Tandem Mass Spectrometric Characterization of Fetuin Sialylated Glycopeptides Enriched by TiO2 Microcolumn

Sialylation of glycoproteins is vital for the function or physicochemical properties of a protein. It becomes more and more important to develop approaches that can be used to efficiently isolate and identify sialylated glycopeptides or glycoproteins for monitoring changes in glycoproteome. In the present study, we analyze intact structures of the enriched sialylated glycopeptides of bovine fetuin by matrix‐assisted laser desorption/ionization‐tandem mass spectrometry (MALDI‐MS/MS), without any chemical derivation. The experimental data show that the optimal loading buffer for TiO₂ as matrix is 80% acetonitrile/2% TFA (trifluoroacetic acid)/100 mg/mL DHB (2,5‐dihydroxybenzoic acid) which is also compatible with MALDI‐mass spectrometric analysis. This study indicates that the improved enrichment approach combined with MALDI‐MS/MS may be a powerful tool to analyze intact structures and components of the sialylated glycopeptides from complex peptide mixture.     

Analysis of human plasma lipids and soybean lecithin by means of high‐performance thin‐layer chromatography and matrix‐assisted laser desorption/ionization mass spectrometry

An improved analytical strategy for the analysis of complex lipid mixtures using matrix‐assisted laser desorption/ionization mass spectrometry (MALDI‐MS) in combination with high‐performance thin‐layer chromatography (HPTLC) is reported. Positive ion MALDI RTOF MS was applied as a rapid screening tool for the various neutral (e.g. triacylglycerols) and polar (e.g. glycerophospholipids and ‐sphingolipids) lipid classes derived from crude lipid extracts of e.g. human plasma as well as soybean lecithin. Finally, MALDI seamless post‐source decay (PSD) product ion analysis was performed in order to obtain further structural information (head‐ and acyl‐group identification) of selected lipid species and structure verification. A Coomassie Brilliant Blue R‐250 staining protocol for lipids on HPTLC plates was evaluated and was found to be fully compatible with subsequent MALDI‐MS. Lipids were analyzed after elution from the HPTLC phase material of the selected band (corresponding to certain lipid classes) by using the proper organic solvent mixture or in few cases directly from the HPTLC plates (a type of on‐line HPTLC/MALDI‐MS coupling). More than 70 distinct lipid species from seven different lipid classes in the range between m/z 500 and 1500 could be identified from the lipid extracts of human plasma and soybean lecithin, respectively. The general high sensitivity of MALDI‐MS detection allowed the analysis of even minor lipid classes from only very small volumes of human plasma (50 µL). The combination of HPTLC, Coomassie staining and positive ion MALDI curved field RTOF‐MS represents a straightforward strategy during lipidomics studies of food and clinically relevant human lipid samples. Copyright © 2009 John Wiley & Sons, Ltd.     

Analysis of cancer cell lipids using matrix‐assisted laser desorption/ionization 15‐T Fourier transform ion cyclotron resonance mass spectrometry

A combination of methodologies using the extremely high mass accuracy and resolution of 15‐T Fourier transform ion cyclotron resonance (FT‐ICR) mass spectrometry (MS) was introduced for the identification of intact cancer cell phospholipids. Lipids from a malignant glioma cell line were initially analyzed at a resolution of >200 000 and identified by setting the mass tolerance to ±1 mDa using matrix‐assisted laser desorption/ionization (MALDI) 15‐T FT‐ICR MS in positive ion mode. In most cases, a database search of potential lipid candidates using the exact masses of the lipids yielded only one possible chemical composition. Extremely high mass accuracy (<0.1 ppm) was then attained by using previously identified lipids as internal standards. This, combined with an extremely high resolution (>800 000), yielded well‐resolved isotopic fine structures allowing for the identification of lipids by MALDI 15‐T FT‐ICR MS without using tandem mass spectrometric (MS/MS) analysis. Using this method, a total of 38 unique lipids were successfully identified. Copyright © 2012 John Wiley & Sons, Ltd.     

