Detection and confirmation of zilpaterol in equine hair using liquid chromatography-mass spectrometry.

Zilpaterol is a ß2 -adrenergic agonist and a repartitioning agent that has a high potential for abuse in equine performance athletes. Analysis of zilpaterol in hair is an alternative sampling matrix that extends detection time periods beyond those found in urine or blood samples. Our laboratory has been screening for zilpaterol in hair for many years and recently detected and confirmed its presence in official samples. Accordingly, a liquid chromatography-mass spectrometry method was developed and validated to detect and confirm zilpaterol in equine hair. Briefly, equine hair was decontaminated, cut, and pulverized prior to disruption and liquid-liquid extraction in basic conditions. Following extraction, the sample was introduced to an Agilent 1260 HPLC and zilpaterol was separated using a reverse phase gradient with a total run time of 12.5 min. Following chromatographic separation, zilpaterol and its corresponding stable isotope labeled internal standard were introduced via positive mode electrospray ionization to a Thermo Q-Exactive Plus mass spectrometer and spectra collected using parallel reaction monitoring. The methodology was validated using in-house criteria including characterization of accuracy, precision, recovery, linear range, matrix effects, limit of detection, and limit of quantitation, and the method was found to be fit-for-purpose to confirm the presence of zilpaterol in equine hair. This methodology has been used to detect and confirm the presence of zilpaterol from out-of-competition hair samples submitted by regional racing authorities.

Electrospray Ionization Inlet Tandem Mass Spectrometry: A Hyphenated Method for the Sensitive Determination of Chemicals in Animal Tissues and Body Fluids.

This study demonstrates the utility of electrospray ionization inlet mass spectrometry (ESII-MS/MS) for the quantitative determination of analytes in complex animal matrices without chromatographic separation. Veterinary drugs including flunixin, its metabolite 5-hydroxyflunixin, and zilpaterol and persistent organic perfluoroalkyl compounds were determined in incurred plasma, urine, and/or tissue samples. Limits of detection (LOD) of zilpaterol in kidney, liver, lung, and muscle ranged from 0.02 to 0.06 ng/g, whereas the limit of quantitation (LOQ) for zilpaterol in all tissues was 0.1 ng/g. For urinary or plasma flunixin, 5-hydroxyflunixin, and PFOS/PFHxS, LODs ranged from 0.1 to 0.7 ng/mL while the LOQs ranged from 0.4 to 50 ng/mL. Regression coefficients for matrix-matched standard curves were 0.993-0.997, 0.977-0.999, and 0.999 for plasma, tissues, and urine, respectively. Correlations between quantitative results obtained by ESII-MS/MS and LC-MS for flunixin, 5-hydroxyflunixin, and zilpaterol ranged from 0.930 to 0.985. ESII-MS/MS provided rapid, sensitive, and accurate analyses of veterinary drugs and environmental contaminants from complex matrices without chromatographic separation.

Detection and quantification of residues in sheep exposed to trace levels of dietary zilpaterol HCl.

Study objectives were to determine zilpaterol residues in urine and tissues of sheep fed dietary zilpaterol HCl, at levels commensurate with feed contamination, using common and novel screening and quantitative analytical methods. Sheep (50.0 ± 2.7 kg) were offered feed (1.75 kg/d) containing 0.0075 (L), 0.075 (M), or 0.75 (H) mg kg-1 of zilpaterol for 12 days and were slaughtered with 0-day (L-0, M-0, H-0; n = 4 each) or 3-day (H-3; n = 4) withdrawal periods. Rapid immunochromatographic assays (ICA) consistently detected urinary zilpaterol (LOD = 1.7 ng mL-1) in L-0 (54.2%), M-0 (96.0%), and the H-0 (100%) treatment groups but only detected zilpaterol in tissues (LOD ~2.4 ng g-1) from the H-0 group. Advanced MS-based technologies detected zilpaterol in some, but not all, tissues of M-0, H-0, L-0, and H-3 sheep. Analytical techniques commonly used to ensure compliance with show-animal rules, import/export guidelines, and regulatory statutes routinely detected residues in animals exposed to zilpaterol at doses insufficient to elicit growth responses.

[Determination of Zilpaterol in Livestock Products by LC-MS/MS].

