Rapid Methods in Analytical Chemistry

This article presents the most recent research in analytical chemistry concerning the development of rapid methodologies covering the period from 2009 up until today. In this context, different useful analytical methods have been developed based mainly on typical techniques such as gas chromatography, liquid chromatography, mass spectrometry, electrophoresis, electroanalytical chemistry, and biosensors. The analytical features of these methods have allowed the analysis of samples of different natures, such as environmental, food, pharmaceutical, and biological type, in which wide classes of analytes are promptly determined. The main advantages of these methods are included and discussed in this review regarding novelty, rapidity, sensitivity, selectivity, and costs. It is concluded that the development of rapid methods is still a growing trend in analytical chemistry and that gas- and liquid-chromatography mainly coupled to different modes of mass spectrometry are the most common anal

Simultaneous determination of copper and iron by solvent extraction and first derivative spectrophotometry

A simple, sensitive and selective first derivative spectrophotometric method has been developed for the determination of copper and iron in mixtures. The method is based on the recovery of the analytes, by liquid-liquid extraction, Integrated reaction with 5-pheny1-3-(4-pheny1-2-pyridiny1)- l,2,4-triazine (PPT) and perchlorate in dichioroethane and on the subsequent direct derivative spectrophotometric measurement using the zero-crossing approach for determination of both analytes. Copper and Iron were thus determined in the ranges 50 - 2500 ng/ml and 2–120 ng/ml, respecttvely, in the presence of one another. The detection limits achieved (3σ) were found to be 17 ng/ml of copper and 0.7 ng/ml of iron. The relative standard deviations were in all instances less than 3.1%. The proposed method was applied to the determination of both analytes in well water and the results were consistent with those provided by the AAS standard method

Multivariate optimization of pressurized solvent extraction of alkylphenols and alkylphenol ethoxylates from biosolids

In this study, a methodology for pressurized solvent extraction of alkylphenols (APs) and alkylphenol ethoxylates (APEOs) from biosolids was optimized by utilizing a biosolid natively containing these compounds at a high concentration level. Optimization of the extraction was carried out through a multivariate analysis experimental design with a central composite design (CCD) producing the following optimum values for the variables: temperature of 129 degrees C, extraction time per cycle of 34 min in two cycles and acetone as extraction solvent. Upon comparison with Soxhlet extraction, this methodology turned out to be more efficient for the extraction of APEOs and of similar efficiency for APs. On the other hand, the methodology is considerably faster than Soxhlet and uses a smaller amount of extraction solvent. Concentrations of 204 +/- 20 and 1053 +/- 23 mg kg(-1) for nonylphenol and nonylphenol-ethoxylate, respectively, were determined in the biosolid sample assayed

Programmable flow-based dynamic sorptive microextraction exploiting an octadecyl chemically modified rotating disk extraction system for the determination of acidic drugs in urine

© 2014 Elsevier B.V. A novel automatic sorptive microextraction approach combining sequential injection-based programmable flow with rotating disk sorptive extraction (RDSE) is proposed for the clean-up and concentration of low polarity organic species in urine samples. Non-steroidal anti-inflammatory drugs (NSAIDs), namely, ketoprofen, naproxen, diclofenac and ibuprofen, were selected as model analytes in a proof-of-concept design, and they were further determined by liquid chromatographic (LC) assays. The extracting phase consisted of octadecyl (C18) chemically bonded silica embedded in a polytetrafluoroethylene (PTFE) substrate. The thin film was immobilized onto the surface of an in-house prepared rotating PTFE disk in a dedicated flow-through chamber. The programmable flow-based microextraction method operates under kinetic principles and features software-controlled sample loading and dynamic sorptive unidirectional-flow microextraction for as little as 10min, followed by matri

Determination of pesticides in river water using rotating disk sorptive extraction and gas chromatography-mass spectrometry

The rotating disk sorptive extraction (RDSE) technique was applied to the determination of pesticides in aqueous samples. Pesticides of different polarities were considered in this study: chlorpyrifos, diazinon, fenvalarate, cyhalothrin, cypermethrin, lindane and malathion. The sorptive/desorptive behavior of the pesticides was studied using a rotating disk containing a polydimethylsiloxane (PDMS) phase on one of its surfaces. The analyte polarity was a significant factor in the extraction time; shorter extraction times were required for the more apolar pesticides. The optimum variables for the extraction of all analytes were: extraction time of 3 h, sample volume of 25 mL, rotational velocity of the disk 1250 rpm, desorption time of 30 min using methanol. For pesticides with values of Log Kow > 4, the extraction time can be reduced to 30 min for a quantitative extraction. Under these conditions, recoveries between 76% and 101% were obtained for the target pesticides, and the repeatab

Determination of trace amounts of cobalt by solvent extraction-second derivative spectrophotometry

