Detector for chemical compounds

Systems and methods to analyze contaminants including a plurality of stages configured to detect contaminants in a sample, wherein the plurality of stages are configured to detect a plurality of contaminants at substantially the same time.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a U.S. national stage application claiming the benefit of International Application No. PCT/IB2010/002990, filed on Nov. 23, 2010, which claims the benefit of Indian Application No. 394/KOL/2010, filed on Apr. 7, 2010, the entire contents of which are incorporated herein by reference in their entireties.

BACKGROUND

Natural water may be contaminated with industrial wastes that contain toxic end products. Further, pesticides used for protecting crops may also be washed into and contaminate the water supply. These toxic chemicals have been found to create health hazards and also to damage/destroy various ecosystems.

A class of bacteria that may be found in water supply includes coliforms. Indeed, coliforms are a commonly-used bacterial indicator of the sanitary quality of foods and water. The presence of coliforms may be used to indicate that other pathogenic organisms of fecal origin may be present. This is because feces from warm blooded animals or human beings often leads to the contamination of water by coliforms and other pathogenic organisms.

Coliforms includeE. coli, Salmonella, KlebsiellaandErwinia. These pathogenic organisms may cause intestinal infections, dysentery, hepatitis, typhoid fever cholera etc. Further, coliforms and other chemical contaminants may have toxic effects on the habitants of a contaminated pond/lake, limiting their growth and proliferation.

DETAILED DESCRIPTION

The monitoring of the level of toxins in pond water is generally laborious and costly. An embodiment includes a low cost automatic optical or electronic apparatus to monitor water contamination that can be controlled remotely. In an embodiment, the apparatus can be remotely switched on and data collected. In some embodiments, a broad range contaminant profile of a body of water such as a pond or lake can be obtained. The profile may include turbidity measurements, bacterial count measurements, and measurements of dissolved organic and inorganic chemicals.

Embodiments include optical apparatuses and methods for analyzing pond/lake water. In an embodiment, the apparatus can enable measurement of a broad spectrum of commonly known contaminants of pond/lake water. Contaminants that may be measured include solutes, toxic organic compounds, heavy metal ions and toxic ions like cyanide. Embodiments of the instrument include the use of a simple fluidic systems, and the use of air pressure controlled valve systems for the addition of the reagents. In an embodiment, the apparatus can enable detection of several contaminants at the same times and reduce the use of manpower. In an embodiment the apparatus can includes light emitting diodes, diode detectors, simple fluidic systems and valve systems.

An embodiment relates to an apparatus comprising a plurality of stages configured to detect contaminants in a sample, where the plurality of stages are configured to detect a plurality of contaminants at substantial the same time. In an aspect, one of the plurality of stages is configured to measure turbidity of the sample. In another aspect, at least one of the plurality of stages is configured to measure the presence of biological organisms in the sample. In another aspect, at least one of the plurality of stages is configured to measure the presence of heavy metal ions in the sample. In another aspect, at least one of the plurality of stages is configured to measure the presence of organic compounds in the sample.

In another aspect, the compound is selected from the group consisting of poly-chlorinated biphenyls, dioxins, furans, aldrin, dieldrin, DDT, endrin, chlordane, haxachlorobenzene, mirex, toxaphene, and heptachlor. In another aspect, the apparatus comprises a plurality of stages configured to detect a plurality of different organic compounds. In another aspect, the sample is an aqueous solution. In another aspect, the apparatus further comprises at least one filtration unit. In another aspect, a stage comprises a sample holder, a light source, and a light detector. In another aspect, the light source comprises a light emitting diode (LED). In another aspect, the light detector comprises a diode. In another aspect, the apparatus is configured to be operated remotely.

