Radiochemical purity assessment

Monsanto Company relies very heavily on the use of high purity radiolabeled materials in obtaining regulatory environmental assurance data on its products. The ability to do rapid economical radiochemical purity assessments and preparative scale purification of tagged products that are often... 

Radiochemical purity assessment, 342 Radioscanners, 350 Raman spectroscopy, 222-223,230 combination of TLC and, 147 surface-enhanced, 34,223,836 Rare earth elements (REE), detection and identification of, 520... 

We have developed a new photoreactive analogue of paclitaxel, 3 -N-BzDC-3 -N-debenzoylpaclitaxel (109) and its ditritiated derivative ([3H]-109) has been evaluated for its ability to photolabel tubulin and P-glycoprotein.66 Radiolabeled photoreactive analogue [3H]-109 was synthesized by N-acylation of 3 -N-deben-zoyl-2, 7-bis(0-TES)paclitaxel (108) with N-(2,3-ditritio-3-(4-benzoyl-phenyl)propanoyloxy)succinimide ([3H]-107), followed by purification on a reversed phase semipreparative HPLC using a C-18 column (Scheme 21).66 Photoaffinity label [3H]-109 was assessed to possess >99.9% radiochemical purity and a high specific radioactivity (34 Ci/mmol). 

Chromatographic techniques have also been used to assess radiochemical purity on a routine basis and may be applied to both Tc preparations at the M level and c complexes... 

The following quality control methods can be adopted for assessing the radiochemical purity of the preparations. 

The results of the serum stability study are depicted in Fig. 13.4. During the 6 h incubation in human serum, the radiochemical analysis showed high labelling yield (>98%) for Y-DO IATATF . as assessed by HPLC, TLC and SepPak column. The Lu-DOTATATE preparation was also very stable (>98% radiochemical purity) when incubated in human serum up to 24 h. The... 

TLRC can be used for animal, human, and plant metabolism analysis radiochemical purity and stability assessment toxicology and biochemical studies and separation, detection, and quantification of separated radioactive zones of all compound classes. Traditional film autoradiography and LSC continue to be widely used, but phosphor imaging and layer scanners are being increasingly applied. The instruments for these methods are highly automated and... 

A radiopharmaceutical has adequate radiochemical purity when the fraction in the form of the wanted chemical form is high enough to meet specifications. Radiolysis (degradation due to own radiation) and the usual factors that affect stability (light, oxidation, reduction, pH shifts), may cause incomplete or slow labelling, degradation and create radiochemical impurities. Thin layer chromatography is the most widely used technique for the analysis of radiochemical purity. HPLC techniques may also be used, for instance for the assessment of the radiochemical purity of PET radiopharmaceuticals. 

The first important step in any radiochemical investigation is to assess the radiochemical purity of the starting material(s), and for this purpose TLRC can be, and is, routinely used. With modem instrumentation, quantitation of radiopurity can be quickly achieved using either one- or two-dimensional development. However, the following points should be taken into consideration. First, care must be taken with the application to the plate since poor application technique, overloading, or chemical decomposition on the plate can give rise to artefact information. Second, if the radiochemical is diluted with cold material to the required specific activity, then the radiochemical purity check should be carried out after the dilution, and it is advisable to carry out a chemical purity check as well. 

Applications include trace element determination in rocks, soils, biogenic samples, and pure metals by direct IDA, i.e., added radiotracer [2], [54], [60]. Another field of increasing importance is in radiochemical AA for assessment and improvement of accuracy at trace and ultra-trace levels by determination of the radiochemical yield. This applies primarily to biomedical samples, high-purity materials, and environmental materials 7]-[91, [32], [84],... 

TLC is still useful for rapid assessment of HPLC methods, because it provides rapid analyses with different mobile phases in much less time than required for reequilibration of HPLC columns. TLC is also practical for rapid qualitative analysis of reaction products from synthetic or semisynthetic reactions and for confirming purity of concentrated solutions, in which impurities might escape detection by HPLC. TLC is in fact preferable to HPLC for analysis of radiochemical impurities (degradation products) in radiolabeled retinoids and carotenoids, since in HPLC some impurities might not be eluted and detected radioactivity on thin-layer plates may be detected by autoradiography (exposure of the plate to x-ray film (98)) or by cutting the TLC plate into short sections which can be counted individually in vials by liquid scintillation. 

---