A salting-out assisted liquid-liquid microextraction procedure for determination of cysteine followed by spectrophotometric detection

Microextraction with smartphone detection of thiocyanate in saliva of tobacco smokers using paper-based analytical method

This study presents a novel, cost-effective approach involving spectrophotometric and smartphone paper-based (SPB) methods and a distinctive salting-out air-assisted dispersive microextraction procedure to quantify thiocyanate in saliva samples. The method relies on the inhibitory effect of thiocyanate on quinoneimine dye formation during the Emerson reaction with sodium hypochlorite. Spectrophotometry quantifies the extracted dye by monitoring quinoneimine color intensity reduction at 525 nm. In the SPB method, extracted dye is applied to a paper strip, a smartphone captures the colored paper, and an application analyzes red, green, and blue components. All analyte determination and extraction variables were explored. Both methods exhibit good linearity (10-100 μg/L) with a coefficient of determination of 0.9991 and a limit of detection of 7.5 μg/L for the spectrophotometric method, and a coefficient of determination of 0.9988 and a limit of detection of 8.8 μg/L for the SPB method. The calculated values for the enrichment factor and extraction recovery of the developed extraction methodology were 46% and 93%, respectively. The methods detect thiocyanate in saliva samples, producing results comparable to a validated method.

Validated UPLC-MS/MS method for the determination of ivosidenib in rat plasma: Application to a pharmacokinetic study

Ivosidenib (AG-120) is an unlisted, but estimated to be valid, oral inhibitor for isocitrate dehydrogenase 1 (IDH1) in the phase Ⅰ study of IDH1-mutated acute myeloid leukemia (AML) patients. This paper presents the investigation and validation of a rapid, effective, qualitative and quantitative determination method of ivosidenib in rat plasma by ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). The samples were treated using acetonitrile precipitation to remove protein influence. Then, the supernatant was extracted to analyze plasma concentration traits. In the UPLC system, acetonitrile and water containing 0.1% formic acid were selected as a cosolvent mobile phase, applying a gradient elution to isolate compounds in a C18 column. Mass detections were performed on a triple quadruple mass spectrometer in positive ion mode. Electroshock characteristic fragment ionization was used for m/z 583.95→214.53 for ivosidenib for quantitative determination, m/z 583.95→186.6 for qualitative determination, and m/z 492.06→354.55 for IS. The selectivity, linearity, stability, accuracy and precision were verified by reaching the guideline criteria from European Medicine Agency (EMA) and the Food and Drug Administration (FDA). The calibration curve was linear over the concentration range of 2–2,000 ng mL−1 for ivosidenib in rat plasma with a lower limit of quantification (LLOQ) of at least 2 ng mL−1. Additionally, there was no distinct matrix effect or carry-over phenomenon. The method was successfully established and applied to separate ivosidenib from plasma, with the entire analytical process being performed within 3 min for each sample, which shows high-efficiency and convenience for further studies of ivosidenib.

Radial basis function-artificial neural network (RBF-ANN) for simultaneous fluorescent determination of cysteine enantiomers in mixtures

The determination of chiral compounds is critically important in chemical and pharmaceutical sciences. Cysteine amino acid is one of the important chiral compounds where each enantiomer (L and D) has different effects on fundamental physiological processes. The unique optical properties of nanoparticles make them a suitable probe for the determination of different analytes. In this work, the water-soluble thioglycolic acid (TGA)-capped cadmium-telluride (CdTe) quantum dots (QDs) were applied as optical nanoprobe for the simultaneous determination of cysteine enantiomers. The difference in the kinetics of the interactions between L- and D-cysteine with CdTe QDs is used for multivariate quantitative analysis. Multivariate methods are superior to univariate methods in determining the concentration of each enantiomer in the mixture without the information about the total chiral analyte concentration. As a nonlinear calibration method the radial basis function -artificial neural network (RBF-ANN) model was more successful in predicting L-and D-cysteine concentrations than the linear partial least squares regression (PLS) model.

