4. Conclusion
A flow injection amperometric method and a new extraction procedure were proposed for the determination of available phosphorus in soil samples. Although the extraction was done by using a simple column made from a plastic syringe, a better extraction efficiency than the standard extraction procedure could be accomplished, which was more convenient to perform. The proposed extraction procedure may be a new alternative way to perform extraction of available P in routine analysis of soil. The FI amperometric method provided the precise and accurate results, with using of simple and cost-effective components to assemble the system, and consumed of smaller amount of chemicals. The amperometric detection also provided significant advantages over the spectrophotometric detection of the standard method, e.g., it can tolerate to silicate up to 1000 mg L−1 and does not suffer interference from turbidity and colored substances present in soil samples. The system could be developed to higher degrees of automation by control of the injection valve via a computer.