Effect of acidity and alkalinity on the distillation of phenol: interferences of aromatic amines and formaldehyde with the 4-aminoantipyrine spectro-photometric method for phenol

As determined by the 4-aminoantipyrine (4-AAP) spectrophotometric method, the distillation of phenol is quantitative over the range from about pH 6 to very strongly acidic solutions. Recovery from alkaline solutions decreases with increasing alkalinity. Aromatic amines can interfere with the 4-AAP method by producing colors. The extent of the interference varies markedly with different aromatic amines and is much greater for the extraction method than the direct method. The interference can be considerably reduced by distillation from a strongly acidic solution (10 ml of concentrated sulfuric acid per 500 ml); for large amounts of aromatic amines, double distillation may be necessary. Formaldehyde can interfere by reacting with phenol and repressing the color development. This interference can be eliminated by treatment with ammonium sulfate and sodium hydroxide to form hexamethylenetetramine, followed by acidification and distillation.     

Study of the behaviour of various phenolic compounds in the 4-aminoantipyrine and ultraviolet-ratio spectrophotometric methods without and with distillation

It is customary in industrial analysis in the determination of phenols by the 4-aminoantipyrine (4-AAP) and ultraviolet-ratio spectrophotometric methods to report the total of phenolic compounds as phenol. A study was therefore made of the behaviour of 36 representative phenolic compounds in the 4-AAP and UV-ratio methods, with and without distillation, to ascertain the apparent recoveries relative to that for phenol. The Fisher phenol analyser was used for the UV-ratio method, which depends upon the bathochromic shift (from about 270 to about 290 nm) usually obtained when the solution of the phenol is made alkaline. The apparent recoveries by the 4-AAP method both with and without distillation varied from 0 to 100%. The apparent recoveries by the UV-ratio method without distillation varied from 0 to 148%, and those with distillation varied from 0 to 110%. Sixteen of the compounds tested without distillation gave less than 10% recovery by the 4-AAP method and eleven gave less than 10% recovery by the UV-ratio method. The results after distillation indicated that several of the compounds did not distil completely.     

Stabilization of sulfide and sulfite and ion-pair chromatography of mixtures of sulfide, sulfite, sulfate and thiosulfate

Ion chromatography of sulfide, sulfite, sulfate and thiosulfate in a mixture is often difficult because of instability of sulfide and sulfite, poor separation of sulfide from common anions such as bromide or nitrate and similar elution-times for sulfite and sulfate. An ion-pair chromatographic method for the determination of these sulfur anions has been established by stoichiometric conversion of sulfide and sulfite into stable thiocyanate and sulfate, respectively, prior to the chromatographic run. Sulfate, thiosulfate and thiocyanate were resolved on an octadecylsilica column with an acetonitrile-water mobile phase containing tetrapropylammonium salt (TPA) as an ion-paring reagent, and thiosulfate and thiocyanate in the effluent could be measured with a photometric detector (220 nm) and sulfate with a suppressed conductivity detector. When an acetonitrile-water (6:94, v/v) mobile phase (pH 5.0) containing 15 mM TPA and small amounts of acetic acid was used at a flow-rate of 0.6 ml min(-1), the three anions could be eluted within 32 min. Calibration plots of peak height versus concentration for sulfide (detected as thiocyanate) and thiosulfate gave straight lines up to 35 and 60 microM, respectively. The calibration plot for sulfide coincided with that obtained by using thiocyanate. A calibration plot for sulfite, measured as sulfate, was also linear up to 135 microM and was in accord with that of sulfate. Each calibration plot gave a correlation coefficient greater than 0.999. For six replicates obtained for a mixture of 30.0 microM sulfide, 50.0 microM sulfite, 50.0 microM sulfate and 20.0 microM thiosulfate, the proposed method gave a mean value of 30.1 microM with a standard deviation (SD) of 0.77 microM and a relative standard deviation (RSD) of 2.6% for sulfide, 101 microM (SD = 3.5 microM, RSD = 3.5%) for the total of sulfite and sulfate and 20.1 microM (SD = 0.44 microM, RSD = 2.2%) for thiosulfate. Recoveries for sulfide, sulfite plus sulfate, and thiosulfate in hot-spring water samples using the proposed method were found to be quantitative.     

