Phosphorus-32 (14596-37-3) Physical and Chemical Properties
Phosphorus-32
A beta-emitting radioisotope of phosphorus commonly supplied for radiolabeling, tracer work and select therapeutic uses, delivered to laboratories as characterized activity under radiological controls.
| CAS Number | 14596-37-3 |
| Family | Radionuclides / Radioisotopes |
| Typical Form | Aqueous solution (carrier-free or buffered preparations) |
| Common Grades | EP, JP |
Phosphorus-32 is a radioactive isotope of the element phosphorus; it belongs to the class of radionuclides used predominantly as a beta-emitting tracer and therapeutic isotope. Chemically it is identical in electronic structure to the element phosphorus and participates in the same covalent and oxyanion chemistry as stable phosphorus, with the isotope most commonly encountered in biochemical and inorganic forms (for example as phosphate species). Molecularly the elemental symbol is \(\ce{P}\) and the labelled radionuclide is represented as \(\ce{^{32}P}\); when incorporated into compounds its chemical bonding, oxidation-state distribution and acid–base behavior mirror those of nonradioactive phosphorus.
Electronically, \(\ce{^{32}P}\) carries the same valence shell configuration as other phosphorus atoms and therefore exhibits the common oxidation states of the element (notably reduced phosphide-type species and oxidized oxyanions). In practical use the isotope is supplied and handled as inorganic phosphate or covalently bound organophosphorus tracers rather than as isolated elemental allotropes. Its radiochemical properties dominate consideration for handling, storage and application: \(\ce{^{32}P}\) is a pure beta emitter with substantial specific activity and a physical half-life appropriate for short-term therapeutic and tracer uses. Chemically it is hydrophilic when present as phosphate salts, generally non-volatile, and does not confer unique lipophilicity beyond that of the carrier molecule.
Common commercial grades reported for this substance include: EP, JP.
Basic Physical Properties (Density, Melting Point, Boiling Point)
Atomic Weight
Molecular weight (atomic mass) is reported as 31.9739076 \(\mathrm{g}\,\mathrm{mol}^{-1}\). The exact/monoisotopic mass is 31.9739076 (unit: atomic mass units).
Appearance and Physical State
Phosphorus-32 is encountered as an isotopic form of phosphorus rather than a distinct chemical phase. In practical and industrial contexts it is typically supplied as aqueous inorganic phosphate salts or as radiolabelled organic compounds; physical appearance therefore follows that of the carrier compound (aqueous solutions, salts, or conjugated tracers). Elemental phosphorus allotropes (white, red, black) are chemically identical in composition but are not the usual commercial form for the radionuclide.
Density
No experimentally established value for this property is available in the current data context.
Melting Point
No experimentally established value for this property is available in the current data context.
Boiling Point
No experimentally established value for this property is available in the current data context.
Chemical Properties (Reactivity and Oxidation States)
Oxidation States
Phosphorus in general exhibits multiple oxidation states; common formal oxidation states include −3 (phosphide), +1, +3 and +5 (phosphite/phosphate). The chemical behavior of \(\ce{^{32}P}\) reflects these same oxidation-state possibilities because isotopic substitution does not change electron configuration. In most biomedical and laboratory uses \(\ce{^{32}P}\) is present in the +5 oxidation state as phosphate oxyanions.
Reactivity with Air and Water
Elemental forms of phosphorus show allotrope-dependent reactivity (for example white phosphorus is pyrophoric in air), but \(\ce{^{32}P}\) is rarely handled as elemental phosphorus. In aqueous environments the isotope is most commonly present as phosphate species, which are stable in water under normal conditions. Oxidation–reduction transformations of phosphorus-bearing species follow standard phosphorus chemistry; the radiochemical half-life and decay emissions are chemically independent but determine practical stability and handling considerations.
Reactivity with Acids and Bases
Phosphate species containing \(\ce{^{32}P}\) act as typical oxyanions in acid–base equilibria and form soluble inorganic salts with alkali and alkaline earth cations and a wide range of metal complexes. Under strongly reducing conditions, phosphorus may be reduced to lower oxidation states; under strongly oxidizing conditions higher-oxidation-state oxyanions predominate. Hydrolysis and ligand-exchange behavior will be governed by the carrier molecule or salt.
