Spectrophotometric and direct-reading methods for the analysis of gas phase peroxyacetic acid

A new method for the determination of peroxyacetic acid (PAA) in gas phase samples is described. It is based on the oxidation of ABTS (2,2′-azino-bis(3-ethylbenzothiazoline)-6-sulfonate) by PAA with formation of a radical cation which is characterized by four strong absorption maxima between 405 nm and 810 nm. These allow for sensitive spectrophotometric determination of the peracid. The selectivity of the method towards hydrogen peroxide is strongly dependent on the sampling method used. Impinger sampling and sampling based on the use of coated solid sorbents (test tubes) was performed. Limits of detection are 10^–8 mol, limits of quantification are ¶5 × 10^–8 mol, the linear range consists of 1.5 concentration decades in both cases. Using ABTS-coated test tubes above 1 × 10^–7 mol, direct reading of the results is possible and may be used as rapid screening method for the PAA concentration.     

Determination of gas phase peroxyacetic acid using pre-column derivatization with organic sulfide reagents and liquid chromatography.

The first selective HPLC methods for the determination of peroxyacetic acid (PAA) in gas phase samples have been developed. PAA reacts with 2-([3-{2-[4-amino-2-(methylsulfanyl)phenyl]- 1-diazenyl}phenyl]sulfonyl)-1-ethanol (ADS) to form the corresponding sulfoxide. Sampling may be performed in impingers using aqueous solutions of the reagent or by test tubes with the reagent coated on a solid sorbent. Sulfide and sulfoxide are separated by means of HPLC and detected at a wavelength of 410 nm. The method is highly selective for PAA in the presence of hydrogen peroxide when sampling in impingers. A 10,000-fold excess of hydrogen peroxide leads to the same peak area compared to PAA. Limit of detection is 10(-8) mol PAA, thus corresponding to PAA concentration of 46 ppb when using a sampling time of 10 min with a flow-rate at 500 ml/min. Another sulfide reagent, methyl-p-tolyl sulfide (MTS) has been used in a similar way with impinger sampling. Major advantages of ADS towards MTS are improved UV-Vis spectroscopic properties and reduced volatility.     

Stopped-flow spectrophotometric determination of hydrogen peroxide with hemoglobin as catalyst

A rapid and sensitive method was proposed for the determination of hydrogen peroxide based on the catalytic effect of hemoglobin using o-phenylenediamine as the substrate. Stopped-flow spectrophotometric method was used to study the kinetic behavior of the oxidation reaction. The catalytic effectiveness of hemoglobin was compared with other four kinds of catalysts. The initial rate of the formation of the reaction product 2,3-diaminophenazine at the wavelength of 425 nm was monitored, permitting a detection limit of 9.2x10(-9) mol/l H(2)O(2). A linear calibration graph was obtained over the H(2)O(2) concentration range 5.0x10(-8)-3.5x10(-6) mol/l, and the relative standard deviation at a H(2)O(2) concentration of 5.0x10(-7) mol/l was 2.08%. Satisfied results were obtained in the determination of H(2)O(2) in real samples by this method.     

Flotation-spectrophotometric determination of trace of germanium with isochromatic dye ion-pairs formed by rhodamine 6G and tetrabromofluorescein

A flotation spectrophotometric method for the determination of germanium with isochromatic dye ion-pairs is described. The molar ratio of germanium to rhodamine 6G to tetrabromofluorescein is 1:5:5. The apparent molar absorptivity is 5.8 x 10(5) l mol(-1) cm(-1) at 531 nm. Beer's law is obeyed over the concentration range of 5.0 x 10(-8)-1.25 x 10(-6) mol l(-1). The proposed method is sensitive and accuracy and can be applied satisfactorily to the determination of germanium in vegetables.     

Spectrophotometric determination of fluoxetine by batch and flow injection methods

A rapid, simple, and accurate spectrophotometric method is presented for the determination of fluoxetine by batch and flow injection analysis methods. The method is based on fluoxetine competitive complexation reaction with phenolphthalein-beta-cyclodextrin (PHP-beta-CD) inclusion complex. The increase in the absorbance of the solution at 554 nm by the addition of fluoxetine was measured. The formation constant for fluoxetin-beta-CD was calculated by non-linear least squares fitting. Fluoxetine can be determined in the range 7.0 x 10(-6)-2.4 x 10(-4) mol l(-1) and 5.0 x 10(-5)-1.0 x 10(-2) mol l(-1) by batch and flow methods, respectively. The limit of detection and limit of quantification were respectively 4.13 x 10(-6) mol l(-1) and 1.38 x 10(-5) mol l(-1) for batch and 2.46 x 10(-5) mol l(-1) and 8.22 x 10(-5) mol l(-1) for flow method. The sampling rate in flow injection analysis method was 80+/-5 samples h(-1). The method was applied to the determination of fluoxetine in pharmaceutical formulations and after addition to human urine samples.     

