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Two methods utilizing the complexation of labile Al species by 8-hydroxyquinoline (HQN) and salicylic acid (SA) ligand groups were developed for aluminium operationally defined fractionation in acid soils. First, the solid phase extraction (SPE) procedure by a short-term ion-exchange batch reaction with chelating resins Iontosorb Oxin and Iontosorb Salicyl containing both ligand groups was used previously. Second, the 8-hydroxyquinoline, salicylic acid and ammonium salicylate agents with different concentrations by a single extraction protocol were applied in this paper. The flame atomic absorption spectrometry (FAAS) and optical emission spectrometry with inductively coupled plasma were used for aluminium quantification. The comparison of results from both methods show the possibility to supersede the first laborious method for the second simpler one in Al environmental risk assessment. The use of 1% 8-hydroxyquinoline in 2% acetic acid and 0.2% salicylic acid by a single extraction protocol without a need of sample filtration can supersede the SPE procedure in the Al pollution soil monitoring. Finally, the new scheme usable in a laboratory and moreover, directly in a field was proposed for Al fractionation in solid and liquid environmental samples. The labile Al species in soils and sediments are separated after their single leaching by 8-hydroxyquinoline or salicylic acid without a need of sample filtration. The labile Al species in soil solutions and natural waters are separated after their ultrafiltration followed by the SPE procedure with Iontosorb Oxin or Iontosorb Salicyl.

A simple dispersive solid-phase micro-extraction method based on CoFe2O4 nano-particles (NPs) functionalized with 8-hydroxyquinoline (8-HQ) with the aid of sodium dodecyl sulfate (SDS) was developed for separation of Al(III) ions from aqueous solutions. Al(III) ions are separated at pH 7 via complex formation with 8-HQ using the functionalized CoFe2O4 nano-particles sol solution as a dispersed solid-phase extractor. The separated analyte is directly quantified by a spectrofluorometric method at 370nm excitation and 506nm emission wavelengths. A comparison of the fluorescence of Al(III)-8-HQ complex in bulk solution and that of Al(III) ion interacted with 8-HQ/SDS/CoFe2O4 NPs revealed a nearly 5-fold improvement in intensity. The experimental factors influencing the separation and in situ monitoring of the analyte were optimized. Under these conditions, the calibration graph was linear in the range of 0.1-300ngmL(-1) with a correlation coefficient of 0.9986. The limit of detection and limit of quantification were 0.03ngmL(-1) and 0.10ngmL(-1), respectively. The inter-day and intra-day relative standard deviations for six replicate determinations of 150ngmL(-1) Al(III) ion were 2.8% and 1.7%, respectively. The method was successfully applied to direct determine Al(III) ion in various human serum and water samples.

This paper presents a study of quiescent microdialysis sampling of Cr 3+ , Cu 2+ , Ni 2+ and Pb 2+ involving the incorporation of poly- l -aspartic acid, poly- l -histidine, 8-hydroxyquinoline (8-HQ) and ethylenediaminetetraacetic acid (EDTA), in the perfusion liquid as an approach to maximise metal analyte flux across the microdialysis membrane. These chelating agents were individually optimised with respect to microdialysis recovery and subsequently combined in the perfusion liquid. A combination of 20% (w/v) poly- l -histidine, 0.032% (w/v) poly- l -aspartic acid and 1 mM 8-HQ achieved microdialysis recovery up to 90%. Since 1 mM EDTA achieved recoveries greater than 80% for all metals understudy, EDTA was not combined with any of the chelating agents. Under the optimal conditions of maximum metal ion flux across the microdialysis membrane, metal ions from natural and wastewater were sampled and analysed with an electrothermal atomic absorption spectrometer equipped with a Zeeman background corrector. Results showed higher concentrations of detected metal ions after microdialysis sampling compared to direct detection without sample clean-up. Incorporation of chelating agents in the microdialysis perfusion liquid enhanced metal ions recovery in real samples and achieved enrichment factors of up to 42. The study demonstrated that combining chelating agents is a good approach towards maximising metal flux across the dialysis membrane. Given that recoveries between 80 and 90% were achieved under quiescent microdialysis sampling conditions, these findings are an important development for in vivo diagnostic sampling of metal ions.