Spectrophotometric determination of total phenolics by solvent extraction and sorbent extraction optosensing using flow injection methodology

Flow injection analysis (FIA) procedures for the Spectrophotometric determination of phenol involving in-line concentration by solvent and sorbent extraction have been developed. The imine product formed in the reaction between phenol and 4-aminoantipyrine (4-AAP) is either extracted into chloroform (solvent extraction) or is temporarily retained on C₁₈-modified silica material contained in a microcolumn (sorbent extraction). In the latter case two variants of detection have been used namely the Spectrophotometric measurement of the methanolic eluent containing the concentrated dye and at-column optosensing of the retained reaction product followed by methanol elution to maintain reversibility of the process. In the solvent extraction procedure a 10-fold increase of sensitivity compared to the common FIA method without extraction is achieved but no corresponding improvement in detectability is observed. Under optimized conditions the detection limit amounts to 8 μg l⁻¹. Using sorbent extraction methodology, high concentration factors can be obtained when large sample volumes are used. The only limitation in getting correspondingly lower detection limits are an increasingly high and variable blank value with sampling volume. The detection limits obtained for measurement of the absorbance in the eluent and on-column optosensing are 11 μg l⁻¹ and 0.4 μg l⁻¹, respectively. A study of the extractability of various phenol derivates using both solvent and sorbent extraction revealed lower relative response rates compared to the FIA method without extraction. Phenolics that possess an additional acidic group are present in ionized form at the high pH of the assay and are not extractable at all.     

A New Extraction Spectrophotometric Method for the Determination of Phenol in Water

The product of the reaction among phenol, sodium nitroprusside and hydroxylamine hydrochloride in an alkaline solution can be extracted by chloroform in the presence of cetylpyridinium bromide(CPB), on the basis of which a new extraction spectrophotometric method for the determination of phenol in water is developed. The optimum determination wavelength is 720 nm. The molar absorptivity is 1.05×105 mol-1·L·cm-1 and the detection limit is 4.0 μg/L. For 30.0 and 60.0 μg/L standard solutions, the relative standard deviations are 4.5% and 2.2%, respectively(n=6). F values of the statistical analysis show that there is no notable difference between the proposed method and 4-AAP method. The results of the standard addition method for the natural water samples are satisfactory.     

Determination of total phenols in environmental wastewater by flow-injection analysis with a biamperometric detector

A flow injection (FI) method with a biamperometric detector, based on the biamperometry for an irreversible redox couple, is described for the determination of phenols in environmental wastewater. The method relies on coupling of the oxidation of phenols at one platinum-wire electrode with the reduction of MnO4- at another platinum wire electrode to enable biamperometric detection with an applied potential difference of 0 V. The linear dynamic range for the dependence of current on phenol concentration was from 1.0 x 10(-6) to 1.0 x 10(-4) mol L(-1), with a detection limit of 4.0 x 10(-7) mol L(-1) (signal-to-noise ratio, S/N=3). In comparison with the 4-aminoantipyrine (4-AAP) standard method and the 3-methyl-2-benzothiazoline hydrazone (MBTH) method the proposed method can be used to detect many para-substituted phenols that do not react with 4-AAP and MBTH, and response factors are higher for most of the phenols tested. The method, which is simple, economic, and rapid (180 samples h(-1)), has been applied to the analysis of four wastewater samples. The results obtained were compared with those from 4-AAP method. The recoveries obtained by adding phenol standards to samples ranged from 94.3 to 105.2% with a standard deviation of 3.6%.     

