An important distinction is that the Pocket Colorimeter II and DR300 instruments themselfs are not USEPA approved. But USEPA complant methods can be performed using these instruments. Low range Hach Method 8167 and high range Hach Method 10070 for Total Chlorine follows the operating principles of Standard Methods 4500-Cl G. With the Methods Update Rule and introduction of the Alternative Test Procedures (ATP) program, the Hach method number was removed from the text of 40 CFR 141 and 40 CFR 136 because its test methodology does not significantly differ from the Standard Methods reference method.
To be technical with language, one could say that the Pocket Colorimeters are USEPA approved for the testing of Total Chlorine in Wastewater, if it is used in a way that conforms to Standard Methods 4500-Cl G, and that Hach methods 8167 and 10070 achieve that conformity.
We at Hach have attempted to change the language we use to discuss method Approval versus what we term “Acceptance.” For “EPA-Accepted” Hach methods, we say that the EPA has reviewed Hach Methods and accepted them for use in compliance monitoring. These methods are defined by EPA as Acceptable versions (via letters) of previously approved methods. These methods are generally not published in the Federal Register or in the Code of Federal Regulations. Attached is the facsimile of the EPA-acceptance letter for Total Chlorine Method 8167.
Further, the high-range Total Chlorine Method 10070 is not mentioned in the facsimile letter. The USEPA has ruled that the extension of calibration is within the scope of the method and does not require regulatory approval, provided that the upper limit of the linear range of the instrument or analytical system is not exceeded. Attached is a copy of the USEPA letter addressing calibration extension.