Abbott i-STAT Alinity - 3.1 - AlinIQ CWi - Customization Workspace for i-STAT

Closure
The closure creates an airght seal necessary for proper uid movement within the cartridge. The
closure also ensures that calibrant and sample remain contained within the cartridge during the tesng
cycle and subsequent disposal.
Cartridge on the le in the illustraon contains natural rubber latex on the snap closure. The cartridge
shown on the right is not made with natural rubber latex.
Heang elements
All i‑STAT cartridges require thermal control at 37°C (98.6°F), and include heang elements on the
underside of the sensor chips which are contacted and heated by the instrument's thermal probes.
Standardizaon and calibraon
Standardizaon is the process by which a manufacturer establishes “true” values for representave
samples. A mul-point calibraon curve, the slope or sensivity of which is dened by coecients in the
CLEW soware, is derived for each sensor by this standardizaon process. These calibraon curves are
stable over many lots.
A one-point calibraon is performed each me a cartridge requiring calibraon is used. During the rst
part of the tesng cycle, the calibrant soluon is automacally released from its foil pack and is
posioned over the sensors. The signals produced by the sensors’ responses to the calibrant soluon are
measured. This one-point calibraon adjusts the oset of the stored calibraon curve. Next, the
instrument automacally moves the sample over the sensors and the signals produced by the sensors’
responses to the sample are measured. While coecients are used rather than graphic calibraon
curves, the calculaon of the result is equivalent to reading the sample’s concentraon from an adjusted
calibraon curve.
Types of cartridge sensors
Sensors are thin lm electrodes microfabricated onto silicon chips. Sensing funconality is imparted to
each electrode by a number of chemically sensive lms coated over the acve region of the electrodes.
The cartridges have three dierent types of sensors built in: potenometric, amperometric, and
conductometric.
Potenometric sensors
In potenometric measurements, the dierence in potenal that exists between an indicator
electrode and a reference electrode is measured. Ion-selecve electrodes (ISE) are examples of
potenometric sensors. The indicator electrode is designed to be sensive to a parcular ion in a
soluon. In cases where other ions are sensed by the system, selecvity coecients can be used
to correct for this interference. An enzyme can be added to an ISE to produce ions from analytes
of interest that are not themselves ions.
Potenometric sensors ulize two important concepts. The rst concept is the Nernst Equaon
which relates the measured potenal to the acvity of the ion being measured. It is wrien as:
E = E° + RT/nF ln a
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i-STAT Alinity — System Operaons Manual Art: 745524-01 Rev. I Rev. Date: 02-Nov-2022