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Accessories for CHROMA Colorimeter Model 260

Sample containers

Colorimetric analysis is performed on solutions and as such the sample can only be analysed within a container. The container must therefore be (or made to be) transparent at the wavelength at which the sample is being measured.

Sample containers are offered in a variety of forms depending on whether the important factor is sample size, speed of measurement or accuracy.

For colorimetric work all containers should be made of glass or clear plastic. The types of container are listed below.

Matched Test Tubes

These are made of soda glass. They are individually matched at the Sherwood factory and supplied in matched sets, i.e. each tube in any set has exactly the same absorbance characteristics, this ensures that once a blank has been measured every sample absorbance readout will be due to the sample only no matter which of the tubes in the set is used.

Various diameter tubes are offered so that the sensitivity of measurement can be varied i.e. if a sample is concentrated (high absorbance values) then measurement in a small test tube is suitable as the light has to travel a smaller distance through the sample leading to lower absorbance values. However if dilute samples are to be analysed it is necessary to increase sensitivity by offering more sample to the light hence larger test tubes are used.

Each test tube size has a corresponding holder. The holders can also accommodate a square cuvette of the appropriate size as indicated in the table

Test Tube Part No Set of 12 Diameter Holder Part No
00299011 15 mm 25212001
00299012 10 mm 25211001
00299013 5 mm 25210001
N/A   25211002

Cuvettes

Sherwood Scientific supplies these in several versions:

General purpose Plastic (Polystyrene) 10 x 10 x 45 mm. (47188300)

Supplied with every M260 (not UV) CHROMA colorimeter. Beware of reusing disposable cuvettes which can become scratched and unusable. They should not be used for any measurement involving light scattering such as Sperm counting as the slightest surface imperfection will ruin the precision of the measurement

Semi micro version Plastic 10 x 4 x 10 mm (47188400)

Also made of polystyrene these are used where the volume of sample is restricted for example with biological samples. The pathlength is still 10 mm and can work with sample volumes down to 600µl

Micro Cuvettes (001 26 120)

For use with Heated Cuvette Holder they are UV compatible and have a path length of 10mm but can operate with sample volumes down to 400µl

Glass Cuvettes These are basically fused glass cells with an exact path length (usually 10 mm). Glass Cuvettes generally offer reusability provided they are handled carefully and cleaned well.

The most common colorimetric measurements are made in 10 mm x 10 mm cuvettes. These cuvettes are usually 45 mm high and hold 4 ml of sample solution.

Optical Filters

Gelatine Filters

These are low cost selection devices which produce or transmit a wide band of radiation usually 20 nm. Fortunately most colorimetric analyses have a wide absorption band which allows excellent results to be obtained in conjunction with the CHROMA colorimeters.

We make this type of filter by sandwiching a thin layer of dyed gelatin of the desired colour between two thin glass plates.

Coverage of all wavelengths in the visible spectrum is catered for using a set of 8 Gelatine filters Sherwood part Number is (25226001). However most colorimeters are used for only one type of analysis. This will require the use of only one filter and the expense will be greatly reduced as compared with manufacturers who supply colorimeters with a full set already fitted and charged for!

Interference Filters

These are used to select wavelengths more accurately by providing a narrow bandpass typically of around 10nm. The interference filter also only absorbs approximately 10% of the incident radiation over the whole spectrum thereby allowing light of higher intensity to reach the detector.

Sherwood supplies a range of interference filters and, in principle, any wavelength can be accommodated.

Filter type Peak wavelength nm Bandpass Part number
Set Gelatine filters 430-710 ± 20 nm 25226001
Gelatine 410 ± 20 nm 25231001
Gelatine 430 ± 20 nm 25215001
Gelatine 470 ± 20 nm 25216001
Gelatine 490 ± 20 nm 25217001
Gelatine 520 ± 20 nm 25218001
Gelatine 540 ± 20 nm 25219001
Gelatine 580 ± 20 nm 25220001
Gelatine 600 ± 20 nm 25221001
Gelatine 710 ± 20 nm 25222001
Interference 340 ± 5nm 25227021
Interference 405 ± 5nm 47188900
Interference 430 ± 5nm 47179700
Interference 430 Brewing* ± 1nm 47179800
Interference 510 ± 5nm 47189000
Interference 546 ± 5nm 47189100
Interference 600 ± 5nm 47189150
Interference 660 ± 5nm 47189200
Interference 670 ± 5nm 47189250
Interference 680 ± 5nm 47189300
Interference 725 ± 5nm 47189400

*Sherwood Scientific has worked with a leading Brewery Group in the UK to develop a method using a CHROMA Colorimeter Model 260 for the colour of Beer. The European Brewing Conference approved this method, which requires very precise wavelength control and uses the 430 Brewing filter with its 2 nm bandwith. The Colorimeter Model 260 has the ability to input a "Factor" which relates the absorbance to a particular concentration value. In the case of the EBC method, the factor is 25. So the "colour" of beer is the absorbance at 430 x 25.