Homogeneous liquid-liquid extraction as an alternative sample preparation technique for biomedical analysis

Liquid-liquid extraction is a widely used technique of sample preparation in biomedical analysis. In spite of the high pre-concentration capacities of liquid-liquid extraction, it suffers from a number of limitations including time and effort consumption, large organic solvent utilization, and poor performance in highly polar analytes. Homogeneous liquid-liquid extraction is an alternative sample preparation technique that overcomes some drawbacks of conventional liquid-liquid extraction, and allows employing greener organic solvents in sample treatment. In homogeneous liquid-liquid extraction, a homogeneous phase is formed between the aqueous sample and the water-miscible extractant, followed by chemically or physically induced phase separation. To form the homogeneous phase, aqueous samples are mixed with water-miscible organic solvents, water-immiscible solvents/cosolvents, surfactants, or smart polymers. Then, phase separation is induced chemically (adding salt, sugar, or buffer) or physically (changing temperature or pH). This mode is rapid, sustainable, and cost-effective in comparison with other sample preparation techniques. Moreover, homogeneous liquid-liquid extraction is more suitable for the extraction of delicate macromolecules such as enzymes, hormones, and proteins and it is more compatible with liquid chromatography with tandem mass spectrometry, which is a vital technique in metabolomics and proteomics. In this review, the principle, types, applications, automation, and technical aspects of homogeneous liquid-liquid extraction are discussed.

Determination of L-glutathione by spot test and spectrophotometric methods based on its interaction with phenazine

This research paper presents simple and quick eco-friendly spot test and spectrophotometric methods for the determination of L-glutathione. The spot test assay is based on the formation of a color complex with phenazine methosulphate and L-glutathione on a thin-layer chromatography plate followed by image analysis using a scanner as a detector. For analysis, the image was converted into red, green, and blue (RGB) histograms. A series of parameters that influenced the color formation were investigated, and under the optimal conditions, a good linearity was observed in the range of 200-1000 μg mL^-1 and 249-1000 μg mL^-1 of L-glutathione with correlation coefficients of 0.9907 for B and 0.9903 for G channels. For the spectrophotometric method, a good linearity was obtained in the range of 2.1-60 μg mL^-1 of L-glutathione concentration with a correlation coefficient of 0.9961. A mechanism of the reaction of L-glutathione with phenazine was proposed and confirmed by Fourier transform infrared and mass spectroscopy.

Fabrication of a sensitive colorimetric nanosensor for determination of cysteine in human serum and urine samples based on magnetic-sulfur, nitrogen graphene quantum dots as a selective platform and Au nanoparticles

A novel colorimetric nanosensor is reported for the selective and sensitive determination of cysteine using magnetic-sulfur, nitrogen graphene quantum dots (Fe₃O₄/S, N-GQDs), and gold nanoparticles (Au NPs). Thus, S, N-GQDs was firstly immobilized on Fe₃O₄ nanoparticles through its magnetization in the presence of Fe³⁺ in the alkali solution. The prepared Fe₃O₄/S, N-GQDs were dispersed in cysteine solution resulting in its quick adsorption on the surface of the Fe₃O₄/S, N-GQDs through hydrogen bonding interaction. Then, Au NPs solution was added to this mixture that after a short time, the color of Au NPs changed from red to blue, the intensity of surface plasmon resonance peak of Au NPs at 530 nm decreased, and a new peak at a higher wavelength of 680 nm appeared. The effective parameters on cysteine quantification were optimized via response surface methodology using the central composite design. Under optimum conditions, the absorbance ratio (A₆₈₀/A₅₃₀) has a linear proportionality with cysteine concentration in the range of 0.04-1.20 μmol L^-1 with a limit of detection of 0.009 μmol L^-1. The fabrication of the reported nanosensor is simple, fast, and is capable of efficient quantification of ultra traces of cysteine in human serum and urine real samples.

Spectrophotometric determination of lamotrigine in plasma samples: Ultrasound-assisted emulsification-microextraction based on a hydrophobic deep eutectic solvent followed by back-extraction

