A New Kinetic‐Mechanistic Approach Towards Spectrophotometric Bioanalysis of 2‐Phenylethylamine as a Sympathomimetic Agent Using Sodium Isopropyl Xanthate

ABSTRACT

2‐Phenylethylamine (2‐PEA), an aromatic biogenic amine, demonstrates significant physiological and toxicological effects on human health. A variety of conventional methods have been widely used for the determination of 2‐PEA. However, the necessity of complex sample preparation and high cost of instrumentation may pose challenges to their widespread application. The application of sodium isopropyl xanthate (SIPX) in spectrophotometric method was introduced a novel optical probe for simple, fast and cost‐effective detection of 2‐PEA. The distinct UV‐Vis spectrum of SIPX is changed in the presence of the target molecule (2‐PEA) which confirmed successful application of sensing strategy. Under optimal conditions, a linear range were achieved between 0.4 and 50 mM. The developed probe was characterized by dynamic light scattering (DLS) and zeta potential tests. The selectivity of prepared probe was validated by its minimal effects towards aliphatic amines, including histamine, cadaverine, 1,4‐diaminobutane, spermidine and ethylenediamine. Furthermore, the validation of reported analytical approach was examined in real human plasma. It can be deduced that SIPX as a novel optical probe could offer suitable, reliable, affordable and rapid sensing platform for detection of 2‐PEA in real samples. This study introduced significant innovations, including the development of a new organic optical probe for biogenic amine recognition in real samples, the establishment of a simple and rapid analytical workflow and the presentation of a novel spectrophotometric sensing platform offering selective detection of 2‐PEA. These advancements highlight clear technical benefits of this opto‐sensors for the specific recognition of biogenic amines compared with conventional analytical methods.

1. Introduction

2‐Phenylethylamine (2‐PEA), an aromatic biogenic amine with a low molecular weight, is generated by the enzymatic decarboxylation of L‐phenylalanine. The chemical structure of this neurotransmitter is similar to monoamine neurotransmitters, such as dopamine and serotonin. It is classified among trace amines, which are naturally synthesized in the vertebrate nervous system and by microbial activity during fermentation processes [1, 2]. As a neurotransmitter and neuromodulator, 2‐PEA influences dopaminergic, serotonergic and adrenergic pathways through trace amine‐associated receptors (TAARs). Through these interactions, it can modulate mood, alertness, energy and cognitive performance, which is why it is called the ‘endogenous amphetamine’ [3]. In addition, in the central nervous system, 2‐PEA promotes the release of catecholamines, such as dopamine and norepinephrine, which may result in antidepressant and psychostimulant effects [4, 5, 6, 7]. However, the level change of 2‐PEA causes several neurological and psychiatric disorders, including depression, schizophrenia, Parkinson's disease and attention‐deficit hyperactivity disorder (ADHD) [8, 9]. Along with its significant in the body, 2‐PEA is found in different fermented foods (cheese, meat, fish, wine and chocolate) as production of microbial decarboxylation [10]. Its concentration is influenced by several factors, including pH, the presence of precursor amino acids, fermentation duration and the microbial species involved [11, 12]. Therefore, there is an urgent need in development of simple, rapid and sensitive method for 2‐PEA quantification.

Although conventional analytical methods, such as mass spectrometry [13], high‐performance liquid chromatography (HPLC) [14] and capillary electrophoresis [15], are capable of detecting 2‐PEA, significant drawbacks limit their widespread application. These include extended analysis times, the utilization of expensive and hazardous reagents, complex sample preparation and the need for highly skilled operators. Therefore, in recent years, researchers have increasingly focused on developing analytical methods that possess several advantages, including simplicity, rapidness and affordability, particularly UV‐Vis detection method [16, 17].

