APERA INSTRUMENTS / PH700-HF / AI5013

Strong acid and HF on the bench.
Start with HF-resistant glass.

The PH700-HF pairs Apera’s PH700 benchtop meter with the Swiss LabSen 833 refillable pH/temperature electrode. Apera’s PH700-HF manual describes the 833 as designed for accurate measurement in strong acidic solutions and resistant to hydrofluoric acid corrosion, good for up to 1,000 measurements when each lasts under one minute and the HF concentration stays below 0.1 mol/L (0.2 wt%).

Choose AI5013 when the sample chemistry, rather than the meter, decides the electrode. The kit manual lists the LabSen 833 at 0–12 pH and 0–100°C and ships the kit with 1.68, 7.00 and 10.01 pH buffers, so the acid side can be calibrated low. The HF rating is a measuring allowance with limits, not immunity: Apera asks for spot sample tests, not continuous immersion.

HF-type glass for strong acids

Ordinary pH glass is attacked by hydrofluoric acid and ages quickly in strong acids. The LabSen 833 uses a hemispherical HF-type membrane that Apera rates for up to 1,000 measurements in HF below 0.1 mol/L when each test lasts under a minute. It is still glass: rinse promptly and protect it from impact.

Silver-ion-trap reference, ceramic junction

A silver-ion-trap reference keeps silver ions away from the single ceramic junction, which Apera describes as improving stability and service life. The junction still needs clean samples, rinsing and wet storage.

Refillable, with a built-in temperature sensor

The 833 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-HF for strong acid solutions and for samples that contain hydrofluoric acid up to 0.1 mol/L (0.2 wt%, 2,000 ppm), measured as spot tests of no more than one minute each. Apera’s kit manual warns that longer or more concentrated exposure wears the electrode much faster than usual.

Measure HF-containing samples in a PTFE container, never glass. For strong alkaline or high-salinity samples, compare the PH700-SA with LabSen 843; for hot, complex or electroplating baths, the PH700-HT with LabSen 863 is the matching configuration. Apera’s electrode manual advises against using the 833 in strong alkaline solutions and dehydrating media such as absolute ethanol and concentrated sulfuric acid.

Calibrate below pH 7.
Then measure quickly and rinse.

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-HF manual walks through a 7.00 / 1.68 / 10.01 three-point calibration, which uses exactly the buffers in this kit. For acid-only work, a two-point 7.00 → 1.68 (or 4.00) calibration covers the range below 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 acidic (pH below 2.00) samples and after fluoride-containing solutions, so plan to recalibrate between HF runs.

Hydrofluoric acid is a serious contact hazard. Follow your site’s HF procedures and PPE, keep each immersion inside Apera’s one-minute limit, and rinse the electrode immediately afterward.

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 833’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; HF work consumes the membrane faster. The replacement electrode is LabSen 833, AI3177.

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 831/833 to strong acid solutions and HF-containing solutions below 2,000 ppm HF. 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 833 sets the practical limits: 0–12 pH and 0–100°C per the PH700-HF manual. Confirm unusual chemistries against Apera’s documentation before measuring.