Linear Calibration Curves Research Articles

Development, validation and application of a GC-MS method for quantification of glucose and lactate in vitreous humor

Develop and apply a GC-MS method for quantifying glucose and lactate in vitreous humor. In routine forensic toxicological screening, glucose and lactate are measured in vitreous humor to evaluate the ante-mortem glycaemic status and to identify possible lactate acidosis. Concentrations for both endogenous compounds are required in the assessment of hypo-, normo- or hyperglycaemic status before death. In our laboratory, no in-house chromatographic method was available and diluted vitreous humor samples had to be analysed by an external laboratory, using a spectrophotometric method validated for serum. Starting from a GC-MS method available for GHB and BHB, we investigated the simultaneous measurement of glucose and lactate to increase sample throughput. An analytical method was developed for analysis of glucose and lactate, based on an available GC-MS method used in-house for other analytes and on literature (Shojaee-Moradie et al., Journal of Mass Spectrometry 1996;31:961–966), employing a combination of two derivatisation reactions. Glucose required both oxime and trimethylsilyl derivatisation to achieve compatibility with GC-MS. For lactate, only the silylation step was necessary. Method validation was carried out using in-house prepared quality control samples. Authentic vitreous humor samples ( n = 100) were analysed in parallel between October 2021 and April 2022, comparing the results of the newly developed method to those from the external laboratory. The derivatisation time and calibration model were optimised. The method was validated according to the guideline on bioanalytical method validation provided by the European Medicines Agency. Linear calibration curves showed R 2 > 0.99 for glucose and lactate and the lower limit of quantification (LLOQ) was 12.5 mg/dL for both compounds. Spearman's ρ showed a strong, statistically significant correlation between the results obtained by the two labs ( P < 0.001; 0.836 for lactate, 0.963 for glucose). Bland–Altman plots were used to assess agreement between the measurements. For glucose, 11% of the analysed samples fell out of the 95% confidence interval; for lactate, only 9%. Deviant samples were re-analysed with the new method, yielding the same results, suggesting the possibility of deviant results by the spectrophotometric method. For lactate, the results of the developed method tended to show a small positive bias compared to those of the clinical lab. The established LLOQ was well below the postmortem cut-off values for determining hypoglycaemia and the measured glucose and lactate concentrations in most authentic samples. Results for the authentic samples showed good agreement between both methods and for both analytes. The developed and validated GC-MS based method has shown to be suitable for accurate measurement of glucose and lactate concentrations in vitreous humor.

Simple defocus laser irradiation to suppress self-absorption in laser-induced breakdown spectroscopy (LIBS)

This study introduces a novel and simple way to suppress the self-absorption effect in laser-induced breakdown spectroscopy (LIBS) by utilizing a defocusing laser irradiation technique. For this purpose, a Nd:YAG laser with a wavelength of 1,064 nm and repetition rate of 10 Hz with energy in the range of 10 mJ–50 mJ was used. The laser irradiation was focused by using a 150-mm-focal-length plano-convex lens onto the sample surface under defocusing of approximately –6 mm. Potassium chloride (KCl) and sodium chloride (NaCl) pellet samples were used to demonstrate this achievement. When the defocus position is adjusted to –6 mm for KCl and NaCl samples, the self-reversal in the emission lines of K I 766.4 nm, K I 769.9 nm, Na I 588.9 nm, and Na I 589.5 nm vanish. Meanwhile, the FWHM values of K I 766.4 and K I 769.9 nm are 0.29 nm and 0.23 nm, respectively, during –6 mm defocus laser irradiation, as opposed to 1.24 nm and 0.86 nm under tight focus laser irradiation. Additionally, this work demonstrates that, when the laser energy is changed between 10 and 50 mJ, no self-reversal occurs in the emission lines when –6 mm defocus laser irradiation is applied. Finally, a linear calibration curve was generated using KCl at a high concentration ranging between K concentrations from 16.6% to 29%. It should be noted that, even at such high K concentrations, the calibration curve is still linear. This means that self-absorption is almost negligible. This simple change in defocus laser irradiation will undoubtedly contribute to the suppression of the self-absorption phenomenon, which disrupts LIBS analytical results.

