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Applications advice and testing methods are an ever-growing resources. As a guide, you'll find Ionode sensors suit most applications and can be sold with complete confidence.
Method –acid/base titration
Sensor – IJ-44A
acidity in wine, juice, soft drinks, mustard, mayonnaise, milk, edible oils, vinegar, cheese, plating baths & TAN (total acid number)of new and used oils
Method –acid/base titration
Sensor – IJ-44A
alkalinity in potable water, cleaning baths & TBN (Total base Number) of new & used oils
CHLORIDE by titration
Method –precipitation titration (argentimetry) using silver nitrate
Sensor – IJ-Ag
chlorides in mineral water, food products, water, and butter
CHLORIDE by ISE
Method –direct potentiometry using Ion selective electrodes
Sensor – IJ-Cl
chlorides in mineral water, food products & water
Method – Redox titration using titrants such as Iodine, sodium thiosulphate & permanganate
Sensor – IJ-64
determination of copper in electroplating baths, determination of hydrogen peroxide, Vitamin C in juice, Iodine value of animal & vegetable Fats and Oils, and Peroxide value of edible oils
Other Applications include:
Carbon dioxide in wine using IJ-44A
Cyanide in water using either IJ-Ag (titration) or direct with IJ-CN ISE
Iodide in milk using IJ-I
Bromide in water using IJ-Br
Fluoride in drinking water, mouthwash, environmental samples, vegetation and toothpaste using IJ-F
Other applications include:
Aluminium Ions Using a Fluoride ISE, Bromide in Water, Cadmium using a Silver ISE, Calcium in Animal Foodstuffs, Calcium in Fruit Juice, Calcium in Beer, Calcium in Meat Products, Calcium in Seawater, Calcium in Serum, Calcium in Skimmed Milk, Calcium in Soil, Calcium in Urine, Chloride in Batter Mix and Sausage Rusk, Chloride in Butter, Chloride in Potato Starch Suspension, Chloride in Fruit Juice, Chloride in Mayonnaise, Chloride in Serum, Chloride in Urine, Chloride in Water, Cyanide (General), Cyanide in the Presence of Heavy Metal Ions, Cyanide in Water, Fluoride in Glass, Fluoride in Urine, Fluoride in Drinking Water, Fluoride in Water, Fluoride in Welding Ash Solution, Fluoride in Vegetation, Iodide in Water, Kjeldahl Nitrogen in Water, Nitrate in Liquor used for Beer Preparation, Nitrate in Plant Tissue, Nitrate in Soils, Nitrate in Water, Phosphate Using a Fluoride ISE, Potassium in Fruit Juice, Potassium in Glass, Potassium in Oral Rehydration Salts, Potassium in Pharmaceutical Syrup, Potassium in Soils, Potassium in Water, Potassium in Wine, Silver in Fixer Solutions, Silver in Fixer Solutions II, Sodium in Dietetic Food, Sodium in Glass, Sodium in Oral Rehydration Salts, Sodium in Peanut Butter, Sodium in Pharmaceutical Syrup, Sodium in Serum, Sodium in Water, Sulphate by Sample Subtraction, Sulphide in Water ...
pH and Lubricating Oils
pH is an index of the concentration of Hydrogen Ion (H +) in water. Since oil is not an ionizing solvent, it has no free hydrogen ions and therefore, it does not have a pH per se. If the oil contains materials which when mixed with water supply hydrogen ions to the water phase, then these will register when the pH of the water phase is measured.
Due to dissociation pure water has a pH of 7. The hydrogen ion (H +) concentration in pure water is 1E-7 (pH 7) and the hydroxide ion (OH -) concentration is also 1E-7. Each molecule of H 2O that dissociates produces one of each ion, (HOH H + + OH -). The H + is the acid ion and the OH - is the base ion. Since they are present in pure water in equal concentrations, then the water is “neutral” pH 7.
The fraction ionized is about 0.0000001 (=1E-7) at 22°C; i.e., 10,000,000 liters of water supplies 1 gram- ion of hydrogen. [DEF: The pH value is the logarithm of the number of liters of a solution which must be taken in order to contain one gram ion of hydrogen].
Since this is a reciprocal relationship, raising the hydrogen ion concentration lowers the pH value and vice versa.
1/10,000,000 = 1E-7
pH does not tell us how much total acidic hydrogen is present in a combined of un-ionized form. To determine the concentration of acidic hydrogen we refer to the acid number test. If either ion (H +/ OH -) is present in excess of the other, the excess amount can be found by measuring how much of the other ion is required to bring the system back to neutral.
But what is “neutral” in lubrication oil? As discussed, pure water is neutral at pH 7. Equivalent amounts of “strong” acids and “strong” bases mixed together are neutral at pH 7.
