Wyniki 1-2 spośród 2 dla zapytania: authorDesc:"Dmytro SNIZHKO"

Ultrafast Potentiostat as Compromise between Current Sensitivity vs. Response Time DOI:10.15199/48.2019.08.24

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This work is considered to the problem of the response time of instrumentation with saving of sensitivity in electrochemical measurements. As authors [1] claims “The ability to measurement nA to pA currents at nanosecond timescales remains a challenge." It is a traditional problem of engineers that is a decrease of measurement current range and response time, i.e. an increase current sensitivity of a potentiostat and an enlarge bandwidth for an analytical signal is. To save the current sensitivity of potentiostat for higher signal time resolution the reduction of a charge registration limit is asked that is limited by a noise level of electronic components. As an example of this problem, the modern femtoampere amplifier LMP7721 by Texas Instrument which has typical input bias current at 3 fA and input-referred current noise at 0.01 pA/Hz-1/2. For a current detection limit at 10 fA the measurement bandwidth reaches (current detection level/input current noise)2 =1 Hz, i.e. time resolution for measurements is 1 s, amount of electrons for detection by the amplifier is greater than 6 000 electrons. So the physical limit of modern electronics is greater than a single electron detection level for a real potentiostat circuit. Electronic elements as wires, semiconductors chips, resistors, and others have electronic noises which specify a detection level in an electrical circuit, and its reduction to absolute zero level is practically impossible. On the other hand, the utilization of novel construction technics and measurement methods can overcome limiting factors. In this paper, we try to analyze the construction of a tradition potentiostat to decrease the response time to nanosecond resolution and to determine sensitivity which we can obtain with commercial operational amplifiers. Investigations of possibilities to construct an ultrafast potentiostat as well as its utilization were considered in different articles [2-20]. Th[...]

Apparatus "Spark" for luminescent and electrochemiluminescent measurements DOI:10.15199/48.2018.06.07

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Electrochemical methods are very attractive to solution content characterization as sensitive, selective, quick, and quite simple technics. A limiting factor of electrochemical technics is electrons amount transferred during the analytical reaction, which should be enough for detection by electronics. The last one is determined by the versatility of modern operational amplifiers they set up a base of a potentiostat, main instrumentation for voltammetric electroanalysis. A solving this problem in electroanalysis is possible to use an electrogenerated chemiluminescence phenomenon (ECL) [1-4]. The registration of the light emission is attractive method for analysis chemical and biochemical reactions [5-8]. ECL is a light emission that is a result of electrochemical reactions that appear during an electrode polarization in specific solutions. The difference in chemical mechanisms of a light generation determines riches of ECL analytical techniques [4, 9]. This powerful analytic method is widely used and foremost in immunochemistry [10]. Routine analyses by this method are characterized by a registration of a weak light during electrolysis of a sample solution so photomultiplier tubes (PMT) [11] frequently are used as a detector in ECL analyzers. Commercial instrumentation for immunochemical assays is limited for a research work as expensive and inflexible devices. [12] Their high productivity is not too important in research as so mainly development works ask frequent changes in the functionality of measurement instrumentation. To conduct electrochemiluminescent analysis is needed combination of luminescent and electrochemical instrumentation. Different electrochemical potentiostats support a data collection in an additional channel, thus attractive possibility to use combination them with PMT as a base for ECL analyzer. Technician problem of a direct connection of PMT to a data acquisition system is a general problem of data[...]

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