过硫酸钾氧化4-氨基安替比林分光光度法测定地表水中挥发酚

在pH值为10.0±0.2的缓冲溶液中,以过硫酸钾溶液作氧化剂,用经乙醇和正己烷(1+4)混合溶液提纯的4-氨基安替比林(4-AAP)作显色剂,采用三氯甲烷分光光度法测定地表水中挥发酚.结果表明,经乙醇和正己烷(1+4)混合溶液提纯的4-AAP,损失较少,且纯度较高,有利于准确配制4-AAP溶液.此外,稳定、无色的过硫...     

Determination of ultra-micro amounts of sulfur in igneous rocks by spectrofluorimetry using 2-(o-hydroxyphenyl) benzoxazole derivatization and tin(II)-strong phosphoric acid-assisted reduction

A new and very sensitive method was developed for the determination of ultra-micro amounts of sulfur in igneous rock samples. The sulfur compounds in an igneous rock sample are reduced and released in the form of hydrogen sulfide by heating with a tin(II)-strong phosphoric acid (SPA) reagent. The liberated hydrogen sulfide is carried by a flow of nitrogen into a copper(II) absorbing solution to obtain a precipitate of copper(II) sulfide. The remaining copper(II) ion forms a chelate with 2-(o-hydroxyphenyl)benzoxazole (HPB) and quenches the fluorescence of HPB. The amount of sulfide is determined by measuring the HPB fluorescence intensity. The optimum reaction conditions were stoichiometrically investigated. By the present method using 0.1-0.2 g of rock sample, ultramicro amounts of sulfur (0.1-12.8 mug) could be quantitatively separated, collected, and determined with a relative standard deviation of 1.37% for a sample containing 5.7 mug of sulfur (95% confidence level).     

Ion paired chromatography of iron (II,III), nickel (II) and copper (II) as their 4,7-Diphenyl-1,10-phenanthroline chelates

A reversed phase ion-paired chromatographic method that can be used to determine trace amounts of iron (II,III), nickel (II) and copper (II) was developed and applied to the determination of iron (II) and iron (III) levels in natural water. The separation of these metal ions as their 4,7-diphenyl-1,10-phenanthroline (bathophenanthroline) chelates on an Inertsil ODS column was investigated by using acetonitrile-water (80/20, v/v) containing 0.06 M perchloric acid as mobile phase and diode array spectrophotometric detection at 250-650 nm. Chromatographic parameters such as composition of mobile phase and concentration of perchloric acid in mobile phase were optimized. The calibration graphs of iron (II), nickel (II) and copper (II) ions were linear (r > 0.991) in the concentration range 0-0.5, 0-2.0 and 0-4.0 mug ml(-1), respectively. The detection limit of iron (II), nickel (II) and copper (II) were 2.67, 5.42 and 18.2 ng ml(-1) with relative standard deviation (n = 5) of 3.11, 5.81 and 7.16% at a concentration level of 10 ng ml(-1) for iron (II) and nickel (II) and 25 ng ml(-1) for copper (II), respectively. The proposed method was applied to the determination of iron(II) and iron(III) in tap water and sea water samples without any interference from other common metal ions.     

Determination of total sulfite in wine. Zone electrophoresis-isotachophoresis quantitation of sulfate on a chip after an in-sample oxidation of total sulfite

This work deals with the determination of total sulfite in wine. The determination combines an in-sample hydrogen peroxide oxidation of total sulfite in alkalized wine to sulfate with the separation and quantitation of the latter anion by zone electrophoresis (ZE) on-line coupled with isotachophoresis (ITP) on a column-coupling chip. Sample clean up, integrated into the ITP-ZE separation, eliminated wine matrix in an extent comparable to that provided by a highly selective distillation isolation of sulfite. At the same time, conductivity detection, employed to the detection of sulfate in the ZE stage of the ITP-ZE combination, provided for sulfate the concentration limit of detection corresponding to a 90 microg/l concentration of sulfite in the loaded sample (0.9 microl). Such a detectability allowed a reproducible quantitation of total sulfite when its concentration in wine was 15 mg/l. Formaldehyde binding of free sulfite in wine, included into the pre-column sample preparation, prevented an uncontrolled oxidation of this sulfite form. This step contributed to an unbiased determination of sulfate present in the original wine sample (this determination corrected for the concentration of sulfate determined in the sample after the peroxide oxidation of sulfite to the value equivalent to the total sulfite). The 99-101% recoveries of sulfite, determined for appropriately spiked wine samples, indicate a very good accuracy of the present method. Such a statement also supports excellent agreements of the results of quantitation based on the in-sample peroxide oxidation of the total sulfite (bound sulfite released at a high pH) with those in which this analyte was isolated from wine by distillation (bound sulfite released at a very low pH).     