In this study, sensitive detection of lamotrigine in human plasma samples was realized at a low cost approach through ultrasound-assisted emulsification-microextraction based on using a hydrophobic deep eutectic solvent followed by back-extraction (USAEME-DES-BE) method. After extraction, detection and quantification of lamotrigine were done by spectrophotometry in the UV region. The hydrophobicity of the deep eutectic solvent not only eliminates the need of the third solvent as an emulsifying agent but also helps to retrieve lamotrigine from the DES by back-extraction to another aqueous phase. The back extraction process allowed the drug to be measured in the UV region. Central composite design in combination with a desirability function approach was applied for the optimization of the USAEME-DES-BE procedure. Essential factors in the method efficiency were discussed, such as back-extraction solution, time of back-extraction, the ratio of DES components, pH, the volume of DES, salt concentration, and sonication time. The method exhibited a wide dynamic linear range from 0.5 to 10 µg mL^-1 and a limit of detection of 0.15 μg mL^-1. The established method was successfully applied to determine lamotrigine in human plasma samples with satisfactory relative recoveries.

pH-responsive release system of topiramate transported on silica nanoparticles by melting method

Incorporating drugs into silica matrices by the melting method can be applied to obtain drug delivery systems because they are governed by electrostatic type interactions, hydrogen bonding and hydrophilic-hydrophobic interactions between the drug and the silica surface. the melting method is an environmentally correct tool since it is free of organic solvent, low cost and with easy execution for the incorporation of drugs in silicas. Drugs delivery systems are very important for improving the treatment of chronic diseases. Topiramate (TPM) is a potent antiepileptic used in high daily doses as it has low bioavailability. In this context, silica nanoparticles (NPS) were used as an inorganic matrix for TPM transport in (in vitro) release studies. The TPM was incorporated into the NPS by hot melt loading employing a new carrier preparation methodology (NPS/TPM) using a thermobalance (by Thermogravimetry-TG) with high temperature control system. The release study using dissolution media simulating gastrointestinal at pH 1.2 (stomach) and 7.4 (intestine), showed that NPS release TPM in a prolonged and pH-responsive manner. The drug was released at intestinal pH ensuring greater absorption, allowing fewer daily doses and less adverse effects. The kinetic study demonstrated the best fit to the zero-order model proving the pH-responsive profile of the developed system.

Development of dual-tool nanosensor for cysteine based on N-(1-naphthyl)ethylenediamine cation functionalized silver nanoparticles

In an accomplishment of development of silver nanoparticles (AgNPs) based nanosensor for cysteine in its anionic and neutral forms, we have preferred N-(1-naphthyl)ethylenediamine cation (NEDA⁺) stabilized AgNPs (NEDA-AgNPs), because NEDA⁺ is a fluorescent active ion and it imparts excellent stability to AgNPs. Surface Plasmon resonance (SPR) of AgNPs and fluorescence property of NEDA⁺ are thus useful for presenting NEDA-AgNPs as a dual-tool nanosensor for cysteine molecules. The surface adsorbed NEDA⁺ cations interact selectively with cysteine as a consequence, the particles get aggregated, which was monitored using spectrophotometric method. The fluorescence property of NEDA⁺ is heavily quenched in NEDA-AgNPs, which could be reversed in presence of cysteine. The spectrofluorimetric method was thus used for quantification of cysteine as well. The detection limits (LOD to LOL) of anionic cysteine are 0.1784-1.598 μM and 0.0842-2.0 μM, respectively in spectrophotometric and spectrofluorimetric methods. From a real sample matrix, the recovery results are excellent, >95%. For neutral cysteine, the sensitivity is a bit low; 0.308-2.8 μM for spectrophotometric and 0.131-2.8 μM for spectrofluorimetric methods. It is found that the anionic cysteine (K_asso = 2.24 × 10⁵ M^-1/4.02 × 10⁵ M^-1) binds surface adsorbed NEDA⁺ cations strongly than that of neutral cysteine (K_asso = 3.69 × 10⁴ M^-1/1.24 × 10⁵ M^-1). Thus, NEDA-AgNPs show its potentials for being a dual-tool nanosensor as well as dual-form nanosensor for quantification of cysteine in a sample which may be the attractive system to an analyst.

