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.     

Sensitivity enhancement for inductively-coupled plasma atomic emission spectrometry of cadmium by suction-flow on-line ion-exchange preconcentration

A column of iminodiacetate chelating resin is used to preconcentrate cadmium by a factor of 25-fold for a 5-ml sample. The sampling rate was 25 h^?1, and the detection limit 0.05 ng Cd²⁺ ml^?1. The r.s.d. for 0.1 μg Cd²⁺ ml^?1 was 2.2% (n = 10). This technique was applied to the determination of cadmium in certified biological reference materials and waste-water samples.     

An extraction-spectrophotometric determination of palladium with 4-(2-pyridylazo)resorcinol in the presence of diphenylguanidine

A new, sensitive spectrophotometric determination of palladium has been developed, based on the extraction of the red Pd(II) chelate with 4-(2-pyridylazo)resorcinol in the presence of N,N′-diphenylguanidine into n-butanol; the sensitivity of the method according to Sandell is S = 1.12 μg cm^?2, ?₅₃₀ = 9.4 × 10⁴ liters mol^?1 cm^?1, and palladium can be determined at concentrations from 0.21 to 1.91 μg ml^?1.     

Atomic absorption spectrometric studies of the atomization of boron from a carbon rod atomizer

Boron (<20 μg ml^?1) in aqueous solutions gives no absorbance but addition of ascorbic acid, especially with titanium greatly enhances the signal, leading to a detection limit of 0.2 μg ml^?1 boron. The presence of uranium (<10 mg ml^?) only slightly decreases the boron signal.     

Colorimetric Determination of Propofol in Bulk form,Dosage Form and Biological Fluids

ABSTRACT

Propofol is coupled with 2, 6-dichloroquinone-4-chlorimide (DCQ) in a reaction buffered at pH 9.6 to give a colored product having an analytically useful maximum at 635 nm. The factors affecting the color generation were optimized and incorporated in the procedure. The reacted propofol has a molar absorptivity of 3.9 × 10^?4 L mol^?1 cm^?1, and Beer's law is obeyed for concentrations 1-5 μg ml^?1 with detection limit 0.25 μg ml^?1. The method was found applicable to biological fluids (plasma and urine) spiked with propofol at concentration levels 1-5 μg ml^?1 for plasma and 1-5 μg 0.5 ml^?1 urine (less sensitivity is obtained with urine volumes above 0.5 ml) with detection limits 0.28 μg ml^?1 for plasma and 0.4 μg 0.5 ml^?1 urine. The average recovery for the commercial preparation (1% w/v propofol emulsion intravenous injection for infusion) was 99.54% with an RSD of 1.05%. The method was validated by an adopted HPLC method. The results obtained by the HPLC method for the commercial preparation were statistically compared with the proposed method and evaluated at the 95% confidence limits.     

Determination of 1,4-thienodiazepines by liquid chromatography with spectrophotometric,amperometric and coulometric detection

Spectrophotometric, amperometric and coulometric methods of detection for the liquid chromatographic determination of four 1,4-thienodiazepines were compared. The effects of several experimental parameters on the separation and sensitivity of the method was evaluated. A mobile phase consisting of methanol—water (60 + 40) and containing ammonium acetate buffer (pH 7) appeared to be optimal when using a 4-μm Novapak ODS column. The amperometric and coulometric detectors, equipped with glassy carbon electrodes, were operated at +1.05 V vs. Ag/AgCl. The limits of detection obtained ranged from 0.05 to 0.2 μg ml^?1 for spectrophotometric detection, from 0.05 to 0.2 μg ml^?1 for amperometric detection and from 0.006 to 0.02 μg ml^?1 for coulometric detection.     

Indirect determination of fluoride in waters with lanthanum alizarin complexone and inductively-coupled plasma emission spectrometry

Fluoride is determined indirectly by measurement of the La II 333.75-nm line in the lanthanum/alizarin complexone/fluoride complex. The ternary complex is extracted into hexanol containing N,N-diethylaniline and the extract is introduced directly into the plasma. Related to water samples, the detection limit (3σ, concentration factor 5) is 0.59 ng ml^?1 fluoride, calibration is linear up to 1.2 μg ml^?1 and the relative standard deviation for 0.04 μg ml^?1 is 2.6%. Alkali, alkali elements and most anions do not interfere. The method is applied in the analysis of river water, coastal seawater and drinking water.     