In this context, the design and selection of an efficient optical probe play a crucial role in determining sensitivity and selectivity. Among various organic and organosulphur reagents, sodium isopropyl xanthate (SIPX) has attracted attention as a promising light‐responsive compound. SIPX is an organosulphur salt (C₄H₇NaOS₂) characterized by strong electronic transitions associated with sulphur‐containing functional groups, leading to distinct absorption peaks in the ultraviolet region. It exhibits excellent solubility and chemical stability within a near‐neutral pH range (7–8), and its UV‐Vis spectrum features two characteristic absorption bands at approximately 231 and 304 nm, which are attributed to n→σ* and n→π* transitions within the xanthate moiety. The strong and well‐defined optical response of SIPX, combined with its stability in aqueous media and ease of use, make it a suitable candidate for optical probe development [18, 19, 20, 21]. In this study, we explore the interaction between SIPX as an optical probe and 2‐PEA as the target analyte under physiological conditions, using UV‐Vis spectrophotometry. The sensing mechanism is based on spectral changes arising from molecular interactions between SIPX and 2‐PEA, which enable direct quantification of the analyte. To the best of our knowledge, this is the first report employing SIPX as a light‐active probe for the sensitive and rapid detection of 2‐PEA in biological and real‐world samples.

2. Experimental

2.1. Chemicals and Materials

Histamine dihydrochloride (HDC), cadaverine dihydrochloride (CD), 1,4‐diaminobutane (DAB), 2‐PEA, spermidine trihydrochloride (STC) and ethylenediamine (EDA) were purchased from Sigma‐Aldrich (Oakville, Canada). SIPX was purchased from Copolymer Inc. (Isfahan Iran). In addition, acetonitrile was bought from Merck Germany and human plasma samples were found from the Iranian Blood Transfusion Research Center (Tabriz, Iran). Distilled water purchased from Shahid Ghazi Pharmaceutical Co. (Tabriz, Iran) was used for the preparation of the solutions. All other chemical materials were of reagent grade and used as received.

2.2. Instrumentation

Spectrophotometric studies were conducted using a Shimadzu UV‐1800 UV‐Vis spectrophotometer. Particle size distribution analysis and zeta potential measurements of the synthesized SIPX were performed using a Zetasizer Ver (Model MAL1032660, Malvern Instruments Ltd., UK). Centrifugation processes were carried out using a laboratory centrifuge operating at appropriate speed and duration according to the experimental requirements.

2.3. Real Sample Preparation

For the real sample preparation, the mixing of human frozen plasma and acetonitrile (1:1 ratio) was centrifuged at 8000 rpm for 10 min. Following centrifugation, the supernatant (clear upper layer) was carefully collected and used for subsequent analysis.

3. Results and Discussion

3.1. Discriminative Detection of 2‐PEA

In order to demonstrate the selectivity of sensing system for 2‐PEA, we assessed its response to potential interferences, including HDC, CD, DAB, STC and EDA under optimal conditions. The optical response of each interference at 30 mM, was recorded across a wavelength range of 200 to 800 nm. As shown in Figure 1A,B, when the 2‐PEA was added to the system, absorption wavelength of SIPX changed by emerging of a new intense peak at 256 nm (see red circle in Figure 1A). The comparison of UV‐Vis absorption response with other tested amines demonstrated that only 2‐PEA changed the absorption spectrum at 256 nm. The aliphatic amines, which lack aromatic systems, produced no significant changes in wavelength or absorbance.

FIGURE 1.

FIGURE 1 (A) The UV‐Vis spectrums of SIPX, SIPX/HDC (30 nM), SIPX/CD (30 mM), SIPX/ DAB (30 mM), SIPX/STC(30 mM), SIPX/2‐PEA (30 mM) and SIPX/EDA (30 mM) at 0 min incubation time and 1:2 v/v ratio. (B) UV‐Vis absorption response versus type of reagents.

