In the water business testing for free chlorine happens quite frequently (as Scott just said)… and we know of two ways to make that task easier:

• DPD ReagentStrips — If you use DPD-1 to test for free chlorine residual, then undoubtedly you do so using DPD in powder or tablet form. Both methods work, but DPD-1 ReagentStrips make testing for free chlorine residual in water a faster and easier process while staying in compliance with 4500-CL G. Simply insert a DPD-1 ReagentStrip into a 10mL water sample, move it back and forth (liberated required DPD chemistry off of reagent pads), and read visually or with your favorite meter.
   
• SenSafe™ Free Chlorine Water Check — In the original recommendation letter from the USEPA, dated October 2003: “We believe that the ITS test strips will provide the regulatory community with a valuable option for monitoring free chlorine levels in drinking water.” This method bears USEPA Approval for in drinking water applications.

While both testing methods make free chlorine residual testing much easier without losing accuracy, we highly suggest check with your State and Local inspectors first before using either product for compliance monitoring… because as you know (probably better than we do!), sometimes State/Local regulation changes do not always keep up with Federal Regulation changes.

Per the request of several men and women currently serving in the United States Armed Forces and other branches of the Unites States Government, we will begin posting possible alternate products for popular (established) NSN’s (National Stock Numbers) related to water quality testing.

NSN: 6550012191061, 6550014257957 — Chlorine Test Tablets

“DPD REAGENT TEST TABLETS FOR CHLORINE ANALYSIS. PACKAGED IN INCREMENTS OF 100. LAMOTTE.”

Alternatives:

• DPD 1, 3 and 4 ReagentStrips — Faster and more convenient than traditional DPD test tablets. No MSDS required. Safe to use on production room floors of food processing facilities. EPA Compliant testing method. Packaged in bottles of 50 or individually wrapped in foil packs. Costs as low as 8 cents a test.

eXact^® Strip DPD ReagentStrips

Note: We have found that the products suggested above meet or exceed the specifications of the original NSN (National Stock Number) item. This does not mean, though, that you may substitute them in place of the item on a Government Contract. We provided the above information as possible sources of water quality testing products for consideration in future Contracts/Bids only.

DPD ReagentStrips: Look like test strips, but function like a totally convenient way to precisely administer measured amounts of DPD into a 10 mL water sample. All the reagents, buffers and indicators come neatly impregnated on the pads at the end of an ergonomic PVC strip.

Simply swish the pads around in your sample for 20 seconds, remove the strip, throw it away, and read your sample in your preferred colorimeter. DPD ReagentStrips fall under the guidelines of EPA Compliance and may, in most cases, be used in place of all other DPD methods. . . and they don’t require MSDS.

Previously, DPD came in one of three forms: powder pillow, tablet or liquid. Each has its benefits. . . and each has its downfalls.

Powder Pillow: The most popular form of DPD. Precise amounts of the reagent come in single-dose foil ‘pouches’ that the user tears open and pours into their sample. Sounds like a great idea, yes, but try using these things in a ‘wet’ or windy environment. Anyone who works in the field will know what that means. MSDS required.

Liquid DPD: Cheap as can be, but with that inexpensive price comes an incredibly short shelf-life compared to other DPD delivery systems. MSDS required.

DPD Tablets: Very inexpensive, very stable. Great way to deliver exact amounts of DPD into samples, except for one small problem: DPD tablets do not dissolve smoothly or easily in cold or hard water. In either type of water, DPD tablets typically leave undissolved solids floating in the sample and when analyzing water samples using colorimeters the suspended solids can cause erroneous readings.

Fast Dissolving DPD Tablets: Same reagent dispensing mechanism as regular DPD tablets, but they dissolve faster. These, too, may leave undissolved materials in samples such as elements of the binding agent(s) which held the tablets together prior to immersion in the sample.

UPDATE: For certain free chlorine testing applications, states now have the ability to approve the use of EPA Approved SenSafe(tm) Free Chlorine Check test strips. Please consult with your State and/or Local Health Departments to see if your State has approved their use. Benefits include faster test times and no monochloramine interference.