Introduction 1 2 2 3 4 5 6 7 8 9 10 11 12 14 13 8 13 15 32 22 24 33 13 34 36 21 37 38 8 13 14 39 2 3 34 40 41 42 17 27 41 12 28 18 37 31 32 8 20 22 23 33 36 41 16 16 43 39 44 15 28 30 24 26 21 25 45 46 47 48 49 50 22 25 51 52 27 53 54 55 29 30 3 3 −4 2 56 In this work, the electrodes were moulded from a 40% carbon fibre-filled polystyrene, which was also found to be suitable for performing electrochemical detection. This paper presents the first report of the use of CAdSV at an in-line plated BiFE in an integrated three-electrode injection-moulded plastic micro flow cell. Experimental Instrumentation Voltammetric measurements were performed using an Autolab electrochemical system (PSTAT 10, Eco Chemie B.V., Utrecht, The Netherlands) controlled with GPES software (v4.6, Eco Chemie) running on a PC. Rotating disc electrode experiments 2 3 Flow cell experiments A gravity-fed flow system was used comprising a reservoir formed from a disposable syringe body (20 ml), and narrow-bore PTFE tubing (0.032 in. i.d., Lee Products, Gerrards Cross, UK). The flow was controlled with a manual two-way valve (Part No. 2420, Omnifit, Cambridge, UK). Barbed (1/16″) polypropylene female Luer fittings (Cole-Parmer, Hanwell, London, UK) enabled connection of the flow system to the injection-moulded flow cell. Electrical connection to the Autolab electrochemical system was made using crocodile clips. Chip fabrication 1 Fig. 1 A B C D E  Reagents and solutions 3 Procedure Procedure Procedure Procedure Formation of the Ag/AgCl miniaturised reference electrode 3 Ex situ electroplating of the BiFE on the rotating disc electrode (RDE) Acetate buffer Bi(III) plating solution. 100 ppm Bi(III) in 1 M acetate buffer (pH 4.5). Plated for 5 mins at −1.0 V in a quiescent solution. LiBr/ HCl Bi(III) plating solution. 0.02 M Bi(III) in 0.5 M LiBr and 1 M HCl. Plated for 60 s at −0.28 V in a quiescent solution. The RDE was then carefully rinsed before transferring it to the analysis solution. In-line electroplating of the BiFE on the flow cell working electrode Acetate buffer Bi(III) plating solution. 100 ppm Bi in 0.1 M acetate buffer (pH 4.5). Plated for 5 mins at −1.0 V at a flow rate of 37.1 μl/s. LiBr/ HCl Bi(III) plating solution. 0.02 M Bi(III) in 0.5 M LiBr and 1 M HCl. Plated for 120 s at −0.28 V at a flow rate of 37.1 μl/s. After formation of the BiFE, the plating flow stream was flushed with water and switched to the analysis stream. Bismuth film cleaning procedure The Bi(III) film was cleaned of the remaining adsorbed complexes by holding the electrode at a potential of −1.3 V for 30 s in 0.1 M HCl. Bismuth film removal 3 In-line plating of MFE on the flow cell working electrode 3 Mercury film cleaning procedure 3 Mercury film removal 3 Results and discussion The in-line prepared BiFE was assessed for its suitability in performing CAdSV of Co(II) and Ni(II). Various parameters, such as flow rates, solution composition, plating parameters and square-wave conditions, were studied to investigate the electrochemical behaviour of the Bi(III) films prepared on the injection-moulded carbon fibre electrodes. Investigation of the effect of flow rate during the plating and accumulation stages 2 Fig. 2 a b c d e f 2  2 R 2 Effect of composition of the BiFE plating solution 15 24 26 28 29 30 3 Fig. 3 a a b b c d c e f d g h 2 e  Effect of solution parameters on the system behaviour Buffer concentration 4 Fig. 4 a b c b c a c a b 2 c c  Effect of DMG concentration 4 Effect of nitrite concentration 4 5 5 5 5 5 Fig. 5 a a 2 b 2 b c 2 d 2 c e 2 f 2 d 2 h g e 2 j k  Effect of varying the square-wave (SW) stripping parameters Frequency 6 Fig. 6 a b c d e 2 b e e  Step potential 6 Amplitude 6 Deposition potential 6 Accumulation time 6 Analytical characterisation 2 y x y x R 2 y  x R 2 −5 −5 7 57 58 Fig. 7 AdSV of Ni(II) on a mercury film electrode. Here decimal numerals indicate the film number and roman numerals indicate replicate analyses carried out on the same film. Carried out with a 200 ppb sample in 0.1 M ammonium buffer (pH 9.3) with 0.1 mM DMG (deaerated) at a flow rate of 16 μl/s. SW conditions: conditioning potential −1.4 V (10 s), deposition potential −0.5 V (200 s), equilibration time 5 s, pulse frequency 25 Hz, pulse amplitude 10 mV and step potential 4 mV. Scan: −0.5 V to end potential −1.4 V. Data were smoothed with a level-2 Savitzky–Golay filter  Conclusions The application of a BiFE for the determination of Co(II) and Ni(II) by square-wave CAdSV under flow conditions in a non-deaerated solution has been demonstrated. The injection-moulded carbon-fibre-filled polystyrene electrodes have proven to be suitable supports for the formation of bismuth films. The LiBr-containing plating solution was found to offer superior performance for both the RDE and the flow cell under the alkaline conditions required for CAdSV. The application of a flow stable BiFE in an inexpensive sensor system permits the possibility of autonomous on-site industrial and environmental monitoring. The inherent disposability of the devices coupled with their mercury-free status should advance the scope of the sensor to point-of-care clinical applications.