An analytical method for the determination of zilpaterol in livestock products was developed. The sample was stirred with n-hexane and n-hexane saturated acetonitrile, and zilpaterol in the sample was extracted with acetonitrile. The extract was cleaned up on a ODS cartridge column (1 g) and SCX cartridge column (500 mg). The LC separation was carried out using an Inertsil ODS-4 column and linear gradient elution with 0.1%formic acid and acetonitrile containing 0.1% formic acid as mobile phase. Detection of MS was carried out positive ion electrospray ionization mode. Average recoveries (n=5) of zilpaterol from 6 kinds of livestock products fortified at the MRLs (0.01 mg/kg) were 87.0-99.4%, and the relative standard deviations were 2.4-6.3%. The limits of quantitation were 0.01 mg/kg.

Simultaneous analysis of spectinomycin, halquinol, zilpaterol, and melamine in feedingstuffs by ion-pair liquid chromatography-tandem mass spectrometry.

A method for the simultaneous analysis of veterinary drug residues (spectinomycin, halquinol, and zilpaterol) and contaminants (melamine) in feedingstuffs by liquid chromatography-tandem mass spectrometry was developed. Method performance for all analytes was evaluated by reversed-phase liquid chromatography, reversed-phase with altered chemical equilibrium, and hydrophilic interaction (HILIC) as chromatographic modes. Validation was in accordance to Commission Decision 657/2002/CE, by considering the best chromatographic approach. Ion-pair liquid chromatography with C18 as stationary phase led to the lowest random uncertainties, effective analyte separation and shorter time of analysis. Low precision deviations and good recovery rates were obtained and thus method reliability and sensitivity could be consolidated. Method applicability was evaluated by the analysis of samples of feedingstuffs, such as cattle, pig, and poultry feeds, feed ingredients of both animal and vegetable origins, and mineral feeds. Some samples showed quantifiable concentrations of halquinol and zilpaterol, reinforcing the importance of this new analytical control method.

Development of an immunochromatographic assay for the ß-adrenergic agonist feed additive zilpaterol.

Zilpaterol is a ß-adrenergic agonist feed additive approved in the United States to increase weight gain and improve feed efficiency of cattle. A zilpaterol immunochromatographic assay was developed as an economical and user-friendly rapid detection method for zilpaterol and validated using urine and tissue samples derived from animal studies. The assay sensitivity was 1.7-23.2 ng g-1 or mL-1 across a variety of feed and animal matrices and did not cross-react with clenbuterol or ractopamine. No sample pre-treatment of cattle and sheep urine was needed, but horse urine and feed required dilution; skeletal muscle required solvent extraction prior to testing. Of 32 incurred sheep urine samples tested, zilpaterol content was correctly identified in all but 2 samples. Horse urine containing >10 ng mL-1 of incurred zilpaterol residue (n = 48) was correctly identified as zilpaterol positive. The assay correctly identified 0-day withdrawal sheep muscle samples as zilpaterol positive and the control and longer withdrawal day sheep muscle samples as negative. Zilpaterol was demonstrated to be stable in horse urine when stored at -20°C for 7 years.

Electron ionization mass spectrometry fragmentation and multiple reaction monitoring quantification of bacterial metabolites of the sea ice biomarker proxy IP25 in Arctic sediments.

RATIONALE: 3,9,13-Trimethyl-6-(1,5-dimethylhexyl)tetradecan-1,2-diol and 2,8,12-trimethyl-5-(1,5-dimethylhexyl)tridecanoic acid appear to be produced during the bacterial metabolism of IP25 , a highly branched isoprenoid lipid often employed for past Arctic sea ice reconstruction. Characterization and quantification of these metabolites in sediments are essential to determine if bacterial degradation may exert a significant influence on IP25 -based palaeo sea ice reconstructions. METHODS: Electron ionization mass spectrometry (EIMS) fragmentation pathways of 3,9,13-trimethyl-6-(1,5-dimethylhexyl)tetradecan-1,2-diol and 2,8,12-trimethyl-5-(1,5-dimethylhexyl)tridecanoic acid trimethylsilyl (TMS) derivatives were investigated. These pathways were deduced by: (i) low-energy collision-induced dissociation (CID) gas chromatography/tandem mass spectrometry (GC/MS/MS), (ii) accurate mass measurement, and (iii) deuterium labelling. RESULTS: CID-MS/MS analyses, accurate mass measurement and deuterium-labelling experiments enabled us to elucidate the EIMS fragmentations of 3,9,13-trimethyl-6-(1,5-dimethylhexyl)tetradecan-1,2-diol and 2,8,12-trimethyl-5-(1,5-dimethylhexyl)tridecanoic acid TMS derivatives. Some specific fragment ions useful in addition to chromatographic retention times for further characterization could be identified. As an application of some of the described fragmentations, the TMS derivatives of these metabolites were characterized and quantified in MRM mode in different Arctic sediments. CONCLUSIONS: EIMS fragmentations of 3,9,13-trimethyl-6-(1,5-dimethylhexyl)tetradecan-1,2-diol and 2,8,12-trimethyl-5-(1,5-dimethylhexyl)tridecanoic acid TMS derivatives exhibit specific fragment ions, which appear to be very useful for the quantification of these bacterial metabolites of the palaeo tracer IP25 in sediments.

