Two azo pigments based on β‐naphthol

There has been much discussion in the literature of the azo–hydrazone tautomerism of pigments. All commercial azo pigments with β‐naphthol as the coupling compound adopt the hydrazone tautomeric form (Ph—NH—N=C) in the solid state. In contrast, the red pigments 1‐[4‐(dimethylamino)phenyldiazenyl]‐2‐naphthol, C₁₈H₁₇N₃O, (1a), and 1‐[4‐(diethylamino)phenyldiazenyl]‐2‐naphthol, C₂₀H₂₁N₃O, (1b), have been reported to be azo tautomers or a mixture of azo and hydrazone tautomers in the solid state. To prove these observations, both compounds were synthesized, recrystallized and their crystal structures redetermined by single‐crystal structure analysis. Difference electron‐density maps show that the H atoms of the hydroxyl groups are indeed bonded to the O atoms. Nevertheless, a small amount of the hydrazone form seems to be present. Hence, the compounds are close to being `real' azo compounds. Compound (1a) crystallizes with a herring‐bone structure and compound (1b) forms a rare double herring‐bone structure.     

Determination of sulphonated azo dyes in food by ion-pair liquid chromatography with photodiode array and electrospray mass spectrometry detection

An ion-pair liquid chromatography method with on-line photodiode-array and electrospray mass spectrometry detection was developed to determine 10 commonly used sulphonated azo dyes (Tartrazine, Amaranth, New Coccine, Sunset Yellow FCF, Allura Red AC, Ponceau R, Ponceau 3R, Orange I, Orange II and Metanil Yellow) in food. A reversed phase C(18) column with gradient elution was utilized to separate these compounds. Triethylamine was added in the mobile phase as an ion-pair reagent for chromatographic separation. Photodiode-array detection was employed for quantitative determination and electrospray mass spectrometry was used for identification. Good linearity (0.05-10 ppm, r(2)=0.999) and detection limit (<0.01 ppm) were determined with 5 mul injection. In addition, precision and accuracy associated with this newly developed method will be presented. A liquid extraction method was also developed to extract these dyes from different foodstuffs. The application of this method was demonstrated by analyzing sulphonated azo dyes in soft drinks, fruit jam, and salted vegetables.     

Sulfonyl chlorination of sulfonate-containing naphthol azo compounds

Chlorosulfonyl-containing naphthol azo compounds were prepared by reaction of the corresponding sulfonate-containing naphthol azo dyes with thionyl chloride in the presence of a catalytic quantity of N,N-dimethylformamide and various solvents. The yields and reaction selectivity of chlorosulfonyl-containing naphthol azo compounds were discussed according to the properties of solvents. It was demonstrated that high chemical selectivity and high yield were achieved by using benzene, toluene or thionyl chloride as solvent. Additionally, on account of unstable properties of sulfonyl chloride compounds in MS and ¹H-NMR analyses, a new analytical method using stable sulfonamide is put forward to verify the chemical structures of the corresponding sulfonyl chloride compounds indirectly. __________ Translated from Journal of Dalian University of Technology, 2008, 48(1): 26–32     

Synthesis,characterization, fluorescence imaging,and cytotoxicity studies of a uracil‐based azo derivative and its metal complexes

A uracil‐based heterocyclic azo derivative was prepared by coupling diazotized 5‐aminouracil with 2‐naphthol. This ligand, viz., 1‐(2,4‐dioxopyrimidine‐5‐yl)‐azo‐naphth‐2‐ol (HNAP), was used as a precursor for the synthesis of a series of complexes with manganese(II), cobalt(II), nickel(II), copper(II), and zinc(II) ions. Various physicochemical measurements UV–Visible, Infrared (IR), ¹H NMR, ¹³C Nuclear Magnetic Resonance (NMR), and electron spin resonance (ESR) spectral studies were employed to characterize the ligand and the metal complexes. The ligand showed good selectivity toward Mn²⁺ over the other metal ions with a detection limit of 1.36 μM. This probe was used for the confocal fluorescence imaging of Mn²⁺ ions in Michigan Cancer Foundation‐7 (MCF‐7) cells. The ligand and the metal complexes were tested for their cytotoxicity on the MCF‐7 cell line. It was observed that complexation of HNAP with the metal ions exhibited a promising cytotoxicity.     