Development of Sequential Injection Analysis for the Determination of Lead in Vegetables

A sequential injection analysis incorporated with spectrophotometric method was developed for determination of lead, based on reaction of dithizone with lead producing pink complex and absorbance of the complex was measured at 515 nm. The analytical parameters of the system were optimized by univariate method such as reagent concentration, fl ow rate of reagent and injection volume. Linear calibration curve over the range of 0.02-0.08 mg L-1 and 0.1-2.0 mg L-1 lead was obtained. The detection limit of lead was 0.012 mg L-1. The relative standard deviations for fi ve replicate injections was 0.77-1.54% for intra-day and 0.86-1.80% for inter-day. The recovery of 98.75-101.20% was achieved with sample throughput of 45 samples per hour. The proposed method has been applied to the determination of lead in vegetable samples. The obtained results were in good agreement with those obtained by the ICP-MS standard method, verifi ed by the student t-test at the 95% confi dence level.

Use of zinc oxide nanoparticles for detection of fluoride in toothpaste gel

This study aimed to investigate the metal-binding effect of fluoride, contained in different commercial toothpaste gels; the study aimed to determine if the toothpastes contained excessive concentrations of fluoride, which result in white spot lesions. A spectrophotometric method that used spectrophotometric reagents, including zinc oxide nanoparticles and iron chloride, was used to determine fluoride distribution; the analysis was based on the selective attack of fluoride ions on metals. Fluoride concentrations between 0 and 1450 ppm were analyzed. Although the iron–fluoride complex was a more sensitive reagent, the zinc–fluoride complex could serve as a suitable alternative to it for fluoride analysis, partly because the method was less time consuming and more stable. The detection and quantification limits obtained from the linear calibration curves of the zinc–fluoride complexes, in deionized water, were 0.191:1 and 0.579:1 w/w ZnO, respectively. A model calibration curve was suggested to detect the unknown products of fluoride degradation. Dentists could use a fluoride treatment similar to the protocol used in this study, to prevent potential enamel demineralization, and exclude physical cavity preparation and restoration.

Diclofenac Concentrations in Post-Mortem Specimens-Distribution, Case Reports, and Validated Method (UHPLC-QqQ-MS/MS) for Its Determination.

The aim of the research was to establish a sensitive method for the quantification of diclofenac in postmortem samples. The developed method was applied in six cases: three fetuses in which the use of abortion pills by their mothers was suspected, one case of duodenal ulcer perforation, one case of traffic accident with fatal outcome, and one acute renal failure in which the distribution of diclofenac was examined. The analyses were performed using liquid–liquid extraction of postmortem samples and the quantification of diclofenac via ultra-high performance liquid chromatography, coupled with triple quadrupole tandem mass spectrometry. Gradient elution using a C18 column was applied. Electrospray ionization measurement in positive multiple reaction monitoring mode was used. Diclofenac-d4 was used as an internal standard. The validation parameters were as follows: lower limit of quantification: 0.5 ng/mL, linearity of calibration curve: 0.5–500 ng/mL, intra- and interday accuracies and precisions: not greater than 15%; recovery values: 72.0–102.2%, and matrix effect: 2.2–28.0%. The developed method enabled the determination of diclofenac in human postmortem biological fluids (blood, urine, vitreous humor, bile, and stomach content), tissues (placenta, kidney, liver, and heart), and in exhumated fetus bones, with high recovery, sensitivity, precision, and accuracy.

Electrochemical determination of vitamin B6 (pyridoxine) by reformed carbon paste electrode with iron oxide nanoparticles

This work aims to introduce a simple high-performance sensitive electrochemical sensor of reformed carbon paste (CP) with iron oxide nanoparticles (IONs). It was developed to determine one of the most important drugs called vitamin B6 in a medium of phosphate buffer (PBS) over pH ranging from 5.0 to 8.0. The electrochemical and surface characterization was achieved by different techniques comprising electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), differential pulse voltammetry (DPV), and scanning electron microscopy (SEM). The studied effects were, pH, buffer, interference, scan rate, accumulation time, and calibration plot. The sensitive electrode produced a linear calibration curve in a concentration range from 8.88 up to 1000.0 µM, with limits of detection and qualification estimated at 9.06 and 30.2 µM, respectively Also, this method was established in human urine real samples and pharmaceutical drugs which have been shown a good result for vitamin B6 detection.