Compression of multidimensional NMR spectra allows a faster and more accurate analysis of complex samples.

We propose an approach to efficiently compress and denoise multidimensional NMR spectral data, improving their corresponding storage, handling, and analysis. This method has been tested with 2D homonuclear, 2D and 3D heteronuclear, and 2D phase-sensitive NMR spectral data and shown to be especially powerful for 2D NMR metabolomics studies.

Analysis of Metabolites from the Tricarboxylic Acid Cycle for Yeast and Bacteria Samples Using Gas Chromatography Mass Spectrometry.

We here explain step by step the implementation of gas chromatography coupled with tandem mass spectrometry for the quantitative analysis of intracellular metabolites from the tricarboxylic acid (TCA) cycle such as citrate, isocitrate, alpha-ketoglutarate, succinate, malate, and fumarate. Isotope dilution is used to correct for potential metabolite losses during sample processing, matrix effects, incomplete derivatization, and liner contamination. All measurements are performed in selected reaction monitoring (SRM) mode. Standards and samples are first diluted with a fixed volume of a mixture of fully 13 C-labeled internal standards and then derivatized to give trimethylsilyl-methoxylamine derivatives prior GC-MS/MS analysis.

Simultaneous analysis of carbohydrates, polyols and amines in urine samples using chemical ionization gas chromatography with tandem mass spectrometry.

A simple method for the simultaneous derivatization of carbohydrates, polyols, amines and amino acids using hexamethyldisilazane and N,O-bis(trimethylsilyl)trifluoroacetamide was developed. This method allows the direct derivatization of urine samples without sample pretreatment before derivatization. The method was successfully used for analysis of the selected metabolites in urine samples of healthy individuals and neonates suffering from galactosemia. The limits of detection by positive chemical ionization gas chromatography with tandem mass spectrometry analysis were in the range of 1.0 mgL-1 for mannitol to 4.7 mg/L for glucose.

Development and Method Validation of Analysis of Urushiol in Sumac and Food Ingredients in Korea.

This study developed an analytical method to determine the urushiol content in sap and several foods. The full process for urushiol analysis consists of extraction, trimethylsilyl silylation, analysis, and identification via GC-MS, with each step optimized to attain the required accuracy and precision. Urushiol was separated from sap via liquid-liquid extraction and was derivatized via silylation. The components were analyzed using a polar capillary column and identified using GC-MS. The deviations of relative retention times and retention time windows were within 0.001 and 0.02 min, which satisfied the criteria of 0.06 and 0.03 min, respectively. The response of the urushiol standards tested was found to be linear in the investigated concentration range, with a correlation coefficient of 0.998. The LODs were between 1.74 and 2.67 µg/mL.

Gas chromatographic-mass spectrometric determination of glycosides without prior hydrolysis.

The article presents for the first time the linear temperature programmed retention indices on a column with stationary phases of 5% phenylpolydimethyl silicone and the mass spectra of trimethylsilyl (TMS) derivatives of 71 glycosides (both commercial preparations and compounds extracted from plant tissues) which were not characterized earlier by these parameters. Converted to their TMS derivatives, the glycosides were thermally stable: they exhibited single peaks on their chromatograms without products of thermal decomposition. Therefore this work demonstrates the suitability of high resolution-high temperature gas chromatography (HR-HT/GC) to analyse different groups of glycosides including compounds with disaccharide moieties without the necessity of their hydrolyses. Since a limited number of commercial and plant-isolated glycosides were available, an attempt was made to assess their retention indices using the known "structure-retention relationships" approach. It was demonstrated that the retention indices of silanised glycosides and their aglycones were characterized by a linear dependence.