The UV‐Vis spectrum of the SIPX/2‐PEA mixture (200–800 nm) exhibited a new absorption band at 256 nm, corroborating the formation of a charge‐transfer complex. The interaction mechanism between SIPX and 2‐PEA involves a combination of chemical and physical processes, including surface adsorption, coordination bonding and plasmon‐induced charge transfer. The primary amine group (─NH₂) and aromatic phenyl ring of 2‐PEA both participate in these interactions:

Amine coordination: The lone pair of electrons on the nitrogen atom of 2‐PEA can coordinate with sulphur atoms on the SIPX surface, forming SIPX─N bonds.

π–metal interaction: The delocalized π‐electrons of the phenyl ring may weakly interact with SIPX, although this contribution is secondary to the amine coordination mechanism.

Thus, the proposed adsorption process can be summarized as follows:

$$\begin{array}{cc}& 2-\text{PEA}+\text{SIPX}(\text{surface})\hfill \\ & \to \text{adsorbed}\text{complex}(\text{SIPX}\text{--}{\text{NH}}_2\text{--}{\text{CH}}_2\text{--}{\text{CH}}_2\text{--}\text{Ph})\hfill \end{array}$$

SIPX supports localized surface plasmon resonance (LSPR), which is highly sensitive to changes in the local dielectric environment. Upon adsorption of 2‐PEA, the local refractive index changes, leading to a red shift of the LSPR band. In addition, two potential charge‐transfer pathways may occur: (i) photo‐excited electrons may transfer from SIPX to the LUMO of 2‐PEA, or (ii) at higher electron densities (under mildly basic conditions), electrons from 2‐PEA may transfer to SIPX, partially reducing surface xanthate ions. Following interaction with 2‐PEA, SIPX may undergo morphological transformations, particularly under light exposure or oxidative conditions. Moreover, 2‐PEA can act as a bridging molecule, promoting inter‐particle aggregation through hydrogen bonding or π–π stacking between SIPX entities. Zeta potential studies demonstrated that SIPX/amine interactions lead to a reduction in surface charge, confirming structural rearrangements within SIPX. When SIPX is mixed with amine solutions, the surface charge magnitude decreases markedly, whereas in the absence of interaction, minimal change is observed. Collectively, these results indicate that the reaction between SIPX and 2‐PEA likely proceeds via the formation of a xanthate–amine complex, in which the C═S group of SIPX interacts with the NH₂ group of aromatic 2‐PEA, inducing a modification of the electronic structure of SIPX and the appearance of the new absorption band at 256 nm. In summary, we have a primary aryl–alkyl amine (the benzene‐containing alkylamine in the first picture) and sodium O‐isopropyl xanthate (the second picture, iPrO─C(═S)–S⁻ Na⁺). A proposed chemically sensible reaction between those reactants is formation of the corresponding dithiocarbamate (as its sodium salt) by nucleophilic attack of the amine on the xanthate's thiocarbonyl carbon with displacement of isopropoxide. For this purpose, amines attack the thiocarbonyl carbon of O‐alkyl xanthates to give a tetrahedral intermediate that collapses with loss of the alkoxide (iPrO⁻ → iPrOH) producing the N‐substituted dithiocarbamate anion (Na⁺ salt). Therefore, below reaction id possible:

$$\begin{array}{cc}& \text{Ph}-\left(\mathrm{C}{\mathrm{H}}_2\right)\mathrm{n}-\mathrm{N}{\mathrm{H}}_2+\mathrm{N}{\mathrm{a}}^{\mathrm{+}}{\left[\text{iPrO}-\mathrm{C}\left(=\mathrm{S}\right)-\mathrm{S}\right]}^{-}\hfill \\ & \to \mathrm{N}{\mathrm{a}}^{\mathrm{+}}{\left[\text{Ph}-\left(\mathrm{C}{\mathrm{H}}_2\right)\mathrm{n}-\text{NH}-\mathrm{C}\left(=\mathrm{S}\right)-\mathrm{S}\right]}^{-}+\text{iPrOH}\hfill \end{array}$$

Which the primary amine attacks the C═S centre of the xanthate, displaces isopropoxide and the product is the sodium N‐alkyl dithiocarbamate (the anion bound to Na⁺). Proton transfer converts the transient ammonium intermediate into the neutral N–H dithiocarbamate which is present as its sodium salt under the basic conditions. FTIIR spectra confirm these results (Figure 2).

