Hanna HI96710 Offers

The portable photometer is for the measurement of pH, free chlorine, and total chlorine, and features an advanced optical system; the combination of a special tungsten lamp, a narrow band interference filter, and silicon photodetector ensure accurate photometric readings every time. The cuvette locking system ensures that the cuvette is inserted into the measurement cell in the same position every time to maintain a consistent path length.

Features

• CAL Check™ - Allows for performance verification and calibration of the meter using a CAL Check NIST traceable secondary standard
• GLP - Records the date of the last user calibration performed
• Built in timer - Ensures the appropriate reaction time is used for the chemical reaction. At the end of the timer the meter will automatically take the reading. This feature ensures consistency across multiple users
• Indexing indent on meter - The meter has an indent that allows for a lock and key fit with the cuvette cap. This ensures that the cuvette is indexed consistently (same position) in order to maintain the same path length for accurate results
• Cooling Lamp Indicator - It is necessary to maintain a consistent temperature of the optical components in order to maintain a narrow wavelength band of light. This photometer has a cooling lamp indicator that is displayed for a short period of time before each measurement in order to allow the components to cool and obtain the highest accuracy possible
• Error messages - Messages on display alerting to problems including no cap, over range and under range readings, and light source error
• Auto-shut off - Automatic shut off after 10 minutes of non-use when the meter is in measurement mode. Prevents wastage of batteries in the event the meter is accidentally not turned off
• Battery status indicator - The instrument has a battery level indicator to display reaming life as follows:
  • 3 lines for 100% capacity
  • 2 lines for 66% capacity
  • 1 line for 33% capacity
  • Battery icon blinks when the capacity is less than 10%
• Units of measure - Appropriate unit of measure is displayed along with reading

Significance of use

Three critical parameters that can be tested to ensure good water quality are pH, free chlorine, and total chlorine. Chlorine is one of the most commonly used disinfectants for drinking water, wastewater, and water used for pools and spas. It can be added to in various forms including calcium hypochlorite, sodium hypochlorite, or in some instances, chlorine gas. When added to water, chlorine creates hypochlorous acid (HOCl) which dissociates into hypochlorite ion (OCl).

HOCl ↔ H+ + OCl

hypochlorous acid ↔ hydrogen ion + hypochlorite ion

HOCl is the form of chlorine that acts as a stronger disinfectant as compared to OCl. To ensure the added chlorine is effective at sanitizing, the pH of the water must be taken into account. Around pH 7.5, HOCl and OCl are present in relatively equal amounts. Below pH 7.5, the equilibrium shifts to favor HOCl; above pH 7.5, the equilibrium shifts to favor OCl. Depending on the application, addition of chlorine is effective when added to water with a neutral or slightly acidic pH value.

When chlorine is first added to water, it is available as free chlorine. The measurement of free chlorine signifies the amount available for disinfection. Once chlorine begins to sanitize bacteria and pathogens present in the water, it becomes combined chlorine; combined chlorine is no longer available to act as a disinfectant. The measurement of total chlorine signifies the amount of free chlorine and combined chlorine. With both free and total chlorine measurements, a drinking water operator or pool owner can determine if there is enough chlorine available for disinfection.

The photometer offers multiple methods within one meter. pH determination uses the phenol red method while free and total chlorine determination uses an adaptation of the EPA method 330.5 and Standard Method 4500-Cl G. The reagents are in powder and liquid form depending on the parameter being tested.

When the appropriate reagent is added to the sample, it will display a color change; the greater the concentration, the deeper the color. The associated color change is then colorimetrically analyzed according to the Beer-Lambert Law. This principle states that light is absorbed by a complementary color, and the emitted radiation is dependent upon concentration. For determination of pH and free and total chlorine, a narrow band interference filter at 525 nm (green) allows only green light to be detected by the silicon photodetector and omits all other visible light emitted from the tungsten lamp. As the change in color of the reacted sample increases, absorbance of the specific wavelength of light also increases, while transmittance decreases.

Simple to use

1. Press "CAL Check" to enter validation procedure
2. Insert CAL Check Standard A cuvette and press "Zero." When the display reads "0.0," remove cuvette
3. Insert CAL Check Standard B cuvette and press "Read"
4. Compare the displayed reading with the value on the Certificate of Analysis. If the reading is not in the stated range, the meter needs to be calibrated