Submitting Samples for Analysis
Preparation of Solid Samples for Stable Isotope Analysis
1. Sample preparation will depend on the type of sample that you wish to analyze. We have in-house capabilities for all sample preparation techniques described below. Solid samples must be dried. Sample can be oven dried, only if the samples contain forms of N that won’t be lost through oven drying. Preferably, samples can be freeze dried. The laboratory contains a Labconco freeze dryer with 16 port-manifold.
2. Dried samples must be ground to a powder. Samples can be ground using a ball mill or manually using a mortar and pestle, depending on the sample type. This helps to ensure sample homogeneity. The laboratory contains a Spex SamplePrep 8000 Ball Mill/Mixer.
3. Samples may be lipid extracted. This is an optional step that can be taken when looking for δ13C and δ15N in tissues such as liver and muscle, or in other samples such as eggs. In the laboratory we add 2:1 Chloroform: Methanol to each sample. We then vortex and leave for a minimum of 24 hours. After 24 hours, we pour the contents of the vial through a filter into a previously weighed tin tray and rinse the tissues 2 more times with Chloroform: Methanol. After 24 hours, we reweigh the tin tray to get the amount of lipid present in the tissue. For accurate lipid extraction, a minimum of 0.5 grams of tissue is required. Lipid extractions may be performed with less tissue, but results may not be reliable. Alternatively, soxhlet extraction may be used.
4. Carbon and Nitrogen- Samples are weighed and encapsulated. Sample weight will depend on sample type. For most tissue samples between 400-600 µg are required for analysis. For plankton and soils samples between 3000-4000 µg are required. The sample is weighed into a special tin or silver capsule. Please note that each sample must be carefully prepared once weighed out into the capsule, and must be rolled and shaped into a ball. This helps ensure that samples do not get caught in the autosampler. In particular if samples are flat, the autosampler will not be able to operate and samples will be lost or ruined. Also note that large samples pose a problem and may not combust! Once samples have been weighed, we organize them into 96 well tissue culture plates. Please inquire before weighing samples as weights will vary depending on the tissue being analyzed
5. Sulphur- Each sample will need 0.3-0.5 mg of Vanadium Pentoxide added before encapsulation. For most tissues, between 3000-6000 µg are required for analysis. Please inquire before weighing samples as weights will vary depending on the tissue being analyzed.
If you choose to send samples that have not been processed please consider the following:
Send more sample than we require. We are only human, and there is that possibility that errors may occur while processing your samples. Therefore it is to your benefit to send more sample than is needed for analysis. As well, this allows for the possibility of external issues (such as shipping) or problems with instrumentation that we did not account for.
Keep labels simple and samples organized. If possible, keep sample names short and sweet! Sample labels are re-recorded throughout processing and analysis, by using short, simple and unique names for each sample, it helps ensure that sample names are recorded properly, and that if an error does occur it can be traced quickly. Additionally, including or emailing spreadsheets of all samples which are sent helps us to keep the laboratory organized. When possible, organizing your samples in boxes also helps us to process samples more quickly.