No abstract

In this work, we describe for the first time the association of batch injection analysis (BIA) with dual pulse amperometric (DPA) detection for simultaneous determination of multi-analytes using a single working electrode. The sequence of pulses is selected in such a way that the analytes are detected individually and independently at the same working unmodified electrode (using a correction factor). BIA provides fast response (high-throughput analysis), elevated precision, reduction of sample volumes and minimization of waste. To illustrate the potential of this method, BIA-DPA was applied for the simultaneous determination of biodiesel preservatives (tert-butylhydroquinone and butylated hydroxyanisole) and pharmaceutical compounds (paracetamol and caffeine or dipyrone and caffeine).

In this study, we describe for the first time the application of an internal standard method to compensate for random errors associated with the injection procedure in batch injection analysis (BIA) systems with multiple pulse amperometric detection. A sequence of potential pulses was selected in such a way that the internal standard (IS) compound was detected individually at one potential pulse and both the IS and analyte, were detected at another potential pulse. The current ratio (IIS+analyte/IIS) was used in the construction of the calibration curve and then to compensate for random errors. The use of disposable syringes or manual pipettes in BIA systems increases the robustness of the method and dispenses with skilled operators.

Chemical analysis performed at the place of the sampling ("in loco" analysis) rather than in a conventional laboratory is often attractive. A portable assay method for field work enables sample collection and data analysis in realtime, the reduction in time consumption and total analyses costs [1]. Furthermore, portable assays is one of the main trends in analytical chemistry due to the rapid growth of the potentials of such analysis [2] and the increasing demands in field analysis for fuel [3], forensic [4], and environmental [5] samples. In electrochemical detection, many companies commercialize a series of portable instruments suitable to in field analysis, as handheld potentiostats and screen-printed electrodes (SPEs) containing a series of modifiers (e.g., multi-and singlewalled carbon nanotubes, graphene, bismuth and Prussian blue) [6]. These simple devices allows the simple adjustment of SPEs in many electrochemical cells, as batch [7] and flow [8,9] systems, as well measurements in drops of solution ( % 50 mL) [10]. Other suitable approach to development of portable analytical methods is Batch Injection Analysis (BIA) [11]. This system is based on the injection of a sample plug through a micropipette tip directly onto the working electrode surface (wall-jet configuration) which is immersed in a large-volume of blank solution. BIA and flow injection analysis (FIA) [12] have high analytical frequency, low consumption of reagents and samples. Nevertheless, BIA is more simple and portable, because the absence of pump, valves and tubes [13]. This work proposes the use of a very simple and portable homemade batch-injection analysis cell to accommodate screen-printed electrodes (BIA-SPE) to determination of herbicide carbendazim (CZIM), hydroquinone (HQ), and catechol (CAT) in tap water. The BIA-SPE system has capability to increase the applicability of electrochemical methods for in field analysis.The BIA-SPE homemade electrochemical cell was constructed from an acrylic rod (1i = 4.0 cm, height = 4.0 cm). As presented in Figure 1, a hole (diameter = 3.1 cm; height = 4.0 cm) was drilled from one side of the rod (top side) and the other side was maintained closed (bottom side). The top side was closed with an acrylic cover with two holes. The first was used for insertion/exchange of the supporting electrolyte and the second was used for the reproducible positioning of the 1 mL combitip of electronic pipette (Figure 1). The combitip with a regular external diameter (6 mm) was firmly introduced into the hole (diameter = 6.1 mm) in such a manner that the distance between the pipette tip and the electrode surface was always the same (highly reproducible injection procedure). Optionally an insulin syringe also can be ) and low detection limits (nanomolar level). Moreover, the BIA-SPE cell presented better stability (RSD % 0.4 %) than a conventional flow injection cell for SPE (RSD % 5.0 %) in organic media. The proposed homemade BIA-SPE cell is very simple, inexpensive and can be easily constructed in any laboratory.