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Local administrations are increasingly demanding real-time continuous monitoring of pollution in the sanitation system to improve and optimize its operation, to comply with EU environmental policies and to reach European Green Deal targets. The present work shows a full-scale Wastewater Treatment Plant field-sampling campaign to estimate COD, BOD5, TSS, P, TN and NO3-N in both influent and effluent, in the absence of pre-treatment or chemicals addition to the samples, resulting in a reduction of the duration and cost of analysis. Different regression models were developed to estimate the pollution load of sewage systems from the spectral response of wastewater samples measured at 380-700 nm through multivariate linear regressions and machine learning genetic algorithms. The tests carried out concluded that the models calculated by means of genetic algorithms can estimate the levels of five of the pollutants under study (COD, BOD5, TSS, TN and NO3-N), including both raw and treated wastewater, with an error rate below 4%. In the case of the multilinear regression models, these are limited to raw water and the estimate is limited to COD and TSS, with less than a 0.5% error rate.
The study aimed at developing a new spectrophotometric method for determining the pectin content. Take commercial pectin as an example, and the method is based on the reaction of copper ions with pectin to produce copper pectate. The spectrophotometer was used to measure the remaining content of copper ions so as to calculate the pectin content. This method eliminated the weight step and avoided the error associated with it. Effects of reaction time, temperature, and pH on absorbance were also studied. Additionally, the accuracy of this method was verified. It indicated excellent repeatability and accuracy with the relative standard deviation of 2.09%. In addition, three different plant types were used to demonstrate the reliability of the method. To summarize, this method can be widely used for the determination of pectin content in many materials.
This study aimed to quantify the active biological compounds in C. officinalis flowers. Based on the active principles and biological properties of marigolds flowers reported in the literature, we sought to obtain and characterize the molecular composition of extracts prepared using different solvents. The antioxidant capacities of extracts were assessed by using spectrophotometry to measure both absorbance of the colorimetric free radical scavenger 2,2-diphenyl-1-picrylhydrazyl (DPPH) as well as the total antioxidant potential, using the ferric reducing power (FRAP) assay.
Tumor-derived exosomes may provide biomarkers for cancer treatment. Using sputtering technology, an affinity-based device to capture exosomes was developed using nanoporous substrate (NPG)-coated silicon microscopy. Immunology-based techniques detect and purify exosomes using gold coating with a specific antigen. Inverted fluorescent microscopy was used to detect target exosomes quantitatively utilizing fluorescent nanospheres as the label. We quantified the expression of CD63 surface protein markers on exosomes from conditioned culture media of breast cancer cells. The exosomes that targeted specific proteins with controls were statistically analyzed and compared to those that targeted non-specific proteins. Results from SEM showed that the exosomes were circular, between 30 and 150 nanometers in size. The porous gold substrates captured more exosomes than the nonporous substrates. Nitric acid treatments at different times resulted in a variety of pore sizes. Despite the increase in the size of the pores, the number of exosomes found in the porous gold substrate treated for 10 min nearly doubled compared to the one treated for 5 min. In this work, a fluorescence biosensor was developed to detect breast cancer exosomes using nanoporous gold substrates (NPG). Assay and model exosomes of specific breast cancer cells showed that exosomes exhibit diagnostic surface protein markers, reflecting the protein profile of their parent cells. Furthermore, the specific binding between the exosome surface antibodies and the targets identified the CD63 biomarkers on the exosome, suggesting these markers' diagnostic potential. This study can accelerate exosome research in determining tumor-related exosomes and develop novel cancer diagnostic methods.
