The vintage season is coming. We realise that this is the busiest and most critical period of the year for winemakers.
Here are our recommendations to prepare your wine lab.
1. Restock calibration buffers
pH electrodes should be calibrated before use. Periodic calibration, if not daily, should be performed frequently to obtain a high accuracy of measurement.
Buffers, by definition, should resist change. But over time, an opened bottle will degrade and the pH value on the bottle is not the actual pH value of the solution.
Hanna tip: All buffers that are open for more than six months need to be replaced.
- pH 7.01 buffer (500 ml) – HI7007L
- pH 4.01 buffer (500 ml) – HI7004L
- pH 3.00 buffer (500 ml) – HI5003
2. Stock the right cleaning solution
Electrodes need to be clean to function. With pH probes, stains or coatings on the sensitive glass surface cause a change in potential (voltage) generated by the pH electrode in a solution. You also need to watch for clogging of the junction. Coatings on the glass or clogging of the junction will result in sluggish and erratic readings.
Hanna tip: Use specially formulated cleaning solutions Lab rather than a general purpose cleaning solution.
- Cleaning solution for wine deposits (500 mL) – HI70635L
- Cleaning solution for wine stains (500 mL) – HI70636L
3. Use electrode storage solution
Storage solutions are designed to keep the pH bulb hydrated and to a maintain free flowing junction.
- pH bulb hydration
The hydration of a pH electrode takes 3-4 hours. Without this, the pH calibration significantly will drift over time.
A dry junction inhibits the diffusion of the internal electrolyte. This impacts the junction potential as well as the stability/response of the electrode.
Hanna tip: Properly stored electrodes exhibit higher accuracy and have a longer lifespan.
4. Check the electrode fill levels
Refillable pH or ORP electrodes needed to be topped up with electrolyte when necessary. The fill solution should always be full. This level is needed to provide adequate amount of head pressure. This pressure allows for the flow of electrolyte through the junction into the sample. The ions in the electrolyte complete the electrical measuring circuit between the meter, electrode, and the wine sample being tested.
Hanna tip: Remove the fill cap while testing to ensure electrolyte flow. Replace and tighten the fill cap to preserve electrolyte during storage.
Single junction and double junction electrodes have different fill solutions
Don’t know what kind of electrode you have? The diagram below will help identify what type of electrode that you have.
- Electrode filling solution for double junction electrodes (4 X 30 mL) – HI7082
- Electrode filling solution for single junction electrodes (4 X 30 mL) – HI7071
5. Check that your electrodes are functioning correctly
a. pH Electrodes
Electrodes have a limited lifespan. Remember pH, TA, and Formal Number (Nitrogen) determinations all use a pH electrode. Signs that your electrode may be failing are drifting or that reading takes a long time to stabilise (more than 30 seconds).
Here’s how to check the overall condition of a pH electrode.
You need to check two values. The offset (mV value in pH 7.01) and slope (mV difference between pH 7.01 and pH 4.01). The offset and slope of a pH electrode should be checked with fresh buffers. If your meter has a Good Laboratory Practice (GLP) option then this will provide the data after calibration.
If your meter does not have a GLP option then any meter with a mV mode can be used to check the pH electrode. Here are the instructions for checking slope and offset without GLP mode:
A pH electrode is placed in pH 7.01 buffer the theoretical mV should be 0 mV. Due to variations in the glass, ageing, and conditioning, the offset voltage will differ from 0 mV. An acceptable offset voltage is +/- 30 mV. Most meters will allow calibration at values as high as +/- 60 mV for pH 7.01 buffer, but the accuracy of the measurement will decrease.
The ideal slope for a pH electrode is 100% or 59.16 mV change per pH unit @ 25 ºC. For pH 4, this represents a 177.48 mV difference, since pH 4 buffer is three units away from pH 7 (59.16 mV x 3). The absolute minimum slope for an operable electrode is 85% or 150 mV (177.48 x 0.85).
If the offset and slope values are outside the acceptable ranges, try cleaning and hydrating the probe and then retest. For refillable probes, you can take the additional step of changing the reference fill solution. If the values are still outside the range, replace the probe.
b. ORP Electrodes
SO2 potentiometric Ripper titrations use an ORP electrode for determining the endpoint. It is important to periodically check the ORP electrode using an ORP test solution.
To check an ORP electrode, the probe is placed in an ORP test solution of a known value. HI7021L is a 500 ml bottle of 240 mV @ 25 ºC ORP test solution. A properly functioning electrode will read 240 mV +/- 50 mV. Readings outside this range indicate that the platinum tip/band needs to be polished or the electrolyte fill solution needs to be changed. If the ORP electrode cannot be brought within range then it should be replaced.
Hanna tip: Very fine sandpaper (i.e. 2000 grit) can be used to polish a tarnished ORP tip or band. The ORP sensing portion of the electrode should be shiny and not tarnished.
6. Get some back-up electrodes
Due to the limited lifespan of electrodes, we recommend that you have a back-up electrode in case your electrode fails.
