Hanna Instruments HI 110 - Manual (Page 11)

11
PREPARATION
Pour small quantities of the buffer solutions into clean beakers. If possible, use
plastic or glass beakers to minimize any EMC interferences.
For accurate calibration and to minimize cross-contamination, use two beakers
for each buffer solution. One for rinsing the electrode and one for calibration.
If you are measuring in the acidic range, use pH 7.01 or 6.86 as first buffer and
pH 4.01 or 1.68 (HI 112, HI 113) as second buffer. If you are measuring in the
alkaline range, use pH 7.01 or 6.86 as first buffer and pH 10.01, 9.18 or 12.45
(HI 112, HI 113) as second buffer.
PROCEDURE
Calibration can be performed in three (HI 110, HI 111) or five (HI 112, HI 113)
calibration points.
For accurate measurements, it is recommended to perform a three (HI 110, HI
111) or five-point calibration (HI 112, HI 113). However, at least a two-point
calibration is suggested.
The calibration buffer can be selected from the calibration buffer list that
includes the defined custom buffers in SETUP menu and the memorized
standard buffers:
• pH 4.01, 6.86, 7.01, 9.18, 10.01 (HI 110, HI 111)
• pH 1.68, 4.01, 6.86, 7.01, 9.18, 10.01, 12.45 (HI 112, HI 113)
The custom buffers are a special option that allows the user to calibrate in a
buffer solution different from a standard one. Up to two custom buffers can be
set in SETUP menu (see page 17). Each custom buffer value can be changed
in a ±1.0 pH window around the set value, during calibration, when it is
selected; the “BUFFER pH” tag will blink.
The instruments will automatically skip the buffer used during calibration and
the buffers which are in a ±0.2 pH window, around one of the calibrated
buffers.
All new calibrations will override existing stored calibration data in a ±0.2
pH window. The slopes adjacent to the new points will be reevaluated.
If the new calibration point has no correspondence in the existing stored
calibration data, it is added to it if this is not full (3 or 5 points), or the
instrument will ask which buffer will be replaced by the current buffer.
If at least a two-point calibration has been performed and an offset correction of
the electrode is wanted, keeping unchanged the existing slopes, perform a one-
point calibration with “OFFS” option selected in SETUP menu. If “Pnt” option is
selected, the slopes adjacent to the calibration points will be reevaluated.