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System for δ13C-CO2 and xCO2 analysis of discrete gas samples by cavity ring-down spectroscopy

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Title System for δ13C-CO2 and xCO2 analysis of discrete gas samples by cavity ring-down spectroscopy
Subtitle Measuring discrete gas samples on an isotopic laser-absorbtion gas analyser
Author Dickinson, Dane
Isotope Bioscience Laboratory
Contributors Bodé, Samuel
Boeckx, Pascal
License CC Attribution 3.0 Germany:
You are free to use, adapt and copy, distribute and transmit the work or content in adapted or unchanged form for any legal purpose as long as the work is attributed to the author in the manner specified by the author or licensor.
DOI 10.5446/32922
Publisher Copernicus Publications
Release Date 2017
Language English
Producer Dickinson, Dane
Production Place Atmospheric Measurement Techniques

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Subject Area Earth Sciences, Physics
Abstract A method was devised for analysing small discrete gas samples (50 ml syringe) by cavity ring-down spectroscopy (CRDS). Measurements were accomplished by inletting 50 ml syringed samples into an isotopic-CO2 CRDS analyser (Picarro G2131-i) between baseline readings of a standard reference air, which produced sharp peaks in the CRDS data feed. A custom software script was developed to manage the measurement process and aggregate sample data in real-time. The method was successfully tested with CO2 mole fractions (xCO2) ranging from <0.1 to >20000 ppm and δ13C-CO2 values from -100 up to +30000 ‰ vs VPDB. Throughput was typically 10 samples h-1, with 13 h-1 possible under ideal conditions. The measurement failure rate in routine use was ca. 1 %. Calibration to correct for memory effects was performed with gravimetric gas standards ranging from 0.05 to 2109 ppm xCO2 and δ13C-CO2 levels varying from -27.3 to +21740 ‰. Repeatability tests demonstrated that method precision for 50 ml samples was ca. 0.05 % in xCO2 and 0.15 ‰ in δ13C-CO2 for CO2 compositions from 300 to 2000 ppm with natural abundance 13C. Long-term method consistency was tested over a 9-month period, with results showing no systematic measurement drift over time. Standardised analysis of discrete gas samples expands the scope of applications for isotopic-CO2 CRDS and enhances its potential for replacing conventional isotope ratio measurement techniques. Our method involves minimal set-up costs and can be readily implemented in Picarro G2131-i and G2201-i analysers or tailored for use with other CRDS instruments and trace gases.

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Transcript
00:02
hello my name is staying Dickinson and I'm at the I stood by science of archery at Ghent University and today I'm going to demonstrate how to measure discrete guess samples on an isotopic laser absorption gas analyzer thank 1st let's have a look at our measurement setup we use in the carriage e 21 31 all I I stop acceded to guess analyzed we're largely aspect for supplying instrument with a stable reference baseline for measurements the gas that is connected to the laws of i one-eighth inch if the p cheating and and dispersing the achieving at to three-way valves were via lock fittings the 1st phallus fulfilling the gas bag of reference here while the 2nd is a sample and the point and finally we using an SGD 50 milliliter gas-tight surrender of fitting and push button thou for straight sample deliberate the principle of operation is as follows we start by taking a 5 to 10 minute measurement of
01:05
reference desk in order to provide a steady baseline against which a syringe samples will be distinguished after that's where I would introduce discrete samples which
01:16
will thus showed as distinctive peaks in the DoDAF aid to standardize this method we
01:22
developed a basic software script which manages the sample input prices the takes a sample Bates extracts and analyzes the sample data and outputs a concise results while I will now demonstrate the method
01:35
info to be we've already started the carrier gas
01:42
analyzer which has been sampling ambient
01:45
labia for the past hour so now starts off with script which runs of them the
01:50
carrot coordinate application programs at the start of sample sequence there is the opportunity to
02:01
adjust various parameters so hero specify a sequence of 3 samples now
02:11
the reference in reading the state after the
02:20
reference measurement is done ready to run syringe samples understand take samples of Latvia the all I needed those connect the syringed Finland point when the system is ready the software will prominent open the valves
02:36
note the position of three-way valve bonnet dereferences supply must be stopped and the
02:41
analyzer then draw directly from the syringe
02:46
the samples then evacuated of the plunger collecting unassisted it is important that the syringes correctly lubricated so as the sample evacuation proceeds smoothly once a sample is finished the three-way valve must be immediately returned to its initial position so
03:03
as to resume reference air intake of minimal disruption is possible the software that
03:09
automatically extracts a sample data once
03:16
analyzer readings have completely returned to the reference composition this time for the next sample when analyze like the G 21
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31 I you can generate expect to complete around 10 samples now now that are 3
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samples have been measured whole upload Sample
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Descriptors there are 3 separate fields
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available for describing each sample and as you can see all measurement data for each sample thus uniquely coded so yeah and the result
04:36
society in CSV format meaning they can be easily imported into any data analysis software for further use thanks for
04:50
watching demonstration this method is described in further detail in article and Atmospheric Measurement Techniques
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