Methods
The DPD Method
In the USEPA-approved DPD methodology, free chlorine reacts with DPD to form a pink product. When ammonia or amines are present, some of the chlorine may exist as combined chlorine. Combined chlorine will not interfere with the free chlorine results, provided the readings are taken at one minute. To determine total chlorine (the sum of free and combined), use the A-2500 Activator Solution (potassium iodide) supplied in the kit. Results are expressed as ppm (mg/L) Cl2.
The DDPD Method
The DDPD method is derived from the DPD method. Test kits that employ this chemistry are well suited for use where biocides and chromate corrosion inhibitors are used simultaneously. DDPD reacts with free chlorine to form a purple product. When ammonia or amines are present in the sample, some of the chlorine may exist as combined chlorine. To determine total chlorine (the sum of free and combined), use the A-2500 Activator Solution (potassium iodide) that is supplied in the kit. Results are expressed as ppm (mg/L) Cl2.
CHEMetrics’ DDPD method is also applicable to the direct determination of hypochlorite concentrations in various cleaning preparations and disinfectants prior to their dilution. The DDPD compound reacts with hypochlorite ions to form a purple color. Results are expressed as percent (%) NaOCl.
How to use a CHEMets Kit
To perform a test, immerse the CHEMet ampoule into the sample and snap off the tip (Step 1)- the correct volume of sample is automatically drawn in, filling the ampoule; a small inert gas bubble remains in the ampoule. To facilitate mixing the sample and reagent, tilt the ampoule back and forth so the bubble travels from end to end (Step 2). In 2 minutes or less, quantify the result by comparing the filled ampoule to the appropriate colour standard(s) (Step 3). For higher concentrations, the flat comparator is used. For lower concentrations, the round comparator is used. The ampoule is compared with the standards until a colour match is found. Kits include 30 ampoules, comparator(s), accessory solution(s)(when necessary), a sample cup, and instructions. Refill packs of 30 ampoules and accessory solutions are available separately. Comparators have a 2-year shelf life. Material Safety Data Sheets are provided in test kits. CHEMets ampoules are designed for maximum simplicity and accuracy. Each glass ampoule is 7 mm in diameter, 100 mm in length, with a tapered, pre-scored tip; reagents are vacuum-sealed inside.
Ordering Information:
Analyte: CHLORINE (free & total)
Method: DPD METHOD (EPA-approved in many states for reporting drinking water data).
Type: CHEMet
K-2504 Chlorine 0-1 and 0-5 PPM
K-2504D Chlorine 0-25 & 0-125 ppm
K-2504A Chlorine 0-50 & 0-250 ppm
K-2504B Chlorine 0-100 & 0-500 ppm
K-2504C Chlorine 0-400 & 0-2000 ppm
K-5808 0-1.55% as NaOCl
K-5816 0-12.5% as NaOCl
Analyte: CHLORINE (free & total)
Method: DDPDtm CHEMISTRY (Proprietary chemistry providing more resistance to interferences than DPD).
Type: CHEMet and Ultra-Low-Range (ULR) CHEMet
K-2511 Chlorine 0-0.20 PPM
Test kits contain 30 ampoules, snap cup, accessory solutions (when necessary), MSDS, and instructions.
i2504