Optical analytical device, waveguide and method

A device for detecting a first material comprising (a) a waveguide having on a peripheral surface of the waveguide a second material which on contacting the first material selectively combines with the first material to measurably change the light transmitting capabilities of the waveguide, (b) a light source positioned to transmit light into the waveguide, and (c) means for measuring the light exiting from the waveguide. The waveguide described in the previous sentence is a new article of manufacture. The device is useful in a method for detecting a first material comprising the steps of (a) exposing a waveguide having on a peripheral surface of the waveguide a second material to an unknown material which may contain the first material, and second material upon being contacted by the first material selectively combines with the first material to measurably change the light transmitting capabilities of the waveguide; (b) transmitting light through the waveguide after exposure in step (a); and, (c) detecting the light transmitted in step (b) as a measure of the first material. The device and method can be used in either qualitative or quantitative analysis.

A related application is Ser. No. 689,403, filed May 24, 1976, for 
Waveguide Holder-Humidifier. 
Another related application is Ser. No. 705,962, filed July 16, 1976. 
BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to an optical analytical method and device and to a 
waveguide or optical fiber useful in the device. 
2. Description of the Prior Art 
U.S. Pat. No. 2,964,993 describes an apparatus for measuring fluids by 
analyzing the specific gravity or composition comprising a longitudinally 
extending radiant energy guide which is of a transparent radiant energy 
transmitting material such as sapphire, quartz or Pyrex. 
U.S. Pat. No. 2,977,842 describes an apparatus and method for measuring the 
quantity of moisture in a moving sheet such as paper using fiber optics. 
U.S. Pat. No. 3,071,038 describes a radiant energy measuring apparatus 
having a radiant energy transmitting light guide for obtaining a 
continuous accurate measurement of changes taking place in density and/or 
specific gravity of composition of a fluid that is flowing over the 
peripheral surface of this guide. 
U.S. Pat. No. 3,370,502 describes an absorption cell means having a rod 
with a cell surrounding the rod, radiant energy being directed at one end 
of the rod means and passing down the rod with multiple internal 
reflection. 
U.S. Pat. No. 3,409,404 teaches the optical properties of a cholesteric 
liquid crystalline material are changed when the cholesteric material is 
contacted with another material. A variety of materials, particularly 
vapors, are identified by observing their effect on cholesteric liquid 
crystalline materials. The most convenient observable effect is a change 
in the color of the cholesteric material and, if necessary, comparing the 
change effected by a known standard material. An anayltical device may 
comprise one or more distinct elements of cholesteric liquid crystalline 
material. Suitable cholesteric liquid crystalline materials include a wide 
variety of compounds, and mixtures thereof, derived from the cholesterol. 
U.S. Pat. No. 3,752,584 describes a spectroscopic device and method of 
using attenuated total reflection techniques for analysis of samples of 
particulate solids in a fluid. A beam of radiation is passed through an 
optical cell comprising a plurality of elongated, totally internally 
reflecting elements, e.g., fiber optics arranged as a mechanical filter. 
When fluid containing the particles is passed transversely across the 
cell, the latter are trapped in the filter whereupon radiation passing 
through the elements is selectively absorbed, thus providing an optical 
output having an absorption spectrum which may be utilized to identify the 
sample. 
U.S. Pat. No. 3,805,066 describes a smoke detecting device utilizing 
optical fibers with smoke paths in a series arrangement interrupting the 
light path. 
SUMMARY OF THE INVENTION 
A device for detecting a first material comprising (a) a waveguide having 
on a peripheral surface of the waveguide a second material which on 
contacting the first material selectively combines with the first material 
to measurably change the light transmitting capabilities of the waveguide, 
(b) a light source positioned to transmit light into the waveguide, and 
(c) means for measuring the light exiting from the waveguide. The 
waveguide described in the previous sentence is a new article of 
manufacture. The device is useful in a method of detecting a first 
material comprising the steps of (a) exposing a waveguide having on a 
peripheral surface of the waveguide a second material to an unknown 
material which may contain the first material, the second material upon 
being contacted by the first material selectively combines with the first 
material to measurably change the light transmitting capabilities of the 
waveguide; (b) transmitting light through the waveguide after exposure in 
step (a); and, (c) detecting the light transmitted in step (b) as a 
measure of the first material. The device and method can be used in either 
qualitative or quantitative analysis. 
