Keep low-range COD testing supplied—without overlooking chloride.

Choose HI93754D-25 when your established mercury-free COD workflow needs a 0–150 mg/L as O2 refill and the sample is free of chloride. The 25 ready-to-use reagent vials reduce reagent preparation without removing the need for a blank, heated digestion or careful method selection. This is a single low-range consumable pack—not an EPA-method substitute, photometer or digestion kit.

Choose chemistry and range together

HI93754D-25 is the orderable pack; HI93754D-0 is the component code identified in the instrument method and US Safety Data Sheet. The low-range mercury-free formulation is designed for chloride-free samples. Do not select it only because its range matches the expected number.

Match the exact instrument procedure

Use HI93754D-0 reagent in the exact-model COD LR procedure: HI97106 selects COD LR; HI83314 and HI83399 select COD LR (16). The verified range is 0–150 mg/L as O2. Follow the instrument’s specified vial adapter and insertion instructions for both zero and read. Official sources conflict on physical vial diameter, so this listing does not assert the diameter of supplied vials or universal adapter fit.

Prepare the blank as deliberately as the sample

Prepare one vial with 2 mL sample and a separate same-lot blank vial with 2 mL deionized water. Follow the full manual’s mixing precautions, then digest at 150 °C for 120 minutes in a separate heater. Cool exactly as directed: allow the initial cooling interval, invert while still warm when instructed, then rack until room temperature without shaking or inverting during final cooling. Never place a hot vial in the photometer adapter. Zero on the blank before reading the sample.

Count vials, not promised results

The pack contains 25 actual pre-dosed vials. A reagent blank consumes one of those vials, leaving 24 sample vials when one blank is prepared for a batch. This explains the benchtop manuals’ 24-test ordering count versus the retail 25-test label. Same-lot blanks and samples are required; follow the manual’s blank-reuse rules and run a blank for each measurement set for improved accuracy. Additional blanks, QC checks, repeats or failed preparations consume more vials. There is no guarantee of 25 reportable results.

Check the matrix before interpreting COD

Chloride must be absent. The HI83314 and HI83399 methods state this specifically for mercury-free reagent. Do not apply the generic 2000 mg/L chloride threshold to this formulation, or assume a routine dilution makes a chloride-containing sample suitable. Confirm the matrix and the validated method before ordering.

Have the complete digestion station ready

Provide a compatible photometer and its specified adapter, a separate digestion reactor capable of 150 °C for 120 minutes, deionized water, accurate 2 mL pipetting/measuring tools and separate clean tips, a cooling rack, and the prescribed safety equipment. The photometer does not heat the vials. A safety shield is strongly recommended by the instrument manuals. Homogenize samples with settling solids as directed; provide the necessary equipment separately.

Confirm reporting acceptance before use

This is the mercury-free dichromate formulation, not the mercury-containing EPA reagent. Hanna cautions that a mercury-free method may not be acceptable for reporting purposes. A shared instrument-manual EPA-adaptation heading is not automatic EPA equivalence or regulatory approval. Verify acceptance with your laboratory’s SOP and reporting authority before use.

Handle and ship as hazardous chemistry

Mercury-free does not mean safe, nonhazardous or suitable for ordinary trash. The reagent remains strongly acidic and contains chromium chemistry; the US SDS identifies sulfuric acid, silver sulfate and potassium dichromate. Use the required PPE and ventilation, and arrange hazardous chemical waste handling. Do not pour reacted material down the drain or dispose of spent vials with ordinary trash. Hanna classifies this product as Dangerous Goods, with ground-only shipping. An SDS air-transport classification is not permission to ship by air. No dispatch date or freight quote is promised.

Manage received stock by its own markings

Keep unused vials in their original packaging in a cool, dark place, subject to the current SDS storage precautions. Check the lot and expiry on received stock; a reference photo does not establish your lot, expiry or available shelf life. No numeric storage temperature or shipping weight is asserted here.