Selective Kinetic Spectrophotometric Determination of Nitrite in Food and Water

Abstract

A highly selective and sensitive method for the kinetic spectrophothometric determination of sub-microgram amounts of nitrite has been development based on its reaction with Nile blue 2B in acidic medium. The reaction is monitored spectrophotometrically at 595 nm at a fixed time of 4.5 min. The change in absorbance at 595 nm is related to the concentration of nitrite in the range 0.005 - 1.100 μg.ml^?1 The detection limit is 0.001 μg.ml^?1. The relation standard deviation is 1% for 0.020 μg.ml^?1 of nitrite for ten replicate measurements. Most common anions and cations do not interfere. The procedure was applied to the determination of trace amounts of nitrite in sausage and water.     

Molekülabsorptionsspektrometrie bei elektrothermischer verdampfung in einer graphitrohrküvette: Teil 7. Untersuchung der erdalkali-halogen-molekülabsorptionen,bestimmung von Fluorid- und Chloridspuren durch die molekülabsorption von MgF- und MgCl-molekülen

(Molecular absorption spectrometry with electrothermal volatilization in a graphite tube. Part 7. A study of molecular absorption of alkaline earth halides and determination of traces of fluoride and chloride based on molecular absorption of MgF and MgCl moleculesv)The molecular absorption of alkaline earth halides, generated by volatilization in a normal graphite tube, is reported. Intense absorption bands were found only with MgF and MgCl molecules. These molecules are used for the determination of fluoride and chloride, respectively. Fluoride can be determined at 268.3 nm or 358.2 nm; for 10-μl injections, the linear ranges are, respectively, 0–6 μg ml^-1 and 0–35 μg ml^-1, with sensitivities (0.01 absorbance) of 2.4 ng and 7.5 ng. Chloride can be determined at 376.3 nm; response is linear up to 15 μg ml^-1, with a sensitivity of 5.8 ng if copper ions are added. Optimal conditions, interferences and mechanisms are discussed.     

Extraction studies of metal complexes with some macrocyclic tetraaza ligands and xanthene dyes : Spectrophotometric determination of Cadmium(II) with Tetramethyltetraazacyclotetradecane and Erythrosin A

The liquid-liquid extraction of ion-pair complexes of zinc(II), copper(II) and cadmium(II) is described. The macrocyclic ligands 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane (4Me-cyclam-14) and rac-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane (Tet b) are used with xanthene dyes as the counter ions. The apparent extraction constants (D′_c) are reported. The sequences of extraction efficiency of both ligands are related to the structure of the complexes. The apparent molar absorptivity of the Cd(4Me-cyclam-14)—erythrosin A ion-associate is 1.1 × 10⁵ l mol^? cm^?1. The calibration graph is linear over the range 0—10^?5 M, which allows even 0.05 μg ml^?1 cadmium to be determined in a 0.5 M sodium hydroxide medium. No interference was observed from Ni²⁺, Pb²⁺, Zn²⁺, Mg²⁺, Sn⁴⁺, Ga³⁺, Al³⁺ and Fe³⁺. Interferences were Cu²⁺, Hg²⁺, Ag⁺ and large anions.     

Determination of aniline in vegetable oils by diazotization and coupling in a microemulsion medium

A microemulsion containing sodium dodecyl sulphate and n-pentanol in a mass ratio of 1 : 4, water and a vegetable oil was investigated using pseudo-tenary phase diagrams. The medium can co-solve important amounts of vegetable oils and aqueous solutions over a wide range of ionic strengths. A procedure for the determination of 1.4–140 μg ml^?1 of aniline in vegetable oils using ionic diazotization and coupling reactions was developed. The absorbance was measured in an optically clear microemulsion containing 4% or 20% of oil. The procedure is much simpler and rapid than the official chromatographic methods and gives almost the same limits of detection (ca. 05 μg ml^?1) using no more than 1 ml of sample. The repeatability for 30 μg ml^?1 aniline was 2%. Acid-base titrations in the microemulsion medium permitted the evaluation of the protonation constant of the dye.     