Lipid fingerprinting of gram-positive lactobacilli by intact--matrix-assisted laser desorption/ionization mass spectrometry using a proton sponge based matrix

A method of direct lipid analysis by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) in intact membranes, without prior extraction/separation steps, is described. Here, we demonstrate the efficacy of a strong base, 1,8-bis(dimethylamino)naphthalene (DMAN; proton sponge), as a novel matrix for MALDI-time-of-flight (TOF) MS analysis of whole cell bacteria. Initially, individual acidic low-molecular-weight analytes such as standard free fatty acids and phospholipids were analyzed using DMAN as matrix. Clear negative-mode MALDI-TOF MS spectra of all analytes show only deprotonated analyte signals at a low picomole limit of detection with the complete absence of matrix-related signals. These results indicate that DMAN represents a suitable matrix for MALDI-TOF MS analysis of mixtures of complex lipids as the intact membranes of microorganisms. DMAN was successfully applied to the analysis of Lactobacillus sanfranciscensis and L. plantarum microorganisms. Different components were sensitively detected in a single spot, including 16:0, 18:2, 18:3, and 21:0 free acids, glycolipids, phosphatidylglycerols (PGs) and cardiolipins. This method might be of general application, offering the advantage of quickly gaining information about lipid components of other gram-positive bacterial membranes.     

Analysis of monoclonal antibody by a novel CE‐UV/MALDI‐MS interface

mAbs are highly complex proteins that present a wide range of microheterogeneity that requires multiple analytical methods for full structure assessment and quality control. As a consequence, the characterization of mAbs on different levels is particularly product‐ and time‐consuming. CE‐MS couplings, especially to MALDI, appear really attractive methods for the characterization of biological samples. In this work, we report the last instrumental development and performance of the first totally automated off‐line CE‐UV/MALDI‐MS/MS. This interface is based on the removal of the original UV cell of the CE apparatus, modification of the spotting device geometry, and creation of an integrated delivery matrix system. The performance of the method was evaluated with separation of five intact proteins and a tryptic digest mixture of nine proteins. Intact protein application shows the acquisition of electropherograms with high resolution and high repeatability. In the peptide mapping approach, a total number of 154 unique identified peptides were characterized using MS/MS spectra corresponding to average sequence coverage of 64.1%. Comparison with NanoLC/MALDI‐MS/MS showed complementarity at the peptide level with an increase of 42% when using CE/MALDI‐MS coupling. Finally, this work represents the first analysis of intact mAb charge variants by CZE using an MS detection. Moreover, using a peptide mapping approach CE‐UV/MALDI‐MS/MS fragmentation allowed 100% sequence coverage of the light chain and 92% of the heavy chain, and the separation of four major glycosylated peptides and their structural characterization.     

Hydrazide and hydrazine reagents as reactive matrices for MALDI‐MS to detect gaseous aldehydes

The reagents 19 hydrazide and 14 hydrazine were examined to function as reactive matrices for matrix‐assisted laser desorption/ionization mass spectrometry (MALDI‐MS) to detect gaseous aldehydes. Among them, two hydrazide (2‐hydroxybenzohydrazide and 3‐hydroxy‐2‐naphthoic acid hydrazide) and two hydrazine reagents [2‐hydrazinoquinoline and 2,4‐dinitrophenylhydrazine (DNPH)] were found to react efficiently with carbonyl groups of gaseous aldehydes (formaldehyde, acetaldehyde and propionaldehyde); these are the main factors for sick building syndrome and operate as reactive matrices for MALDI‐MS. Results from accurate mass measurements by JMS‐S3000 Spiral‐TOF suggested that protonated ion peaks corresponding to [M + H]⁺ from the resulting derivatives were observed in all cases with the gaseous aldehydes in an incubation, time‐dependent manner. The two hydrazide and two hydrazine reagents all possessed absorbances at 337 nm (wavelength of MALDI nitrogen laser), with, significant electrical conductivity of the matrix crystal and functional groups, such as hydroxy group and amino group, being important for desorption/ionization efficiency in MALDI‐MS. To our knowledge, this is the first report that gaseous molecules could be derivatized and detected directly in a single step by MALDI‐MS using novel reactive matrices that were derivatizing agents with the ability to enhance desorption/ionization efficiency. Copyright © 2014 John Wiley & Sons, Ltd.     

