Detection limit

About: Detection limit is a research topic. Over the lifetime, 34379 publications have been published within this topic receiving 644817 citations. The topic is also known as: limit of detection & lower detection limit.

Turn-off fluorescence sensor for the detection of ferric ion in water using green synthesized N-doped carbon dots and its bio-imaging.

Abstract: This paper reports turn-off fluorescence sensor for Fe3 + ion in water using fluorescent N-doped carbon dots as a probe. A simple and efficient hydrothermal carbonization of Prunus avium fruit extract for the synthesis of fluorescent nitrogen-doped carbon dots (N-CDs) is described. This green approach proceeds quickly and provides good quality N-CDs. The mean size of synthesized N-CDs was approximately 7 nm calculated from the high-resolution transmission electron microscopic images. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy revealed the presence of –OH, –NH2, –COOH, and –CO functional groups over the surface of CDs. The N-CDs showed excellent fluorescent properties, and emitted blue fluorescence at 411 nm upon excitation at 310 nm. The calculated quantum yield of the synthesized N-CDs is 13% against quinine sulfate as a reference fluorophore. The synthesized N-CDs were used as a fluorescent probe towards the selective and sensitive detection of biologically important Fe3 + ions in water by fluorescence spectroscopy and for bio-imaging of MDA-MB-231 cells. The limit of detection (LOD) and the Stern–Volmer quenching constant for the synthesized N-CDs were 0.96 μM and 2.0958 × 103 M of Fe3 + ions. The green synthesized N-CDs are efficiently used as a promising candidate for the detection of Fe3 + ions and bio-imaging.

Rapid, sensitive, microscale determination of phosphate in water and soil.

Abstract: ample, is not widely used because it has a relatively high detection limit (0.1 mg L 1 ) and cannot be used for A rapid and sensitive analysis of inorganic and organic phosphorus samples with high concentrations of interfering anions (P) is needed to analyze water and soil extracts at submicromolar concentrations. The proposed method, based on the complexation of without sample pretreatment. The automated ascorbic malachite green with phosphomolybdate under acidic conditions, was acid colorimetric method is extensively used because it adapted to a 96-well microtiter plate format, and was tested for matrix overcomes most of these obstacles. Moreover, many interferences using 15 soils and some common extractants, including automated techniques can save time when they are conwater, KCl, CaCl2, NaOH, and HCl. The accuracy of P determination figured to simultaneously determine several compowas affected when CaCl2 and HCl concentrations were greater than nents in a sample mixture. However, many automated 0.1 M and when NaOH concentration exceeded 0.4 M. Potassium techniques require expensive and dedicated equipment chloride concentration up to 1 M did not interfere with P determina- and a high degree of technical expertise to operate, and tion. The molar absorptivity was 46 841 M 1 cm 1 and the reagent generate large volumes of waste. Considering the short blank absorbance was 0.071 0.003 (n 10). At the 99% confidence holding time for analysis of soluble inorganic P (48 h limit, the method detection limit was calculated to be 0.006 mg P L 1 . Recovery of added inorganic P in different types of soils and extracts for refrigerated samples) and the number of samples ranged between 95 and 112% with an average of 102%. The proposed involved, these constraints put a burden on many labomicroplate method allows P to be determined rapidly in a wide range ratories. of soil types and extracts and requires limited volume (20–200 L). The malachite green (MG) colorimetric procedure The procedure uses limited quantities (40 L) of two stable reagents has also been used to determine P at submicromolar (1 yr), and generates low amounts of hazardous waste. concentrations in water and soil–water extracts (van Veldhoven and Mannaerts, 1987; Ohno and Zibilske, 1991). Both the ascorbic acid (AA; Murphy and Riley,

Capacitance Measurements of Antibody−Antigen Interactions in a Flow System

Abstract: Capacitive immunosensors were made by coupling monoclonal antibodies to thioctic acid, which had self-assembled on a gold electrode. Surface areas that were not covered were plugged with 1-dodecanethiol to make the layer dense and insulating. Cyclic voltammetry showed that the hexacyanoferrate redox reactions were blocked by this procedure. The capacitance of the electrode was evaluated from the current transients obtained when a potentiostatic step was applied. The immunosensor was placed in a flow system, and a capacitance decrease could be observed after injection of an unlabeled antigen. It was linear over almost three decades when plotted vs the logarithm of the antigen concentration. Human chorionic gonadotropin hormone could be determined in the range 1 pg/mL-1 ng/mL, with a detection limit of 0.5 pg/mL (15 10(-15) M). A similar response was obtained with immobilized F(ab)2 fragments. No cross-reactivity was observed with the thyrotropic hormone, which has one chain in common with gonadotropin. Monoclonal antibodies toward interleukin-2 immobilized on the immunosensor gave also a response over 1 pg/mL-1 ng/mL, with a detection limit of 1 pg/mL. An immunosensor with monoclonal antibodies toward human albumin gave a calibration curve with lower slope than the other proteins but still with a detection limit of 1 pg/mL.