Electrodeposition of bismuth at a graphene modified carbon electrode and its application as an easily regenerated sensor for the electrochemical determination of the antimicrobial drug metronidazole

Metronidazole is a well-known antimicrobial drug that belongs to the nitroimidazole family of antibiotics. It has been widely used in the treatment of infections, but its accumulation in aquatic environments is an emerging concern. In this study a glassy carbon electrode was modified with graphene (Gr) nanoplatelets and bismuth. Both the Gr and Bi were electrochemically deposited onto the glassy carbon and the modified electrode was employed in the electrochemical detection of metronidazole. At the modified electrode, the reduction of metronidazole was found to be an adsorption-controlled reaction. The optimised sensor, which was fabricated within 6 min, exhibited good selectivity in the presence of various inorganic and organic compounds, good recovery in tap water, and exhibited a linear calibration curve extending from 0.005 to 260 μM, with a limit of detection of 0.9 nM. The sensor was easily regenerated through the simple oxidation of the Bi deposit followed by a 100 s reduction period in the Bi(III) solution to give a newly generated surface. Good reproducibility was achieved using this simple regeneration approach.

A new voltammetric sensor for penicillin G using poly(3-methylthiophene)-citric acid modified glassy carbon electrode

In this study, an effective voltammetric sensor was developed for determination of penicillin G by electropolymerization of 3-methylthiophene with citric acid on glassy carbon electrode. Penicillin G selective electrode was prepared in water:acetonitrile (1:1) mixture containing 0.1 M sodium perchlorate as electrolyte medium with cyclic voltammetry. Then, the electrochemical behavior of penicillin G on poly(3-methylthiophene) based membrane modified electrode was investigated by cyclic voltammetry, differential pulse voltammetry and differential pulse stripping voltammetry techniques. When the penicillin G responses of the modified glassy carbon electrode were compared with the bare glassy carbon electrode responses, it was seen that the selectivity and sensitivity of the penicillin G responses of the modified electrode significantly increased. A linear calibration graph for penicillin G was obtained in the concentration range of 0.07 to 4.0 mM with the prepared electrode. The R2 value was calculated as 0.9999 from the linear calibration curve. The limit of detection and limit of quantitation of the poly(3-methylthiophene)-citric acid modified glassy carbon electrode for penicillin G were calculated as 8 μM and 28 μM, respectively. In addition, the developed electrode for the detection of PeG was applied to milk samples. The recovery efficiency of the poly(3-methylthiophene)-citric acid modified glassy carbon electrode was obtained in the range of 93 % and 103 % for three different milk samples. As a result; the modified electrode can be used for residue penicillin detection in food and biological samples.

Determination of short-chain fatty acids by N,N-dimethylethylenediamine derivatization combined with liquid chromatography/mass spectrometry and their implication in influenza virus infection.

Short-chain fatty acids (SCFAs) are the end products of the fermentation of complex carbohydrates by the gut microbiota. Although SCFAs are recognized as important markers to elucidate the link between gut health and disease, it has been difficult to analyze SCFAs with mass spectrometry technologies due to their poor ionization efficiency and high volatility. Here, we present a novel and sensitive method for the quantification of SCFAs, including C2-C6 SCFAs and their hydroxy derivatives, by liquid chromatography/tandem mass spectrometry (LC-MS/MS) upon N,N-dimethylethylenediamine (DMED) derivatization with a run time of 10min. Moreover, the quantification method of DMED-derivatized SCFAs in intestinal contents using isotope-labeled internal standards was also established. The method validation was performed by analyzing spiked intestinal samples; the limits of detection and quantification of SCFAs with this method were found to be 0.5 and 5 fmol, respectively; the recovery was greater than 80% and good linearity (0.9932 to 0.9979) of calibration curves was obtained over the range from 0.005 to 5000pmol/μL; the intraday and interday precisions were achieved in the range of 1-5%. Furthermore, the validated method was applied to analyze SCFAs in the cecum and colon contents of mice infected with the influenza virus. The results showed that the concentration of most of the SCFAs tested here decreased significantly in a time-dependent manner after the infection, suggesting a possibility that SCFAs in intestinal samples could be used as severe disease markers. Overall, we here successfully developed a simple, fast, and sensitive method for SCFA analysis by LC-MS/MS combined with DMED derivatization. The method for the quantification of SCFAs will be a useful tool for both basic research and clinical studies.