The waveguide can be coated with, impregnated with or in some instances can 
be made from the second material provided the second material will 
adequately transmit light, and in some instance the second material may 
constitute reactive groups attached to the waveguide. The first material 
can be selectively combined with the second material by adsorption or 
absorption, chemically including biochemically reacting with and/or 
complexing with the second material. The waveguide coating preferably 
conforms to FIGS. 1B, i.e. both where n.sub.o &lt;n.sub.1 and n.sub.o 
.perspectiveto.n.sub.1, providing for multiple internal reflections 
through the second material, e.g. the coating. 
In the case of a coated waveguide, the waveguide might be either solid or 
hollow, e.g. a hollow or solid cylinder, and in the case of a hollow 
cylinder the coating could be on the inner or outer surfaces or both, but 
normally the ends of the solid rods will not be coated rather only the 
longitudinal circumferential (peripherial) area, i.e. not the light inlet 
and exit ends of the waveguide, except in some cases where it may be 
desirable to pass the light through a coating on the ends to absorb 
certain wavelength light. Obviously, in quantitative detection, the amount 
of the second material on the waveguide needs to be in excess of that 
needed to combine with the anticipated maximum amount of the first 
material to be detected, and preferably the second material is in 
substantial excess. 
Waveguides can be made from transparent material such as sapphire, glass, 
Pyrex or other transparent inorganic material; or from transparent 
plastics such as polystyrene, poly-.alpha.-methylstyrene, 
polymethylmethacrylate or other transparent plastic material. The 
waveguides can be of any convenient shape and size but for greatest 
sensitivity will normally be elongated in the direction of the flow of 
light. Cylindrical waveguides, sometimes called optical fibers, will 
normally be used; however, square, rectangular, oval or other 
cross-section fibers or rods can be used. 
The light source can be a commercially available light source being a 
substantially white light source or can be colored or substantially 
monochromatic in the infrared, ultraviolet, yellow, orange, green, blue or 
other color ranges; however, as the discussion of FIG. 4 indicates filters 
can be used to obtain colored light. Monochromatic light in various colors 
can be supplied by light emitting diode (LED's). Laser light, especially 
dye laser light, can also be used, if desired. As is indicated in this 
discussion of FIG. 4, a particular color such as green in that case can be 
the most desirable depending on the color or compensation of the coating 
developed on the waveguide.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The waveguide-coated combination, which acts as a specific 
collector/sensor, can be chosen to provide a coating whose refractive 
index is either higher, the same, or lower than that of the waveguide. 
Usually, it is preferred that the coating be either a water-soluble or 
non-water-soluble polymer with a reactant in it depending upon its 
compatibility with the desired reactants; however, in some instances the 
coating will be only a reactant. The lower refractive index condition is 
that normally employed in optical guide applications and results in the 
mechanism illustrated in FIG. 1A. 
Employing a coating with refractive index higher than or approximately 
equal to that of the waveguide, the mechanisms shown in FIG. 1B would be 
operative. Although either approach can be used, Model 1A would result in 
lower sensitivity, since the evanescent wave interactions occur only in 
the region of the rod-coating interface. In either of the mechanisms of 
Model 1B, essentially all radiation is transmitted through the entire 
coating and in this way allows solid state spectrophotometric measurements 
to be made in situ. 
In order to measure the light transmittance, an instrument or device was 
designed and constructed to provide quantitative analytical measurements. 
This particular device accommodates glass rods 0.9 mm to 1.3 mm in 
diameter and either 10 mm or 20 mm long. A schematic diagram showing the 
basic components is presented in FIG. 2. The components are: 
1. A tungsten filament lamp light source. 
2. A condenser system to produce nearly collimated light. 
3. A filter for wavelength selection. 
4. An annular aperature to block axial light rays. 
5. A condenser to produce a hollow cone of light rays. 
6. Coupling hemispheres and aperatures to couple large angle rays into the 
rod. 
7. A rod mount to accurately position rods with respect to the aperature 
while presenting a minimum of surface contact. 