An optimized and validated spectrophotometric method has been developed for the determination of cefixime in pharmaceutical formulations. The method is based on the complexation reaction between cefixime and palladium ion in the presence of acidic buffer solution (pH 3) in ethanol-distilled water medium at room temperature. The complex absorbed maximally at 352 nm. Beer's law is obeyed in the working concentration range of 2.5-35 μg/mL with apparent molar absorptivity of 1.015×104 L/mol cm and Sandell's sensitivity of 0.001 μg/cm2/0.001 absorbance unit. The limits of detection and quantitation for the proposed method are 0.175 and 0.583 μg/mL, respectively. The effect of common excipients used as additives has been studied in the determination of cefixime. The proposed method has been successfully applied for the determination of cefixime in pharmaceutical formulations. The results obtained by the proposed method were statistically compared with the reference method using t and F values and found no significant difference between the two methods.
The quantification of nanomaterials accumulated in various organs is crucial in studying their toxicity and toxicokinetics. However, some types of nanomaterials, including carbon nanomaterials (CNMs), are difficult to quantify in a biological matrix. Therefore, developing improved methodologies for quantification of CNMs in vital organs is instrumental in their continued modification and application.
Thermoresponsive drug delivery systems are designed for the controlled and targeted release of therapeutic payload. These systems exploit hyperthermic temperatures (>39°C), which may be applied by some external means or due to an encountered symptom in inflammatory diseases such as cancer and arthritis. The objective of this paper was to provide some solid evidence in support of the hypothesis that solid lipid nanoparticles (SLNs) can be used for thermoresponsive targeting by undergoing solid-liquid phase transition at their melting point (MP). Thermoresponsive lipid mixtures were prepared by mixing solid and liquid natural fatty acids, and their MP was measured by differential scanning calorimetry (DSC). SLNs (MP 39°C) containing 5-fluorouracil (5-FU) were synthesized by hot melt encapsulation method, and were found to have spherical shape (transmission electron microscopy studies), desirable size (<200 nm), and enhanced physicochemical stability (Fourier transform infrared spectroscopy analysis). We observed a sustained release pattern (22%-34%) at 37°C (5 hours). On the other hand, >90% drug was released at 39°C after 5 hours, suggesting that the SLNs show thermoresponsive drug release, thus confirming our hypothesis. Drug release from SLNs at 39°C was similar to oleic acid and linoleic acid nanoemulsions used in this study, which further confirmed that thermoresponsive drug release is due to solid-liquid phase transition. Next, a differential pulse voltammetry-based electrochemical chemical detection method was developed for quick and real-time analysis of 5-FU release, which also confirmed thermoresponsive drug release behavior of SLNs. Blank SLNs were found to be biocompatible with human gingival fibroblast cells, although 5-FU-loaded SLNs showed some cytotoxicity after 24 hours. 5-FU-loaded SLNs showed thermoresponsive cytotoxicity to breast cancer cells (MDA-MB-231) as cytotoxicity was higher at 39°C (cell viability 72%-78%) compared to 37°C (cell viability >90%) within 1 hour. In conclusion, this study presents SLNs as a safe, simple, and effective platform for thermoresponsive targeting.
The radical cure of Plasmodium vivax and P. ovale requires treatment with primaquine or tafenoquine to clear dormant liver stages. Either drug can induce haemolysis in individuals with glucose-6-phosphate dehydrogenase (G6PD) deficiency, necessitating screening. The reference diagnostic method for G6PD activity is ultraviolet (UV) spectrophotometry; however, a universal G6PD activity threshold above which these drugs can be safely administered is not yet defined. Our study aimed to quantify assay-based variation in G6PD spectrophotometry and to explore the diagnostic implications of applying a universal threshold.
