1、 FORD LABORATORY TEST METHOD AM 106-01 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 5 Copyright 2001, Ford Global Technologies, Inc. DETERMINATION OF BENZOATE AND TRIAZOLE IN COOLANT BY LI
2、QUID CHROMATOGRAPHY Application This method is used to determine the concentrations of sodium benzoate and benzotriazole corrosion inhibitors in formulated automotive coolant. The method is based on the technique of high pressure liquid chromatography. The separation of the corrosion inhibitors is a
3、ccomplished using a reverse phase C-18 column and an isocratic mobile phase consisting of a volume to volume mixture of 50% sodium acetate buffer/50% methanol at a pressure of 1000 to 2000 psig. The compounds are detected by means of their UV absorbance at 254 nm and quantitation is accomplished by
4、use of external standards. Equipment Required 1. Hewlett-Packard 1100 Series Liquid Chromatograph or equivalent. 2. Hewlett-Packard 3396C Integrator or equivalent. 3. Phenomenex Selectosil reverse phase C-18 column or equivalent. 4. Analytical balance, Mettler Model AE 160 or equivalent. 5. pH meter
5、, Brinkmann Metrohm Model 744 with combination electrode or equivalent. 6. Vacuum system 7. Gelman # 4200 47 mm magnetic filtration funnel - 300 mL plastic with stainless steel coupling ring and support screen. 8. Kimax 2000 mL filtering flask 9. Metrical 47 mm, .45 m membrane filters 10. Syringe Fi
6、lters - 0.45 m. 11. Kimax 4000 mL graduated beaker 12. Pyrex 1000 mL graduated FORD LABORATORY TEST METHOD AM 106-01 Page 2 of 5 Copyright 2001, Ford Global Technologies, Inc. Reagents Required 1. Water - HPLC grade 2. Methanol - HPLC grade 3. Sodium Acetate Trihydrate - HPLC grade 4. Glacial Acetic
7、 Acid - reagent grade 5. Sodium Benzoate - analytical grade, 99% 6. Benzotriazole - analytical grade, 99+% 7. Sodium Hydroxide Solution - 10-15% Preparation of the Mobil Phase The glassware and filtration equipment used in preparing the mobile phase should be very clean. The mobile phase used in thi
8、s method consists of two parts: 1. Solvent A = 0.08 M Sodium Acetate buffer solution (50%) 2. Solvent B = HPLC grade methanol (50%) A. Solvent A Preparation (Sodium Acetate Buffer Solution) 1. Add 44 grams of HPLC grade sodium acetate trihydrate to a lean four-liter glass beaker. Add HPLC (or nanopu
9、re) grade water to make up four liters of solution. Stir until sodium acetate is dissolved. 2. While stirring, adjust the solution pH to 6.0 using a pH meter and drop wise addition of reagent grade glacial acetic acid. 3. Filter the completed solvent A through a 0.45 micron membrane filter using the
10、 Gelman filtration apparatus. Fill the one liter reservoir marked Solvent A and store the remaining mobile phase in a clean, labeled four liter glass container. Keep refrigerated. B. Solvent B Preparation (HPLC grade methanol) 1. No preparation required. Fill the one liter reservoir marked Solvent B
11、. FORD LABORATORY TEST METHOD AM 106-01 Page 3 of 5 Copyright 2001, Ford Global Technologies, Inc. Preparation of the Standard 1. Prepare a concentrated stock solution of the high-purity corrosion inhibitor standards. Weigh the following amounts of corrosion inhibitor standards into a 100 mL volumet
12、ric flash on the analytical balance: a. Sodium Benzoate: 0.820 g (820 mg) b. Benzotriazole: 0.100 g (100 mg) 2. Add 20-30 mL of HPLC-grade methanol to the 100-mL volumetric flask containing the weighed standards. Add 4-5 drops of dilute (10-15%) NaOH to the flask. Swirl the flask until the standards
13、 are completely dissolved. Then, fill the flask to the mark with a volume/volume solution of 50% sodium acetate buffer/50% methanol. 3. Store the stock solution in a dated amber bottle in the refrigerator when not in use. A new stock solution should be prepared every six months. 4. Prepare the worki
14、ng solution by pipetting 10 mL of the stock solution into a 100 mL volumetric flask. Fill the flask to the mark with the 50/50 volume percent solution of mobile phase. After thorough mixing, this constitutes the working standard solution needed for routine sample analysis. Record the standard prepar
15、ation in the standard log book. 5. The working standard solution should also be kept in a dated amber container in the refrigerator when not in use. Prepare additional working standard solutions from the stock solution as needed (See Step 4). Preparation of the Sample 1. Weigh an appropriate amount
16、of automotive coolant into a 100 mL volumetric flask on the analytical balance. Most antifreeze formulations require 4-5 grams. Record the weight of the sample. 2. Add a solution consisting of 50% sodium acetate buffer/50% methanol by volume to the mark and mix well. Filter the prepared sample throu
17、gh a syringe filter into the auto sampler vial and cap it. This constitutes the prepared sample ready for analysis. Calibration 1. Calibration of the method using the working standard solution is required for each series of analyses and at a minimum of one/day when automotive coolant samples are ana
18、lyzed. A calibration standard should be analyzed after every 8-10 samples. 2. Standard calibration response factors are recorded in the instrument log book. FORD LABORATORY TEST METHOD AM 106-01 Page 4 of 5 Copyright 2001, Ford Global Technologies, Inc. Procedure 1. Check the volume of solvents cont
19、ained in the one-liter glass containers. Make sure that there is enough solvent present to complete the analysis. 2. Set up the following parameters on the Liquid Chromatograph: a. Wavelength - 254 nm b. Injection Volume - 5.0 l c. Stop Time - 8.50 minutes d. Flow Control: 50% Solvent A / 50% Solven
20、t B e. Mobile Phase Flow Rate - 1.30 mL/Min. . Load the following parameters in the integrator: a. ZERO = 10 b. ATT = 6 c. CHT SP = 1.0 d. REJ = 50000 e. THRSH = 2 f. PK WD = 0.04 4. Start the instrument and allow system to equilibrate. This will take 10-15 minutes and is indicated by a steady basel
21、ine. 5. Place the filled vials containing standards and samples in the auto sampler tray. 6. Verify auto sampler information input and begin sequence. 7. The integrator will automatically print out the results upon completion of the analysis. The order of elution and retention times of the corrosion
22、 inhibitors are as follows: Order of Elution Retention Time a. Sodium Benzoate 1.73 b. Benzotriazole 2.63 8. Standards and samples should be injected in duplicate. The peak areas for the components of interest should match in at least the first 2-3 decimal places. Also, the peaks should be symmetric
23、al and well-resolved. FORD LABORATORY TEST METHOD AM 106-01 Page 5 of 5 Copyright 2001, Ford Global Technologies, Inc. Calculations 1. Calculate a response factor for each component in the standard as shown: Response Factor for Component A = Peak Area of Component A in Standard Wt. of Component A in
24、 Standard (mg) Note: Record all standard response factors in the laboratory notebook. 2. Calculate the weight % of each component in the sample as shown: Wt. % Component A = Peak Area of Component A in Sample x 100 Standard Response Factor for Component A Report Results must be reported to three significant figures. Reference This procedure is based on Valvoline procedure CAF-PR-012. 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.