Reactions of the synthesis of azo dyes in solidified gelatin gel and their analytical application in the determination of nitrites

The interaction of aromatic sulfonates of azo and diazo components in diazotization and azocoupling reactions electrostatically immobilized on gelatin solidified gel was studied. It was found that, among the variety of the functional groups of the polymer (amino, hydroxy, and carboxy groups and guanidine, phenol, and sulfur-containing amino acid residues), some groups are capable of protonation and are responsible for the efficient electrostatic immobilization of aromatic sulfonates with amino and hydroxy groups. A sufficiently high capacity of the polymer gel causes the formation of a relatively large amount of immobilized compounds, which makes it possible to conduct different types of synthetic analytical reactions of the formation of azo dyes in these gelatin gels in the real-time mode. It was demonstrated that, in all cases, the rate-determining step is external diffusion. These effects were used for the preparation of irreversible sensing elements suitable for measurements of calibration functions using the fixed-time technique or the tangent method in the determination of nitrites in solutions.     

Liquid-Liquid Extraction and Liquid Chromatographic Studies on Interactions of Inorganic Anions with Coordinatively Unsaturated Copper(II) Complexes of Heterocyclic Azo Compounds

The interactions between Cu(II) complexes with heterocyclic azo compounds and several anions were studied by equilibrium analysis of ion-pair extraction, RP-HPLC of metal complexes, and ion chromatography of anions on an ODS column coated with Cu(II) complexes of the long alkyl derivatives. Both ion-pair extraction and HPLC studies demonstrated that a dicationic complex with 8-(3,5-dibromo-2-pyridylazo)-5-aminoquinoline interacted with anions stronger than a monocationic complex with 2-(2-pyridylazo)methylphenol. Anions were more retained on the column coated with dicationic Cu(II) complex. Such differences were quantitatively ascribed to the first ion-pair formation of the dicationic complex giving a monocationic species.     

IPC behaviour of some sulphonated naphthols and nitroso-naphthols

Summary The ion-pair chromatographic behaviour of a naphthol and some sulpho-substituted naphthols and nitroso-naphthols is studied. Formation of the ion-pair compounds is done either by pre-extraction or during elution with long-chained quaternary alkyl- or alkylarylammonium salts. Identification is based in UV/VIS absorption using a diode array detector at 229, 240, 254 or 280 nm. Special emphasis is placed on the column material, the positions of the substituents in the naphthols and the organic ion-pairing agents in the eluent.

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IPC-Verhalten einiger sulfonierter Naphthole und Nitrosonaphthole

     

Determination of aromatic sulfonates in the river Elbe by on-line ion-pair extraction and ion-pair chromatography

An automated method based on ion-pair extraction and HPLC has been used to investigate the occurrence of aromatic sulfonates in the river Elbe. Twelve different naphthalene, anthraquinone and stilbene sulfonates have been found. The substances have been detected by UV detection at 220 nm and, if possible, by their fluorescence signal. The aromatic sulfonates have been identified by their retention time and by comparing their UV spectra with the respective spectra of reference substances. The occurrence of these substances in the river Elbe water is caused by a discharge of several waste water effluents. The results showed, that certain naphthalene sulfonates cannot be totally removed by biological treatment and adsorption on activated carbon.     

Supramolecular motifs in s-block metal-bound sulfonated monoazo dyes, part 1: structural class controlled by cation type and modulated by sulfonate aryl ring position

The solid-state structures of 43 Li, Na, K, Rb, Mg, Ca and Ba salts of para- and meta-sulfonated azo dyes have been examined and can be categorised into three structural classes. All form alternating organic and inorganic layers, however, the nature of the coordination network that forms these layers differs from class to class. The class of structure formed was found to be primarily governed by metal type, but can also be influenced by the nature and position of the organic substituents. Thus, for the para-sulfonated azo dyes, Mg compounds form solvent-separated ion-pair solids; Ca, Ba and Li compounds form simple coordination networks based on metal-sulfonate bonding; and Na, K and Rb compounds form more complex, higher dimensional coordination networks. Compounds of meta-sulfonated azo dyes follow a similar pattern, but here, Ca species may also form solvent-separated ion-pair solids. Significantly, this first attempt to classify such dyestuffs using the principles of supramolecular chemistry succeeds not only for the simple dyes used here as model compounds, but also for more complex molecules, similar to modern colourants.     