The sensitizing effect of cetyltrimetrylammonium bromide (CTAB) microemulsion media on the determination of aluminium(III) by spectrofluorimetry was developed. The main factors affecting the determination were investigated in detail. The results showed that 8-hydroxyquinoline (HQ) react with aluminium(III) forming a complex with fluorescence in the system of potassium acid phthalate–NaOH buffer solution at pH 6.0, the maximum excitation and emission wavelengths are at 380.0 and 502.6 nm, the sensitizing effect of CTAB microemulsion is higher than that of CTAB micelle. The proposed method has been applied to the determination of aluminium(III) in tap water and lake water samples with satisfactory results.

This study describes the functionalization of biopolymer chitosan, using the complexing agent 8-hydroxyquinoline (oxine) by reaction of diazotization. The chelating resin was characterized by degree of deacetylation, infrared, Raman spectroscopy. The efficiency of the chelating resin and accuracy of the proposed method was evaluated by the metal ion recovery technique in the analysis of potable water, lake water, seawater and a certified sample of oyster tissue. The metal ions Cd(II) and Cu(II) in the samples were previously enriched in a minicolumn and flow injection flame atomic absorption spectrometry (FI-FAAS) determined the concentrations of the analytes. The chelating resin exhibited high selectivity for Cd(II) at pH 7 and for Cu(II) at pH 10. The eluent concentration was tested by the use of HNO 3 in concentrations of 0.1–3 mol l −1 maximum response was obtained at 0.5 mol l −1 for Cd(II) and Cu(II), with R.S.D. values of 0.4%. The analytes gave relative standard deviations (R.S.D.) of 1.5 and 0.7% for solutions of Cd(II) and Cu(II), respectively ( n = 7) containing 20 μg l −1 of the metal ions, defining a high reproducibility. The limits of detection (LOD) were 0.1 μg l −1 for Cd(II) and 0.4 μg l −1 for Cu(II). The analytical properties of merit were obtained using the parameters previously optimized with preconcentration time of 90 s. The chelating resin showed chemical stability within a wide range of pH and the efficiency was not altered for the preconcentration of the metal ions during all the experiments.

A novel strategy for the speciation of aluminum has been developed by fluorometry using selective analytical reagents under different pH conditions, which is based on the measurement of the complexation ability of Al for analytical reagents and native organic matters. With Eriochrome Blue Black R, labile monomeric Al and total monomeric Al fractions are determined at pH 4.5 and pH 8.0, respectively. With morin only the labile monomeric Al is determined at pH 4.0, while with 8-hydroxyquinoline the total monomeric Al is determined at pH 5.5. So, acid soluble Al fraction is obtained indirectly. This method is successfully applied to the fractionation of Al in natural waters. The results well agree with those obtained by Driscoll’s 8-hydroxyquinoline/cation-exchange protocol. This fluorometric method possesses some advantages such as high sensitivity, easy manipulation, no separation step and less time-consuming.

A novel method for the speciation of chromium(III) and chromium(VI) by in situ separation and sequential determination with electrothermal vaporization-inductively coupled plasma-atomic emission spectrometry (ETV-ICP-AES) was developed. The reaction conditions between Cr(III) and 8-hydroxyquinoline (8-Ox) and the vaporization behavior of the chelate formed were investigated in detail. It was found that the Cr(III)-8-Ox chelate could be formed at room temperature and vaporized from graphite furnace under controlled experimental conditions, therefore, an in situ separation of Cr(III) from Cr(VI) was achieved. The retained Cr(VI) in graphite tube was then determined by using fluorination vaporization ETV-ICP-AES with PTFE slurry as chemical modifier. Under optimum experimental conditions, the detection limits for Cr(III) and Cr(VI) are 8.6 ng/ml and 11.3 ng/ml, and the relative standard deviations (R.S.D.s) are 3.8% and 4.1% ( c =0.1 μg/ml, n =6), respectively. The linear ranges of the calibration curve for both Cr(III) and Cr(VI) covered three orders of magnitude. The proposed method has been applied to the speciation of Cr(III) and Cr(VI) in water samples with the satisfactory results.