Quantitative carbon detector for enhanced detection of molecules in foods, pharmaceuticals, cosmetics, flavors, and fuels.

Analysis of trace compounds, such as pesticides and other contaminants, within consumer products, fuels, and the environment requires quantification of increasingly complex mixtures of difficult-to-quantify compounds. Many compounds of interest are non-volatile and exhibit poor response in current gas chromatography and flame ionization systems. Here we show the reaction of trimethylsilylated chemical analytes to methane using a quantitative carbon detector (QCD; the Polyarc™ reactor) within a gas chromatograph (GC), thereby enabling enhanced detection (up to 10×) of highly functionalized compounds including carbohydrates, acids, drugs, flavorants, and pesticides. Analysis of a complex mixture of compounds shows that the GC-QCD method exhibits faster and more accurate analysis of complex mixtures commonly encountered in everyday products and the environment.

Oxidative stress: Determination of 4-hydroxy-2-nonenal by gas chromatography/mass spectrometry in human and rat plasma.

The lipid peroxidation product 4-hydroxynonenal (HNE) is a biomarker of oxidative stress which is essentially involved in the pathophysiology of many diseases. The analysis of HNE is challenging because this aldehyde is extremely reactive and thus unstable. Hence, we adopted a gas chromatography-mass spectrometry (GC-MS) method based on derivatization of HNE with pentafluorobenzyl-hydroxylamine-HCl followed by trimethylsilylation to trimethylsilyl ethers. Ions representative for a negative ion chemical ionization mode were recorded at m/z = 152 for HNE and at m/z = 162 for the deuterated analogon (HNE-d11) as internal standard. This excellent stable and precise GC-MS method was carefully validated for HNE, and showed good linearity (r(2) = 0.998), and high specificity and sensitivity. Within-day precisions were 4.4-6.1% and between-day precisions were 5.2-10.2%. Accuracies were between 99% and 104% for the whole calibration range (2.5-250 nmol/L) of HNE. To examine the versatility of this modified GC-MS method, we analyzed HNE in ethylenediaminetetraacetic acid (EDTA) plasma in a well-defined collective of migraine patients; recently published. The results underline our former observations that women with migraine are afflicted with increased levels of HNE. Patients with thyroidal dysfunction showed no significant HNE alterations. This was confirmed by normal HNE EDTA plasma levels in hyper- und hypothyroid Sprague-Dawley rats. Taken together, the GC-MS method presented herein is of excellent quality to record oxidative stress-related bioactive HNE levels. This is important for a reorientation of oxidative stress analytics in other human diseases first of atherosclerosis and cancer.

Determination of terpenoid indole alkaloids in hairy roots of Rhazya stricta (Apocynaceae) by GC-MS.

INTRODUCTION: Rhazya stricta Decne. (Apocynaceae) is a medicinal plant rich in terpenoid indole alkaloids (TIAs), some of which possess important pharmacological properties. The study material including transgenic hairy root cultures have been developed and their potential for alkaloid production are being investigated. OBJECTIVE: In this study, a comprehensive GC-MS method for qualitative and quantitative analysis of alkaloids from Rhazya hairy roots was developed. METHODS: The composition of alkaloids was determined by using GC-MS. In quantification, the ratio between alkaloid and internal standard was based on extracted ion from total ion current (TIC) analyses. RESULTS: The developed method was validated. An acceptable precision with RSD ≤ 8% over a linear range of 1 to 100 µg/mL was achieved. The accuracy of the method was within 94-107%. Analysis of hairy root extracts indicated the occurrence of a total of 20 TIAs. Six of them, pleiocarpamine, fluorocarpamine, vincamine, ajmalicine and two yohimbine isomers are reported here for the first time in Rhazya. Trimethylsilyl (TMS) derivatisation of the extracts resulted in the separation of two isomers for yohimbine and also for vallesiachotamine. Clearly improved chromatographic profiles of TMS-derivatives were observed for vincanine and for minor compounds vincamine and rhazine. CONCLUSION: The results show that the present GC-MS method is reliable and well applicable for studying the variation of indole alkaloids in Rhazya samples.

