APERA INSTRUMENTS / PH8500-SA / AI5523

Strong alkali and high salinity.
Start with the right glass.

The PH8500-SA pairs Apera’s portable, USB-enabled PH8500 meter with the Swiss LabSen 843 refillable pH/temperature electrode. Apera designs the 843 for high-precision pH measurement of strong alkaline solutions (pH 10–14) and high-salinity solutions, using an HA-type glass membrane to minimize alkaline error and a silver-ion-trap reference to prevent junction clogs.

Choose AI5523 when the sample chemistry, rather than portability alone, decides the electrode. Apera lists the supplied LabSen 843 at 2–14 pH and 0–100°C for this kit. Those are the electrode’s working limits, not the meter’s wider −2.00 to 16.00 pH display range. Automatic temperature compensation corrects the electrode response; it does not stop a caustic sample from absorbing carbon dioxide from air.

HA-type glass for strong alkalis

Ordinary pH glass responds partly to sodium ions at high pH, so readings drift low. Apera specifies an HA-type membrane on the LabSen 843 to minimize that alkaline error in pH 10–14 samples. The membrane is a hemispherical bulb; protect it from impact and keep it hydrated.

Silver-ion-trap reference, ceramic junction

The reference system traps silver ions before they reach the ceramic junction, which Apera describes as preventing junction clogs. The junction still needs clean samples, rinsing and wet storage; a protected reference does not make the junction maintenance-free.

Refillable, with a built-in temperature sensor

The 843 uses 3M KCl reference solution that you top up through the refill hole, and a 30 kΩ NTC sensor wired to a separate RCA plug. Connect both the BNC and RCA leads so the PH8500 can display sample temperature and apply automatic compensation.

Where this configuration fits.

Use the PH8500-SA for strong alkaline solutions in the pH 10–14 region and for high-salinity samples where a general-purpose electrode is likely to read low. Typical examples are caustic cleaning and process solutions, alkaline reagents and brines, measured within the electrode’s 2–14 pH and 0–100°C limits.

If the sample is also hot, complex or an electroplating bath, compare the PH8500-HT with LabSen 863. For strong acids and fluoride-containing samples, the PH8500-HF with LabSen 833 is the matching configuration. Apera’s manual advises against using the 843 in strong acids and dehydrating media such as absolute ethanol or concentrated sulfuric acid.

Calibrate above pH 7.
Then measure a stable sample.

Connect the electrode’s BNC plug to the pH input and the black RCA plug to the temperature input. Twist off the storage bottle cap, pull out the electrode, rinse it with distilled or deionized water and open the blue rubber plug on the refill hole so the reference solution flows smoothly.

Apera specifies at least a two-point calibration before a new electrode is used. The PH8500 always starts at 7.00 pH (6.86 pH in the NIST series). For alkaline work, the manual’s Option B adds 10.01 pH or 12.45 pH as the second point, and a three-point calibration can use 4.00, 7.00 and 10.01 or 12.45 pH. The kit supplies 4.00, 7.00 and 10.01 pH; add 12.45 pH buffer when your samples sit near the top of the range.

Immerse the bulb and junction, stir gently and wait for the stability icon before saving. Strong bases absorb carbon dioxide from air and drift downward, so keep samples covered and measure promptly. Strong alkali is corrosive: wear eye and skin protection.

Refill with 3M KCl.
Store the glass wet.

When the electrode is not in use, keep it in the storage bottle with 3M KCl soaking solution (Apera AI1107). Replace the solution if it becomes contaminated. Distilled and deionized water are rinse liquids, not storage liquids; never store the 843 in pure water.

The reference solution runs down with use. When it falls to about half the electrode height, unplug the blue rubber plug and add 3M KCl through the refill hole with a syringe or pipette. After measuring, return the electrode to its bottle, tighten the cap and close the refill hole.

Keep the BNC and RCA connectors clean and dry. Apera puts typical pH-electrode service life at 12–24 months and recommends replacement every 12–18 months; frequent strong-alkali work sits at the demanding end of that range. The replacement electrode is LabSen 843, AI3179.

Read the meter.
Know what is held.

Use the physical controls for standalone measurement and calibration. The stable-reading indicator and HOLD help you read a result; a held display is not a stored record.

The PH8500 measures −2.00 to 16.00 pH at 0.01 or 0.1 pH resolution with ±0.01 pH ±1 digit accuracy, mV from −1999 to 1999, and temperature from −5 to 100°C. A calibration reminder can be set in days or hours. The meter runs on three AA batteries or 5 V USB power and carries an IP57 rating.

Build a local record.
Keep the transfer workflow clear.

The PH8500 can retain up to 500 data sets, including number, date, time, measured value, unit and temperature. M+ saves a reading manually after stability, and timed logging records automatically at the interval you set. Deleting stored data cannot be undone.

For computer work, connect the supplied USB cable and use PC-Link or the browser-based Web PC-Link on a desktop Chrome or Edge browser under Windows or Mac to download records and export them. While connected to PC-Link, new readings go to the software rather than to meter memory, so export before closing the session.

Check the electrode limits.
Then the meter’s.

Apera lists the LabSen 843 in this kit at 2–14 pH and 0–100°C, with an HA hemispherical membrane, ceramic junction, silver-ion-trap reference, 3M KCl electrolyte, 30 kΩ NTC temperature sensor, lead-free glass body (Ø12 × 120 mm), membrane resistance below 500 MΩ, a 1 m cable and BNC plus RCA connectors.

The meter’s automatic temperature compensation covers 0–100°C. Keep samples, buffers and the electrode within those limits, and confirm suitability with Apera’s documentation before measuring unusual chemistries.