Measurements of absorbance and fluorescence emission were carried out on aqueous suspensions of polystyrene (PS) microspheres with a diameter of 2.5 µm using a spectrophotometer with an integrating sphere detector. The apparatus and the principles of measurements were described in our earlier publications. Microspheres with and without green BODIPY(@) dye were measured. Placing the suspension i...

The precision characteristics of the absorbance measurements obtained with a low-cost miniature spectrometer incorporating an array detector were evaluated. Uncertainties in absorbance measurements were due to a combination of non-uniform light intensity and detector response over the wavelength range examined (350-850 nm), in conjunction with the digitization of the intensity indications and t...

UV absorbance spectroscopy is the most common method for detecting nucleic acid structural transitions and obtaining thermodynamic parameters. UV-detected melting has been used to determine stabilities of nucleic acid hairpins, duplexes, triplexes, and higher order structures and to determine thermodynamic effects of unusual or modified bases and mismatched base-pairs. We report that in some ca...

A new, simple, precise, accurate and sensitive UV ‐ Spectrophotometric absorption correction method has been developed for simultaneous determination of Metoprolol Succinate and Olmesartan Medoxomil in combined tablet dosage form. Methanol was used as solvent. Absorbance correction method was based on the property of additivity of absorbances. The two wavelengths on Olmesartan medoxomil curve w...

curves of precipitation are shown in Figure 1. Ampicillin, carbenicillin, amoxycillin, procaine penicillin, cephalothin, salicylic acid, acetylsalicylic acid, and dexamethasone caused no interference. The presence of methicillin in urine may be differentiated from the turbidity attributable to protein by measuring the absorbance at different intervals during the reaction, such as 0.5 and 5.0 mm...

We describe spectrophotometric determination of methemoglobin (Met-Hb) in blood by absorbance differences at two wavelengths (characteristic of the instrument used) in the 500-600 nm region. Blood is diluted 100- to 200-fold with a solution containing KCN and carbon monoxide to convert hemoglobin to carboxyhemoglobin and Met-Hb to cyanomethemoglobin (CN-Met-Hb). Carboxyhemoglobin has the same a...

We characterize the leaf spectra of tree species of an Andean cloud forest in Venezuela, grouped according to position in canopy, subcanopy and understory. We measured leaf reflectance and transmittance spectra in the 400-750 nm range using a high-resolution spectrometer. Both signals were subtracted from unity to calculate the absorbance signal. Nine spectral variables were calculated for each...

The performance of two commercially available high-speed photometers, designed for through-the-plate reading, was evaluated. Linearity of instrumental reading and reproducibility of same-day and 2-day measurements were assessed by least-squares analysis and analysis of variance, respectively. For both instruments, the photometric error was on the order of thousandths of an absorbance unit and w...