Analysis of volatile aldehyde biomarkers in human blood by derivatization and dispersive liquid-liquid microextraction based on solidification of floating organic droplet method by high performance liquid chromatography

Dispersive liquid-liquid microextraction for the high performance liquid chromatographic determination of aldehydes in cigarette smoke and injectable formulations

A dispersive liquid-liquid microextraction method (DLLME) combined with high performance liquid chromatography (HPLC) was developed for the extraction and determination of some aldehydes, such as benzaldehyde (BzA), butyraldehyde (BuA) and furfural (Fur) in mainstream cigarette smoke as well as BzA in injectable formulations. After trapping of combustion smoke into sulfuric acid with a laboratory-made smoking machine, aldehydes were converted into their hydrazone derivatives by the reaction with 2,4-dinitrophenylhydrazine (DNPH), and then rapidly extracted by DLLME. The effects of various experimental parameters on the derivatization and extraction were studied and optimized. Under the optimum extraction conditions, linear calibration curves in the range 0.025 to 1.0 μg/mL with correlation coefficients of 0.9980-0.9996 were obtained for studied aldehydes. Limit of detections (LODs) for BzA, BuA and Fur were found to be 14.2, 21.3 and 7.92 μg/L, respectively. The relative standard deviations (RSDs) for inter-and intra-day assays were lower than 8.50%. Average recoveries for spiked samples were in the range 88.0-109%. The proposed method was successfully applied to the determination of aldehydes in different real samples.

Recent advances in unique sample preparation techniques for bioanalysis

The extraction and/or purification of drugs and medicines from biological matrices are important objectives in investigating their toxicological and pharmaceutical properties. Many widely used methods such as liquid–liquid extraction or SPE, used for extracting, purifying and enriching drugs and medicines found in biological materials, involve laborious, intensive and expensive preparatory procedures, and they require organic solvents that are toxic to both humans and the environment. Recent trends are focused on miniaturization, high-throughput and automation techniques. All the advantages and disadvantages of these techniques and devices in biological analysis are presented, and their applications in the extraction and/or purification of drugs and medicines from biological matrices are discussed in this review.

Analysis of losartan and carvedilol in urine and plasma samples using a dispersive liquid–liquid microextraction isocratic HPLC–UV method

Background: A simple, precise and sensitive HPLC method has been developed for simultaneous determination of carvedilol and losartan in human plasma and urine samples. The analytes were extracted by a dispersive liquid–liquid microextraction method. A mobile phase of 15 mM sodium dihydrogen phosphate buffer (pH 4.0)/acetonitrile/2-propanol (70/27.5/2.5, v/v/v) was used to separate the drugs using a Waters® ODS column (250 × 4.6 mm) and detected by a UV detector at 222 nm. Results: The developed method is selective for studied drugs possessing a linearity range of 0.1–1.0 and 0.05–0.75 µg/ml, respectively, for losartan and carvedilol with precision <15%. The accuracy is better than 15% and the mean recovery of carvedilol and losartan was 98.9 and 100.2% for plasma and 100.7 and 100.5% for urine samples, respectively. Conclusion: The developed method is applicable for therapeutic drug monitoring and PK analyses.

Spectrophotometric determination of iron species using a combination of artificial neural networks and dispersive liquid-liquid microextraction based on solidification of floating organic drop

A dispersive liquid-liquid microextraction based on solidification of floating organic drop (DLLME-SFO) and artificial neural networks method was developed for the simultaneous separation/preconcentration and speciation of iron in water samples. In this method, an appropriate mixture of ethanol (as the disperser solvent) and 1-undecanol (as the extracting solvent) containing appropriate amount of 2-thenoyltrifluoroacetone (TTA) (as the complexing agent) was injected rapidly into the water sample containing iron (II) and iron (III) species. At this step, the iron species interacted with the TTA and extracted into the 1-undecanol. After the phase separation, the absorbance of the extracted irons was measured in the wavelength region of 450-600 nm. The artificial neural networks were then applied for simultaneous determination of individual iron species. Under optimum conditions, the calibration graphs were linear in the range of 95-1070 μg L(-1) and 31-350 μg L(-1) with detection limits of 25 and 8 μg L(-1) for iron (II) and iron (III), respectively. The relative standard deviations (R.S.D., n=6) were lower than 4.2%. The enhancement factor of 162 and 125 were obtained for Fe(3+) and Fe(2+) ions, respectively. The procedure was applied to power plant drum water and several potable water samples; and accuracy was assessed through the recovery experiments and independent analysis by graphite furnace atomic absorption spectrometry.

A novel approach in dispersive liquid-liquid microextraction based on the use of an auxiliary solvent for adjustment of density UV-VIS spectrophotometric and graphite furnace atomic absorption spectrometric determination of gold based on ion pair formation

This paper presents a novel approach to dispersive liquid-liquid microextraction (DLLME), based on the use of an auxiliary solvent for the adjustment of density. The procedure utilises a solvent system consisting of a dispersive solvent, an extraction solvent and an auxiliary solvent, which allows for the use of solvents having a density lower than that of water as an extraction solvent while preserving simple phase separation by centrifugation. The suggested approach could be an alternative to procedures described in the literature in recent months and which have been devoted to solving the same problem. The efficiency of the suggested approach is demonstrated through the determination of gold based on the formation of the ion pair [Au(CN)(2)](-) anion with Astra Phloxine (R) reagent and its extraction using the DLLME procedure with subsequent UV-VIS spectrophotometric and graphite furnace atomic absorption spectrometric detection. The optimum conditions were found to be: pH 3; 0.8 mmol L(-1) K(4)[Fe(CN)(6)]; 0.12 mmol L(-1) R; dispersive solvent, methanol; extraction solvent, toluene; auxiliary solvent, tetrachloromethane. The calibration plots were linear in the ranges 0.39-4.7 mg L(-1) and 0.5-39.4 μg L(-1) for UV-VIS and GFAAS detection, respectively; thus enables the application of the developed method in two ranges differing from one from another by three orders of magnitude. The presented approach can be applied to the development of DLLME procedures for the determination of other compounds extractable by organic solvents with a density lower than that of water.