Thiosemicarbazone-triazole bearing siloxy framework for the detection of Hg2+ and Cu2+ ions and their potent cytotoxic activity

The designing of chemosensors is a fascinating and growing research field among the scientific community. This article emphasizes the synthesis of thiosemicarbazone-triazole bearing siloxy framework (5a-5c)by utilizing an effective and biocompatible Cu(I) catalyzed “Click Silylation” approach. All the newly synthesized compounds (4a-4cand5a-5c)have been well-characterized by various spectroscopy techniques like Infrared, Nuclear Magnetic Rasonance (1H NMR and 13C NMR), mass spectrometry and Thermogravimetric Analysis. The photophysical properties of5aand its precursor alkyne4awere investigated by employing UV-vis spectroscopy, which showed the selective and sensitive recognition of Hg2+ and Cu2+ ions with negligible interference from different metal ions. All types of the binding interaction between chemosensors (4a/5a)and Hg2+/Cu2+ ions got reversed upon addition of salt of ethylene diamminetetraacetic acid. The association constant and limit of detection values were also determined by plotting BH-plot and linear calibration curve respectively. Furthermore, the cytotoxic activity results indicate that the siloxy compounds were found to be excellent postulants compared to ascorbic acid and hence can be applied for biological purposes.

Imaging electrochemiluminescence layer to dissect concentration-dependent light intensity for accurate quantitative analysis

As one of most advanced transduction techniques, electrochemiluminescence (ECL), such as that generated by tris(2,2′-bipyridyl)ruthenium (Ru(bpy)32+), has been extensively used in chemical sensing and analysis, but the reaction mechanism has not been fully resolved. Aiming at gaining insightful mechanistic information on the coreactant system involving (Ru(bpy)32+) and tri-n-propylamine (TPrA), herein we investigate the variation of thickness of ECL layer (TEL) with the concentration ratio of (Ru(bpy)32+) to TPrA (cRu/cTPrA) by ECL microscopy. Using carbon fiber as the working electrode, TEL was observed to grow with the increase of cRu/cTPrA remarkably. In conjunction with finite element simulations, the extension of ECL layer was rationalized to be associated with the incremental contribution of so-called “catalytic route”. This route offers an additional channel of generating remote light emission in solution, apart from surface-confined emission produced by the “oxidative-reduction route”. Given the quantitative analysis of coreactant-type analytes is often based on the calibration curve, namely a graph generated by plotting the measured light intensity of a series of standard solutions against their concentrations, the contribution of “catalytic route” particularly at a low concentration of analyte (equivalent to a relatively large cRu/cTPrA) is favorable to the analytical sensitivity. Moreover, the presence and absence of this route will result in a nonlinear and linear calibration curve, respectively, for example in the detection of TPrA and pyruvate. The results highlight the microwire-based imaging approach can provide insightful mechanistic information and help unveil the concentration dependence of measured ECL intensity for precise quantitative analysis.

An ionic covalent organic framework loaded with terbium-based probe for the sensing and removal of chrysolepic acid: Characterization and ratiometric behavior

