# Isotope Provision

Isotope Provision

We have a laboratory dedicated to the clean and sterile provision of DLW and we are happy to ship globally.

If we enter a collaboration with your research group we will calculate the doses needed for both human and animal research studies. We can also provide advice on your study protocol and presentation and interpretation of the results.

### Calculating the dose of isotopes needed for DLW studies

Deuterium washes out of the body slower than 18oxygen, so we can use less of this isotope. We normally enrich with deuterium to half the extent of the 18oxygen. We recommend using 10% O18 for human studies, 65% for large animals and 30% for small animals/birds.

The minimum duration of an experimental measurement is dependant on the time taken for sufficient divergence of the labels to have occurred, and for sufficient isotope to have been washed out of the body (about 10% of the initial enrichment).

The maximum duration of an experimental measurement is set by the ability of the isotope analysis technique to separate the final isotope enrichment from the background enrichment (normally a minimum of 20 ppm excess).

To calculate the actual dosage, we multiply the desirable initial enrichment by the body water pool size of the animal/human and then divide this by the enrichment of the injectate:

dosage required (mls) = [0.65(Body Mass g) x DIE]/IE

The constant 0.65 is the approximate proportion of the body comprised of water. This is only an approximate figure, and, if specific information is available, it should be substituted at this point. DIE is the desirable initial enrichment (in ppm), and IE is the injectate enrichment (also in ppm).

For every 10 fold increase in body mass the desirable initial enrichment (DIE) halves:
DIE for an animal of 10g = 2500 ppm,
DIE for an animal of 100g = 1250 ppm,
DIE for an animal of 1kg = 625 ppm,
DIE for an animal of 10kg = 300 ppm,
DIE for an animal of 100kg = 150 ppm.
Beyond 100kg the desirable enrichment should remain fixed at about 100 ppm excess.

Animal example: for a 25g mouse injected with a 30% solution (ie 30% 18oxygen) the DIE would be 1907ppm.
The dose would be [0.65 x 25 x 1907]/600000 = 0.14mls

Human example: for a 70kg adult dosed with a 10% solution the DIE would be 169PPM.
The dose would be [0.65 x 70,000 x 169]/100,000 = 77.1mls