G. Nakagawa

2-(2-thiazolylazo)-4-methyl-5-(sulfomethylamino)benzoic acid as a reagent for the spectrophotometric determination of cobalt

Summary Some 2-(2-thiazolylazo)-5-(sulfomethylamino)benzoic acid derivatives are synthesized. Among them, 2-(2-thiazolylazo)-4-methyl-5-(sulfomethylamino)benzoic acid (TAMSMB) is very sensitive (e = 1.13 × 105 l mol-1 cm-1 at λmax 655 nm) and selective for the spectrophotometric determination of cobalt. The interference of copper and nickel can be eliminated by addition of EDTA after the cobalt(III)—TAMSMB complex has been formed. Cobalt is determined in nickel salts and glass.

Sulfonated 1-(2-pyridylazo)-2-naphthols and 2-(2-pyridylazo)-1-naphthols as spectrophotometric reagents: Determination of nickel

Abstract Three sulfonated 1-(2-pyridylazo)-2-naphthols and six sulfonated 2-(2-pyridylazo)-1-naphthols were synthesized, and their application to the spectrophotometric determination of metals was studied. The acidity constants of the reagents and the stability constants of the nickel chelates are reported, and the relationship between their properties and the position of the sulfonic acid group is discussed. 1-(2-Pyridylazo)-2-naphthol-6-sulfonic acid (PAN-6S) and 1-(2-pyridylazo)-2-naphthol-7-sulfonic acid (PAN-7S) are sensitive and selective reagents for nickel. The determination of nickel in the presence of cobalt with PAN-6S is described. Extraction of the chelate as the ion-pair with tetraphenylarsonium ions into chloroform is suitable for the determination of 1–10 μg Ni at 570 nm; the molar absorptivity is 56 000 l mol -1 cm -1 , and interferences are easily avoided.

Spectrophotometric determination of fluoride with lanthanum/alizarin complexone by flow injection analysis

Abstract Lanthanum/alizarin complexone (1:1) in 70% acetone is used in conjunction with a 500-cm reaction coil at 60°C to determine 0.03–1.2 mg l−1 fluoride at 24 samples per h. The method is applied to tap-water samples.

Synthesis of N-sulfoalkyl derivatives of 2-(2-pyridylazo)-5-aminophenol and the spectrophotometric determination of uranium(IV)

Abstract Six N-sulfoalkyl derivatives of 2-(2-pyridylazo)-5-aminophenol were synthesized. The acidity constants of the reagents and the stability constants of several of their metal complexes were determined. Their application to the spectrophotometric determination of metals in aqueous solution was studied. 2-(3,5-Dibromo-2-pyridylazo)-5-[N-ethyl-N-(3-sulfopropyl)amino]phenol was found to be a highly sensitive reagent for some metal ions. The molar absorptivities (1 mol−1 cm−1) of metal complexes at λmax (nm) are 66 000 (592 nm) for uranium(VI), 138 000 (560 nm) for zinc, 70 000 (558 nm) for copper(II) and 88 000 (568 nm) for iron(II). The effects of various masking agents were examined. The determination of uranium(VI) is described in detail.

Synthesis of o,o′-dihydroxyazo compounds and their application to the determination of magnesium and calcium by flow injection analysis

Seven o,o′-dihydroxyazo dyes were synthesized and examined as spectrophotometric reagents for magnesium and calcium. These reagents are highly sensitive for magnesium (ϵ = 47 000) and calcium (ϵ = 39 000 l mol−1 cm−1). Of the reagents synthesized, 2-(2-hydroxy-3,6-disulfo-1-naphthylazo)-5-(N,N-diethylamino)phenol was the best because of its ease of preparation and purification, and its stability in alkaline solution. This dye was applied in the determination of magnesium and calcium by flow injection analysis. The total concentration of magnesium (0.1–1.2 mg 1−1) and calcium (0.4–4.0 mg 1−1) was determined by masking iron(III), aluminium(III), copper(II), zinc(II), manganese(II) and cadmium(II) with 2,3-dimercapto-1-propanol (DMP) and triethanolamine (TEA). Magnesium was determined by masking calcium and the other metal ions with a ligand buffer containing barium(II)—EGTA, DMP and TEA. The amount of calcium was obtained as the difference between the two peak heights. Results for the determination of magnesium and calcium in potable water and serum are presented.