The use of sulfate reducing bacteria (SRBs) in laboratory studies is a common approach for investigating microbially influenced corrosion (MIC). The characteristic formation of black iron sulfide precipitates during SRB growth, however, preclude the use of traditional spectrophotometric approaches for capturing growth data instead necessitating labour-intensive or technically specialized approaches. As such, an understanding of SRB growth responses to experimental conditions is often missing from MIC studies. Bernardez and de Andrade Lima (2015) have outlined a spectrophotometric approach for estimating SRB cell mass via the addition of HCl. This method has potential for the study SRB growth however its applicability is currently limited by the use of large aliquot volumes (45 mL), which restrict the number of timepoints that can sampled from one culture, and the extensive time devoted to cell preparation prior to OD readings. •We demonstrate an improved method for capturing SRB growth data via spectrophotometry following acidification. We incorporate lower sample volumes and adapt the method described in Bernardez and de Andrade Lima (2015) to a high throughput microtiter plate approach that increases the efficiency of this method and its applicability to growth rate studies.•Our results allay theoretical concerns that acidification may distort growth rate analysis by impacting cells differently depending on their metabolic state.•We further demonstrate that this method (acid-amended OD measurements) is more accurate and far more cost efficient than traditional methods (dilution spread-plate counting) and popular molecular methods (quantitative PCR) currently in use in SRB growth research.
Proximal femur fractures represent a major healthcare problem in the aging society. High rates of post-operative infections are linked to risk factors that seem to affect local microcirculation. Patterns and time courses of alterations in microcirculation have, however, not been previously investigated. The aim of this prospective cohort study was to evaluate perioperative changes in microcirculation after trochanteric femur fractures using non-invasive laser-Doppler spectrophotometry to analyze how oxygen saturation (SO2), hemoglobin content (Hb) and blood flow changed before and after surgery, and how these parameters were altered by implant type, gender, smoking, diabetes and age. Measurements were separately recorded for nine locations around the greater trochanter in 2, 8, and 15 mm depths, before surgery and 8, 24, 48 h, 4, 7, and 12 days after surgery in 48 patients. Three implants were compared: Dynamic Hip Screw, Gamma3 Nail, and Percutaneous Compression Plate. Surgery resulted in significant differences between the healthy and injured leg in SO2, Hb and flow. Each parameter showed comparable values for both legs prior to surgery. Significantly higher values in SO2 and flow were registered in women compared to men before and after surgery. Smoking caused significant increases in SO2, Hb, and flow only in the superficial layer of the skin after surgery. Diabetes decreased blood flow at 2 and 8 mm depth and increased SO2 at 8 and 15 mm depth after surgery. Age revealed a significant negative correlation with flow. The ability to increase the flow rate after surgery decreased with age. Comparison of implants indicated the minimally invasive implant PCCP altered microcirculation less than the DHS or the Gamma3 nail. Overall, the proximal femur fracture alone did not alter local skin microcirculation significantly in a way comparable to the effect caused by surgery. In conclusion, microcirculation after proximal femur fractures is highly affected by surgery, gender, smoking, diabetes, age and implant in ways specified in this study.
The determination of protease activity is very important for disease diagnosis, drug development, and quality and safety assurance for dairy products. Therefore, the development of low-cost and sensitive methods for assessing protease activity is crucial. We report two approaches for monitoring protease activity: in a volume and at surface, via colorimetric and acoustic wave-based biosensors operated in the thickness-shear mode (TSM), respectively. The TSM sensor was based on a β-casein substrate immobilized on a piezoelectric quartz crystal transducer. After an enzymatic reaction with trypsin, it cleaved the surface-bound β-casein, which increased the resonant frequency of the crystal. The limit of detection (LOD) was 0.48 ± 0.08 nM. A label-free colorimetric assay for trypsin detection has also been performed using β-casein and 6-mercaptohexanol (MCH) functionalized gold nanoparticles (AuNPs/MCH-β-casein). Due to the trypsin cleavage of β-casein, the gold nanoparticles lost shelter, and MCH increased the attractive force between the modified AuNPs. Consequently, AuNPs aggregated, and the red shift of the absorption spectra was observed. Spectrophotometric assay enabled an LOD of 0.42 ± 0.03 nM. The Michaelis-Menten constant, KM, for reverse enzyme reaction has also been estimated by both methods. This value for the colorimetric assay (0.56 ± 0.10 nM) is lower in comparison with those for the TSM sensor (0.92 ± 0.44 nM). This is likely due to the better access of the trypsin to the β-casein substrate at the surface of AuNPs in comparison with those at the TSM transducer.
