Refractometers

Note that in liquid phase chromatography there are no detectors that are both sensitive and universal, that is, which respond linearly to solute concentration regardless of its chemical nature. In fact, the refractometer detects all solutes but it is not very sensitive its response depends evidently on the difference in refractive indices between solvent and solute whereas absorption and UV fluorescence methods respond only to aromatics, an advantage in numerous applications. Unfortunately, their coefficient of response (in ultraviolet, absorptivity is the term used) is highly variable among individual components. 

For circulating water through a refractometer any commercial water circulating pump may be used.J... 

Refractive index. The refractive index of a liquid is conveniently determined with an Abbe refractometer. This refractometer possesses the following advantages ... 

Fig. XI, 2, 5 is a drawing of the Hilger "Abbe refractometer, whilst Fig. XI, 2, 6 is a fine diagram showing the essential parts of the instrument.

The author is indebted to Messrs. Adam Hilger Ltd. for these two figures. A detailed description of the instrument will be found in their booklet, Instructions for the Use of the Abbe Refractometer," and to which the reader is referred for further particulars. 

D774 D1894-78 weighed samples D3420-80 D542 Abbe refractometer, 30°C... 

Refractive Index. The refractometric value of sugar solutions is used as a rapid method for the approximate determination of the soHds content (also known as dry substance), because it is assumed that the nonsugars present have a similar influence on the refractive index as sucrose. Measurement is usually carried out on a Brix refractometer, which is graduated in percentage of sucrose on a wt/wt basis (g sucrose/100 g solution) according to ICUMSA tables of refractive index at 20.0°C and 589 nm. Tables are available that give mass fraction corrections to refractometric values at temperatures different from 20°C. 

Polarimetric analysis of sorbitol and mannitol in the presence of each other and of sugars is possible because of their enhanced optical rotation when molybdate complexes are formed and the higher rotation of the mannitol molybdate complex under conditions of low acidity (194). The concentration of a pure solution of sorbitol may be determined by means of the refractometer (195). Mass spectra of trimethylsilyl ethers of sugar alcohols provide unambiguous identification of tetritols, pentitols, and hexitols and permit determination of molecular weight (196). 

The proof content is determined by the use of a standardized hydrometer with a standardized thermometer. The alcohol content can also be determined by the use of an immersion refractometer, a pycnometer, or a density meter. 

When heated with pyrocatechol [720-80-9] copper powder, and alcohoHc sodium hydroxide, carbon tetrachloride gives a blue color that changes to red on addition of hydrochloric acid. This color reaction is not produced by chloroform. Quantitative analysis of carbon tetrachloride may be done by first decomposing the sample free of organic and inorganic chlorides, heating in a sealed tube with alcohoHc potash, and subsequently determining the potassium chloride formed as the silver haHde. The Zeiss interference refractometer has been used to determine the concentration of carbon tetrachloride vapor in air (36). 

Water Content and Refractive Index. The water content of a hydrophilic contact lens is a determinant of other properties. The relationship of water content and Dk is discussed above. Water content in lenses is inversely related to refractive index (23), a key property for vision correction. A lens material with a higher refractive index refracts light to a greater degree, allowing more vision correction with a thinner material. The water content of a lens is generally determined gravimetricaHy or inferred from the relationship to refractive index, measured with a refractometer (24). 

The reseai ch has been carried out by the liquid chromatograph Perkin-Elmer (Series 200), which has tandem detectors the diode array (X=210 nm) and the refractometer. The temperature of a column was 30 C, speed of a mobile phase is 1.5 ml/ min. As a mobile phase, mixtures of solvents methanol - water and acetonitrile - water with addition of sodium perchlorate. The columns with the modified silica gel C8 and Cl8 (4.6x220 mm, 5 pm) were used for sepai ation of the AIST and FAS components. In order to make the identification of AIST and FAS components more reliable the ratio of the values of the above-mentioned detectors signals of each substance analyzed. 

