基体效应对火焰光度计测定土壤和植株钾素含量准确性的影响

为定量研究基体效应干扰对火焰光度计测定土壤或植株钾素的影响,测定了土壤和植株标准样品中各形态钾素(水溶性钾、速效钾、缓效钾、土壤全钾和植株全钾)待测液和具有相同基体钾标液的电信号值,研究了基体效应对测定结果的干扰。结果表明:当钾标准溶液和待测液的基体一致时,标准样品各形态钾素的测定结果均具有较好的回收率。若各形态钾素的测定均使用基体为纯水的钾标准溶液,则基体效应干扰会使测定结果存在一定的负误差,尤其是对土壤全钾和植株全钾待测液的电信号值影响极大。稀释能够在一定程度上减少基体效应的干扰,但在通常的土壤和植株样品待测液稀释倍数范围内,不同基体钾标液的电信号值仍差异较大。因此,在采用火焰光度计测定土壤和植株样品钾素含量时,为消除基体效应干扰,应当保证钾标准溶液的基体与各形态钾素待测液的基体相同。

Influence of matrix effect on determination accuracy of potassium content in soil and plant samples by flame photometer

In order to study the interference of matrix effect on the measurement of soil and plant potassium content by flame photometer, the electrical signals of the K⁺ test solutions and K⁺ standard solutions with same matrix were measured. The K⁺ test solutions consisted of water soluble potassium, rapidly available potassium, slowly available potassium, total potassium of soil and total potassium of plant. The interference of different types of matrixes and different dilution factors of matrixes were studied. It was shown that the K⁺ content of standard samples had a high recovery rate when the matrixes of test solutions and standard solutions were the same. It caused a negative error, especially for total potassium of soil and total potassium of plant, when the matrix of K⁺ standard solutions was deionized water. The effect of matrix could be reduced by dilution of matrix. However, within the commonly adopted dilute times of soil or plant sample, the measured electrical signals of K⁺ standard solutions with different matrixes still varied. In order to eliminate the interference caused by the differences of matrixes, the matrixes between K⁺ test solution and K⁺ standard solution should be kept consistently when the potassium contents of soil and plant samples were measured by flame photometer.