Application of porous metal enrichment probe sampling to single cell analysis using matrix‐assisted laser desorption ionization time of flight mass spectrometry (MALDI‐TOF‐MS)

There is an increasing need for analyzing metabolism in a single cell, which is important to understand the nature of cellular heterogeneity, disease, growth and specialization, etc. However, single cell analysis is often challenging for the traces of samples. In the present study, porous metal enrichment probe sampling combined with matrix‐assisted laser desorption ionization time of flight mass spectrometry ( MALDI‐TOF‐MS) has been applied for in situ analysis of live onion epidemic cell. Porous probe, treated by corroding copper wire with HCl, was directly inserted into a single cell to get cell solution. A self‐made linear actuator was enough to control the penetration of probe into the target cell accurately. Then samples on the tip of probe were eluted and detected by a commercial MALDI‐TOF‐MS directly. The formation of porous microstructure on the probe surface increased the adsorptive capacity of cell solution. The sensitivity of porous probe sampling was 6 times higher than uncorroded probes generally. This method provides a sensitive and convenient way for the sampling and detection of single cell solution. Copyright © 2015 John Wiley & Sons, Ltd.     

A convenient purification and preconcentration of peptides with α‐cyano‐4‐hydroxycinnamic acid matrix crystals in a pipette tip for matrix‐assisted laser desorption/ionization mass spectrometry

Peptide samples derived from enzymatic in‐gel digestion of proteins resolved by gel electrophoresis often contain high amount of salts originating from reaction and separation buffers. Different methods are used for desalting prior to matrix‐assisted laser desorption/ionization (MALDI) mass spectrometry (MS), e.g. reversed‐phase pipette tip purification, on‐target washing, adding co‐matrices, etc. As a suitable matrix for MALDI MS of peptides, α‐cyano‐4‐hydroxycinnamic acid (CHCA) is frequently used. Crystalline CHCA shows the ability to bind peptides on its surface and because it is almost insoluble in acidic water solutions, the on‐target washing of peptide samples can significantly improve MALDI MS signals. Although the common on‐target washing represents a simple, cheap and fast procedure, only a small portion of the available peptide solution is efficiently used for the subsequent MS analysis. The present approach is a combination of the on‐target washing principle carried out in a narrow‐end pipette tip (e.g. GELoader tip) and preconcentration of peptides from acidified solution by passing it through small CHCA crystals captured inside the tip on a glass microfiber frit. The results of MALDI MS analysis using CHCA‐tip peptide preconcentration are comparable with the use of homemade POROS R2 pipette tip microcolumns. Advantages and limitations of this approach are discussed. Copyright © 2009 John Wiley & Sons, Ltd.     

High‐resolution MALDI‐TOF MS study on analysis of low‐molecular‐weight products from photo‐oxidation of poly(3‐hexylthiophene)

High‐resolution matrix‐assisted laser desorption/ionization (MALDI) time‐of‐flight mass spectrometry (TOF MS) was used for the analysis of the low‐molecular‐weight products from the photo‐oxidation of poly(3‐hexylthiophene) (P3HT) in solution and thin film. Eight new peak series were observed in the low‐mass range of the mass spectra of the products degraded in solution, and the formulas of the eight components were determined from the accurate mass. From SEC/MALDI‐TOF MS, two components were identified as the degraded products, and the other six components were derived from the fragmentation of the degraded products during the MALDI process. A mechanism for the formation of these components was proposed on the basis of the results of MALDI‐TOF MS. For the thin film degradation, a part of products in the solution degradation were observed, which supports that the oxidation of P3HT in solution and thin film proceeded in the same mechanism. This study shows that high‐resolution MALDI‐TOF MS is effective for the analysis of the low‐molecular‐weight products from P3HT photo‐oxidation and expected to be feasible for the degradation analyses of other polymers. Copyright © 2015 John Wiley & Sons, Ltd.     

