New Spectrophotometric Method for Sulfite Determination

Abstract

A highly selective spectrophotometric method for the determination of aqueous sulfite was developed. Sulfite was found to react with o-phthaldialdehyde in presence of ammonia yielding a deep blue colored complex the absorbance of which is sensitive to trace sulfite concentrations. The method is simple, very sensitive, and convenient for the determination of as little as 5X10^?6 M sulfite. The molar absorptivity of the colored complex is about 1.2X10⁴ L cm^?1 mol^?1. The proposed method is more sensitive and selective for sulfite than the widely used Ellman reagent method. Absorbance is measured at 628 nm which is the best of the two absorption maxima that are exhibited by the compound.     

Isolation and Identification of Drugs of Forensic Interest by High Performance Reverse Phase Ion Pair Partition Chromatography

Abstract

A method is presented for the isolation and identification of milligram or microgram quantities of drugs of forensic interest. High performance reverse phase ion pair partition chromatography is performed on a 9.4 millimeter internal diameter microparticulate octadecylsilane column employing a water, methanol, acetic acid, alkylsulfonate mobile phase. Subsequent to collection from the liquid chromatograph, a simple extraction is performed followed by Infrared (IR) analysis and/or solid probe Mass Spectrometry (MS). A study is presented using phenylpropanolamine hydrochloride and ephedrine hydrochloride as a test model for the determination of the optimum concentration of counter ion required for a semi-preparative separation. The method is applied to an LSD seizure from a clandestine laboratory, methamphetamine in a street exhibit, and an amobarbital - secobarbital mixture in a multi-barbiturate capsule.     

Development of a cloud point extraction and preconcentration method for chromium(III) and total chromium prior to flame atomic absorption spectrometry

A sensitive and selective method has been developed for the determination of chromium in water samples based on using cloud point extraction (CPE) preconcentration and determination by flame atomic absorption spectrometry (FAAS). The method is based on the complexation of Cr(III) ions with Brilliant Cresyl Blue (BCB) in the presence of non-ionic surfactant Triton X-114. Under the optimum conditions, the preconcentration of 50 mL of water sample in the presence of 0.5 g/L Triton X-114 and 1.2 × 10⁻⁵ M BCB permitted the detection of 0.42 μg/L chromium(III). The calibration graph was linear in the range of 1.5–70 μg/L, and the recovery of more than 99% was achieved. The proposed method was used in FAAS determination of Cr(III) in water samples and certified water samples. In addition, the developed CPE-FAAS method was also used for speciation of the inorganic chromium species after reduction of Cr(VI) to Cr(III) using a thiosulphate solution of 120 mg/L in the presence of Hg(II) ion as a stabilizer.     

Machine-Learning-Enabled Virtual Screening for Inhibitors of Lysine-Specific Histone Demethylase 1

A machine learning approach has been applied to virtual screening for lysine specific demethylase 1 (LSD1) inhibitors. LSD1 is an important anti-cancer target. Machine learning models to predict activity were constructed using Morgan molecular fingerprints. The dataset, consisting of 931 molecules with LSD1 inhibition activity, was obtained from the ChEMBL database. An evaluation of several candidate algorithms on the main dataset revealed that the support vector regressor gave the best model, with a coefficient of determination (R2) of 0.703. Virtual screening, using this model, identified five predicted potent inhibitors from the ZINC database comprising more than 300,000 molecules. The virtual screening recovered a known inhibitor, RN1, as well as four compounds where activity against LSD1 had not previously been suggested. Thus, we performed a machine-learning-enabled virtual screening of LSD1 inhibitors using only the structural information of the molecules.     

Reversed Phase Liquid Chromatographic Separation of Lysergic Acid Diethylamide (LSD) and Lysergic Acid Methylpropylamide (LAMPA)

Abstract

A fast and convenient procedure is described for the HPLC separation of LSD and LAMPA. These compounds are separated by a reversed phase (C18) procedure using a binary solvent system of methanol and pH 3 phosphate buffer. Under these conditions all compounds are eluted in a retention volume of 27 mL or less. This procedure allows a forensic sample to be identified as LSD and to eliminate LAMPA as a possibility.     

Polarographic Study Op Trinitrotriphenylamine

Abstract

The paper describes the conditions of polarographic reduction of trinitrotriphenylamine. The reduction occurs in 2 steps of similar height (one for trihydroxylaminotriphenyl-amine and the other for triaminotriphenylamine). The method allows the polarographic determination of trinitrotriphenylamine between 0.1–0.5 mg/ml. In the presence of silver ions, the polarographic steps are shifted to more negative potentials, which indicates formation of a compound of silver with triaminotriphenylamine.     

