Converting Refractometer Readings to Read Def Percentage

March 09, 2022 Post a Comment

Measurement Tool

A refractometer is a laboratory or field device for the measurement of an index of refraction (refractometry). The index of refraction is calculated from the observed refraction angle using Snell's constabulary. For mixtures, the alphabetize of refraction then allows to determine the concentration using mixing rules such equally the Gladstone–Dale relation and Lorentz–Lorenz equation.

Refractometry [edit]

Standard refractometers measure out the extent of calorie-free refraction (every bit part of a refractive index) of transparent substances in either a liquid or solid-state; this is so used in order to identify a liquid sample, analyze the sample's purity, and determine the corporeality or concentration of dissolved substances within the sample. As light passes through the liquid from the air information technology will slow down and create a 'bending' illusion, the severity of the 'bend' volition depend on the amount of substance dissolved in the liquid. For example, the amount of sugar in a glass of water.^[one]

Types of refractometers [edit]

There are 4 chief types of refractometers: traditional handheld refractometers, digital handheld refractometers, laboratory or Abbe refractometers (named for the instrument'due south inventor and based on Ernst Abbe'due south original pattern of the 'critical angle') and inline process refractometers.^[2] There is also the Rayleigh Refractometer used (typically) for measuring the refractive indices of gases.

In laboratory medicine, a refractometer is used to measure the full plasma protein in a blood sample and urine specific gravity in a urine sample.

In drug diagnostics, a refractometer is used to measure the specific gravity of human urine.

In gemology, the gemstone refractometer is one of the cardinal pieces of equipment used in a gemological laboratory. Gemstones are transparent minerals and tin can therefore be examined using optical methods. Refractive alphabetize is a material constant, dependent on the chemical composition of a substance. The refractometer is used to help place precious stone materials by measuring their refractive index, one of the principal properties used in determining the type of a gemstone. Due to the dependence of the refractive alphabetize on the wavelength of the light used (i.e. dispersion), the measurement is normally taken at the wavelength of the sodium line D-line (Na_D) of ~589 nm. This is either filtered out from daylight or generated with a monochromatic light-emitting diode (LED). Sure stones such as rubies, sapphires, tourmalines and topaz are optically anisotropic. They demonstrate birefringence based on the polarisation plane of the low-cal. The 2 different refractive indexes are classified using a polarisation filter. Gemstone refractometers are available both equally classic optical instruments and as electronic measurement devices with a digital display.^[iii]

In marine aquarium keeping, a refractometer is used to measure the salinity and specific gravity of the water.

In the auto industry, a refractometer is used to measure the coolant concentration.

In the car industry, a refractometer is used to measure the amount of coolant concentrate that has been added to the h2o-based coolant for the machining process.

In homebrewing, a brewing refractometer is used to measure the specific gravity earlier fermentation to determine the amount of fermentable sugars which volition potentially be converted to alcohol.

Brix refractometers are oftentimes used by hobbyists for making preserves including jams, marmalades and honey. In beekeeping, a brix refractometer is used to mensurate the amount of water in love.

Bausch & Lomb Abbe Refractometer, ca. 1919-1926
Gemology refractometer ER604 used to test light bending in gemstones; courtesy of A.KRÜSS Optronic GmbH
Hand refractometer
A vino grape grower with refractometer

Automatic refractometers [edit]

Schematic setup of an automatic refractometer: An LED calorie-free source is imaged under a broad range of angles onto a prism surface which is in contact with a sample. Depending on the departure in the refractive index between prism cloth and sample the lite is partly transmitted or totally reflected. The critical angle of total reflection is adamant by measuring the reflected light intensity as a office of the incident angle - Source of paradigm: Anton Paar GmbH, www.anton-paar.com

Automatic refractometers automatically measure the refractive index of a sample. The automatic measurement of the refractive index of the sample is based on the decision of the critical angle of full reflection. A light source, unremarkably a long-life LED, is focused onto a prism surface via a lens system. An interference filter guarantees the specified wavelength. Due to focusing light to a spot at the prism surface, a wide range of dissimilar angles is covered. As shown in the figure "Schematic setup of an automatic refractometer" the measured sample is in direct contact with the measuring prism. Depending on its refractive index, the incoming low-cal beneath the critical bending of total reflection is partly transmitted into the sample, whereas for college angles of incidence the light is totally reflected. This dependence of the reflected light intensity from the incident bending is measured with a high-resolution sensor array. From the video point taken with the CCD sensor the refractive index of the sample can be calculated. This method of detecting the bending of full reflection is contained on the sample properties. It is even possible to measure the refractive index of optically dense strongly absorbing samples or samples containing air bubbling or solid particles . Furthermore, just a few microliters are required and the sample can be recovered. This determination of the refraction bending is independent of vibrations and other environmental disturbances.

