Manual - Hach Nitrate and Nitrite Test Strips
Contents
1. Description Quantity Test Unit Catalog number Ammonium Sulfate Reference Electrolyte Gel Cartridge varies 2 pkg 2597102 Nitrate Electrode Membrane Tips varies 16 pkg 4613300 Nitrate Nitrogen Standard Solutions 10 mg L as NO3 N varies 500 mL 30749 Nitrate ISA liquid varies 500 mL 2488349 Nitrate half cell filling solution varies 50 mL 4456369 Nitrate Nitrogen Standard Solution 100 mg L NO3 N varies 500 mL 194749 Nitrate test strips varies 25 pkg 2745425 Water deionized varies 4L 27256 Required apparatus Description Unit Catalog number Beaker 150 mL polypropylene each 108044 Bottle wash 500 mL each 62011 Pipet TenSette 0 1 1 0 m each 1970001 Flask volumetric poly 100 mL each 1406042 Thermometer Digital each 2630600 Flask volumetric 100 mL polypropylene each 1406041 Nitrate Combination Electrode Platinum series BNC each 5192000 sension 4 Laboratory pH ISE Meter each 5177500 Stir Bar 7 8 x 3 16 in 22 2 x 4 8 cm each 4531500 Stir Bar 11 8 x 3 10 in 28 6 x 7 9 cm each 2095355 Select one based on available voltage Stirrer electromagnetic 115 VAC with stand and stir bar each 4530001 Stirrer electromagnetic 230 VAC with stand and stir bar each 4530002 Nitrate Electrode Membrane Tips replacements 6 pkg 4613300 Nitrate Page 9 of 10 Nitrate Optional reagents Pipet Mohr 2 00 mL glass Description Unit Catalog number Nitrate lonic Strength Adjustor powder 454 g 44563012. For the nitrate electrode the major interferences include perchlorate iodide nitrite bromide and chloride The addition of Nitrate ISA will eliminate most of these interferences The highest level of chloride the ISA can accommodate is 40 mg L Cl Concentrations greater than 40 mg L CI in the sample will cause false high nitrate values For more information on selectivity coefficients without ISA refer to the Electrode Characteristics section of the electrode manual Sample collection preservation and storage e Collect samples in clean plastic or glass bottles e Start nitrate measurements promptly after sampling If storage is necessary store for up to 24 hours at 4 C or lower as per the USEPA MUR in March 2007 the storage criteria changed from 4 C to 0 6 C Do not adjust sample pH This method is for low ionic strength use only Adjusting the pH with acid will change the ionic strength and make this method unusable Accuracy check Checking electrode response To verify electrode response at these low levels of nitrate the millivolt potential should decrease upon each addition of 100 mg L NO3 N Using the Low Level Nitrate Nitrogen procedure at least a 5 0 mV drop should be observed from step 1 to step 2 0 040 mg L to 0 080 mg L NO3 N Each additional spike should decrease the mV reading substantially from the previous change If this is not the case check the purity of the standard If this is not the problem use a
3. Nitrate DOC316 53 01239 Direct Measurement ISE Method Method 8359 0 04 to 4 00 mg L NO N TISAB Solution Scope and Application Drinking water Test preparation How to use instrument specific information The nstrument specific information table displays requirements that may vary between instruments To use this table select an instrument then read across to find the corresponding information required to perform this test Table 452 Instrument specific information Meter Electrode sension 4 meters 5192000 1 Only sension 4 meters can be used for this analysis Before starting the test Refer to the meter user manual for meter operation Refer to electrode manual for electrode maintenance and care When using the electrode for the first time condition the reference electrode for eight hours in a 100 mg L nitrate nitrogen standard After initial conditioning before the first use or after long term storage condition the electrode for 60 minutes only unless the electrode is stored dry for longer than four weeks If the electrode is used daily store the electrode in a nitrate standard having a concentration similar to the measured samples The low range nitrate test requires several conditioning steps and careful attention to temperature Read through the procedure steps and the Sample collection preservation and storage section before proceeding The 2 hour conditioning step must be completed be
