Sample Preparation Guide
Please send (electronically by e-mail and as a printout with the samples) an Excel-sheet containing sample weights and names.
Solid matter 15N or 13C-determination following elemental analysis
- Samples must be homogeneous (finely ground) and dry. Homogenization is not necessary if the sample is analyzed completely (e.g. whole individuals like ants, collembola, etc.).
Care should be taken during homogenization to avoid losing individual fractions of the sample (e.g., the lipid fraction in animal samples, which tends to stick in the mortar during grinding).
- Samples with natural 15N or 13C abundance must be processed and delivered separately from labeled samples.
- For samples with high C and N contents (e.g. plant samples) about 50 µg N and/or 100 µg C are ideal for the measurement (starting from approx. 2 µg N and/or C measurements are in principle possible). In the case of material with a high N or C content that is difficult to homogenize, it may be advisable to select higher sample weights. However, the sample weights must not exceed 100 µg N or 1000 µg C.
- In the case of samples with low C and N content (e.g. soil samples), weights of more than 10 mg should be avoided and the weights should be kept as low as possible in accordance with the (possibly estimated) C or N content. The target value in this case should be approx. 10 µg C or N. Weights above 30 mg are not possible.
- The weights should be selected in such a way that the C or N amounts of the samples of a batch do not differ too much.
- Samples weighed into tin capsules should be delivered in 96-well plates.
- Form tin capsules (use smallest tin capsules possible) into small balls (flat samples get stuck in the sampler).
- Tightly seal tin capsules, as stray samples will lead to contamination.
- Please make sure that the plates are tightly closed so that the samples cannot get mixed up.
CAUTION: There are lids with spacers (to allow evaporation) that should not be used, as this can easily cause sample disarray with very small samples.
- For every 10 samples, 2 standards must be weighed in. This is usually acetanilide and must be obtained from us so that the isotopic composition of the standard is known.
- The amounts of C or N in the standard must cover the same range as the C or N amounts of the samples.
- Please make sure that high and low amounts of standard are evenly distributed over the sample sequence, so that possible quantity and time drifts during the measurement can be distinguished from each other.
- For each uniquely (name, serial number, ...) identified sample plate, a file with sample names and weights and a printout should be included. Sample names should also be unique and in one single Excel column.
- Please use our weigh-in sheet file and indicate on it the approx C and N contents and the expected isotopic enrichment as follows: natural abundance, <100 permil, <500 permil, <5%, etc.
Please feel free to contact us in case of any uncertainties or special cases!
Prepraration of water samples for 18O and/or 2H analysis
- samples should be free of particulate matter (filter over 0,45µm. Attention: Do not use vacuum, this may lead to fractionation
- Samples should not be poisoned or acidified.
- Samples should be sent in small containers with only little headspace. Use glass vials to avoid evaporation and fractionation.