HI 4112 LEAD/SULFATE COMBINATION LEAD/SULFATE HI 4012 Instruction Manual HI 4012 HI 4112 Half-cell Combination Lead Ion Selective Electrode 1
HI 4012 Lead Half-cell HI 4112 Lead Combination Electrode I. Introduction: The Hanna HI 4012 and HI 4112 are ion selective electrodes designed for the measurement of Lead ions in aqueous solutions. The HI 4012 is a solid state half-cell sensor that requires a separate reference. The HI 4112 is a combination ion selective electrode. IIII. Specifications Type: Solid State electrode with a lead sulfide pellet. +2 Lead (Pb ) Ion(s) measured: 0.1 M to 1X 10-6 M 20700 to 0.
III. Theory of Operation Operation:: The HI 4012 or HI 4112 lead electrodes are potentiometric devices used for the rapid determination of free lead ions in plating baths and as a detector for the titration of sulfate or thorium with lead perchlorate. Lead sensors are “electrodes of the third kind” because they detect cations which also form low-solubility salts with sulfide anions and forms low-solubility salts with silver. The electrode functions as a sensor or ionic conductor.
IV.
V. Equipment required: • Hanna HI 5315 Double Junction Reference Electrode with HI 7072 Fill Solution for HI 4012. • 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 (ion) meter is not available). • Hanna HI 180 Magnetic Stirrer or equivalent with TFE coated stirring bars (HI 731320). Note: isolate beakers from stirrer motor heat by placing insulating material such as foam or cork between them.
VII VII. General Guidelines • Use of a hood and protective clothings is advised when handling lead solutions. • Concentrated samples (>0.10 M) should be diluted before measurement. Multiply the final result by the corresponding dilution factor. • Calibration standards and sample solutions should have the same ionic strength. ISA and Methanol/ Formalin should be added to both samples and standards in the same ratio. 2 parts ISA to 50 parts standard (or sample)/50 parts Methanol/Formalin is the normal dosing.
• Gas bubbles may form from solution out-gassing due to temperature change. Gently tap body of sensor to dislodge them from sensing membrane. HI 4012 • Remove protective cover from sensor tip. HI 4112 • Remove the protective plastic wrap that covers the ceramic junction before assembling sensor for the first time. • HI 7072 reference fill solution should be added daily to electrolyte reservoir before electrode use. • During measurement always operate electrode with the fill hole open.
Deionized Water VIII. Electrode Preparation HI 4012 1. Remove protective cover from sensor tip. 2. Prepare reference electrode by filling outer electrolyte reservoir with HI 7072. 3. Place sensor and reference electrodes into electrode holder and connect cable connectors to meter. HI 4112 1. Unwrap plastic film seal found over ceramic junction on inner stem and discard. This is only used for shipping and long term storage. 2.
HI 4112 ULFATE LEAD/S ATION IN COMB 6. Holding the body of the electrode gently press upper cap with your thumb. This permits the fill solution to drain out of the body. Release cap and verify electrode returns to its original position. (You may need to gently assist for this to occur). 7. Tighten the electrode cap onto the body and fill electrode body until fill solution volume is just below fill hole. 8. Position electrode in a Hanna HI 76404 electrode holder (or equivalent) and connect plug to meter.
IX. Quick Check of Electrode Slope Use of a hood and protective clothing is strongly advised. • Connect sensors to pH/mV/ISE meter • Place meter in mV mode. • Place 50 mL of deionized water into a beaker with stir bar and 2 mL of HI 4012-00 ISA. Add 50 mL of the methanol/Formalin mixture. Add stir bar and place on magnetic stirrer. • Place electrodes into prepared sample. • Add 1 mL of the stock standard HI 4012-01 (or .01 M or .001 M standard by dilution) to the beaker.
applying gentle pressure. Continue polishing until you are satisfied with the surface. If dark deposits appear on polishing strip move the paper slightly and continue polishing. • If the membrane is damaged, the response becomes extremely sluggish, or the slope of the electrode has decreased significantly, and procedures above have not helped, the sensor should be replaced. XI. Direct Calibration and Measurement This method is a simple procedure for measuring many samples.
1) 2) 3) 4) 5) Procedure Follow sections VIII and IX to prepare sensors for measurement. Follow section VI to prepare standards / solution. Standards should bracket and fall within the range of interest. Two mL HI 4012-00 ISA is added to 50 mL of both samples and standards. Fifty milliliters of the methanol/formalin mixture is also added to each sample or standard. Add stir bar and mix before taking measurements. Follow section VII; General Guidelines to optimize test set-up.
This technique is called Known Addition. The method can use an ideal sensor slope, but actual determined slopes at the temperature of measurement should be used if known. The volume and concentration of the added standard must cause a mV change of at least 8 mV. This method is preprogrammed in the Hanna HI 4222 pH/ISE/mV meter, which simplifies the method greatly. The method works well for samples with high ionic strengths.
the sulfate ions forming a precipitate. Pb2+ + SO4.2- <—> PbSO4 (insoluble) At the stoichiometric end point, a change in mV occurs. Measurements may be automated by use of the Hanna Titrator HI 901 or titrated manually. Plot generated on Hanna HI 901 Titrator during automated sulfate titration using HI 4112 electrode. Notes: • Use of the methanol/formalin antioxidant is advised to increase sensitivity. • Addition of ISA is suggested (2mL/50mL sample). • pH adjustment of the sample to 4-6 range is advised.
Plot generated on Hanna HI 901 Titrator during automated lead titration using HI 4112 electrode. Notes: • Use of the methanol/formalin antioxidant is advised to increase sensitivity. • pH adjustment of the sample to 4-7 pH is advised to favor the Pb-EDTA formation constant. XIII. pH XIII.pH HI 4112 and HI 4012 electrodes may be used in solutions with pH values between 4 and 6. Samples that fall beyond this range should be adjusted with perchloric acid or sodium hydroxide. XIV.
MAN4112 01/07 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.
