Liquid chromatography refractive index detection

Femia, R. E. and Weinberger, R., Determination of reducing and non-reducing carbohydrates in food products by liquid chromatography with post-column catalytic hydrolysis and derivatization comparison with refractive index detection, /. Chromatogr., 402, 127, 1987. 

The sensors in this section can also be utilized to detect chemicals in liquid through the bulk solution refractive index change induced by the presence of target chemicals. Since no recognition molecules are used, this type of chemical sensing may usually have low specificity. However, these sensors may perform excellently in conjunction with other technologies such as capillary electrophoresis, mass spectrometer, and liquid chromatography in chemical detection. 

A light beam is refracted to different extents by different compounds. This mechanism is used for refractive index detection. This detector is not sensitive and the selectivity differences are negligible for homologous compounds, but any solvent with a different refractive index to the analyte can be used as the eluent. This detector is mainly applied to size-exclusion and preparative-scale liquid chromatography. 

As a result of advances in detection technology, newer HPLC detection techniques may be utilized. For example, evaporative light-scattering detection and refractive index detection may be used to quantify impurities with poor or no UV chromophore. Conductivity detection may also be used. In some cases, when no chromophore is present, chemical derivatization may be used to add a chromophore. Increasingly, tandem techniques such as liquid chromatography mass spectrometry (LC-MS) and GC-MS are utilized for impurity characterization. The highly selective nature of LC-MS ensures that few impurities are undetected. 

Endo, Y., Tagiri-Endo, M., Seo, H. S., and Fujimoto, K. (2001). Identification and quantification of molecular species of diacylglyceryl ether by reversed-phase high-performance liquid chromatography with refractive index detection and mass spectrometry. J. Chro-matogr. A 911, 39-45. 

Golander Y Schurrath U, Luch JR. Determination of pharmaceutical compounds in animal feeds using high-performance liquid-chromatography with refractive-index detection. Journal of Pharmaceutical Sciences 77, 902-905, 1988. 

Kenmore CK, Erskine SR, Bornhop DJ. Refractive-index detection by interferometric backscat-ter in packed-capillary high-performance liquid chromatography. Journal of Chromatography A 762, 219-225, 1997. 

Our ThFFF channel is similar to the model TlOO Thermal Fractionator (FFFractionation, Inc., Salt Lake City, UT), with a channel thickness of 0.10 mm. When the carrier liquid was tetrahydrofuran (THF) or cyclohexane, a UV monitor set at 254 nm was used for sample detection when toluene was the carrier liquid, a refractive index monitor was used instead. The temperature difference was 60.0 K and the cold wall temperature was 298.2 K. Intrinsic viscosities were measured with a CannonFenske ASTM-25 viscometer obtained from Fisher Scientific (Santa Clara, CA). Viscosities were measured in a thermostated temperature bath set at T g. All solvents were high-performance liquid chromatography grade. 

The refractive index detection (RID), often used in high-performance liquid chromatography, is an interesting detection method in CE with a laser light source and a limit of detection (LOD) in the micromolar range. Electrochemical detection (ECD) and pulsed amperometric detection (PAD) of sugars are common and effective methods used in HPLC. Some recent communications show that the sensitivity of these detection methods in CE have an approximately 1000-fold better LOD than RID. Unfortunately, these de-... 

Ethanol This is determined by oxidation with K2Cr207, followed by titration with Fe (NH4)2(S04)2 6H20-Mohr salt [13] and using a Waters high performance liquid chromatography (HPLC), an ion exchange Shodex column, at 80°C, refraction index detection, at 34°C, elution with Milli-Q water, flow rate of 1.0 ml/min. All samples were analyzed using the titration method. HPLC was used to confirm the results obtained with the titration method. The two methods led to very similar results. 

Figure 7 Refractive index detection in liquid chromatography. (A) Dual-triangular section flow cell for detector based on Snell s law. (B) Separation of detection of carbohydrates with LC and refractive index detection. Sample 4ng each of (1) xylose, (2) fructose, (3) sucrose, (4) maltose hydrate, and (5) lactose. (Reproduced with permission from Munk M (1993) Refractive index detection. In Parriott D (ed.) A Practical Guide to HPLC Detection. San Diego Academic Press.)...

Renn, C. N. and Synovec, R. E., Refractive index gradient detection of biopolymers separated by high-temperature liquid chromatography, /. Chromatogr., 536, 289, 1991. 

Molecular weights were measured by gel permeation chromatography on a Perkin-Elmer Series 10 Liquid Chromatograph using tetrahydro-furan as solvent and refractive index as the detection mode. Standards were polystyrene, and reported molecular weights for the poly-siloxanes do not include a correction. 

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