Oxidant sensor
A microfluidic device for measuring an amount of an oxidant in a solution is disclosed. The device includes a microfluidic substrate configured to mix a solution sample to be analysed with an indicator dye solution containing an indicator dye under conditions suitable for some of the indicator dye to react with any oxidant in the solution to produce an oxidant measurement solution having a reduced indicator dye concentration that is indicative of the amount of oxidant in the solution, the microfluidic substrate including an optical reading window through which the reduced indicator dye concentration in the oxidant measurement solution can be measured optically.
1. A microfluidic device for measuring free chlorine and combined chlorine in an aqueous sample, the device comprising a microfluidic free chlorine measurement module and a microfluidic combined chlorine measurement module,
the free chlorine measurement module comprising a solid substrate comprising:
an aqueous sample inlet port configured to receive an aqueous sample to be analysed for free chlorine and combined chlorine,
an indicator dye solution inlet port configured to receive an indicator dye solution containing an indicator dye capable of reacting with any free chlorine in the aqueous sample to produce a first reduced indicator dye concentration that is indicative of the free chlorine concentration in the aqueous sample,
a first microfluidic flow channel in fluid communication with the aqueous sample inlet port and the indicator dye solution inlet port and configured to mix the aqueous sample and the indicator dye solution and to flow the combined fluids along the channel under conditions suitable for the indicator dye to react with any free chlorine and produce a free chlorine measurement solution having a first reduced indicator dye concentration,
a free chlorine measuring chamber in fluid connection with the first microfluidic flow channel at a downstream end thereof and configured to receive the free chlorine measurement solution, the free chlorine measuring chamber comprising an optical reading window through which the first reduced indicator dye concentration in the free chlorine measurement solution can be measured optically,
a transfer port in fluid communication with the free chlorine measuring chamber and/or the first microfluidic channel and configured to transfer the free chlorine measurement solution from the free chlorine measurement module to the combined chlorine measurement module,
the combined chlorine measurement module comprising a solid substrate comprising:
a free chlorine measurement solution inlet port configured to receive the free chlorine measurement solution from the transfer port,
a combined chlorine release agent inlet port configured to receive a solution containing a combined chlorine release agent capable of reacting with any combined chlorine in the free chlorine measurement solution to produce liberated chlorine from the combined chlorine,
a second microfluidic flow channel in fluid communication with the free chlorine measurement solution inlet port and the combined chlorine release agent inlet port and configured to mix the free chlorine measurement solution and the solution containing the combined chlorine release agent and to flow the combined fluids along the channel under conditions suitable for the combined chlorine release agent to react with combined chlorine in the free chlorine measurement solution to produce liberated chlorine and for the indicator dye in the free chlorine measurement solution to react with any liberated chlorine to produce a combined chlorine measurement solution having a second reduced indicator dye concentration that is indicative of the combined chlorine concentration in the aqueous sample,
a combined chlorine measuring chamber in fluid connection with the second microfluidic channel at a downstream end thereof and configured to receive the combined chlorine measurement solution, the combined chlorine measuring chamber comprising an optical reading window through which the second reduced indicator dye concentration in the combined chlorine measurement solution can be measured optically, and
a waste outlet port in fluid communication with the combined chlorine measuring chamber and/or the second microfluidic channel and configured to allow the combined chlorine measurement solution to exit the device.
2. The microfluidic device of claim 1 , wherein the microfluidic device is a unitary device comprising the microfluidic free chlorine measurement module and the microfluidic combined chlorine measurement module.
3. The microfluidic device of claim 1 , wherein the microfluidic device is a multilayer microfluidic device comprising a first and second outer chips and first and second intermediate chips and wherein the free chlorine measurement module is formed between the first outer chip and the first intermediate chip, and the combined chlorine measurement module is formed between the second intermediate chip and the second outer chip.
4. The microfluidic device of claim 3 , wherein the aqueous sample inlet port, the indicator dye solution inlet port and the combined chlorine release agent inlet port are formed in the first outer chip.
5. The microfluidic device of claim 4 , wherein the transfer port and the free chlorine measurement solution inlet port are formed between the first intermediate chip and the second intermediate chip.
6. The microfluidic device of claim 5 , wherein the free chlorine measuring chamber forms the transfer port and the free chlorine measurement solution inlet port.
7. The microfluidic device of claim 1 , wherein the microfluidic device comprises two or more microfluidic substrates connected in series or parallel, with at least one of the substrates comprising the microfluidic free chlorine measurement module and at least one of the other substrates comprising the microfluidic combined chlorine measurement module.
8. The microfluidic device of claim 1 , wherein the first microfluidic flow channel is configured so that the aqueous sample and the indicator dye solution have a residence time of from 0.5 minutes to 5 minutes at the specific flow rate used.
9. The microfluidic device of claim 8 , wherein the second microfluidic flow channel is configured so that the free chlorine measurement solution and the solution containing the combined chlorine release agent have a residence time of from 1.5 minutes to 10 minutes at the specific flow rate used.
10. A method of measuring the free chlorine content and combined chlorine content in an aqueous solution using the microfluidic device of claim 1 , the method comprising:
passing an aqueous sample to be analysed through the aqueous sample inlet port of the microfluidic device;
passing an indicator dye solution through the indicator dye solution inlet port of the microfluidic device;
mixing the aqueous sample and the indicator dye solution in the first microfluidic channel of the microfluidic device under conditions suitable for the indicator dye to react with any free chlorine in the aqueous sample and produce a free chlorine measurement solution having a first reduced indicator dye concentration,
measuring the first reduced indicator dye concentration optically in the free chlorine measuring chamber,
transferring the free chlorine measurement solution from the free chlorine measuring chamber and mixing the free chlorine measurement solution and the solution containing the combined chlorine release agent in the second microfluidic channel under conditions suitable for the combined chlorine release agent to react with combined chlorine in the free chlorine measurement solution to produce liberated chlorine and for the indicator dye in the free chlorine measurement solution to react with any liberated chlorine to produce a combined chlorine measurement solution having a second reduced indicator dye concentration that is indicative of the combined chlorine concentration in the aqueous sample,
measuring the second reduced indicator dye concentration optically in the combined chlorine measuring chamber, and
determining the free chlorine concentration and the combined chlorine concentration in the aqueous sample from the measured first reduced indicator dye concentration and the second reduced indicator dye concentration, respectively.