An Inexpensive Sequential Injection Analyzer for the Analytical Laboratory

Abstract

A home‐made multiposition valve and a syringe pump were specially designed and fabricated using inexpensive and easily available materials and equipment in the laboratory. The hardware and software for controlling the devices and displaying the signal were developed. Both devices were combined to obtain a sequential injection analysis (SIA) system and used by incorporating with a spectrophotometric detector. The developed SIA analyzer is computerized. The SIA system can select the samples and reagent, which is then sequentially injected into the holding coil where the sample and the reagent zones are taking place. Both sample and reagent zones are delivered into a flow‐through detector where the reaction product is measured spectrophotometrically. The program for interfacing the SIA instrumentation with a personal computer was also developed using Microsoft Visual Basic™. This can enable a wide range of chromophores to be automatically detected. The fabricated SIA analyzer was tested for determining Fe(III) in standard solution based on Fe(III)‐thiocyanate complex. The RSD for 11 replicates determination of 4.0 mg/L iron was 1.08%. The detection limit (3σ) and the determination limit (10σ) were 0.34 and 1.13 mg/L, respectively. A linear calibration curve over the range of 1.0–7.0 mg/L iron and correlation coefficient of 0.9977 were established. The analyzer has been successfully applied to the determination of total iron in waters. Results obtained by both the proposed SIA and AAS methods were in excellent agreement.