Tips for Compound Specific Analysis of 2H and 13C in n-Alkanes
Sample preparation
We recommend shipping samples dry; shipment of solvents requires handling as dangerous goods and incurs additional shipping fees. If shipping samples in solvent, please do not overtighten your vial caps. Samples leak out of vials with over-tightened caps. Turn caps until snug, but not so far that septa start to pucker.
We recommend using an internal standard if you intend to account for extraction efficiency in concentration data. Please avoid the use of small chain FAMEs, as we often use these compounds as internal standards for calibration of isotope-ratio measurements.
Please inspect your data. We provide the identification of n-alkanes, however we also report data for all detectable, yet unidentified, peaks. This allows you to decide which data to keep and which ones to discard. Very small peaks (< 1 V-s) may have biased values that should be ignored, especially when closely eluting to much larger peaks. Further, when large peaks are not fully resolved, the δ13C or δ2H measurement for each approaches the average of the two peaks. This is because the IRMS measurements take place on the combustion/pyrolysis products (CO2/H2) following chromatography and cannot fully discern the CO2/H2 from either peak.
Quality Assurance
Every SIF data report contains results for a range of calibrated quality assessment reference materials that were co-measured with the project. However, as for all analyses, we recommend that clients submit a quality assurance material to allow for their own monitoring of batch-to-batch variation over time and consider the submission of sample duplicates[1]. Ideally, these QA materials should be similar to the sample materials you intend to measure. Requirements for material preparation are the same as those for all sample materials.
Scheduling
The queue for CSIA at the SIF often extends several months. We recommend that you contact us about your sample submission as early as possible to expedite your project analysis.
Supplies
|
Manufacturer / Part# |
Description |
Unit |
|
National Scientific / C4000-2W |
Screw-Thread Vials 9-425, 2 mL Amber with ID Patch |
100/PK |
|
National Scientific / C4000-53B |
Blue Screw Caps, Red PTFE/White Silicone/Red PTFE |
100/PK |
|
National Scientific / C4010-630 |
Poly-spring Glass Inserts 300 µL |
100/PK |
|
National Scientific / C4012-25 |
Storage rack for 50 vials, polypropylene, without lid |
EACH |
|
National Scientific / C4011-25 |
Storage rack for 100 vials, polystyrene, with lid |
EACH |
|
Agilent / 5182-0716 |
Screw-Thread Vials, Large Opening, 2 mL Amber with Write-On Spot |
100/PK |
|
Agilent / 5182-0716 |
Screw-Thread Vials, Large Opening, 2 mL |
100/PK |
|
Agilent / 5182-0724 |
Green Screw Cap, PTFE/Silicone/PTFE |
100/PK |
|
Agilent / 5181-1270 |
Micro-volume Inserts, Borosilicate Glass, Conical with Polymer Support Feet |
100/PK |
|
Agilent / 5181-3377 |
Micro-volume Inserts, Borosilicate Glass, Flat Bottom |
500/PK |
|
Microliter / 09-1400 |
Conical Bottom Vials, Clear, 1.8 mL |
100/PK |
References
[1] Jardine, T.D. & Cunjak, R.A.. 2005. Analytical error in stable isotope ecology. Oecologia. 144: 528. doi: 10.1007/s00442-005-0013-8