Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
  • G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
  • G01N21/64—Fluorescence; Phosphorescence
  • G01N21/6428—Measuring fluorescence of fluorescent products of reactions or of fluorochrome labelled reactive substances, e.g. measuring quenching effects, using measuring "optrodes"
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N31/00—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods
  • G01N31/22—Investigating or analysing non-biological materials by the use of the chemical methods specified in the subgroup; Apparatus specially adapted for such methods using chemical indicators
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
  • G01N33/18—Water
  • G01N33/1826—Organic contamination in water
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/75—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated
  • G01N21/77—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator
  • G01N2021/7769—Measurement method of reaction-produced change in sensor
  • G01N2021/7786—Fluorescence

Definitions

• the invention relates generally to the chemical detection of halogenated hydrocarbons using the Fujiwara reaction and more particularly to the selective detection of certain organic chlorides.
• Trichloroethylene heads theU.S. Environmental Protection Agency's (EPA) list of hazardous (toxic, carcinogenic, etc.) compounds and the organic chlorides, as a group, dominate the ten (10) most frequently found dangerous compounds.
• the other organic chlorides include 1,1,1- trichloroethane (TCA) , 1,1,2,2-tetrachloroethane, chloroform (CC£ 3 ) , carbon tetrachloride (CC£ 4 ) , and 1,2-dichloroethylene (DCE) .
• the Fujiwara reaction is a known methodology widely used for the fluorometric and colorimetric analysis of gem- polyhalogen compounds.
• a strong alkali such as sodium or potassium hydroxide
• pyridine or a derivative thereof reacts with a halogenated hydrocarbon to produce a red colored fluorescent product.
• the traditional chemistry pyridine/base
• pyridine is insoluble in water with the commonly used alkalis (NaOH or KOH) . Therefore, the reaction product is formed only at the interface.
• the Fujiwara chemistry has been modified to overcome the limitations of the two-phase system.
• a single-phase system utilizes pyridine or a derivative thereof with a hindered nitrogen base (phase transfer catalyst) .
• U.S. Patents 4,666,672 issued May 19, 1987 and
• Anderson (deceased), et al. shows method and apparatus for detecting gem-polyhalogenated hydrocarbons using a single- phase Fujiwara reaction.
• the modified Fujiwara chemistry is pyridine or its derivative with a hindered nitrogen base, e.g. tetra(methyl, butyl or propyl) a ⁇ mionium hydroxide. Fluorescence and/or absorbance measurements relate to hydrocarbon concentration.
• EPA Report EPA/600/X-87/467 Part VI (Dec. 1987) describes the Fujiwara reaction for detection of organic chlorides. TCE and chloroform are detected using 2- (aminomethyl)pyridine. As suggested at p.
• TCE is selectively monitored in the presence of chloroform by selectively separating the intermediate product chloroform- derived dichlorocarbene. Fluorescence is measured when the reaction mixture is irradiated at 350 nm (UV) . To shift this excitation wavelength to a lower energy, auxochromes are attached to the pyridine (p. 11) . Lockheed Fiber Optic Chemical Sensor Project - Final
• LLNL Phase II Final Report to DOE (Sept. 1989) describes optrodes for TCE and chloroform, including fluorescence and absorption-based sensors.
• a dual wavelength absorption optrode measures absorption at 530 nm by the colored reaction product, with an internal reference provided by measuring unattenuated light at 610 nm.
• the optrode reagents are different for chloroform: 87.5 v. % pyridine, 12.5% tetrabutylammonium hydroxide (TBAH) (40% aqueous solution), and for TCE: 99 v. % pyridine, 1% TBAH solution.
• the absorption spectra for TCE and chloroform are different.
• the fluorescence sensor has been supplanted by the absorption sensor.
• a method of selectively detecting and identifying a particular organic chloride species in a sample comprising: reacting the sample with a Fujiwara chemistry to form a reaction product, the Fujiwara chemistry being selected to enhance color and specificity of the reaction product of the particular organic chloride species; measuring at least one of an absorbance peak of the reaction product at a preselected first wavelength and fluorescence peak of the reaction product when excited at a preselected second wavelength; comparing the measured absorbance and fluorescence peaks of the reaction product to predetermined values of absorbance and fluorescence peaks at the preselected wavelengths for the reaction product of the selected Fujiwara chemistry and the particular organic chloride species.
• the invention may provide a method of selecting between each of various organic chlorides using a modified Fujiwara reaction.
• the method may spectrally sort the reactions of various organic chlorides with a modified Fujiwara chemistry.
• a method of the invention can preferably distinguish between TCE, chloroform, TCA, carbon tetrachloride, tetrachloroethane and dichloroethylene using a modified Fujiwara reaction.
• the method may select a suitable composition for a modified Fujiwara chemistry and spectrally sorts the reaction products of the selected chemistry with TCE, chloroform, TCA, carbon tetrachloride, tetrachloroethane and dichloroethylene.
• the invention is preferably a method for detecting and identifying each of various organic chlorides using a modified Fujiwara reaction which selectively identifies each particular organic chloride.