Indirect Microdetermination of Hydroxide Ions by Atomic Absorption Spectrophotometry

Abstract

A simple indirect atomic absorption spectrophotometric method is described for the determination of hydroxide ions. The method is based on the reduction of silver ions which takes place when hydroxide sample is treated with silver (I) solution in presence of manganese(II) ions. The unconsumed silver is determined by atomic absorption spectrophotometry. The effects of a number of factors have been studied and the method was employed for the determination of free alkali in paper samples.     

Targeting Cancer with PCPA‐Drug Conjugates: LSD1 Inhibition‐Triggered Release of 4‐Hydroxytamoxifen

Targeting cancer with small molecule prodrugs should help overcome problems associated with conventional cancer‐targeting methods. Herein, we focused on lysine‐specific demethylase 1 (LSD1) to trigger the controlled release of anticancer drugs in cancer cells, where LSD1 is highly expressed. Conjugates of the LSD1 inhibitor trans‐2‐phenylcyclopropylamine (PCPA) were used as novel prodrugs to selectively release anticancer drugs by LSD1 inhibition. As PCPA‐drug conjugate (PDC) prototypes, we designed PCPA‐tamoxifen conjugates 1 a and 1 b , which released 4‐hydroxytamoxifen in the presence of LSD1 in vitro. Furthermore, 1 a and 1 b inhibited the growth of breast cancer cells by the simultaneous inhibition of LSD1 and the estrogen receptor without exhibiting cytotoxicity toward normal cells. These results demonstrate that PDCs provide a useful prodrug method that may facilitate the selective release of drugs in cancer cells.     

Direct Kinetic Determination of Bromhexine Hydrochloride in Pharmaceutical Formulations

Abstract

A very simple, automatic, fast method for the photometric determination of bromhexine hydrochloride based on the application of kinetic methodology and the stopped-flow mixing technique to the coupling reaction between the diazotized bromhexine derivative and N-(1-naphthyl)ethylenediamine is proposed. The high initial rate of this reaction allows analytical measurements to be made within only 0.5–1 s, which makes the method applicable to automatic routine analyses. The calibration graph is linear over the range 1.5–65.0 μg mL^?1 and the precision (as %RSD) is less than 2%. The presence of antibiotics such as penicillins and cephalosporins in a 100-fold excess has no effect on the analyte determination. The proposed method was satisfactorily used for direct analysis of pharmaceutical formulations containing these antibiotics.     

Kinetic-Spectrophotometric Determination of Tellurium (IV) by Its Catalytic Effect on the Reduction of Thionine by Sodium Sulfide in Cationic Micellar Medium

A simple and highly sensitive method is proposed for the determination of Te(IV) by its catalytic effect on the reduction of thionine by sodium sulfide in the presence of cetyl trimethyl ammonium bromide as a micelle media. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of thionine at 600 nm with a fixed time of 0.5-2.5 min from initiation of the reaction. Tellurium can be measured in the concentration range of 0.6-500.0 ng/mL, with a limit of detection of 0.3 ng/mL Te(IV). The influence of more than thirty potential interfering ions was studied on the determination of tellurium. The relative standard deviation for ten replicate measurements of 0.020 and 50.0 ng/mL Te(IV) was 2.1 and 1.9%, respectively. The method was applied for the determination of tellurium in synthetic samples.     

A New Spectrophotometric Method for the Determination of Maneb in Commercial Formulations

Abstract

A new rapid, selective and sensitive method has been developed for the determination of maneb using pyrocatechol-violet(PV) as chelating reagent in the pH range of 7.5–11.0 in the presence of CTAB producing a complex which shows maximum absorption at 640 nm. Working range of the method is 0.2–3.0 μg ml^?1 maneb (manganese ethylenebisdithiocarbamate). The molar absorptivity of the color system is 79600 1 mol^?1 cm^?1 and Sandell's sensitivity is 0.0033 μg cm^?2. The reproducibility of the method has been checked by the 10 replicate analysis of 15 μg of maneb in 10 ml of solution. The method is quite sensitive and has been applied for the determination of maneb in various commercial samples, crops, grains and synthetic samples.     

Spectrophotometer Determination of Nitrite Using Salbutamol sulphate as a Reagent

Abstract

A simple spectrophotometric method for the trace determination of nitrite (NO^? ₂) is described. Nitrite is reacted with Salbutamal sulphate in acidic medium which gives a yellow colour in alkaline medium (?pH 7) and can be determined in the presence of several cations and anions. Beer's law is obeyed in the range of 1.8 to 27.6 ppm of nitrite with the molar absorptivity 1.8 × 10³ 1 × mole^?1 × cm^?1 at 4l0 nm. The proposed method can also be utilized for the determination of nitrate (NO^? ₃) after its reduction to nitrite. The method has been applied for the determination of various samples containing traces of nitrite.     