Chrysolepic acid (CA) is a widely-used chemical product and considered hazardous for ecosystem and human health, which makes its removal as important as its sensing. In this work, a composite structure (denoted as Tb–COF, with a structural composition of C 162 H 120 N 18 O 12 Br 3 ·C 21 H 9 N 3 O 12 Tb 1 ) was synthesized, consisting of an ionic covalent organic framework (denoted as I–COF, with a structural composition of C 162 H 120 N 18 O 12 Br 6 ) and a terbium-based dopant/emitter (denoted as Tb(DPA) 3 3− , DPA = pyridine-2,6-dicarboxylic acid). Tb–COF was identified by means of single crystal analysis, infrared (IR) spectra, X-ray diffraction (XRD), porosity analysis, SEM (scanning electron microscope)/TEM (transmission electron microscope) and elemental composition analysis. The dopant loading level in Tb–COF was determined as 41%. Both green emission from Tb-based dopant and red emission from I–COF host were observed. The presence of CA quenched I–COF emission but enhanced dopant emission, resulting in ratiometric sensing signal. A linear calibration curve was demonstrated, with fitting equation of I/I 0 = 1.223 + 6.709 × 10 5 M −1 [CA], R 2 = 0.996, within [CA] region of 0–9 μM. The key sensing/adsorption process was revealed as the adsorption of I–COF micropores for CA molecules, which endowed Tb–COF with a good selectivity over competing species. I–COF adsorption/removal feature for CA was tentatively evaluated. • An ionic covalent organic framework was synthesized and modified with luminescent ionic Tb(III) emitter. • The as-synthesized Tb–COF showed weak Tb(III) emission and strong red COF emission. • After adding CA, Tb(III) emission was increased with COF emission weakened greatly, showing sensing behavior. • The adsorption and removal performance of Tb–COF was investigated as well.

Determination of naproxen by using differential pulse voltammetry with poly (aniline-2-sulfonic acid) modified boron doped diamond electrode

In this study, an electrochemical sensor based on a boron doped diamond electrode (BDDE) was developed for the determination of naproxen (NAP) using a poly(aniline-2-sulfonic acid)/boron doped diamond electrode, p(A2SA/BDDE). Polymerization of A2SA was conducted in a water/acetonitrile (1:1) mixture containing 0.1 M sodium perchlorate (NaClO4) on bare BDDE and the electrochemical properties studied by cyclic voltammetry in ferricyanide/KNO3 solution. The prepared p(A2SA/BDDE) was used for detection of NAP. Effects of parameters such as monomer type and concentration, the number of cycles, and scan rate were investigated using differential pulse voltammetry (DPV) in phosphate buffer containing 0.75 mM NAP. The effect of electrolyte type and pH on DPV responses to NAP were also studied. The oxidative current peak stem from NAP concentration observed at 1.1 V potential. A linear calibration curve was obtained in the range of 0.05–1.00 mM NAP concentration. Correlation coefficient (R2), detection limit, and quantification limit were calculated as 0.9944, 0.0328 mM, and 0.1093 mM, respectively. In conclusion, it may be claimed that the modified electrode constructed in this work can be used successfully as a naproxen-selective membrane due to its ease of preparation, high R2 value, and good reproducibility.

RATIO DERIVATIVE SPECTROPHOTOMETRIC MONITORING AND PHYTOREMEDIATION OF PANTOPRAZOLE

Recently much attention has been placed to identify the presence of emerging contaminants with special reference to pharmaceutical wastes by the development of specific techniques for detection and monitoring of environmental pollutants at the trace level. The present work aims to investigate the application of a non-destructive, selective and less expensive ratio derivative spectrophotometric method for the monitoring of pantoprazole present in the pharmaceutical binary mixture and wastewater without their prior separation. The linear calibration curve was obtained in the concentration range of 1.0-75.0 ppm for pantoprazole (r2 = 0.994). It was found that significant amounts of pantoprazole can be recovered from laboratory prepared binary mixtures (98.73 %, 100.69 % and 103.46 %), distilled water (98.90 %, 100.13 % and 94.57 %) and wastewater (103.60 %, 98.38 % and 104.73 %) via spike method with known concentrations (40.0 ppm, 50.0 ppm and 60.0 ppm respectively) of pharmaceuticals viz. omeprazole and pantoprazole. Interestingly, selected macrophytes (water hyacinth and water lettuce) were capable to remove pantoprazole (~60 %) from waste water samples.

Application of small amplitude oscillatory rheology measurements for estimating residual rennet activity in rennet whey

The relationship between (very low) rennet activity (RA) levels and rennet coagulation time (RCT) is non-linear, and its determination is time consuming, with accuracy depending on an objective RCT. Here, RCT was determined by small amplitude oscillatory rheology and the Carlson, Hill and Olson's spiking technique was modified to estimate the unknown residual RA directly from a linear calibration curve of RCT against 1/RA created using the serum phase of the reconstituted skim milk (RSM) utilised for preparation of the rennet whey. The estimated residual RA mL−1 of the rennet whey could be obtained by spiking the rennet whey with a known RA derived from the linear range of the calibration curve. This observation was confirmed by a commonly used reverse-phase high-performance liquid chromatography (RP-HPLC) method. Using this information, a simple general model that estimates RA partitioning based on total volume of whey separated from the curd could be proposed.

