Multianalyte Determination

S. Rodriguez-Mozaz, S. Reder, M. Lopez de Alda, G. Gauglitz, and D. Barcelo, Simultaneous multianalyte determination of estrone, isoproturon and atrazine in natural waters by the River ANAlyser (RIANA), an optical immunosensor. Biosens. Bioelectron. 19, 633-640 (2004). 

Kampioti AA, da Cunha ACB, de Alda ML et al (2005) Fully automated multianalyte determination of different classes of pesticides, at picogram per litre levels in water, by online solid-phase extraction-liquid chromatography-electrospray-tandem mass spectrometry. Anal Bioanal Chem 382 1815-1825... 

Arrays can be divided into three groups depending on their design (Fig. 32.2). In the first design, each electrode is independently addressed (Fig. 32.2a). This type of array allows several practical applications. On one hand, these devices can be fabricated for obtaining the same information at different sites of a medium. For example, studies about the responses of neuronal cell cultures under different stimulus [85-87]. On the other hand, these devices can be designed to obtain different information at reduced spaces, i.e. multianalyte determination. Those arrays can be employed directly like detectors in flow systems [88] (where each electrode is maintained at a different potential) or they can be individually modified for specific analytes [89],... 

Borba da Cunha, A.C., M.J. Lopez de Alda, D. Barcelo, T.M. Pizzolato, and J.H.Z. dos Santos. (2004). Multianalyte determination of different classes of pesticides (acidic, triazines, phenyl ureas, anilines, organophosphates, mohnate and propanil) by liquid chromatography-electrospray-tandem mass spectrometry. Anal. Bioanal. Chem., 378 940-954. 

Matrix effects variable, depending on biorecognition principle and transduction element Direct analysis of the sample. Minimal sample preparation Limited multianalyte determination Possible automatization of the system Direct analysis after sampling is possible. 

Marchi I, Rudaz S, Veuthey JL (2009) Sample preparation development and matrix effects evaluation for multianalyte determination in urine. J Pharm Biomed Anal 49(2) 459—467. doi S0731-7085(08)00639-0 [pii] 10.1016/j.jpba.2008.11.040... 

J.L Martinez Vidal, A. Garrido Frenich, T. Lopez Lopez, I. Martinez Salvador, L. Hajjaj el Hassani, M. Hassan Benajiba, Selection of a representative matrix for calibration in multianalyte determination of pesticides in vegetables by LC-ESI-MS-MS, Chromatographia, 61 (2005) 127. 

In the recent past, multianalyte determination has found increased applications, i.e. specific and multiple reactions favor a system that allows the specific determination of each reaction, using the same principal measurement methods, detectors and conditions. In keeping with this idea, a flow injection thermometric method based on an enzyme reaction and an integrated sensor device was proposed for the determination of multiple analytes. In principle the technique relies on the specificity of enzyme catalysis and the universality of... 

The integrated system, including transducer and enzyme reactor, provides improved reliability and stability in multianalyte determinations, as compared with discrete thermal sensor systems. In addition, application of micromachining and IC technologies is of benefit for the manufacture of uniform, cheap thermal transducers with flexible shape, size, and resistance, as well as delicate microstructure on the chips. The good thermal insulation of the transducers from the flow stream eliminates interference from the reactants on the transducers, and the intrinsic stability of the transducers obviates the need for frequent recalibration of the sensors. 

If a single analyte is to be detected, a simple flow-through microdialysis/microchip system may suffice. If multianalyte determination is needed, a separation-based microchip device can allow resolution and detection of several analytes in a single sample (Section 48.5.4). In flow-through devices, the perfusate is directed to an array of sensors, which may be also be modified to allow detection of different analytes and improve detection sensitivity. 

In the loop of the injection valve, for preconcentration, multianalyte determinations, or simultaneous blank and sample measurements. 

On the other hand, GD coupled to high mass acquisition spectral rate time-of-flight mass analyzers offers great analytical potentials in depth profiling analysis, especially for thin layers, where the composition of the sample changes rapidly with time (depth) and the simultaneous multianalyte determination should be carried out at every sample depth [32,33]. 

Multielectrode configuration allows parallelization of the assays. In this way, eight-electrode arrays are available, in a way that material employed in conventional ELISA microtiter plates (8x 12 wells) such as eight-channel micropipettes could be used. This format was employed for detection of antimicrobial sulfonamides in honey [44] or clen-buterol in livestock urine [55] with 8 or 16-electrode arrays, respectively. Apart from these arrays, dual-electrode formats in which both working electrodes share the reference and auxiliary electrodes can be employed for single [45] or multianalyte determinations [143], similarly to what happens with a four-channel SPCE (screen-printed carbon electrode) design for simultaneous bianalyte determination [70] (see also Section 9.7.1). 

On the other hand, even when field analysis is necessary in many steps of the food chain (farms, crops, etc.) and small devices with portable instmmentation are required, food processes in industries need in many cases automatization, especially when the number of samples is high (e.g., food quality). Moving the approaches from off- to at-, on-, and in-line analysis is always desirable, but all the possibilities have to be considered and all of them need innovative approaches for generating the ideal food analysis platform. In this section, some issues related to multianalyte determination and automatization are considered. 

The possibility of determining different analytes in the same sample (multiplexing) is of paramount importance nowadays. When dealing with multianalyte determination, different strategies could be followed [172] ... 

Chromatographic techniques are suitable for quantitative multianalyte determinations. In particular, LC is the technique of choice for the direct analysis of polar, nonvolatile, and heat-sensitive compounds, such as water-soluble vitamins (see Figure 18.3 for an example) moreover, having no molecular weight limitations, it can be used for the separation of cobalamins, polyglutamates, FAD, and CoA. LC is also the most common technique used for the concurrent analysis of fat-soluble vitamins and provitamin A carotenoids (see Figure 18.4 for an example). 

Microdialysis LC-ECD Well-established technique New LC technologies can achieve rapid separation Capable of multianalyte determination 10—30 min 0.03-2.2 nM [45,107-109]... 

Garcia-Jimenez, J. F., M. C. Valencia, and L. F. Capitan-Vallvey. 2006. Improved multianalyte determination of the intense sweeteners aspartame and acesulfame-K with a solid sensing zone implemented in an FIA scheme. Anal. Lett. 39(7) 1333-1347. 

The following sections will describe the main features and characteristics of flow analysis methodologies proposed for the individual determination of cyclamate and saccharin, and for the multianalyte determination of acesulfame-K, cyclamate, and saccharin. 

Only two flow analysis methods have been published for multianalyte determination including cyclamate as analyte. Both methods determine cyclamate with other artificial sweeteners. One of them used stabilized systems of filter-supported BLMs in a FIA manifold [72], and the other is based on CE with contactless conductivity detection employing a sequential injection manifold based on a syringe pump [77]. 

Saccharin is also determined with FIA methodologies, which allow multianalyte determination. These methodologies include methods cited previously for acesulfame-K and/or cyclamate a method based on electrochemical detection of these three artificial sweeteners using stabilized systems of filter-supported BLMs [72] online dialysis for sample pretreatment prior to the simultaneous determination of saccharin and caffeine, benzoic acid, and sorbic acid by HPLC-FID [76] and molecular spectroscopic methods in the UV region based on the transient retention of analytes on solid phases, silica Cjg [74], and quaternary amine ion exchanger [75]. 

Wu J, Zhang Z, Fu Z, Ju H (2007) A disposable two-throughput electrochemical immunosensor chip for simultaneous multianalyte determination of tumor markers. Biosens Bioelectron 23 114-120... 

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