Chemometric can be defined as a branch of analytical chemistry using statistical principles to design and select optimal analytical procedures and experiments. The chemometric technique that applies in the design of quantitative calibration curves in the spectral analysis is very important in quality control of the component contained in the drug mixture of 2 or 3 drug components or more, especially the component that has the adjacent wavelength when the spectrum overlap.
The study aimed to gain first data on the prevalence of G6PD enzyme deficiency measured by spectrophotometry and associated genetic variants in Jimma and surroundings, Ethiopia. The area is a Plasmodium vivax endemic region, but 8-aminoquinolines such as primaquine are not recommended as G6PD testing is not available.
Simple, fast, and precise reversed-phase (RP)-high-performance liquid chromatography (HPLC) and two ecofriendly spectrophotometric methods were established and validated for the simultaneous determination of moxifloxacin HCl (MOX) and flavoxate HCl (FLX) in formulations. Chromatographic methods involve the separation of two analytes using an Agilent Zorbax SB C18 HPLC column (150 mm × 4.6 mm; 5 µm) and a mobile phase consisting of phosphate buffer (50 mM; pH 5): methanol: acetonitrile in a proportion of 50:20:30 v/v, respectively. Valsartan was used as an internal standard. Analytes were monitored by measuring the absorbance of elute at 299 nm for MOX and 250 nm for FLX and valsartan. Two environmentally friendly spectrophotometric (first derivative and ratio first derivative) methods were also developed using water as a solvent. For the derivative spectrophotometric determination of MOX and FLX, a zero-crossing technique was adopted. The wavelengths selected for MOX and FLX were -304.0 nm and -331.8 nm for the first derivative spectrophotometric method and 358.4 nm and -334.1 nm for the ratio first-derivative spectrophotometric method, respectively. All methods were successfully validated, as per the International Conference on Harmonization(ICH) guidelines, and all parameters were well within acceptable ranges. The proposed analytical methods were successfully utilized for the simultaneous estimation of MOX and FLX in formulations.
We present a protocol for measuring the pH of cell-free bacterial-conditioned media based on changes in the ultraviolet-visible (UV-Vis) absorbance spectrum using the pH indicator dye litmus. This protocol includes detailed procedures for performing bacterial culturing, examining bacterial growth, collecting cell-free supernatant, litmus dye addition, and pH-based calibration curve preparations. This assay has been designed for flexible formatting that can accommodate both high-volume and low-volume sample sets.
Several microwave-assisted digestion methods were tested at the Centro de Estudios Aplicados en Química laboratory in Quito, Ecuador, to determine the accuracy and performance efficiency of the mineralization process for the determination of total mercury in fish tissue by cold vapor atomic fluorescence spectrophotometry. The use of MARSEasyPrep high-pressure vessels, low amounts of reagents (1 cm3 HNO3, 1 cm3 H2O2, and 1 cm3 HClO4), an irradiation temperature of 210 °C, and 35 min of mineralization time resulted in accurate performance, with recoveries of certified reference material DORM-4 between 90.1% and 105.8%. This is better than the Association of Official Analytical Chemists 2015.01 method, which has a reported accuracy of 81%. The repeatability precision and intermediate precision were established at three concentration levels (0.167, 0.500, and 0.833 mg·kg-1) and expressed as the percentage of the relative standard deviation ranging from 1.5% to 3.0% and 1.7% to 4.2%, respectively. Further, the method was satisfactorily applied to analyze fortified samples of tilapia (Oreochromis niloticus), with recoveries ranging from 98.3% to 104.3%. The instrumental limits of detection and quantification were 0.118 µg·dm-3 and 0.394 µg·dm-3, respectively.