Copper complexation in freshwater was investigated by cathodic stripping voltammetry (CSV) with ligand competition using 8-hydroxyquinoline (oxine). Complexing capacity titrations were used to determine concentrations of natural copper complexing ligands and their conditional stability constants. The effect of the adsorption potential on the determination of copper complexation was studied at three potentials of −0.15, −0.7 and −1.1 V. It was found that the detected complexing ligand concentrations decreased from 6.7 to 69.4% when the potential used was more negative than −0.15 V. The decrease was greater at more negative potentials and lower detection windows. Detailed measurements of copper complexation in freshwater were carried out at three detection windows by varying the oxine concentrations from 7.3 to 36.7 μM and confirmed the presence of several complexing ligands. The detected complexing ligand concentrations were found to decrease with increasing detection window, whereas the conditional stability constants were found to increase. These findings confirm that a spectrum of natural complexing ligands exist in freshwater with weaker ligands being determined at lower detection windows and stronger ligands being determined at higher detection windows. A good linear relation was found between log α CuL x and log α Cuox .

A derivative of 8-hydroxyquinoline (8-quinolinol, oxine) with a linking bridge containing a carboxylic group was covalently coupled to bovine serum albumin by the N-hydroxysuccinimide method to obtain stable monomeric conjugates with oxine to protein mole ratios up to 37. These conjugates were characterised spectrophotometrically and their complexation properties were confirmed by spectral analysis with and without the addition of Al(III), Cd(II), Co(II), Cu(II), Hg(II), Mn(II), Ni(II), Pb(II), V(IV), U(VI) and Zn(II) ions added. The maximum number of ions bound by these chelating proteins was determined spectrophotometrically by titration with metal ions at pH 6.0. The conjugates with a substitution ratio (moles of 8-hydroxyquinoline bound/mole of albumin) less than about 8 showed 1:1 binding with metal ions, while conjugates with higher substitution ratios were able to complex with 2:1 ratio of 8-hydroxyquinoline to metal ion. Association and dissociation kinetics of complexation with copper(II) ions showed a complex mechanism. The spectral and binding properties of these metal ion-binding proteins confirm that the coupling of the 8-hydroxyquinoline derivative to bovine serum albumin gives stable, water soluble, macromolecular chelating agents that retain the complexing ability of the original ligand.

A method has been developed for the determination of aluminium and other metal ions (Ca, Mg, Zn, Cd) in aqueous samples. The metal ions are separated as the free cations by capillary electrophoresis. A solution of 8-hydroxyquinoline-5-sulphonic acid (HQS) is added post column to mix with the separation buffer. The resulting HQS complexes could be detected by their fluorescence. The influence of the pH of the separation buffer and the post-column reagent has been studied. For Al and Zn low-pH values were required, while for Ca and Mg a pH of 8–9 for the reagent was optimal. The fluorescence intensities could be increased approximately three-fold by adding 20% (v/v) dimethylformamide to the reagent. Under optimised conditions detection limits in the low μg l−1 level (approx. 0.1 μmol l−1) were obtained. The repeatability of the peak areas was from 1.4% at high concentration to 8.4% at a concentration of 0.25 μmol l−1. The speciation of aluminium ions in the presence of fluoride was studied.

8-hydroxyquinoline immobilized on fluorinated metal alkoxide glass (MAF-8HQ) was prepared under metal-free conditions and used for the separation of trace elements from seawater matrix. Trace elements in 250 ml of seawater were collected with a MAF-8HQ column (bed volume, 0.85 ml; total exchange capacity, 5.2 mg for Cu (II)), eluted with 25 ml of 0.5 M nitric acid and determined by the high-resolution inductively coupled plasma mass spectrometry (HR-ICP-MS). This procedure allowed the determination of V, Co, Ni, Ga, Y, Mo, Cd, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, W and U, of which the concentrations ranged over six orders (10 μg–0.01 ng l −1 ). The precision was less than 10%. The detection limit of most elements depended not on the performance of HR-ICP-MS but on the level of contamination.