Improved stability of TMS derivatives for the robust quantification of plant polar metabolites by gas chromatography-mass spectrometry.

Plant metabolite profiling is commonly carried out by GC-MS of methoximated trimethylsilyl (TMS) derivatives. This technique is robust and enables a library search for spectra produced by electron ionization. However, recent articles have described problems associated with the low stability of some TMS derivatives. This limits the use of GC-MS for metabolomic studies that need large sets of qualitative and quantitative analyses. The aim of this work is to determine the experimental conditions in which the stability of TMS derivatives could be improved. This would facilitate the analysis of the large-scale experimental designs needed in the metabolomics approach. For good repeatability, the sampling conditions and the storage temperature of samples during analysis were investigated. Multiple injections of one sample from one vial led to high variations while injection of one sample from different vials improved the analysis. However, before injection, some amino acid TMS derivatives were degraded during the storage of vials in the autosampler. Only 10% of the initial quantity of glutamine 3 TMS and glutamate 3 TMS and 66% of α-alanine 2 TMS was detected 48 h after derivatization. When stored at 4 °C until injection, all TMS derivatives remained stable for 12 h; at -20 °C, they remained stable for 72 h. From the integration of all these results, a detailed analytical procedure is thus proposed. It enables a robust quantification of polar metabolites, useful for further plant metabolomics studies using GC-MS.

Sequential derivatization of polar organic compounds in cloud water using O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride, N,O-bis(trimethylsilyl)trifluoroacetamide, and gas-chromatography/mass spectrometry analysis.

Cloud water samples from Whiteface Mountain, NY were used to develop a combined sampling and gas chromatography-mass spectrometric (GCMS) protocol for evaluating the complex mixture of highly polar organic compounds (HPOC) present in this atmospheric medium. Specific HPOC of interest were mono- and di keto-acids which are thought to originate from photochemical reactions of volatile unsaturated hydrocarbons from biogenic and manmade emissions and be a major fraction of atmospheric carbon. To measure HPOC mixtures and the individual keto-acids in cloud water, samples first must be derivatized for clean elution and measurement, and second, have low overall background of the target species as validated by GCMS analysis of field and laboratory blanks. Here, we discuss a dual derivatization method with PFBHA and BSTFA which targets only organic compounds that contain functional groups reacting with both reagents. The method also reduced potential contamination by minimizing the amount of sample processing from the field through the GCMS analysis steps. Once derivatized only gas chromatographic separation and selected ion monitoring (SIM) are needed to identify and quantify the polar organic compounds of interest. Concentrations of the detected total keto-acids in individual cloud water samples ranged from 27.8 to 329.3ngmL(-1) (ppb). Method detection limits for the individual HPOC ranged from 0.17 to 4.99ngmL(-1) and the quantification limits for the compounds ranged from 0.57 to 16.64ngmL(-1). The keto-acids were compared to the total organic carbon (TOC) results for the cloud water samples with concentrations of 0.607-3.350mgL(-1) (ppm). GCMS analysis of all samples and blanks indicated good control of the entire collection and analysis steps. Selected ion monitoring by GCMS of target keto-acids was essential for screening the complex organic carbon mixtures present at low ppb levels in cloud water. It was critical for ensuring high levels of quality assurance and quality control and for the correct identification and quantification of key marker compounds.

Analytical methodology for sampling and analysing eight siloxanes and trimethylsilanol in biogas from different wastewater treatment plants in Europe.

Siloxanes and trimethylsilanol belong to a family of organic silicone compounds that are currently used extensively in industry. Those that are prone to volatilisation become minor compounds in biogas adversely affecting energetic applications. However, non-standard analytical methodologies are available to analyse biogas-based gaseous matrixes. To this end, different sampling techniques (adsorbent tubes, impingers and tedlar bags) were compared using two different configurations: sampling directly from the biogas source or from a 200 L tedlar bag filled with biogas and homogenised. No significant differences were apparent between the two sampling configurations. The adsorbent tubes performed better than the tedlar bags and impingers, particularly for quantifying low concentrations. A method for the speciation of silicon compounds in biogas was developed using gas chromatography coupled with mass spectrometry working in dual scan/single ion monitoring mode. The optimised conditions could separate and quantify eight siloxane compounds (L2, L3, L4, L5, D3, D4, D5 and D6) and trimethylsilanol within fourteen minutes. Biogas from five waste water treatment plants located in Spain, France and England was sampled and analysed using the developed methodology. The siloxane concentrations in the biogas samples were influenced by the anaerobic digestion temperature, as well as the nature and composition of the sewage inlet. Siloxanes D4 and D5 were the most abundant, ranging in concentration from 1.5 to 10.1 and 10.8 to 124.0 mg Nm(-3), respectively, and exceeding the tolerance limit of most energy conversion systems.

