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Chromatographs—Liquid
Published in Béla G. Lipták, Analytical Instrumentation, 2018
The refractive index detector measures the difference between the refractive index of the sample compounds and the carrier. With the proper choice of carrier it is sensitive to all sample compounds, but the sensitivity is generally lower than that of the optical absorbance detector. It is also quite sensitive to temperature and carrier composition variations. The dielectric constant detector measures the difference between the dielectric constant of the sample compounds and the carrier. Because for compounds with no dipole moment, refractive index and dielectric constant are related, the advantages and disadvantages of this detector and the refractive index detector are similar. However, if, for example, the sample compounds have a dipole moment and the carrier does not, the dielectric constant detector has higher sensitivity and more uniform response than the refractive index detector.
Liquid Chromatography
Published in James P. Lodge, Methods of Air Sampling and Analysis, 2017
The mainstay of HPLC detection remains with the measurement of optical absorbance in the UV-visible range. Detectors with noise levels down to 1 x 10-5 absorbance units are commercially available. The degree of sophistication ranges from fixed wavelength (254 nm) instruments to filter photometers to programmable, monochromator-equipped variable-wavelength devices to diode array detectors. The latter can measure the entire spectral absorption profile (190–800 nm) simultaneously on a subsecond time scale. Fluorescence and electrochemical (amperometric/coulometric) detectors are among the most sensitive and selective. Conductivity detectors are particularly useful for ionic analysis and are widely used in the subdiscipline of Ion Chromatography (4). Radioactivity detectors are available for the detection of radiolabelled compounds. The refractive index detector approaches the closest to an universal detector; however, good sensitivity with such a detector can only be attained with very precise temperature control.
Analytic Methods fo the Bioactive Compounds in Waste
Published in Quan V. Vuong, Utilisation of Bioactive Compounds from Agricultural and Food Waste, 2017
Use of a refractive index detector in HPLC is advantageous as it is able to respond to most analytes. A parallel beam of visible light radiation is passed through a flow cell consisting of two triangular compartments—one containing the pure mobile phase and the other containing the elutant coming from the column. When only the mobile phase is eluted from the column, the beams of light passing between each compartment are unchanged and pass through a deflection plate to hit the photocell detector on the other side. When an analyte enters the cell, the refractive index between the two compartments changes, resulting in a different output that is received by the detector. However, it has numerous disadvantages as compared to other detectors. When compared to the UV detector, it has a significantly lower detection limit (up to 1000 x). Because this detector measures the difference in light refraction between two liquid cells, it can only be used in separations that utilize isocratic solutions. Systems using an elution gradient will never have the same refractive index. So this detector becomes ineffective under these conditions. Such detectors are also linear over a short concentration range and inapplicable for low concentration analysis (Harris 2003, Meyer 2014).
Degradation of 1,4-dioxane by heterogeneous photocatalysis and a photo-Fenton-like process under fluorescent light
Published in Environmental Technology, 2023
Linkon Bhattacharjee, Chunjie Xia, Ethan Krouse, Haoran Yang, Jia Liu
Thermo Scientific™ TRACE™ 1300 gas chromatography (GC) coupled with a ISQ™ 7000 single quadrupole mass spectrometer (MS) was used to analyse 1,4-dioxane. Versa Automated Headspace auto-sampler (Teledyne Tekmar) was used for sample injection into the GC/MS. Chromatographic separation was achieved using a Thermo Scientific™ Trace™ TR-V1 column (30 m × 0.32 mm × 1.80 µm). The MS was operated in electron ionisation (EI) mode with full scan. Instrument parameters for the autosampler, GC, and MS were listed in the Supporting Information (Tables S2-S4). High performance liquid chromatography (HPLC) with a refractive index detector (Shimadzu Scientific Instrument, Inc. Columbia, MD, USA) was used to detect the intermediates. An Aminex HPX-87 column (5 μm, 30 cm × 4.6 mm, Bio-Rad, CA, USA) was installed, and oven temperature was set at 35 °C. H2SO4 at 0.005 M was used as the mobile phase with a flow rate of 0.6 mL/min. Total organic carbon (TOC) was determined using a Shimadzu TOC-L/TNM-L. The samples were preserved in H2SO4 before analysis.
An innovative plasma pre-treatment process for lignocellulosic bio-ethanol production
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2020
Navnit Kumar Ramamoorthy, Raviprakash Nagarajan, Sambavi Ravi, Renganathan Sahadevan
High-Performance Liquid Chromatography (HPLC) analyses mentioned in the work were performed using an Agilent 1290 Infinity HPLC equipped with a Refractive Index detector (RID). 5 mM sulfuric acid was the mobile phase while 20 µl was the sample injection volume. 60°C and 55°C temperature were maintained in the column oven and the detector, respectively. The column used was Agilent Hi-Plex H 7.7 mm x 300 mm x 8 mm.