An embodiment relates to a method comprising obtaining a sample, and analyzing the sample for the presence of biological organisms, heavy metal ions or organic compounds, wherein the analyzing is conducted in an apparatus having a plurality of different sensors configured to detect the presence of biological organisms, heavy metal ions and/or organic compounds at substantially the same time. In one aspect, the method further comprises measuring the turbidity of the sample. In another aspect, the method further comprises adding a lysing reagent to the sample. In another aspect, the method further comprises adding quantum dots to the sample. In another aspect, the method further comprises adding a stain to the sample. In another aspect, the method further comprises mixing the sample. In another aspect, the method further comprises filtering the sample. In another aspect, the apparatus is configured to be operated remotely.

FIG. 1illustrates a schematic diagram of apparatus100according to an embodiment. The apparatus100of this embodiment includes a pipe/tube101which connects a series of stages. As illustrated, this embodiment includes four measurement stages: a turbidity stage108, a biological measurement stage110, an organic molecule stage112, and an ion measurement stage114. Other embodiments may include more or less stages. At one end of the pipe/tube101is an inlet102to which an optional hose104may be attached. The optional hose104may be extended into a pond or lake (or any other source of water to be tested). At the other end of the pipe/tube101is a pump106. The pump106may be a syringe pump or any other kind of pump suitable to draw water from a water source into the inlet102.

In some embodiment, the stages may be separated by filtration units116a,116b, and116c. In the embodiment illustrated inFIG. 1, the turbidity stage108, biological measurement stage110, organic molecule stage112, and ion measurement stage114are separated by filtration units116a,116b, and116c, respectively. Other embodiments, however, may include more or less filtration units. That is, there may be more than one filtration unit between stages or stages having no filtration units between them. In one aspect, the filtration units116a,116b, and116c, comprise multiuse filers. Multiuse filters can be used more than one time so that they do not have to be changed before each set of experiments. In another aspect, the filtration units116a,116b, and116c, comprise single use, disposable filters. The choice of filter material is not important. That is, any filter medium having the specified pore size can be used. Further, the filtrations units116a,116b, and116care generally provided in such a manner that the sizes of the contaminant passed through the filtration units116a,116b, and116care in decreasing order. That is, the filtration units116a,116b, and116care configured in such a fashion so as to restrict passage of particles with larger diameter while allowing passage of particles with smaller diameter. For example, filtration unit116amay include a filter with a pore size of approximately 2 micron or greater. The filter may be, for example, a glass microfiber grade D filter having a 2.7 micron porosity. If the size of the suspended particles is less than 2 microns, a 1.5 micron glass microfiber filter grade 934-AH may be used. Filtration unit116bmay include a filter having a pore size less than 1 micron. The filter may be, for example, a syringe filter including mixed cellulose (Millipore WMCF134501, pore size 0.45 micron). Filtration unit116cmay include a filter having a pore size between 0.1 and 0.3 micron. The filter may be, for example, a syringe filter including PTFE (Teflon®), (Millipore WPTF134501, pore size 0.22 micron). Suitable filters may be obtained, for example, from Millipore Corporation.

FIG. 2illustrates a sample holder118(e.g. a cuvette) according to an embodiment. The sample holder118may be of known dimensions and known volume. In an example embodiment an optical measurement technique is used. In this case, the sample holder118may be at least partially transparent to the light used for measurement.FIG. 3illustrates an example of an optical measurement technique to measure turbidity. A water sample is taken and light from a light source126(e.g., and LED) is shown through the sample. The transmitted light is detected with a light detector128and converted to a voltage signal. The voltage signal is monitored as a function of time. As the particulate matter in the water settles, more light passes through the sample resulting in an increase in the voltage. The turbidity can then be determined as discussed in more detail below. With a transparent (partially transparent) sample holder118, the light sources126and the light detectors128may be located outside of the sample holder118. As the detectors128and light sources126are outside of the sample holder118, and thus not in contact with the experimental samples, they typically will not get soiled. The light sources126may be of any type such as incandescent bulbs, light emitting diodes (LEDs), lasers or any other suitable light source. The light detectors may include, but are not limited to, diode detectors. Suitable light sources can be obtained from companies such as Maxion Technologies, Inc. Suitable light detectors can be obtained from companies such as Arcoptix S.A. and Future Electronics, Inc.