The latest trend is to smaller beads in smaller columns, as this saves eluent and shortens the time for a chromatographic analysis. This argument can be correct if only one suitable detector is used. However, these modern small columns are not optimal for a combination of detectors. So-called multiple detection is a combination of some detectors with different measurement principles (differential refractometer, spectral photometer, light-scattering detector, on-line viscometer) behind the last column, mostly in series, seldom in a branched ( parallel ) order. In this way, the tedious preparative fractionation of a polymer sample can often be avoided. 

X 0.75 cm) Ve i = 28 ml = 50 ml eluent 0.05 M NaCI flow rate 0.80 ml/min detection Optilab 903 interferometric differential refractometer applied sample mass/volume 200 /tl of 2-mg/ml aqueous solutions sum of individual chromatograms (theory —) and (theory/experimental) ratio (—) plotted for quantification of deviations in separation performance between narrow distributed samples and broad distributed samples. 

SEC measurements were made using a Waters Alliance 2690 separation module with a 410 differential refractometer. Typical chromatographic conditions were 30°C, a 0.5-ml/min flow rate, and a detector sensitivity at 4 with a sample injection volume of 80 fil, respectively, for a sample concentration of 0.075%. All or a combination of PEO standards at 0.05% concentration each were used to generate a linear first-order polynomial fit for each run throughout this work. Polymer Laboratories Caliber GPC/SEC software version 6.0 was used for all SEC collection, analysis, and molecular weight distribution overlays. 

A detector is used to determine when to initiate collection of the eluent by a fraction collector. A differential refractometer can be used if the polymer... 

The author and several other chemists have for some years past persistently advocated the use of the refractometer in the examination of essential oils. Although this determination was regarded as of little use by many chemists, it is now generally recognised that it is indispensable. But its value is only to be properly estimated by a very careful consideration of the results obtained. 

Brechungs-ebene, /. (Optica) plane of refraction. -exponent, m. refractive index, -ge-setz, n. law of refraction. -Index, m. refractive index, -k effizient, m. coefficient of refraction. -kraft, /. refractive power, -messer, m. refractometer. -verhaltnis, n. refractive index, -vermfigen, n. refractive power, -winkel, m, angle of refraction, Brech-walzwerk, n. crushing rolls (or rollers), crushing mill. >weln, m. (Pharm.) wine of antimony, antimonial wine, -weiustein, m. tartar emetic, -werk, n. crusher, -wurzel, -wurz,/. ipecacuanha, ipecac. 

Strahlen-brechung, /. refraction, -brechungs-messer, m. refractometer. -bUndel, n., -biischel, m. pencil of rays, beam. 

Figure 1 The gel-chromatogram of the obtained product from the alkylation reaction of toluene with EC under various reaction conditions T, K = 273 (1), 293 (2), 313 (3), 333 (4). The ratio of toluene epichlorohydrin 0.5 1 (5) 1 1 (6), 2 1 (7), and 5 1 (8). (-) refractometer detector (—) UV-detector.

In the laboratory, RI is measured using a refractometer. The instrument has two prisms and a light source. The technician spreads a small amount of sample on the faces of both prisms in the refractometer. The light is then directed at the sample and the scale is read. The observed scale is then converted to a refractive index with tables supplied with the instrument and corrected for the sample temperaturi. ... 

The n-d-M method is very sensitive to both refractive index and density. It calls for measurement or estimation of the feed refractive index at 20°C (68°F). The problem is that the majority of FCC feeds are virtually solid at 20°C and the refractometer is unable to measure... 

Care must be taken to clean and dry the refractometer prisms before and after use in order to prevent etching of the prisms. 

Use of a refractometer to make measurements of the refractive index of liquids. This will often provide a means of identifying a pure compound, and can also be used (in conjunction with a calibration curve) to analyse a mixture of two liquids. 

---