Single Isotope Analysis
Nitrogen: 20 μg minimum is required for optimal analysis. Samples should not contain more than ~1 mg of carbon. If your C/N ratio is very high, such that you will exceed the acceptable C content to achieve the optimal N amount, we can analyze down to 15 μg N with acceptable accuracy and precision. Below this level, the δ15N value become less precise depending on sample type and homogeneity.
Carbon: The optimal range for C is 200 - 600 μg C, though we can analyze as low as 10 μg. Sample sizes that are consistent and close to the optimal amounts listed above will give the best precision and accuracy.
Dual Element & Isotope Analysis
Since the C/N of many materials do not allow one to target the ideal amounts of each element simultaneously, some compromise on sample size has to be made such that the carbon content cannot exceed 1200 μg and the N should not fall below 20 μg. If it is not possible to meet these criteria, then it may be necessary to analyze two separate samples.