FIGURE 2.

FTIR spectra of SIPX after its interaction with 2PEA (B).

3.2. Zeta and DLS Characterization of SIPX

The DLS and zeta potential results were used for validation of the spectrophotometric findings (Figures 3 and 4). The zeta potential analysis reveals a clear shift in the surface charge characteristics of SIPX after incubation and interaction with 2‐PEA. Prior to incubation, the species exhibit a moderately negative zeta potential (−15.1 mV) (Figure 3A), which reflects a reasonably stable colloidal system in which electrostatic repulsion limits particle–particle interactions and minimizes aggregation. This negative charge environment is consistent with the uniform particle distribution observed in the corresponding DLS results. Following incubation with 2‐PEA, however, the zeta potential (+0.173 mV) shifts sharply toward neutrality (Figure 2B), indicating substantial charge neutralization at the particle surface. Such a pronounced reduction in electrostatic repulsion suggests strong molecular interactions between SIPX and the analyte, likely involving surface binding or rearrangement of functional groups. The near‐neutral zeta potential further implies decreased colloidal stability, which aligns with the increased polydispersity and changes in particle size distribution detected by DLS. Overall, this shift in zeta potential provides compelling evidence for interaction‐induced modification and reorganization of SIPX in the presence of 2‐PEA.

FIGURE 3.

Zeta potential analysis of the SIPX before (A) and after (B) interaction with 2‐PEA in 0 min of incubation time.

FIGURE 4.

DLS analysis of the SIPX before (A) and after (B) interaction with 2‐PEA in 0 min of incubation time.

Dynamic light scattering (DLS) analysis of SIPX reveals notable changes before and after incubation with 2‐PEA (Figure 4). Prior to incubation, the size of particles are primarily in the 65–115 nm range, with only a minor fraction (∼3%) appearing at much larger sizes (∼5560 nm), likely representing limited aggregation. The polydispersity index (PDI = 0.390) indicates a relatively uniform distribution, and number‐ and volume‐based distributions confirm that most particles remain within the nanoscale range, suggesting that the system is stable and well‐dispersed (Figure 3A). Upon incubation with 2‐PEA, the particle size distribution changes markedly: the Z‐average increases to ∼723 nm and the PDI rises to 0.768, reflecting a significant loss of uniformity and increased dispersity. The intensity distribution shows two distinct populations: a portion of small particles (∼105 nm) persists, while a substantial fraction (∼33.7% intensity) appears at extremely small sizes (∼2.3 nm) (Figure 3B). These observations indicate that interactions with 2‐PEA induce partial disassembly or reorganization of SIPX, altering both their size and distribution. Overall, the DLS data demonstrate that the presence of the analyte strongly affects the structural stability and aggregation behaviour of the species.

Their possible interaction was illustrated in Scheme 1. As can be seen in Scheme 1, the lone pair on the amine nitrogen attacks the thiocarbonyl carbon (C═S) of the xanthate anion (iPrO─C(═S)─S⁻). This forms a tetrahedral intermediate. Next, the O‐isopropyl group departs as isopropoxide (iPrO⁻) while the C─N bond is retained, yielding an N‐protonated dithiocarbamate (or, equivalently, the neutral N─H dithiocarbamate plus base/proton transfers). Because the starting xanthate carried Na⁺ and the leaving alkoxide can pick up a proton, the net by‐product is isopropanol (iPrOH) under protic workup. Therefore, under reaction conditions (neutral to mildly basic), the final stable species is the sodium salt of the dithiocarbamate anion. It is important to point out that, the dithiocarbamate anion is resonance‐stabilized:

$$\begin{array}{cc}& \mathrm{R}-\text{NH}-\mathrm{C}(=\mathrm{S})-{\mathrm{S}}^{-}\leftrightarrow \mathrm{R}-{\mathrm{N}}^{+}\mathrm{H}=\mathrm{C}-\mathrm{S}-{\mathrm{S}}^{-}\hfill \\ & \left(\text{delocalization}\text{over}\mathrm{C}=\mathrm{S}\text{and}\mathrm{S}\right)\hfill \end{array}$$

SCHEME 1.