A method has been developed for the determination of endogenous levels of aluminium (>1 μ l −1 ) in water samples using an automated on-line preconcentration system with flow injection coupled directly to an electrothermal atomic absorption spectrometer. Two preconcentration materials, 8-quinolinol immobilized on controlled-pore glass (8-Q-CPG) and Amberlite XAD-2, poly(styrene/divinyl benzene) copolymer (XAD-2) were investigated and compared. Both systems were found to be suitable for preconcentration. However, the sampling flow-rate for the 8-Q-CPG system was found to be much lower than that of the XAD-2 system, relative to the same magnitude of preconcentration. The chelating kinetics of the 8-Q-CPG system were less favourable than the adsorption kinetics of the XAD-2 system. The detection limits (3SD) varied from 15 to 40 ng l −1 , depending on the preconcentration time, with RSDs of the order of 4% for a 1 μg l −1 concentration of aluminium. The optimum concentration range for the application of the method developed was 50 ng l −1 to 3 μg l −1 . Recoveries for drinking water were in the range 100–115% for the 8-Q-CPG system and 90–100% for the XAD-2 system. The method developed was applied with varying results to the analysis of potable, fresh, river and sea water samples.

The affinity of glycine for a chromatographic resin modified by covalent attachment of a complex of 8-hydroxyquinoline with Pd(II) was evaluated. The loading capacity of the resin for Pd(II) and the corresponding reaction equilibria were determined. Experimental, as well as theoretical studies, for the processes of partition and elution of the amino acid were also undertaken. It was found that for both the partition and elution processes, theoretical predictions based on equilibrium reactions confirmed the experimental data. This study demonstrates that a soft metal, Pd(II), immobilized on a chromatographic resin through its interaction with 8-hydroxyquinoline, can be used to adsorb and elute the amino acid glycine. This could serve as a model for the separation of amino acids based on immobilized soft-metal affinity chromatography principles.

A rapid and sensitive differential-pulse adsorptive stripping voltammetric method, based on the formation of an electroactive complex between aluminium(III) and 8-hydroxyquinoline (HOx), is presented for the determination of trace levels of aluminium. The complex showed an oxidative peak potential at +0.876 V vs. Ag/AgCl (saturated KCl) at a glassy carbon (GC) electrode in aqueous ammonium acetate (0.024 M, pH 6.8. A good linear relationship between the peak current and Al(III) concentration in the ranges 4.00 X 10 −8 –5.00 X 10 −6 and 8.00 X 10 −6 –4.00 X 10 −5 M were observed. In the lower Al(III) concentration region, the anodic peak was the result of the stripping of the absorbed Al(III)-HOx complex, whereas in the higher concentration range, the diffusional oxidation current of the solution species predominated. A surface saturation region was observed from 5.00 X 10 −6 to 8.00 X 10 −6 M Al(III). Relatively few interferences were found and these were easily masked. The detection limit for Al(III) for this method is 1.00 X 10 −8 M and ten determinations of Al(III) at 1.00 X 10 −7 M gave a relative standard deviation of 6.2%. The method was employed in the analysis of Al(III) in a US Environmental Protection Agency water pollution quality control sample (WP 386) and excellent agreement with the certified value was obtained.

A selective on-line trace enrichment technique for doxorubicin in plasma based on complex formation between iron(III) and the analyte is described. Fe(III) immobilized on 8-hydroxyquinoline (HO)-bonded silica was used as a solid support for the enrichment of doxorubicin. Sorption of the analyte on the iron(III)-loaded HQ-silica (FeHQ-silica) was investigated as a function of pH, flow-rate, content of organic modifier and ionic strength. Desorption was based on protonation of doxorubicin and simultaneous removal of Fe(III) from the HQ-silica. Efficient on-line desprotion to the C 18 analytical column was achieved by injecting a plug of nitric acid solution on to the FeHQ-silica precolumn. Desorption was optimized by determining the recovery of doxorubicin as a function of the acidity and the volume of the nitric acid plug. An example of the determination of doxorubicin in plasma is presented.

