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pH-2 Operator’s Manual – OPTI CCA-TS
pH
ANALYTES
Interferences
Optode pH measurements have a known sensitivity to the blood ionic strength 3, which is determined
primarily by variation in serum levels of sodium. The OPTI CCA-TS utilizes an internal Na
+
sensor to
actively compensate and correct for this sensitivity. That is, the OPTI CCA-TS’s reported pH has no
measurable interference from hyponatremic or hypernatremic samples, nor for ionic strength variations
within the physiologic limits of 100 to 190 mmol/L.
Heparin salts are the only acceptable anticoagulants. Other anticoagulants such as citrate, EDTA, oxalate,
and fluoride cause significant interferences to the pH sensor.
The following exogenous interferents were quantified in tonometered plasma, showing interferences to
dyes which typically have short half-lives within the body before being metabolized by the liver.
Substance amount pH change
Sodium fluorescein 26 mg/dL unstable
Cardio (indocyanine) green 0.5 mg/dL -0.04
Methylene blue 25 mg/dL -0.16
Only clear, uncolored quality control materials, such as OPTI CHECK or OPTI CHECK PLUS brand
aqueous controls should be used with the OPTI CCA-TS system. Colored materials, including proficiency
testing materials, may interfere with the pH measurement, or fail to be properly aspirated
.
Reproducibility
Typical Within-Run ( Swr ), Between-Day ( Sdd ) and Total ( ST ) Precision is determined from 1 run per
day with 2 replicates per run for 20 days on each of two OPTI CCA instruments. pH is expressed in pH
units.
Material mean S
wr (CV%)
S
dd (CV%)
S
T (CV%)
OPTI CHECK PLUS
(aqueous control solution)
Level 1 7.166 0.003 (—) 0.003 (—) 0.003 (—)
Level 2 7.414 0.0003 (—) 0.002 (—) 0.002 (—)
Level 3 7.620 0.0005 (—) 0.003 (—) 0.006 (—)
Serum 7.524 0.001 (—) 0.003 (—) 0.003 (—)
Reduced Bovine Hemoglobin 7.44 0.0005 (—) 0.002 (—) 0.003 (—)
Solution
All specific performance characteristics tests were run with default instrument calibration and after
normal recommended equipment quality control checks were performed (see Operator’s Manual).
Specimens at each level were analyzed in replicates of two for 20 days. The within-run and
between-day standard deviations were calculated by the analysis of variance method.