Waikato Stable Isotope Unit (WSIU)

Routine Sample Preparation

Samples are normally submitted for analysis as very finely ground (‹200 µm) oven dried material. Processing to this stage is by the customer, and our charges are based on this assumption. Normal laboratory grinding procedures are usually sufficient to ensure good precision in 5-10 mg samples. In many instances, small samples of dry material can be ground in a mortar and pestle. Some materials such as dry fish tissue, can be readily ground under liquid nitrogen. For larger quantities of material, a mechanical grinder is more suitable, and for variable material, a ball mill is best. The homogeneity of the sample is one of the major variables in the precision of the analysis.

Samples should be packed in small plastic or glass vials and labelled carefully. We are happy to return unused material to you at your cost. Liquid samples can be processed, but must be reduced to a small volume (50 µL). Gaseous samples, such as breath, can also be processed. For more information on preparation of these, please refer to the Breath Samples section.

Sample Analysis

Samples are weighed with a 6-place high precision microbalance.

Carbon Analysis:

Routine-precision analyses for C content and 13C are carried out on samples containing 100 to 1000 µg C. Dry plant leaf material and animal tissue typically contain roughly 40% C by weight thus optimum sample size is 2-4 mg. Up to 50 mg of tissue (solids or liquids can be processed in any one analysis. For gas samples, such as breath, a usual sample size is 10 ml.

Nitrogen Analysis:

Routine-precision analyses can be carried out on samples with as little as 20 µg of N. However, optimum sample size should consist of 300 µg of N. Soils pose particular problems if the N content is low, requiring larger samples. Up to 50 mg of total sample can be processed in any one analysis.


Mailing and Turn-Around Time

Samples can be sent through the regular mail, by international courier service, or by air freight (find out how). If your samples are non-viable, they should not be held up. Clear marking will help to speed up transit. Heat-treated and ground material can usually be labelled:


We endeavour to process samples as fast as we can, and batches of 100-500 routine-precision isotope analyses normally take no more than 3 to 6 working weeks, excluding transit time. We will advise you when we receive your samples, and indicate when results will become available. If for some reason we cannot meet this date, we will advise you immediately.


All care is taken by The University of Waikato, and the Waikato Stable Isotope Unit to provide accurate, standardised results. All analyses are bracketed with known standards which are related to the common isotope standard. While the University undertakes to implement the best possible analytical techniques and procedures, it cannot be held liable for the way in which the results are used by clients or third parties.

Routine samples

Find out how to prepare and submit routine samples for analysis.


For the latest equipment and analytical costs for external clients, please refer to the Science & Engineering Services Fees Schedule.