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Lateral flow immunoassays combining enrichment and colorimetry-fluorescence quantitative detection of sulfamethazine in milk based on trifunctional magnetic nanobeads
摘要： In this study, magnetic nanobeads (MNBs) were used as a trifunctional material in lateral flow immunoassay for quantitative detection of sulfamethazine (SM2) in milk. Magnetic enrichment aimed to reduce matrix effects. Naked-eye screening of SM2 was based on colorimetry of colored MNBs. The cut-off value of the naked-eye screening was 25 ng mL-1. When the concentration of SM2 in the samples is equal to the cut-off value or higher, the lateral flow strips can be quantitatively detected via grayscale intensity based on colored MNBs. When the concentration of SM2 in the samples is less than the cut-off value, the lateral flow strips can be quantitatively detected by means of fluorescence intensity based on the fluorescence quenching effect of MNBs. Under optimal conditions, the linear range and limit of detection (LOD) of fluorescence lateral flow immunoassay were 0.033-33 ng mL-1 and 0.026 ng mL-1 respectively, while the linear range and LOD of colorimetric lateral flow immunoassay was 1-100 ng mL-1 and 0.71 ng mL-1, respectively. This novel method can be used for rapid and quantitative detection of SM2 in milk.
关键词： lateral flow immunoassay,matrix effects,magnetic nanobeads,colorimetry,fluorescence,sulfamethazine
更新于2025-09-10 09:29:36
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Determination of iodide based on dynamic gas extraction and colorimetric detection by paper modified with silver triangular nanoplates
摘要： This paper reports on a new method for sensitive and selective determination of iodide based on dynamic gas extraction with air flow and digital colorimetric detection using paper modified with silver triangular nanoplates (AgTNPs). Iodide is oxidized in a sample by Fe(III) to produce molecular iodine which is extracted in air flow and transferred to a sensitive AgTNPs-containing paper layer. Interaction of AgTNPs with iodine results in optical changes which can be monitored by ordinary scanner. The high selectivity of dynamic gas extraction to volatile compounds ensures successful analysis of such samples as cranberry and kelp with no sample pretreatment, and due to the sensitivity of AgTNPs good analytical performance can be achieved. The limit of detection of iodide was found to be of 0.01 mg L?1 and the determination range of 0.03–0.3 mg L?1. The method can be easily adapted to simultaneous determination of iodide/iodine and iodide/chloride in the same sample.
关键词： Scanner,Silver triangular nanoplates,Colorimetry,Dynamic gas extraction,Plant and pharmaceutical analysis,Iodide
更新于2025-09-10 09:29:36
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Estimating chlorophyll content from Eucalyptus dunnii leaves by reflectance values
摘要： This study aimed to estimate photosynthetic pigments contents from leaves of Eucalyptus dunni Maiden based on values of reflectance spectra of red, green and blue colors obtained with a digital color analyzer. We collected fifty leaves from the lower third of the crown of twenty trees including young as well as mature leaves. From each leaf an area of 14 cm2 of the leaf blade was cut in which we measured reflectance values on the red, green and blue spectra with a portable digital colorimeter, obtained relative index of chlorophyll with a SPAD – 502 and determined the content of the chlorophyll a, b, and a + b by classic method of solvent extraction. We submitted the data to multiple linear regression and nonlinear analysis at 5% of error probability. It was evaluated the occurrence of multicollinearity. The negative exponential model resulted in good fit when data from red spectrum was used for chlorophyll a, green spectrum for chlorophyll b and a + b, making possible correlation coefficients between the estimated values and the extracted above 0.85. Except for the chlorophyll a content, the accuracy in estimates of photosynthetic pigments were higher than estimated by the chlorophyll meter, even with linearity between methods. Therefore, it is possible to estimate photosynthetic pigments on E. dunni leaves through values of red and green wavelengths from a digital color analyser.
关键词： Colorimetry,Chlorophylls,Spectrum colors
更新于2025-09-09 09:28:46
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Daylight Spectrum Index: A New Metric to Assess the Affinity of Light Sources with Daylighting
摘要： The current scenario of colorimetry shows a wide variety of different metrics which do not converge in the assessment of the color rendering of light sources. The limitations of the Color Rendering Index have promoted the emergence of new metrics, such as the Color Quality Scale. As in the case of the previous metric, these new concepts are based on the analysis of the deviation of different color samples in a color space, contrasting the results with those obtained with a light source reference, which can vary depending on the color temperature. Within this context, the Daylight Spectrum Index is proposed. This new concept aims to determine the affinity with daylighting of electric light sources, comparing the resulting spectral power distributions of the lamps studied and that observed under natural light. The affinity of an electric light source with daylighting allows for lower energy consumption due to the better performance of human vision. The new metric proposed is evaluated following the results obtained from 80 surveys, demonstrating the usefulness of this new concept in the quanti?cation of color rendering of LED lamps and the affinity of electric light sources with daylighting.
关键词： light spectra,light sources,color rendition,colorimetry,energy savings,daylighting
更新于2025-09-04 15:30:14
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Paper-based miniaturized immunosensor for naked eye ALP detection based on digital image colorimetry integrated with smartphone
摘要： Alkaline phosphatase (ALP) is a metalloprotein found naturally in raw milk samples and is considered as an important biomarker in quality control of milk. Its easy, personalized, as well as instrument-less detection is important to ensure the pasteurization and its differentiation form raw milk. In view of such importance of APL, we have developed an office punching machine crafted paper biosensor for naked eye detection of ALP in milk samples. The quantitative estimation is done by digital image colorimetry (DIC) based technique integrated with smartphone. The sensor-probe was developed by the covalent immobilization of ALP antibody (anti-ALP) onto the functionalized paper surface. The fabrication of the biosensing probe was characterized using DIC, Fourier transform infrared spectroscopy (FTIR), and atomic force microscopy (AFM). The detection was based on immunocomplexation between the sensor-probe and ALP, which generates blue-green precipitate as an analytical signal by exploiting the catalytic activity of ALP towards 5-bromo-4-chloro 3-indolyl phosphate (BCIP). The dose dependent appearance of the blue-green complex was captured using smartphone camera and DIC was employed using Red, Green, and Blue (RGB) profiling system, where the maximum sensitivity was obtained for the red color channel. Based on the DIC analysis, a wide dynamic range for the ALP detection is obtained from 10-1000 U/mL with the detection limit of 0.87 (±0.07) U/mL. The designed paper-based biosensor is successfully applied to detect ALP in commercial and raw milk samples. Interferences due to components present in the milk samples was evaluated and the long-term stability of the designed biosensor was examined. Based on the detection principle, a miniaturized kit [20.0 mm (L) x 20.0 mm (W) x 2.15 mm (H)] was developed and applied for the ALP detection to demonstrate the instrument-free direct in-kitchen applicability.
关键词： Miniaturized prototype,Alkaline phosphatase,Paper biosensor,Digital image colorimetry,Bioanalysis
更新于2025-09-04 15:30:14