Isotopic Composition
Stable Isotopes
The naturally abundant, nonradioactive isotope of phosphorus is \(\ce{^{31}P}\); it is the only stable isotope of phosphorus and is widely used in NMR spectroscopy due to its nuclear properties. Chemically, \(\ce{^{31}P}\) and \(\ce{^{32}P}\) are equivalent aside from radioactive decay.
Radioisotopes
Key radiochemical properties reported for phosphorus-32 include: Half-Life: 14 days; Decay Mode: Beta; Radiation Energy (MeV): Beta 1.71 (100%); Specific Activity: 285,000 Ci/gm. The isotope is a high-specific-activity pure beta emitter with a physical half-life suitable for short-term tracer studies and certain therapeutic applications. Critical organ deposition tends to be in bone when administered in phosphate form; internal toxicity is reported to be high for systemic incorporation. Regulatory and hazard summaries list an Annual Limit on Intake of 0.4 mCi in the cited hazard characterization.
Thermodynamic Parameters
Heat Capacity and Related Data
No experimentally established value for this property is available in the current data context.
Enthalpy and Gibbs Energy
No experimentally established value for this property is available in the current data context.
Identifiers and Synonyms
Registry Numbers and Codes
- CAS number: 14596-37-3
- Molecular formula: \(\ce{P}\)
- Molecular weight: 31.9739076 \(\mathrm{g}\,\mathrm{mol}^{-1}\)
- Exact mass / Monoisotopic mass: 31.9739076
- SMILES: [32PH3] (inline code)
- InChI: InChI=1S/P/i1+1 (inline code)
- InChIKey: OAICVXFJPJFONN-OUBTZVSYSA-N (inline code)
Additional computed descriptors: Topological Polar Surface Area = 0; Heavy Atom Count = 1; Formal Charge = 0; Hydrogen Bond Donor Count = 0; Hydrogen Bond Acceptor Count = 0; Rotatable Bond Count = 0.
Synonyms and Common Names
Reported synonyms and common names include: - Phosphorus-32 - 32P radioisotope - P-32 radioisotope - Phosphorus, isotope of mass 32 - 32P isotope - Phosphorus-32 isotope - Isotope:32P - 32P (isotope)
Industrial and Commercial Applications
Major Use Sectors
Phosphorus-32 is used in biomedical research and clinical settings where beta-emitting tracers or therapeutic beta irradiation are required. Major sectors include nuclear medicine and radiopharmaceutical research laboratories, where the isotope is used for both diagnostic labeling and certain therapeutic indications.
Typical Application Examples
Reported applications include therapeutic use in select hematologic and neoplastic conditions (historical and controlled clinical applications cited for conditions such as leukemia, polycythemia and certain other malignancies), and widespread use as a tracer in biochemical and molecular biology experiments (for labelling nucleic acids and other biomolecules). In practice \(\ce{^{32}P}\) is supplied as radiolabelled phosphate or covalently incorporated into target molecules for tracing metabolic, synthetic and pharmacokinetic pathways.
If an application summary above is not sufficient for procurement or process design, selection should be based on the radiochemical form, specific activity, and application-specific requirements described in product documentation.
Safety and Handling Overview
Storage and Handling Considerations
Phosphorus-32 is classified as a radioactive material. Key hazard parameters include Half-Life: 14 days and Decay Mode: Beta; Radiation Energy (MeV): Beta 1.71 (100%). Specific Activity is reported as 285,000 Ci/gm, indicating high activity per unit mass for typical preparations. The substance has been associated with significant internal toxicity and bone-seeking behavior when administered as phosphate; documented carcinogenic classification applies to internal deposition of \(\ce{^{32}P}\) in phosphate form (IARC Group 1 for phosphorus-32 as phosphate). Storage should follow radionuclide containment principles: secured, labeled shielding, inventory control, and decay-allowance strategies consistent with institutional radiation-safety programs.
Occupational Exposure and Protective Measures
Handling of \(\ce{^{32}P}\) requires radiation-protection controls appropriate for beta emitters: time, distance and shielding optimization; contamination prevention (gloveboxes, trays, absorbent barriers); use of appropriate personal protective equipment to prevent skin contact and inhalation; area monitoring and personnel dosimetry; and strict controls on waste segregation and decay storage. Because internalization (ingestion or inhalation) poses the principal health risk, administrative controls and training to avoid contamination are essential. For detailed hazard, transport and regulatory information, users should refer to the product-specific Safety Data Sheet (SDS) and local legislation.
