Total phosphorus is one of the critical evaluation indexes for water eutrophication. Excessive phosphorus discharge into rivers, lakes and reservoirs will trigger algal blooms and destroy aquatic ecological balance. Traditional laboratory total phosphorus analysis requires water sample collection, transportation, high‑temperature digestion inside the laboratory, and colorimetric measurement. Water sample preservation and long‑distance transportation may cause component change and measurement deviation, and the whole testing cycle is relatively long. Portable integrated digestion‑detection instruments make it possible to complete sample pretreatment and quantitative analysis directly at sampling sites. YUNTANG YT‑BTP portable total phosphorus detector is developed in accordance with GB11893‑89 ammonium molybdate spectrophotometry standard, realizing the integration of field digestion and on‑site detection.

This instrument adopts high‑strength PVC portable suitcase structure. It is equipped with an 8‑inch high‑definition touch screen and Android 7.1.1 operating system. The digestion module supports dual‑temperature‑zone independent control with 8 digestion positions. Heating speed can reach up to 165 ℃ within 10 minutes. Intelligent PID temperature control ensures temperature control accuracy of ±0.5 ℃. Digestion temperature can be adjusted from room temperature to 200 ℃. Pre‑set digestion modes for COD, total phosphorus, total nitrogen and other conventional water quality indicators are stored in the system, and users can also define three sets of custom digestion programs according to special experimental requirements. The detection unit supports dual color‑measurement modes: prefabricated test‑tube colorimetry with 360° precise rotary device and cuvette colorimetry. The 360° rotating test‑tube detection structure greatly improves measurement repeatability and stability, effectively reducing measurement error caused by test‑tube placement deviation.

Built‑in large‑capacity 48V 8AH lithium battery supports more than 6 hours of continuous operation under the condition of simultaneous digestion and detection, fully satisfying all‑day field sampling missions. The device integrates a thermal printer, supporting automatic and batch report printing, as well as QR‑code printing for traceability management. Diversified data transmission channels including Wi‑Fi, 4G remote transmission and RJ45 wired network are reserved. Detection data can be uploaded to the supporting cloud platform, where users can view historical records and dynamic change trend remotely on mobile phones or computers. The instrument stores more than four demonstration operation videos inside, so field technicians can watch guidance videos while operating experiments, lowering technical thresholds for new operators. It also carries GPS positioning function, which automatically records longitude and latitude information of sampling points and stores geographic information together with detection data.

In field method verification experiments, we collected multiple groups of lake and river surface‑water samples. Digestion and determination were completed on‑site with YT‑BTP, meanwhile parallel water samples were transported back to laboratory for reference detection by bench‑top spectrophotometer. The test range of the instrument is 0.02‑30 mg/L by segments. The indication error is ≤±5%, repeatability less than 0.5%, stability less than 0.5%. Comparative experimental results show good data consistency between portable field test and laboratory reference results. Users can also build custom calibration curves to adapt to special water matrix samples. It should be emphasized that prefabricated reagent tubes should be stored properly, and blank control test shall be carried out before batch sample measurement. YT‑BTP portable total phosphorus detector is suitable for environmental monitoring stations, municipal sewage plants, scientific research universities and third‑party testing agencies to conduct on‑site emergency monitoring and routine field investigation of total phosphorus in surface water and wastewater.