Detectors refraction index

Model RR/066 351 and 352 pumps models 750/16 variable-wavelength UV monitor detector 750/11 variable filter UV detector, MPD 880S multiwave plasma detector, 750/14 mass detector 750/350/06 electrochemical detector refractive index detector HPLC columns column heaters, autosamplers, pre-columns derivatization systems, solvent degassers, preparative HPLC systems... 

A common cause of baseline drift is a slow elution of substances previously adsorbed on the column. A column cleanup procedure may be in order, or it may need to be replaced. This problem may also be caused by temperature effects in the detector. Refractive index detectors are especially vulnerable to this. In addition, a contaminated detector can cause drift. The solution here may be to disassemble and clean the detector. 

Figure 4.22 High temperature size-exclusion liquid chromatography of an engineering plastic, poly (phenyl sulfate). Column, SSC GPS-3506, 50 cm x 8 mm i.d. eluent, 1-chloronaphthalene flow rate, 1.0 ml min-1 column temperature, 210 °C detector, refractive index detector.

However, samples that have no UV absorbance, exist in ionic form, or require structural information have to couple with other types of detectors. Refractive index (RI) detector is almost a universal detector in that it responds to almost any solute (UV-absorbing molecules, sugars,... 

Figure 6. Chromatograms of polydisparse dextran calihra-tion standard and dextran T-1 0 sample. Detector refractive index.

Figure 8. Gel filtration of ethylated (/ -0-4)-(/ -/ )-DHP 16. Solid line Ethylated (/ -0-4)-(/ -/ )-DHP 16 after removal of low molecular weight fractions. The column was calibrated with (/ -0-4)-(/ -/ ) lignin substructure model trimer 6 (molecular weight 642) /3-0-4 lignin model dimer 1 (molecular weight 348) and polystyrenes of molecular weight 9000, 4000 (void), 2200 (indicated by A). Column Sephadex LH-20, 1.1 x 48 cm. Eluent DMF, 13.5-14.4 ml/hr. Detector Refractive index detector RI-2 (Japan Analytical Industry Co., Ltd.).

Fig. 23 HPSEC separation of standard mixtures. GPC (A) and HPSEC (B) separation of standard mixtures. For GPC (A) separation Columns two glass 109 cm X 12.5 mm ID packed with Bio-Beads SX2 Eluent toluene at a flow rate of 1 ml/min. Detector Refractive index Injection volume 100 fi of 50-100 mg solute/ml toluene. Ambient temperature for HPSEC (B) separation. Columns LiChrogel Ps4 + LiChrogel Psl (each 25 cm X 0.7 cm ID) Eluent toluene at a flow rate of 0.5 ml/min. Detection refractive index Injection volume 20 /rl. Sample cone. 1.5 ml/min Temperature ambient Peaks 1, trimer (Empol 1014) 2, dimer (Empol 1010) and 3, monomer (methyl stearate) as the methyl ester. (From Ref. 77.)...

Classical LC detectors (refractive index, fixed wavelength UV absorbance at 254 or 280 nm) have lacked the sensitivity to allow direct analysis of cannabi-noids in biological fluids. However, recent development of variable wavelength absorbance detectors extending into the 195-220nm UV region and of fluorescence detectors for HPLC led the authors to initiate... 

FIGURE 2-17. Contribution of molecular weight to polymer properties, (a) Molecular weight distribution profile of a typical polymer. (b) Quality control of an alkyd resin. It was determined that a good paint resulted only when the ratio of the peak heights was between 0.6 and 0.8. Detector refractive index. 

FIGURE 5-8. Comparison of elution profiles of commercial oils. Column /aBonda-pak Ci8 (10 /t,m), 3.9 mm ID x 30 cm. Mobile phase tetrahydrofuran acetonitrile (20 80). Detector refractive index at 4X (Model R401). (a) Olive oil. (b) Safflower oil. 

Figure 2. Typical response peaks for HPLC separation of saturates and aromatics. Column, 1-ft /i-PorasU soU vent, n-heptane (1 mL/min) sample, 10 fiL of vacuum gas oil in n-heptane detectors, refractive index, and Pye Unicam moving wire.