Anwendung von Austauschreaktionen zur Vervielfachung von Sulfid und Sulfat

Zusammenfassung Über die Vervielfachung von Milligrammengen Sulfid (Austauschreaktion mit Silberjodid) und von Mikrogrammengen Sulfat (Austauschreaktion mit Bariumjodat in acetonitrilhaltigem Medium) wurde berichtet. Das freigesetzte Jodid bzw. Jodat wird nach üblichen Methoden jodometrisch bestimmt. Ein großer Überschuß an Sulfit und annähernd äquimolare Mengen an Thiosulfat stören die Sulfidbestimmung nicht.

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Employment of exchange reactions for the multiplication of sulfide and sulfate

Summary A report is given of the multiplication of milligram quantities of sulfide (exchange reaction with silver iodide) and of microgram amounts of sulfate (exchange reaction with barium iodate in a medium containing acetonitrile). The liberated iodide or iodate is determined iodometrically according to the usual procedures. A large excess of sulfite and approximately equimolar amounts of thiosulfate do not interfere with the sulfide determination.

     

Non-extractive derivative spectrophotometric determination of cobalt in neutral micellar medium

A sensitive derivative spectrophotometric method using 1-nitroso-2-naphthol has been developed for determination of trace amounts of cobalt in the presence of a neutral surfactant. Photometric parameters, viz., lambda(max), molar absorption coefficient and analytical sensitivity of the complex formed in micellar media are 420 nm, 3.18x10(4) l mol(-1) cm(-1) and 2.05 ng ml(-1), respectively. Beer's law holds from 0.20 to 3.0 mug ml(-1) of the analyte concentration. The method has a high sensitivity with a detection limit of 1.68 ng ml(-1). A selective determination of cobalt in presence of copper(II) or iron(III) using derivative spectral profiles and without any masking or pre-separation is also reported. Samples of drugs and standard alloys analysed by the proposed method yielded results comparable to those obtained using recommended procedures.     

Resolution of matrix effects on analysis of total and methyl mercury in aqueous samples from the Florida Everglades

 Aqueous samples from the Florida Everglades present several problems for the analysis of total mercury (HgT) and methyl mercury (MeHg). Constituents such as dissolved organic carbon (DOC) and sulfide at selected sites present particular challenges due to interferences with standard analytical techniques. This is manifested by 1) the inability to discern when bromine monochloride (BrCl) addition is sufficient for sample oxidation for HgT analysis; and 2) incomplete spike recoveries using the distillation/ethylation technique for MeHg analysis. Here, we suggest ultra-violet (UV) oxidation prior to addition of BrCl to ensure total oxidation of DOC prior to HgT analysis and copper sulfate (CuSO₄) addition to aid in distillation in the presence of sulfide for MeHg analysis. Despite high chloride (Cl^-) levels, we observed no effects on MeHg distillation/ethylation analyses. Received: 24 September 1996/Revised: 12 February 1997/Accepted: 19 February 1997     

Extraction of copper(II) carboxylates with chloroform under substoichiometric conditions

The features are considered of binding carboxylic acids (HR) as dimeric solvated copper(II) complexes at the copper(II) extraction with chloroform under substoichiometric conditions, with excess of the metal ion in the aqueous phase. The fundamental difference in the optimization of the quantitative extraction of copper(II) in the form of any carboxylate with a maximum ratio of Cu:R and the total binding with carboxylic acids to form the copper complex of the minimum stoichiometry was noted. It was found that quantitative binding of HR occurred at the extraction of mixed-ligand acetate-carboxylate copper(II) complexes without control over the aqueous phase acidity when acetic acid medium or copper(II) acetate was used, but not copper chloride, nitrate, perchlorate, or sulfate. The possibility of determination by extraction-photometric method by the color of the Cu(II) complex was shown that was suitable only to those carboxylic acids, whose logarithm of the partition coefficient in the water-chloroform mixture was higher than three.     

