Hach-Lange PHC725 User Manual

User Manual

PHC725

Safety information

DOC022.52.80432

Precautionary labels

Read all labels and tags attached to the instrument. Personal injury or damage to the instrument could occur if not observed. A symbol on the instrument is referenced in the manual with a precautionary statement.

Electrical equipment marked with this symbol may not be disposed of in European domestic or public disposal systems. Return old or end-of-life equipment to the manufacturer for disposal at no charge to the user.

Specifications

W A R N I N G

Chemical exposure hazard. Obey laboratory safety procedures and wear all of the personal protective equipment appropriate to the chemicals that are handled. Refer to the current safety data sheets (MSDS/SDS) for safety protocols.

C A U T I O N

Personal injury hazard. Glass components can break. Handle with care to prevent cuts.

Specifications are subject to change without notice.

Specifications Details

Probe type Digital combination glass pH probe with refillable electrolyte and built-in temperature sensor

Body material Glass

pH range pH 0 to 14

pH resolution User-selectable stabilization time and resolution—Fast: 0.1, Fast: 0.01, Medium: 0.01, Slow:

0.01 or Slow: 0.001

pH accuracy ±0.01 pH

Sodium (alkalinity) error <0.3 pH at pH 13 in 0.1 M NaOH

Slope –59 mV/pH (85 to 115% at 25 °C (77 °F) per Nernstian theoretical value)

Isopotential point pH 6.00

Temperature compensation 30 kΩ NTC thermistor

Temperature accuracy ±0.3 °C (±0.54 ° F)

Operating temperature –10 to 100 °C (14 to 212 °F)

Storage temperature 5 to 40 °C (41 to 104 °F)

Junction type Annular porous ring

Reference type Red Rod

Electrolyte Refillable, saturated KCl

Specifications Details

Storage solution Saturated KCl

Minimum sample depth 14 mm (0.55 in.)

Dimensions Body diameter: 12 mm (0.47 in.)

Body length: 103 mm (4.1 in.)

Total length: 200 mm (7.87 in.)

Cable length: 1 m (3.28 ft)

Cable connection M12 digital output and connector compatible with HQd meters

Radiometer Analytical’s Red Rod technology: Encapsulation of reference elements with a red protection tube.

Product overview

The probe is a digital pH combination electrode with refillable electrolyte, a glass body and an integrated temperature sensor. The probe is for laboratory use and measures pH in general aqueous samples.

Note: Do not use the probe with organic solvents, emulsions, samples with high solids content or high alkaline sample types.

A 59-mL bottle of reference electrolyte filling solution (saturated KCl solution) is included with the probe. Refer to Figure 1.

Figure 1 Probe overview

1 Probe soaker bottle 5 Probe soaker bottle holder

2 Filling-hole cap 6 Reference junction

3 Protective tape and filling-hole 7 Glass bulb and temperature sensor

4 Cable, 1 meter (3.28 ft)

Preparation for use

Prepare the probe before a calibration or a sample measurement.

1. Turn the probe soaker bottle cap counter-clockwise to loosen the cap.

2. Remove the soaker bottle from the probe.

3. Fully rinse the reference junction and the glass bulb with deionized water to remove

all of the storage solution or possible salt particles. Dry with a no-lint cloth.

4. Remove the protective tape from the filling hole before initial use (refer to Product

overview on page 2). Discard the protective tape.

5. Add the filling solution to the probe as necessary (refer to Fill the probe

on page 11). The filling solution must be above the standard solution or the sample level during measurement or calibration (Figure 2).

6. For Red Rod probes, make sure that there is approximately 0.5 cm (0.2 in.) of KCl crystals in the filling solution in the probe. Refer to Table 1. For measurements at temperatures higher than 60 °C (140 °F), add KCl crystals through the filling hole. Refer to Table 1 to calculate the quantity of KCl crystals to add. The quantity of necessary KCl crystal increases linearly from 60 to 100 °C.

7. For Red Rod probes, make sure that the KCl crystals move freely through the liquid when the probe is inverted. If necessary, shake the probe to loosen the crystals.

8. Make sure that the filling hole is open during measurement for the correct flow of the filling solution.

Note: For the best stabilization time, condition the probe for 2 hours in pH buffer 4.01 before use, if the probe was not used for 3 weeks or more. In low ionic strength (LIS) samples, condition the probe for a maximum of 5 minutes in the sample before use. In all other cases a condition before use is not necessary.