Determination of Hg in water and wastewater samples by CV-AAS following on-line preconcentration with silver trap

An online mercury preconcentration and determination system consisting of cold vapor atomic absorption spectrometry (CV-AAS) coupled to a flow injection (FI) method was studied. The method was developed involving the determination of ng/L levels of mercury retained on the silver wool solid sorbent. Experimental conditions such as sample volume, flow rate, stability of the column and effect of foreign ions on the determination of trace amounts of mercury were optimized. The detection limit is 3 ng/L and dynamic range 10–250 ng/L require only 50 mL of sample. The relative standard deviations (RSD) of the determinations are below 4%. The presence of common metal ions, such as K+, Na⁺, Cu²⁺, Pb²⁺, Fe³⁺, Ni²⁺, and Mn²⁺, does not interfere with the measurement of mercury by this method. The method was successfully applied to the determination of mercury in water and wastewater samples.     

Etude Electrochimique d'Un Nouveau Neuroleptique: La Loxapine

Abstract

The electrochemical characteristics of loxapine have been determined using D.C., A.C. and D.P. polarography and cyclic voltamnetry. The reduction of the azomethin group is influenced by the vicinity of the protonable piperazin ring. Adsorption phenomena have been observed, especially in alkaline medium. The determination of loxapine can be easily carried out quantitatively in acidic medium, and an application of the method for the determination of loxapine in tablets has been realized. The simultaneous detection of loxapin and clothiapine, which are structurally related neuroleptics differing only by an oxygen or a sulfur atom in the central heterocycle is not possible; nevertheless, loxapine has been detected in neutral or alkaline medium in the presence of clozapine, which differs from the two precedents by the presence of a nitrogen as heteroatom.     

Environmental Status of Cobalt and Its Microdetermination With 7-Nitroso-8-Hydroxyquinoline-5-Sulfonic Acid In Waters,Aquatic Weeds and Animal Tissues

Abstract

A method is presented for the spectrophotometric microdetermination of cobalt (II) in fresh waters, aquatic weeds, and animal tissues employing 7-nitroso-8-hydroxyquinoline-5-sulfonic acid. the method enables direct determination of cobalt (II) in presence of a large number of anions and cations commonly associated with cobalt, and is adequate for determining the metal in the concentration range of 0.001–10 ppm, which is commonly encountered in environmental samples.     

Determination of Amygdalin in Blood Serum

Abstract

A rapid, simple and sensitive method for the repetitive determination of amygdalin in human serum has been developed. The method is based on the β-gluco-sidase-catalyzed hydrolysis of amygdalin to glucose, which subsequently is oxidized in the presence of glucose-oxidase. The sample is injected into a continuously circulated reagent mixture and the oxygen depletion is monitored with a three-electrode amperometric system. Amygdalin in the range 0.02 to 2 mg/ml has been determined with relative errors and relative standard deviation of about 2%. The maximum determination rate is 700 injections/h. Recovery studies are also reported for amygdalin in serum calibration and controls.     

Spectrophotometric Determination of Nitrite Ion or Chloramine T with Gallein-Molybdenum Complex and Cobalt (II) with Gallin and Hydrogen Peroxide in a Micellar Media

Abstract

A simple and sensitive spectrophotometric method for the determination of nitrite ion or chloramine T is proposed utilizing a gallein-molybdenum complex in the presence of N-hexadecyltrimethylammonium chloride in acidic media. Also, a sensitive catalytic spectrophotometric procedure for determi     

Electrochemical Behavior of Dopamine at a Mercury Electrode in the Presence of Citrate: Analytical Applications

Abstract

Dopamine can be determined by voltammetric methods using a mercury electrode, previously oxidized at +0.30 V. The oxidation product formed is stabilized in the presence of citrate and undergoes reduction at ?0.31 V. This work describes the electrochemical behavior of dopamine at a mercury electrode in the presence of citrate and its application in the development of a square‐wave voltammetric method for the dopamine determination in pharmaceutical formulations. The method was in‐house validated for determination of dopamine in injectable formulations. The detectability of the method was 0.02 µg ml^?1.     

Photometric Endpoint Detection in the Edta Titration of Zinc in the Presence of Manganese

Abstract

A method has been developed for the simultaneous determination of manganese and zinc or just zinc in the presence of manganese using a photometric technique for determination of the zinc end-point. The accuracy of the results is comparable to that obtained with conventional methods but, in most cases, there is a slight increase in precision. The endpoint is much easier to determine photometrically.     

Spectrophotometric Assay of Penem (SCH 29482) by Reaction with Imidazole

Abstract

A rapid method is described for the determination of SCH 29482. This is based on the spectrophotometric measurement at 386 nm of the product of reaction with imidazole formed at 35°Cin a 1.5 M imidazole and 2×10^?3M mercuric chloride solution at pH 7.50. The method, which permits detection of concentrations of SCH 29482 as low as to 2.8, μg/ml, is reproducible and specific for intact SCH 29482 in the presence of degradation products. The molar absorptivity for the chromophore formed is 2.54×l0⁴ I mol^?1cm^?1.