Dual-labelled water

Drug code labels come in many forms. One of the most reliable is the dual-labeled form, in which the code is covered by a mercury film that can be scratched off easily by a coin or similar blunt object to reveal the identity of the contents. Another effective type is the three-sided envelope A B C in front and C B A in back. Section C contains the written code and is sealed to part B. If an emergency arises, the detached code label portion is immersed in warm water for 2 minutes and then peeled apart. If the A B C form is used, the investigator should remove and save the coded portion prior to dispensing the medication, and attach it to the case report form. These labels are to be returned to the sponsor at the conclusion of the trial. If a code label is missing from a subject evaluation form, the sponsor may not accept that subject s data for statistical analysis. 

Automatic sample preparation methods for the determination of oarbon-14 and/or tritium, and carbon-14 and/or sulfur-36 in dual labelled samples by liquid scintillation counting are presented. The sample is burnt in a stream of oxygen, and the combustion products carrying radioisotopes are subsequently separated and collected for radioactivity determination. Tritium is measured as water, carbon-14 as "carbamate" and sulfur-35 as sulfuric acid. The procedures run automatically, they are free of memory effect and cross contamination, and provide quantitative recovery. 

Although indirect calorimetry has considerable advantages over direct calorimetry, it still only permits measurement of energy expenditure over a period of a few hours. A more recent technique permits estimation of total energy expenditure over a period of 1—2 weeks. This method depends on the administration of dual isotopically labelled water, The rate at which the labelled water is lost from the body is determined... 

Figure 5.1 The estimation of energy expenditure using dual isotopically labelled water...

A dual isotope labeling technique [85] has been used to measure membrane permeability in plant cells, based on the selective permeabiHty of the membranes of living cells to tritiated water and carbon-14 labeled mannitol. Kieran [29] showed that the results of the dual isotope labeling and Evan s Blue staining methods correlated well as indicators of cell viability however, the latter was preferable in terms of reagent cost and ease of analysis. 

The radiochemical analyses and purification of the Lu, and 1 labelled DOTATATE conjugates were achieved using an HPLC system. A dual pump HPLC unit with a C18 reversed phase column (25 cm x 0.46 cm) was used for purification of the labelled conjugates. Tire elution was monitored by UV signals at 270 nm as well as by radioactivity signals. The flow rate was maintained at 1 mL/min. Mixtures of 0.1% trifluoroacetic acid/water (solvent A) and 0.1% trifluoroacetic acid/acetonitrile (solvent B) were used as the mobile phases. The following gradient elution technique was adopted for the... 

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