Influence of wavelength [edit]

The refractive index of a given sample varies with wavelength for all materials. This dispersion relation is nonlinear and is characteristic for every material. In the visible range, a decrease of the refractive index comes with increasing wavelength. In drinking glass prisms very little absorption is observable. In the infrared wavelength range several absorption maxima and fluctuations in the refractive index appear. To guarantee a high quality measurement with an accuracy of up to 0.00002 in the refractive index the wavelength has to be determined correctly. Therefore, in modernistic refractometers the wavelength is tuned to a bandwidth of +/-0.2 nm to ensure correct results for samples with unlike dispersions.

Modern Automatic Refractometers - Source of image: Anton Paar GmbH, www.anton-paar.com

Influence of temperature [edit]

Temperature has a very important influence on the refractive index measurement. Therefore, the temperature of the prism and the temperature of the sample have to be controlled with high precision. There are several subtly-different designs for controlling the temperature; but in that location are some key factors common to all, such as loftier-precision temperature sensors and Peltier devices to control the temperature of the sample and the prism. The temperature command of these devices should exist designed then that the variation in sample temperature is small plenty that it volition non cause a detectable refractive-alphabetize change.

External water baths were used in the past but are no longer needed.

Extended possibilities of automatic refractometers [edit]

Automatic refractometers are microprocessor-controlled electronic devices. This means they can have a loftier degree of automation and likewise be combined with other measuring devices

Period cells [edit]

In that location are different types of sample cells available, ranging from a menstruum jail cell for a few microliters to sample cells with a filling funnel for fast sample exchange without cleaning the measuring prism in betwixt. The sample cells can besides be used for the measurement of poisonous and toxic samples with minimum exposure to the sample. Micro cells require simply a few microliters book, assure practiced recovery of expensive samples and prevent evaporation of volatile samples or solvents. They tin can too exist used in automated systems for automatic filling of the sample onto the refractometer prism. For user-friendly filling of the sample through a funnel, catamenia cells with a filling funnel are bachelor. These are used for fast sample commutation in quality control applications.

Automatic sample feeding [edit]

Automated refractometer with sample changer for automatic measurement of a big number of samples - Source of image: Anton Paar GmbH, world wide web.anton-paar.com

In one case an automatic refractometer is equipped with a flow jail cell, the sample can either exist filled by means of a syringe or by using a peristaltic pump. Modern refractometers have the option of a born peristaltic pump. This is controlled via the instrument's software bill of fare. A peristaltic pump opens the manner to monitor batch processes in the laboratory or perform multiple measurements on ane sample without any user interaction. This eliminates human error and assures a high sample throughput.

If an automated measurement of a large number of samples is required, modernistic automatic refractometers can be combined with an automatic sample changer. The sample changer is controlled past the refractometer and assures fully automated measurements of the samples placed in the vials of the sample changer for measurements.

Multiparameter measurements [edit]

Measuring combination of an automatic refractometer and a density meter as widely used in the flavors and fragrances industry - Source of paradigm: Anton Paar GmbH, www.anton-paar.com

Today's laboratories exercise not only want to measure the refractive alphabetize of samples, but several boosted parameters similar density or viscosity to perform efficient quality control. Due to the microprocessor control and a number of interfaces, automatic refractometers are able to communicate with computers or other measuring devices, e.g. density meters, pH meters or viscosity meters, to shop refractive alphabetize data and density data (and other parameters) into one database.

Software features [edit]

Automatic refractometers do not only measure the refractive index, just offer a lot of additional software features, like

Instrument settings and configuration via software bill of fare
Automatic data recording into a database
User-configurable information output
Consign of measuring data into Microsoft Excel information sheets
Statistical functions
Predefined methods for different kinds of applications
Automated checks and adjustments
Bank check if sufficient amount of sample is on the prism
Data recording only if the results are plausible

Pharma documentation and validation [edit]

Refractometers are often used in pharmaceutical applications for quality control of raw intermediate and final products. The manufacturers of pharmaceuticals accept to follow several international regulations like FDA 21 CFR Office 11, GMP, Gamp 5, USP<1058>, which require a lot of documentation work. The manufacturers of automatic refractometers support these users providing musical instrument software fulfills the requirements of 21 CFR Part 11, with user levels, electronic signature and audit trail. Furthermore, Pharma Validation and Qualification Packages are available containing

Qualification Plan (QP)
Blueprint Qualification (DQ)
Adventure Analysis
Installation Qualification (IQ)
Operational Qualification (OQ)
Check Listing 21 CFR Part xi / SOP
Performance Qualification (PQ)

Scales typically used [edit]

Brix
Oechsle scale
Plato scale
Baumé scale

References [edit]

^ "The Measurement Shop's Guide to Refractometers - Measurement Store Great britain". www.measurementshop.co.uk . Retrieved 2018-10-15 .
^ "Brief history of refractometers". world wide web.refractometer.pl . Retrieved 2018-10-15 .
^ production page of A.KRÜSS Optronic GmbH (read March 13, 2013)

External links [edit]

Refractometer – Gemstone Buzz uses, procedure & limitations.
Rayleigh Refractometer: Operational Principles
Refractometers and refractometry explains how refractometers work.

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Source: https://en.wikipedia.org/wiki/Refractometer

Harvey Alifeen