Integrated water testing system and method for ultra-low total chlorine detection

A method of for determining an amount of total chlorine in water for dialysis, the method comprising:

• (a) providing a water purification machine in fluid communication with a dialysis machine;
• (b) providing a total chlorine detection system, in fluid communication with the water purification machine, the total chlorine detection system including
• a first chamber in fluid communication with an iodide reservoir and a water sample source,
• a second chamber in fluid communication with a reducing agent reservoir, and
• an electrode pair associated with a voltage source, wherein one electrode of the electrode pair is in contact with an iodide fluid in the first chamber and the other electrode of the electrode pair is in contact with a reducing agent solution in the second chamber, and wherein the first and second chambers are separated by a membrane that allows charge but not fluid to pass between the chambers;
• (c) measuring a background voltage VB in the electrode pair, the background voltage VB associated with any tri-iodide in the system before introduction of a water sample;
• (d) providing a water sample from the water purification machine, the water sample including an amount of total chlorine;
• (e) metering an amount of the water sample into the system;
• (f) monitoring a baseline voltage V0 via the electrode pair, the baseline voltage V0 associated with tri-iodide present in the water sample before application of a tri-iodide generating voltage to the electrode pair;
• (g) generating a first amount of tri-iodide from the water sample by applying a voltage V1 to the electrode pair for a time t1;
• (h) thereafter monitoring a first voltage V2 in the electrode pair, optionally for a time t2, the first monitored voltage V2 associated with a sum of the amount of total chlorine and the first amount of tri-iodide;
• (i) thereafter generating a second amount of tri-iodide from the water sample by applying a voltage V3 to the electrode pair for a time t3;
• (j) thereafter monitoring a second voltage V4 in the electrode pair, optionally for a time t4, the second monitored voltage V4 associated with a sum of the amount of total chlorine and the first and second amounts of tri-iodide;
• (k) optionally thereafter generating a third amount of tri-iodide from the water sample by applying a voltage V5 to the electrode pair for a time t5, the third amount of tri-iodide corresponding to the third amount of tri-iodide;
• (l) optionally monitoring a third voltage V6 in the electrode pair, optionally for a time t6, the third monitored voltage V6 associated with a sum of the amount of total chlorine and the first, second and third amounts of tri-iodide;
• and
• (m) calculating the unknown total chlorine concentration in the water sample from the baseline voltage V0, the background voltage VB, and at least one of the first, second and optional third monitored voltages V2, V4 and V6.