LUOMUS

Luonnontieteellinen keskusmuseo

Stable isotope determinations

The atoms of an element can have different amount of neutral particles, neutrons, in their cores. Atoms with different amount of neutrons are called isotopes and non-radioactive isotopes are called stable isotopes. Even though different isotopes have similar chemical properties, small difference in mass between the atoms can cause different behaviour in physical processes and chemical reactions. As a result of this the original isotopic composition can change. The changes are usualle very small and they are measured using Isotope Ratio Mass Spectrometer (IRMS).

The change in the isotopic ratio can indicate how the compound or material was formed or what were the conditions, such as temperature. Due to this, the stable isotope ratios are commonly used when determining things like origin of substances or process chains related to them and they are also widely used in environment or atmospheric research, genuinity and origin research and industrial applications, such as food and beverage industry. Current study projects in Luomus concentrate on environmental changes determined by studying the isotope ratios in tree-rings and on the diets of past humans and animals by studying the isotope ratios of bones.

Delta V Plus isotope ratio mass spectrometer

 

 

 

 

 

 

 

 

 

 

 
 
 

Analytical services for stable isotope analysis

The Laboratory of Chronology offers stable isotope analyses first and foremost for scientific research projects. Collaborative research is prioritized, but time permitting the laboratory provides stable isotope analytical services also for non-collaborative research and non-academic customers.

As a rule, the laboratory accepts only natural abundance samples for analysis, i.e. isotopically labelled substances are not accepted for analysis. Any materials that have been isotopically labeled will not be analyzed, and if such samples are submitted without notice, any loss of instrument use time and possible maintenance will be charged to the customer.

Routine services:

  • δ13C and δ15N analysis of organic solids like plant material, fungi, antlers, horns, hair and skin
  • δ13C and δ15N analysis of collagen extracted from bones and teeth
  • δ13C and δ15N analysis of soils and sediments (C and N content limits apply)
  • δ18O analysis of organic solids like cellulose, plants, insects, hair, nail, wool
  • δ13C and δ18O of calcium carbonate
  • ẟ2H and ẟ18O of fresh water 

We also perform the following analyses, inquire for details and availability:

  • δ18O analysis of phosphate extracted from skeletal samples
  • δ34S analyses of certain sulfides, sulfates and organic solids

Routine pretreatments and extractions:

  • weighing into analysis
  • sample drying (warm/ freeze-drying)
  • sample homogenization (ball-milling or manual)
  • carbonate removal/acid fumigation
  • cellulose extraction from wood chips (ask for details)
  • collagen extraction from bone and dentine
  • silver phosphate extraction from skeletal samples

If you are interested in a pretreatment not listed above, please contact us at stableisotopes@helsinki.fi, and give the full details of the procedure including a description of the chemicals and equipment used and we will get back to you. Time permitting, custom procedures may be developed, but these are usually related to collaborative research projects.

General:

If you are interested in the analysis of organic solids (other than collagen) for δC/N/S/O, we need you to provide a best guess estimate of the weight-% of the element(s) of interest in your samples for us to evaluate whether they can be analyzed or not. Search for mean values from scientific literature if you have no measurement data for your own sample set. If you will do the weighing of samples for the isotopic analysis yourself, we will provide you with a sample size calculation form that gives you the necessary weighing amounts based on your estimated element weight%.

For isotopic analyses of C and N, the material must contain at least 0.2% of the element of interest. In some cases we can measure samples down to 0.1% at an additional charge, but the feasibility is reviewed on a case by case basis.

The isotope values for both carbon and nitrogen (ẟ13C and ẟ15N) values of materials with a low C/N ratio can be analyzed in a single run thus lowering the analytical cost per sample. For example most animal tissues like hair and nails have a sufficiently low C/N ratio for this type of analysis. For high C/N ratio materials, such as plant tissues, soils and sediments, two separate subsamples must be weighed that are analyzed in two separate runs to obtain both ẟ13C and ẟ15N values.

Depending on your sample material and desired analysis, you may want to consider analyzing replicates, for example to get an estimate of the effects of material heterogeneity on ẟ-value precision. This is especially recommendable for soil and sediment materials, and ẟ18O analysis of solids in general. We recommend choosing a representative set of samples, e.g. 10-30% of total sample number, to be analyzed in duplicate or triplicate.

The schedule:

The normal turnaround time for routine services when received ready for measurement is 1-2 months. You may ask for possibilities of expedited service at additional cost, but this may not be available. Turnaround times may be somewhat longer during the general holiday seasons in Finland, i.e. the turn of the year and summer holidays around July.

The timetable for analysis is affected by any additional services required. If you are submitting samples that are ready for analysis, i.e. you have already weighed the proper amount into the analytical vial, you will receive results faster. We also provide sample weighing for analysis as a service but it will make the turnaround time slower. Please ask for estimated timetables if you require weighing or other pretreatment services.

The timetable for analysis is affected by the number of samples submitted. Small projects may be analyzed within a week or two if they happen to fit an existing planned run with empty sample slots.

Pricing:

Pricing is available upon request. Please note that prices are charged per sample replicate. Minimum charges apply for very small projects.

There are two price categories for analytical services at the University of Helsinki. Internal pricing is applied to projects that have an existing wbs code within the University of Helsinki’s finance system. Internal prices do not contain VAT nor a profit margin. External pricing is automatically applied to all other projects. Unfortunately this also applies to projects within the University of Helsinki, if the funds are not managed within the University (e.g. personal grants of UofH researchers). External pricing includes a profit margin and will also incur a VAT of 24% to be added to services charged.

Contacting laboratory staff:

Before submitting samples, contact laboratory staff at stableisotopes@helsinki.fi. You may also use this email address for queries about prices, timetables or other questions not covered here. When contacting the lab for scheduling, pricing and feasibility, please include the following information to help us provide you with the correct answers:

1) sample material in as much detail as possible, i.e. not just “sediment” but e.g. sulfate rich sediment from the Baltic Sea; not just “water” but precipitation or lake water from Lapland; not just (archaeological) “food crust” but food crust from Åland island with very little organic content and a lot of pottery material;

2) the expected (measured or estimated) content of the element you want analyzed, especially important for soils, sediments and other unusual materials not covered by the examples in “Routine services;

3) number of samples and replication (analysis in duplicate or triplicate), and the resulting total number of analyses requested - if you are interested in several different isotope analyses, give sample/replication numbers for each analysis separately;

4) desired isotope analysis/analyses;

5) any additional services required (weighing, pretreatment);

6) any prior treatments done to the samples;

7) If asking for pricing a) will the project be charged to a University of Helsinki wbs account, or payed externally; b) in case of external pricing, will the invoice be paid by a private person, a non-profit organization or a commercial company.

Sivun vastuuhenkilö: 
Eero Tirkkonen
25.1.2021