Calibration curve

About: Calibration curve is a research topic. Over the lifetime, 6552 publications have been published within this topic receiving 95128 citations.

Determination of Nitrate in Water Containing Dissolved Organic Carbon by Ultraviolet Spectroscopy

Abstract: Direct measurement of ultraviolet (UV) light absorption by nitrate in the 200–205 nm wavelength band offers a reliable, accurate and rapid method of nitrate determination in natural waters. However, UV light is also strongly absorbed by organic matter at these wavelengths. A two-wavelength approach was adopted and evaluated for the correction of absorbance that organic matter might have contributed. The measurements were made at 205 nm and 300 nm. The relationship between absorbance at 205 nm and 300 nm due to organic matter was incorporated into traditional nitrate calibration curve to make allowance for the organic matter contribution. The method developed has a detection limit of 0.04 mg NO3-N dm−3 and is capable of determining nitrate concentration in the range of 0.08 – 4.0 mg NO3-N dm−3. In terms of accuracy and reproducibility, the method compares well with the hydrazine-reduction method, with matching precision (1.14% over the concentration range) and accuracy (± 2%). This two-wavelength ...

Gel permeation chromatography coupled to fourier transform mass spectrometry for polymer characterization.

Abstract: We report an on-line coupling of gel permeation chromatography (GPC) to Fourier transform mass spectrometry (FTMS) using a modified commercial electrospray ionization (ESI) interface. Selected oligomer profiles for the sodiated (1+ through 5+ charge states) oligomer ions of a narrow-molecular-weight poly(methyl methacrylate) were generated and used for obtaining a calibration curve. Using the MS-generated calibration curve and the refractive index response for quantification, an accurate molecular weight distribution was calculated and showed an excellent agreement with the value specified by the supplier. GPC/ESI/FTMS also allowed for an unequivocal end-group determination and characterization of a secondary distribution due to the formation of cyclic reaction products. We analyzed a glycidyl methacrylate/butyl methacrylate copolymer with a broad molecular weight distribution, where fractionation and high resolving power were required for adequate characterization. Molecular weight distribution data show...

Rapid Quantitative Determination of Ciprofloxacin in Pharmaceuticals by Use of Solid-State FT-Raman Spectroscopy

Abstract: FT-Raman spectroscopy based on band intensity or band area measurements was used for the quantitative determination of ciprofloxacin in pharmaceutical solid dosage forms. Univariate calibration was used for quantitative analysis. Bands observed at 1708, 1624, 1548, 1493, 1273, 1253, 1238, 1024, 805, 787, 752, 718, 665, and 638 cm-1 were used. Calibration curves were linear in the concentration range of 3-100% w/w with correlation coefficients of 0.99-0.996 and 0.991-0.9993 for band intensity and band area measurements, respectively. Precision ranged from 0-11 and 0.4-12% relative standard deviation (RSD) (n = 3) for band intensity and band area measurements, respectively, and results were in good agreement with the results obtained by the current United States Pharmacopoeia (USP 24) and National Formulary (NF 19) method. Multivariate calibration was also used for quantitative analysis. Multiple linear regression using the intensities of the 1545 and 1272 cm-1 bands gave results in accordance with those obtained by the current United States Pharmacopoeia (USP 24) and National Formulary (NF 19) method. As measurement takes just 30 s using the analytical readout from a single band, the proposed method can be used to replace tedious and time-consuming methods.

Protein assay using microwave energy

Abstract: A modification of the standard BCA protocol is provided that allows sensitive and reliable protein determinations in a matter of seconds utilizing a microwave oven to irradiate the samples. Methods of determining protein concentrations in a sample are disclosed comprising the steps of combining the sample with a BCA assay reagent in a sample container, placing the sample container into a microwave oven, irradiating the sample and measuring an absorbance value at 562 nm for the sample. Protein concentrations are then determined by comparing the absorbance value with a known value based on a calibration curve. In preferred embodiments, the calibration curve is generated by placing one or more standards in the microwave oven and irradiating the standards. Preferably, the step of irradiating the sample is carried out for a duration of less than about 60 seconds and most preferably, for a duration of about 20 seconds. The step of irradiating the sample most preferably comprises exposing the sample to microwave energy at a power level of between about 600 to about 650 watts at a frequency of about 2.45 GHz. In addition to the preferred embodiments using BCA reagents, it has been found that the incubation times other protein assays, such as those based on the reaction with alkaline copper tartrate can also be significantly reduced by exposing the sample and the assay reagents to microwave irradiation. Apparatus for performing such microwave enhanced assays is also disclosed.