Dihydroxynaphthalenes determination

Calcium in the 10-500ng range can be determined by using the selective spectrofluorimetric reagent l,5-bis(dicarboxymethyl-aminoethyl)2,6-dihydroxynaphthalene at pH 11.7 (Ref. 32). 

Unique methods based on new principles have been developed within the past 10 years. Threonine (27,28,249) is oxidized by lead tetraacetate or periodic acid to acetaldehyde, which is determined by photometric analysis of its p-hydroxydiphenyl complex or iodometric titration of its combined bisulfite. Serine is oxidized similarly to formaldehyde, which is determined gravimetrically (207) as its dimedon (5,5-dimethyldihydro-resorcinol) derivative or photometric analysis (31) of the complex formed with Eegriwe s reagent (l,8-dihydroxynaphthalene-3,5-disulfonic acid). It appears that the data obtained for threonine and serine in various proteins by these oxidation procedures are reasonably accurate. [Block and Bolling (26) have given data on the threonine and serine content of various proteins. ]... 

The rate constants in Figure 5-3 were measured by injecting the solution of the (E)-diazoate into a buffer solution that also contained a highly reactive coupling component (2-naphthol-3,6-disulfonic acid, except at pH values below 2.5, where l,8-dihydroxynaphthalene-3,6-disulfonic acid was used instead). The diazonium ion formed reacts rapidly with these naphthols, and the concentration of the corresponding azo compounds was determined spectrophotometrically. 

Al-Ghannam et al. [25] described a simple fluorimetric procedure for determination of three pharmaceutical compounds containing thiol groups, including penicillamine. In this method, the drugs are treated with 1,2-naphthoquinone-4-sulfonic acid. The later compound is reduced to l,2-dihydroxynaphthalene-4-sulfonic acid, which is measured fluorimetrically (excitation = 318 nm, emission = 480 nm). The method is sensitive to 0.5 1.5 pg/mL, with a detection limit of 0.05 pg/mL (S/N = 2). 

Among the Ti02 powders, P25, which contains a 30% rutile phase and has a 43 m2/g surface area, showed the highest activity, as shown in Fig. 11.8. In this system, only three kinds of oxidized compounds (2-formylcinnamaldehyde and 1,3- and 1,4-dihydroxynaphthalene) among 10 possible isomers were obtained.81) Furthermore, no mono-hydroxylated compounds, i.e., 1- and 2-naphthol. were detected in the reaction products. Quantum efficiencies of the reactions were determined at around 365 nm. After photoirradiation for 1 h, the quantum efficiencies were determined to be 14.6% and 5.8% for the production of 2-formylcinnamaldehyde and 1,3-dihydroxynaphthalene, respectively. The efficiency was determined on the assumption that 4 holes are necessary to form one oxidized naphthalene molecule. 

Arsenazo I and a number of its analogues are derivatives of chromotropic acid (1,8-dihydroxynaphthalene-3,6-disulphonic acid). Arsenazo I is applied to the determination of rare earths, Th, U, Zr, Ti, Nb, and other metals. 

Iron in silicate rocks was determined with the use of 2,3-dihydroxynaphthalene [16,17]. 1,5-Bis(di-2-pyridylmethylene) thiocarbonohydrazide in DMF was used as a reagent to determine Fe (Co, Ni and Cu) by calculation of first- and second derivatives [18]. The method was applied to the determination of the metal ions in alloys and biological materials. 

Photometric determination. Formaldehyde yields a red-violet colour with chromotropic acid (l,8-dihydroxynaphthalene-3,6-disulphonic acid) in concentrated sulphuric acid, its intensity being proportional to the concentration of formaldehyde. The measurement is made at 560 nm [23]. 

Eskinja, M. Zollner, P. Schmid, E. R. Determination of mercapturic acids using 1,4-dihydroxynaphthalene, a new matrix for matrix-assisted UV laser desorption/ ionization mass spectrometry. Eur. Mass Spectrom. 1998, 4, 157-162. 

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