4. Nitrate Nitrogen Standard Solutions 1 mg L as NO3 N 500 mL 204649 Optional apparatus Description Unit Catalog number Beaker 100 mL polypropylene each 108042 Pipet Tips for TenSette Pipet 50 pkg 2185696 Water Bath circulating each 2616300 each 2093636 In the U S A Call toll free 800 227 4224 Hach Company 2007 2010 2012 All rights reserved Printed in the U S A FOR TECHNICAL ASSISTANCE PRICE INFORMATION AND ORDERING Outside the U S A Contact the HACH office or distributor serving you On the Worldwide Web www hach com E mail techhelp hach com HACH COMPANY WORLD HEADQUARTERS Telephone 970 669 3050 FAX 970 669 2932 Edition 7
5. completely or the pressure will cause the membrane tip to fall off Use a gentle twisting action to carefully slide a clean dry nitrate membrane tip over the glass stem until the end of the stem rests midway through the Nitrate Membrane Tip and some resistance is met Leave a 1 8 inch gap between the tip and the electrode body Shake the electrode as if shaking down mercury in a thermometer to make sure the Nitrate Electrode Filling Solution contacts the end of the nitrate membrane tip Verify that air bubbles are not present in the tip Electrode assembly Nitrate Page 6 of 10 1 2 Remove the cap from the electrolyte cartridge Visually inspect the Luer tip of the electrolyte cartridge If air is present rotate the feed screw counter clockwise until gel expels the air and fills the tip Fit the cartridge outlet tube firmly onto the inlet tube of the electrode body Place the dispenser unit over the electrolyte cartridge Screw the dispenser unit onto the electrode body until reaching the stop Do not over tighten Dispense the electrolyte gel by pressing the pump button Repeat this procedure until gel is visible at the reference outlet If readings become erratic make sure that the electrolyte gel is completely purged through the reference line Rinse the electrode with deionized water Do not scrub the electrode tip Connect the BNC connector of the electrode to the BNC connector on the meter Nitrate Interferences
6. new membrane Checking calibration accuracy 1 Pipet 1 mL liquid Nitrate ISA into a 100 mL volumetric flask 2 Fill the 100 mL volumetric flask to the mark with 1 0 mg L NO3 N Pour this solution in a 100 mL beaker and add a stir bar 3 Put the beaker on an electromagnetic stirrer and measure the concentration of the solution with the calibrated electrode The measurement should be 1 0 mg L 0 1 mg L Note The beaker containing the 3 0 mg L NO3 N standard used in the calibration may also be used as a check on the calibration It should read close to 3 0 mg L NO3 N 0 1 mg L Nitrate Page 7 of 10 Nitrate Checking the accuracy of the sample reading To verify sample measurement accuracy add a spike of standard NO3 N solution with a TenSette or volumetric pipet Use the Spike volumes of 100 mg L standard table and the formulas in Percent recovery Table 454 Spike volumes of 100 mg L standard Measured sample Concentration Volume of 100 ppm Standard to CxV NO3 N Add 0 04 to 0 3 0 1 mL 10 0 30 to 0 60 0 3 mL 30 0 6 to 0 9 0 5 mL 50 0 9 to 3 0 1 0 mL 100 Percent recovery To calculate the percent recovery M x100 CxV M waar R x100 Where M calculated mass of nitrate as nitrogen present after the spike micrograms S mg L of NO3 N in sample before spike C concentration of standard used for spiking mg L V spike volume from the Spike volumes of 100 mg
7. standard solution in the 150 mL beaker used to perform the calibration A white precipitate will form if chloride or other ions that react with silver are present in solution This will not hurt the electrode or interfere with the analysis Calibration ra L 14 Pour this 100 mL of sample into a 150 mL beaker Add a magnetic stir bar place the beaker on an electromagnetic stirrer Stir at a moderate rate 15 Put the electrode into the sample and press the electrolyte dispenser button once HRS MIN SEC 16 Wait 5 10 minutes to allow electrode to condition to the low level nitrate in solution Read the nitrate concentration from the display after it stabilizes This is the sample nitrate concentration expressed as elemental nitrogen NO3 N Note Record this value Between uses the electrode can be stored in the sample if not an extreme pH See electrode manual for details Make sure to measure millivolt potentials of all nitrate standards at the same temperature 0 5 C The sample and standards must be measured at the same temperature 1 C This procedure keeps temperature error to a minimum by using a spiked additions method of calibration Even so care should be taken to use the 100 mg L NO3 N standard at room temperature Use a water bath slightly above room temperature 25 C to equilibrate the standard temperature and sample temperature before measuring mV potentials Use a labor
