Tris (2-carboxyethyl) phosphine hydrochloride (TCEP HCL) is a water soluble strong reducing agent that cleave disulfide bonds. It is a non-thiol and non-volatile solid. It can be utizlied as catalyst for the reduction of sulfonyl chlorides, N-oxides, sulfoxides and azides.

In measuring DHA (Dehydroascorbic acid) content in multiple tissues and plasma of 6-weeks-old mice, 35 mM TCEP HCL fully reduced DHA to AA (Ascorbic acid) after 2 hours on ice in a 5% solution of metaphosphoric acid containing 1 mM ethylenediaminetetraacetic acid (EDTA) at pH 1.5 [1]. In Aspergillus saitoi protease type XIII and porcine pepsin, TCEP can also be used in proteolysis and hydrogen/deuterium exchange [2].

Reference:
1.  Sato Y, Uchiki T, Iwama M, Kishimoto Y et al. Determination of dehydroascorbic acid in mouse tissues and plasma by using tris(2-carboxyethyl)phosphine hydrochloride as reductant in metaphosphoric acid/ethylenediaminetetraacetic acid solution. Biol Pharm Bull. 2010;33(3):364-9.
2.  Zhang HM, McLoughlin SM, Frausto SD et al. Simultaneous reduction and digestion of proteins with disulfide bonds for hydrogen/deuterium exchange monitored by mass spectrometry. Anal Chem. 2010 Feb 15;82(4):1450-4.