8. A silicon photodiode detector. 
9. An operational amplifier operating as "current-to-voltage" converter. 
10. A 31/2 digit digital voltmeter for relative transmittance readout. 
A schematic optical diagram is shown in FIG. 3, with rod dimensions 
exaggerated to show basic instrumental operation. The light from the 
tungsten lamp is collimated using both mirror and lens condensers. The 
light then passes through a heat absorbing glass filter and a variable 
color selection filter. A front surface mirror deflects the light 
90.degree. in the vertical direction. An annular aperature blocks axial 
light rays and defines the range of cone angles for light rays propagating 
in the quartz rods. The substage condenser converts the collimated beam 
into a strongly converging hollow cone of light. The hemispherical lens 
and circular aperture couple the light into the rod. 
After multiple reflections within the rod, the light emerges at the upper 
face and is scattered by a diffuser, part of the light going into the 
silicon photodiode detector. The photodiode is operated in photovoltaic 
mode, the operational amplifier acting as a current sink to minimize the 
voltage across the diode. The amplifier output is a low impedance voltage 
proportional to the input current over a range of 10.sup.31 11 ampere to 
10.sup.31 3 ampere. An output voltage suitable for the 200 mV full-scale 
digital panel meter is selected by a decade range switch. 
In use, the amount of light transmitted through the rod after coating but 
before exposure is first recorded with the device. When the coating is 
exposed to a material of analytical interest, the ensuing reaction changes 
the coating, and the transmission of light through the waveguide changes 
in proportion to the concentration of the reactant species. Depending on 
the particular application it may be desirable that the coated waveguides 
be exposed to the material being detected either positioned in the device 
for measuring light transmission or the coated waveguides may be exposed 
separate from the device and then positioned in the device for light 
transmission measurements. The phenomenon is controlled by the well-known 
waveguide theories that have been described by Kapany*. 
FNT *Kapany, N.S., "Fiber Optics, " Academic Press, New York, 1967. 
The composition of a coating that has been applied to a waveguide can be 
changed by the following mechanisms which lead to detection by the device 
through sensing a change in refractive index and/or by absorption, 
adsorption or scattering processes: 
1. Chemical reaction of a component with the active ingredient (reactant) 
in the coating of the waveguide to produce a product which is essentially 
the same color as the starting material. 
The device senses this change due to a change in the refractive index of 
the product material. This approach has the disadvantage that the end 
product is not colored and therefore not wavelength selective. As a 
consequence moisture is sensed and interferes but this may be eliminated 
by drying the coated waveguide to the same degree as when the test was 
initiated. The product can be quite stable depending upon the specific 
reaction chosen. 
The essential factor is that the critical angle beyond which entering the 
light rays are no longer transmitted through the rod is given by sin 
.theta.c = (n.sub.1 /n.sub.o), wherein n.sub.o, the refractive index of 
the core, is greater than n.sub.1, the refractive index of the coating. 
Thus, the coated waveguide acts as a sensitive light amplifier whose 
electrical analog is that of a vacuum tube or transistor-operated 
amplifier in that a small change on the outer surface of the rod controls 
a large change in the light transmitted through the rod. 
2. Chemical reaction of a component with the active reactant in the coated 
waveguide to produce a stable product which is clear and colored. 
This approach offers specificity because of the wavelength selection 
capabilities of the device, and therefore achromatic light can be used to 
compensate for moisture which contributes to the readings. The product can 
be quite stable depending upon the specific reaction chosen. 
3. Chemical reaction of a component with the active reactant in the coated 
waveguide to produce a colored and/or non-colored precipitate. 
In this instance whether or not the precipitate has color would make little 
difference since the light impinging on the particles would be mainly lost 
due to scattering. Moisture would interfere here but could be negated by 
drying to the same extent as when the test was initiated. The product can 
be quite stable depending upon the specific reaction chosen. 
4. Complexation reaction of a component of interest with the active 
reactant in the coated waveguide to produce a colored and/or non-colored 
product. 
In most cases the product will be colored. The product stability will 
generally not be as acceptable as that formed in a chemical reaction but 
will vary depending upon the specific reaction chosen. 
5. An acid-base reaction of an acidic or basic component of interest with a 
pH-sensitive reactant in the coating to produce a colored reaction 
product. 
