Simultaneous determination of three chloroacetic acids, three herbicides, and 12 anions in water by ion chromatography

Sample preparation for suspect screening of persistent, mobile and toxic substances and their phase II metabolites in human urine by mixed-mode liquid chromatography

Persistent, mobile and toxic substances have drawn attention nowadays due to their particular properties, but they are overlooked in human monitorization works, limiting the knowledge of the human exposome. In that sense, human urine is an interesting matrix since not only parent compounds are eliminated, but also their phase II metabolites that could act as biomarkers. In this work, 11 sample preparation procedures involving preconcentration were tested to ensure maximum analytical coverage in human urine using mixed-mode liquid chromatography coupled with high-resolution tandem mass spectrometry. The optimized procedure consisted of a combination of solid-phase extraction and salt-assisted liquid-liquid extraction and it was employed for suspect screening. Additionally, a non-discriminatory dilute-and-shoot approach was also evaluated. After evaluating the workflow in terms of limits of identification and type II errors (i.e., false negatives), a pooled urine sample was analysed. From a list of 1450 suspects and in-silico simulated 1568 phase II metabolites (i.e. sulphates, glucuronides, and glycines), 44 and 14 substances were annotated, respectively. Most of the screened suspects were diverse industrial chemicals, but biocides, natural products and pharmaceuticals were also detected. Lastly, the complementarity of the sample preparation procedures, columns, and analysis conditions was assessed. As a result, dilute-and-shoot and the Acclaim Trinity P1 column at pH = 3 (positive ionization) and pH = 7 (negative ionization) allowed the maximum coverage since almost 70 % of the total suspects could be screened using those conditions.

Sensitive SERS assay for glyphosate based on the prevention of l-cysteine inhibition of a Au-Pt nanozyme

Herein, an indirect SERS sensing assay was developed for the determination of glyphosate (Gly) in tap water. The mechanism of detection was based on relieving the inhibitory effect of l-cysteine (l-cys) on a Au-Pt nanozyme by combining Gly with l-cys through divalent copper ions (Cu2+). In this method, a novel nano-chain-like Au-Ag composite with good repeatability was successfully fabricated to detect SERS signals of oxTMB without disturbing TMB Raman signals. Under optimal conditions, the SERS signal intensity of oxTMB (at 1605 cm-1) was proportional to the concentration of Gly. The results showed a good linear response over the concentration ranges of 10 μg L-1 to 1000 mg L-1. The limit of detection and limit of quantitation of Gly were found to be 5 μg L-1 and 10 μg L-1, respectively. In addition, good anti-interference ability against interfering cations and structural analogues deserves to be mentioned. This SERS assay can be used for detection of Gly in tap water that can meet the needs of practical detection.

Validation of a simple ion chromatography method for simultaneous determination of glyphosate, aminomethylphosphonic acid and ions of Public Health concern in water intended for human consumption

The herbicide glyphosate and its main metabolite aminomethylphosphonic acid (AMPA) are generally studied in environmental samples in the investigation of contamination of soil, plants, water and food. Many analytical methods are based on liquid chromatography or high-performance liquid chromatography, with pre-column or post-column derivatization; in addition, the chromatograph can be coupled to mass spectrometers for detection and quantification. Gas chromatography and spectroscopic and electrochemical methods have also been used. In this work, a simple low-cost method is presented for the analysis of water intended for human consumption with the quantification not only of glyphosate and AMPA, but also of other ions of interest to public health (fluoride, chlorite, bromate, chloride, nitrite, nitrate, sulfate and phosphate). Based on ion chromatography with conductivity detection (chemical suppression of eluent conductivity), the key point in this method is the use of gradient elution with two eluents of different pH and ionic strength, not requiring derivatization. There is no interference from the other ions at higher concentrations. The detection limits obtained for glyphosate and AMPA were 15 μg L-1 and 80 μg L-1, respectively. As the method allows the analysis of a large number of samples, it has been successfully applied to monitoring the quality of tap water in 89 municipalities in the northeast region of the State of São Paulo, Brazil.

Trends in sample preparation and separation methods for the analysis of very polar and ionic compounds in environmental water and biota samples

Recent years showed a boost in knowledge about the presence and fate of micropollutants in the environment. Instrumental and methodological developments mainly in liquid chromatography coupled to mass spectrometry hold a large share in this success story. These techniques soon complemented gas chromatography and enabled the analysis of more polar compounds including pesticides but also household chemicals, food additives, and pharmaceuticals often present as traces in surface waters. In parallel, sample preparation techniques evolved to extract and enrich these compounds from biota and water samples. This review article looks at very polar and ionic compounds using the criterion log P ≤ 1. Considering about 240 compounds, we show that (simulated) log D values are often even lower than the corresponding log P values due to ionization of the compounds at our reference pH of 7.4. High polarity and charge are still challenging characteristics in the analysis of micropollutants and these compounds are hardly covered in current monitoring strategies of water samples. The situation is even more challenging in biota analysis given the large number of matrix constituents with similar properties. Currently, a large number of sample preparation and separation approaches are developed to meet the challenges of the analysis of very polar and ionic compounds. In addition to reviewing them, we discuss some trends: for sample preparation, preconcentration and purification efforts by SPE will continue, possibly using upcoming mixed-mode stationary phases and mixed beds in order to increase comprehensiveness in monitoring applications. For biota analysis, miniaturization and parallelization are aspects of future research. For ionic or ionizable compounds, we see electromembrane extraction as a method of choice with a high potential to increase throughput by automation. For separation, predominantly coupled to mass spectrometry, hydrophilic interaction liquid chromatography applications will increase as the polarity range ideally complements reversed phase liquid chromatography, and instrumentation and expertise are available in most laboratories. Two-dimensional applications have not yet reached maturity in liquid-phase separations to be applied in higher throughput. Possibly, the development and commercial availability of mixed-mode stationary phases make 2D applications obsolete in semi-targeted applications. An interesting alternative will enter routine analysis soon: supercritical fluid chromatography demonstrated an impressive analyte coverage but also the possibility to tailor selectivity for targeted approaches. For ionic and ionizable micropollutants, ion chromatography and capillary electrophoresis are amenable but may be used only for specialized applications such as the analysis of halogenated acids when aspects like desalting and preconcentration are solved and the key advantages are fully elaborated by further research. Graphical abstract.

Evaluation of selected buffers for simultaneous determination of ionic and acidic pesticides including glyphosate using anion exchange chromatography with mass spectrometric detection

Ion chromatography coupled with mass spectrometry is an established technique for determination of ionic analytes, however, sophisticated buffer removal equipment is required to eliminate inorganic compounds from the eluate before introduction into the ion source of mass spectrometer. A standard high-performance liquid chromatography coupled with tandem mass spectrometry setup using an ion exchange column (Metrosep® A Supp 5) is proposed as an alternative approach. For that reason, some buffers including non-volatile carboxylic acid based solutions have been evaluated for simultaneous trace determination of ionic and acidic pesticides including glyphosate in the same extract without a need for sophisticated buffer removal equipment. Two differently designed ionisation sources were compared qualitatively for the application of non-volatile buffers. The study revealed that the choice of buffers had a strong influence on matrix effects in case of spiked extract injections. Finally, pesticides with very different physicochemical properties (logP < 0, logP ≥ 0) and structures (containing carboxylate, phosphonate, azolide, azanide, phenolate, bromate, and chlorate moieties) were quantified in spiked beer and oat extracts with acceptable recoveries (80-110%) using tandem mass spectrometry detection with AB SCIEX QTRAP 5500 instrument after separation using edetate buffer.