The improved performance of MALDI‐TOF MS on the analysis of herbal saponins by using DHB‐GO composite matrix

Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) is an excellent analytical technique for rapid analysis of a variety of molecules with straightforward sample pretreatment. The performance of MALDI‐TOF MS is largely dependent on matrix type, and the development of novel MALDI matrices has aroused wide interest. Herein, we devoted to seek more robust MALDI matrix for herbal saponins than previous reported, and ginsenoside Rb1, Re, and notoginsenoside R1 were used as model saponins. At the beginning of the present study, 2,5‐dihydroxybenzoic acid (DHB) was found to provide the highest intensity for saponins in four conventional MALDI matrices, yet the heterogeneous cocrystallization of DHB with analytes made signal acquisition somewhat “hit and miss.” Then, graphene oxide (GO) was proposed as an auxiliary matrix to improve the uniformity of DHB crystallization due to its monolayer structure and good dispersion, which could result in much better shot‐to‐shot and spot‐to‐spot reproducibility of saponin analysis. The satisfactory precision further demonstrated that minute quantities of GO (0.1 μg/spot) could greatly reduce the risk of instrument contamination caused by GO detachment from the MALDI target plate under vacuum. More importantly, the sensitivity and linearity of the standard curve for saponins were improved markedly by DHB‐GO composite matrix. Finally, the application of detecting the Rb1 in complex biological sample was exploited in rat plasma and proved it applicable for pharmacokinetic study quickly. This work not only opens a new field for applications of DHB‐GO in herbal saponin analysis but also offers new ideas for the development of composite matrices to improve MALDI MS performance.     

MALDI‐based intact spore mass spectrometry of downy and powdery mildews

Fast and easy identification of fungal phytopathogens is of great importance in agriculture. In this context, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) has emerged as a powerful tool for analyzing microorganisms. This study deals with a methodology for MALDI‐TOF MS‐based identification of downy and powdery mildews representing obligate biotrophic parasites of crop plants. Experimental approaches for the MS analyses were optimized using Bremia lactucae, cause of lettuce downy mildew, and Oidium neolycopersici, cause of tomato powdery mildew. This involved determining a suitable concentration of spores in the sample, selection of a proper MALDI matrix, looking for the optimal solvent composition, and evaluation of different sample preparation methods. Furthermore, using different MALDI target materials and surfaces (stainless steel vs polymer‐based) and applying various conditions for sample exposure to the acidic MALDI matrix system were investigated. The dried droplet method involving solvent evaporation at room temperature was found to be the most suitable for the deposition of spores and MALDI matrix on the target and the subsequent crystallization. The concentration of spore suspension was optimal between 2 and 5 × 10⁹ spores per ml. The best peptide/protein profiles (in terms of signal‐to‐noise ratio and number of peaks) were obtained by combining ferulic and sinapinic acids as a mixed MALDI matrix. A pretreatment of the spore cell wall with hydrolases was successfully introduced prior to MS measurements to obtain more pronounced signals. Finally, a novel procedure was developed for direct mass spectra acquisition from infected plant leaves. Copyright © 2012 John Wiley & Sons, Ltd.     

MALDI‐FT‐ICR‐MS for archaeological lipid residue analysis

Soft‐ionization methods are currently at the forefront of developing novel methods for analysing degraded archaeological organic residues. Here, we present little‐used soft ionization method of matrix assisted laser desorption/ionization‐Fourier transform‐ion cyclotron resonance‐mass spectrometry (MALDI‐FT‐ICR‐MS) for the identification of archaeological lipid residues. It is a high‐resolution and sensitive method with low limits of detection capable of identifying lipid compounds in small concentrations, thus providing a highly potential new technique for the analysis of degraded lipid components. A thorough methodology development for analysing cooked and degraded food remains from ceramic vessels was carried out, and the most efficient sample preparation protocol is described. The identified components, also controlled by independent parallel analysis by gas chromatography‐mass spectrometry (GC‐MS) and gas chromatography‐combustion‐isotope ratio mass spectrometry (GC‐C‐IRMS), demonstrate its capability of identifying very different food residues including dairy, adipose fats as well as lipids of aquatic origin. The results obtained from experimentally cooked and original archaeological samples prove the suitability of MALDI‐FT‐ICR‐MS for analysing archaeological organic residues. Sample preparation protocol and identification of compounds provide future reference for analysing various aged and degraded lipid residues in different organic and mineral matrices.     

