Citric acid thiourea

Complexing agents, which act as buffers to help control the pH and maintain control over the free metal—salt ions available to the solution and hence the ion concentration, include citric acid, sodium citrate, and sodium acetate potassium tartrate ammonium chloride. Stabilizers, which act as catalytic inhibitors that retard the spontaneous decomposition of the bath, include fluoride compounds thiourea, sodium cyanide, and urea. Stabilizers are typically not present in amounts exceeding 10 ppm. The pH of the bath is adjusted. 

The copper complex is very stable at neutral pH, but it fades very rapidly in the presence of hydrogen ions. Other complex formers such as tartaric acid or citric acid and thiourea interfere with the reaction and, therefore, should not be included in mobile phases used for the separation of amino acids [3]. 

Asn = asparagine CitH2 = citric acid tu = thiourea see Thiourea), Ettu = ethylenethiourea Glu = glutamic acid Met = methionine tren = tris(2-aminoethyl)amine Mee tren = tris(2-dimethylaminoethyl)amine, en = ethane-1,2-diamine pn = propane-1,2-diamine. 

Abbreviations conform to Tarr s nomenclature F, formic acid A, acetic acid fA, trifluoroacetic acid KNm, dimethylformamide mSO, methylsulfoxide MOH, methanol EOH, ethanol MCN, acetonitrile M5KN, N-methyl-pyrrolidone 6N, pyridine N, ammonia ENm, dimethylethylamine M6N, N-methylpiperidine M6NO, N-methylmorpholine E6NO, N-ethylmorpholine ENip, diisopropylethylamine eN, triethylamine fmK, hexafluoroacetone (hydrate) cit, citric acid W, water NaA, sodium acetate eN+, tetraethylammonium MNT, methylthiocarbamyl NT, phenylthiocarbamyl MNGS, methylisothiocyanate ONCS, phenylisothiocyanate NPN-TNdab, N-aminopropyl-N -p-dimethylaminoazobenzene thiourea. 

Benzyl-2-aza-bicyclo[2.2.1]hept-5-ene (0.100 g, 0.538 mmol) and 0.094 mL DIEA (0.538 mmol) were added to a solution of 0.103 g EDCI (0.538 mmol) and 0.172 g A-tosyl-A -benzyl thiourea (0.538 mmol) in 5 mL CHCI3 at room temperature. The resulting solution was maintained at room temperature overnight. The reaction mixture was then poured into a mixture of 65 mL EtOAc and 65 mL 0.25M aqueous citric acid. The organic layer was washed with 65 mL 0.25M aqueous citric acid and 65 mL water (twice), dried over Na2S04, and concentrated. Purification of the residue on silica gel, eluting with hexanes/EtOAc (2 3)... 

C.7.3 100 g citric acid (C H Oy) 50 mL sulfuric acid (HySO, sp gr 1.84) 2 g inhibitor (diorthotolyl thiourea or quinoline ethylio-dide or betanaphthol quinoline) Reagent water to make 1000 mL 5 min 60 C ... 

One of the problems encountered with HG arises when analyzing difficult samples. Poor recoveries have been reported for complex matrices, as a result of chemical processes, such as catalytic decomposition of hydrides by transition metals. The use of masking agents (e.g. thiourea, L-cysteine, ascorbic acid, citric acid, and iodide) suppresses hydride decomposition when transition metals are present. " An internal standard (e.g. Ge) can also be used in order to compensate for matrix interferences in samples such as urine. ... 

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