The determination of Mo(VI) by differential-pulse voltammetry based on catalytic currents in nitrate medium is described. The existence of catalytic currents in the system Mo(VI)NO 3 − in the presence of 8-hydroxyquinoline was proved by various polarographic techniques. The optimum background electrolyte is 20 ml 0.5 M KNO 3 −0.005 M HNO 3 with the addition of 1 ml of 1 × 10 −2 M 8-hydroxyquinoline. The detection limit is 7 × 10 −10 M under these conditions. Cr(VI), Cu(II), Cd(II) and Pb(II) interfere when present at higher concentrations then Mo(VI) and W(VI) interferes at an equal concentration to Mo(VI). The method was successfully used in analyses of environmental samples.

8-Hydroxyquinoline (HQ), 2-methyl-8-hydroxyquinoline (CH3-HQ), 5,7-dichloro-2-methyl-8-hydroxyquinoline (Cl2-CH3-HQ), 5,7-dibromo-8-hydroxyquinoline (Br2-HQ), 5-sulfo-7-iodo-8-hydroxyquinoline (ferron) and 5-sulfo-8-hydroxyquinoline (SO3H-HQ) were compared as chelating reagents for on-line sorption preconcentration of cobalt in a knotted reactor (KR) precoated with the reagent. The results obtained with the different HQ derivatives reveal those properties of the chelating reagent responsible for the processes taking place in the KR. The influence of hydrophobicity, acidity, stability of the cobalt chelate and type of substituents in the HQ ring system on the separate steps of the flow injection (FI) preconcentration procedure are discussed. According to the performance characteristics of the different HQ derivatives, the most important parameters for on-line preconcentration in a KR are the hydrophobicity of the reagent and the stability of the chelate complex with the analyte.

The preparation of oxine-containing ion-exchange resins has been treated rigorously. The reactant ratios, nature of cure, degree of cross-linking and hydrophilicity have been evaluated in terms of metal capacity and kinetics of metal uptake. The preparation of a bead polymer with good physical properties is described; stability tests show that the gel polymers must never be allowed to dry, otherwise their advantageous properties are destroyed. Stability towards acids in re-cycling procedures is excellent in terms of metal capacity, but there is some loss in water regain which equates to a slower equilibration rate with constant use.

Aluminum reacts with 8-hydroxyquinoline-5-sulphonic acids (HQS) in cationic micelles of cetyltrimethylammonium bromide (CTAB) to form a strongly fluorescent compound. In the micellar media the formation of the Al—HQS complex is very fast, allowing a useful continuousdetermination of aluminum in flow systems. At pH 6.3, for 2 × 10 -4 M HQS and 2 × 10 -3 M CTAB the detection limit for a luminum by flow injection is 0.1 ng ml -1 . The calibration is linear up to 100 ng ml -1 and the peak-height precision is 2% at the 10 ng ml -1 level. Interfences are greatly decreased compared with the batch method. The reaction has also been applied to the post-column detection by ion chromatography of aluminium in fresh and high-salinity wates and for speciation of aluminium in blodd serum after separation of serum proteins by ion-exchange liquid chromatography.

The behaviour of the silicone rubber-based copper(II)-selective electrode in the presence of complexing agents is discussed. The electrode shows well defined responses to several complexing agents in solutions practically free of copper(II) ions. Titrimetric determinations of citrates and 8-hydroxyquinoline with potentiometric end-point detection are described.

Instrumental neutron activation analysis of biological and environmental samples suffers from interferences caused by high salt concentrations. Poly-5-vinyl-8-hydroxy-quinoline coated on controlled pore diameter glass beads is suggested as a chelating column for the rapid removal of aluminum, vanadium, copper and manganese from neutron-activated sea-water samples. Separation from bulk elements is satisfactory at flow rates of 20 ml min−1. With addition of carriers and with chemical yield determinations, relative standard deviations of 2–10% can be achieved for spike concentrations of 0.1 μg Mn ml−1, 0.3 μg V ml−1, 20 μg Al ml−1 and 1.0 μg Cu ml−1.