This is because strong acids and strong bases release essentially all (over 90%) of their H + and OH - ions respectively when diluted with water. However, in most lubricating oil systems we are dealing with “weak” acids and bases. Weak acids or bases ionize or release their H + and OH - reluctantly, on the order of 1%, 0.01% or less, at equilibrium.
All of these systems are in dynamic equilibria. Systems at equilibrium with pH 7 are “neutral” in that the concentration of the hydrogen ions (H +) and the hydroxide ions (OH -) are equal. If the equilibrium is shifted either of both ions may be available depending on what other materials may be present. You could say, “pH is characteristic of a particular oil,” but remember that the pH is measured in and refers to what is in the water phase only. It is generally accepted that new unused turbine oil will have a pH of about 7. Slightly higher or lower pH values may be encountered depending on those materials (additives), which are present.
Acid Numbers and Lubricating Oils
As discussed, used lubricating oils may contain a combination of strong and weak acid formations.
Determining the concentration of strong acids: Titration with a strong base (specifically KOH) will begin at a pH of less than 4.2 and produce a Strong Acid Number (SAN) at an end point of about pH 4.2.
Determining the concentration of weak acids: Titration with a strong base will begin at a pH above 4.2 and produce an Acid Number at an end point of about pH 11.
In the case of the strong acid titration we add only enough base (OH -) to shift the equilibrium up to pH 4.2. In the case of a weak acid titration we add just enough base to shift the equilibrium from some point above 4.2 to a pH of about 11.
Total Acid Numbers (TAN): It follows then, that if both strong and weak acids are present, the Acid Number (commonly referred to as Total Acid Number, TAN) for the system is obtained by titrating to pH 11. The amounts of each type of acid can be obtained by noting the amount of KOH used to reach pH 4.2 for the strong acids and the incremental amount of KOH added between pH 4.2 a pH 11 for the weak acids. These may be recorded as Strong Acid Number and Weak Acid Number respectively with the TAN being the sum of the two.
Acidity in Cheese
As the acidity of cheese has a major influence on the taste of the product, this parameter is used to test the quality.
The acidity of cheese is determined by end point titration using 0.1 eq/l NaOH. The end point value is generally fixed at pH 8.4 and the result is expressed in % of lactic acid, which has a MW of 90.08 g/mol.
Electrode and reagents
IJ-44 pH electrode
NaOH 0.1 eq/l solution in distilled water
pH 4.00 buffer or pH 7.00 buffer and pH 10.0 buffer
End Point titration settings
Burette volume: 10 ml
Stirring speed: 400 rpm
Working mode: pH
Number of end points: 1
End point: 8.40 pH
Stirring delay: 30 seconds
Minimum speed: 0.2 ml/min
Maximum speed: 10 ml/min
Proportional band: 4.00 pH
End point delay: 5 seconds
Titration: Increasing pH
Sample unit: g
Sample amount: see below
Sample preparation Place a known amount of cheese (generally between 10 and 20 g) in a 250 ml beaker, add
100 ml of distilled water at 40°C and homogenize with a high speed homogenizer. Filter or centrifuge according to particular recommendations and dilute to 250 ml using a volumetric flask. Titrate an aliquot of 25 or 50 ml for example.
1/ Calibrate the combined pH electrode using the 2 IUPAC standards above.
2/ Pipette 25 or 50 ml of sample.
3/ Dip electrode and delivery tip in the solution.
4/ Start method.
Expressed as % of lactic acid (CH3?CHOH?COOH with a MW of 90.08 g/mol)
As in this case 1 molecule of titrant reacts with 1 molecule of lactic acid
R = V(titr) * C(titr) * 90.08 * 100 * F /1000 * W(smp)
?V(titr) = total volume of titrant to reach the end point in ml ?C(titr) = Titrant concentration in eq/l (currently 0.1) ?W(smp = sample amount in g
90.08 = Molecular weight of lactic acid
F = Dilution factor between total volume and aliquot 100 = Factor needed for a result expressed in %.
pH is a fundamental element of the wine-making industry and strongly influences wine properties such as color, oxidation, biological and chemical stability. The IJ Koala series electrodes are accurate and reliable tools for measuring wine parameters.
pH measures the quantity of acids present, the strength of the acids, and the effects of minerals and other ingredients in the wine. Wine pH depends on three main factors: the total amount of acid present, the ratio of malic acid to tartaric acid, and the amount of potassium present. Wines that contain little acid and excess potassium show high pH values. Wine with more tartaric acid, less malic acid, less potassium and more titratable acid has lower pH values.
pH values range from 2.9 to 4.2 in wine. Wine’s chemical and biological stability are very dependent on pH value. Lower pH values are known to improve the stability, so winemakers usually prefer a pH range of 3.0 to 3.5. The wine is so stable in this range that many winemakers believe pH is a crucial guideline in wine making.