Benzophenone-4 (BZ4) was separated from surfactants, dyes, preservatives, and other components of hair shampoos by thin-layer chromatography on silica gel 60 stationary phase, with ethyl acetate-ethanol-water-pH 6 phosphate buffer (15 : 7 : 5 : 1 v/v/v/v) as mobile phase. Densitometry scanning of chromatograms was performed at 285 nm. The densitometric calibration curve for BZ4 was nonlinear (second-degree polynomial), with R > 0.999. The limits of detection and quantification were ca. 0.03 and ca. 0.1 μg spot(-1), respectively. The results obtained by HPTLC-densitometry were compared to those obtained by zero and 2nd derivative UV spectrophotometry. In the case of spectrophotometric methods, calibration curves were linear with R > 0.9998. The chromatographic method was fully validated.
The effects of gradual vascular occlusion on the blood supply of perfused areas are poorly described. Information relating to the comparison of flap monitoring techniques is lacking. Varying stenotic conditions (0%, 25%, 50%, 75% and 100%) were generated on purpose at the A. and V. femoralis in the rat model. Analyses included flowmeter, simultaneous laser-Doppler flowmetry and tissue spectrophotometry (O2C) and indocyanine green- (ICG-) videoangiography with integrated FLOW 800 tool. A Random Forests prediction model was used to analyse the importance of each method to diagnose the stenotic conditions. The ability to discriminate and to accurately estimate the probability of stenosis was assessed by Receiver Operating Characteristic (ROC) curves and calibration plots. Blood flow changes for all modalities were described in detail. Flowmeter displayed earliest a linear decrease as a result of increasing stenosis. A stenosis of 50% degrees was most difficult to detect correctly. The combination of flowmeter and ICG-videoangiography showed high diagnostic power for each stenotic situation (area under the ROC > 0.79). Flowmeter and ICG-videoangiography showed to be most relevant in detection of varying stenotic conditions and may change the clinical outcome. The O2C showed less effect on varying stenotic situations as the only surface monitoring device.
A new cloud point methodology was successfully used for the extraction of carcinogenic pesticides in milk samples as a prior step to their determination by spectrophotometry. In this work, non-ionic silicone surfactant, also known as 3-(3-hydroxypropyl-heptatrimethylxyloxane), was chosen as a green extraction solvent because of its structure and properties. The effect of different parameters, such as the type of surfactant, concentration and volume of surfactant, pH, salt, temperature, incubation time and water content on the cloud point extraction of carcinogenic pesticides such as atrazine and propazine, was studied in detail and a set of optimum conditions was established. A good correlation coefficient (R2 ) in the range of 0.991-0.997 for all calibration curves was obtained. The limit of detection was 1.06 µg l-1 (atrazine) and 1.22 µg l-1 (propazine), and the limit of quantitation was 3.54 µg l-1 (atrazine) and 4.07 µg l-1 (propazine). Satisfactory recoveries in the range of 81-108% were determined in milk samples at 5 and 1000 µg l-1, respectively, with low relative standard deviation, n = 3 of 0.301-7.45% in milk matrices. The proposed method is very convenient, rapid, cost-effective and environmentally friendly for food analysis.
Gabapentin is an anticonvulsant widely used in the treatment of epilepsy. No peculiar chromophore is available on the gabapentin moiety for direct analysis by absorption spectrophotometry. A sensitive spectrophotometric method for the determination of gabapentin in bulk, pharmaceutical formulations and human plasma has been developed. In this method, gabapentin directly derivatized with vanillin and analyzed without any extraction in bulk and pharmaceutical dosage form and in plasma samples, it was extracted with a reversed-phase solid-phase extraction (SPE) cartridge followed by derivatization with vanillin. Analysis was performed by a spectrophotometer system. The quantitation limit of gabapentin in human plasma was 0.8 mg/L. The method was linear over the concentration range of 10.0-90.0 mg/L and 0.8-10.0 mg/L for pharmaceutical dosage form and plasma, respectively. The method was precise (relative standard deviation, RSD <1.20%) and accurate (relative mean error <5.5%) for both pharmaceutical dosage form and plasma samples. Mean absolute recoveries were 94.5% for plasma.
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