Indirect Determination of Sulfide by Extraction Flotation Spectrophotometry of Copper(II) with Ammonium Sulfate‐Ethanol‐Water System

A new extraction flotation spectrum method for indirect determination of trace amounts of sulfide by ammonium sulfate‐ethanol‐water system was developed. It showed that Cu(II) could combine with S^2? into precipitate (CuS) which was floated in the surface of ethanol and water in the presence of ammonium sulfate. The sulfide can be indirectly determined by determining the flotation yield of Cu(II). The linear range from 2.4 × 10^?8to 3.2 × 10^?6g/mL and the detect limit of 2.0 × 10^?8g/mL was achieved. The results showed the determination of S^2? was not affected by Pb(II), Zn(II), Cd(II), Fe(II), Co(II),Ni(II), Mn(II) and Cl^?, Br^?, I^?, etc. In the paper, the method was successfully applied to the determination of a trace amount of sulfide in polluted water samples with the advantages of simplicity of equipment, rapidity, low cost, etc.     

Quantitative separation of zinc traces from cadmium matrices by solid-phase extraction with polyurethane foam

A system for separation of zinc traces from large amounts of cadmium is proposed in this paper. It is based on the solid-phase extraction of the zinc in the form of thiocyanate complexes by the polyurethane foam. The following parameters were studied: effect of pH and of the thiocyanate concentration on the zinc extraction, shaking time required for quantitative extraction, amount of PU foam necessary for complete extraction, conditions for the separation of zinc from cadmium, influence of other cations and anions on the zinc sorption by PU foam, and required conditions for back extraction of zinc from the PU foam. The results show that zinc traces can be separated from large amounts of cadmium at pH 3.0±0.50, with the range of thiocyanate concentration from 0.15 to 0.20 mol l⁻¹, and the shaking time of 5 min. The back extraction of zinc can be done by shaking it with water for 10 min. Calcium, barium, strontium, magnesium, aluminum, nickel and iron(II) are efficiently separated. Iron(III), copper(II) and cobalt(II) are extracted simultaneously with zinc, but the iron reduction with ascorbic acid and the use of citrate to mask copper(II) and cobalt(II) increase the selectivity of the zinc extraction. The anions nitrate, chloride, sulfate, acetate, thiosulphate, tartarate, oxalate, fluoride, citrate, and carbonate do not affect the zinc extraction. Phosphate and EDTA must be absent. The method proposed was applied to determine zinc in cadmium salts using 4-(2-pyridylazo)-resorcinol (PAR) as a spectrophotometric reagent. The result achieved did not show significant difference in the accuracy and precision (95% confidence level) with those obtained by ICP–AES analysis.     

Amberlite XAD resin solid-phase extraction coupled on-line to a flow injection approach for the rapid enrichment and determination of phenols in water and waste waters