There are many advantages to low pH values in wine. Low pH inhibits bacteria, causes sugar fermentation to progress more evenly and makes malolactic fermentation easier to control. Low pH also has a direct influence on the hot stability of wine. When bottled wines are stored in warm areas, protein precipitates out of them, causing serious problems. These wines are then treated with bentonite, which removes excess protein. pH is important to the treatment because bentonite successfully removes more protein when the pH value is low. If wine pH increases, bentonite is less effective, making it necessary to add larger amounts. The danger is adding too much bentonite because it can strip wines of their unique aromas and flavors.
An example of the importance of low pH is displayed with Sauvignon Blanc. Sauvignon Blanc grapes normally have large amounts of protein, so they can be difficult to sufficiently stabilize when pH values are too high.
Low wine pH results in better visual qualities as well. When pH is lower, both red and white wines maintain better color intensity. Red wines have more and better color and white wines do not brown as easily.
When wine has high pH values, bacteria grow rapidly and undesirable bacterial fermentation is more problematic. This condition causes less biological and chemical stability, and poorer color. Wines with a high pH always need more attention and greater care.
Refer to the table below as to the effects of pH levels on wine quality:
|Wine Characteristic||Low pH Range (3.0-3.4)||High pH Range (3.6-4.0)|
|Amount of color||More||Less|
|Kind of color||Ruby||Browner|
|Protein Stability||More stable||Less Stable|
Use IJ-44 pH electrode for rugged and easy-clean performance.
Yogurt is a popular dairy product made from concentrated milk fermentation. The quality of the product depends on production control of lactic acid formed by fermentation. Lactic acid provides the tart flavor and the destabilization of milk protein forms the gel structure. pH measurement monitors lactic acid production and aids in the quality control of yogurt’s ingredients.
The production of yogurt starts by selecting and blending the correct ingredients, like milk concentrate and other dairy products, thickening agents, sweeteners and fruit. These ingredients add the correct solids, flavor and viscosity. The blend of ingredients is homogenized at high pressures to prevent fat separation and cause solid dispersion. Next, the temperature is raised to destroy harmful microorganisms and restructure protein to help with the viscosity. After cooling, the smarter culture, which contains a particular lactic fermentation bacteria, is added to the mix. Incubation then takes between 4 and 11 hours.
During fermentation, lactose (milk sugar) converts to lactic acid, decreasing the pH values to a range of 4.25 to 4.5. Bacterial action is stopped by rapid cooling at the right lactic acid level. pH meters are the best instrumentation to determine the completion time of fermentation. Incorrect pH levels can lead to discoloration, excessive free whey and excess or insufficient tartness.
Perform the test on sample by putting the probe in the sample, gently stirring for a few moments to be sure no air bubble is trapped on the sensor surface.
Note: In 0.01 resolution, the endpoint time is about twice that of the 0.1 resolution. If you don’t need 0.01 precision, put the meter in 0.1 resolution to speed response time. This research grade resolution is not required in most dairy applications. Be sure not to use 0.001 resolution or unnecessary time will be spent reaching an endpoint reading.
Rinse probe with a jet of distilled or de-ionized water from a right angle squirt bottle. Alternatively, you can remove the reference sleeve, clean the reference tube and reference area around the glass. Add a bead of electrolyte at the base of the glass and slide the reference tube back onto the probe. Ready to go!
Protein is the biggest single problem in pH testing of dairy applications. In glass electrodes it gets in the glass and is very difficult to remove. We recommend HCl acid dips or pepsin solutions. The best approach is a 2 minute soak in 0.1M HCl. After this soak, use a gentle rub of the sensor surface with a soft cloth. Rinse well, then recalibrate. It is not necessary to use this method unless response time slows.
• Replace the soaker sleeve over the pH electrode tip with a small amount of pH 4 buffer or a storage solution.
• Remove the bottle by reversing the sequence.
The best storage solution is pH 4 buffer solution saturated with KCL. The pH 4 solution is acidic, and will eat away most fouling of the pH electrode. Additional solution, if required, may be made using commercially available buffer capsules, KCL crystals, and distilled water. The sensor will tolerate the periodic absence of the soaker bottle and can be returned to initial performance by soaking for a few hours. However, exposure of the bare sensor to temperature extremes (e.g., strong direct sunlight on a hot day) can cause a loss of internal electrolyte. Subsequent cooling will draw air into the sensor, which will lead to pressure-related problems.
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