Determination of β-Agonists in Urine Samples at Low µg/kg Levels by Means of Pulsed Amperometric Detection at a Glassy Carbon Electrode Coupled with RP-LC

A method for the determination of β-agonists was developed by combining the separation of analytes through high-performance liquid chromatography, with a reversed-phase column, coupled to the pulsed amperometric detection at a glassy carbon electrode. Preliminary experiments, using cyclic voltammetry, allowed for an understanding of the electrochemical behavior of clenbuterol, fenoterol, and terbutaline. By analyzing the electrochemical response, the conditions for detecting the analytes and for cleaning the working electrode were identified. The proposed potential-time profile was designed to prevent contamination of the carbon electrode following consecutive analyses, so ensuring a reproducible and sensitive quantitative determination. The waveform electrochemical parameters, including detection and delay times, have been optimized in terms of sensitivity, detection limits, and long-term response stability. The chromatographic separation was carried out using a C8 column in isocratic mode, and a mixture of acetic acid and acetonitrile. The optimized experimental conditions were used for the analysis of standard solutions and real samples. Detection limits, lower than the maximum residue limit set for clenbuterol by European directives, were obtained for all β-agonists investigated. The method validation was performed by evaluating the linearity, selectivity, precision, and recovery. Calf urine samples were used to verify the applicability of the proposed method, analyzing both enriched and naturally contaminated urine samples.

Determination of myo-inositol content in milk by high performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD)

A method to determine inositol content in milk using high performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) was developed and validated. Samples were hydrolyzed with 10 mL HCl in a vacuum oven at 120oC, prolonging 6 h. Hydrolyzed samples were neutralized to a pH from 6 to 7.5 before analysing in an HPAEC-PAD system. The analytical program used Dionex CarboPacTM MA1 column (4 × 250 mm) with a mobile phase of a gradient program including NaOH 50 mM and NaOH 1M. The method was validated following AOAC guidelines: selectivity, linear range from 0,01 to 20 mg/L with a coefficient (R) 0.9998, the recoveries in the range of 99 - 102%, and repeatability with RSD under 1.8%. The limit of detection (LOD) and the limit of quantification (LOQ) of inositol were 0.047 µg/g and 0.155 µg/g, respectively. The method has been applied to determine of inositol content in milk samples with content ranging from 22.5 mg/100g to 64.7 mg/100g.

Ion Chromatography with Pulsed Amperometric Detection for Determining Cyanide in Urine and Meconium Samples

The parents’ addictions and eating habits have a significant influence on the child’s growth. The first stool of a newborn baby provides a large amount of information about xenobiotics transmitted by the mother’s body. The analytical technique used in the study is ion chromatography with pulsed amperometric detection (IC-PAD). The biological samples, which were obtained from women staying in a maternity ward and their partners, revealed cyanide concentrations in urine samples spanning 1.30–25.3 μg L−1. Meanwhile, the results of the meconium samples were in the range of 1.54 μg L−1 to 24.9 μg L−1. Under the optimized chromatographic conditions, the IC-PAD system exhibited satisfactory repeatability (R < 3%, n = 3) and good linearity in the range of 1–100 μg L−1. Thus, it proved to be an effective tool for monitoring trace cyanide concentration in a series of human body fluid matrices, including meconium. Based on the literature review, this is the first application of the IC-PAD analytical technique for the determination of cyanide ions in meconium samples.