Kağıt Tabanlı Kolorimetrik Yöntemle Askorbik Asit (Vitamin C) Tayini

Ascorbic acid (AA) is the most important water-soluble organic biomolecule with antioxidant properties, known as vitamin C in many foods and beverages. The number of different methods developed for the determination of antioxidant properties of foods is increasing. Paper-based microfluidic analytical devices (µPADs) have been applied in the development of fast, simple, and cost-effective field analyzes in recent years. These developed analyzes are used as an alternative to laboratory-equipped qualitative and quantitative analyzes. In this study, a paper-based colorimetric method was applied for the determination of ascorbic acid. Geometric shapes with hydrophobic barrier were created on Whatman filter papers with the help of a wax pen. Using the principle of reduction of the AgNO3 solution in the presence of antioxidants in these shapes, the images of the color transformations were recorded with the help of a smartphone camera. ImageJ software was used in the image processing to determine the concentrations of standard AA solutions. Linear calibration curves for AA concentrations in the 0,2 to 1,0 mM range were obtained in grayscale and RGB (Red-Green-Blue) values. The coefficient of determination of the calibration curves (R2), respectively; 0,9389 for grayscale, 0,9728, 0,9628, and 0,8859 for Red, Green, and Blue channels. High-Performance Liquid Chromatography (HPLC) was used as a standard method to compare with the paper-based method. Freshly squeezed orange juice was used for the determination of ascorbic acid in the real food sample. The ascorbic acid value determined in orange juices by HPLC and colorimetric methods were statistically compared.

DETERMINATION OF ACTIVE INGREDIENT IN TAMSULOSIN DRUG BY USING HPLC

This study was aimed to development and modification the method of analysis for active ingredient in Tamsulosin drug by using high performance liquid chromatography (HPLC) also determined shelf life and storage conditions for Tamsulosin. Chromatographic conditions utilized stationary phase C18 (250*4.6) mobile phase 0.05Nmixture of di hydrogen ortho phosphate and Acetonitrile 55:45 , preserve the flow rate near (1ml/min) and length of wave has been 275nm, The retention time found to be 10 minute for the HPLC process . The Tamsulosin assay result was found to be 99.93% . The calibration curve linearity analysis results showed a strong linear relationship in the concentration range (10-200ppm) and the correlation coefficient, slope and intercept value were 0.9933,11796,190017, respectively The percentage recovery was found 99%. LOD value was found to 0.00053 µg/ml and LOQ value was found to 0.0016 µg/ml , Precision was found to be 99.49% Robustness was found to 99.69%. Our proposed procedure confirmed a group of merits such as Linear ,accurate ,precise ,and robust , could be recommended for determination of Tamsulosin.

Novel LC–MS Method development and Validation for Characterization of Talazoparib, an Anti-cancer drug and its forced degradation behavior

The present work aimed to develop a novel liquid chromatography and mass spectrometry (LC-MS) method for the determination of Talazoparib (TZPB) in pharmaceutical forms. Analysis of TZPB was performed in mobile phase of Methanol, Acetonitrile and 0.2% Perchloric acid in the ratio of 70:28:02 (v/v) as mobile phase and separation was carried on Prontosil ODS C18 Column (150 X 4.6mm, 5μ) as stationary phase. The degradative property of the TZPB under different stress conditions were evaluated using mass spectral analysis of the eluted compounds. The characterization of column eluents was carried on mass spectrometer operated in a positive ESI (electrospray ionization) mode and analyzed in single quadrupole analyzer. The mass spectra corresponding to molecular weight of TZPB was observed at m/z of 381 and characteristic mass fragmentation was observed in the spectra (m/z of 339 to 204). The linear calibration curve for TZPB was achieved in the range of 0.1–150 ng/mL (r = 0.9994) with a very sensitive detection limit (0.03ng/mL) and quantification limit (0.1ng/mL). The method was validated for parameters such as accuracy, precision, ruggedness, robustness etc and the results of the validation parameters are within acceptable limit at all quality control levels. The forced degradation studied for conditions such as acid, base, oxidation, UV light and thermal degradation conditions. The method can separate and detect the degradation compounds formed during the stress study. The forced degradation compounds formed were characterized using mass spectral study and a total 9 different degradation compounds were identified in the study. Hence the method can apply in identification and quantification of degradation compounds of TZPB in quality control and formulations.

