(Ethylenedinitrilo)tetraacetic Acid - ACS Reagent Chemicals (ACS

Monograph pubs.acs.org/doi/book/10.1021/acsreagents

(Ethylenedinitrilo)tetraacetic Acid (N,N,N′,N′-Ethylenediaminetetraacetic Acid; N,N′-1,2-Ethanediylbis[Ncarboxymethyl]glycine; EDTA, Free Acid)

Downloaded by CORNELL UNIV on June 18, 2017 | http://pubs.acs.org Publication Date (Web): February 28, 2017 | doi: 10.1021/acsreagents.4139

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 provides, in addition to common physical constants, a general description including typical appearance, applications, change in state (approximate), 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, Insoluble in Dilute Ammonium Hydroxide, Residue after Ignition, Nitrilotriacetic Acid, Calcium, Magnesium, Heavy Metals, and Iron.

C10H16N2O8

Formula Wt 292.24

CAS No. 60-00-4

GENERAL DESCRIPTION Typical appearance . . . . . . . . Applications . . . . . . . . . . . . . Change in state (approximate) . Aqueous solubility . . . . . . . . .

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white solid chelating agent melting point, 220 °C, with decomposition 0.05 g in 100 mL at 25 °C

SPECIFICATIONS Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99.4–100.6% C10H16N2O8

© 2017 American Chemical Society

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ACS Reagent Chemicals ACS Reagent Chemicals; American Chemical Society: Washington, DC, 2017.

DOI:10.1021/acsreagents.4139 ACS Reagent Chemicals, Part 4

ACS Reagent Chemicals

Monograph

pubs.acs.org/doi/book/10.1021/acsreagents

Insoluble in dilute ammonium hydroxide. Residue after ignition. . . . . . . . . . . . . Nitrilotriacetic acid [(HOCOCH2)3N] . . . . Calcium (Ca) . . . . . . . . . . . . . . . . . . Magnesium (Mg) . . . . . . . . . . . . . . . . Heavy metals (as Pb) . . . . . . . . . . . . . Iron (Fe) . . . . . . . . . . . . . . . . . . . . .

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Maximum Allowable 0.005% 0.2% 0.1% 0.001% 5 ppm 0.001% 0.005%

TESTS Downloaded by CORNELL UNIV on June 18, 2017 | http://pubs.acs.org Publication Date (Web): February 28, 2017 | doi: 10.1021/acsreagents.4139

Assay (By complexometric titration). Weigh accurately about 4.0 g, and transfer to a 250 mL volumetric flask. Dissolve in 25 mL of 1 N sodium hydroxide volumetric solution, 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 N sodium hydroxide volumetric solution 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 in the titration; and Ws = weight, in g, of the sample in aliquot.

Insoluble in Dilute Ammonium Hydroxide To a 20.0 g sample, add 190 mL of water and 0.10 mL of methyl red indicator solution. Slowly add ammonium hydroxide, keeping the solution acidic, until all the sample is dissolved. Warm if necessary. Heat to boiling, and digest in a covered beaker on a hot plate (~100 °C) for 1 h. Filter through a tared filtering crucible, wash thoroughly, and dry at 105 °C.

Residue after Ignition [Part 2: Gravimetric Methods; Residue after Ignition]. Ignite 3.0 g. Moisten the char with 1 mL of sulfuric acid.

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).


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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.


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.

Calcium and Magnesium (By flame AAS, [Part 2: Trace and Ultratrace Elemental Analysis; Atomic Absorption Spectroscopy; Analysis; Procedure for Flame AAS]).

For the Determination of Calcium and Magnesium

S a m p l e S t o c k S o l u t i o n . Dissolve 5.0 g of sample in 50 mL of water and 5 mL of ammonium hydroxide in a 150 mL beaker, and heat if necessary. Transfer to a 100 mL volumetric flask, and dilute to the mark with water (1 mL = 0.05 g).

For the Determination of Calcium and Magnesium

Element

Wavelength (nm)

Sample Wt (g)

Standard Added (mg)

Flame Type*

Background Correction

Ca

422.7

1.0

0.01; 0.02

N/A

No

Mg

285.2

1.0

0.005; 0.01

A/A

Yes

*A/A is air/acetylene; N/A is nitrous oxide/acetylene.

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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 . Char 3.0 g thoroughly, and heat in an oven at 500 °C until most of the carbon is volatilized. Cool, add 0.15 mL of nitric acid, and heat at 500 °C until all of the carbon is volatilized. Dissolve the residue in 2 mL of dilute hydrochloric acid (1: 1), digest in a covered crucible on a hot plate (~100 °C) for 10 min, remove the cover, and evaporate to dryness. Dissolve in 1 mL of 1 N acetic acid and 20 mL of hot water, digest for 5 min, cool, and dilute with water to 30 mL (1 mL = 0.1 g).


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Heavy Metals

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[Part 2: Colorimetry and Turbidimetry; Heavy Metals (as Lead); Procedure for Heavy Metals, Method 1]. Dilute 20 mL of sample solution E (2.0 g sample) with water to 25 mL.

Iron†


[Part 2: Colorimetry and Turbidimetry; Iron; Procedure for Iron, Method 1 (Ammonium Thiocyanate)]. Use 2.0 mL of sample solution E (0.2 g sample).


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(Ethylenedinitrilo)tetraacetic Acid - ACS Reagent Chemicals (ACS

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