Monograph pubs.acs.org/doi/book/10.1021/acsreagents
(Ethylenedinitrilo)tetraacetic Acid, Disodium Salt Dihydrate (N,N,N′,N′-Ethylenediaminetetraacetic Acid, Disodium Salt, Dihydrate; N,N′-1,2Ethanediylbis[N-carboxymethyl]glycine, Disodium Salt, Dihydrate; EDTA (Dihydrate)) Part 4, Monographs for Reagent Chemicals: General Descriptions, Specifications, and Tests eISBN: 9780841230460 Tom Tyner Chair, ACS Committee on Analytical Reagents James Francis Secretary, ACS Committee on Analytical Reagents
ABSTRACT This monograph for (Ethylenedinitrilo)tetraacetic Acid, Disodium Salt Dihydrate provides, in addition to common physical constants, a general description including typical appearance, applications, and aqueous solubility. The monograph also details the following specifications and corresponding tests for verifying that a substance meets ACS Reagent Grade specifications including: Assay, pH of a 5% Solution at 25.0 °C, Insoluble Matter, Nitrilotriacetic Acid, Heavy Metals, and Iron.
C10H14N2O8Na2 · 2H2O
Formula Wt 372.24
CAS No. 6381-92-6
GENERAL DESCRIPTION Typical appearance . . . . . . . . . . . . . . . . . . . white solid Applications . . . . . . . . . . . . . . . . . . . . . . . . chelating agent; sequestering agent Aqueous solubility . . . . . . . . . . . . . . . . . . . . 11 g in 100 mL at 20 °C
SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99.0–101.0% C10H14N2O8Na2 · 2H2O pH of a 5% solution at 25.0 °C . . . . . . . . . . . . 4.0–6.0
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4140 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Insoluble matter . . . . . . . . . . . . . Nitrilotriacetic acid [(HOCOCH2)3N] . Heavy metals (as Pb) . . . . . . . . . . Iron (Fe) . . . . . . . . . . . . . . . . . .
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Maximum Allowable 0.005% 0.1% 0.005% 0.01%
TESTS Assay (By complexometric titration). Weigh accurately about 5.0 g of sample, and transfer to a 250 mL volumetric flask. Dissolve in water, dilute to volume with water, and mix thoroughly. Fill a 50 mL burette with this sample solution. Weigh accurately about 0.2 g of calcium carbonate, chelometric standard, that has been dried in an oven at 300 °C for 3 h and cooled in a charged desiccator for 2 h, and transfer to a 400 mL beaker. Cover the beaker with a watch glass. Add 2 mL of 10% hydrochloric acid reagent solution from a pipette placed between the lip of the beaker and the watch glass. Swirl the beaker to aid dissolution. With water, wash down the inner wall of the beaker, the outer surface of the pipette, and the watch glass. Dilute to about 100 mL with water. While stirring, add from the burette about 30 mL of the sample solution. Add 15 mL of 1 M sodium hydroxide and 300 mg of hydroxynaphthol blue indicator mixture. Continue the titration immediately with the sample solution to a blue color.
where Wc = weight, in g, of calcium carbonate; V = volume, in mL, of the sample solution required for titration; and Ws = weight, in g, of the sample in aliquot.
pH of a 5% Solution at 25.0 °C [Part 2: Direct Electrometric Methods; pH Potentiometry; pH Range; Procedure for pH of a 5% Solution at 25.0 °C].
Insoluble Matter [Part 2: Gravimetric Methods; Insoluble Matter]. Use 20.0 g dissolved in 200 mL of hot water.
Nitrilotriacetic Acid Analyze the sample by liquid chromatography using the general method described in [Part 2: Chromatography; Recommended Procedures; Liquid Chromatography; Solvent Suitability for Liquid Chromatography; Procedure for Liquid Chromatography] and the parameters below. Weigh a 1.0 g sample in a 100 mL volumetric flask, add cupric nitrate solution (10 mg/mL) to volume, and sonicate to achieve complete solution. Prepare a standard in the same manner containing 1.0 g of the sample and 100 µL of nitrilotriacetic acid standard solution (0.01 g/mL) in 100 mL of cupric nitrate solution (10 mg/mL). Inject 50 µL aliquots of the sample and standard solutions, and measure the responses for the major peaks. The response for the nitrilotriacetic acid peak in the sample does not exceed the difference in the peak responses for the nitrilotriacetic acid peaks for the standard and the sample.
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4140 ACS Reagent Chemicals, Part 4
ACS Reagent Chemicals
Monograph
pubs.acs.org/doi/book/10.1021/acsreagents
Chromotagraphic Conditions for the Determination of Nitrilotriacetic Acid Mobile Phase . . . . . . . . . . . . . . . . Add 10 mL of 1.0 M terabutylammonium hydroxide in methanol to 200 mL of water, and adjust with 1 M phosphoric acid to pH 7.5 ± 0.1. Transfer the solution to a 1000 mL volumetric flask, add 90 mL of methanol and dilute to volume with water. Mix well, and filter through a 0.5 µm porosity filter before use. Column . . . . . . . . . . . . . . . . . . . . Octyl (C-8), 150 mm × 4.6mm, 5µm Temperature . . . . . . . . . . . . . . . . Ambient Flow Rate . . . . . . . . . . . . . . . . . . 2 mL/min Sample Size . . . . . . . . . . . . . . . . . 50 µL Detector . . . . . . . . . . . . . . . . . . . UV at 254 nm Nitrilotriacetic acid standard (0.01 g/mL): Accurately weigh 100 mg of nitrilotriacetic acid, and transfer to a 10 mL volumetric flask. Add 0.5 mL of ammonium hydroxide and mix. Dilute to volume with water and mix well.
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For the Determination of Heavy Metals and Iron
S a m p l e S o l u t i o n E . To 1.0 g, add 1 mL of sulfuric acid, heat cautiously until the sample is charred, and ignite in an oven at 500 °C until most of the carbon is volatilized. Cool, add 1 mL of nitric acid, heat until the acid is evaporated, and ignite again at 500 °C until all of the carbon is volatilized. Cool, add 4 mL of dilute hydrochloric acid (1:1), digest on a hot plate (~100 °C) for 10 min, and evaporate to dryness. Add 10 mL of aqueous 10% ammonium acetate solution, and digest on a hot plate (~100 °C) for 30 min. Filter, wash thoroughly, and dilute with water to 50 mL (1 mL = 0.02 g).
Heavy Metals† [Part 2: Colorimetry and Turbidimetry; Heavy Metals (as Lead); Procedure for Heavy Metals, Method 1]. Dilute 20 mL of sample solution E (0.4 g sample) with water to 25 mL.
Iron† [Part 2: Colorimetry and Turbidimetry; Iron; Procedure for Iron, Method 1 (Ammonium Thiocyanate)]. Use 5.0 mL of sample solution E (0.1 g sample).
© 2017 American Chemical Society
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DOI:10.1021/acsreagents.4140 ACS Reagent Chemicals, Part 4