Synthese de substances macromoleculaires renfermant des motifs monomeres derives de colorants—XVIII: Synthese d'oligoamides colores par structure

Oligoamides with amino end-groups have been reacted with acid chlorides of azo or quinophthalic dyes. Oligoamides with 4-nitro phenyl end-groups have been reduced to oligoamides with aminophenyl end-groups; they have been diazotized and coupled with β naphthol. Due to their low thermal stability, oligoamides containing azo groups cannot be spun; on the other hand, oligoamides with quinophthalic groups can be used as macromolecular dyes for polyamides. Coloured fibres have excellent mechanical properties and the dye cannot be extracted by solvent.     

Epoxy-based azo molecular glasses with four-arm architecture: Preparation,characterization and holographic recording

A series of epoxy-based azo molecular glasses with four-arm architecture was synthesized, characterized and applied to holographic recording.     

Sensitive high-performance liquid chromatographic determination of ionic drugs in biological fluids with short-wavelength ultraviolet detection using column switching combined with ion-pair chromatography: application to basic compounds

A highly sensitive and selective high-performance liquid chromatographic method with short-wavelength UV detection is described for the determination of ionic compounds in biological fluids, which was applied to two basic compounds, 2-(3-[4-(4-fluorophenyl)-1-piperazinyl]propyl)-6,7,8,9-tetrahydro-2H-nap htho [2,3-b][1,4]oxazin-3(4H)-one (I) and methyl 2-(4-diphenylmethyl-1-piperazinyl)ethyl (+/-)-1,4-dihydro-2,6-dimethyl-4-(m-nitrophenyl)-3,5-pyridinedicarboxyla te (II), in human serum. The method is based on the combination of the column-switching technique and ion-pair chromatography. In the first ODS column, the analyte is pre-separated from endogenous substances in serum by ion-pair chromatography. After column switching, in the second ODS column the heart-cut fraction containing the analyte is further separated by non-ion-pair chromatography from coeluted endogenous substances from the first ODS column. The proposed method offered high sensitivity and selectivity with UV detection at 215 nm for I and 230 nm for II. The detection limits were 0.2 ng/ml for both I and II using 1 ml of serum. The principle of the proposed method would be applicable to both acidic and basic compounds in biological fluids with a suitable ion-pair reagent.     

Liquid chromatography-mass spectrometry and strategies for trace-level analysis of polar organic pollutants

Liquid chromatography–mass spectrometry using atmospheric pressure ionization (LC–API-MS) has drastically changed the analytical methods used to detect polar pollutants in water. The present status of application of this technique to organic water constituents is reviewed. The selection of the appropriate LC conditions, whether reversed-phase liquid chromatography, ion-pair chromatography, capillary electrophoresis or ion chromatography, and of the most sensitive ionization mode, electrospray ionization (ESI) or atmospheric pressure chemical ionization (APCI), depends upon the polarity and acidity of the analytes. Strongly acidic compounds such as aromatic sulfonates, sulfonated dyes, haloacetic acids, linear alkylbenzene sulfonates, aliphatic sulfonates and sulfates and complexing agents, weakly acidic compounds such as carboxylates and phenols, neutral compound classes, namely alkylphenol ethoxylates, alcohol ethoxylates and polycyclic aromatic hydrocarbons and the basic toxins, quaternary ammonium compounds and organometallic compounds are considered. The selection of the mass spectrometer depends upon the analytical task: triple-quadrupole mass spectrometers are highly suited for sensitive quantitation and for qualitative analyses, ion traps are especially suited for structure elucidation, whereas time-of-flight mass spectrometers and quadrupole time-of-flight mass spectrometers with their higher mass resolution are ideal for the determination of molecular formulas of unknown compounds and for screening purposes. While large steps have already been made, future efforts with respect to water analysis may be directed at fine-tuning the methodical arsenal for increased sensitivity and selectivity and to extend LC–MS application to transformation products.     

Coated-wire organic ion-selective electrodes in titrations based on ion-pair formation : Determination of arenediazonium salts with sodium tetraphenylborate

Titrimetric determinations of arenediazonium salts can be based on ion-pair formation between the diazonium cation and tetraphenylborate. Titrations are done under cooling with ice and are followed potentiometrically with organic ion-selective electrodes comprising PVC membranes plasticized with polar solvents and coated on aluminium wires. The method was tested in determinations of arenediazonium salts derived from 20 aromatic amines, including aniline, toluidines, naphthylamines and their derivatives. Except for compounds containing hydrophylic groups such as —COOH and —OH, the potentiometric titration curves have well defined end-points. The results are reproducible, with relative standard deviations in the range 0.4–1.4% at the millimolar level. The method can be used for reliable determinations of arenediazonium salts in analytical control of azo dyestuff production.     