This reaction is non-specific since any acidic or basic material will 
provide the same colored product. An advantage is that in this instance 
the reaction can be reversible and tailored to change at a desired 
concentration of component by proper selection of the initial pH and 
buffering agents present. 
6. Use of physical processes such as absorption and/or adsorption of a 
component of interest by the reactant incorporated into the coating which 
has selective affinity for the component. 
This approach may not hold the component strongly enough to provide the 
desired product stability. 
We have found that moisture in the coating is necessary for many chemical 
and complexation reactions to occur. This is normally not a problem due to 
the moisture present in the air and the tendency of the coated 
collector/sensors to retain a relatively fixed amount of moisture; 
however, a preferred solution for moisture sensitive reactions is 
described in copending application Ser. No. 689,403, filed May 24, 1976, 
for a Waveguide Holder-Humidifier, and the teachings of the Waveguide 
Holder-Humidifier application are hereby incorporated by reference into 
this application. 
EXAMPLE 1 
This technique was tested by seeing if microgram quantities of sodium 
cyanide (NaCN) could be determined. A 1% aqueous solution of polyvinyl 
alcohol was prepared and 0.1% by weight of sodium picrate was added, which 
is known to respond to (CN.sup.-).* This solution was then used to 
uniformly coat the surface of the rods while the ends were protected. 
FNT *Feigl, Fritz, "Spot Tests in Inorganic Analysis, " Elsevier Publishing 
Company, New York, 1958. 
Light transmission of the dry, coated lightguides was measured before 
reaction. Known amounts of cyanide ion in the form of sodium cyanide were 
applied to the outer surface of the guides using a 5 ml Eppendorf pipette, 
the rods were dried, and transmission was again measured. The percent 
transmission based on the initial reading before exposure was then plotted 
as a function of (CN.sup.-) concentration. 
The results shown in FIG. 4 were obtained. Reaction between the cyanide ion 
and the picrate changed the refractive index of the coating. The resulting 
change in light transmission through the guide was proportional to the 
concentration of the cyanide species. The multiple internal reflections 
enhanced the sensitivity, in that a small change in the optical 
characteristics of the coating caused a large change in the light 
transmitted through the system. It will be noted that the green filter 
provided the best sensitivity, which would be anticipated since green is 
the complementary color of the reddish-brown color of the reaction 
product. It is also noted that Beer's law is obeyed over the expected 
concentration range. 
This technique was also successfully applied to the determination of 
gaseous HCN in air. The cyanide-in-air determination is not felt to be a 
typical of the applications that might be encountered and, therefore, it 
should be possible to apply this technique to a wide variety of components 
or pollutants of interest. 
Initially, we anticipated problems both with the coatings themselves and 
with coating uniformity. While we did encounter problems along these 
lines, we have found that coatings can be applied uniformly once the 
coating procedures have been developed and that a number of different 
coating materials may be useful. In addition to water-soluble polyvinyl 
alcohol, Carbowax was found to perform quite well. Polymers that are not 
water-soluble will also be useful in some instances and sometimes the 
second material reactant without a polymer binder can be used to coat the 
waveguide, although in most instances a polymer binder will be preferred. 
The most serious problem that we encountered, in the case of the 
determination of gaseous HCN, was the interference due to varying amounts 
of moisture in the air contributing to the reading obtained. We found that 
moisture absorption by the coated rods was proportional to the readings 
obtained at each of the wavelengths. However, since the reddish-brown 
reaction product was most sensitive to its complementary color or green, 
the green wavelength could be used to follow the reaction with sodium 
picrate while the moisture interference at this wavelength was corrected 
by using the change in the readings using achromatic light. 
Thus, it is preferable to utilize a selective reaction which results in a 
colored product. The use of a selective reaction in which a 
non-color-selective end product is formed can still be utilized provided 
that the waveguide rods are dried to the same extent after the reaction as 
before. 
