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Diquat (DQ) and paraquat (PQ) residues in food are potential hazards to consumers' health. Point-of-care testing (POCT) of them remains challenging. Based on surface-enhanced Raman spectroscopy (SERS) technology, we developed a POCT strategy for DQ and PQ on apple surface and in apple juice. A point-of-use composite was fabricated using a piece of porous melamine sponge (MS) modified with silver nanoflowers (AgNFs), combining the specificity of the SERS fingerprint and the excellent adsorption capacity of MS. Using this dual-functional AgNFs@MS, the on-site determination of the DQ and PQ residues was completed within 3 min without pretreatment. Clear trends were observed between SERS intensity and logarithmic concentrations, with r values from 0.962 to 0.984. The limit of detection of DQ and PQ were 0.14-0.70 ppb in apple juice and on apple surface. This study provides a new point-of-use alternative for rapidly detecting DQ and PQ residues in nonlaboratory settings., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Data Availability. Data will be made available on request., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Poisoning with diquat (DQ) and paraquat (PQ) herbicides has been a public health problem. Unfortunately, rapid detection in biofluids remains challenging. Herein, a hyphenated approach of electro-enhanced adsorption, solid-phase microextraction, and surface-enhanced Raman spectroscopy (EE−SPME−SERS) was exploited for rapid and sensitive in situ analysis of DQ and PQ in human urine and plasma. A porous Ag fiber with an Au layer (p-Ag/Au fiber) was fabricated with multi-functions (SERS substrate, SPME sorbent, and working electrode). Clear trends could be observed between signal intensity and concentration of DQ or PQ with high reproducibility. The method detection limits (MDLs) calculated from the characteristic peak of DQ were 0.064 ppb and 0.65 ppb in urine and plasma, respectively. Corresponding MDLs for DQ and PQ in urine and plasma were 0.036 ppb and 0.35 ppb, respectively. The whole process of "extracting and detecting" was completed within 4 min with satisfactory recoveries. Notably, the EE−SPME−SERS technique could easily realize in situ analysis of DQ and PQ in biofluids with good selectivity, which is practical in clinical diagnosis. This EE−SPME−SERS method provides a potential avenue for efficient pretreatment and in situ poison detection in biological samples. [Display omitted] • Ultrafast EE-SPME-SERS method for in situ analyzing diquat and paraquat in biofluids. • Low detection limits ranging from 0.034 ppb to 0.65 ppb. • Good selectivity based on electrochemical adsorption. • p-Ag/Au fiber to realize hyphenation of enrichment, extraction, and SERS detection. [ABSTRACT FROM AUTHOR]

Rapid detection of diquat (DQ) is essential in clinical diagnosis and rescue. Here, we developed a fast, simple-yet-practical detection strategy for the reliable identification and quantification of DQ in biological fluids. Based on surface-enhanced Raman spectroscopy (SERS), point-of-care detection was realized under the acidic condition with gold nanoparticles as the substrate. Under optimal experimental conditions, the detection limits of the strategy were 17.5 ppb and 1.99 ppm in human urine and gastric juice, respectively. High specificity and selectivity of the SERS strategy were demonstrated using common pesticides and coexisting biological substances. The method was also used to detect biofluids from 5 patients and urine samples from 10 healthy volunteers. The results were in high agreement with spectrophotometric and clinical liquid chromatography-mass spectrometry methods. The volume of urine samples required for this technique is merely 20 μL, and no preparation of the samples is required. Compared to traditional methods used in clinical settings, SERS-based methods are capable of real-time measurements that accurately provide rapid detection and response in non-laboratory settings, with great potential for on-site and point-of-care testing. [ABSTRACT FROM AUTHOR]