US 6,346,419 B1 · Photolysis system for fast-response NO2 measurements and method therefor

Abstract

An efficient, lightweight, and relatively inexpensive photolysis system based on a short-arc Hg arc lamp provides a simple and accurate method for measurement of ambient NO2. High time resolution is achieved by minimizing inlet and photolysis cell residence times and matching NO and NO2 sample paths, and data reduction is greatly simplified relative to conventional photolysis designs. The single-channel embodiment includes (a) a UV light source for emitting light capable of photolytically dissociating NO2 in the gas sample to NO; (b) a device for positioning the light source; (c) an ellipsoidal reflector for collecting and focusing the light from the light source; (d) an enclosure for enclosing the light source and the ellipsoidal reflector; (e) an optical filter assembly for receiving, filtering, and transmitting the focused light; (f) a shutter capable of blocking the transmission of the filtered light which is transmitted through the optical filter assembly; (g) a sample photolysis cell for containing a volume of the gas sample; (h) a device for controllably introducing the gas sample to the sample photolysis cell, and a device for controllably delivering the gas sample from the sample photolysis cell; (i) a detector capable of detecting an amount of the NO present in the gas sample delivered from the sample photolysis cell, and capable of emitting a signal representative of the amount of NO; and (j) a device for measuring the signal so as to quantify the amount of NO. The system is characterized by i) higher conversion efficiency at faster time response; ii) lower power consumption; iii) less heat output with consequently less sample heating; iv) optically filtered light output for NO2-specific conversion, and v) simplified data reduction. The system can be used for measurement of gas-phase NO2 at concentrations ranging from parts per trillion to parts per million or higher. Present applications of the system include ambient atmospheric air measurements, while future medical applications might include the non-invasive monitoring of human breath for NO2.

Claims27

Dependent claims

A single-channel photolysis system for measuring a quantity of NO2 in a gas sample, said system comprising:

(a) a UV light source for emitting light capable of photolytically dissociating NO2 in said gas sample to NO;
(b) a means for positioning said light source;
(c) a reflector for collecting and focusing said light from the light source;
(d) an enclosure for enclosing said light source and said reflector;
(e) an optical filter assembly for receiving, filtering, and transmitting said focused light from the reflector;
(f) a shutter capable of blocking the transmission of said filtered light which is transmitted through the optical filter assembly;
(g) a sample photolysis cell for containing a volume of said gas sample;
(h) a means for controllably introducing said gas sample to said sample photolysis cell, and a means for controllably delivering said gas sample from said sample photolysis cell;
(i) a detector capable of detecting an amount of said NO present in said gas sample delivered from the sample photolysis cell, and capable of emitting a signal representative of said amount of NO;
and
(j) a means for measuring said signal so as to quantify said amount of NO.

8 more elements

A dual-channel system for measuring a quantity of NO2, said system comprising;

a gas inlet line for receiving a total gas sample;
a flow divider for dividing said total gas sample into a first gas sample having a first gas sample volume, and a second gas sample having a second gas sample volume, said first gas sample volume and said second gas sample volume being equal;
a first channel for detecting ambient NO in said first gas sample;
and
a second channel for detecting both ambient NO, and NO resulting from the photolytic dissociation of NO2 to NO, in said second gas sample,
said first channel comprising:
(a) an opaque sample cell;
(b) a first channel means for controllably introducing said first gas sample to said opaque sample cell, and a first channel means for controllably delivering said first gas sample from said opaque sample cell;
(c) a first channel detector capable of detecting an amount of said NO present in the first gas sample delivered from the opaque sample cell, and capable of emitting a signal representative of said amount of NO in the first gas sample;
and
(d) a first channel means for measuring said signal so as to quantify said amount of NO in the first gas sample, and
said second channel comprising:
(e) a UV light source for emitting light capable of photolytically dissociating NO2 in said second gas sample to NO;
(f) a means for positioning said light source;
(g) a reflector for collecting and focusing said light from the light source;
(h) an enclosure for enclosing said light source and said reflector;
(i) an optical filter assembly for receiving, filtering, and transmitting said focused light from the reflector;
(j) a shutter capable of blocking the transmission of said filtered light which is transmitted through the optical filter assembly;
(k) a sample photolysis cell for containing a volume of said second gas sample;
(l) a second channel means for controllably introducing said second gas sample to said sample photolysis cell, and a second channel means for controllably delivering said second gas sample from said sample photolysis cell;
(m) a second channel detector capable of detecting an amount of said NO present in said second gas sample delivered from the sample photolysis cell, and capable of emitting a signal representative of said amount of NO in the second gas sample;
and
(n) a second channel means for measuring said signal so as to quantify said amount of NO in the second gas sample,
wherein said first channel means for controllably introducing the gas sample, said opaque sample cell, said first channel means for controllably delivering the gas sample, and said first channel detector capable of detecting an amount of NO define a first channel gas flow volume, and
said second channel means for controllably introducing the gas sample, said sample photolysis cell, said second channel means for controllably delivering the gas sample, and said second channel detector capable of detecting an amount of NO define a second channel gas flow volume,
said first channel gas flow volume and said second channel gas flow volume being minimal and equal.

