PRO6152 — pH electrode HF acid resistance: a glass pH electrode for acidic wastewater that contains fluorine, resistant to hydrofluoric acid up to 2000 ppm HF. Glass body, ceramic junction and a refillable long-life reference. It has a refillable long-life reference, a ceramic junction and an S7 head; an S7–BNC cable connects it to the meter.
How the pH electrode HF acid resistance is built
The long-life reference keeps a steady potential over a longer service time and a wider temperature range than a plain Ag/AgCl reference. It is refilled with 3 M KCl, so the pH electrode HF acid resistance can be kept in service by topping up the electrolyte.
Technical parameters
| Model / order code | PRO6152 |
| Electrode type | pH composite (combination) electrode |
| Measuring range | pH 0 – 14 |
| Working temperature | 0 – 80 °C |
| pH sensor | Hemispherical glass bulb |
| Body material | Glass |
| Reference system | Long-life reference |
| Junction | Ceramic |
| Fill solution | 3 M KCl |
| Temperature sensor | None |
| Dimensions | Φ12 × 120 mm |
| Connector | S7 – BNC (Q9) |
| HF resistance | ≤ 2000 ppm HF |
Full data sheet: Technical Specification (PDF), two pages.
Is this the right electrode for your sample?
The pH electrode HF acid resistance is recommended for: highly concentrated acidic wastewater containing fluorine (≤ 2000 ppm HF).
Some samples need a different design. The selection by sample in the electrode catalogue shows which electrode is recommended for which sample; the most frequent cases are:
- Samples above 80 °C: the high-temperature electrode, specified to 120 °C.
- Pure or low-conductivity water: a low-conductivity or ultrapure-water electrode.
- Emulsions, suspensions, viscous samples: a cleanable or open-junction electrode.
- No refilling wanted: a non-refillable, low-maintenance electrode.
- One sensor instead of two: the 3-in-1 pH composite electrode with a built-in temperature sensor (ATC).
One electrode for benchtop and portable pH meters
The pH electrode HF acid resistance does not belong to one meter. The same electrode works on a benchtop meter in the laboratory and on a portable meter in the field — what decides is the input of the meter, not its housing. With the S7–BNC cable it fits every meter with a BNC input; see the pH meters in the catalogue.
Because the pH electrode HF acid resistance has no temperature sensor, the meter compensates temperature from a separate temperature probe or from a value entered by hand. After moving the electrode to another meter, calibrate again: calibration data are stored in the meter, not in the electrode.
From sample to result
Sampling and keeping the sample
pH is one of the few parameters that cannot be preserved. Carbon dioxide from the air, biological activity and temperature change the value within minutes, so the common water standards ask for measurement on site or as soon as possible after sampling. Take the sample in a clean bottle, fill it to the top without an air space, close it, keep it cool and out of the light, and measure without delay. Do not add any preservative to the portion used for pH.
Preparing the pH electrode HF acid resistance before calibration and measurement
- Remove the protective cap from the sensor bulb at the bottom of the electrode and rinse the tip with distilled water; blot the drops, do not rub — rubbing charges the glass and slows the response.
- Check the electrolyte level; if it is low, top up with 3 M KCl solution.
- Leave the refill hole open during calibration and measurement.
Calibrating the pH electrode HF acid resistance
- Prepare fresh buffers at the same temperature as the samples and start the calibration on the meter.
- Immerse the tip in the first buffer, pH 7.00; wait for a stable reading and confirm the point.
- Rinse the tip with distilled water and blot the drops.
- Immerse the tip in the second buffer (pH 4.01 for acidic samples, pH 10.01 for alkaline); wait for a stable reading and confirm the point.
- The meter shows the electrode slope. If it is outside the limits given in the meter manual, clean the electrode, take fresh buffers and repeat the calibration.
Measuring
Keep the refill hole open while measuring, so the reference electrolyte can flow through the junction, and keep the electrolyte level above the level of the sample. Stir gently or move the electrode slightly, wait for a stable value and read pH together with the temperature. Rinse the tip between samples.
pH in BOD and COD analysis
In a water laboratory the pH electrode HF acid resistance works next to the BOD and COD methods, and both depend on it.
BOD (biochemical oxygen demand) is a biological test: micro-organisms consume oxygen for five days, and they do it properly only near neutral pH. The standard methods therefore require the pH of the sample to be checked before dilution and adjusted to roughly pH 6 – 8 with acid or alkali when it lies outside that range. A wrong pH at the start gives a BOD result that is too low.
COD (chemical oxygen demand) samples that cannot be analysed at once are preserved by acidifying to pH 2 or lower with sulfuric acid and stored cold. The pH check confirms that the preservation worked.
BOD and COD analysers, together with dissolved-oxygen and conductivity meters, are in the electrochemistry catalogue.
Care, storage and accessories
Storing the electrode
Never store the pH electrode HF acid resistance dry and do not keep it in distilled water. Between measurements and overnight, keep the tip in the protective cap filled with 3 M KCl storage solution and close the refill hole. Top up the reference with 3 M KCl filling solution when the level drops.
When the reading is slow or drifts
The usual causes are a membrane that has dried out, a blocked junction, old buffers or a low electrolyte level. Soak the tip in storage solution, top up the 3 M KCl, use fresh buffers and calibrate again.
Accessories
- pH buffers in sachets: single-use portions, always fresh, practical for field work and occasional calibration.
- 3 M KCl solution: for refilling the reference and for storing the electrode.
- S7–BNC (Q9) cable: connects the S7 head of the pH electrode HF acid resistance to the BNC input of the meter.
Video: preparing, using and storing the electrode
The film shows treatment before first use, connecting the pH electrode HF acid resistance to the instrument, rinsing between samples and storage after measurement.
Video: how the electrode holder is installed and used
Buffers, solutions, cables and holders are in the accessories section of the electrochemistry catalogue.
Frequently asked questions
Does the pH electrode HF acid resistance fit my meter?
The pH electrode HF acid resistance fits any meter with a BNC input when it is used with the S7–BNC cable. Meters with another input type need a different cable, so tell us the meter model before you order.
How often should I calibrate the pH electrode HF acid resistance?
For routine work, calibrate at the start of each working day and whenever the sample type or temperature changes noticeably. For occasional measurements, calibrate before each series.
Where can I read more about electrodes?
The electrode catalogue has an electrode guide on sensor shapes, body materials and junctions, a full selection matrix and an overview of connectors. The electrochemistry overview covers pH, conductivity, dissolved oxygen and ion measurement.