Use specific electrodes designed for wine making where possible. Factors like body type, junction material, type of junction, fill solution, and for pH electrodes the type of glass are all part of the design process. The right mix of materials and technologies significantly improves accuracy, ease-of-use, and the working life of the electrode.
a. Ideal pH electrodes for wine
- Wired electrodes
The HI1048 electrode series is specifically designed for use by winemakers.
CPS Sleeve Junction
CPS™ (Clogging Prevention System) is an innovation in electrode technology. Conventional pH electrodes use ceramic junctions that clog quickly when used in wine. When the junction is clogged, the electrode does not function. CPS™ technology uses the porosity of ground glass coupled with a PTFE sleeve to prevent clogging of the junction. The ground glass allows proper flow of electrolyte, while the PTFE sleeve repels dirt. As a result, pH electrodes with CPS™ function up to 20 times longer than conventional electrodes.
Double Junction Reference
A double junction electrode has an internal compartment surrounding the reference wire. Silver ions are present in the electrolyte of the internal compartment, which houses the Ag/AgCl reference wire; the electrolyte outside this compartment is silver free. The double junction design means that virtually no silver from the electrode enters the sample. This design allows measurement in applications where silver ions in the sample are undesirable or silver precipitates on the junction are likely to form.
The HI1048 is available with a variety of connectors so can be used with a wide range of meters and instruments. Two popular versions are below.
Digital pH Electrode with Clogging Prevention System (CPS™) HI1048B (BNC + Pin connector): This connector is universal and can be used with any meter that has a BNC connector. Use with HI84102 and HI 84502 acidity mini titrator.
Digital pH Electrode with Clogging Prevention System (CPS™) – HI10480 (3.5 mm pin connector): edge digital pH electrodes contain a built-in microchip that stores sensor type, serial number, and calibration information. This includes the date, time, offset, slope, probe condition, and buffers used. The HI10480 has a built in temperature sensor for temperature compensated measurements. This connector is only used with the edge meters.
- Wireless electrodes
The HALO Bluetooth® pH Electrode for Wine (HI10482) offers all the wine specific features of the HI1048 wired electrode but with the convenience of wireless operation.
The HI10482 pairs with the free Hanna Lab app turning your compatible Apple or Android device into a fully featured pH meter.
Features of the Hanna Lab App include:
- Data logging
- Data sharing
The HI10482 offers a great addition to your pH testing analysis toolkit both as a back-up and additional meter for high volume analysis periods.
You can try the Hanna Lab App without a probe in demo mode.
Download the Hanna Lab App today
b. ORP electrode for wine makers
Much like a pH electrode, ORP electrodes also have their own design criteria. Since the ORP electrode is used with the same type of samples in wine testing as a pH electrode, the favourable criteria are similar.
The HI3148 is a double junction, refillable ORP electrode with a platinum ring sensing tip. The HI3148 also has the CPS™ (Clogging Prevention System) technology with the same unique junction made of PTFE as the HI1048 pH electrode.
The HI3148B has a BNC connector and can be used with any titrator that has a BNC input. The HI3148B is supplied with the HI84500 Free and Total Sulphur Dioxide Mini Titrator.
7. Consider purchasing a mini titrator
Hanna’s mini titrators for the wine makers are very popular because of their accuracy, ease-of-use, and affordability with a purchase price below A$1,500. No technical expertise is needed to operate.
Mini titrators are used as the main automated titration system for many wineries as well as back up titrators for high volume periods or as cover for outages with larger systems.
Here’s a few of our wine mini titrators with supporting guides.
HI84533 – Piston-driven syringe Formol Nitrogen Mini Titrator
HI84100 – Original (peristaltic pump) Free and Total SO2 Mini Titrator
Download quick guide for HI84100
HI84102 – Original (peristaltic pump) TA Mini Titrator
Download quick guide for HI84102
HI84100 and HI84102 users should replace old tubing before the season start.
Contact us to ask us about our range of solutions, buffers and reagents.
8. Upgrade to a Digital Refractometer
A well-designed refractometer needs very little maintenance. If you are using a mechanical refractometer then you may want to consider upgrading to a digital refractometer for improved accuracy and ease-of-use.
HI96811 Digital Refractomter for BRIX Analysis measures from 0 to 50% Brix with an accuracy of +/- 0.2% Brix
The HI96813 Digital Refractometeris the same as the HI96811 but also has an algorithm to predict the potential alcohol from the refractive index of the sample. The potential alcohol range is 0 to 25% V/V.
Both meters convert the refractive index of a wine, juice or must sample to % Brix. This conversion is based on the tables found in the ICUMSA Methods Book (International Commission for Uniform Methods of Sugar Analysis) that documents the changes in refractive index with temperature for a percent by weight sucrose solution. Since the majority of sugar in grape juice and must is fructose and glucose instead of sucrose, the reading is sometimes referred to as “apparent Brix”.
Common features for both meters are:
- Reports sugar content as % Brix
- Simple operation with only two buttons: one button is to calibrate with distilled or deionised water and the other to take a measurement
- Sample size as small as two metric drops (about 100 μL)
- All readings are automatically compensated for temperature variations with a 1.5 second response time
- The sealed flint glass prism and stainless steel well are easy to clean – just wipe with a soft cloth in preparation for the next sample
All the best for a successful vintage.
Contact us for more information