Analysis of ppb Levels of Nitrous Oxide by Gas   Chromatography   Ch       t     h                 Pittcon Paper # 460-7  ...
INTRODUCTIONNitrous oxide (N2O) is produced in the soil by the decompositionof nitrogen compounds. This results in an aver...
FUV DetectorConsists of a uv lamp (120 nm), a 1 cmpathlength cell (50 uL) and a UVphotodiode that measures lamp intensityA...
Chromatogram of HC with FUV Detector
Far UVDetector
Photo of Model 301-B               301-
Equipment usedPA Model 301-B GC           301 BModified by adding a 6 port manual valvewith sample loops from 0 1 to 50 cc...
Actual vs Measured N2O by GC-FUV (ppm)                            120                       on                            ...
Concentrator for N2O
Concentrator ParametersMaterial : molecular sieve- 80/100 meshDesorb volume 10-50 cc        volume- 10 50Desorb temperatur...
Chromatogram of 50 ppmN2O with FUV Detector 10 M x 0.53 mm PLOT Molesieve, 15 cc/min. 80C; 50 ppm N2O in ambient air    bi...
N2O 10 foldconcentration
100 ppb N2O  25 foldconcentration
Calibration Curvefor Concentrator                                   ppb Levels of N2O                    140              ...
SUMMARYBy coupling a FUV detector to a PLOT column, we  y     p ghave been able to detect from 500 ppm down to 250ppb of N...
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Analysis of ppb_levels_of__nitrous_oxide_by_gas_chromatography

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A PID Analyzers portable GC Model 312 was used to detect ppb levels of N2O in the atmosphere.

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Analysis of ppb_levels_of__nitrous_oxide_by_gas_chromatography

  1. 1. Analysis of ppb Levels of Nitrous Oxide by Gas Chromatography Ch t h Pittcon Paper # 460-7 p 460- Dr. John N. Driscoll PID Analyzers, LLC Sandwich, MA www.hnu.com www hnu com
  2. 2. INTRODUCTIONNitrous oxide (N2O) is produced in the soil by the decompositionof nitrogen compounds. This results in an average atmosphericconcentration of approximately 0.25 ppm. It is also used indental offices and in hospital operating rooms during surgery surgery.Methods used for determination of N2O include infrared (IR)spectroscopy and gas chromatography. The former method is chromatography.useful to just below 1 ppm although photoacoustic IR has adetection limit of 30 ppb. The GC detectors used for N2O ppb.include the thermal conductivity detector (TCD) for high levels (>100 ppm) and the electron capture detector (ECD) (100 ppm toapp. 0.1 ppm).app. ppm).)We will be evaluating a Far UV absorbance detector coupled toa concentrator to detect low ppb levels of N2O
  3. 3. FUV DetectorConsists of a uv lamp (120 nm), a 1 cmpathlength cell (50 uL) and a UVphotodiode that measures lamp intensityAs a sample enters the cell, the signal willdecrease in proportion to the absorptioncoefficient of the speciesResponse- organic HC, fixed gases &inorganic gases as shown in next slide
  4. 4. Chromatogram of HC with FUV Detector
  5. 5. Far UVDetector
  6. 6. Photo of Model 301-B 301-
  7. 7. Equipment usedPA Model 301-B GC 301 BModified by adding a 6 port manual valvewith sample loops from 0 1 to 50 cc 0.1Low ppm concentrations prepared bydilution fdil ti of gas standard (1000 ppm N2O) i t d d inzero air10 M x 0.53mm PLOT MolesieveFar UV detector (50 uL dead volume)
  8. 8. Actual vs Measured N2O by GC-FUV (ppm) 120 on y = 1 0162x - 0 5833 1.0162x 0.5833Measure N2O concentratio 100 2 R = 0.9987 80 60 ed 40 20 0 0 20 40 60 80 100 120 Actual N2O concentration Detection limit- 500 ppb
  9. 9. Concentrator for N2O
  10. 10. Concentrator ParametersMaterial : molecular sieve- 80/100 meshDesorb volume 10-50 cc volume- 10 50Desorb temperature: 150°CTimeTi to max.T – 4 seconds T dCan vary Tmax from 1 second to 4 min.Cycled between runs to clean columnAll parameters are under PC control
  11. 11. Chromatogram of 50 ppmN2O with FUV Detector 10 M x 0.53 mm PLOT Molesieve, 15 cc/min. 80C; 50 ppm N2O in ambient air bi t i
  12. 12. N2O 10 foldconcentration
  13. 13. 100 ppb N2O 25 foldconcentration
  14. 14. Calibration Curvefor Concentrator ppb Levels of N2O 140 120 y = 1.0257x - 0.4667 ppb Measured 100 R2 = 0.9913 80 60 M 40 20 0 0 20 40 60 80 100 120 140 ppb Actual
  15. 15. SUMMARYBy coupling a FUV detector to a PLOT column, we y p ghave been able to detect from 500 ppm down to 250ppb of N2O.This covers approximately the same range as theECDWe have evaluated a concentrator/ thermal desorber That improves th d t ti of N2O t 5 ppb. Th t i the detection f to bThe FUV (without a concentrator) is will provide arange that would be adequate for workplace gmonitoring of N2O.The FUV with a concentrator is ideal for monitoringN2O in ambient air

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