Effects of manifold components on peak profiles in flow-injection analysis

Abstract The effects of pumps, mixing coils and joints on the peak profiles in flow-injection analysis are described. Four reciprocating pumps, three peristaltic pumps, single coils and double coils with helix diameters of 0.4–3 cm and two types of mixing joint were examined. When pumps yielding small pulsations and double coils with small helix diameter were used, well defined and reproducible peaks were obtained and the effects of mixing joints were small.

Spectrophotometric determination of traces of iron with 2-(3,5-dibromo-2-pyridylazo)-5-[N-ethyl-N-(3-sulfopropyl)amino]phenol and its application in flow injection analysis

Abstract 2-(3,5-Dibromo-2-pyridylazo)-5-[ N -ethyl- N -(3-sulfopropyl)amino]phenol reacts with iron(II) to form a water-soluble chelate, which gives two absorption maxima at 568 nm (ϵ = 88000 l mol −1 cm −1 ) and 748 nm (ϵ = 39000 l mol −1 cm−1). A spectrophotometric determination of 1–35 μg of iron is described. Interferences from other metals are eliminated with N -(dithiocarboxy)sarcosine and EDTA; Cu (15 or 30 μg), Ni (3 or 60 μg), Zn (30 or 130 μg) and Co (20 or 150 μg) do not interfere when the absorbances are measured at 570 nm or 750 nm, respectively. For the flow-injection procedure, the calibration graph is linear for 20–440 μg l −1 iron at 750 nm. Total iron in potable waters can be determined after some preliminary treatment. The sample rate is 30 h −1 .

Spectrophotometric determination of calcium with a flow injection system

Abstract The indirect spectrophotometric determination of 0.8–7.2 ppm calcium in the presence of magnesium, phosphate and sulphate by flow injection analysis (f.i.a.) is described. The method is based on the exchange reaction between the calcium and the zinc complex of ethylene glycol-bis(2-aminoethylether)tetraacetic acid (EGTA) in the presence of 4-(2-pyridylazo)resorcinol (PAR): Ca + Zn(EGTA) + 2 PAR ⇌ Zn(PAR) 2 + Ca(EGTA). A home-made and a commercial flow injection system with a sampling rate of 80 h −1 , are compared. Results for water samples are in good agreement with those obtained by atomic absorption spectrometry.

Synthesis of bidentate pyridylazo and thiazolylazo reagents and the spectrophotometric determination of copper in a flow-injection system

Abstract Some pyridylazo and thiazolylazo compounds were synthesized as spectrophotometric reagents for copper(II). The water-soluble bidentate ligand, 4-(3,5-dibromo-2-pyridylazo)-N-ethyl-N-(3-sulfopropyl)aniline (3,5-diBr-PAESA), provides the greates sensitivity, forming a 1:2 Cu:L in the presence of sodium dodecylsulfate. The molar absorptivity of the complex is 1.24 × 105 l modl−1 cm−1 at 638 nm. Copper(II) (10–200 μg l−1) is easily and quickly (60 h−1) determined in a flow-injection system. Application to the determination of copper(II) in serum is described.

Synthesis of 2-[2-(8-hydroxyquinolyl)azo]-1-naphthol and its use in the spectrophotometric determination of calcium in potable water

Abstract The synthesis of a novel reagent, 2-[2-(8-hydroxyquinolyl)azo]-1-naphthol (HQAN), is described. The acidity constants of the reagent and its reactions with various metal ions are reported. The HQAN reagent forms a soluble calcium chelate in 50% (v/v) dioxane/ water at pH > 8.5 (ϵ = 24 000 l mol −1 cm t-1 at 570 nm). It also forms chelates with magnesium, other alkaline earth metals, and ivalent Mn, Fe, Ni, Cu, Zn, Cd and Pb. These interferences (except for Mn) can be avaoided by pH adjustment or by adding masking agents, and a very simple procedure for the determination of calcium in potable waters is obtained.