Determination of a cationic surfactant with naphthalene black 12B by the resonance light scattering technique

A new determination method for a cationic surfactant, zephiramine (Zeph), was developed with resonance light scattering (RLS) technique, based on the interaction of naphthalene black 12B with Zeph. The resonance light scattering (RLS) and UV characteristics of interaction between naphthalene black 12B and Zeph were studied. The RLS intensity of naphthalene black 12B at 363 nm was greatly enhanced in the presence of Zeph at pH 6.0. The enhanced RLS is proportional to the concentration of Zeph in the range of 3.20 x 10(-7) - 1.44 x 10(-5) mol L(-1). The limit of detection was 8.8 x 10(-8) mol L(-1). The proposed method was applied to the determination of Zeph in synthetic and spiked water samples with the recovery of 96.2-104% and RSD of 1.1-2.5%.     

Fluorimetric study of the interaction between human serum albumin and quinolones-terbium complex and its application

A highly sensitive spectrofluorimetric method is proposed for determination of human serum albumin (HSA) and some quinolone drugs. Using quinolones-terbium (Tb3+) complex as a fluorescent probe, in the buffer solution of pH 7.8, HSA can remarkably enhance the fluorescence intensity of the quinolones-Tb3+ complex at 545 nm and the enhanced fluorescence intensity of Tb3+ ion is in proportion to the concentration of HSA and quinolone drugs. Optimum conditions for the determination of HSA were also investigated. The linear ranges and limits of detection are 8.0 x 10(-9) to 8.0 x 10(-8) mol L(-1), 4.20 x 10(-9) mol L(-1) (for HSA); 1.0 x 10(-6) to 4.0 x 10(-6) mol L(-1), 1.87 x 10(-8) mol L(-1) (for norfloxacin) and 1.0 x 10(-7) to 1.0 x 10(-6) mol L(-1), 4.82 x 10(-8) mol L(-1) (for enoxacine), respectively. This method is simple, practical and relatively free interference from coexisting substances, as well as much more sensitive than most of the existing assays.     

Lysozyme-enhanced europium(III)-metacycline luminescence and its application to the determination of metacycline.

A new spectrofluorometric method is described for the determination of metacycline (MC), based on modified enzyme-amplified lanthanide luminescence. Under the optimum conditions, Eu3+-MC forms a ternary complex with lysozyme in close proximity. Then lysozyme can remarkably enhance the characteristic fluorescence intensity of Eu3+ at 612 nm in metacycline-Eu3+ binary complex. The enhanced fluorescence intensity is in proportion to the concentration of MC. The limit of detection is 1.6 x 10(-8) mol L(-1), with a linear range from 6.2 x 10(-6) to 1.7 x 10(-5) mol L(-1). Interferences of other coexisting substances were studied. The developed method was successfully applied to the determination of MC in serum and urine samples. The mechanism of fluorescence enhancement was also studied.     

Determination of morphine in process streams by sequential injection analysis with chemiluminescence detection

A procedure for the determination of morphine in process streams by sequential injection analysis based on the chemiluminescence reaction of morphine with acidic potassium permanganate in the presence of sodium hexametaphosphate is presented. The chemiluminescence emission has been monitored using an in-house detection system which consisted of a fibre optic flowthrough cell and a sensitive, low dark current, photomultiplier tube. The calibration graph (range 2 x 10(-8) to 1 x 10(-4) mol/l) was not linear over the entire range of concentration, with a polynomial equation of best fit of y = 1.0 x 10(15) x(3) - 2.2 x 10(11) x(2) + 1.3 x 10(7) x - 8.3. The calibration function approximates linearity over the concentration range 2.5 x 10(-6) to 3.0 x 10(-5) mol/l where the slope of the log-log plot is 1.09 +/- 0.16. The detection limit was estimated at about 10(-8) mol/l from the response of the lowest calibration standard (2.5 x 10(-8) mol/l) which gave a signal to noise ratio of 3 : 1. Although the structurally related codeine did not interfere significantly the results suggest that this method may be susceptible to matrix effects, dependent on the location of sampling from the process stream.     

Flow-injection determination of trace amounts of dopamine by chemiluminescence detection

A flow-injection analysis (FIA) for the determination of dopamine has been developed. The method is based on the inhibition effect of dopamine on the iron(II)-induced chemiluminescence (CL) of 10,10'-dimethyl-9,9'-biacridinium dinitrate (lucigenin). The presence of a non-ionic surfactant, polyoxyethylene (23) lauryl ether (Brij 35), caused an increase in the inhibition effect. The present method allows the determination of dopamine over the range 1x10(-8)-2x10(-7) mol dm(-3). The relative standard deviation was 0.7% for eight determinations of 6x10(-8) mol dm(-3) dopamine. The detection limit (S/N=3) was 2x10(-9) mol dm(-3) with the sampling rate of 40 samples h(-1). The effect of other catecholamines and compounds of similar structure on the lucigenin CL reaction was studied: quinone, hydroquinone, norepinephrine, pyrocatechol and l-dopa suppressed the CL intensity.     

