CHEMets Dissolved Oxygen Visual

CHEMets Dissolved Oxygen Visual Method

The level of dissolved oxygen in natural waters is often a direct indication of quality, since aquatic plants produce oxygen, while microorganisms generally consume it as they feed on pollutants. At low temperatures the solubility of oxygen is increased; during summer, saturation levels can be as low as 4 ppm. Dissolved oxygen (D.O.) is essential for the support of fish and other aquatic life and aids in the natural decomposition of organic matter. Waste treatment plants that employ aerobic digestion must maintain a level of at least 2 ppm dissolved oxygen. At elevated temperatures, oxygen is highly corrosive to metals, causing pitting in ferrous systems such as high-pressure boilers and deep well oil recovery equipment. To prevent costly corrosion damage, the liquids in contact with the metal surfaces must be treated, usually by a combination of physical and chemical means. De-aeration can reduce the dissolved oxygen concentration of boiler feedwater from several ppm to a few ppb. Chemical reducing agents such as hydrazine, DEHA, or sodium sulfite, may be used instead of or in conjunction with de-aeration.

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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 color 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 color 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 shelflife. 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.

The Indigo Carmine Method
The reduced form of indigo carmine reacts with D.O. to form a blue product. The indigo carmine methodology is not subject to interferences from temperature, salinity, or dissolved gases such as sulfide, which plague users of D.O. meters. Results are expressed as ppm (mg/L) O2.

The Rhodazine D Method
Test kits for boiler waters and applications requiring trace levels of D.O. (ppb range) employ the Rhodazine D methodology. Developed by CHEMetrics, Inc., and approved by ASTM as the reference method for ppb D.O. determination, the Rhodazine D compound in reduced form reacts with dissolved oxygen to form a bright pink reaction product. The method is not subject to direct temperature, salinity, or dissolved gas interferences.

Oxidizing agents, including benzoquinone, can cause high results. Reducing agents such as hydrazine and sulfite do not interfere. Results are expressed as ppm (mg/L) or ppb (mg/L) O2.

Low-range dissolved oxygen test kits include a special sampling tube for use with boiler feedwater. This device allows the user to break the tip of the ampoule in a flowing sample stream in order to preclude error from contamination by atmospheric oxygen.

Ordering Information:

Analyte: OXYGEN (dissolved)
Method: RHODAZINE D(TM) METHOD (Proprietary chemistry).
Type: CHEMet and Ultra-Low-Range (ULR) CHEMet

K-7511 Dissolved Oxygen 0-20 ppb
K-7540 Dissolved Oxygen 0-40 ppb
K-7599 Dissolved Oxygen 0-100 ppb
K-7518 Dissolved Oxygen 5-180 ppb
K-7501 Dissolved Oxygen 0-1 ppm

Analyte: OXYGEN (dissolved)
Type: CHEMet

K-7512 Dissolved Oxygen 1-12ppm

Kits come in a plastic case and contains everything needed to perform 30 tests: Refill, Comparator, adhesive mounting clamp, permanent mounting clamp, sampling tube, 25 mL sample cup, instructions, and MSDS.





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