23 more elements

A method of measuring a quantity of NO2 in a gas sample with a single-channel photolysis system, said system comprising (i) a UV light source for emitting light capable of photolytically dissociating NO2 in said gas sample to NO;

(ii) a means for positioning said light source;
(iii) an ellipsoidal reflector for collecting and focusing said light from the light source;
(iv) an enclosure for enclosing said light source and said ellipsoidal reflector;
(v) an optical filter assembly for receiving, filtering, and transmitting said focused light from the ellipsoidal reflector;
(vi) a shutter capable of blocking the transmission of said filtered light which is transmitted through the optical filter assembly;
(vii) a sample photolysis cell for containing a volume of said gas sample;
(viii) a means for controllably introducing said gas sample to said sample photolysis cell, and a means for controllably delivering said gas sample from said sample photolysis cell;
(ix) a detector capable of detecting an amount of said NO present in said gas sample delivered from the sample photolysis cell, and capable of emitting a signal representative of said amount of NO;
and (x) a means for measuring said signal so as to quantify said amount of NO,
said method comprising the steps of:
(a) introducing a first portion of said gas sample to said sample photolysis cell;
(b) irradiating said first portion of the gas sample with said light capable of photolytically dissociating NO2;
(c) delivering said first portion of the gas sample from said sample photolysis cell to said detector so as to detect said amount of NO present in the first portion of the gas sample, and so as to emit said signal representative of said first portion amount of NO;
(d) measuring said signal so as to quantify said first portion amount of NO;
(e) positioning said shutter so as to block the transmission of said filtered light to said sample photolysis cell;
(f) introducing a second portion of said gas sample to said sample photolysis cell;
(g) delivering said second portion of the gas sample from said sample photolysis cell to said detector so as to detect said amount of NO present in the second portion of the gas sample, and so as to emit said signal representative of said second portion amount of NO;
(h) measuring said signal so as to quantify said second portion amount of NO;
and
(i) positioning said shutter so as to allow the transmission of said filtered light to said sample photolysis cell.

17 more elements

A method of measuring a quantity of NO2 with a dual-channel system, said system comprising a gas inlet line for receiving a total gas sample;

a flow divider for dividing said total gas sample into a first gas sample having a first gas sample volume, and a second gas sample having a second gas sample volume, said first gas sample volume and said second gas sample volume being equal;
a first channel for detecting ambient NO in said first gas sample;
and a second channel for detecting both ambient NO, and NO resulting from the photolytic dissociation of NO2 to NO, in said second gas sample,
said first channel comprising (i) an opaque sample cell;
(ii) a first channel means for controllably introducing said first gas sample to said opaque sample cell, and a first channel means for controllably delivering said first gas sample from said opaque sample cell;
(iii) a first channel detector capable of detecting an amount of said NO present in the first gas sample delivered from the opaque sample cell, and capable of emitting a signal representative of said amount of NO in the first gas sample;
and (iv) a first channel means for measuring said signal so as to quantify said amount of NO in the first gas sample, and
said second channel comprising (v) a UV light source for emitting light capable of photolytically dissociating NO2 in said second gas sample to NO;
(vi) a means for positioning said light source;
(vii) an ellipsoidal reflector for collecting and focusing said light from the light source;
(viii) an enclosure for enclosing said light source and said ellipsoidal reflector;
(ix) an optical filter assembly for receiving, filtering, and transmitting said focused light from the ellipsoidal reflector;
(x) a shutter capable of blocking the transmission of said filtered light which is transmitted through the optical filter assembly;
(xi) a sample photolysis cell for containing a volume of said second gas sample;
(xii) a second channel means for controllably introducing said second gas sample to said sample photolysis cell, and a second channel means for controllably delivering said second gas sample from said sample photolysis cell;
(xiii) a second channel detector capable of detecting an amount of said NO present in said second gas sample delivered from the sample photolysis cell, and capable of emitting a signal representative of said amount of NO in the second gas sample;
and (xiv) a second channel means for measuring said signal so as to quantify said amount of NO in the second gas sample,
wherein said first channel means for controllably introducing the gas sample, said opaque sample cell, said first channel means for controllably delivering the gas sample, and said first channel detector capable of detecting an amount of NO define a first channel gas flow volume, and
said second channel means for controllably introducing the gas sample, said sample photolysis cell, said second channel means for controllably delivering the gas sample, and said second channel detector capable of detecting an amount of NO define a second channel gas flow volume,
said first channel gas flow volume and said second channel gas flow volume being minimal and equal,
said method comprising the steps of:
in said first channel, (a) introducing said first gas sample to said opaque sample cell;
(b) delivering said first gas sample from said opaque sample cell to said first channel detector so as to detect said amount of NO present in the first gas sample, and so as to emit said signal representative of said amount of NO in the first gas sample;
and
(c) measuring said signal so as to quantify said amount of NO in the first gas sample;
and
in said second channel,
(d) introducing a first portion of said second gas sample to said sample photolysis cell;
(e) irradiating said first portion of the second gas sample with said light capable of photolytically dissociating NO2;
(f) delivering said first portion of the second gas sample from said sample photolysis cell to said second channel detector so as to detect said amount of NO present in the first portion of the second gas sample, and so as to emit said signal representative of said first portion amount of NO;
(g) measuring said signal so as to quantify said first portion amount of NO;
(h) positioning said shutter so as to block the transmission of said filtered light to said sample photolysis cell;
(i) introducing a second portion of said second gas sample to said sample photolysis cell;
(j) delivering said second portion of the second gas sample from said sample photolysis cell to said second channel detector so as to detect said amount of NO present in the second portion of the second gas sample, and so as to emit said signal representative of said second portion amount of NO;
(k) measuring said signal so as to quantify said second portion amount of NO;
and
(l) positioning said shutter so as to allow the transmission of said filtered light to said sample photolysis cell,
wherein said steps (a) through (c) are performed simultaneous with said steps (d) through (l).

35 more elements

Dependencies are inferred from the claim text.

Photolysis system for fast-response NO2 measurements and method therefor

Life of this patent

Photolysis system for fast-response NO2 measurements and method therefor

Life of this patent

Abstract

Claims27