Possible reaction mechanism of 2‐PEA with SIPX.

This resonance explains why the anionic product is relatively stable as its sodium salt which confirmed by previous reports [22, 23].

3.3. Analytical Performance

The application of the developed optical probe for detection of 2‐PEA with different concentrations, including 0.4, 0.6, 0.8, 1, 2, 4, 6, 8, 10, 20, 30, 40, 50, 100 mM, was examined at different incubation times (Figure 5A–C). In detail, the analytical performance of the sensing assay was measured at various incubation times of 0, 60 and 120 min (Table 1). At 0 min, the calibration curve demonstrated a low slope but high R ² value. This show system was analytically consistent at this early stage. After 60 min of incubation, the analytical performance of sensing system was improved due to an increasing slop of the calibration curve. However, the decrease in R ² after 0 min indicated the instability or incomplete signal uniformity. At 120 min, the system transitions into the stabilization or saturation phase, where the slope dropped and R ² value recovered to 0.9737. This indicates that the absorbance at 256 nm was no longer responsive to the target concentration in this stage. These finding show that, the time‐dependent SIPX‐2‐PEA interaction evolves from rapid initiation (0 min) to maximum kinetic activity (60 min), followed by stabilization and charge‐transfer complex formation (120 min).

FIGURE 5.

UV‐Vis spectra of different concentration of 2‐PEA in the presence of SIPX at different incubation times (A) 0, (B) 60 and (C) 120 min. (D–F) Calibration curves.

TABLE 1.

The analytical parameters of the developed optical sensor at different incubation times (0, 60 and 120 min).

Incubation time (min)	Concentration range (mM)	Regression equation	R 2
0	0.4–50	0.0075x + 0.5252	0.9946
60	0.8–6	0.0395x + 0.4347	0.9601
120	4–40	0.0011x + 0.6154	0.9737

The effect of analyte concentration was evaluated at three different incubation times (0, 60 and 120 min) to determine the most appropriate concentration range for reliable quantification of 2‐PEA. According to the obtained calibration parameters (Figure 6 and Table 1), the system exhibited the widest linear dynamic range at time 0 (0.4–50 nM) with a high correlation coefficient (R ² = 0.9946), indicating fast optical interaction between SIPX and 2‐PEA without the need for prolonged incubation. Although the slope of the regression increased markedly after 60 min (0.0395), suggesting higher analytical sensitivity, the linear range became significantly narrower (0.8–6 mM) and the R ² value decreased (0.9601), limiting its applicability for samples with unknown or wide concentration ranges. After 120 min, the analytical performance declined further, as shown by the minimal slope (0.0011) and a reduced linear interval (4–40 mM), confirming a loss of signal responsiveness over extended incubation. Overall, the concentration range of 0.4–50 mM at zero incubation time provided the most robust and practical analytical window, maintaining excellent linearity, acceptable sensitivity and rapid response. These findings demonstrate that the SIPX‐based sensing system performs optimally without incubation, making it suitable for fast and straightforward quantification of 2‐PEA.

FIGURE 6.

Calibration curves of peak intensity versus concentration of 2‐PEA at different incubation times (0, 60 and 120 min).

