Activity will be shipped from Hevesy Laboratory (DTU, Risø, Denmark) to the users in form of La3+ solution.
| Parameter | Specifications |
|---|---|
| Half-life | 18.91 h |
| Daughter | Stable Ba-135 |
| Branching Ratio/Decay | 99.993% EC, 0.007% β+ |
| Production | Ba-135(p,n)La-135 |
| Purification | multi-step ion exchange |
| Chemical Form | La3+ ion in 0.1 M HCl solution (1-2 ml) |
| Specific Activity | typical 1000 GBq/µmol La at End Of Chemistry |
| Radionuclidic Purity | >99% |
| Radiochemical Purity | t.b.d. |
| Chemical Purity | 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). |
| Identification | 480.5 keV and 874.5 keV gamma lines present |
| Appearance | Clear colourless solution |
| pH | 1 |
| Activity available | <1 GBq |
| Availability | Upon request |
| Grade | Research grade, n.c.a. |
| Other information | Bioburden and endotoxin burden can be analysed post release, upon request. |