Sensitive fluorimetric determination of formaldehyde by the co-quenching effect of formaldehyde and sulfite on the fluorescence of tetra-substituted amino aluminium phthalocyanine

A novel and sensitive fluorimetric method was developed for the determination of formaldehyde based on the co-quenching effect of formaldehyde and sulfite on the fluorescence of tetra-substituted amino aluminium phthalocyanine. Formaldehyde in the concentration range 0.040-1.19 micrograms ml-1 can be determined with a limit of detection of 7.5 ng ml-1. The relative standard deviation for nine replicate measurements of 80.0 ng ml-1 formaldehyde is 1.8%. The method was applied to the analysis of real samples with satisfactory results.     

The fluorimetric determination of phosphate with thiamine

A method for the microdetermination of sulphur in organic compounds by means of combustion in a flow of oxygen is described. The oxides of sulphur are absorbed and stored on a small silver layer. After completion of the combustion, the oxygen is replaced first by nitrogen and secondly by hydrogen which liberates the sulphur as sulphur dioxide and regenerates the silver layer. The sulphur dioxide can be easily absorbed by dilute hydrogen peroxide and determined by any convenient method.     

The specific fluorimetric determination of digoxin.

The simultaneous determination of Cd, Cu, Pb and Zn in lead and zinc concentrates by fundamental, second-harmonic and linear-sweep a.c. and pulse polarographic methods is described. Calibration curves are linear over wide concentration ranges, so that both major and minor trace constituents can be determined in the same experiment; thus the polarographic method is highly competitive with atomic absorption spectrometry (a.a.s.). Conventional a.c. polarography and a.a.s. were compared in the first instance with conservative instrumentation. More sophisticated polarographic methods were then utilized; with the phase-selective linear sweep a.c. (fundamental- and second-harmonic) methods the four elements were determined simultaneously from voltammograms obtained in less than 20 s down to the 10^-6-10^-7M concentration range.     

A sensitive flow analysis system for the fluorimetric determination of low levels of formaldehyde in alcoholic beverages

A sensitive FIA method was developed for the selective determination of formaldehyde in alcoholic beverages. This method is based on the reaction of Fluoral-P (4-amine-3-pentene-2-one) with formaldehyde, leading to the formation of 3,5-diacetyl-1,4-dihydrolutidine (DDL), which fluoresces at λ_ex = 410 nm and λ_em = 510 nm. The analytical parameters were optimized by the response surface method using the Box-Behnken design. The proposed flow injection system allowed for the determination of up to 3.33 × 10⁻⁵ mol L⁻¹ of formaldehyde with R.S.D. < 2.5% and a detection limit of 3.1 ng mL⁻¹. The method was successfully applied to determine formaldehyde in alcoholic beverages, without requiring any sample pretreatment, and the results agreed with the reference at a 95% confidence level by paired t-test. In the optimized condition, the FIA system proved able to analyze up to 60 samples/h.     

催化荧光光度法测定血红蛋白

基于血红蛋白(Hb)对过氧化氢氧化靛蓝胭脂红体系的催化作用,建立了模拟酶催化荧光光度法测定血红蛋白的新方法并对催化氧化反应的机理进行了初步探讨。实验发现体系的荧光强度与血红蛋白浓度在6.20×10-11~7.75×10-8mol/L范围内线性关系良好,方法的检出限为1.67×10-11mol/L。方法用于人血中血红蛋白含量的测定,回收率为98.8%~103.2%。     

Development and comparison of different fluorimetric HPLC-methods with standard methods for the determination of formaldehyde in the atmosphere

Summary Three different fluorimetric methods for the measurement of atmospheric formaldehyde are described. The relatively unknown 2-diphenylacetylindan-1,3-dionhydrazine (DAIH) method was developed and optimized with an improved limit of detection of 2 ppbv corresponding to a sample volume of 7.5 L. Separation of lutidines necessary for the Nash method was successfully carried out and the separation time was reduced by a factor of 5. The detection limit of the Nash method was improved to 1 ppbv. In comparison, the N,N-diphenyl-1-naphthylamine-5-sulfonhydrazine (DNSH) method performed in a similar manner, reached an LOD of 0.5 ppbv. Finally, measurements made in candle smoke using the three different fluorimetric methods and three standard methods yielded very similar results.     

A new fluorimetric method for the determination of formaldehyde in air based on the liquid droplet sampling technique

A new, simple, sensitive, selective and in-field fluorimetric method for the determination of formaldehyde is proposed. The reaction of formaldehyde with hydralazine in acidic medium, heating on a boiling water-bath for 25 min, produces s-triazolo[3,4-a]phthalazine (Tri-P). The fluorescence intensity of the product formed (Tri-P) was determined at lambda em = 389 nm with lambda ex = 236 nm. The fluorescence intensity is linear over a formaldehyde concentration range of 1.2-33.0 micrograms l-1. The proposed method was applied successfully to the determination of formaldehyde sampled from the atmosphere using the liquid droplet technique. Formaldehyde vapour in a wind tunnel was produced by a mean of permeater. A linear curve was obtained between the concentration in the wind tunnel and that in the droplet. The detection limit for formaldehyde was 2.0 micrograms l-1 with RSDs varying from 3 to 12% in ambient air, using a droplet correction solution (boric acid and hydralazine). The effect of interfering substances on the determination shows that most cations and anions did not interfere. The results obtained were satisfactory compared with a reference method.     

