食品 饮料 大气 海洋生物中碳同位素检测方案(其它质谱仪)

PICARRO STABLE CARBON ISOTOPE ANALYSIS OF AIRBORNE PARTICULATE MATTER USING A CARBONAEROSOL ANALYZER AND A CAVITY RING-DOWN SPECTROMETER Z. Lin1*， D. Kim-Hak1， L， Pitzman2， R. Cary2， C.W. Rella1，J. A. Hoffnagle1， R. Winkler1，Y. Zhang3 1Picarro， Inc.， 3105 Patrick Henry Drive， Santa Clara， California *Contact： zlin@picarro.com2Sunset Laboratory Inc.， 10180 SW Nimbus Ave， Tigard， OR 97223， USA SunsetLaboratory Inc. Abstract Particulate matter affects more people than any other ambient air pollutant， leadingto increased risk of cardiovascular and respiratory diseases. Levels of PM10 andPM2.5 in the developing world， especially southeast Asia and the Indiansubcontinent， routinely exceed World Health Organization guidelines， often by afactor of 10 or more. Despite their importance to poor air quality in urban areas inthe developing world， the mechanisms that lead to heavy particulate loading are notwell understood. Consequently， there is great interest in developing new tools forunderstanding the pollution sources and mechanisms that drive the formation ofharmful aerosols. Stable isotope analysis of the carbon contained in the aerosolspromises to provide important information about the sources and processes thatgovern aerosol formation and transport. We have coupled a Sunset Laboratoriesorganic and elemental carbon (OC/EC) analyzer to a cavity ringdown spectrometer(CRDS) to create a system that provides hourly measurements of the d13C contentof PM in the ambient air. The OC/EC system executes a sequence of temperatureand oxygenation steps to create distinct CO2 pulses of organic carbon， carbonatecarbon， and elemental carbon， which are subsequently analyzed by the CRDSinstrument for d13C -Co. We present laboratory measurements with this system，including calibration， precision， and drift， demonstrating that a system of this designcan deliver aerosol stable isotope analysis at sub-permil accuracy and precision.This system can be operated unattended， and is thus suitable for remote fielddeployment. Instrumentations CRDS Technology and Picarro G2131-iAnalyzer Cavity Ring-Down Spectroscopy (CRDS) Technology utilizes the unique infraredabsorption spectrum of gas-phase molecules to quantify the concentration of (andsometimes isotopes of) H2O， CO，CH4，N2O，CH2O，NH3. CRDS Features： · Small 3-mirrored cavity ~ 35 cc Long effective path-length (> 10 km) .Time-based measurement Laser is switched on and off， and scannedacross wavelengths The Picarro G2131-ianalyzer uses the CRDStechnology to measure d13C in CO at <0.1%o.It also simultaneously analyze CO2， CH4，and H20concentrations. G2131-iSpecifications： Precision，6*C in CO，1-a， 1 Hr wiMax Drift at STP 6C in CO： (over 24hrs，eak-to-peak， 1 hr interval average)sion， CO： Concentration (30 sec， 1-o)recision，CH， Concentration (30 sec， 1-a)Precision， H；O Concentration (30 sec， 1-o)CO：Dynamic Range 0.1. guai on at>380 ppm COd<0.25%o。tytypical precision at 200 ppmCO.，0.05% typical precision at >1000 ppmCOc0.5%。200 ppb("C)/10 ppb("C)50 ppb +0.05% of reading ("C)100 ppm380-2000 ppm e，0.01-0.4% ooppeeratior rangeUp to 100% pure CO， samples can be analyzed with the A0314 Small Sample IsotopeModule 2 (SSIM2) peripheral， which includes dilution. Minimum sample volume per replicate with the SSIM2 is 10 pl of pure CO： (0.45 pmoles or 20 pg of CO；) or the equivalent volumeof CO， in air. Sunset Organic Carbon-Elemental Carbon (OC-EC) Aerosol Analyzer In the Lab OC-EC Aerosol Analyzer， samples are thermally desorbed from the filtermedium under an inert argon atmosphere followed by an oxidizing atmosphereusing carefully controlled heating ramps. A non-dispersive infrared sensor (NDIR) isused to monitor the analysis. The low dead volume carrier gas control system andproprietary quartz oven design provide high sensitivity with ultra low carbonbackground and no oxygen contamination. Method To analyze the isotopic composition (d13C) of the effluent CO gas coming from theSunset analyzer， additional considerations need to be made for the CRDS analyzer.1) Carrier Gas The Sunset analyzer accepts helium and argon as two carrier gas options. Theargon has been chosen for the system， as the helium could degrade the pressuregauge used for cavity pressure monitoring due to its small atom size. Although theargon is a carrier gas that will broaden the CO2 peaks differently than the air whichthe analyzer is designed for， the spectral fitter is kept the same. This is because thebroadening effect caused by the argon does not differ much from the one caused bythe air. The effect of the line shapes on the isotopic ratio measurement can beaccounted for by calibrating the analyzer with samples of known isotopiccomposition in a background of argon. 2) Precision Optimization： Tape Recorder Technique · Darker colors represent the measurement conducted with ZA as the carrier gas.· Measurement precision is poorer for the directly measured 'record' phase thanfor the slower replay' measurement， for a couple of reasons： less time is spentmeasuring each pulse in the record phase (by a factor of 5-6)， and the pulsesare smaller. This is the main benefit of the tape recorder-improved precision.· The per-pulse measurement noise on replay is about 0.4 permil for an averagereplay pulse peak height of 350 ppm and duration of about 2-3 minutess. Experiment Setup Gas Storage / On nThe collected aerosols get combustion in Sunset. TheAerosol Combustion generated CO，/Ar flows to the tape recorder. Thesample gas flows to the tape recorder. The net gasflowrate going into the tape recorder is 35 sccm.Isotope Analysis/ Off Off Off The gas collected into the tape recorder is released toAerosol Collection the Picarro analyzer at a lower flow (11 sccm). Thus，the dilation time is 3.2 greater than the pulse. Results Mean Standard DeviationOC 617.9 ppm23.2 ppmOC Isotope -27.8%o 0.2%oboEC 257.4ppm6.7ppmEC Isotope -28.2 0.4%obo· The aerosol sample was collectednear l-5 interstate highway.10ug OC corresponds to a CO，pulse peaking at~600ppm.TThe 12CO， and 13CO， pulses areintegrated separately before thecalculation of the isotope value. The good precision reveals the potential of this method for practical use onin-situ monitoring stations. The fact that the precision gets higher as the. amount of the aerosols increases suggests that more accurate isotopicinformation can be recorded during pollution episodes. Future Work The Picarro analyzer has been sent to Professor Zhang Yanlin’s lab in NanjingUniversity of Information Science & Technology for the integration test with thefield Sunset analyzer to complete the semi-continuous monitoring solution.Prof. Zhang will fine-tune the configuration of the system and deploy thesystem for field study. Interested in learning more? Contact Zhiwei Lin (zlin@picarro.com) . Visit www.picarro.com1. 用于识别和分类食用油的δ13C的自动测量