Optionally, a stirrer122can be included in the sample holder118and used to homogenize the sample. The stirrer122may also be used to stir reagents added to the sample as discussed in more detail below. The sample holder118may also include a lower shutter124. The lower shutter123may be opened after the measurements are completed to empty the sample holder118and/or to allow access to the interior of the sample holder118to facilitate cleaning. The lower shutter124may also include a stirrer122comprising a rotatable bar connected to a rotor. The stirrer122may be used for making homogeneous solutions. Alternatively, a magnetic stirrer could be used.

Referring toFIG. 4, the sample holder118includes a float valve1which opens when the sample holder118is empty. When the sample holder118fills to a desired level, the float valve1valve closes. In this manner, each sample holder118may be filled with a water sample to be tested (FIG. 2). In one embodiment, separate sample holders118are provided for each contaminant to be measured. In this manner, all of the contaminants can be measured individually at the same time. In an alternative embodiment, multiple contaminants can be determined in a give sample holder118. That is, the number of sample holders118may be less than the numbers of contaminants to be measured. In this embodiment, the measurement of the contaminants is generally performed sequentially rather than at the same time.

In an embodiment, to detect if a particular toxin is present in the sample and/or measure the concentration of the toxin, light sources126(e.g., light emitting diodes) and light detectors128(e.g., diode detectors) can be configured in some or all of the stages (FIGS. 3,5). That is, one or more stages may be configured with one or more light sources126on one side of the sample holder118and one or more light detectors128located on the opposite side of the sample holder118. The concentration of the contaminant may be determined by measuring the absorption of light at a known wavelength and comparing the absorption to known absorption standards for the contaminant.

FIG. 4illustrates an embodiment of a reagent delivery system120that may be used in conjunction with apparatus100. As illustrated, the reagent delivery120includes four valves: a float valve1, air intake valve2, reagent reservoir valve3, and reagent supply valve4. The illustrated reagent delivery system120also includes a reagent reservoir121, a reagent delivery piston6, and a pressure tube5operatively connecting the reagent delivery piston6to the reagent reservoir121. In this embodiment, the reagent delivery piston6is attached to the float valve1(which controls the water flow inside the sample holder118). As the float valve1rises upon filling the sample holder118with a water sample, the delivery piston6asserts pressure in the pressure tube5. The pressure causes reagent reservoir valve3and reagent delivery valve4to open and deliver an aliquot of the reagent to the sample holder118. Afterwards, when the experiments are completed and the sample are drained out of the sample holder118, the reagent delivery piston6may be dragged down and air valve2opened. When air valve2is opened, air is pulled into the pressure tube5, preparing the reagent delivery system120for the next experiment.

FIG. 5is a circuit diagram illustrating the configuration of four light sources126and four light detectors128according to an embodiment of the apparatus100. This embodiment includes four LEDs126and four diode detectors128. In this embodiment, the output of the diode detectors128is sent to a digital acquisition module130. As illustrated, the digital acquisition module130includes a memory132suitable for data storage and a microprocessor134which can control the operation of the apparatus100. Optionally, the memory132and/or the microprocessor134may also include instructions which allow analysis of the data. In an alternative embodiment, the memory132and/or the microprocessor134are separate from the digital acquisition module130. That is, the memory132and/or the microprocessor134are located in a separate housing from the digital acquisition module130. In an example embodiment, the digital acquisition module130includes wireless communication circuitry136that allows wireless communication, for example, with remote a computer214(FIG. 6). In an alternative embodiment, the wireless communications circuitry136may be contained in a separate module.