A sensitive derivative spectrophotometric method is described for the determination of microamounts of cobalt based on the integration of liquid-liquid separation and reaction, in dichloroethane, of the analyte with 3-(4-phenyl-2-pyridinyl)-5-phenyl-1,2,4-triazine (PPT) and 2,4,6-trinitro-phenol (picric acid). Cobalt was thus determined in the range 7.2-500 ng/ml. The method has a high selectivity with a detection limit of 2.2 ng/ml. The relative standard deviations were 3.2 and 1.5% for 20 and 100 ng/ml cobalt, respectively. The proposed method was applied to the determination of the analyte in vitamins. © 1993

Flow-through polarographic cell for flow-injection analysis. Determination of nifedipine in pharmaceutical formulations

Artículo de publicación ISIA simple design of a polarographic flow-through cell is proposed in which a conventional dropping mercury electrode (DME) is used as working electrode, and a mercury pool and a platinum wire are used as the reference and counter electrodes, respectively. The mercury droplets falling from the DME coalesce with the pool, and a fairly constant hold-up cell volume is achieved by controlled removal of the mercury from the pool at an equivalent flow rate than that of the DME. The analytical features of the cell are illustrated by flow-injection (FI) determination of the nitro derivative nifedipine in pharmaceuticals. The flow-through defector can be used either amperometrically, under continuous flow operation, or voltammetrically in quiet solution, under continuous flow-stopped flow mode. Under continuous flow operation of;he eel!, the sampling rate obtained was 120 h(-1). The repeat-ability of the analytical signals, expressed as RSD, was always lower than 2.1%. The recovery of nifedipine in synthetic tablet formulations was 99.8 +/- 0.6%

Liquid chromatography–time-of-flight high-resolution mass spectrometry study and determination of the dansylated products of estrogens and their hydroxylated metabolites in water and wastewater

© 2018, Springer-Verlag GmbH Germany, part of Springer Nature. A method combining liquid chromatography with a dual-probe ultraspray electrospray ionization (ESI) source and time-of-flight high-resolution mass spectrometry (LC-ESI-TOF/MS) was developed for the simultaneous determination of four steroidal sex hormones, estrone (E1), 17β-estradiol (E2), 17α-ethinyl estradiol (EE2), and estriol (E3), as well as five of their hydroxylated metabolites, 2-hydroxyestrone (2-OHE1), 4-hydroxyestrone (4-OHE1), 16α-hydroxyestrone (16-OHE1), 2-hydroxyestradiol (2-OHE2), and 4-hydroxyestradiol (4-OHE2), in water samples in a short chromatographic run of 10 min. Derivatization of the analytes was optimized using dansyl chloride as the derivatizing agent. Under optimal positive ionization conditions, the following signals, which had not been previously reported, were observed (with theoretical values of m/z 377.1373 for 2- and 4-OHE1 and 378.1452 for 2- and 4-OHE2), corresponding to doubly derivatiz

Polarographic behaviour and determination of nitrofurantoin, chloramphenicol and related compounds

The polarographic behaviour of nitrofurantoin and chloramphenicol have been studied in pyridine - formic acid buffer and tetramethylammonium chloride solution at pH 4.3. The E<inf>1/2</inf> versus pH and iym versus pH relationships show that the E<inf>1/2</inf> values are pH dependent and that the current is independent of pH except when acid - base equilibria affect it. The difference in E<inf>1/2</inf> values (230 mV) makes simultaneous determination possible. Simultaneous determinations of both drugs were performed in a concentration range suitable for application to pharmaceutical formulations and body fluids. Other nitro derivatives can also be determined without interference. The standard additions technique provided results as satisfactory as the use of a calibration graph. The proposed method has the advantage over previously used electrochemical methods of not requiring prior separations

Simultaneous determination of copper and iron by second derivative spectrophotometry using mixtures of ligands

A highly sensitive and selective second derivative spectrophotometric method has been developed for the determination of copper and iron in mixtures. The method is based on the separation of the analytes by liquid-liquid extraction as picrate ion pairs. Iron-picrate, reacts in the organic phase of DCE with 5-phenyl-3-(4-phenyl-2-pyridinyl)-1,2,4-triazine (PPT). Similarly the copper-picrate reacts with 2,9-dimethyl-4,7-diphenyl-1,10-phenantroline (bathocuproine). The extracts were evaluated directly by derivative spectrophotometric measurement, using the zero-crossing approach for determination of copper and graphic method for iron. Iron and copper were thus determined in the ranges 8-120 ng ml-1 and 8-125 ng ml-1, respectively, in the presence of one another. The detection limits achieved (3σ) were 2.9 ng ml-1 of iron and 2.8 ng ml-1 of copper. The relative standard deviations were in all instances less than 2.1%. The proposed method was applied to the determination of both analytes i