Metrohm Dosing Test. Calibration of Metrohm dosing and exchange units

Transcription

1 Metrohm Dosing Test Calibration of Metrohm dosing and exchange units

2 Used every day and always accurate Everyday use Your Metrohm dosing or exchange unit operates reliably day in, day out, or even overnight if so configured. It al ways dispenses an exact volume. The cylinder is filled with titrant before the sequence starts again. The Metrohm Dosing Test The Metrohm Dosing Test has been developed to deal with this situation: your dosing or exchange unit is periodically inspected to verify that its accuracy and precision are still within the required tolerances. You base your decisions on the results obtained because you know that you can rely on the values delivered by your Metrohm titration system. Furthermore, the Metrohm Dosing Test is carried out by specially trained Metrohm Service Engineers at your workplace using recognized standards and procedures. But are these values absolutely reliable? Yes they are, provided that your Metrohm dosing or ex change unit is new, or has been regularly serviced. Like any instrument exposed to chemicals or which has moving parts, or both in the case of a Metrohm buret, it may become less accurate over time. The Metrohm Dosing Test can be conducted during an nual servicing of the instrument, either as a component of a Metrohm Care Contract or «on demand» to mi nimize disruption to your laboratory workflow. Alcoholic KOH, for example, attacks the glass cylinder and can thus alter its inside diameter. Intensive use of the internal buret or just simply aging may also compromise the performance of the measuring system.

3 ... for very demanding requirements Piston burets have very demanding requirements with respect to accuracy and precision of the dosed volumes, as defined in ISO standard :2002 «Piston-operated volumetric apparatus Part 3: Piston burettes» and in U.S. Pharmacopeia USP 35-NF 30, General Chapter <31> «Volumetric Apparatus». When they leave factory, Metrohm burets fulfill these strin gent requirements without exception, as confirmed by the corresponding quality certificate. This means you can rely on the accuracy and precision of your piston buret right from the start. The Metrohm Dosing Test checks that these requirements are still being fulfilled in your daily operations and confirms continuous compliance with the respective standards. 03 Maximum permissible errors for motor-driven piston burets according to ISO :2002: Tolerances for burets according to N.I.S.T. Class A (ASTM E287-02): Nominal Maximum permissible errors volume systematic random ml ± µl ± µl Designated 10 volume («micro» ml type) Subdivisions, ml Limit of error, ml

4 One test method for every requirement The Metrohm Dosing Test is based on a gravimetric The accuracy of the results depends not only on exact 04 method. This means that the dispensed water is weighed determination of the mass, but on other parameters as and the volume dosed is then calculated using the specific density of water. The calculated dosed volume is and the ambient air as well as the barometric pressure. well. These are primarily the temperature of the water sub sequently compared to the displayed volume. This is why the Metrohm Service Engineers are equipped with calibrated thermometers and barometers. Procedure according to ISO In the procedure specified in the standard «ISO :2002 Piston operated volumetric apparatus Part 6: Gravimetric methods for the determination of measurement error», three different volumes are used in the test: 10% of the nominal cylinder volume 50% of the nominal cylinder volume 100% of the nominal cylinder volume Ten individual measurements are carried out for each of these three volumes. The test liquid is water conforming with grade 3 as specified in ISO The systematic and the random measurement errors are calculated from the measured values. Metrohm Dosing Test, cumulative procedure The general conditions of the Metrohm Dosing Test correspond to those of standard ISO :2002. Details of the test conditions, the test procedure, and the calculations are given in Metrohm Application Bulletin 283/1 e. In the cumulative procedure, the test volumes are dispensed from one cylinder filling without any refilling. The smallest test volume is exactly 10% of the cylinder volume, the largest is exactly 100%. The remaining 8 test volumes are randomly selected from the range between these two limits. This procedure ensures that the entire volume range of the buret is covered. The linearity of the dosed volume can thus be reliably checked.

5 Metrohm Dosing Test, repetitive procedure In the repetitive procedure of the Metrohm Dosing Test, one test volume is dispensed and then the cylinder is refilled. Each dosing thus starts with a cylinder that is completely full. 05 Customer-specific Dosing Test The Customer specific Dosing Test is carried out in accordance with the procedure and general conditions specified in standard ISO :2002. However, customers can select the following parameters: The selected test volume can be any value between 10% and 100% of the nominal cylinder volume. The number of repeated measurements can vary between 3 and 10, and this number can be varied for the individual test volumes. This enables compliance with customer specific requirements, e.g. those specified in an SOP. Choosing the appropriate test procedure Procedure according to ISO Metrohm Dosing Test, cumulative procedure Metrohm Dosing Test, repetitive procedure Customer specific Dosing Test Your advantages Official procedure according to an internationally recognized standard Based on ISO :2002 Checks the entire volume range Quickest procedure Based on ISO :2002 Checks the entire volume range Simulates practical conditions Complies with the requirements of your SOP The buret can be checked in the volume range you need

6 Stay on the safe side 06 The Dosing Test gives you certainty the certainty that your Metrohm buret is dispensing the displayed value. This in turn gives you assurance that you really can rely on your results, and that this will not cause problems during auditing. Once the Metrohm Dosing Test has been successfully completed, you will receive the corresponding certificate. This certificate confirms clearly and traceable that your buret continues to comply with the requirements as verified by the test, as well as the reference instruments used in the test. In short, you can focus on your work knowing that you can rely 100 percent on the accuracy of your Metrohm buret.

7 Good to know The test includes inspection and maintenance of your Metrohm buret Every Metrohm Dosing Test includes inspection and maintenance of your Metrohm buret. Titrando. The piston stroke of 50 mm or 80 mm is di vi ded into 10,000, respectively, 20,000 increments. 07 The Metrohm Service Engineer checks the piston, cylinder, valve disc, connecting tubes, and other components for any signs of damage or wear, and then cleans and lubricates the parts as necessary. If the buret no longer complies with the requirements, the Metrohm Service Engineer can replace the correspon ding components directly on-site and then repeats the Dosing Test. Inspection and maintenance of your drive unit (Dosino, Titrino, Titrando) The exchange unit or the dosing unit and the buret drive form a unit, and the complete system is checked during the Dosing Test. The drive unit itself is also a high-precision instrument, re gardless whether it is a Dosino, a Titrino or even a Needless to say, this stroke is directly related to the dosed volume. If the drive unit deviates from the spe cifi cations, it directly compromises the result of the Dosing Test. Inspection and maintenance of your drive is thus worthwhile for several reasons: No unpleasant surprises during the Dosing Test. Error-free function of the drive unit, not only during the Dosing Test itself, but also during operation. Maximum flexibility in combining the drive unit with an exchange unit resp. a dosing unit. Provided that all of your exchange, dosing, and drive units have been calibrated, any ex change or dosing unit can be combined with any drive unit. Legend: Subsidiary Independent Distributor

8 Subject to change Layout Ecknauer+Schoch ASW, printed in Switzerland by Metrohm AG, CH-9100 Herisau EN