Full custom radiolabeling with tritium
PerkinElmer has years of experience in custom synthesizing and purifying a wide variety of tritium-labeled compounds. We prepare them using a wide variety of procedures aimed at yielding high specific activity and purity.
Submitting samples for tritium labeling
With PerkinElmer's Tritium Labeling, you provide the precursors of the compounds to be labeled.* You will receive specific packaging, labeling, and shipping instructions from our Custom Services Technical Administration Group, or your local sales office or distributor, when you place your order.
Because impurities may complicate the labeling process or cause it to fail, PerkinElmer recommends that only chemically pure compounds be submitted for tritium labeling. Your precursor is used as received, without analysis, testing, or verification.
Catalytic reduction service with tritium gas
PerkinElmer will perform tritium gas catalytic reductions on compounds you submit. Just provide the precursor, confirm the conditions for the reduction, and note any special requirements (such as specific activity desired, sensitivity of the compound to pH, heat, etc.). This method is the preferred procedure for labeling a compound with tritium, provided a suitable unsaturated or halogenated precursor can be obtained. Advantages of this method are:
- Typical specific activities in the range of 20-30 Ci/mmol
- Purity of the tritiated product
- Predictable positions of labeling
Reduction service with [3H] sodium borohydride
PerkinElmer applies tritium-labeled sodium borohydride to reduce ketones and aldehydes to alcohols, even in the presence of other reducible groups, such as esters, acids, and nitriles. This reagent is often preferred over [3H] lithium aluminum hydride, because of these features:
- Reductive selectivity
- High specific activity (¢10 Ci/mmol)
- Ease of handling
- Low cost
*Due to the nature of this process, the precursor may be destroyed in whole or in part during the labeling process. PerkinElmer accepts no liability or claims of damage for destruction of the precursor. Excess precursor will be discarded unless other arrangements are agreed to in writing.
Catalytic exchange with tritium
PerkinElmer offers you a resource for performing a catalytic exchange in a solvent - an important technique for random tritium labeling. Usual solvents include water, glacial acetic acid, dimethylformamide, and other aprotic solutions, while noble metals are the typical catalysts. Both tritium-labeled water and tritium gas are used as sources of the isotope.
If you are supplying aromatic compounds, PerkinElmer can effectively label them using an acid-catalyzed (particularly trifluoroacetic acid), tritium-labeled, water exchange procedure. In this catalytic exchange, impurities often increase proportionately with the specific activity, although this occurs less frequently with reduction methods. Nevertheless, PerkinElmer can assure adequate purity levels within a specific activity range by simply using standard purification techniques.
Catalytic exchange is performed by stirring the materials (0.1 - 0.3 mmol) at room temperature (for gas) or 50-100_C (for tritiated water) for 16 hours or more. The success of the method depends on the stability of the compound under these conditions.
On the other hand, catalytic exchange using tritium-labeled gas as the source of the isotope is particularly effective for nucleosides, nucleotides, sugars, and amino acids. This is a very mild technique that usually results in specific activities greater than 1 Ci/mmol and retention of stereochemical integrity.
Tritium gas exposure labeling
PerkinElmer offers a simple approach to random labeling of organic molecules with tritium - tritium gas exposure. Using this method, your compound is sealed in an ampoule containing carrier-free tritium gas and kept in this ionizing field for several weeks. Although this method produces relatively low specific activities (1 to 125 mCi per gram of purified compound), it is, for some compounds, the only practical, cost-effective labeling solution. For example, it lets us successfully label a variety of steroids, hormones, enzymes, pharmaceuticals, and other complex compounds.*
*In tritium gas exposure labeling, considerable radiation decomposition of the organic material occurs, causing the formation of high specific activity contaminants. Before you decide to use the tritium gas exposure method, carefully examine the practicability of other labeling methods and use them instead, if possible. We will be happy to assist you in the decision-making process.
In general, the highest specific activities are obtained when the sample is kept small (no more than 1 gram for 15 Ci exposure). Large samples should be finely ground. We will return the labeled compound to you about five weeks after you submit it to us.
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