FIG. 6illustrates a system200for optical detection of chemical compounds according to an embodiment. In this embodiment, the apparatus100is enclosed inside a container or box202. The container202may include a high speed fan208for quick drying the sample holders118. Optionally, a heating system210can also be used along with or instead of the fan208for drying the sample holders118. The combination of airflow (the fan208) and heating (heating system210) typically works better than aeration or heating alone. Optionally, to attenuate microbial contamination of the apparatus100, UV light sources (e.g. UV LEDs)212may be placed at one or more of the corners of the container202. In an embodiment, UV light sources212are placed in all 8 corners of the container202. The UV light sources212typically are illuminated for sufficient time to kill any microbial contamination. For example, the UV light sources212may illuminate the apparatus100for one hour after the experiments are over.

As discussed above, apparatus100includes wireless communication circuitry136. With the includes wireless communication circuitry136, the apparatus100can receive instructions and send data to a remote computer214. The remote computer214of system200, may include workstations, laptops and smaller computing devices such as personal digital assistants (PDA) or even modern cell phones. Indeed, the remote computer214includes any device capable of wirelessly sending instructions and receiving data. With the wireless communication circuitry136, the system200can be remotely controlled. That is, the apparatus100may be operated by a user who is not in direct physical contact with the apparatus100.

Referring again toFIG. 6, in an embodiment, solar cells204could be used for powering the apparatus100. Indeed, in some embodiments all of the mechanical and electrical components of the apparatus100may be powered by solar cells204. In alternative embodiments, the apparatus100may include batteries206and be battery powered. In still other embodiments, the apparatus100may include solar cells204and rechargeable batteries206charged by solar cells204. Such an embodiment could receive power by solar cells204yet still be able to operate under conditions with minimal light.

In alternative embodiment, detection and measurement may be performed by non-optical techniques. That is, the light sources126and the light detectors128may be replaced with electrical and other techniques. For example, organic molecules may be detected via mass spectroscopy (MS) or nuclear magnetic resonance (NMR). Ions may be detected via atomic absorption.

In the above embodiments, in contrast to conventional devices, turbidity, biologicals, organics, and/or ionic contaminants may be determined with a single device. Further, the apparatus100may be operated such that some or all of the stages108,110,112,114may be operated substantially at the same time. In this manner, turbidity, biologicals, organics, and/or ionic contaminants may be determined quickly and efficiently.

Example embodiments of the method of using the apparatus100will now be described (FIG. 7). In a first step300of an embodiment of the method, water is pumped into the apparatus100by the pump106. In one aspect, the pump106is a syringe type pump. When the piston of the syringe is withdrawn, suction is created which causes the withdrawal of the water from the pond/lake. In an alternative aspect, the pump106may be a peristaltic pump. Other pumps may also be used. As discussed above, the sample holder118may include a detachable bottom part, the lower shutter124. During piston pulls, the lower shutter124is closed. When measurement is complete, the lower shutter124can be opened, facilitating removal of waste solutions from the sample holder118.

In an embodiment, the first sample holder118used for the measurement of turbidity. That is, the first stage is a turbidity stage108. In turbidity stage, the measuring unit can contain a high intensity light emitting diode having emission at approximately 660 nm. Other wavelengths may be used, however, 660 nm is distant from the absorption regions of the most common contaminants and therefore 660 nm is suitable for the measurement of the nonspecific scattering by large particles.

The turbidity may be characterized by the rate of sedimentation. The rate of the sedimentation is generally dependent on the mass and volume of the particles. Thus, the slope of the increase in light intensity provides a measure of the rate of sedimentation. From the rate of sedimentation, the size of the dissolved particle can be calculated. The calculation can be done as follows. For free settling, the total amount of force exerted on a particle can be broken down into four forces: Force due to Acceleration=Gravity Force−Buoyancy Force−Drag Force. The buoyancy (as a function of gravity) and drag forces (as a function of acceleration) can be calculated with equations 1 and 2 below.

These equations can be combined and solved for the settling velocity Vsas a function of the hydrodynamic size (Vp/Ap) of the particles.

Thus, by measuring the settling velocity, the hydrodynamic size of the particles can be calculated.