The behavior of the polarographic maximum of the cobalt—8-hydroxyquinoline system in ammonia-ammonium chloride buffer has been studied with regard to general morphology, effect of mercury flow rates, current—time curves and streaming patterns under carefully controlled conditions. The maximum appears to be an adsorption-controlled catalytic maximum. Current—time curves and streaming observations provide useful information in its characterization. Difficulties in distinguishing the first-kind negative maxima from catalytic maxima are discussed.

Vanadium(IV) at concentrations of 10-2–10-4 M can be titrated at pH 5–6; the 1:2 metal—ligand complex is formed. Back-titrations with copper(II) solution and reverse titrations are also feasible. Absorbances are measured at 385 nm.

The preparation and properties of chelating resins containing the oxine group have been studied. Condensation resins with the optimal swelling properties were made by control of the water content during curing. The resins have high capacity and selectivity, and a fast exchange rate resulted from the incorporation of a proportion of sulphonic acid groups. A resin of this type was used for rapid column separations. Polystyrene-based resins of the gel-type were less satisfactory.

The ligand, 8-hydroxyquinoline-5-sulfonic acid, forms anionic complexes with cobalt(II), zinc(II), cadmium(II), and lead(II), each resulting complex showing a high affinity for anion-exchange resins. The effect of pH, ligand/metal ratio, volume, and concentration on percent retention of the anionic complexes by an anion-exchange resin are reported. At optimum conditions, all four metals are quantitatively retained by the column. Zinc, cadmium and lead(II) ions are completely eluted with 11 ml or less of 2 M HN03; cobalt(II) is totally removed by 12 M HCl and 2 M HNO3. Concentration enhancements of 100-fold are easily achieved. All four anionic complexes can be left on the column for 7 days and still be quantitatively (99%) recovered. A ligand-loaded resin column can also remove all four metals quantitatively. Distribution coefficients for the metal complexes and their ligand/metal ratios were determined by using batch methods that may also serve as the isolation procedure.

The oxine-containing chelating ion-exchangers described in the literature have been synthesized and their properties determined. Total capacities for copper, cobalt, nickel, zinc, aluminium and uranyl ions as a function of pH are given, together with equilibration rates and swelling properties. Detailed analysis of the various exchangers has shown that other factors are responsible for chelation in addition to the oxine groups present. Column separations on one exchanger, with a specific method for uranium isolation, are described.

As a result of the study of the chemical behaviour of some metallo-oxinates it is shown that : 1. A fluorescence test can be used to detect the presence of calcium, magnesium and aluminium in paper. The test is made by spotting the paper or its ash with a solution of oxine and examining tlie spot in the ultraviolet light. 2. A test for a fluoridc can be based on the inability of a qualitative filter paper which has been exposed to hydrogen fluoride to form fluorescent oxinate by spotting with oxine. 3. A test for a cyanide can be based on the liberation of oxine from coppcr(II)oxinate and the detection of the oxine by the formation of fluorescent aluminium oxinate. 4. Some non-fluorescent oxinates are able to quench the fluorescence of aluminium oxinate dissolved in chloroform. 5. The oxinates of aluminium, gallium, and iron(III) have a remarkable resistance to the action of 3N hydrochloric acid, whereas all other oxinates dissolve immediately. An explanation for this behaviour is proposed.

Spectrophotometric determination of the formation constants of iron(III)-8-hydroxyquinoline complexes in 0.1 M sodium perchlorate solution at 25° gave the values K1=[FeOx2+]/([Fe3+][Ox-])=4.9·1013, K2=[FeOx2+]/([FeOx2+][Ox-])=4.2·1012 and K3=[FeOx3]/([FeOx2+][Ox-])=3.9·1010. FeOx2OH and FeOx(OH)2 are obtainable as solid phases. FeOx3 (Ksp=3·10-44, intrinsic solubility 1.6·10-7 M) dissolves in basic solutions to form FeOx2(OH)2 -In a solution saturated with FeOx3, ([FeOx2(OH)2-][Ox-])/[OH-]2=7.7·10-5.

