Isotope

The BIOGRIP Node for Isotope Biogeochemistry is located across and has access to several different laboratories in different departments at the University of Cape Town. These laboratories provide possibly the widest array of isotopic analyses available on the African continent, including both routine analyses, such as C isotopes of hair and bone, through to novel analyses, such as Pb isotopes of bronze artifacts.

The Isotope Node has several mass spectrometers and access to others, including 4 IRMS's for H, C, N, O and now also S isotopes of organic and inorganic materials, 2 multicollector ICP-MS's for Li, B, Sr, Nd and Pb isotopes, a LA-ICPMS for U-Pb dating of cave deposits, and a TILDAS laser instrument for triple oxygen isotope analysis of CO₂ gas.

The work done in these laboratories ranges from geological and planetary studies, through archaeological, oceanographic and environmental topics, to pollution, wildlife crime and climate change studies. We service a mixture of local and international researchers and are open to developing new capabilities and collaborations.

Isotope services

Download a list of analytical services available at this node, including details on how you can access these for your work.

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Analyses offered

The BIOGRIP Node for Isotope Biogeochemistry offers many analyses, including isotopes of those listed below. Specific analyses include:

C, N, O and S of organic materials such as bone collagen and plants
C and O in inorganic materials such as teeth
N and O of NO₃(aq) of ocean water or other natural waters
Li, B, Sr, Nd and Pb of material chemically processed into solution or by laser ablation
triple oxygen isotopes of CO₂₍g₎

Laboratory equipment

The BIOGRIP Node for Isotope Biogeochemistry infrastructure comprises a strategic mix of new, state-of-the-art instruments, as well as generational upgrades and critical support of existing instruments, supported by existing and newly established sample preparation laboratories:

The NuPlasma HR was upgraded by AJB Instrumentation (Wrexham, UK) in 2023 with enhanced pumping and electronics. It is predominantly used for Sr isotope analysis of solutions following chemical separation of Sr in the clean chemistry laboratory.
Sample requirements:
- Sample requirements differ depending on the user’s requirements. It is recommended users contact the lab in advance to discuss their particular needs.
- Typically, samples are submitted as homogeneous powders – enamel, rock powder, ashed organic etc – with a clear sample list, ready for dissolution.
The Plasma3 is used for Sr, Nd and Pb isotope analysis of sample solutions following chemical separation in the clean chemistry laboratory. This instrument equipped with two sets of resistors on 16 Faraday detectors, and switching between these allows the analysis of samples with either very low elemental abundances or very low total mass samples. An ASI RESOlutions 193nm laser ablation system with a large format sample cell can be coupled to the P3 for the in-situ isotope analysis of Sr in teeth, bone, minerals etc, and also whole-rock B and Li isotope compositions in nano-particle pressed tablets.
Sample requirements:
- Sample requirements differ depending on the user’s requirements. It is recommended users contact the lab in advance to discuss their particular needs.
- Typically, samples are submitted as homogeneous powders – enamel, rock powder, ashed organic etc – with a clear sample list, ready for dissolution.
- For isotope analysis by laser ablation, there are some restrictions as samples need to:
  - fit into the laser ablation sample holders;
  - have appropriate elemental compositions, e.g. high Sr and low Rb; and
  - couple with the laser. Whole-rock samples are prepared in-house as nano-pellets for Li and B isotope analysis by LA-MC-ICP-MS.
The new Delta V Plus is used to analyse carbon, nitrogen and sulphur isotopes in materials such as plant and animal tissues. This new instrument adds sulphur isotopes to our suite of possible analyses. Samples are weighed into tin cups using a microbalance, then combusted in an EA Isolink series elemental analyser (ThermoScientific) to convert them into CO₂, N₂ and SO₂. The gases are passed into the mass spectrometer via a Conflo IV gas control unit (ThermoScientific, Bremen, Germany).
Sample requirements:
- Sample requirements differ depending on the user’s requirements. It is recommended users contact the lab in advance to discuss their particular needs.
- Samples should be submitted prepared, dried, homogenised and (if possible) weighed, ready to be run
The Delta V Plus is used to analyse carbon and nitrogen isotopes in materials such as plant and animal tissues, soils and filter papers. Samples are weighed into tin cups using a microbalance, then combusted in a Flash 2000 series elemental analyser (ThermoScientific) to convert them into CO₂ and N₂. The gases are passed into the mass spectrometer via a Conflo IV gas control unit (ThermoScientific, Bremen, Germany).
Sample requirements:
- Sample requirements differ depending on the user’s requirements. It is recommended users contact the lab in advance to discuss their particular needs.
- Samples should be submitted prepared, dried, homogenised and (if possible) weighed, ready to be run.
Used in combination with a ThermoFinnigan Gasbench to analyse carbon and oxygen isotopes in carbon dioxide, or in carbonates such as carbonate rocks, tooth enamel, or ostrich eggshell. Dual inlet capability is also used to measure C, O and H isotopes in silicates and waters which have been prepared offline in the Department of Geological Sciences.
Samples are weighed into 12 ml borosilicate tubes closed with screw top lids containing a septum. The tubes are placed in a temperature-controlled sampler tray set to 72°C, then flushed with helium to remove the atmospheric gases. Five to seven drops (according to sample size) of warm (72°C) phosphoric acid are added to each sample tube by manual injection through the septum, using a 1 ml syringe, then left to react for a minimum of two and a half hours. The evolved gas is sampled by the autosampler and passed through a Nafion water removal unit, then a GC column to separate the gases and then through a second Nafion water trap. The purified gas is then passed into a Delta Plus XP isotope ratio mass spectrometer (IRMS) controlled by Isodat software.
Sample requirements:
- Sample requirements differ according to the material analysed and the user’s requirements. It is recommended that users contact the lab in advance to discuss their particular needs.
The tunable infrared laser direct absorption spectrometer (TILDAS, Aerodyne, Inc) is used for high precision measurement of δ¹³C and triple oxygen isotopes (δ¹⁸O, δ¹⁷O) of CO₂.
This instrument is interfaced with a carbonate digestion device for geological carbonates, and biominerals. It is capable of analysing 1 mg of carbonate material with a reproducibility of < 0.01 ‰. This instrument can also measure CO₂ from the atmosphere, as well as different combustion sources.
Developed as a collaboration between UCT scientists and Aerodyne, Inc., this is the only such instrument on the African continent, and makes the Stable Light Isotope Laboratory at UCT, as a BIOGRIP participant, one of only a handful of facilities worldwide capable of performing such high precision measurements.
Applications of triple oxygen isotopes are varied and include the quantification of sources and sinks of carbon dioxide, palaeohydrological reconstruction, and identifying long term changes in primary productivity.
Sample requirements:
- Sample requirements differ according to the material analysed and the user’s requirements. It is recommended that users contact the lab in advance to discuss their particular needs.
The Nu Instruments Attom ES HR-ICP-MS is coupled to an Applied Spectra RESOlution-SE 193nm excimer laser ablation system. The facility is a fast, highly sensitive instrument (i.e., <105ms), purposely designed to measure rapid and precise isotope ratio and quantitative analysis of trace elements in solid and liquid matrices.
The primary focus of the HR-ICP-MS is on Uranium-lead (U-Pb) dating, which facilitates dating of much older things, e.g, rocks and minerals, which are in order of millions of years old.

Affiliated centres

The BIOGRIP Node for Isotope Biogeochemistry works closely in collaboration with several partners. To learn more about these arrangements visit the BIOGRIP Affiliated Centres.

Laser Ablation and High-resolution Facility (LA-ICP-MS Lab)

The Laser Ablation and High-resolution Facility (LA-ICP-MS Lab) at the University of Cape Town specialises in high-precision elemental and isotopic analysis using laser ablation coupled with inductively coupled plasma mass spectrometry (LA-ICP-MS). This advanced lab supports a wide range of research applications, including geochemistry, environmental science, and materials analysis, by providing detailed insights into the composition of solid samples. Read more about the LA-ICP-MS Lab here.

Marine Biogeochemistry Lab (MBL)

The Marine Biogeochemistry Lab at the University of Cape Town focuses on studying the chemical processes and biological interactions in marine environments, particularly how they influence oceanic carbon cycling and nutrient dynamics. Through interdisciplinary research, the lab aims to enhance understanding of ocean health and its role in global climate change. Read more about the MBL here.

Multicollector ICP-MS Lab

The Multicollector ICP-MS Lab at the University of Cape Town is equipped with state-of-the-art instrumentation for high-precision isotopic and elemental analyses. This facility supports a diverse range of research in geology, environmental science, and paleoclimatology, providing critical data for understanding geological processes and changes over time. Read more about the lab here.

Stable Light Isotope Lab

The Stable Light Isotope Laboratory at the University of Cape Town specialises in analysing stable isotopes of light elements, such as carbon, nitrogen, and oxygen. This facility supports research in various fields, including paleoenvironmental studies and biogeochemistry, by providing insights into past climate conditions and biological processes. Read more about the lab here.