• the composition of the Fujiwara chemistry has a significant effect on the characteristics of the colored reaction product with respect to wavelength and absorption.
• a chromophoric-enhancing and species-selective, modified Fujiwara chemistry may be obtained by varying the pyridine, base and water composition and ratios to optimize the results for a particular organic chloride.
• absorption and fluorescence measurements further identify a particular organic chloride by comparing to reference values which have been measured for known samples.
• the invention is a method of selectively measuring the presence of each of a group of gem-polyhalogenated hydrocarbons in a sample using a modified Fujiwara chemistry which has been formulated to enhance the color of the Fujiwara reaction products obtained for the particular hydrocarbon.
• the method is further carried out by measuring the absorption and fluorescence peaks of the sample reaction products and comparing the measured values to a previously determined set of reference values.
• the reference values of absorption and fluorescence peaks for each species of hydrocarbon in the group are determined by reacting a known sample of the species with a modified Fujiwara chemistry with the selected formulation for that particular hydrocarbon. The same selected chemistry is used to test the unknown sample.
• the absorbance and fluorescence reference values of the hydrocarbon species can be compiled into a lookup table, as a function of the chemistry composition for comparison with the measured data. Similar measurements can be performed using different Fujiwara chemistries for each hydrocarbon so that the presence of each hydrocarbon can be tested.
• the invention is described with respect to the following group of gem-polyhalogenated hydrocarbons: trichloroethylene (TCE) , chloroform, carbon tetrachloride, 1,1,1-trichloroethane (TCA) ,1,1,2,2-tetrachloroethane, and 1,2-dichloroethylene.
• the principles of the invention can be carried out to add other species to the group, or for a group of different species, by modifying the Fujiwara chemistry composition to respond to each of the species and by establishing a baseline of colorimetric, absorption and fluorescence data for known samples of each species, and comparing measured values for an unknown sample against the baseline.
• a color and sensitivity enhancing modified Fujiwara chemistry is selected for each species.
• the composition can be varied in terms of using pyridine or a derivative thereof, choosing 5 the phase transfer catalyst (base) , and choosing the ratio thereof. By the proper choice, the development of color and sensitivity are significantly enhanced.
• Pyridine is preferred; 2,2 bipyridine or other pyridine derivatives can also be used.
• the phase transfer catalyst is preferably a
• quaternary ammoniumhydroxide selected fromtetrabutylammonium hydroxide (TBAH) , tetramethylammonium hydroxide (TMAH) , tetraethyla monium hydroxide (TEAH) , and tetrapropylammonium hydroxide (TPAH) , with TBAH most preferred.
• the catalyst is preferably in an aqueous solution, with 30 to 14 wt. % water.
• the ratio of pyridine to catalyst solution is preferably as low as 60 v. % pyridine to 40 v. % catalyst solution and more preferably 80 v. % pyridine to 20 v. % catalyst solution and most preferably 90 v. % pyridine to 10 v. % catalyst solution.
• Light emitting diodes with narrow spectral emission are available at 480 and 555 nm wavelengths. These wavelengths can be used for absorbance and fluorescence measurements, respectively, although other wavelengths could
• the selected Fujiwara chemistry is reacted with a known sample of the particular organic chloride for which the chemistry has been selected and the fluorescence and absorption peaks of the reaction products are measured to establish a reference baseline.
• the reference values may be
• the selected Fujiwara chemistry is then used to analyze unknown samples for the presence of the particular organic chloride.
• the fluorescence and absorption data for the unknown sample is compared with
• 35 series of measurements with different Fujiwara chemistries for the different species can be used to selectively identify all the species present in the sample.
• Table I shows reference absorbance data and reference fluorescence data for each organic chloride for a selected chemistry (80 v. % pyridine) . Absorption is measured using a 480 nm source and fluorescence at an excitation wavelength of 555 nm. The observed color of the reaction products of each of the preferred group of organic chlorides with a number of Fujiwara chemistries can be used to select the appropriate reaction chemistry. Table II shows the absorption band, i.e., the wavelength range absorbed, for each observed color.
• one chemistry 65 % pyridine / 35 % TMAH
• the organic chlorides of interest produce a yellow-brown color or no color
• a second chemistry 80 % pyridine / 20 % TMAH
• TCE chloroform
• tetrachloroethane To produce a color response for carbon tetrachloride a pyridine/TPAH (65%/35%) chemistry should be used.
• a pyridine/TPAH 65%/35%) chemistry should be used.
• the selected chemistry can then be used to analyze samples, with absorption and/or fluorescence measurements being made to identify each species.

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Cited By (4)

Citations (3)

• 1992
  • 1992-08-12 WO PCT/US1992/006791 patent/WO1993004368A1/en active Application Filing
  • 1992-08-12 TW TW081106379A patent/TW207567B/zh active

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