Additionally, the opacity of the sample may be used to provide a measure of the concentration of the particles. Opacity is generally caused by the absorbance and scattering of larger particles. In an embodiment, absorbance is measured at 660 nm. At this wavelength, there is essentially no loss of light due to absorbance of the particles. That is, the absorbance of the sample is due essentially from scattering from the particles.

The beam of monochromatic radiation directed at a sample solution has an incident radiant power P0. When absorption takes place, the beam of radiation leaving the sample has a radiant power of P. The absorbance of a material can thus be defined in terms of the radiant power of the light transmitted through a sample divided by the radiant power of the light incident on the sample. This relationship is defined in equation 4 below:
A=log10P0/P4
Where A is the absorbance, P0is the radiant power of the incident light and P is the radiant power of the transmitted light. For concentration determinations, P0is determined experimentally by first using a blank with a standard phosphate buffer saline solution and measuring the output voltage at the detector. The output voltages of samples can then be taken and the absorbance calculated with equation 4.

The concentration of the particles in a sample can be determined as follows. The absorbance may be also be defined in terms of concentration of particles in the sample using the Beer-Lambert law:
A=ebc5
Where A is absorbance, e is the molar absorbtivity with units of L mol−1cm−1, b is the path length of the sample—that is, the path length (in centimeters) of the cuvette in which the sample is contained, and c is the concentration of the compound in solution, expressed in mol L−1

For the same type of particles, if the path length is kept constant, a calibration curve of absorbance as a function of concentration can be determined. The molar absorbivity can then be determined from the slope of the calibration curve. The molar absorbivity is typically constant for a solution gathered from same source. Using molar absorbivity and a curvette of know width, the concentration can be calculated with equation 5.

Referring toFIGS. 2 and 7in an embodiment, a portion of the water may be filtered304with filtration unit116aand drawn into a sample chamber118of the biological measurement stage110. An analysis of the biologicals308may then be performed. In this step, a light source126and light detector128are provided which are suitable for detecting biological contaminants such as coliforms. In an example embodiment, the filtration unit116ahas a pore size greater than 2 microns. The filtration unit116filters out larger particulate matter but has pores of sufficient size to allow the passage of biological contaminants to the biological measurement stage110.

In the biological measurement stage110, the biological matter may be treated with a lysing agent306before analysis. A small volume of cell lysing mixture may be added to the water sample306The lysing mixtures generally contains a detergent (e.g., Triton X or SDS) in a buffer (e.g., sodium phosphate buffer 0.5 M, pH-7.2). Other lysing mixtures may be used. The samples may be thoroughly mixed by a mechanical stirrer122. After an incubation period, the optical absorbance may be measured308with light at a suitable wavelength, e.g. 280 nm with a UV LED emitting at 280 nm and a diode detector. Alternative wavelengths may also be used, such as 260 nm. Indeed, light of any wavelength for which proteins or DNA can be detected may be used. To determine the approximate number of biological contaminants, the net protein content or the net DNA content may be measured. Both the net protein content or the net DNA content are proportional to the number of cells. A wavelength of 280 nm may be used to detect proteins while a wavelength of 260 nm may be used for detecting DNA.

Between the biological measurement stage110and the organic molecule stage112, a second filtration may be performed310. In one aspect, the second filtration unit116bmay have a pore size <1 micron. This pore size can eliminate larger particles and larger cells but allows the common non-biological organic contaminants to pass. Some of the most toxic organic compounds, commonly known as “dirty dozen,” may be monitored by using such a filter. These 12 chemicals are poly-chlorinated biphenyls, dioxins, furans, aldrin, dieldrin, DDT, endrin, chlordane, hexachlorobenzene, mirex, toxaphene, and heptachlor.

These organic compounds have an absorbance at specific wavelengths in the UV, VIS or IR regions. Thus, light emitting diodes having the emission wavelengths in the regions where the compounds have their absorption may be selected. Seven of the compounds and their absorbance are listed in Table 1 below. The information in Table 1 generally known.

