Spectrophotometric flow-batch determination of aluminum in plant tissues exploiting a feedback mechanism Original Research Article

The feasibility of flow-batch systems to carry out procedures exploiting feedback mechanisms is discussed, and a flow-batch analyzer is proposed for spectrophotometric determination of aluminum in plant digests. As eriochrome cyanine R (ECR) was used as chromogenic reagent and considering the pronounced pH dependence of absorbance of the Al-ECR, in-line individual pH conditioning was performed. For pH matching, the m-cresol purple indicator was monitored in order to reach the required acidity for every assayed sample. The proposed system handles about 15 samples per hour, requires only 60 μg ECR per determination, and yields reproducible results (R.S.D.<1.0%). A quadratic correlation (r>0.999, n=6) was achieved within 0.25 and 6.00 mg l−1 Al (dry basis). Results are in agreement with inductively coupled plasma atomic emission spectrometry.