18 o & d/h analysis of solids by tc/ea-irms. collect your samples
TRANSCRIPT
18O & D/H Analysis of Solids by TC/EA-IRMS
Collect your samples
Sample Preparation
Material needs to be dry and homogenous
Organisms can be analyzed wholeif small enough
Separate samples are required for hydrogen and oxygen
Sample Weights
Sample should contain:400 µg oxygen
80 µg hydrogen
Encapsulating SamplesWeigh samples into
silver capsules
A crimper plate helps shape capsules
The Good
The Bad
The Ugly
Organizing Trays
Load samples across rows of 96-wells trays
Do not leave empty wells between samples
Label trays uniquely and clearly
Place samples for different analyses in different trays
Sealing trays
For small samples, place an index card or parafilm between tray and lid before sealing
Tape lid securely to tray – use lab tape
International Shipments
Use a shipping company that brokers their own packages (such as Fedex or DHL)
Customs documentsSpecify plant genus and species
Specify for “chemical analysis”
Permits are required for bird feathers
Email [email protected] the appropriate permit
Paperwork
Complete an Analysis Order Form for each analysis type
Complete a sample list for each Analysis Order From
Email forms to [email protected]
Include printed copies with samples
IRMS Basics
(1) Ionize gas
(2) Focus ion beam
(3) Deflect ions
(4) Detect masses
Pyrolysis (High Temperature)TC/EA-IRMSHD & 18O in solids
H2
CO
Gas separation in GC column
CombustionReactor (1400°C)
GCColumn
H2OTrap
Flow toIRMS
HeFlow
Auto sampler
Chromatography
Standards - Hydrogen
International standard (IAEA-CH-7) and inter-laboratory keratin standards are included in all runs
In-house standards have been calibrated against same standards
All results are expressed with respect to VSMOW
Standards - Oxygen
International standards (IAEA-601, IAEA-602, USGS-8568) are included in all runs
In-house standards have been calibrated against same standards
All results are expressed with respect to VSMOW
Raw Data
Reviewed in reprocessorPoor chromatography
Evaluate reference gas values
Confirm placement of standards
Hydrogen Corrections
All corrections are performed on raw ratios
Memory, if needed
Drift over time
H3+ / Size correction
Scale expansion
Oxygen Corrections
Memory
Drift
Size
Scale expansion
Exchangeable hydrogen
Carboxyl and hydroxyl groups will exchange hydrogen atoms with water vapor
Results in shift of deuterium value
Exchangeable Hydrogen - Keratin
Accepted keratin standards allow measurement of keratin samples by “like treatment”
Standards and samples equilibrate with lab atmosphere and are analyzed together
Exchangeable Hydrogen - Keratin
Correcting to known values of keratin standards determines value of non-exchangeable hydrogen of keratin samples
Only works for keratin
Exchangeable Hydrogen
For non-keratin samples, percent of exchangeable hydrogen must be calculated
Dual-Equilibration
By equilibrating a material with waters of different deuterium values, the percent of exchangeable hydrogen and deuterium value for the non-exchangeable fraction can be determined
Oxygen – Memory effect
Oxygen is prone to carryover from one sample to the next
Varies with age of reactor and ash accumulation
Can be corrected for by mass balance
Best precaution – run replicates