Whole air canister sampling coupled with preconcentration GC/MS analysis of part-per-trillion levels of trimethylsilanol in semiconductor cleanroom air.

The costly damage airborne trimethylsilanol (TMS) exacts on optics in the semiconductor industry has resulted in the demand for accurate and reliable methods for measuring TMS at trace levels (i.e., parts per trillion, volume per volume of air [ppt(v)] [~ng/m(3)]). In this study I developed a whole air canister-based approach for field sampling trimethylsilanol in air, as well as a preconcentration gas chromatography/mass spectrometry laboratory method for analysis. The results demonstrate clean canister blanks (0.06 ppt(v) [0.24 ng/m(3)], which is below the detection limit), excellent linearity (a calibration relative response factor relative standard deviation [RSD] of 9.8%) over a wide dynamic mass range (1-100 ppt(v)), recovery/accuracy of 93%, a low selected ion monitoring method detection limit of 0.12 ppt(v) (0.48 ng/m(3)), replicate precision of 6.8% RSD, and stability (84% recovery) out to four days of storage at room temperature. Samples collected at two silicon wafer fabrication facilities ranged from 10.0 to 9120 ppt(v) TMS and appear to be associated with the use of hexamethyldisilazane priming agent. This method will enable semiconductor cleanroom managers to monitor and control for trace levels of trimethylsilanol.

Systematic derivatization, mass fragmentation and acquisition studies in the analysis of chlorophenols, as their silyl derivatives by gas chromatography-mass spectrometry.

An exhaustive GC-MS sample preparation, derivatization, mass fragmentation and acquisition study was performed, for the simultaneous analysis of chlorophenols (CPs). Selected species were 2-CP, 3-CP, 4-CP, 3,5-dichlorophenol (diCP), 2,5-diCP, 2,6-diCP, 2,4-diCP, 2,3-diCP, 3,4-diCP 2,4,6-trichlorophenol (triCP), 2,4,5-triCP, 2,3,4-triCP, 2,3,4,6-tetrachlorophenol (tetraCP) and pentachlorophenol (pentaCP), in total 14 compounds. As novelties to the field, basic researches, like systematic derivatization, mass fragmentation and acquisition methods have been optimized for the trimethylsilyl (TMS) ether derivatives of CPs. The reactivity of chlorophenols with silylating agents has not been systematically analyzed. Here, we studied the reactivity of 14 chlorophenols with five silylating reagents. The three acquisition techniques, the full scan (FS), the multiple ion monitoring (MIM), and the currently optimized multiple reaction monitoring (MRM) methods, have been compared. We developed a new analytical approach, simultaneously monitoring the fragmentation pattern of the (35)Cl and the (37)Cl containing fragment ions both as precursor and as product ions. This principle resulted in remarkable specificity and sensitivity of detection and quantification; particularly in the cases of the tetraCP and pentaCP derivatives containing the (35)Cl and the (37)Cl fragment ions at an approximate ratio of <1:1. Detailed documentation of the loss of HCl via fragmentation processes, without decomposition of the benzene ring, was attributed to the "ring-walk" mechanism described first for monochlorophenol. Critical evaluation of the derivatization and acquisition protocols was collated and validated with the same characteristics. Data of six point calibration along with the corresponding relative standard deviation percentage (RSD%) values, in the line of FS, MIM and MRM methods (r(2): 0.9987, 0.9992, 0.9989; RSD%: 8.7, 5.6, 8.1), proved to be independent on the acquisition processes. The practical utility of the optimized MRM acquisition techniques was confirmed by the quantitation of the CP contents of Danube River, tap water and distilled water samples. Results confirmed at the first time the primary importance of the MRM acquisition method, even in comparison to the MIM one: we revealed that distilled water contains higher chlorophenol content than tap water, which might have a great significance for the water industry.