Long-wavelength stopped-flow fluorimetric determination of lysozyme

The use of Cresyl Violet and sodium dodecyl sulphate for the kinetic fluorimetric determination of lysozyme from dynamic fluorescence measurements at a long wavelength in the range near 600 nm was explored. The high initial rate of this system allows analytical measurements to be made within ca. 2 s after the reactants are mixed, by using the stopped-flow mixing technique, which makes the method applicable to automatic routine analysis. The calibration graph is linear over the range 0.5-40 mug ml(-1) lysozyme hydrochloride and the detection limit of 0.19 mug ml(-1). The precision is less than 2% (relative standard deviation). The results obtained by applying the proposed method to the analysis of pharmaceutical samples with no pretreatment shown how readily it can be adapted for routine analyses. Analytical recoveries ranged between 94.0 and 104.0%.     

Flow injection fluorimetric determination of thiourea

A flow injection configuration for the fluorimetric determination of thiourea is proposed. The procedure is based on the rapid oxidation of thiourea by thallium(III) with concomitant formation of fluorescent thallium(I). Linear calibration graphs were obtained between 5 x 10(-7) and 1 x 10(-5)M, with a sampling rate of 90 samples/hr. The usefulness of the method was tested in the determination of thiourea in fruit juices and fruit peels.     

Spectrophotometric and fluorimetric determinations of trichothecene mycotoxins with reagents for formaldehyde

Several trichothecene mycotoxins, such as fusarenone-X (F-X) and T-2 toxin (T-2), readily liberate formaldehyde on heating with sulfuric acid. Spectrophotometric and fluorimetric methods for the determination of trichothecenes with reagents for formaldehyde are therefore possible. F-X (or T-2) can be determined in the 50–1000 mg l^-1 (or 50–1500 mg l^-1) range by the chromotropic acid method, in the 30–1200 mg l^-1 (or 50–2000 mg l^-1) range by the phenyl J acid method, and in the 1.25–25 mg l^-1 (or 2–40 mg l^-1) range by the J acid method. Other trichothecenes, neosolaniol, nivalenol, tetraacetylnivalenol, diacetoxyscirpenol and HT-2 toxin, etc. also give positive reactions but trichothecin and dihydronivalenol do not.     

Fluorometric determination of formaldehyde

A simple, selective and sensitive fluorometric method is presented for the determination of formaldehyde in water based on its reaction with 3,4-diaminoanisole in alkaline ethanol-water solution to give a strongly fluorescing Schiff base. The dependence of the fluorescence intensity on the solvent composition, quenching by acetic and sulphuric acid, heating time and interference by other compounds is discussed. The detection limit of the method is 0.6 μg/L. The recovery of formaldehyde spiked into river water is 93% with an R.S.D of 6.05% at a concentration level of 10 μg/L. Received: 18 November 1996 / Revised: 17 February 1997 / Accepted: 18 February 1997     

Fluorometric determination of formaldehyde

A simple, selective and sensitive fluorometric method is presented for the determination of formaldehyde in water based on its reaction with 3,4-diaminoanisole in alkaline ethanol-water solution to give a strongly fluorescing Schiff base. The dependence of the fluorescence intensity on the solvent composition, quenching by acetic and sulphuric acid, heating time and interference by other compounds is discussed. The detection limit of the method is 0.6 μg/L. The recovery of formaldehyde spiked into river water is 93% with an R.S.D of 6.05% at a concentration level of 10 μg/L.     

Spectrophotometric determination of formaldehyde

A new spectrophotometric method for the determination of micro amounts of formaldehyde in aqueous and methanol solutions is based on the oxidation of formaldehyde by hydrous silver oxide at pH 11-12.5 and oxidation of the metallic silver produced, with iron(III) in the presence of Ferrozine. The absorbance of the resulting iron(II)-Ferrozine complex at 562 nm is proportional to the amount of formaldehyde and corresponds to an apparent molar absorptivity of 5.58 x 10(4) 1.mole(-1).cm(-1).     

Spectrophotometric determination of formaldehyde by using formaldehyde dehydrogenase

A new method for the determination of formaldehyde by using formaldehyde dehydrogenase is described. The method is based on the quantitative oxidation of formaldehyde with oxidized nicotinamide adenine dinucleotide (NAD⁺), in the presence of formaldehyde dehydrogenase, to form the reduced dinucleotide (NADH). This enzyme does not require glutathione as a co-factor and the NADH produced, which is directly proportional to the concentration of formaldehyde in the assay solution, is then measured spectrophotometrically at 340 nm. Formaldehyde can be determined in the range 0.3–8.0 μg ml^?1 (1.0×10^?5–2.7× 10^?4 M) with a sensitivity of 0.216 absorbance/ μg ml^?1 (0.0065 absorbance/μM). Optimal conditions and the selectivity of this enzyme toward formaldehyde are described.     

协同催化荧光法测定痕量钴的研究

基于在硼酸 硼砂介质中,钴和三乙醇胺协同催化过氧化氢氧化还原型罗丹明6G的反应,建立了协同催化荧光法测定痕量钴的新方法。钴的检出限为0.011ng/mL;测定范围0.016～0.80ng/mL。方法已用于小麦粉,玉米粉,VB12和人尿液等样品中痕量钴的测定。     

Flow-injection fluorimetric determination of nabam and metham

A simple and sensitive flow-injection fluorimetric method was developed to determine nabam or metham in water and cereal samples. The procedure is based on the oxidation of these pesticides by thallium(III) with the concomitant formation of fluorescent thallium(I). Lineal calibration graphs were obtained between 0.25 and 2.56 muml(-1) for nabam, and between 0.26 and 2.65 mug ml(-1) for metham. The sampling rate was 80 samples h(-1). The method was satisfactorily applied to the direct analysis of water, wheat, barley and oat samples spiked with nabam or metham.