Extraction—spectrophotometric determination of boron with 2,6-dihydroxybenzoic acid and 4-(4-diethyl-aminophenylazo)-n-methylpyridinium iodide,with application to steels

The sensitive and selective method reported is based on the reaction of boric acid with 2,6-dihydroxybenzoic acid in acidic aqueous solution to form a 1:2 complex anion which can be extracted into chloroform as an ion-pair with 4-(4-diethylaminophenylazo)-N-methylpyridinium ion. The ion-pair formed by the excess of reagents and co-extracted into chloroform, is removed by washing the organic phase with phosphate buffer solution (pH 7.0) and 0.025 M sulfuric acid solution. The absorbance of azo dye in chloroform is measured at 570 nm. Calibration graphs are linear in the range 0–1.5 × 10^-5 M of boron. The molar absorptivity is 6.6 × 10⁴ l mol^-1 cm^-1 and the absorbance of the reagent blank is 0.030. The method was applied to the determination of boron at the 0.001% level in steels.     

Heterocyclic diazo compounds. 5. Reaction of benzimidazole-2-diazonium salts with naphthols and their ethers

The principal pathways for the reaction of benzimidazole-2-diazonium ion salts with naphthols and their methyl ethers in a mixture of phosphoric acid annd acetic acid have been elucidated. In concentrated acidic media, in addition to substitution at the 4-position in naphthol and its ether, azo coupling at the 8-positin is also possible. It has been found that a 2-methoxy group in naphtylazobenzimidazole exhibits anomalously high reactivity with respect to hydrolytic cleavage, which explains the observed ease of dealkylation of the azo compound during the course of the azo coupling sequence.For Communication No. 4, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 67–72, January, 1992.     

Structural and Thermal Studies on the Ion-pairs [Co(NH3)6]5[HV10O28]3·18H2O and [Co(NH3)6][V2O6OH]

Two cobalt hexammine-vanadate ion-pair complexes have been prepared; one in acid medium (pH≈4) and the other in alkaline medium (pH≈10). The formed complexes were characterized by their elemental analysis, IR and XRD techniques. The complexes were subjected to thermogravimetric and differential thermal analyses. The IR study suggests that the formed complexes were of the ion-pair type, while that of the thermally decomposed compounds revealed the resolution of the originally present broad V=O and V-O-V bands. This revised version was published online in July 2006 with corrections to the Cover Date.     

Decolorization of Naphthol Blue Black using the Horseradish Peroxidase

This study evaluates the potential of the enzyme horseradish peroxidase in the decolorization of one common industrial azo dye, naphthol blue black. Studies are carried out to understand the process parameters such as pH, temperature and reaction time. The enzymatic decolorization of the dye was examined by UV-Vis spectrophotometer and LC-MS measurements. Temperature and pH conditions were optimized for obtaining high azo-dye decolorization. Azo-dye removal at a pH range 4-6 was found to be the highest for all temperatures. After 5 minutes of treatment, the color removal of dye was ca. 80-90%. The LC-MS and spectrophotometric analyses indicated that the decolorization of the azo dye with enzyme was due to the reduction of the azo bonds. This study verifies the viability of the use of the horseradish peroxidase in the decolorization of naphthol blue black.     

碱金属和碱土金属离子在反相高效液相色谱柱上的保留机理

发现以酒石酸和吡啶二甲酸等羧酸水溶液作淋洗剂时，钠，铵，钾，镁和钙等碱金属及碱土金属离子在ＯＤＳ反相高效液相色谱柱上有明显的保留，而且相互之间能达到一定程度的分离。单独用分配或疏水作用等反相高效液相色谱的保留机理难以解释其保留行为。为此，作者提出了动态包固定相机理，即认为羧酸根阴离子因其疏水性在ＯＤＳ固定相有保留，在固定相表面形成具有羧酸基阳离子交换树脂功能的动态包覆固定相。     

Dispersionsazofarbstoffe auf Aminobenzimidazolon-Basis

New dispersion azo dyes were prepared on the basis of 5-amino- and 5,6-diaminobenzimidazolone by diazotisation and coupling, esp. with -naphthol and naphthol AS. The new compounds are suitable for dying of polyamide, polyester, polyacrylonitrile and acetate fibers in pink, orange, brown and red-violet colours.