Potentiometric detection in UPLC as an easy alternative to determine cocaine in biological samples

Abstract

The analytical methods which are often used for the determination of cocaine in complex biological matrices are a prescreening immunoassay and confirmation by chromatography combined with mass spectrometry. We suggest an ultra-high-pressure liquid chromatography combined with a potentiometric detector, as a fast and practical method to detect and quantify cocaine in biological samples. An adsorption/desorption model was used to investigate the usefulness of the potentiometric detector to determine cocaine in complex matrices. Detection limits of 6.3 ng mL(-1) were obtained in plasma and urine, which is below the maximum residue limit (MRL) of 25 ng mL(-1). A set of seven plasma samples and 10 urine samples were classified identically by both methods as exceeding the MRL or being inferior to it. The results obtained with the UPLC/potentiometric detection method were compared with the results obtained with the UPLC/MS method for samples spiked with varying cocaine concentrations. The intraclass correlation coefficient was 0.997 for serum (n =7) and 0.977 for urine (n =8). As liquid chromatography is an established technique, and as potentiometry is very simple and cost-effective in terms of equipment, we believe that this method is potentially easy, inexpensive, fast and reliable.

Addressing the Detection of Ammonium Ion in Environmental Water Samples via Tandem Potentiometry–Ion Chromatography

“…The averaged calibration graph for the potentiometric cell ( n = 3 electrodes) revealed a slope of 59.5 ± 1.2 mV dec –1 within the LRR (from 3.0 × 10 –5 to 10 –3 NH 4 + activity) and a LOD of 2.5 × 10 –6 (Figure b). Pursuing the detection of lower NH 4 + levels, we investigated a transformation for the calibration graph via linearization of the entire logarithmic response . We used the linear fitting of the (10 E / S –1) magnitude (where E refers to the potential and S to the slope in the LRR when plotting the potential versus log a i ) against the NH 4 + concentration (Figure c), as previously reported for other chromatographic–potentiometric tandem systems …”

“…22 We used the linear fitting of the (10 E/S −1) magnitude (where E refers to the potential and S to the slope in the LRR when plotting the potential versus log a i ) against the NH 4 + concentration (Figure 4c), as previously reported for other chromatographic− potentiometric tandem systems. 22 Following this approach, an expanded LRR from 10 −6 to 10 −3 mol L −1 NH 4 + with a sensitivity of 76.6 ± 2.2 L mmol −1 (R 2 = 0.9986) was found. The LOD and LOQ were calculated as the concentration corresponding to a signal-to-noise ratio of three and ten times, respectively, yielding values of 3.0 × 10 −7 and 1.0 × 10 −6 mol L −1 NH 4 + .…”

A genosensor based on CPE for study the interaction between ketamine as an anesthesia drug with DNA

“…Ketamine abuse results a state of "dreamy intoxication", blurred vision and out of body experiences [7][8][9][10][11][12]. Recently, interaction of DNA and drugs has been a growing attractive topic in the electrochemical investigations [13][14][15][16]. For small molecules such as drugs, mechanism of interaction as well as evaluation of binding constant can be investigated by electrochemical studies.…”

A bimetallic nanocomposite electrode for direct and rapid biosensing of p53 DNA plasmid

“…[4][5][6] DNA hybridization biosensors, also known as genosensors, are analytical devices for the detection of specific DNA target sequences in solution upon hybridization of the targets with complementary probes immobilized on a solid substrate. 7 Nowadays, the technological platforms that provide biosensors of high sensitivity, selectivity and stability are therefore in high demand. [8][9][10] A sensor consists of two functional components: a recognition element for binding with target analytes and a transduction process to signal the binding event.…”