A novel and expeditious approach for direct determination of phenols in water and waste waters based on solid-phase extraction coupled on-line to a flow injection analysis (FIA) manifold is described. The method employs on-line preconcentration of the phenols in an acidified sample (pH=2.0) onto a 3 cmx3 mm column packed with Amberlite XAD-4 resin. The phenols are subsequently eluted from the resin into a flowing system with an alkaline solution (pH=13) by actuating a switching valve; the eluted analytes were then quantified spectrophotometrically as the products of reaction with 4-aminoantipyrine (4-AAP) and potassium ferricyanide on passing through the flow-cell of a detector. The proposed method has a linear calibration range 0.01-1 mug ml(-1) of phenol, with a detection limit of 0.004 mug ml(-1) (S/N=3) and a sample throughput of 12 h(-1), investigated with a 4.4 ml sample volume. The relative standard deviation is 2.4% for 0.2 mug ml(-1) of the analyte. The sensitivity offered by the procedure was higher by a factor of 13 than that provided by a conventional flow injection analysis method. The analytical scheme of the proposed system is much simpler than its conventional manual counterpart due to the fact that it combines trace enrichment, sample clean-up, derivation and detection in one analytical set-up. The high speed, ease of use and automation, selectivity, and relative freedom from random contamination by sample handling make this method ideal for the phenols monitoring in water and waste waters.     

Spectrophotometric determination of sulfide in the presence of sulfite and thiosulfate via the precipitation of bismuth(III) sulfide.

A photometric method has been developed for the determination of sulfide at 10(-5) mol dm(-3) levels, which is based on the reaction of sulfide with a given excess amount of bismuth(III) to form a precipitate of bismuth(III) sulfide and on the spectrophotometric measurement of the residual bismuth(III) at 335 nm after extracting with bismuthiol II reagent from an aqueous solution containing acetate buffer into benzene. The presence of sulfite and thiosulfate up to 0.002 mol dm(-3) did not cause any interference in the determination of sulfide, because both sulfite and thiosulfate do not produce any precipitate with bismuth(III). A linear calibration plot with a negative slope was obtained for sulfide over the range of 5.00 x 10(-7) - 3.00 x 10(-5) mol dm(-3) (16.0 - 960 ppb). An experimental calibration plot was in accord with the theoretical plot, taking into account the known excess of bismuth(III), showing that the reaction of sulfide with bismuth(III) proceeded to completion. The relative standard deviation of results from 10 replicate determinations of standard sulfide (2.00 x 10(-5) mol dm(-3)) was 0.44%. The proposed method was successfully applied to the determination of sulfide in hotspring water samples without any pretreatment.     

Cross-talk Between (Hydrogen)Sulfite and Metalloproteins: Impact on Human Health

Sulfite is a potent toxic substance causing harm to multi-organ in human. Despite toxicity, it is widely used as preservative, anti-browning and anti-oxidant in foods, beverages, and pharmaceuticals, which cause easy admission of sulfite in human. Sulfite is also produced endogenously during the catabolism of cysteine and methionine. In vivo, the serum sulfite level at physiological range is strictly maintained by a molybdenum dependent sulfite oxidase (SO), which catalyzes sulfite to sulfate oxidation via a two-electron oxidation pathway. The loss of SO activity causes high serum sulfite level that fosters several diseases, including asthma, neurological dysfunction, birth defects, and heart diseases. The cytotoxicity of (bi)sulfite is implicated as sulfite radicals, which are generated by mainly heme-peroxidases via a one-electron oxidation pathway. On the other hand, the toxic sulfite radicals are neutralized to sulfite by heme-globins. The enzymatic reduction of sulfite to sulfide is catalyzed by sulfite reductase, which contains an unusual metal cofactor, siroheme-[4Fe4S]-cluster. Overall, the interaction of sulfite with various metalloproteins in vivo is a close relation with human health. Therefore, this review describes the metabolic conversion of (bi)sulfite to sulfate, sulfite radical or sulfide via oxidation or reduction pathways by various metalloproteins (specially SOs, peroxidases, heme-globins, and sulfite reductases), and the potential applications of sulfite in biosensors/biofuel cells, anti-browning, and advance oxidation process.     

固相萃取光度法测定饮用水中挥发酚的研究

研究了用Waters Sep-Park-C18小柱固相萃取光度法测定饮用水中挥发酚的方法。水样中经水汽蒸馏分离后的挥发酚，用4－氨基安替比林显色，显色产物可用C18固相萃小柱萃取、乙醇洗脱后用分光光度法测定。方法污染小，操作简便，便于批量样品处理，用于饮用水中挥发酚的测定，结果令人满意。