Figure 2 Filling solution level

1 KCl crystals

2 Filling solution level 4 Standard solution or sample level

Red Rod probes only

3 Filling solution

Table 1 KCl crystal level for Red Rod pH probes

Temperature Amount of KCl crystals Add Temperature Amount of KCl crystals Add

60 °C (158 °F) 0.5 g (0.5 cm) 0 g 90 °C (194 °F) 0.875 g 0.375 g

70 °C (158 °F) 0.625 g 0.125 g 100 °C (212 °F) 1.0 g (1.0 cm) 0.5 g

80 °C (176 °F) 0.750 g 0.25 g

Calibration

Before calibration:

The probe must have the correct service-life time stamp. Set the date and the time in the meter before the probe is attached.

It is not necessary to calibrate again if a calibrated probe is moved from one HQd meter to another. Make sure that the additional meter is configured to use the same calibration options.

Before calibration:

To view the calibration data, push , then select View Probe Data>View Current Calibration.

If two probes are connected, push the UP or DOWN arrow to change to the single display mode to show the Calibrate option (available only on HQ40d and HQ440d meters).

Prepare the probe for use (refer to Preparation for use on page 2).

Calibration notes:

• Use buffers that are two pH units apart.

• Select additional standard sets with the minimum number of calibration points in the Calibration Options. For a two-point calibration, select: one buffer with a pH above and one buffer with a pH below the sample pH. For a one-point calibration, select the buffer nearest to the sample pH.

• The calibration is recorded in the probe and the data log. Send the calibration to a PC, a printer or a flash memory stick if connected.

• Air bubbles under the sensor tip can cause a slow response or an error in the measurement. If there are bubbles under the sensor tip, carefully shake the probe to remove the bubbles.

• Make sure that the filling hole is open and above the sample solution level.

• Use a laboratory stirrer or shake the probe from side to side in the solution to refresh the reference junction.

• The meter display shows "Stabilizing" and a progress bar as the probe stabilizes in the standard. The display shows the buffer and the temperature corrected pH value when the measurement is stable.

• The calibration and sample measurement conditions must be as similar as possible (e.g., the temperature of the solution, the stir procedure, the stir rate and the position of the probe).

• If a calibration error occurs, refer to Troubleshooting on page 12.

1. Connect the probe to the meter. Make sure that the cable locking nut is correctly connected to the meter. Set the meter to on.

Calibration procedure:

2. Push Calibrate.

The display shows the buffers that are necessary for calibration.

3. Prepare the fresh buffers in separate beakers or applicable containers.

4. Rinse the probe with deionized water. Dry with a no-lint cloth.

5. Put the probe in the pH buffer solution and stir lightly. Make sure to fully put the reference junction into the standard.

6. Push Read. Wait

until the reading stabilizes.

7. Do steps 4–6 again to collect the minimum number of calibration points specified in the calibration options.

Sample requirements

8. Push Done to view

the calibration summary.

Note: The display will not show "Done" until the minimum number of calibration points is collected.

9. Push Store to accept the calibration and go back to the measurement mode.

N O T I C E

Some probes are not compatible with specific sample types. Probe damage can occur.

• Samples must be aqueous. The probe can also make measurements in partially aqueous or some water-miscible solvents. Read the results with caution because the full pH scale changes when the solvent system changes.

• Probes with a Red-Rod reference system are compatible with solutions that contain silver complexing or binding agents (e.g., TRIS, proteins and sulfides), as they have an encapsulated reference system.

• Proteins can collect on the sensing element. Make sure that the probe stays clean when these types of samples are measured.

• Do not use the probe in solutions that are out of the temperature range of the probe. Refer to Specifications on page 1.

• For low ionic strength (LIS) or high purity samples, use an LIS chamber or a flow cell to prevent sample contamination.

Measurement

Before measurement:

The probe must have the correct service-life time stamp. Set the date and the time in the meter before the probe is attached.

If the complete traceability is necessary, enter a sample ID and an operator ID before the measurement. Refer to the HQd meter manual for more information.

A regular calibration is necessary for the best measurement accuracy (refer to Calibration on page 3).

Prepare the probe for use (refer to Preparation for use on page 2).

Measurement notes:

• Data is automatically stored in the data log when Press to Read or Interval is selected in the Measurement Mode. When Continuous is selected, data is only stored when Store is pushed.

• Air bubbles under the sensor tip can cause a slow response or an error in the measurement. If there are bubbles under the sensor tip, carefully shake the probe to remove the bubbles.

• For the best stabilization time, condition the probe for several minutes in the sample or in a solution comparable to the sample in terms of pH and ionic strength before the initial sample measurement.

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