A sieve-conducted two-syringe-based pressurized liquid-phase microextraction for the determination of indium by slotted quartz tube-flame atomic absorption spectrometry

In this study, a new liquid-phase microextraction method termed sieve-conducted two-syringe-based pressurized liquid-phase microextraction (SCTS-PLPME) was developed as a preconcentration tool for indium. Here, two syringes were connected to each other by an apparatus to produce an environment subject to pressure. The pressure created between the two syringes by simultaneous movements of the syringe plungers (to and fro) generated an efficient dispersion and this eliminated the need for dispersive solvents. Determination of indium after preconcentration was carried out with a slotted quartz tube attached flame atomic absorption spectrometer (SQT-FAAS). The detection limit (LOD) and quantification limit (LOQ) of the developed method were calculated as 19.2 and 72.2 μg L^-1, respectively. The reliability and accuracy of the developed method was tested by performing recovery studies on lake water spiked at different concentrations and the obtained percent recoveries were between 101.2 and 106.9%.

A two-dimensional zinc(II)-based metal-organic framework for fluorometric determination of ascorbic acid, chloramphenicol and ceftriaxone

A two-dimensional zinc(II)-based metal-organic framework [Zn • (BA) • (BBI)] was synthesized from 1,2-benzenediacetic acid and 1,1'-(1,4-butanediyl) bis(imidazole) via a solvothermal reaction. The crystal exhibits good chemical stability in the pH range from 2 to 12, and strong fluorescence with excitation/emission maxima of 270/290 nm. The crystal is shown to by a viable fluorescent probe for the detection of ascorbic acid (AA) and the antibiotics chloramphenicol (CHL) and ceftriaxone (CRO). Fluorescence intensity of crystal dispersion is significantly quenched with increasing concentrations of AA/CHL/CRO. Quenching occurs even in the presence of other substances. The assay is fast (5 s) and has a low detection limit (1.6 ppb for AA, 12 ppb for CHL and 3.9 ppb for CRO). The crystal still has a good quenching effect on AA/CHL/CRO after washing and using for five times. The response of the probe is related to the interplay between the MOF and analytes via energy absorption competition. Graphical abstractSchematic diagram of preparing Zn • (BA) • (BBI) and responding to target analytes. BA: 1,2-phenyldiacetic acid; BBI: 1,1'-(1,4-butanediyl)bis(imidazole); Zn • (BA) • (BBI): Crystal chemical formula.

Chemiluminescent determination of L-cysteine with the lucigenin-carbon dot system

This work describes a new chemiluminescence (CL) system that is composed of lucigenin and carbon dots (CDs). The CDs display absorption peak at 260 nm and fluorescence with a emission peak centered at 524 nm (photo-excited at 470 nm). They were synthesized by hydrothermal treatment of starch and characterized by Fourier transform infrared spectroscopy, high resolution transmission electron microscopy, UV-vis absorption spectra and fluorescence spectra. The effects of oxygen and free radical scavengers on the CL system and on the CL spectra were investigated to elucidate the CL mechanism. It is found that L-cysteine (Cys) enhances the blue CL of the lucigenin-CD system by 59%. The finding was used to design a method for the determination of Cys. CL increases linearly in the 10.0 to 100 μM Cys concentration range, and the detection limit is 8.8 μM (at an S/N ratio of 3). The assay is highly selective over other amino acids. Conceivably, this novel CL system paves the way to numerous new assays based on the use of lucigenin. Graphical abstractSchematic representation of the carbon dots enhanced lucigenin chemiluminesence.

Salt-assisted liquid-liquid extraction in microchannel

In this study, for the first time, salt-assisted liquid-liquid extraction was performed in a microchannel system. The proposed design is based on the increase of contact surface area between target analytes and extracting phase during the sample and extracting phase transfer in microchannel. In this method, first sample solution, extracting solvent, and salt were mixed by stirrer and simultaneously delivered into a microchannel using a syringe pump. In order to optimize the influential parameters on the extraction efficiency of the proposed method, zidovudine and tenofovir disoproxil fumarate were selected as model analytes. The main parameters such as extracting solvent and its volume, salt amount, pH of sample solution, and microchannel shape, length, and its inner diameter were investigated and optimized. Under the optimized conditions, the proposed method was linear in the range of 0.1-30 µg/mL and R² coefficients were equal to 0.9922 and 0.9947 for zidovudine and tenofovir disoproxil fumarate, respectively. Extraction efficiency of the proposed method was compared with conventional salt-assisted liquid-liquid extraction. The results show that the proposed design has higher extraction efficiency than conventional salt-assisted liquid-liquid extraction. Finally, the proposed method was successfully applied for the determination of zidovudine and tenofovir disoproxil fumarate in plasma samples.