溴酚蓝作酸碱指示剂分光光度法测定土壤中有效磷

Spectrophotometric Determination of Available Phosphorus in Soil with Bromophenol Blue as an Acid-base Indicator

测定土壤中有效磷的标准方法及通用方法,通常采用酸或碱溶液浸提样品,调节浸提液pH值后用分光光度法测定。该方法过滤操作繁琐、酸碱指示剂二硝基酚颜色易受溶液底色干扰且有毒。对现有方法进行优化创新,提高检测效率,对土壤有效态分析及土壤质量评价具有重要意义。本文比较了不同浸提时间、不同浸提液酸度、不同酸碱指示剂等实验条件对检测结果的影响;采用离心分离代替过滤,使用溴酚蓝作指示剂调节pH。同时对比了溴酚蓝指示剂与标准方法的二硝基酚指示剂的检测结果,吸光度、标准物质准确度、未知样品检测结果均完全一致。研究表明使用溴酚蓝作酸碱指示剂,颜色突变更明显,不易受待测液底色影响,毒性低,测试数据准确。实验条件优化后的方法适用于酸性、中性及石灰性土壤有效磷的快速测定。

BACKGROUND:Standard and common methods for the determination of available phosphorus in soil are usually spectrophotometry methods.Before measurement,the sample is extracted by an acid or base solution,and the pH of the extracted liquid is regulated.The existing methods include complex operation steps such as filtration,and the acid-base indicator dinitrophenol is highly toxic.Most of all,the color of dinitrophenol is easily altered.OBJECTIVES:To optimize the existing method and improve detection efficiency,and then use the method for soil available state analysis and soil evaluation.METHODS:Different experimental conditions such as extraction time,acidity of the extraction and acid-base indicator type were compared.Centrifugal separation was used instead of filtration,and bromophenol blue was first used as the acid-base indicator.Detection results of bromophenol blue and dinitrophenol were compared.RESULTS:Comparing the detection results of the bromophenol blue indicator and dinitrophenol indicator,the absorbance,accuracy of national standard substance and unknown sample detection results were completely consistent.With bromophenol blue as the acid-base indicator,color mutation was obvious without any interference of bottom color.CONCLUSIONS:Bromophenol blue has low toxicity with accurate detection results.This improved method is appropriate for rapid determination of available phosphorus in acid,neutral and carbonate soils.