palintest Macro 900 Operation Manual

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palintest Macro 900 Operation Manual Manual pdf 74 page image

Macro 900 Operation Manual V3© 2013 Palintest Ltd. www.palintest.com Page 74 of 147Full two-point calibration should be carried out every few months.15.4.4. Calibration Solution PreparationIn order to 'calibrate' (actually, set the relative sensitivity) of the CPHYLLprobe, a 500μg/L calibration solution of fluorescent dye known as RhodamineWT should be used.Please note: there is no direct correlation between Rhodamine concentrationand the concentration of chlorophyll. Rhodamine is used as a convenient dyefor setting the sensitivity of the sensor. The subsequent display of chlorophyll interms of mg/L is a generalisation based on research and experience. The onlyway to obtain a true value in terms of cells/L is to correlate the values from theProbe to quantitative data that has been obtained by laboratory analysis of grabsamples. See previous 'Limitations of Use' section.The 500μg/L calibration solution should be freshly prepared by serial dilutionfrom 200g/L standard using deionised water. The following Rhodamine WTstandard is recommended:Part number: 70301027Description: Rhodamine WT LiquidSupplier: Keystone Europe Ltd.Contact: http://www.dyes.comBe sure to handle chemicals with care and to read and comply with allhealth and safety advice.15.4.5. Serial DilutionThe recommended Rhodamine solution is supplied as a 20% or 200g/L solution,dilution of the stock solution should be carried out as follows.200g/L stock → 500μg/L is recommended to be done as a two-step dilutionprocedure.Step 1: weigh out 0.5g of 200g/L stock solution in a weigh boat and add this to1L of deionized water in a volumetric flask, use some of the water from the 1Lflask to rinse the weigh boat so no stock Rhodamine remains on the boat. Puta lid on the 1L flask and invert 10 times.This step results in a 1 in 2000 dilution of the stock, at this point the 1L flaskwill contain a 100mg/L solution.Step 2: Transfer 5ml of the 100mg/L solution to a 1L volumetric flask and topup to 1L with deionized water. Put a lid on the 1L flask and invert 10 times.This step results in a 1 in 200 dilution of the solution from step 1. Theconcentration of this solution is 500μg/L. This solution can now be used as Pt-2calibration of the CPHYLL sensor.The dilute solution can be stored in a dark bottle in a refrigerator for up to fivedays. After that time it must be discarded.