Spectrophotometric determination of some aromatic amines

A method for spectrophotometric determination of four aromatic amines is described. The method is based on the reaction between the amine and the colorless Fe(III)-ferrozine complex. The amine reduces iron from Fe(III) to Fe(II) which forms a violet colored complex with ferrozine. The method is suitable for to the determination of 1,4-phenylenediamine, 2,4-diaminotoluene, 8-aminoquinoline and 2-amino-3-hydroxypyridine. The effect of different factors such as; pH, stability of the complex, temperature, ferrozine concentration, Fe(III) concentration and methanol concentration have been studied. The composition of the complex as well as the tolerance amount of other amines have been reported. Maximum absorbance is at 562 nm and Beer's law is obeyed over the ranges 0.17-1.6 ppm for 1,4-phenylenediamine, 0.45-3.7 ppm for 2,4-diaminotoluene, 0.51-3.4 ppm for 8-aminoquinoline and 0.53-4.4 ppm for 2-amino-3-hydroxypyridine. The obtained molar absorbtivities were 4.7x10(4), 2.0x10(4), 1.6x10(4), 1.5x10(3) l mol(-1) cm(-1) respectively.     

Voltammetric determination of traces of Cr(VI) in the flow system in the presence of bipyridyne

The voltammetric method of Cr(VI) determinations in the flow system, based on the combination of selective accumulation of the product of Cr(VI) reduction on HMDE and a very sensitive method of chromium determination in the presence of bipyridine [Z. Gao K.S. Siow, Electroanalysis 8 (1996) 602] is proposed. The calibration graphs were linear from 3x10(-9) to 3x10(-8) and from 5x10(-10) to 5x10(-9) mol l(-1) for accumulation times 120 and 600 s, respectively. The relative standard deviation (R.S.D.) was 6.5% (n=5) for Cr(VI) concentration 1x10(-8) mol l(-1) and the accumulation time 120 s. The influence of foreign ions commonly present in water samples is presented. Validation of the method was made by comparison of the results of analyses of tap water by another electrochemical method and by recovery test for river and mineral water.     

Fluorimetric determination of ascorbic acid in vitamin C tablets using methylene blue

In this study, a simple and sensitive fluorimetric method was described for the determination of Ascorbic Acid (AA). The procedure is based on the reaction between AA and Methylene Blue (MB). The fluorescence intensity of MB was measured at excitation and emission of 664 and 682 nm, respectively. MB concentration was decreased as a function of decreasing fluorescence intensity due to forming colorless form of MB (Leuco-MB) in the reaction between AA and MB. A linear relationship was obtained between the decreasing fluorescence intensity and the concentration of AA in the range of 3.0 x 10(-7)-6.0 x 10(-6) mol.l(-1). The detection limit was 2.5 x 10(-7) mol.l(-1). The proposed method was applied successfully for the determination of AA in Vitamin C tablets.     

Chemiluminescence flow injection analysis of 1,3-dichloro-5,5-dimethylhydantoin in swimming pool water

A new chemiluminescence (CL) flow-injection method is proposed for the determination of 1,3-dichloro-5,5-dimethylhydantoin (DDH). The method is based on the chemiluminescent reaction of DDH and luminol-H(2)O(2) in an alkaline medium (pH 12.0-12.5). The concentration of the analyte shows a good linear relationship with the produced luminescence intensity in the range of 3.0x10(-8) to 8.0x10(-6) mol l(-1). The detection limit of the proposed method is 1.0x10(-8) mol l(-1) and the relative standard deviation (R.S.D.) is 4.7% (n=5) at 5.0x10(-7) mol l(-1). This method was successfully applied to the determination of trace amounts of this disinfectant in water samples obtained from five different swimming pools. Satisfying recovery values were also obtained.     

