Apparatus and method for detecting glycol

Abstract

A method and apparatus are provided for detecting contaminants, such as ethylene glycol and diethylene glycol, in various materials, including household products, and medicines. The contaminants can be detected using enzyme assays that produce measurable changes in light absorption and/or light fluorescence.

1 . A method of detecting at least one of ethylene glycol and diethylene glycol in a sample suspected of containing glycol, the method comprising:
 reacting a glycol with NAD+ in the presence of an alcohol dehydrogenase to produce NADH;   oxidizing NADH with an oxidase to produce hydrogen peroxide;   oxidizing a fluorogenic substrate in the presence of the hydrogen peroxide and a peroxidase to convert the fluorogenic substrate to a fluorescent form;   irradiating the sample at a first wavelength;   detecting light emission at a second wavelength; and   
       providing a signal corresponding to the amount of light detected. 
     
     
         2 . The method of  claim 1  wherein reacting a glycol includes generating an aldehyde. 
     
     
         3 . The method of  claim 1  wherein the alcohol dehydrogenase is a yeast alcohol dehydrogenase. 
     
     
         4 . The method of  claim 1  wherein oxidizing a fluorogenic substrate includes converting N-acetyl-3,7-dihydroxyphenoxazine (Amplex Red) or Amplex Ultrared into its fluorescent form. 
     
     
         5 . The method of  claim 1  wherein the glycol is reacted with the NAD+ in an alkaline environment. 
     
     
         6 . The method of  claim 1  wherein the glycol is reacted with the NAD+ at a pH of greater than or equal to 7.5. 
     
     
         7 . The method of  claim 1  wherein the glycol is reacted with the NAD+ at a pH between 7.3 and 9. 
     
     
         8 . The method of  claim 1  wherein the glycol is reacted with the NAD+ in a Tris-HCl buffer having a pH of about 7.8. 
     
     
         9 . The method of  claim 1  wherein the glycol is reacted with the NAD+ in a buffer selected from the group consisting of Tris, bicine, Tris Base HCl, bicine NaOH, alkaline pH “Good's,” and phosphate buffers. 
     
     
         10 . The method of  claim 1  further comprising the step of fitting the signal to V(t)=β exp(t/τ)+V0. 
     
     
         11 . The method of  claim 10  further comprising the step of normalizing a time constant for the sample by a time constant for pure glycol. 
     
     
         12 . A method of detecting ethylene glycol and diethylene glycol in a sample suspected of containing glycol, the method comprising:
 reacting the sample with a coenzyme in the presence of an alcohol dehydrogenase to form a measurement solution;   electroluminescently generating a single wavelength ultraviolet light;   illuminating the measurement solution with the single wavelength ultraviolet light;   detecting ultraviolet light transmitted through the measurement solution; and   producing a signal corresponding to the amount of light detected.   
     
     
         13 . The method of  claim 12  wherein the signal comprises a voltage signal. 
     
     
         14 . The method of  claim 13  comprising normalizing the voltage signal by dividing the voltage signal by a second voltage signal recorded at time equals zero. 
     
     
         15 . The method of  claim 14  comprising fitting the normalized voltage signal to V(t)=1−a*exp(b*t). 
     
     
         16 . The method of  claim 15  comprising determining an initial slope of the normalized voltage signal, −dV/dt, at time equals zero. 
     
     
         17 . A device comprising:
 first and second cuvette spaces, each cuvette space comprising;   a single wavelength light source constructed and arranged to illuminate at least a portion of the cuvette space;   a second light source at a wavelength different from the first, the second light source constructed and arranged to illuminate at least a portion of the cuvette space;   a light detector positioned to detect light transmitted from the second light source through the cuvette space; and   a fluorescence detector positioned to receive light emitted from the cuvette space at a wavelength different than that emitted from either light source.   
     
     
         18 . The device of  claim 17  wherein the device is powered by a portable battery. 
     
     
         19 . The device of  claim 17  wherein the device is capable of measuring fluorescence simultaneously in two separate samples. 
     
     
         20 . A method of detecting a contaminant in a sample comprising:
 intermittently generating an electroluminescent ultraviolet light;   intermittently generating an electroluminescent visible light;   detecting a quantity of ultraviolet light transmitted through the sample;   detecting a quantity of light fluoresced from the sample at a wavelength different than that of the ultraviolet light and the visible light; and   determining the concentration of the contaminant using both the amount of light transmitted and the amount of light fluoresced.   
     
     
         21 . The method of  claim 20  comprising repeating steps one and two at least twice and extinguishing the ultraviolet light prior to generating the visible light and extinguishing the visible light prior to generating the ultraviolet light.