3.4. Reproducibility Analysis of the Reported Probe

The stability of the reported optical probe SIPX was evaluated by measuring the UV‐Vis absorbance of its solutions over the three days (Figure 7). For this purpose, different concentrations of target, including low (0.4 mM), intermediate (2 mM) and high (10 mM) were prepared to assess the stability based on different concentration. The absorbance values for the 10 mM solution were 0.8421, 0.7146 and 0.7182 a.u on Days 1, 2 and 3, respectively, with standard deviation (SD) of 0.07257. The 2 nM demonstrated absorbances of 0.6962, 0.6423 and 0.6324 a.u, from Day 1 to 3, (SD of 0.03434). The absorbance values were recorded 0.5650, 0.5635 and 0.4705 a.u for the concentration of 0.4 mM. In addition, the result indicated the SD of 0.05413 for this concentration. The absorbance of data collected over the testing period showed a decreasing trend across all tested concentrations. For the solution at 10 mM, the absorbances recorded from Day 1 to 3 were 0.8421, 0.7146 and 0.7182, representing an approximate 14.7% drop from Day 1 to 3, with a mean SD for this concentration calculated at 0.07257. At the intermediate concentration of 2 mM, the absorbances were observed as 0.6962, 0.6423 and 0.6324 a.u, indicating a smaller drop of about 9.16%. Notably, this concentration registered the lowest inter‐day variability with a SD of 0.03434. Finally, the 0.4 mM concentration experienced a greater decrease, with absorbance values dropping from 0.5650 (Day 1) to 0.4705 (Day 3) (an approximate 16.7% loss), yielding a SD of 0.05413. The above results indicate that the stability of the SIPX optical probe is concentration dependent. The overall decrease in absorbance over the three days generally suggests slow degradation or physical instability (such as aggregation or precipitation) of the active probe species under the storage conditions, which must be accounted for when quantitatively interpreting the identification of 2‐PEA. In terms of measurement reproducibility, the 2 mM concentration demonstrated the best consistency across inter‐day replicates, showing the lowest SD (0.03434). This suggests this concentration may be near an optimal point for molecular interactions or a stable saturation point. Conversely, the lowest (0.4 mM) and highest (10 mM) concentrations showed higher sensitivity to environmental factors or degradation processes, experiencing the largest losses in absorbance (16.7% and 14.7%, respectively). Therefore, for future experiments requiring accurate and reproducible absorbance measurements, the 2 mM SIPX concentration is proposed as the optimal operating point.

FIGURE 7.

UV‐Vis spectra and corresponding histograms of SIPX+2‐PEA solutions recorded over three days at concentrations of 0.4, 2 and 10 mM. All samples show a gradual decrease in absorbance, indicating concentration‐dependent stability of the probe. The 2 mM sample exhibits the lowest inter‐day variation and best reproducibility, while the 0.4 and 10 mM samples show greater signal loss over time.

To evaluate the intra‐day, UV‐Vis absorbance measurements were performed at three different time (0, 60 and 120 min) for three analyte concentrations (0.4, 2 and 10 mM) (Figure 8). For each concentration, the peak intensity was monitored to assess short‐term stability. The analysis of the absorbance data clearly demonstrated that the varying analyte concentrations had a profound effect on the long‐term signal stability of the probe. At an analyte concentration of 0.4 mM, the SIPX probe exhibited maximum stability; this condition recorded only a marginal and acceptable signal decrease of 3.25% over the 120‐min interval. This superior signal constancy, coupled with the lowest overall SD (0.0648), confirms that the interaction between the probe and the analyte at this level results in the most stable and lowest‐noise measurement system. Conversely, increasing the analyte concentration to 2 and 10 mM induced severe instability. The 2 nM sample experienced a sharp signal increase of 68.69%, while the 10 mM sample showed significant fluctuation with a 48.38% increase. These drastic changes suggest that at these higher analyte loads, secondary reactions or physical changes, such as aggregation or non‐linear light absorption, may be occurring, leading to artificially inflated absorbance readings and compromising the reliability of the 2‐PEA detection. Given that the SIPX probe concentration was constant, the results decisively confirm that 0.4 mM of 2‐PEA is the ideal operating concentration for this time‐dependent assay, as it provides the best signal stability (minimal drift) and the highest measurement precision (lowest SD).

