# Rapid Determination of Molybdenum (VI) in Water Using Phenylfluorone-Modified Test Strips Combined with Colorimetry and LAB Color Space Analysis

## TL;DR

A new rapid and portable method for detecting molybdenum (VI) in water using test strips and color analysis is developed and validated.

## Contribution

A PF-modified test strip with dual readouts (visual and LAB color space) enables rapid and accurate on-site detection of Mo(VI) in water.

## Key findings

- The PF-modified test strip provides a detection range of 0–0.8 mg L−1 with a detection time of 2.5 minutes.
- The LAB color space analysis showed a strong linear relationship (R² = 0.992) between color development and Mo(VI) concentration.
- Test strip results matched UV-vis spectrophotometry with relative errors below 5% in real water samples.

## Abstract

Excessive molybdenum (VI) (Mo (VI)) in water threatens environmental safety and human health, yet rapid on-site methods for Mo (VI) determination remain limited. Here, we propose a rapid method for Mo (VI) determination using phenylfluorone (PF)-modified test strips with dual readouts: visual colorimetry and image-based analysis in the CIELAB (Lab*) color space, and demonstrate its applicability using urban park water samples. Based on visual colorimetry, a standard color card was established, providing a screening range of 0.08 to 0.8 mg L−1 (A blank (0 mg L−1) was used as the baseline reference). Moreover, by the LAB color space, the linear relationship between the color development results of the PF-modified test strip and the A channel conforms to y = 21.08 + 8.82x (R2 = 0.992), with a detection range of 0–0.8 mg L−1. The total detection time was reduced to 2.5 min. To evaluate accuracy in real matrices, influent, midstream, and effluent samples from Chengdu Living Water Park were analyzed, with UV-vis spectrophotometry used as the reference method. The test-strip results agreed well with UV-vis spectrophotometry, with relative errors below 5%. Overall, this study provides a portable, rapid, and accurate method for the detection of Mo (VI) in water, and has potential application prospects in the field of water environment detection in the future.