EXAMPLE 2 
This example describes the detecting of ammonia. The reaction between 
ammonia and ferric sulfate could take three possible routes: 
##STR1## 
The most desirable reaction is the chemical reaction to form the combined 
salt, ferric ammonium sulfate. Applying the basic thermodynamic 
considerations of 
EQU aA + bB + . . . .revreaction. cC + dD 
EQU .DELTA.g.sup.0 = cG.sub.C.sup.0 + dG.sub.D.sup.0 - aG.sub.A.sup.0 - 
bG.sub.B.sup.0 
EQU .DELTA.g.sup.0 = rtlnK 
where 
.DELTA.G.sup.0 = Gibbs free energy 
K = equilibrium constant 
to equation 3, we obtain as an estimation of K = 5.5 .times. 10.sup.22. 
Thermodynamically this indicates feasibility of the reaction and that the 
product formed should be stable. 
Accordingly, coated waveguides were prepared which incorporated Fe.sub.2 
(SO.sub.4).sub.3 as the active ingredient into the coating. These 
waveguides were then exposed to ammonia, which caused the expected color 
change, i.e. from off-white before exposure to violet after. The measured 
change was about 20% as opposed to waveguide rods which were not exposed 
to ammonium vapors. The colored product proved to be stable overnight, as 
hoped. 
Waveguides were also prepared which incorporated 
ninhydrin(triketohydrindene hydrate) as the active ingredient in the 
coating. On exposure to ammonia, which caused the clear-colorless coating 
to turn blue, a change in transmittance of about 60% was found as opposed 
to waveguide rods which were not exposed to ammonia vapors. Both the 
ferric sulfate and ninhydrin can also be used to detect amines as well as 
ammonia. This is only another example of many different types of reagents 
that can be used to measure a component of interest. Sensitivity can be 
tailored by (1) selection of reagent, (2) the concentration of reagent 
used in the coating, (3) the coating thickness, and (4) the length of the 
waveguide. 
EXAMPLE 3 
A device of the invention was used to indicate the reaction of an antigen 
with an antibody on a quartz rod. The need for a simple test for disease 
and/or immunology detection using antibodies or antigens of all types and 
the broad operability of the present invention to fill this need is 
indicated by this example coupled with a recent article in Science News, 
by Dietrick, E. Thompson, "How a Nobel laureate solid-state physicist 
discovered a way of doing immunology by dunking, " Vol. 105, May 18, 1974, 
pages 324 and 5. 
Polystyrene latex spheres about 1.mu. in diameter were treated with an 
excess of an antigen (human serum albumin) and the excess was then removed 
by repeated washings. Quartz rods silanized with diphenyl dimethoxy silane 
were coated with the corresponding antibody by incubating for 21 hours 
with a solution of anti human albumin at 1.0 mg/ml in 0.05 M bicarbonate 
buffer at pH 9.6, centrifuging and washing excess from the spheres. 
Uncoated portions of the rod surface can be filled by subsequent dipping 
of the rod in bovine serum albumin (BSA). The rods coated with specific 
and nonspecific antibody were exposed to a buffered solution containing 
the specific antigen (human albumin) coated polystyrene spheres. 
The following results were obtained. 
______________________________________ 
Sample Concentration of 
% Change in Axial Transmission 
Antigen Originally 
of Rod Coated With Specific 
Applied to Polystyrene 
Antigen as Opposed to Rod 
Latex Spheres Coated With Nonspecific Antigen 
______________________________________ 
.perspectiveto.1 mg/ml 
-55.7% 
.perspectiveto.1 .mu.g/ml 
-17.6% 
______________________________________ 
EXAMPLE 4 
This example describes the detecting of hydrogen sulfide. Lead acetate 
reacts with H.sub.2 S to produce a black precipitate of lead sulfide which 
scatters light. Using 1% lead acetate in polyvinyl acetate on the 
waveguide the results shown in FIG. 5 were obtained in the laboratory for 
a 6.7 ppm concentration of H.sub.2 S in air. 
The changes in the scattered axial transmission are measured by using an 
appropriate mask at the waveguide exit which masks mainly the direct light 
from the input aperture mask. These changes are due to scattering of the 
hollow cone of light launched into the waveguide because of the effect of 
the polystyrene spheres on the circumferential portion of the waveguides. 
