APERA INSTRUMENTS / PH700-SA / AI5011

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

The PH700-SA pairs Apera’s PH700 benchtop meter with the Swiss LabSen 843 refillable pH/temperature electrode. Apera’s PH700-SA manual describes the 843 as designed for professional pH measurement of strong alkaline solutions (above pH 12) and high-salinity solutions (above 5 ppt, 5,000 ppm or 0.5%), and notes that it also works well in general water solutions.

Choose AI5011 when the sample chemistry, rather than the meter, decides the electrode. The kit manual gives the 843 a working pH range of 2 to 14 and a 0–100°C temperature rating, and ships the kit with 4.00, 7.00 and 12.45 pH buffers, so the alkaline end can be calibrated close to where you measure.

HA-type glass for strong alkalis

At high pH and high sodium, general-purpose pH glass responds partly to sodium ions and reads low. The LabSen 843 uses a hemispherical HA-type membrane built to minimize that alkaline error. Protect the bulb from impact and keep it hydrated.

Silver-ion-trap reference, ceramic junction

A silver-ion-trap reference keeps silver ions away from the single ceramic junction, which Apera credits with preventing junction clogs. The junction still needs clean samples, rinsing and wet storage.

Refillable, with a built-in temperature sensor

The 843 runs on 3M KCl electrolyte that you top up through the refill hole, and carries a 30K NTC sensor on a separate black RCA plug. Connect both leads so the PH700 shows ATC and compensates automatically.

Where this configuration fits.

Use the PH700-SA for strong alkaline solutions above pH 12 and for brines and process liquids above 0.5% salinity, such as caustic cleaning solutions, alkaline reagents and saline process streams. The 843 also handles ordinary water samples, so one bench setup can cover both.

If the sample is also hot, complex or an electroplating bath, compare the PH700-HT with LabSen 863. For strong acids and fluoride-containing samples, the PH700-HF with LabSen 833 is the matching configuration. Apera’s electrode manual advises against using the 843 in strong acids and dehydrating media such as absolute ethanol and concentrated sulfuric acid.

Calibrate above pH 7.
Then measure a stable sample.

The PH700 takes one to three calibration points, and the first must always be 7.00 pH (6.86 in the NIST series). Apera’s PH700-SA manual walks through a 7.00 / 4.00 / 12.45 three-point calibration, which uses exactly the buffers in this kit. For alkaline-only work, a two-point 7.00 → 12.45 (or 10.01) calibration covers the range above pH 7.

After a two- or three-point calibration the meter shows the electrode slope for the acid and alkaline ranges; the closer to 100%, the healthier the electrode. Apera requires recalibration after measuring strongly alkaline (pH above 12.00) samples, so plan for it between caustic runs.

Strong bases absorb carbon dioxide from air and drift downward, so keep the 12.45 buffer and your samples capped and measure promptly. Strong alkali is corrosive: wear eye and skin protection.

Set up the bench.
Connect pH and temperature.

Screw the metal stand base to either side of the meter, fit the supporting bar, then the electrode clip. Plug the 9V adapter into the DC9V socket, clip the electrode into the holder, and connect the blue BNC plug to pH/mV and the black RCA plug to TEMP. The banana REF socket is for a separate reference electrode and is not used with this combination electrode.

To prepare the electrode, loosen the locking ring on the storage vial, pull the electrode out slowly, rinse it with pure water and blot it dry. Never rub the glass membrane. Before measuring or calibrating, open the blue rubber stopper on the 843’s refill hole so electrolyte flows smoothly, and close it again when you finish. Run at least a two-point calibration before first use.

Read the meter.
Save the readings you need.

Wait for the stable-reading smiley to appear and stay before you record a value or confirm a calibration point. Short-press M+ to save a stable reading; long-press RM to recall saved data. The PH700 stores 50 sets in total across pH and mV, each with its number, value, unit, temperature and compensation status. When memory is full the meter shows FUL; clear it in parameter P4.

MAX/MIN mode tracks the highest and lowest readings since you entered it. The meter has no documented USB or PC export, so transcribe saved values into your own records. If a calibration fails, the Er codes on screen point to the cause in Apera’s troubleshooting guide.

Four sockets, labeled.
One for each job.

The rear panel carries a Φ2 banana REF socket for a separate reference electrode, a BNC pH/mV socket for pH and ORP electrodes, an RCA TEMP socket for the temperature sensor and a Φ2.5 DC9V power socket. Fit the connector cap whenever no electrode is connected to keep the BNC clean and the readings steady.

Press MODE to switch to mV. With a pH electrode connected, mV shows the electrode’s raw potential; with an ORP electrode such as Apera’s 301Pt-C, the PH700 reads ORP directly.

Refill with 3M KCl.
Store the glass wet.

Store the electrode in its vial with 3M KCl soaking solution and twist the locking ring tight. Replace the solution if it becomes contaminated, and as a rule of thumb once a month. White KCl crystals on the outside of the vial are normal; rinse them off.

Never store the electrode in tap, RO, distilled or deionized water. If it happens, soak it overnight in 3M KCl and recalibrate before use.

When the electrolyte drops below half the glass tube, open the blue stopper and use a syringe to add 3M KCl (Apera AI1107) to about one inch below the refill hole. Apera puts typical pH-electrode life at one to two years. The replacement electrode is LabSen 843, AI3179.

Clean for the contaminant.
Then rehydrate and recalibrate.

Rinse with distilled or deionized water before and after every measurement, and blot rather than wipe. For deposits that rinsing does not remove, Apera’s table matches the cleaning agent and soak time to the contaminant: dish soap water for oils and fats, Apera cleaning solution AI1166 for proteins, scale and unknown residues, 0.1M NaOH for acidic coatings, thiourea for sulfide staining.

Use a soft brush where needed. After any cleaning, soak the electrode in 3M KCl for 12–24 hours to rehydrate it, then recalibrate before measuring.

Where the electrode sits
in Apera’s range.

Apera’s application guide assigns the LabSen 841/843 to high-salinity and strong alkaline solutions. The same PH700 meter accepts any BNC/RCA LabSen electrode, so a lab that later needs a different sample type can swap the electrode rather than the meter.

Every pH electrode ages; Apera recommends replacing yours at least every one to two years, depending on use, samples and maintenance.

Check the meter limits.
Then the electrode’s.

The PH700 displays 0 to 14.00 pH at 0.01 or 0.1 resolution with ±0.01 pH ±1 digit accuracy, −1999 to 1999 mV at 1 mV (±0.1% F.S.), and temperature from 0 to 100°C at 0.1°C (±0.5°C), with automatic or manual compensation from 0 to 100°C. It runs on a DC 9V/300 mA adapter, carries an IP54 dustproof and spillproof rating, and measures 240 × 235 × 103 mm at 1 kg.

The supplied LabSen 843 sets the practical limits: 2–14 pH and 0–100°C per the PH700-SA manual. Confirm unusual chemistries against Apera’s documentation before measuring.