8. L standard table mL E expected concentration after spiking mg L R percent recovery should be 95 100 A actual reading on meter after spike mg L NO3 N Method performance Precision instrument Standard 95 Confidence Limits of Distribution sension 41 0 1 mg L 0 095 0 1005 mg L 1 With a stabilization criteria of 0 1 mV min Nitrate Page 8 of 10 Summary of method Nitrate Nitrate ions are selectively absorbed by the ISE membrane establishing a potential voltage that is proportional to the concentration of nitrate in the sample This potential is compared to the constant potential of a reference electrode by measuring the potential of known standard A calibration curve can be constructed to determine the concentration of nitrate in unknown samples The solvent polymer membrane is a nitrate ion exchanger in an inert polyvinyl chloride PVC plastic matrix The nitrate electrode has an internal silver silver chloride element which establishes a fixed potential when in contact with the internal filling solution The ion selective membrane undergoes ion exchange with nitrate in the sample creating a potential across the membrane which varies with the amount of nitrate ion in the sample This potential will decrease by about 58 mV for every tenfold increase in nitrate concentration in the linear operating range at 25 C Consumables and replacement items Required reagents
9. Nitrogen liquid ISA method continued READ enter 9 Edit the display to show the concentration of the solution in the 150 mL beaker 0 040 mg L Refer to the Low level nitrate calibration table Press ENTER to accept the concentration Nitrate Page 4 of 10 Repeat step 10 10 When the measurement stabilizes pipet the corresponding additional volume from the Low level nitrate calibration table Wait the amount of time specified for step 2 in the table to allow the membrane to respond 11 Repeat step 10 adding the additional volumes of 10 mg L and 100 mg L NO N standard from the Low level nitrate calibration table until all seven standards have been measured Store the calibration and return to Enter the concentration in Measurement mode mg L 0 080 mg L Accept the concentration If Error 2 occurs use 0 08 mg L as the first standard for this calibration Then try conditioning in 0 04 mg L NO 3 N solution for subsequent attempts ia 12 Remove the electrode from the last standard rinse well with deionized water and blot dry Save the solution in the 150 mL beaker with the 3 84 mg L NO3 N for later calibration checks Nitrate Nitrogen liquid ISA method continued Nitrate 13 Accurately pipet 5 mL of nitrate liquid ISA into a Class A 100 mL volumetric flask Bring to the mark with the sample being measured The sample must be at the same temperature as the
10. atory grade thermometer to monitor the temperature A one degree centigrade difference may result in as much as a 0 4 mV inaccuracy This temperature variation will in turn decrease accuracy of concentration measurements Nitrate Page 5 of 10 Nitrate Table 453 Low level nitrate calibration table Step Volume 10 mg L NO3 N Volume 100 mg L NO3 N Concentration standard added standard added mg L Time 1 0 4 mL 0 040 30 min 2 0 4 mL 0 080 10 min 3 1 2 mL 0 20 5 min 4 0 2 mL 0 40 5 min 5 0 4 mL 0 80 5 min 6 1 2mL 1 96 5 min 7 2 0 mL 3 84 5 min Nitrate half cell preparation 1 Condition the nitrate membrane tip by immersing the membrane tip in beaker with 100 mg L NO3 N solution for approximately one hour prior to use When using th electrode for the first time condition the reference electrode for eight hours in a 100 mg L nitrate nitrogen standard Clean all gel from the electrode tip and glass stem Rinse with Deionized water and dry completely with a soft paper towel Use a soft paper towel soaked in isopropyl or rubbing alcohol to wipe the glass stem Dry the stem with a dry soft paper towel Make sure that alcohol does not get in the glass stem Use the provided syringe to fill the membrane to with the electrode filling solution Fill with solution to the top of the tip Alternatively fill the glass stem as shown in the electrode manual Do not fill the stem
