General Sample Requirements for regular AMS analysis
For analysis in one of our accelerator mass spectrometers (AMS), the ideal sample size is 1 milligram of pure extracted carbon. We routinely analyze much less than this (0.020 - 1 mg C), however the smaller the mass analyzed, the greater the uncertainty due to the effects of the process blank and fewer 14C counts detected (small mass means fewer carbon atoms and the older the sample, the fewer the radiocarbon atoms due to decay). While AMS allows the precise measurement of radiocarbon from tiny amounts of material, the potential resolution can easily be obscured by analyzing extraneous components or by the process blank.
The recommended sample sizes provided below are based on an ideal 1 milligram carbon sample mass for clean dry material free from impurities such as adhering sediment, rootlets or other extraneous materials.
The steps you take to prepare your sample for AMS analysis are by far the most important determinant of the quality of the radiocarbon result. Your choices define the sample and determine the scope of questions that can ultimately be addressed.
For information on how to submit samples click here.
General guidelines for 1 milligram extracted carbon sample size are provided below.
| Sample Type | Recommended Sample Size for AMS analysis | Pretreatment included |
|---|---|---|
| Inorganic Carbon Sample Type | ||
| Marine carbonates: | ||
| Foraminifera | 8-12 milligrams | |
| Coral | 8-12 milligrams | pre-acid etch upon request |
| Mollusk | 8-12 milligrams | pre-acid etch upon request |
| Otolith | 8-12 milligrams | |
| Water Dissolved Inorganic C (DIC) | depends on DIC concentration | |
| Sediment - carbonate minerals | depends on the % carbonate | |
| Carbonates - carbonate shell samples are expected to arrive free from sediments and extraneous material, ready to be directly acidified. To estimate the milligrams of carbon in carbonate, use the formula mg C = mg CaCO3/8.33 then multiply by 0.9 to account for impurities. If δ13C analysis is requested, this will consume up to 9 % of the CO2 generated via acidification. | ||
| Organic Carbon Sample Type | ||
| Plant/Wood | 3 mg | Acid-base-acid pretreatment applied |
| Charcoal | 5 mg | Acid-base-acid pretreatment applied |
| Sediment (OC) | depends on %OC | Acidification or acid fuming on request |
| Compound-specific (CSRA) | depends on %OC | |
| Water DOC | depends on DOC concentration | |
| Proteinaceous corals | 3-4 mg | |
| POC or aerosols on filters | depends on %OC | Acid fuming |
| black carbon | ||
| Pretreatment – Unprocessed plant based materials undergo a series of acid-base-acid leaches to remove any inorganic carbon or base-soluble organic acids prior to combustion. If your samples are very small and/or friable, we may contact you to discuss pretreatment options before processing them to decide on the best approach. | ||
| Gas Sample Type | ||
| Pure CO2 | 80 micromoles, 2-9 umols considered small | |
| Methane in gas or water | > 3 umols methane | |
| CO2 or methane in a gas mixture | > 3 umols | |
| Small sample fee/processing - samples yielding between 2- 9 micromoles CO2 (25 - 100 micrograms C) are considered small samples. An additional small sample analysis surcharge applies. See fees. | ||
| Other Sample Types | ||
| Graphite | 0.025 - 1 milligram C | |
| Contamination/swipe | ||
| Single Step Reduction for Organic Carbon Samples | ||
For information on the sample submission process click here.