1、 FORD LABORATORY TEST METHOD AM 107-01 Date Action Revisions 2001 01 30 Revised Editorial - no technical change A. Cockman 2000 04 17 Activated A. Reaume Printed copies are uncontrolled Page 1 of 4 Copyright 2001, Ford Global Technologies, Inc. DETERMINATION OF NITRITE IN ENGINE COOLANT BY ION CHROM
2、ATOGRAPHY Application This method is used to determine the concentration of sodium nitrite in automotive antifreeze formulations which also contain sodium benzoate. Principle This method is based on the technique of ion chromatography. The separation of nitrite and benzoate anions in the antifreeze
3、is accomplished by the use of an ionic eluent which is pumped through an ion exchange column and a suppressor column. The anions are separated in the ion exchange separator column based on their affinity for the column resin. After separation, the eluent containing the sample anions passes through a
4、 membrane suppressor which simultaneously neutralizes the ionic species in the eluent and converts the sample anions to their highly conductive acid form. The nitrite anion is then detected by means of a conductivity detector. Identification and quantitation of nitrite is accomplished by an external
5、 standard technique. Equipment Required 1. Ion Chromatograph - Dionex model DX120, or equivalent, with conductivity detector. 2. Anion Guard/Separator Column - Dionex part # AS-4 Guard, AS-4 Separator or equivalent 3. Anion Suppressor Column - Dionex micromembrane suppressor part # 38019 or equivale
6、nt 4. Integrator - Hewlett Packard model 3396C or equivalent. 5. Analytical Balance - + 0.1 mg sensitivity, Mettler model AE160 or equivalent. 6. Pyrex 100 mL Volumetric Flasks - CMS No. 106-377 or equivalent. 7. Pyrex Volumetric Transfer Pipets - (Various capacities, 10, 20 mL), CMS No. 250-816 or
7、equivalent, Class A. 8. Kimax 4000 mL Graduated Beaker - CMS 029-637 or equivalent. 9. pH Meter - Orion model 520A or equivalent with Ross combination pH electrode and temperature compensation probe. FORD LABORATORY TEST METHOD AM 107-01 Page 2 of 4 Copyright 2001, Ford Global Technologies, Inc. Rea
8、gents Required 1. Water deionized - nanopure reagent grade - conductivity 5mohms. 2. Benzoic Acid (C6H5COOH) - reagent grade. 3. Sodium Carbonate (Na2CO3) - reagent grade. 4. Sodium Nitrite (NaNO2) - Certified ACS reagent grade (99 + %) or purchased - traceable 1000ppm N02 standard solution. 5. Citr
9、ic Acid (2-hydroxyl-1-1,2,3-propanetricarboxylic acid) - reagent grade. 6. Sulfuric Acid (1.0 N) - Certified, analytical grade titrant. Eluent Preparation The eluent used for this method consists of 0.001 M sodium carbonate and 0.001 M benzoic acid. The procedure for preparation of four liters of el
10、uent is as follows: 1. On an analytical balance, accurately weigh 0.488 grams of benzoic acid and 0.424 grams of sodium carbonate. 2. Add both of the above to a clean four-liter glass beaker. 3. Add deionized water to make up four liters of solution and stir until components are dissolved. Preparati
11、on of the Standards A 1000 ppm stock solution of nitrite (NO-2) should be prepared as follows: 1. On an analytical balance, accurately weigh 1.4998 grams of sodium nitrite and add to a clean one liter volumetric flask. 2. Dissolve the standard and dilute to the mark with deionized water. Store the s
12、tock solutions in one liter plastic containers in the refrigerator with the preparation date labeled. 3. Record all weights, date, and name of technician in the standards log book. 4. A working standard of 20 ppm nitrite is prepared by pipetting 20 mLs of 1000 ppm nitrite stock solution into a clean
13、 one liter volumetric flask and diluting to the mark with deionized water. Store the stock solution and working standard in the refrigerator until needed. The working standard should be stable for one month. As the working standard is depleted, make up fresh solution using the stock solution. The st
14、ock solution should be stable for three months. FORD LABORATORY TEST METHOD AM 107-01 Page 3 of 4 Copyright 2001, Ford Global Technologies, Inc. Preparation of the Sample 1. On an analytical balance, weigh approximately 0.6 grams of antifreeze into a disposable 250 mL plastic beaker. Record actual w
15、eight. 2. Add 50 mLs of deionized water to the beaker and swirl to mix. Determine the pH of the solution using a previously calibrated pH meter. 3. The sample must be acidified to a pH of 4.9 - 5.1. This can be accomplished using a citric acid solution consisting of 2 grams +/- 0.5g citric acid diss
16、olved in 30 mLs of deionized water. Add the citric acid solution drop wise while observing the pH until the correct range is obtained. 4. Remove the pH electrodes from the sample and rinse with deionized water into the beaker. Replace electrodes in pH 7 buffer solution. 5. Quantitatively, transfer t
17、he acidified sample solution into a 100 mL volumetric flask. Rinse the beaker with deionized water and transfer to the volumetric flask. Dilute to the mark with additional deionized water and mix well. Procedure 1. Check to make sure that there is proper amount of eluent present to complete the anal
18、ysis. To determine this amount, multiply the flow rate runtime number of samples. This calculation will determine total amount of solutions needed. 2. Turn on instrument power and set the Dionex instrument and chart recorder controls as follows: a. Eluent Pressure = On b. Pump = On c. SRS = On d. Fl
19、ow Rate = 1.3 mL /Min e. Control = Local f. Sample = Load 3. Allow the system 15 minutes to reach equilibrium as indicated by a steady baseline and low conductivity. Turn auto zero on. 4. With all instrument systems operating normally, press run on the autosampler to begin the injection queue. All s
20、tandards and samples are injected sequentially. 5. The order of elution is as follows: a. Benzoate b. Nitrite c. Nitrate FORD LABORATORY TEST METHOD AM 107-01 Page 4 of 4 Copyright 2001, Ford Global Technologies, Inc. 6. If the baseline is extremely noisy and unstable, check for: a. contaminated mob
21、ile phase b. liquid leaks in the system c. air bubbles in mobile phase or regenerant system 7. After all analyses are completed, turn the instrument power OFF. Turn off the nitrogen pressure to the regenerant and bleed off the pressure. Clamp the end of the tubing from the suppressor column to stop
22、regenerant flow. Calculations 1. Calculate a response factor for nitrite in the standard as follows: Standard Response Factor for Nitrite = Peak Height of Nitrite in Standard Concentration of Nitrite (in ppm) Note: Record all response factors on lab notebook. 2. Calculate the weight % of nitrite in
23、the sample as follows: Weight % Nitrite = Peak Height of Anion A in Sample (from Integrator) x .01 Sample Weight (g) Standard Response Factor for Nitrite 3. If the nitrite concentration is desired in ppm, multiply the result from Step 2 by 104. Reference This procedure is based on Valvoline procedure CAF-PR-017. Chemicals, materials, parts, and equipment referenced in this document must be used and handled properly. Each party is responsible for determining proper use and handling in its facilities.
