Integrated sample processing and detection

Figure 5.1 — Classification of (bio)chemical flow-through sensors based on integrated reaction, separation and detection according to whether the three processes take place sequentially (A,B) or simultaneously (C) at the sensing microzone. S sample R reagent. (Reproduced from [1] with permission of the Royal Society of Chemistry).

Recent achievements in the miniaturization of MS instrumentation gave rise to the first instruments with characteristic dimensions in the micrometer range52 54 as in the case of microsystems dedicated to analysis and chemical processing. Such achievements should lead in the near future to the development of a fully integrated setup including the steps of both sample preparation and detection. 

Fig. 17 Detection of B. anthracis from murine blood, (a) Detector responses during all three stages of sample processing and analysis are portrayed in terms of total analysis time. The SPE trace (green) was taken from off-line DNA extraction of the same murine sample and is representative of the total DNA concentration observed in a typical extraction. The temperature (blue) and fluorescence intensity (black) represent on-line data, with a total analysis time <24 min. Three sequential injections and separations were carried out to ensure the presence of amplified product, (b) Fluorescence data from an integrated analysis of a blank sample (no DNA) control with marker peaks labeled. The inset represents valve actuation during co-injection, with the PR and MR pumping inlets indicated by the arrows, (c) Zoomed view of the first separation shown in (a), with the product peak marked. The second and third runs are overlaid with the time axis cropped. Inset shows the sizing curve of inverse migration time vs. logfbase pairs) with both the sizing standard peaks (open diamonds) and product (square) plotted for all three runs shown in (a). From these data, the product was 211 2 bp. Reproduced from [10] with permission...

In another example of integrated sample processing, Lee et al. accomplished cell lysis, DNA purification, and PCR amplification for pathogen detection using a single-chamber device. In this work, the authors developed a Laser-Irradiated Magnetic Bead System (LIMBS) for cell lysis and... 

It is used in IC systems when the amperometric process confers selectivity to the determination of the analytes. The operative modes employed in the amperometric techniques for detection in flow systems include those at (1) constant potential, where the current is measured in continuous mode, (2) at pulsed potential with sampling of the current at dehned periods of time (pulsed amperometry, PAD), or (3) at pulsed potential with integration of the current at defined periods of time (integrated pulsed amperometry, IPAD). Amperometric techniques are successfully employed for the determination of carbohydrates, catecholamines, phenols, cyanide, iodide, amines, etc., even if, for optimal detection, it is often required to change the mobile-phase conditions. This is the case of the detection of biogenic amines separated by cation-exchange in acidic eluent and detected by IPAD at the Au electrode after the post-column addition of a pH modiher (NaOH) [262]. 

Determining the occurrence of a chemical in the environment should be viewed as an integral process that involves several steps including sampling, storage, sample preparation, and ultimately detection of the chemical(s) of interest. Each of these steps has profound effects on the whole analytical and detection process of PPCPs in the... 

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