Eye-Visible Oxygen Sensing via In-Situ Synthesizing Blue-Emitting Cu(I) Cluster in Red-Emitting COF: Characterization and Performance.

Covalent organic frameworks (COFs) have shown virtues of well-defined and uniform pores with structural diversity, including the shape, size and even chemical nature of pores. These features are excellent for the application of O2 gas optical sensors. In this paper, two oxygen probes based on halogen-bridged Cu cluster were in-situ synthesized in the micropores of COFs, to allow a uniform distribution. The resulting composite samples were characterized in detail to confirm the successful probe loading. The doping level was determined as ~22%. The halogen-bridged Cu clusters showed blue emission peaking at ~440 nm, while COF host showed red emission peaking at 630 nm. These halogen-bridged Cu clusters had long emissive lifetime of ~6.7 μs and high emission quantum yield of 0.30 in pure N2 atmosphere. Given pure O2 atmosphere, lifetime and quantum yield were quenched to 2.5 μs and 0.11, showing oxygen-sensing possibility. A linear oxygen-sensing calibration curve was observed, with sensitivity of 12.25, response time of 13 s and recovery time of 38 s. Sample emission color was changed from blue to red when testing atmosphere was changed from pure N2 to pure O2, which was detectable by eyes.

Smartphone as a Portable Detector for Thin-Layer Chromatographic Determination of Some Gastrointestinal Tract Drugs.

Thin-layer chromatography (TLC) is an effective and simple technique for screening, evaluating, and quantifying low-quality and counterfeit pharmaceutical products. Smartphones have recently been used as accessible, cheap, and portable detectors that can replace more complicated analytical detectors. In this work, we have developed a simple and sensitive TLC method utilizing a smartphone charged-coupled device (CCD) camera not only to verify and quantify some gastrointestinal tract drugs, namely, loperamide hydrochloride (LOP) and bisacodyl (BIS), but also to detect acetaminophen (ACT) as a counterfeit drug. Both drugs (LOP and BIS) were chromatographed separately on a silica gel 60 F254 plate as a stationary phase under previously reported chromatographic conditions, using ethyl acetate:methanol:ammonium hydroxide (24:3:1, by volume) and ethyl acetate:methanol:glacial acetic acid (85:10:5, by volume) as developing systems to determine LOP and BIS, respectively. Universal stains, namely, iodine vapors and vanillin, were used to visualize the spots on the TLC plates to get a visual image using the smartphone camera and a spotlight as an illumination source with no need for a UV illumination source. The spot intensity was calculated using a commercially available smartphone application for quantitative analysis of the studied drugs utilizing ″acetaminophen″ as an example of a counterfeit substance. Rf values were calculated using the recorded images and found to be 0.77, 0.79, and 0.74 for LOP, BIS, and ACT, respectively, providing drug identity. Linear calibration curves using the smartphone–TLC method were obtained between the luminance and the corresponding concentrations over the ranges of 2.00–10.00 μg/mL and 1.00–10.00 μg/mL with limits of detection of 0.57 and 0.10 μg/mL for LOP and BIS, respectively. The suggested method was validated according to the International Conference of Harmonization (ICH) guidelines. The method was then successfully applied for the qualitative and quantitative determination of LOP or BIS as an example for gastrointestinal tract drugs in pure form and in their pharmaceutical dosage formulations. The proposed method is considered as a perfect alternative to traditional reported densitometric methods due to its simplicity, easy application, and inexpensiveness. No previously reported methods utilizing smartphones have been published for the determination of the studied drugs. The developed approach is considered the first TLC method using smartphones for the determination of some gastrointestinal tract drugs in their pure form and in pharmaceutical formulations.