11. fore the calibration step Sample concentration for this test must be 3 0 mg L NO3 N or less Use a test strip to determine nitrate concentration If the electrode is conditioned to a low nitrate nitrogen concentration as in this procedure putting it in a concentrated NO3 N sample 10 mg L or higher will swamp the electrode with nitrate ion and the 2 hour conditioning step must be repeated Note A If the electrode is conditioned properly the mV potential should not change more than 0 1 mV every five minutes in step 7 It may be necessary to press the electrolyte dispenser button again to stabilize the potential reading If the potential drifts one direction more than 0 2 mV every 5 minutes leave the electrodes in the 150 mL beaker until the drift has slowed If the drift is higher than 0 1 mV per minute the electrode should be conditioned longer in 100 mL of 0 040 mg L standard Do not put ISA into the standard Prepare the electrode Refer to Electrode assembly and Nitrate half cell preparation in this procedure Use identical amounts of ionic strength adjustor ISA in the standard beaker and in sample measurements Use liquid ISA Temperature variation causes inaccurate measurements Calibration and sample measurements should be made at the same temperature 1 C The stable sample reading is the nitrate nitrogen NO3 N concentration expressed as elemental nitrogen N The results can be expressed as mg L nitrate NO37 by mult
12. iplying the results by 4 4 Nitrate Page 1 of 10 Nitrate Collect the following items Nitrate ISA solution Nitrate Electrode Membrane Tip replacement Pipet TenSette 0 1 to 1 0 mL Pipet TenSette 1 0 to 10 0 mL Nitrate Nitrogen standard solutions 10 mg L as NO3 N 100 mg L as NO3 N Water deionized Beaker 150 mL polypropylene Bottle wash 500 mL Cylinder graduated 25 mL polypropylene Combination Nitrate Electrode BNC sension 4 laboratory Stir Bar 7 8 X 3 16 in 22 2 x 4 8 cm Stirrer electromagnetic with stand and stir bar Thermometer Digital 100 mL plastic volumetric flask Description Quantity Ammonium sulfate reference electrolyte gel cartridge 1 Nitrate half cell internal filling solution 0 5 mL 25 mL per sample or standard 1 1 1 25 mL 25 mL varies 3 See Consumables and replacement items for reorder information Nitrate Page 2 of 10 Nitrate Nitrogen liquid ISA method Nitrate N 1 Condition the electrode in 100 mg L NO 3 N standard for one hour refer to Nitrate half cell preparation and Electrode Assembly in this procedure Then condition the electrode in 0 010 mg L NO3 N for at least 2 hours To make 100 mL of 0 010 mg L NO3 N use a TenSette Pipet to deliver 0 10 mL of 10 mg L NO3 N into a 100 mL volumetric flask and dilute to the mark Mix well 5 Use a TenSette Pipet to add 0 4 mL of 10 mg L nitrate nitrogen standard s
13. olution to the solution in the beaker this makes 100 mL of 0 04 mg L nitrate nitrogen Allow the electrode to condition for 30 minutes in this solution before proceeding 2 Usea TenSette Pipet to pipet 5 0 mL of of nitrate liquid ISA into a plastic 100 mL volumetric flask Bring to the 100 mL mark with deionized water The deionized water must be at room temperature 6 Turn the meter on Press SETUP set the electrode type to BNC and scroll to Stabilizing Press ENTER and edit the display to show 0 1 mg min Accept the value and EXIT the setup menu pi L 3 Pour the solution from the flask into a 150 mL beaker Add a large stir bar 50 8 x 7 9 mm to the beaker place the beaker on an electromagnetic stirrer and begin stirring ata moderate rate 7 Press ISE MV until the mV potential shows on the display Refer to Before starting the test Note A After the measurement is stable record the potential value Measure the temperature of the standard C with a lab grade thermometer Record the temperature LIO 4 Remove the electrode from the 0 010 mg L nitrate nitrogen standard and rinse it well with deionized water Place the electrode in the 150 mL beaker submerging the tip below the solution surface 8 Press ISE MV to toggle to concentration units Press CAL and scroll to mg L Press ENTER and accept the concentration units Nitrate Page 3 of 10 Nitrate Nitrate
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