Nanodiamonds Used as a Platform for Studying Noncovalent Interaction by MALDI‐MS

作为一种新的,易于实现的快速分析方法,纳米金刚石被应用基于基质隔离激光解吸附电离质谱的非共价相互作用的研究中。表面覆盖有“饵分析物”的纳米金刚石被加入到含有“目标分析物”的溶液中,通过离心的方法进行分离,并用水清洗后再利用基质隔离激光解吸附电离质谱进行分析。同时,通过比较加入纳米金刚石前后的溶液的质谱图,亦可得到相关信息。这种平台可应用于分子间非共价相互作用的研究,并可进一步应用于选择性增强的基质隔离激光解吸附电离质谱分析中,一个例子就是表面覆盖聚赖氨酸的纳米金刚石在磷酸化多肽的质谱分析的应用。     

The identification of synthetic homopolymer end groups and verification of their transformations using MALDI‐TOF mass spectrometry

Recent advances in the resolving power of matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) enable the detailed characterization of linear homopolymers, and in particular provide invaluable data for the determination of their end‐group functionalities. With the growing importance of macromolecular coupling reactions in building complex polymer architectures, the ability to accurately monitor end‐group transformations is becoming increasingly important for synthetic polymer chemists. This tutorial demonstrates the application of MALDI‐TOF MS in determining both end‐group functionalities and their transformations for linear homopolymers. Examples of both polycaprolactone and polystyrene are examined, and the strengths and weaknesses of various approaches to data analysis are given. Copyright © 2010 John Wiley & Sons, Ltd.     

Uncovering matrix effects on lipid analyses in MALDI imaging mass spectrometry experiments

The specific matrix used in matrix‐assisted laser desorption/ionization imaging mass spectrometry (MALDI IMS) can have an effect on the molecules ionized from a tissue sample. The sensitivity for distinct classes of biomolecules can vary when employing different MALDI matrices. Here, we compare the intensities of various lipid subclasses measured by Fourier transform ion cyclotron resonance (FT‐ICR) IMS of murine liver tissue when using 9‐aminoacridine (9AA), 5‐chloro‐2‐mercaptobenzothiazole (CMBT), 1,5‐diaminonaphthalene (DAN), 2,5‐Dihydroxyacetophenone (DHA), and 2,5‐dihydroxybenzoic acid (DHB). Principal component analysis and receiver operating characteristic curve analysis revealed significant matrix effects on the relative signal intensities observed for different lipid subclasses and adducts. Comparison of spectral profiles and quantitative assessment of the number and intensity of species from each lipid subclass showed that each matrix produces unique lipid signals. In positive ion mode, matrix application methods played a role in the MALDI analysis for different cationic species. Comparisons of different methods for the application of DHA showed a significant increase in the intensity of sodiated and potassiated analytes when using an aerosol sprayer. In negative ion mode, lipid profiles generated using DAN were significantly different than all other matrices tested. This difference was found to be driven by modification of phosphatidylcholines during ionization that enables them to be detected in negative ion mode. These modified phosphatidylcholines are isomeric with common phosphatidylethanolamines confounding MALDI IMS analysis when using DAN. These results show an experimental basis of MALDI analyses when analyzing lipids from tissue and allow for more informed selection of MALDI matrices when performing lipid IMS experiments.     

Laser desorption postionization for imaging MS of biological material

Vacuum ultraviolet single photon ionization (VUV SPI) is a soft ionization technique that has the potential to address many of the limitations of matrix‐assisted laser desorption/ionization (MALDI) for imaging MS. Laser desorption postionization (LDPI) uses VUV SPI for postionization and is experimentally analogous to a MALDI instrument with the addition of a pulsed VUV light source. This review discusses progress in LDPI‐MS over the last decade, with an emphasis on imaging MS of bacterial biofilms, analytes whose high salt environment make them particularly resistant to imaging by MALDI‐MS. This review first considers fundamental aspects of VUV SPI including ionization mechanisms, cross sections, quantum yields of ionization, dissociation and potential mass limits. The most common sources of pulsed VUV radiation are then described along with a newly constructed LDPI‐MS instrument with imaging capabilities. Next, the detection and imaging of small molecules within intact biofilms is demonstrated by LDPI‐MS using 7.87 eV (157.6 nm) VUV photons from a molecular fluorine excimer laser, followed by the use of aromatic tags for detection of selected species within the biofilm. The final section considers the future prospects for imaging intact biological samples by LDPI‐MS. Copyright © 2010 John Wiley & Sons, Ltd.     

