RESUMEN
A mechanically robust in-tube stainless steel microneedle solid phase microextraction (SPME) platform for dual electrochemical and chromatographic detection has been demonstrated. The SPME microneedle was fabricated by layer-by-layer (LbL) in-tube coating, consisting of carbon nanotube (CNT)/cellulose nanocrystal (CNC) film layered with an electrically conductive polyaniline (PANI) hydrogel layer (PANI@CNT/CNC SPME microneedle (MN)). The PANI@CNT/CNC SPME MN showed effective analysis of caffeine by GC-MS with an LOD of 26 mg/L and excellent precision across the dynamic range. Additionally, the PANI@CNT/CNC SPME MN demonstrated a 67% increase in sensitivity compared to a commercial SPME fiber, while being highly robust for repeated use without loss in performance. For electrochemical detection, the PANI@CNT/CNC SPME MN showed excellent performance for the detection of 3-caffeoylquinic acid (3-CQA). The dynamic range and limits of detection (LOD) for 3-CQA analysis were 75-448 mg/L and 11 mg/L, respectively. The PANI@CNT/CNC SPME MN was demonstrated to accurately determine the caffeine content and 3-CQA in tea samples and dark roast coffee, respectively. The PANI@CNT/CNC SPME MN was used for semiquantitative antioxidant determination and composition analysis in kiwi fruit using electrochemistry and SPME-coupled GC-MS, respectively.
RESUMEN
Aflatoxin B1 (AFB1) has been identified as one of the most potent naturally occurring carcinogens with high toxicity. The maximum permissible levels of total aflatoxin contamination in food products are limited to 10-15 µg kg-1, as established by the Codex Alimentarius Commission. The widespread occurrence of AFB1 in the food chain identifies them as significant agricultural contaminants of global concern. We herewith demonstrate a molecularly imprinted polymer (MIP)-enabled stainless steel hypodermic needle sensor for sensitive electrochemical detection of AFB1. The stainless-steel hypodermic needle sensor was fabricated using a layer by layer (LbL) film coating comprising multiwalled carbon nanotubes (MWCNTs), cellulose nanocrystals (CNC), and an AFB1 imprinted polyaniline (PANI) biomimetic receptor film. The PANI@MIP/CNC-CNT hypodermic needlesensor showed excellent electrochemical capacitance response (â¼10 min) to AFB1 with a linear range of 0-25 nM and a limit of detection (LOD) of 3 nM. Demonstrating good reusability, a single PANI@MIP/CNC-CNT hypodermic needle AFB1 sensor could be reused up to 7 times with a 2.8% relative standard deviation (% RSD) in the sensor's capacitive response. The PANI@MIP/CNC-CNT hypodermic needle sensor was effective in the detection of AFB1 spiked in milk.