Description
Sodium glycinate is a non-essential amino acid. It is found primarily in gelatin and silk fibroin and used therapeutically as a nutrient. It is also a fast inhibitory neurotransmitter.
Chemical Properties
White or light yellow crystalline powder. Hygroscopic, easily soluble in water.
Uses
Sodum glycinate is a useful research chemical. It Inhibits spinal cord neurotransmitter, allosteric regulator of NMDA receptors.
Application
Sodium glycinate is a substance with low toxicity, cost, and aggressiveness, and it is an effective cleaning option. Glycinate can react with silver compounds to form the polymeric compound silver glycinate (I), soluble in water. Glycinate also reacts with copper to form copper (II) glycinate, also soluble in water. Water solubility is due to the complexes’ ability to form hydrogen bonds. In addition to water solubility, which fulfills the criterion of keeping the cleaning reaction products within the solution, amino acids are capable of solubilizing silver and copper. Corrosion products can be removed using 0.1-mol L1 sodium glycinate solution (pH 10) from artificially tarnished silver coins and naturally tarnished silver objects with a high silver content (90% or above)[1]. In the past sodium glycinate (SG) in glycerol was used in an immobilized liquid membrane in a closed loop life support systems, such as in spacecraft or space suits for removal of carbon dioxide from the atmosphere[2].
Hazard
Sodium glycinate is a compound that can be obtained by reacting the amino acid glycine with sodium hydroxide. Because glycinate is soluble in water, it requires less water for cleaning, and it is not a toxic substance or mixture, according to the GHS (Thermo Fisher Scientific, Safety Data Sheet). However, as the pH of the medium makes it reactive with skin, handling the sodium glycinate solution requires gloves. Another difference between glycinate and thiourea is that the former does not cause wear on the metallic surface. Thiourea, however, causes micro-roughness. Thus, polishing can be required after the treatment.
Synthesis
The general procedure for the synthesis of sodium glycinate from N-methyl-2-hydroxyethylamine is as follows: first, 10 g of Pd-doped copper catalyst (based on dry matter calculations, loaded on Degussa AG, CE 1015 OY/W activated carbon) was suspended in water and, similar to the method of Example 1, added to an autoclave along with 61 g of ethanolamine. Subsequently, 272 g of 15 wt% sodium hydroxide solution was added. After sealing the autoclave, the reaction mixture was heated to 160°C. During the reaction, the system pressure was maintained at 12 bar (absolute pressure) and the generated hydrogen was continuously vented through a pressure control valve. The end point of the reaction was determined by observing a significant decrease in hydrogen release. Upon completion of the reaction, the mixture was cooled to 90 °C and the catalyst was removed by filtration to yield 315 g of filtrate. The content of sodium glycinate in this filtrate was 29.8 wt%, corresponding to 96.7% of the theoretical yield. Finally, the filtered catalyst was suspended in 10 g of water for the next batch.
References
[1] Ho-Jun Song. “Solubilities of carbon dioxide in aqueous solutions of sodium glycinate.” Fluid Phase Equilibria 246 1 (2006): Pages 1-5.
[2] Joo Cura D’Ars de Figueiredo Junior. “The Cleaning of Silver Objects With a Basic Solution of Sodium Glycinate: A Study on Artificially and Naturally Tarnished Silver.” Studies in Conservation 66 1 (2021): 375–383.