In the device and method of this example, light from a tungsten filament is 
directed via a lens system through a quartz rod to a photodiode detector, 
as in previous discussion on FIG. 3. When a coating is incorporated on the 
surface of the rod, the attenuation of light travelling through the rod 
varies. Thus, a measure of the amount of light transmitted through the 
entire rod and falling on the photodetector is indicative of the physical 
properties (refractive index, suspended solids, color, etc.) of the 
coating. Colored filters can be used to measure color changes in the 
coating. 
There are significant differences in transmittance of different rods since 
each surface imperfection or scattering center has an effect. Therefore, 
each rod must be handled separately, or rods prepared or selected having 
substantially the same transmittance should be used. 
Some illustrations of other materials which can be detected by a device of 
the invention are as follows: 
1. Some experiments were carried out detecting CO.sub.2. A polyvinyl 
alcohol coating containing a sodium carbonate/bicarbonate buffer and a 
methyl red indicator was applied to a waveguide. This coated waveguide was 
exposed to an atmosphere containing CO.sub.2 and the coating changed from 
red to yellow which is measurably detected with the device. This reaction 
illustrative of the acid/base reaction is reversible (not permanent) and 
when the CO.sub.2 atmosphere is removed from the waveguide the color 
changes back to red and thus the utility of the invention has been 
demonstrated both for permanent and reversible chemical reactions. 
2. An illustration of a precipitate being formed is when an SO.sub.3 
containing atmosphere is contacted with a coated waveguide containing 
BaCl.sub.2. Sufficient moisture is normally present in the air to form 
sulfuric acid from the SO.sub.3 and the sulfuric acid reacts with 
BaCl.sub.2 to form a precipitate BaSO.sub.4, which has a coating on the 
waveguide will cause loss of light by scattering and so measurably reduce 
light transmission through the waveguide. 
3. Phosgene can be detected using a rod coated with a reagent such as 
mixtures of p-dimethylaminobenzaldehyde and dimethylaniline or 
alternatively mixtures of p-nitrobenzylpyridine and N-benzylaniline. Other 
reagents useful for phosgene determination are: 
a. Methyl violet 
b. Methyl violet B 
c. Gentian violet 
d Rosaniline 
e. phenylhydrazine cinnamate and 1% copper sulfate 
f. p-dimethylaminobenzaldehyde and an aromatic amine 
g. diethylphthalate containing (4-nitrobenzyl)pyridine 
h. N-ethyl-N-2-hydroxylthylaniline and p-dimethylaminobenzaldehyde 
i. 4-(p-nitro-4,4-bis(dimethylamino)benzophenine 
j. 4,4'-bis(dimethylamino)benzophenone and N-phenyl-1-napthylamine 
Each reacts with phosgene to produce a colored compound. 
4. Tolylene diisocyanate can be detected using a rod coated with a reagent 
such as p-dimethylaminobenzaldehyde mixed with acetic acid, or 
p-dimethylaminobenzaldehyde, sodium nitrite, boric acid and ethyl 
cellosolve mixed together. 
5. Sulfur dioxide can be detected using a rod coated with mixtures of 
p-phenylenediamine and formaldehyde, mixtures of iodine and starch, or 
mixtures of potassium tetrachloromercurate, pararosaniline and 
formaldehyde. Other reagents which can be used for O.sub.2 are: 
a. sodium tetrachloromercurate and pararosaniline 
b. zinc acetate, pyridine, and sodium nitroprusside 
c. zinc nitroprusside 
d. nickel hydroxide 
e. iodine and starch 
f. Meldola Blue 
g. Hydrine Blue R 
Each reacts with sulfide dioxide to form a colored adduct. 
6. Carbon Monoxide -- Reagents useful for the CO determination are: 
a. palladous chloride 
b. alkaline solution of the silver salt of p-sulfaminobenzoic acid 
c. tetrachloropalladate (II), iodate, and leucocrystal violet 
[4,4',4"-methylidynetris (N,N-dimethylaniline)] Each serves as a reagent 
for oxidation of CO, the accompanying reduction of metal ions providing 
the basis for a color change and/or precipitate formation. 
7. Hydrogen Chloride (or Hydrochloric Acid Vapors) 
a. hydrogen ion (pH) indicators such as phenol red, methyl orange, methyl 
red, etc, in a procedure analogous to that for item (1), page 19. 
b. silver nitrate, which would provide both sensitivity and specificity 
through formation of the light scattering precipitate silver chloride. 
