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- Winquist, Fredrik, et al.
(författare)
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Determination of ammonia in air and aqueous samples with a gas-sensitive semiconductor capacitor
- 1984
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Ingår i: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 164, s. 127-138
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Tidskriftsartikel (refereegranskat)abstract
- The properties of a new type of ammonia gas-sensitive semiconductor capacitor are described. The sensor is based on a palladium MOS field-effect capacitor with a thin layer (3 nm) of iridium surrounding the palladium gate. The lower limit of detection for ammonia in air is 1 ppm (0.59 mg kg−1). The analytical characteristics and temperature-dependence of the sensor in measurements of ammonia in air are evaluated. Ammonia in aqueous solutions is determined by the use of a continuous flow system utilizing a gaspermeable membrane in combination with the sensor. The calibration plot of the voltage drop of the capacitor vs. ammonia concentration in 150-μl samples is linear in the concentration range 0.2 × 10−6–5 × 10−5 M. Ammonia is determined in rain and river water as well as in whole blood and blood serum; 15 samples per hour can be assayed. Analytical recovery studies and the selectivity properties of the system are described and discussed. Finally, the properties of the flow-through system in continuous monitoring are described.
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| 2. |
- Winquist, Fredrik, et al.
(författare)
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Determination of urea with an ammonia gas-sensitive semiconductor device in combination with urease
- 1984
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Ingår i: Analytica Chimica Acta. - : Elsevier. - 0003-2670 .- 1873-4324. ; 163, s. 143-149
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Tidskriftsartikel (refereegranskat)abstract
- An ammonia gas-sensitive Ir/Pd MOS capacitor is used for urea determinations with the aid of urease in two different systems. One combination utilizes a reaction column with immobilized urease in a flow-injection system. The lower limit of urea detection for 150-μl samples was 0.2 μM. Urea in whole blood and blood serum was determined after a 500-fold dilution, and 15 samples per hour could be assayed. The relative standard deviation was 4.6% (n=10). Recovery tests were satisfactory. Values obtained for urea in serum correlated well with those from a spectrophotometric method. The other combination is based on a small flow cell with free urease enclosed between a dialysis membrane and a gas-permeable membrane. Urea was determined in the concentration range 0.01–50 mM. The enzyme probe could be used for up to four days without changes of behaviour.
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| 3. |
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