HI 410 CARB ON DIO XIDE 5 Instruction Manual HI 4105 Carbon Dioxide Ion Selective Electrode 1
HI 4105 Carbon Dioxide Electrode I. Introduction: The Hanna HI 4105 Carbon Dioxide gas sensing electrode is a combination electrode designed for the measurement of Carbon Dioxide in aqueous solutions such as water, soft drinks or wine, samples. Carbonate and Bicarbonate ions are also measured by conversion to Carbon Dioxide gas upon ISA addition. II. Specifications Type: CO2 gas sensing electrode with glass pH internal, Ag/ AgCl reference and gas permeable membrane.
III. Theory of Operation Operation:: The Carbon Dioxide electrode is a complete potentiometric cell that contains both a silver/silver chloride (Ag/AgCl) reference and a pH measurement element. These elements are housed within a thermoplastic body in a chloride ioncontaining electrolyte, and are isolated from the sample by a PTFE membrane. ISA addition changes the pH of the sample to approximately 4.7 pH and Bicarbonate (HCO3-) and carbonate (CO32-) ions in the sample are converted to carbon dioxide (CO2).
IV. Design Elements The Hanna HI 4105 Carbon Dioxide gas sensor has 3 main parts. These are the membrane/membrane cap, outer probe body with antirotation key and the pH/reference assembly which includes the outer electrode cap, spring, inner cap and pH/reference electrode assembly.
V. Equipment Required: • Hanna HI 4222 pH/ISE/mV meter or other suitable ion or pH/mV meter. (Note: log/linear graph paper is useful if an ISE meter is not available). • Hanna HI 180 magnetic stirrer or equivalent with stirring bars. (Note: Isolate beakers from stirrer motor heat by placing insulating material such as foam or cork between them).
VII VII. General Guidelines • Calibration standards and sample solutions should have the same ionic strength. ISA should be added to both samples and standards immediately before taking measurements. • Calibration standards and sample solutions should be stirred at the same rate using identical sized stir bars. Stir thoroughly and continuously. • Calibration standards and sample solutions should be at the same temperature.
VIII. Inner Electrode Check Prior to assembling the electrode for the first time or subsquently reactivating it after extended periods of dry storage, the inner electrode assembly should be hydrated and then tested as a pH electrode. Prepare pH test solutions HI 4000-47-4 and HI 4000-477 by mixing and dissolving each buffer packet in separate containers with 50 mL deionized water.
• If sensor has been stored or shipped dry, it should be “conditioned” by soaking the pH/reference assembly 1 hour or more in one of the pH test solutions. • Avoid touching the pH glass with your fingers. • Attention: The pH/reference assembly is fragile! Support the upper portion of the internal cell while immersing the glass and reference assembly. A tall narrow container with weighted bottom is best. The pH test solution should cover the bottom of the large black band.
IX. Electrode Preparation 1) Remove glass internal from sensor body and perform inner electrode check. (See section VIII). 2) The HI 4105 sensor comes with three easily replaceable membrane caps (two which are spares). Remove a cap from membrane box and screw on to lower threads of outer probe body, compressing the o-ring seal. Avoid touching working area of membrane with your fingers as skin oil will change the membrane properties. 3.
4) Insert and position the inner glass/reference assembly into the outer body so that the anti-rotation key sits in the cut out on the outer probe body. CARBON DIOXIDE HI 4105 CARBON DIOXIDE HI 4105 5) Holding the electrode upright, slide spring and electrode cap down cable and screw cap on outer body until fully engaged. Do not invert electrode. Do not overtighten. 6) Install assembled electrode in gas sensor test vessel or in electrode holder and connect cable connector to pH/mV meter.
X. Quick Check of Electrode Slope • Connect BNC (connector) to pH/mV/ISE meter. • Place meter in mV mode. • Place 100 mL of deionized water into a vessel with stir bar. Add 10 mL of ISA Hanna HI 4005-00. • Place sensor into prepared sample. • Add 1 mL of 1000 ppm or 0.1 M Carbon dioxide standard to beaker and stir sample. Wait approximately 5 minutes. Record the mV value when stable. • Add an additional 10 mL of standard to the solution. Record the mV when reading has stabilized (approximately 5 minutes).
XII. Sample Handling • For optimum results, allow samples and standards and the HI 4105 electrode to reach the same temperature. • As CO2 is volatile, measure samples immediately after collection. • If sample must be stored: Completely fill collection bottle with dilute samples and tightly cap container to prevent carbon dioxide loss or contamination from other sources. • If sample must be stored: For acetic samples. add sodium hydroxide (10N) to raise pH to 8-9 for storage. Tightly close collection bottle.
XIII. Direct Calibration and Measurement The direct measurement method is best used in the linear working regions of the sensor. (See figure for typical sensor response) and can be used when measuring many samples. A direct reading ISE meter (HI 4222 or equivalent) determines concentration of the unknown by a direct reading after calibrating the meter with the standards. The meter is calibrated with two or more freshly made standards that are in the measurement range of the unknowns.
• Standards and solutions should be at the same temperature. 10 mL of ISA is added to each 100 mL of sample and standard. Protect these solutions from loss of dissolved gas by covering and using promptly. Follow section VII; General Guidelines to optimize test set-up. During calibration it is best to start with lower concentration samples first. Wait for a stable reading before reading/recording values (approximately 5 minutes).
XIV echniques XIV.. Other Measurement TTechniques Known Addition An unknown concentration of carbon dioxide can be determined by adding a known amount (volume and concentration) of carbon dioxide standard to a known volume of the sample. This technique is extremely useful for carbon dioxide because changes in the sensor calibration are corrected for continuously because, the standard and sample are measured within minutes of one another.
7. The procedure can be repeated with a second standard addition to verify slope and operation of the method. Note: This method is preprogrammed in the Hanna HI 4222pH/ISE/mV meter, which simplifies the method greatly and permits repeated determinations easily. Example: Carbon Dioxide determination with known addition: 1. A 50 mL sample of unknown (VSAMPLE) is placed in an clean vessel with an electrode. 5 mL of ISA is added to the sample .
XV. Storage and Care of the HI 4105 sensor The HI 4105 sensor can be stored assembled and ready to use in HI 4005-45 Conditioning solution overnight or between measurements. After overnight storage, gently pull on the cable to compress the spring mechanism thus permitting electrolyte to exchange from the bulk to the thin film between the membrane and glass. Calibration is required after doing this.
XVII. HI 4105 AAccessories ccessories and Replacement PParts arts For Calibration : Code HI 4005-00 Ionic Strength Adjuster (500 mL) HI 4005-01 HI 4005-03* Hanna 0.
MAN4105 07/06 REV1 WARRANTY Hanna Instruments Ion Selective Electrodes are warranted to be free of defects in material and workmanship for 6 months from date of purchase when used for their intended purpose and maintained according to instructions. If they fail to work when first used contact your dealer immediately. Damage due to accidents, misuse, misapplication, tampering or lack of prescribed maintenance is not covered.