8. NO.sub.x -- Reagents useful for the NO.sub.x determination are: 
a. benzidine hydrochloride 
b. 
mixture of aniline and p-toludine 
c. 2,7-diaminofluorene, or 2,7-diaminofluorenehydrochloride 
d. 2,4-diamino-6-hydroxypyrimidine and H.sub.2 SO.sub.4 
e. diethyldiphenyl urea 
f. .beta.-dinaphthylamine and H.sub.2 SO.sub.4 
g. diphenylamine 
Each results in formation of a colored or fluorescing adduct. 
9. Ozone -- Reagents useful for the ozone determination are: 
a. a mixture of .alpha.-naphthylamine and tartaric acid 
b. o-phenylenediamine and HCl 
c. alcoholic solution of benzidine 
d. m-phenylenediamine hydrochloride 
e. p-phenylenediamine 
f. tetramethyl-p-phenylenediamine in acetic acid 
g. buffered potassium iodide 
Each utilizes the reaction with ozone to produce a colored product. 
10. Hydrazine -- Reagents useful for the hydrazine determination are: 
a. p-dimethylaminobenzaldehyde 
b. perinapthindan-2,3,4-trione hydrate Each produces a colored or 
fluorescing product. 
The device, waveguides and method of this invention are especially useful 
in detecting toxic substances and/or atmospheric or water pollutants, for 
which a number of examples are given in this application. Some of the most 
significant atmospheric pollutants are combustion gases which consist 
essentially of CO, CO.sub.2, NO.sub.x, SO.sub.2 and SO.sub.3 in varying 
quantities depending on the materials and amounts thereof involved in 
combustion. Each of these combustion gases is dealt with in one of the 
specific numbered items listed above. A waveguide for each of these 
combustion gases can be included in a single waveguide holder to provide 
for the detection of all of these combustion gases at the same time. 
Similar techniques to the above examples can be adapted to measurement of 
other components such as vinyl chloride, sulfuric acid, acrolein, maleic 
anhydride, formaldehyde, hydrogen fluoride, chlorine, fluorine, acetic 
acid, napthoquinone and phthalic anhydride. 
Furthermore, techniques similar to the above examples can be adapted for 
functional group response of generic classes of compounds such as: 
alcohols, ketones, aldehydes, ethers, esters, halogen compounds, phenols, 
amines, and hydrocarbons. 
In all applications of the device of the invention it is recognized that 
reagents and reaction conditions must be selected in accordance with the 
criteria of mutual compatibility, sensitivity, stability, and proportional 
response. 
Many more illustrations could easily be provided by a person skilled in the 
art from chemistry texts or literature articles, such as, "Spot Tests In 
Inorganic Analysis":, Fritz Fergl, Elsevier Publishing Co., New York, 
(1958); or "Colorimetric Methods of Analysis, " F. D. Snell, C. T. Snell 
and C. A. Snell, D. Van Nostrand Co., Inc., New York, (1959). 
A number of desirable features of the coated waveguide rods are: 
1. They do not require batteries or other power sources since sample pumps, 
etc. are not required. However, it may be desirable to utilize a sample 
pump in conjunction with a coated waveguide for a future application. 
2. They can be quantitatively measured for ammonia or hydrogen cyanide 
exposure or other materials by measuring the transmission when they are 
returned to the laboratory without any additional treatment. 
3. The instrumentation for measurement is simple and inexpensive. 
4. The coated waveguide rods can be sensitized to a variety of different 
compounds. 
5. The classification of approaches made at the present time indicates a 
broad scope of application. 
6. The sensitivity of the waveguide can be increased by increasing its 
length and this may be especially important in detecting minute quantities 
of environmental air pollutants such as ammonia, hydrogen cyanide, etc. 
Although the invention has been described in terms of specified embodiments 
which are set forth in considerable detail, it should be understood that 
this is by way of illustration only and that the invention is not 
necessarily limited thereto, since alternative embodiments and operating 
techniques will become apparent to those skilled in the art in view of the 
disclosure. Accordingly, modifications are contemplated which can be made 
without departing from the spirit of the described invention.