An electroanalytical instrument for determining by amperometry the presence or quantity of an analyte in an aqueous sample comprising: a sealed housing which is compartmentalised, wherein the sealed housing has an exterior compartment defining a receptacle for the aqueous sample and interior compartments; an elongate pivotal arm mounted pivotally at a proximal end on the sealed housing, wherein the elongate pivotal arm houses a potentiostat; a pivotal forearm joined pivotally to a distal end of the elongate pivotal arm, an electrochemical sensor capable of being mountable in or on an anterior wall of the pivotal forearm to extend inferiorly to the elongate pivotal arm; and a mounting for electrical contact pins which is mounted sealingly on the distal end of the elongate pivotal arm, or electrical contact pins on the distal end of the elongate pivotal arm, wherein the electrical contact pins are electrically connectable to the potentiostat to apply a potential to the electrochemical sensor, wherein the elongate pivotal arm is configured to pivot between a fully extended position and a fully flexed position whereat an inferior part of the electrochemical sensor may be immersed in the aqueous sample in the receptacle and wherein the pivotal forearm is configured to pivot between a fully open position whereat the electrical contact pins are exposed and a fully closed position whereat the electrical contact pins are configured for positioning in operative contact with the contacts on the superior part of the electrochemical sensor whereby when the elongate pivotal arm is in the fully flexed position and the pivotal forearm is in the fully closed position the electrical contact pins are configured to interface with the electrochemical sensor and the aqueous sample. a sealed housing which is compartmentalised, wherein the sealed housing has an exterior compartment defining a receptacle for the aqueous sample and interior compartments; an elongate pivotal arm mounted pivotally at a proximal end on the sealed housing, wherein the elongate pivotal arm houses a potentiostat; a pivotal forearm joined pivotally to a distal end of the elongate pivotal arm, an electrochemical sensor capable of being mountable in or on an anterior wall of the pivotal forearm to extend inferiorly to the elongate pivotal arm; and a mounting for electrical contact pins which is mounted sealingly on the distal end of the elongate pivotal arm, or electrical contact pins on the distal end of the elongate pivotal arm, a mounting for electrical contact pins which is mounted sealingly on the distal end of the elongate pivotal arm, or electrical contact pins on the distal end of the elongate pivotal arm, wherein the electrical contact pins are electrically connectable to the potentiostat to apply a potential to the electrochemical sensor, wherein the elongate pivotal arm is configured to pivot between a fully extended position and a fully flexed position whereat an inferior part of the electrochemical sensor may be immersed in the aqueous sample in the receptacle and wherein the pivotal forearm is configured to pivot between a fully open position whereat the electrical contact pins are exposed and a fully closed position whereat the electrical contact pins are configured for positioning in operative contact with the contacts on the superior part of the electrochemical sensor whereby when the elongate pivotal arm is in the fully flexed position and the pivotal forearm is in the fully closed position the electrical contact pins are configured to interface with the electrochemical sensor and the aqueous sample.