Quantitative and qualitative analysis of polycyclic aromatic hydrocarbons in urine samples using a non-separative method based on mass spectrometry

Development of a non-separative screening strategy based on mass spectrometry for the semi-quantification of urinary polycyclic aromatic hydrocarbon metabolites

A fast and non-separative screening strategy is presented for the analysis of five urinary metabolites of polycyclic aromatic hydrocarbons (PAHs), namely 2-naphthol, 1-acenaphthenol, 2-hydroxyfluorene, 9-phenanthrol and 1-hydroxypyrene. These hydroxylated derivatives (OH-PAHs) were subjected to enzymatic hydrolysis and were extracted from urine using a liquid-liquid extraction (LLE). The profile signals were obtained by direct injection of the sample into a programmed temperature vaporizer coupled to a quadrupole mass spectrometer via a deactivated fused silica tubing (PTV-qMS). Semi-quantitative determination was carried out by means of partial least squares regression (PLS1) using urine samples free of the analytes and spiked at several uncorrelated concentration levels. The multivariate calibration models worked satisfactorily, with errors ranging between 30 and 33 % for all the analytes except for 1-acenaphthenol that provided an error of 39 % when external validation set was considered. The repeatability and reproducibility, expressed as relative standard deviation (RSD), were ranged between 8-16 % and 11-18 %, respectively. The proposed method could be a useful tool for semi-quantification purposes of five OH-PAHs in urine samples, identifying positive samples for subsequent further chromatographic separation (confirmation), thus saving time and costs.

Determination of Hydroxy Polycyclic Aromatic Hydrocarbons in Human Urine Using Automated Microextraction by Packed Sorbent and Gas Chromatography-Mass Spectrometry

A fast methodology for the determination of monohydroxy polycyclic aromatic hydrocarbons in human urine using a fully automated microextraction by packed sorbent coupled to a gas chromatograph-mass spectrometer is reported. Sample preparation requires simple hydrolysis, centrifugation, filtration, and dilution. The method does not require a derivatization step prior to analysis with gas chromatography and allows the measurement of up to three samples per hour after hydrolysis. Quantitation is carried out by a one-point standard addition allowing the determination of 6 analytes with good limits of detection (10.1-39.6 ng L^-1 in water and 0.5-19.4 µg L^-1 in urine), accuracy (88-110%) and precision (2.1-23.4% in water and 5.1-19.0% in urine) values. This method has been successfully applied to the analysis of six urine samples (three from smoker and three from non-smoker subjects), finding significant differences between both types of samples. Results were similar to those found in the literature for similar samples, which proves the applicability of the methodology.

Determination of leucine and isoleucine/allo-isoleucine by electrospray ionization-tandem mass spectrometry and partial least square regression: Application to saliva samples

Herein we propose, for the first time, a rapid method based on flow injection analysis, electrospray ionization-tandem mass spectrometry (FIA-ESI-MS/MS) and multivariate calibration for the determination of l-leucine, l-isoleucine and L-allo-isoleucine in saliva. As far as we know, multivariate calibration has never been applied to the data from this non-separative approach. The possibilities of its use were explored and the results obtained were compared with the corresponding ones when using univariate calibration. Partial least square regression (PLS1) multivariate calibration models were built for each analyte by analyzing different saliva samples, and were subsequently applied to the analysis of another set of samples which had not been used in any calibration step. For Leu, the model worked satisfactorily with root mean square errors in the prediction step of 17%. This error can be considered acceptable and is common in methodologies that do not include a separation step. Results were compared with those obtained when univariate calibration was used, using the m/z transition 132.1 → 43.0 as the quantitation variable. In this case, the obtained results were not acceptable, with RMSEP of 236%, due to the fact that saliva samples contained another compound, different to the target analytes, which also shared the same transition. Ile and aIle have the same fragmentation patterns, so quantification of the sum of both compounds was performed, with RMSEP of 14% using a PLS1 model. Similar results were obtained when a univariate calibration model using the m/z transition 132.1 → 69.0 was employed. However, the use of this transition should be carefully examined when other compounds present in the matrix contribute to the analytical signal. The method increases sample throughput more than one order of magnitude compared to the corresponding LC-ESI-MS/MS method and is especially suitable as screening. When abnormally high or low concentrations of the analytes studied are obtained, the use of the method that includes separation is recommended to confirm the results.

Polycyclic aromatic hydrocarbons in edible oils and fatty foods: Occurrence, formation, analysis, change and control

Numerous studies have demonstrated that dozens of polycyclic aromatic hydrocarbons (PAHs) are mutagenic, genotoxic and strongly carcinogenic. PAHs are found to be widely present in foods contaminated through multiple paths. Due to their lipophilic nature, these compounds easily accumulate in edible oils and fatty foods where they can range from no detection to over 2000μg/kg. Compared to precursor PAHs, researchers have seldom studied the presence of PAH derivatives, especially in food matrices. This chapter includes the physical and chemical characteristics of PAHs and their types, occurrence, sample pretreatment and instrumental determination methods, and their formation, change and control in edible oils and fatty foods. The occurrence and formation of PAH derivatives in foods are much less investigated compared to those of their precursor PAHs. Although the removal of matrix effects and accuracy remain difficult for current rapid determination methods, a prospective research direction of PAH analysis for large-scale screening is in demand. To date, physical absorption, chemical oxidation and biodegradation have been widely used in PAH removal techniques. Specific types of bacteria, fungi, and algae have also been used to degrade PAHs into harmless compounds. However, most of them can only degrade a range of LPAHs, such as naphthalene, anthracene and phenanthrene. Their ability to degrade HPAHs requires further study. Moreover, it is still a great challenge to maintain food nutrition and flavor during the PAH removal process using these methods.