Method development for the analysis of resinous materials with MALDI‐FT‐ICR‐MS: novel internal standards and a new matrix material for negative ion mode

Matrix‐assisted laser desorption/ionization (MALDI) is a mass spectrometry (MS) ionization technique suitable for a wide variety of sample types including highly complex ones such as natural resinous materials. Coupled with Fourier transform ion cyclotron resonance (FT‐ICR) mass analyser, which provides mass spectra with high resolution and accuracy, the method gives a wealth of information about the composition of the sample. One of the key aspects in MALDI‐MS is the right choice of matrix compound. We have previously demonstrated that 2,5‐dihydroxybenzoic acid is suitable for the positive ion mode analysis of resinous samples. However, 2,5‐dihydroxybenzoic acid was found to be unsuitable for the analysis of these samples in the negative ion mode. The second problem addressed was the limited choice of calibration standards offering a flexible selection of m/z values under m/z 1000. This study presents a modified MALDI‐FT‐ICR‐MS method for the analysis of resinous materials, which incorporates a novel matrix compound, 2‐aminoacridine for the negative ion mode analysis and extends the selection of internal standards with m/z <1000 for both positive (15 different phosphazenium cations) and negative (anions of four fluorine‐rich sulpho‐compounds) ion mode. The novel internal calibration compounds and matrix material were tested for the analysis of various natural resins and real‐life varnish samples taken from cultural heritage objects. Copyright © 2017 John Wiley & Sons, Ltd.     

Repeat MALDI MS imaging of a single tissue section using multiple matrices and tissue washes

Matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI MSI) techniques are continually being assessed with a view to improving the quality of information obtained from a given sample. A single tissue section will typically only be analyzed once by MALDI MSI and is then either used for histological staining or discarded. In this study, we explore the idea of repeat analysis of a single tissue section by MALDI MSI as a route toward improving sensitivity, structural characterization, and diversity of detected analyte classes. Repeat analysis of a single tissue section from a fresh frozen mouse brain is investigated with both α-cyano-4-hydroxycinnamic acid (CHCA) and para-nitroaniline (PNA). Repeat analysis is then applied to the acquisition of MALDI MSI and MALDI tandem mass spectrometry imaging employing collision induced dissociation (MS/MS imaging employing CID) from a formalin-fixed mouse brain section. Finally, both lipid and protein data are acquired from the same tissue section via repeat analysis utilizing CHCA, sinapinic acid (SA), and a tissue wash step. PNA was found to outperform CHCA as a matrix for repeat analysis; multiple lipids were identified using MS/MS imaging; both lipid and protein images were successfully acquired from a single tissue section.

Direct screening of herbal blends for new synthetic cannabinoids by MALDI‐TOF MS

Since 2004, a number of herbal blends containing different synthetic compounds mimicking the pharmacological activity of cannabinoids and displaying a high toxicological potential have appeared in the market. Their availability is mainly based on the so‐called “e‐commerce”, being sold as legal alternatives to cannabis and cannabis derivatives. Although highly selective, sensitive, accurate, and quantitative methods based on GC–MS and LC–MS are available, they lack simplicity, rapidity, versatility and throughput, which are required for product monitoring. In this context, matrix‐assisted laser desorption ionization‐time of flight mass spectrometry (MALDI‐TOF MS) offers a simple and rapid operation with high throughput. Thus, the aim of the present work was to develop a MALDI‐TOF MS method for the rapid qualitative direct analysis of herbal blend preparations for synthetic cannabinoids to be used as front screening of confiscated clandestine preparations. The sample preparation was limited to herbal blend leaves finely grinding in a mortar and loading onto the MALDI plate followed by addition of 2 µl of the matrix/surfactant mixture [α‐cyano‐4‐hydroxy‐cinnamic acid/cetyltrimethylammonium bromide (CTAB)]. After drying, the sample plate was introduced into the ion source for analysis. MALDI‐TOF conditions were as follows: mass spectra were analyzed in the range m/z 150–550 by averaging the data from 50 laser shots and using an accelerating voltage of 20 kV. The described method was successfully applied to the screening of 31 commercial herbal blends, previously analyzed by GC–MS. Among the samples analyzed, 21 contained synthetic cannabinoids (namely JWH‐018, JWH‐073, JWH‐081, JWH‐250, JWH‐210, JWH‐019, and AM‐694). All the results were in agreement with GC–MS, which was used as the reference technique. Copyright © 2012 John Wiley & Sons, Ltd.