Spectrophotometric determination of some drugs for osteoporosis

Three simple, accurate and sensitive spectrophotometric methods are developed for the determination of some new drugs for the treatment of osteoporosis: risedronate sodium (I), alendronate sodium (II) and etidronate disodium (III). The first method is based on the measurement of difference in absorbance (Delta A) of risedronate sodium in 0.01 mol l(-1) hydrochloric and 0.1 mol l(-1) sodium hydroxide at 262 nm. Beer's law is obeyed over a concentration range of 15-150 microg ml(-1) with mean recovery 99.75+/-1.22 and molar absorptivity (epsilon) 1.891 x 10(3). The second method is based on the reaction of the primary amino group of (II) with ninhydrin reagent in methanolic medium in the presence of 0.05 mol l(-1) sodium bicarbonate. The colored product is measured at 568 nm, and the linearity range is found to be 3.75-45 microg ml(-1) with mean recovery 99.77+/-0.73 and epsilon 9.425 x 10(3). The third method is based on oxidation of the three mentioned drugs with ceric (IV) sulphate in 0.5 mol l(-1) sulphuric acid at room temperature and subsequent measurement of the excess unreacted cerium (IV) sulphate at 320 nm. The method obeyed Beer's law over a concentration range of 2-24 microg ml(-1) for the three drugs with mean recovery 99.79+/-1.16, 99.73+/-1.38 and 99.86+/-1.13 and epsilon 14.427 x 10(3), 13.813 x 10(3) and 14.000 x 10(3) for drugs I, II, III respectively. The proposed methods were successfully applied for the determination of the studied drugs in bulk powder and in pharmaceutical formulations. The results were found to agree statistically with those obtained the reported methods. Furthermore, the methods were validated according to USP regulations and also assessed by applying the standard addition technique.     

Fluorimetric determination of methylmercury as an ion-association complex with rhodamine B in the presence of iodide

A fluorimetric method for the determination of methylmercury was established. The method was based on the formation of an ionic pair between iodide-methylmercury-rhodamine B in hydrochloric acid, which can be extracted with benzene. The fluorescence emission was measured at lambda(ex)/lambda(em) 575/590 nm, and the experimental variables and possible interference were studied. The linear calibration range was 4 x 10(-8) mol/L to approximately 5 x 10(-7) mol/L with a correlation coefficient of 0.9992. The detection limit was 1 x 10(-8) mol/L. The method was used to determine methylmercury in human hair. The recovery was in the range of 91% to 105% and the relative standard deviation was 2.8%. The results agreed with those obtained by gas chromatography with electron capture detection.     

Resonance scattering spectral analysis of chlorides based on the formation of (AgCl)n(Ag)s nanoparticle

A novel resonance scattering spectral method has been proposed for the determination of trace amounts of chlorides in the range of 2 x 10(-7)-8 x 10(-6) mol/l. It was based on the photochemical reaction system of AgNO3-NaCl-sodium oxalic to form the (AgCl)nucleus (n)(Ag)shell (s) nanoparticle. There is a strongest resonance scattering peak at 470 nm and a maximum absorption peak at 425 nm. The concentration of chlorides is proportional to the intensity of resonance scattering at 470 nm. The nonlinear resonance scattering peaks of the nanoparticle system have been also considered, according to the theory of the interaction between the surface electron of nanoparticle and the incidence photon.     

Determination of ulifloxacin by terbium-sensitized fluorescence with second-order scattering and its applications.

This paper reports the determination of ulifloxacin (UFX) by terbium-sensitized fluorescence using a second-order scattering method. UFX and Tb(III) ion form a fluorescence complex in aqueous solution, and its maximum excitation and emission wavelengths are located at 273 and 545 nm, respectively. In optimum conditions, the relative intensity at 545 nm has a linear relationship to the concentration of UFX in the range of 2.0 x 10(-8) - 1.0 x 10(-5) mol L(-1) and the detection limit is 3.9 x 10(-9) mol L(-1). The proposed method was applied to the determination of UFX in spiked human serum and urine satisfactorily. The luminescence property of UFX is also discussed by comparing with norfloxacin (NFLX) and ofloxacin (OFLX).     

Flow-injection electrogenerated chemiluminescence determination of isoniazid using luminol.

Based on a new electrogenerated chemiluminescence (ECL) analytical idea, this paper explains a sensitive and selective flow-injection ECL method using luminol for the determination of isoniazid, based on the sensitizing effect of isoniazid for the weak ECL emission of electrochemically oxidized luminol. Under the optimum experimental conditions, the relative ECL intensity was linear with isoniazid concentration in the range of 4.0 x 10(-8) mol/L to 8.0 x 10(-6) mol/L and with a detecting limit of 2.8 x 10(-8) mol/L.     

高效液相色谱-荧光检测法测定环境样品中的过氧化物

对高效液相色谱-荧光检测法测定过氧化氢和有机过氧化物的方法进行了改进,从而提高了方法的检测灵敏度。以氯化血红素(hemin)作催化剂进行柱后衍生反应,过氧化物将对羟基苯乙酸氧化生成能吸收荧光的二聚物,然后用荧光检测器检测。实验确定了最佳反应管温度和荧光检测波长。应用该法测定了大气和雨水样品中过氧化物的浓度。