Sample Handling and Pre-analysis Preparation

Most samples need some form of preparation before shipping to SIRFER. This preparation can be as simple as sealing liquid sample containers for prevention of evaporation or freeze-drying fresh samples such as leaves or tissue to as complex as delipification and extraction of cellulose from plant material. In the case of solid organic materials such as plant parts or soils, the samples must be dried and ground (<40 mesh). SIRFER will grind samples upon request for a nominal fee. Fresh samples, which require water extraction, should be frozen before shipping to SIRFER. Sample preparation and preservation of gas samples usually involves leak tight storage and avoiding isotopic exchange with polymer materials. For liquid samples, avoiding evaporation by sealing or freezing the sample is usually adequate.

SIRFER will accept bulk or pre-weighed solid samples for isotope composition. If you choose to submit bulk samples, the samples should arrive at SIRFER dried and ground (<40 mesh). SIRFER technicians will then weigh the samples into the appropriate capsule. Samples are routinely weighed to 1 µg before analysis. For δ13C, δ15N, and δ34S analysis of solid samples, a 0.2-20 mg aliquot of the sample is accurately weighed into a tin capsule. If the samples are not weighed immediately, the samples are placed into a dry storage cabinet. Weighed samples are stored in a vacuum desiccator until analysis. For analysis of solid (organic or inorganic) samples for δ2H and/or δ18O analysis, a 0.1-0.2 mg aliquot of the sample is accurately weighed into a pre-baked silver capsule.

Note on the submission of pre-weighed samples: because of instrument linearity issues, the elemental composition of the sample dictates the amount of sample weighed into either tin or silver capsules. Before submitting pre-weighed samples, contact the SIRFER laboratory manager for information on the appropriate weight.

Special requirements for soil analysis: SIRFER is an approved lab that can receive and process soils regulated by the USDA and APHIS PPQ. Because of specific handling and treatment requirements for regulated soils (both domestic and foreign) of the USDA, before shipping of any soils to SIRFER please complete the Soil Form.

SIRFER will accept freshwaters, saline waters and brines, and fresh plant and soil samples for δ2H and/or δ18O isotope composition. Saline waters may require vacuum extraction, and any water sample with visible suspended sediment in it requires filtration prior to analysis. Samples should be stored in tightly sealed, gas-tight containers with minimal headspace and sent to SIRFER as soon as practical after collection. Extraction of water from plant and soil samples or saline samples and other sample preparation can be conducted by SIRFER at additional cost. Clean freshwater samples can also be sent to SIRFER preloaded in 1.8 mL glass gas chromatography crimpseal vials. Pre-loaded vials should contain a minimum of 400 μL of the sample. Upon arrival, SIRFER stores liquid samples in a cold room or freezer. Plant and soil samples are frozen prior to water extraction

Clients who wish to submit isotopically enriched samples must contact the SIRFER manager ( prior to submitting samples. This email must provide information on the sample type, analytical services requested, the isotopic label used, and the estimated level of label present in the sample.

We can provide analyses on some enriched samples, but the precision of the analyses will be low due to the lack of reference materials required for a high-precision and accurate analysis. Depending on sample and label type, samples may be accepted. However, duplicate analysis is required to achieve acceptable analytical accuracy. If samples are accepted for analysis, the customer must agree in advance to pay a sample analysis cost that is twice the normally charged rate.

Artificially labeled samples (i.e. any sample derived from an experiment in which a substrate artificially enriched or depleted in one or more isotopes has been used) create special challenges in terms of calibration and correction for sample-to-sample memory effects, and can contaminate instruments with residual label that can compromise the analysis of natural abundance samples for days to weeks. Clients who submit labeled samples prior to notifying SIRFER and receiving permission to submit these samples for analysis will have their samples returned and will be responsible for the costs of any work performed prior to our discovering the presence of the label as well as costs associated with restoring SIRFER instruments to normal operational condition after the unexpected introduction of the isotopic label.

Optional SIRFER Services (per sample)

Soil acidification
Sample grinding
Sample weighing
Water extraction