FIGURE 8.

UV‐Vis spectra of the interaction SIPX with 2‐PEA at different concentrations and incubation times (0, 60 and 120 min) and related histogram.

3.5. Real Sample Analysis

To further evaluate the analytical performance of the optical probe SIPX, detection of 2‐PEA was conducted under real biological conditions. To this aim, the potential interference of plasma compounds on the optical response was examined in a series of samples containing various concentrations of 2‐PEA (0.4–50 mM). The UV‐Vis absorbance of each sample was measured over the wavelength range of 200–800 nm, as illustrated in Figure 9, plasma exhibited strong absorbance in UV region owing to the presence of the proteins and metabolite content. While there was background signal in all samples, the change in optical signal was increased toward 2‐PEA (Figure 8). The calibration curve of absorbance versus 2‐PEA concentration was plotted and the linear regression equation obtained was:

$$\text{Abs}(\mathrm{a}.\mathrm{u})=0.029{\mathrm{C}}_{(2-PEA)}+0.4846,(R^2=0.9978)$$

FIGURE 9.

(A) UV‐Vis absorption spectra to show the effect of different concentrations of 2‐PEA on optical probe SIPX in the presence of human plasma. (B) Related corresponding calibration plot.

The high correlation coefficient (R ² = 0.9978) confirms that the sensing system presents a consistent response.

Reviewing and comparing previous studies on the detection and quantification of 2‐PEA is essential for understanding the development of analytical approaches, identifying their limitations and positioning the current work within the broader context of the field. Table 2 is presented to summarize the various analytical methods that have been developed for 2‐PEA. By comparing the linear ranges, limits of detection and sample types used in previous studies, the strengths and limitations of each method can be highlighted. This overview allows for the evaluation of the current work in relation to existing methods and emphasizes its potential advantages or innovations.

TABLE 2.

Comparison the analytical performance of various developed biosensors for detection of 2‐PEA.

Method	Type of probe or utilized material	Linear range	LOD/LOQ/LLOD/LLOQ	Sample type	Ref.
Ion chromatography (IC)	—	0.5–100 mg/L	0.02 mg/L	Cheese, processed meat, fish	[24]
Ion chromatography (cation exchange column) coupled with Tandem MS	—	10 µg/L–10 mg/L	46 µg/L	Cheese	[25]
Liquid chromatography (LC–MS/MS)	Magnetic Molecularly Imprinted Polymer (MMIP) as selective extraction probe	2.4–8.7 µg/g	8.7 µg/g	Cocoa powder and chocolate	[26]
Electrochemical/potentiometric method	t‐Butyl calix[8]arene/Ag/CuO composite‐based potentiometric sensor	1 × 10−5 – 1 × 10−2 mol/L	9.77 × 10−6 mol/L	Dietary supplements	[10]
Biochemical enzymatic method	Amine oxidase enzyme (oxidase activity)	2.5–120 µM	2.3 µM	Commercial cheese	[27]
Fluorescence spectroscopy (on–off–on mode)	Host—Guest supramolecular probe with Cucurbit[8]uril	0.5–3 × 10−4 M (aqueous), 0.4–1.6 × 10−4 M (urine)	3.08 µM (aqueous), 1.34 µM (urine)	Aqueous and human urine samples	[28]
HPLC with on‐column fluorescence derivatization	—	0.5–15 mg/L	300 µg/L	Wine	[29]
HPLC with pre‐column dansylation	—	0.025–3 mg/L	0.025 mg/L	Wines and beers	[30]
Modified liquid–liquid extraction followed by HPLC	—	0.1–50 mg/L	0.001–0.050 mg/L	Wine	[31]
High‐performance liquid chromatography (HPLC)	—	0.001–20 mg/L	0.0628 µg/L	Human serum	[32]
Ultra‐high‐performance supercritical fluid chromatography (UHPSFC–MS)	—	0.25–5 µg/mL	0.15 µg/mL	Aquatic products	[33]
UV‐Vis spectrophotometry	SIPX	0.4–50 mM	0.4 mM	Human plasma	This work