Fluorimetric determination of mebendazole and flubendazole in pharmaceutical dosage forms after alkaline hydrolysis

The selective and very sensitive fluorimetric determination of mebendazole and flubendazole is based on alkaline hydrolysis and adsorption on Whatman 42 filter paper. Limits of detection are 0.1 μg ml^?1 and 0.5 μg ml^?1, respectively, with linear response sponse up to 10 μg ml^?1 and 50 μg ml^t?1. The fluorescence produced is very stable (λ_em = 460 nm) and the method is applicable to anthelmintic pharmaceutical preparations.     

Spectrophotometric determination of copper with α, β, γ, δ-tetraphenylporphine trisulfonate

Water-soluble porphyrin, α, β, γ, δ-tetraphenylphorphine trisulfonate (TPPS, H₂R), was found to be a very useful agent for both the direct spectrophotometric determination and the photometric titration of copper(II). The molar absorptivity of H₄R²⁺ at 434 nm is 5.0·10⁵ and the spectrophotometric sensitivity is 0.00013 μg Cu cm^?2 for A=0.001. Beer's law is followed in the range 0.006 μg–0.06 μg Cu ml^?1. Among twenty-two elements examined, only zinc(II) seriously interfered. Acid dissociation constants and salt effects on the spectra of TPPS were evaluated.     

Determination of Molybdenum in Human Urine by Spectrophotometric Method using Thiazolylazo Compounds as Chromogenic Reagents

ABSTRACT

Four azo compounds based on diazotization of 2-aminobenzothiazole have been synthesized and characterized by elemental analysis as well as different spectroscopic techniques. The potentiality of the prepared compounds as new chromogenic reagents for the spectrophotometric determination of Mo⁶⁺ was studied by extensive investigation of optimum conditions favouring the formation of the coloured complexes. Beers law is obeyed in the concentration range 0.2-8.5 μg ml^?1 whereas Ringbom optimum concentration range was 0.8-7.5 μg ml^?1. The detection limit was 0.05 μg ml^?1. The molar absorptivity and Sandell sensitivity of the formed complexes are calculated. The effect of interfering ions on the determination of Mo⁶⁺ was investigated. The relative standard deviations for six replicate determinations of 5.0 μg ml^?1 of Mo⁶⁺ are 1.23, 1.47, 1.05 and 1.38 % using reagents I, II, III and IV, respectively. The proposed method has been applied to investigate the amount of Mo⁶⁺ in human urine samples. The molybdenum levels found between 0.5-2.1 μg/100 ml.     

Flow-injection spectrophotometric determination of cobalt by extraction as tetrathiocyanatocobaltate(II) with the ethylenebis(triphenylphosphoniu) cation

Cobalt (0–10 μg) may be determined spectrophotometrically at 625 nm after flow-injection extraction into chloroform of the ion associate ethylenebis(triphenylphosphonium) tetrathiocyanatocobaltate(II). The carrier stream contained 10% (w/v) ammonium fluoride and the reagent stream contained 0.5% (w/v) ethylenebis (triphenylphosphonium) bromide and 5% (w/v) ammonium thiocyanate. The injection rate was 20 h^?1. The calibration graph is linear up to 20 μg ml^?1 and detection limit is 0.23 μg ml^?1 cobalt, based on injection volumes of 500 μl. The system has been applied to the determination of cobalt in a range of tool steels.     

Use of diode-array detectors for the simultaneous spectrophotometric determination of calcium and magnesium by flow injection

A method for the simultaneous flow injection spectrophotometric determination of calcium and magnesium with Arsenazo III based on the use of diode-array detector and merging zones is described. The method is applicable to the resolution of mixtures in which the chromogenic reagent has a high absorbance and its spectrum strongly overlaps those of its complexes. In resolving the mixtures, the excess reagent is considered as another component. Quantitation is based on the normal absorbance and first-derivative absorbance spectra. The method is applied to 0.2–1.5 μg ml^?1 Ca and 0.1–1.0 μg ml^?1 Mg. The analysis rate is 50 h^?1.     