TABLE 1Table 1 describes the name of the organic contaminants of the pondwater and their optical detection processName of theAbsorbanceCompoundwavelengthSourceDetectorPBC245nmUV LEDUV diodedetectorFurans284nmUV LEDUV diodedetectorDioxin7.01micronIR laser LEDquantum-cascadedetectorsendrin6.25micronIR laser LEDquantum-cascadedetectorsDDT (nile red550nmVIS LEDDiode detector atfluorescence)663 nmaldrin8.48micronIR laser LEDquantum-cascadedetectorsdieldrin10.98micronIR laser LEDquantum-cascadedetectors

Mid-IR detectors have a wide-ranging potential applications in sensing, security, and especially in NIR spectrometry. Indium phosphide (InP)-based quantum-cascade detectors (QCDs) operating from 4 and 17.5 μm are now available. In an embodiment similar to the embodiment illustrated inFIG. 1, the apparatus100includes set of seven sample holders118for organic analysis, one for each of the seven chemicals list in Table 1. The number of sample holders118, however, is not restricted. The apparatus100may include sample holders118for each of the “dirty dozen” organic compounds. Indeed, the apparatus100may include sample holders118for other compounds as well. Embodiment may also include fewer sample holders118. Further, one or more of the same holders118may be equipped with a reagent reservoir121. The reagent reservoir121may include, for example, a stain. A stain is a compound that bonds to the contaminant and, when excited by a light source, provides light emission in a known wavelength when bound. By adding a stain312, a contaminant that otherwise is difficult to detect may be detected and its concentration measured314. For example, for the detection of DDT, a reagent reservoir121containing the stain nile red may be provided. The nile red may be added to the water sample in the organic molecule stage112to detect DDT312. Optionally, the mixture may be stirred313. Other stains useful for the detection of other organic contaminants, of course, may be used as desired.

In some embodiments, the apparatus100may include an ion measurement stage114and a filtration unit116cprovided between the ion measurement stage114and the organic molecule stage112for further filtering316of the water. The filtration unit116cmay have pores of approximately 0.22 micron. This pore size is suitable for eliminating bigger molecules and compounds but allowing ions through.

The ions may be quantified320, for example, by a method based on quenching of surface modified Quantum dots specific for the binding of particular ions such as cyanide, copper(II), Fe(II)/Fe(III) etc. In an alternative embodiment, a chemical analysis method may be used for ion detection and measurement. A chemical analysis method, may include additional chemicals and performance of additional reactions. The quantum dots and/or additional chemical reagents may be added318via a regent reservoir121similarly to the biological measurement110and organic molecule stages112. Optionally, the mixture of quantum dots and water sample may be stirred319.

Surface modified quantum dots, when excited, fluoresce at a specific wavelength. Further, modified quantum dots may be modified such that they have specificity to bind to a specific ion. In an embodiment, the binding of the ion to the modified quantum dots quenches the fluorescence emission in proportion to the concentration of the ion. Accurate concentration of the ions may be determined with a suitable calibration curve. In one aspect, the fluorescence can be measured by using an LED light source126emitting light at the excitation wavelength of the quantum dots and detecting the emission with a diode detector128configured for the range of emission wavelength of the quantum dots.

After the completion of the experiments, the pump106pumps out the filtration united water. Optionally, the lower shutter124may be detached to allow cleaning of the sample holder118. The sample holders118may be washed with the filtration united water pumped with the pump106.

FIG. 7illustrates an example embodiment method that comprises the following steps: performing turbidity measurements302, performing biological measurements308, performing organic molecule measurements314, and performing ion measurements320. In other embodiments, one or more of these measurements is not performed. Further, in other embodiments, one or more of the filtering steps304,310, and316may be omitted, as can the addition of reagents in steps306,312, and318and the stirring steps307,313, and319.

While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are no intended to be limiting, with the true scope and spirit being indicated by the following claims.