In this study, a simple and rapid optical sensing method using SIPX developed for the detection of 2‐PEA. Our platform exhibits an excellent sensitivity and wide linear range, highlighting its application for real sample analysis. In terms of linear range and sensitivity, our method covers 0.4–50 mM with a limit of detection (LOD) of 0.4 mM, making it suitable for biological samples such as human plasma. In addition, an acceptable selectivity of the SIPX probe toward 2‐PEA. This is an advantage over some general chromatography or extraction methods, which may need complete separation to avoid interference from other compounds. Advantages of our method include fast analysis, simplicity, low cost and applicability to real human samples. In addition, the optical detection approach allows measurement without the need for specialized or advanced instruments. Limitations include lower sensitivity compared to advanced HPLC and LC–MS/MS methods. For samples with very low 2‐PEA concentrations, more sensitive methods may be preferred. Furthermore, the millimolar range of detection may limit applicability in samples with extremely low analyte concentrations. Overall, the SIPX‐based method provides a suitable, rapid and economical approach for monitoring 2‐PEA in biological and environmental samples and can serve as a simpler alternative to more complex techniques, especially when advanced instruments are not available. In summary, a simple and rapid optical sensing method using SIPX developed for the detection of 2‐PEA. The comparison of analytical performance of the designed sensing approaches with other methods demonstrated that. Our platform exhibits an excellent sensitivity and wide linear range, highlighting its application for real sample analysis. In addition, an acceptable selectivity of the SIPX probe toward 2‐PEA, making its feasible in real samples with several inter‐references.

4. Conclusion

In this study, the optical interaction between 2‐PEA and SIPX was investigated using UV‐Vis spectrophotometry. The results revealed that the SIPX probe exhibited no significant response toward aliphatic amines, while a distinct and measurable spectral signal was observed in the presence of 2‐PEA, confirming the critical role of the aromatic structure in the recognition process. The concentration‐dependent studies demonstrated a linear relationship between absorbance intensity and analyte concentration within the range of 0.4–50 mM, with a low limit of quantification of 0.4 mM. In addition, stability evaluation confirmed the acceptable reproducibility and robustness of the system. Furthermore, the reported sensor was able to successfully detect the 2‐PEA in complex biological samples. Although this sensing approach provides an efficient monitoring method of 2‐PEA based on SIPX, future perspectives can focus on the application of this probe in wearable sensors for on‐site detection of 2‐PEA. In addition, the integration of the developed sensor with smart gadgets like smartphones can boost analysis of data. Furthermore, the implementation of the probe in the lateral flow assays can be considered another novel idea for portable detection of 2‐PEA. Along with portability, the combination of the biological elements, such as aptamers, peptides, antibodies and enzymes, can improve the selectivity of the reported fluorescence sensor. Moreover, the findings of this work underline several key innovations, including the introduction of a new organic optical probe tailored for selective identification of aromatic biogenic amines, the establishment of a rapid and user‐friendly analytical strategy and the presentation of a novel spectrophotometric sensing platform with superior operational simplicity and affordability relative to traditional instrumental methods. These innovations collectively position the SIPX‐based sensor as a promising next‐generation analytical tool for real‐sample detection of 2‐PEA.

Author Contributions

Fatemeh Nami: writing – original draft, methodology, investigation. Houman Kholafazad: writing – original draft, methodology. Mohammad Hasanzadeh: conceptualization, supervision, writing – review and editing, validation, formal analysis, methodology. Nasrin Shadjou: writing – review and editing, project administration.

Conflicts of Interest

The authors declare no conflicts of interest.

Data Availability Statement

The authors have nothing to report.