Flow-injection spectrophotometric determination of ascorbic acid by reduction of vanadotungstophosphoric acid

Ascorbic acid may be determined spectrophotometrically at 360 nm based on reduction of vanadotungstophosphoric acid using flow-injection analysis. The carrier stream was distilled water and the reagent streams were buffer solution (pH 3.0), 1.735 × 10^?3 M dodecatungstophosphoric acid and 1.735 × 10^?3 M sodium vanadate. The injection rate was 80 h^?1. The calibration graph was linear up to 80 μg ml^?1 ascorbic acid and the relative standard deviation for the determination of 20 μg ml^?1 ascorbic acid was 1.5% (n=10). The detection limit was 1.0 μg ml^?1 ascorbic acid, based on an injection volume of 250 μl. The system was applied to the determination of ascorbic acid in vitamin C tablets.     

Automated stopped-flow system in pharmaceutical and clinical analysis : Kinetic determination of acetaminophen in formulations and serum by using the iron(II)—2,4,6-tris(2-pyridyl)-s-triazine

The development of automated stopped-flow spectrophotometric systems, their potential in automated routine determinations using kinetic and fast equilibrium techniques and several examples of applications are briefly reviewed. The use of a compact, inexpensive laboratory-made stopped-flow system for the measurement of reaction rates and a fast equilibrium method for the determination of acetaminophen in formulations and serum are described. The reaction-rate method is based on monitoring the oxidation of acetaminophen by iron(III) in the presence of the chelating agent 2,4,6-tris(2-pyridyl)-s-triazine to form a highly absorbing complex of iron(II). The calibration graph is linear in the range 20–200 μg ml^?1, with a precision of 0.8–2.6%, a detection limit of 5.5 μg ml^?1 and a measurement throughput of 120 per hour. Common excipients do not interfere and the analysis of commercial formulations gave results similar to those of a reference method. The optimization of the experimental conditions was done by a kinetic study of the reaction and some kinetic parameters are given.The method for the determination of acetaminophen in serum is based on a rapid measurement of the absorbance of the reaction mixture after a delay time of 15 s in the presence of chlorpromazine, which catalyses the reaction. Acetaminophen is isolated by extraction with ethyl acetate and the calibration graph is linear in the range 0.5–6 μg ml^?1 with a detection limit of 0.04 μg ml^?1 and a precision of 1.5%. The proposed method showed a decreased interference from drugs that also react with iron(III).     

Inductively-coupled plasma atomic emission spectrometric determination of boron based on generation of methyl borate

Boron is converted to methyl borate, distilled and condensed, and selectively volatilized at 50°C into the plasma without interference from methanol, which quenches the plasma. The 3σ detection limit is 40 ng ml^?1 boron, the calibration graph is linear up to 10 μg ml^?1 and the r.s.d. 3.0% for 2.0 μg ml^?1 (n = 10). Boron is determined in plant-tissue and steel standards.     

Preconcentration of copper with the ion-pair of 1,10- phenanthroline and tetraphenylborate on naphthalene

A solid ion-pair material produced from 1,10-phenanthroline and tetraphenylborate on naphthalene provides a simple, rapid and fairly selective means of preconcentrating copper from up to 1000 ml of aqueous samples (about 200-fold concentration is possible). Copper is quantitatively adsorbed in the pH range 1.6–10.4 at a flow rate of 3 ml min^?1. The solid mass (0.2 g) is dissolved from the column with 5 ml of dimethylformamide (DMF) and copper is measured by atomic absorption spectrometry at 324.7 nm. Linear calibration is obtained for 2–28 μg of copper in 5 ml of DMF solution. Replicate determination of 14 μg of copper gave a mean absorbance of 0.220 (n = 7) with a relative standard deviation of 1.5%. The sensitivity for 1% absorption was 0.093 μg ml^?1. After optimization, the method was applied to determine trace copper in standard reference materials, natural waters, beverages and hair.