HACH LANGE QuikChem 8500 2 Serie Wartung Und Fehlerbehebung Seite 17

Do a dye test
Use a dye test is to find a problem with the reagent flow or hardware setup. If nothing is found, the
problem can be chemistry related. Use an interference filter of 500 nm or larger wavelength and a
universal dye. Refer to
There are two important dye tests that can be done. The first test is used to find flow problems. The
second test can help find a valve problem or partial clogs that could not be found with the first test.
The latter test can also be used to find out whether the sample loop is filled correctly.
Make a universal dye
1. In a one liter container, put 7.5 mL (0.25 fl. oz) of each food dye: green, yellow, red and blue.
2. Fill the container with deionized water and shake it several times.
Note: Universal dye is available from the manufacturer (50959).
Identify flow problems with a dye test
This test will find blockages in the reagent tubing or air leaks in the manifold.
1. Put each transmission tube (includes the carrier and the sample probe) in the universal dye one
at a time. Make sure that the dye flows through the tubing. If there is a clog, refer to
blockages on page 18.
2. Look for transmission tubes that pulsate. This might be caused by a partial clog. Make sure that
the liquid from the waste tubing falls in the waste container and that the waste lines are not below
the level of the liquid in the waste container.
Note: The term pulsate refers to the dye that moves forward and backward constantly, but still moves toward
the manifold. The tubing can also pulse.
3. If the dye suddenly stops and flows back to the container, look for a clog somewhere in that
reagent stream. The path of the solution from the reagent container to the waste container must
be located after the flow cell.
4. Look at the transmission tubing and tubing on the manifold to see if there are air bubbles. If yes,
look at the connections prior to the location where the bubbles are visible. Look for crimped
tubing where the connection is made. There must be two O-rings at every tee or union connector.
5. Look at the flow of the dye to see the correct path of that particular reagent. This test can also
show connections that are not correct on the manifold or at the valve. A particular tubing can be
in a universal dye solution and the others in deionized water.
Identify valve problems with a dye test
Make a series of dye standards that can be operate with the method in use. Make two injections for
each standard and use a first-order-polynomial fit.
Another option is to make up four dye standards and write a new method with exactly the same
parameters for the method in use. The concentrations for the standards could be a sequence of four
numbers in descending order. Make sure that each standard is half of the preceding one (e.g., 20,
10, 5, 2.5). Refer to Table
1. Put all reagent tubing in deionized water. The manifold for this test agrees with the diagram of the
method that is operated. Make sure that the pump operates at 35 and the sample loop is
approximately 20 cm of the Teflon 0.8 mm ID.
2. Put the dye standards in the standard vials and start a calibration operation. Monitor the dye as it
fills the sample loop when the valve is in the load state. Monitor the dye as it flows to the manifold
when the valve is in the inject state.
3. The sample loop should be filled with dye when the valve moves from the load to the inject state.
If the sample loop is not filled completely, adjust the Valve Timing.
4. The calibration will pass if the standards were made correctly. If poor precision occurs, do a valve
test (refer to Identify injection valve faults
blockages on page 18). A poor precision is specified as a %RSD of more than 10%.
5. If the calibration is correct, the hardware and manifold are in good condition. To make sure that
the chemistry is correct, look at the standards and the full method procedure again. Make sure
Make a universal dye
2.
on page 17.
on page 18) and look for clogs (refer to
Find the flow
Find the flow
English 17