The HI84500 can be used to test for free and total SO2 in all wines, including red, which are difficult to test using traditional methods due to the inability to see the distinctive color change that occurs at the endpoint. The HI84500 offers a reliable, accurate, and fast way to analyze free and total sulfur dioxide. This mini titrator dispenses the titrant, detects the endpoint, and performs all necessary calculations automatically in a fraction of the time as compared to a manual titration.
Winemakers add sulfur dioxide (SO2) to wine in order to inhibit bacteria and wild yeast growth and to serve as an antioxidant to prevent browning. When SO2 is added to wine, a portion of it becomes immediately bound while a remaining portion is unbound SO2. The portion that is unbound is also called free SO2 and it is responsible for protecting the wine. The bound and free SO2 together are referred to as total SO2. The relationship between the amount of SO2 added and the amount of free SO2 is complex, governed by the total amount of SO2 in the wine and the ability of compounds (e.g. sugars, aldehydes, keto acids, quinones, anthocyanin) to bind to the SO2. The exact relationship between free and bound SO2 will vary from wine to wine.
The amount of free SO2 depends on how much is added, how much was present before the addition, and how much was immediately bound. Free SO2 exists in two forms. The first form, bisulfite (HSO3-), is the predominant form but is relatively ineffective. The second form, molecular SO2, is the minor form and is responsible for protecting the wine. The amount of molecular SO2 available in wine is dependent upon the amount of free SO2 present and the pH. Typically 0.8 ppm of molecular SO2 provides adequate protection against bacteria growth and oxidation. In order to obtain this value for a wine sample that has a pH of 3.2 you would need 22 ppm of free SO2. If the pH was at 3.5 you would need double the amount of free SO2, 44 ppm.
Application-Specific ORP Electrode The HI84500 is supplied with the HI3148B ORP electrode featuring CPS™ technology to prevent the clogging of the reference junction. Conventional electrodes may clog quickly in samples such as wine that have a high suspended solids content. By design, the HI3148B ORP electrode utilizes a ground glass/PTFE sleeve junction which controls a steady, predictable flow of electrolyte solution, keeping the junction open. The hydrophobic properties of PTFE repel wetness and coatings.
Piston Driven Dosing Pump The heart of the HI84500 is the piston driven burette pump. This type of dosing system uses a motor in which each dose is very precisely controlled and the volume dispensed is accurately determined. The piston driven burette is controlled dynamically so that the volume of titrant being dosed is automatically adjusted based on a voltage response of the previous dose. This type of dosing speeds up the titration process by allowing for more titrant to be dosed at the start of the titration and then very small doses as the endpoint is reached.
Automatic Stirrer The built-in stirrer is automatically maintained at a speed of 700 rpm, regardless of the viscosity of the solution being titrated.
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