Kidneys filter our blood; removing harmful waste products to excrete and keeping the useful stuff in! They are essential for the body to function – without these waste products would rise to dangerous levels in your blood and cause health issues. Dialysis is a procedure to keep the function of the kidneys continuing when a person’s own have stopped working properly.
Blood from the patient is pumped through membranes in a machine, which are surrounded by dialysis fluid that mimics the body containing water, glucose and salts etc. The waste products diffuse out the blood to the surrounding solution and the needed substances will stay in the blood flow. What’s vital to this process is that the dialysis solution accurately mimics the blood and does not contain any unwanted contaminants.
Key contaminants of water that must be tested for and if present removed before use in dialysis fluid is chlorine as prescribed in ISO 13959:2014. Chlorine is used to disinfect mains water for drinking purposes both in free and combined forms.
The low levels of chlorine that need to be detected in dialysis fluid mean that for accurate analysis quantitative testing methods have been favoured over cheap test strips. Using DPD, it is first added to the sample which reacts with any free chlorine to form a pink colour which can be measured using a photometer.
Chloramines (mg/L) = total chlorine result (mg/L) – free chlorine result (mg/L)
If using DPD tablets:
Chloramines (mg/L) = DPD 3 result (mg/L) – DPD 1 result (mg/L)
Alternatively, a DPD 4 tablet alone can be used but this only measures total chlorine, which is fine if all you want to do in ensure you’re conforming to ISO 13959.
The detection limit of the DPD method is 0.02 mg/L. It is a quantitative test and non-subjective method therefore suitable for use in the measurement of water to be used in the production of dialysis fluid. It still requires a little bit of training for users to get used to.
Since this method, many dialysis unit have moved on to using ChloroSense which has the same performance as DPD but is easier to use with a lot less training. It has a detection limit of 0.04 mg/L but is still suitable for renal units that need 0.1 mg/L total chlorine or less to pass. 
For more information about chlorine testing for any application please get in touch with one of our technical support team on 01954 233 120, send us an email on support@camlab.co.uk or fill in the contact form below.