When one of the constituents, A or B of a copolymer A-B, has an ultraviolet (UV) absorption and the other does not, a UV detector-refractive index (RI) combined detector system can be used for the determination of chemical composition or heterogeneity of the copolymer. A point-to-point composition, with respect to retention volume, is calculated from two chromatograms and a variation of composition is plotted as a function of molecular weight. The response factors of... 

There exist several different detectors suitable for detecting the analytes after the chromatographic separation. Some commercial detectors used in LC are ultraviolet (UV) detectors, fluorescence detektors, electrochemical detectors, refractive index (RI) detectors and mass spectrometry (MS) detectors. The choice of detector depends on the sample and the purpose of the analysis. 

The UV detector, fluorescence detector, electrolytic detector, refractive index detector, and other detection systems must be checked for repeatability of response signal, sensitivity, and stability. 

Analyses were carried out on a 300 x 4.6 mm i.d. column of Lichrosorb NH2 (10 pm particle size). Detector refractive index. Mobile phase 0.02 M ammonium formate in acetonitrile-water 60 40 adjusted to pH 6 with formic acid. Flow rate 2 ml/min. For quantification, pure compounds were used as external standard. 

The next detector often used in liquid chromatography is the refractive index detector. This detector uses the property of the sample molecules to bend or refract light. The disadvantage of these detectors in comparison to UV detectors is that refractive index detectors are less sensitive than the UV detectors. Refractive index depends strongly on the temperature of the sample. This is why the refractive index detector must be well thermally insulated. A scheme of the analysis cell of the refractive index detector is shown in Figure 2.23. 

This technique is often used online in conjunction with size-exclusion chromatography. Since the signal from the light-scattering detector is directly proportional to the molecular mass of the protein times the concentration (mg mL ), by combining this signal with that from a concentration detector (refractive index or absorbance) it is possible to measine the molecular mass of each protein coming off the column. 

Sterols are generally monitored with either a refractive index detector or a UV detector. Refractive index detectors are generally rather insensitive and therefore UV detectors have generally been used where limits of detection are critical. The limits of detection at 254 nm for lanosterol, jS-stigmasterol and cholesterol have been reported to be approximately 600 ng and for ergosterol 40 ng however, at 282 nm the limits of detection for the latter are reduced to 700 pg, putting the range of detection in the same order as that reported for GLC with flame ionisation detection (Colin et al., 1979). 

Separation of dialkyl phthalates, column PLgel 5 pm 50 A 300 X 7.5 nim, eluant tetrahydrofuran, flow rate 1 ml/minute, detector refractive index (RI) (1) dioctyl phthalate (2) di-n-butyl phthalate (3) diethyl phthalate (4) dimethyl phthalate (5) toluene. 

This type of measurements can very elegantly be realized online by coupling several detectors at the end of the SEC column such as a concentration detector (refractive index detector, spectrophotometric detector, etc.) and an absolute detector measuring the molar mass or related property of the separated species such as laser light scattering detector or capillary viscometer detector. These modern sophisticated separation systems allow not only the separation of the analyzed species but also their very detailed analysis and characterization as concerns the MMD or PSD, as well as other structural and compositional characteristics of simple polymers, co-polymers, etc. A schematic representation of a procedure of SEC data treatment from an experimental chromatogram to the final MMD or PSD data is shown in Figure 8. 

Additional detectors available for HPLC analysis include fluorescence detectors, high-sensitivity diode-array detectors, refractive index detectors, and electrochemical detectors. 

FIGURE 28-28 Applications of size-exclusion chromatography, (a) Separation of fatty acids. Column polystyrene based, 7.5 x 600 nm, with exclusion limit of 1 x 10. Mobile phase tetrahydrofuran, Flow rate 1.2 mL/min. Detector refractive index, (b) Analysis of a commercial epoxy resin (n = number of monomeric units in the polymer). Column porous silica 6.2 x 250 mm. Mobile phase tetrahydrofuran. Flow rate 1.3 mL/min. Detector UV absorption. (Courtesy of BTR Separations.)... 

Detector Refractive Index Light Scattering Detector (miniDAWN, Wyatt Technology, Santa Barbara CA) (detector measures scattered fight intensity (690 nm) at three angles (45°, 90°, 135°)... 

Column 300 x 3.2 Superdex (Pharmacia PC 3.2/30) Mobile phase 200 mM NaCl Flow rate 0.1 Detector Refractive Index... 

Mobile phase pH 4.0 acetate buffer Detector Refractive Index... 

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