DTA curves were obtained for a number of anhydrous metal chelates derived from the important analytical reagent 8-hydroxyquinoline. The compounds were heated in an inert atmosphere to avoid interaction with oxygen or water vapor. The Cu, Pb, Zn, Ni and Co chelates melted without decomposition, under the conditions used, while the remainder of the compounds underwent partial decomposition upon melting. The order of increasing melting point is Pb Mg > Sr > Cd > Mn > Ba > Co > Ni > Zn > Pb > Cu.

The deeply coloured 1:1 and 1:2 (metal : ligand) complexes of ruthenium(III) with 5,7-dichloro-8-hydroxyquinoline N-oxide (II), 5,7-dibromo-8-hydroxyquinoline N-oxide (III) and 5,7-dinitro-8-hydroxyquinoline N-oxide (IV) have been investigated spectrophotometrically in 60% acetone medium, and are suggested for the spectrophotometric determination of ruthenium(III) in presence of other platinum metals. The stability constants (log β1 and log β2 (determined spectrophotometrically) decrease in the order III < II < IV, which is the same as that of the basicity of the ligands.

The preparation of an 8-hydroxyquinoline complex of trivalent gold by the action of oxine upon gold chloride and “monopyridine gold chloride” is described. The absorption spectrum of the complex, which approximated to the composition AuCl 2 C 9 H 6 ON was plotted in the U.V. and visible regions of the spectrum. A partial separation between tri- and tetravalent titanium was obtained using paper chromatography. Absorption curves were obtained for oxine complexes of Ti(III) and Ti(IV) in the visible region of the spectrum.

8-Quinolinol-5-sulfonic acid can be used in compleximetric titrations by means of a displacement type of titration; a fluorescent weak complex is used to titrate an ion which forms a non-fluorescing stronger complex, the end-point being the appearance of fluorescence. The titration is best performed by an instrumental method. A non-fluorescing weak complex can similarily be used for the titration of a cation which is strongly complexed and fluoresces. By making use of suitable combinations, it is possible to titrate a non-fluorescing complex former and a fluorescing complex former in the same solution.

Experimental evidence suggests that the existence of only one stable cationic valency-state, in which the remaining electron shells arc empty, half-full or complete are necessary conditions for the fluorescence of a metal-8-hydroxyquinoline complex in u.v. light, The preparations of hitherto unreported compounds of 8-hydroxyquinoline with Rb, Cs, Ge, Sn and Ta are described.

2-Methyl-5-nitroso-8-hydroxyquinoline (2-methyl-5-nitroso-oxine), hitherto undescribed, has been prepared. The sensitivity and selectivity of this oxine derivative, together with 5-nitroso oxine, and 2-methyl-oxine towards aluminium, yttrium, gallium, indium and thallium(III) have been investigated. A gradation in selectivity is found. With oxine, precipitation occurs with all the above metals under the conditions of the test. With 2-methyl-oxine, precipitation occurs with all metals with the exception of aluminium. With 5-nitroso-oxine, no precipitation occurs with aluminium, yttrium, gallium and indium, and with 2-methyl-5-mtroso-oxine, no precipitation occurs with any metal in Group III B. A possible explanation for this behaviour is advanced.

A rapid method for fluoride determination in natural and waste water with a fluoride ion-specific electrode is described. This method involves a preliminary extraction of the interfering polyvalent cations, as their 8-hydroxyquinoline complexes, into a butyl cellosolve-chloroform mixture. The procedure is directly usable for water samples containing fluoride in the 0.2–6.0 p.p.m. range, with an overall error of less than 0.5%. The method can be successfully employed for fluoride determination in most polluted water samples which contain a high level of Ca, Mg, Fe and Al ions.