Pressure-assisted capillary electrochromatography with electrospray ionization-mass spectrometry based on silica-based monolithic column for rapid analysis of narcotics

Green Assessment of Chromatographic Methods Used for the Analysis of Four Methamphetamine Combinations with Commonly Abused Drugs

Numerous agents with anxiolytic or stimulant effects have the potential to be overused, and their misuse is associated with serious side effects. In Saudi Arabia, the estimated percentage of Saudis who abuse drugs is around 7–8% and the age range is 12–22 years. Methamphetamine, captagon, tramadol, heroin, and cannabis/cannabinoids have been proven to be the most commonly abused drugs in Saudi Arabia, with methamphetamine being at the top of the list. The present study focuses on the chromatographic analytical methods used for the analysis of methamphetamine in combination with commonly abused drugs, aiming to point out the greenest among them. These mixtures have been chosen as they are analyzed periodically and frequently in criminal evidence and forensic medicine. Therefore, the chances of hazards for analysts and the environment are high if the mixtures are not handled appropriately. This study aims to compare 23 chromatographic methods used for the analysis of methamphetamine mixtures in four major combinations, and to assess their greenness by using three greenness assessment tools, namely, NEMI, ESA and AGREE, to recommend the greenest analytical method. The NEMI results were proven to have low discriminating abilities and, accordingly, the comparisons are based on ESA and AGREE scores. The analysis results show that the safest methods with the most eco-friendly results (based on ESA and AGREE) are the GC-MS method proposed by Mohammed et al. to analyze methamphetamine and captagon mixtures (ESA = 79 and AGREE = 0.57), the UHPLC–MS-MS method proposed by Busardò et al. to analyze methamphetamine and cannabis/cannabinoid mixtures (ESA = 78 and AGREE = 0.57), the LC-MS method proposed by Herrin et al. to analyze methamphetamine and tramadol mixtures (ESA = 81 and AGREE = 0.56), and the LC-MS method proposed by Postigo-et al to analyze methamphetamine and heroin mixtures (ESA = 76 and AGREE = 0.58).

An underestimated technique. Does pressurized and pressure-assisted capillary electrochromatography have potential in drug and pharmacological-active compounds analysis?

Pharmaceutical analysis guarantees patient safety all over the world. Thus, continuous development of existing analytical techniques is still very important. Pressurized capillary electrochromatography and pressure-assisted capillary electrochromatography are hybrid separation techniques that combine the selectivity of liquid chromatography and the high separation efficiency of capillary electrophoresis. They use a smaller amount of reagents and samples, hence, reducing the total cost of analysis. Therefore they have found application in a number of pharmaceutical and biomedical analysis. This review article focuses on the use and importance of pressurized and pressure-assisted capillary electrochromatography in pharmaceutical and biomedical analysis, taking into account types of detectors and capillaries used. Despite the fact that pressurized capillary electrochromatography and pressure assisted capillary electrochromatography offer many possibilities and have been available for over a dozen years, they are still underdevelopment and not fully explored.

Quantitative analysis of microcystin variants by capillary electrophoresis mass spectrometry with dynamic pH barrage junction focusing

Dynamic pH junction is an online focusing method in CE based on the electrophoretic mobility difference of analytes in the sample matrix and the background electrolyte. An advantage of this method over the conventional CE is that the sensitivity can be significantly improved. By injecting a long sample plug in the capillary and focusing the analytes at the pH boundary between the background electrolyte and sample matrix, the LOD can be improved by 10-100 folds. The dynamic pH junction method can be easily coupled with ESI-MS. In this work, we used this method for the analysis of microcystins (MCs). The detection limits and dynamic ranges were studied. The separation was optimized by adjusting the injection time, and concentrations and pH values of the background electrolyte. The optimization of analyte focusing leads to enhanced detection response compared to conventional injections, achieving 200-400 fold higher averaged peak heights for four microcystin (MC) variants. More importantly, this method was successfully used for the quantitative analysis of microcystins (MCs) in crude algae samples from natural water bodies, making it promising for practical applications.

Monolithic alkylsilane column: A promising separation medium for oligonucleotides by ion-pair reversed-phase liquid chromatography

In this paper, a monolithic octadecylsilane column and particle-packed octadecylsilane columns were used to investigate the retention behaviors of oligonucleotides by ion-pair reversed-phase liquid chromatography (IP-RPLC). Results showed that, with same base composition, hairpin oligonucleotides always had weaker retention than corresponding random coil oligonucleotides on the monolithic column, but not on the particle-packed columns. In addition, the linear correlation between the retention factor k of oligonucleotides and the reciprocal of temperature (1/T), especially for hairpins, was relatively weaker on the particle-packed columns, as compared to the correlation on the monolithic column. The correlation between k and 1/T became weaker with decreasing particle size of the particle-packed columns. Moreover, results revealed that the overall retention order on the particle-packed column with small particles (3 μm) differed greatly from that on the monolithic column. In contrast, the retention order on the 10 μm particle-packed column was very close to that on the monolithic column. From the above, we inferred that oligonucleotides could keep their primary conformations unchanged when passing through the monolithic column, attributed to the special pore structures of the monolith. However, the conformations of oligonucleotides were suppressed or even destroyed when oligonucleotides passed through the particle-packed columns. This because the narrow and tortuous channels created by the stacked stationary phase particles could lead to more complex and unequable retention behaviors. Therefore, the monolithic column exhibited better retention regularity for oligonucleotides of secondary structure especially for hairpins than the particle-packed columns. It is noteworthy that the monolith-based IP-RPLC opens an intriguing prospect in accurately elucidating the retention behaviors of oligonucleotides.

Monoliths in capillary electrochromatography and capillary liquid chromatography in conjunction with mass spectrometry

Here, we have reviewed separation studies utilizing monolithic capillary columns for separation of compounds preceding MS analysis. The review is divided in two parts according to the used separation method, namely CEC and capillary LC (cLC). Based on our overview, monolithic CEC-MS technique have been more focused on the syntheses of highly specialized and selective separation phase materials for fast and efficient separation of specific types of analytes. In contrast, monolithic cLC-MS is more widely used and is often employed, for instance, in the analysis of oligonucleotides, metabolites, and peptides and proteins in proteomic studies. While poly(styrene-divinylbenzene)-based and silica-based monolithic capillaries found their place in proteomic analyses, the other laboratory-synthesized monoliths still wait for their wider utilization in routine analyses. The development of new monolithic materials will most likely continue due to the demand of more efficient and rapid separation of increasingly complex samples.

Determination of stimulants and narcotics as well as their in vitro metabolites by online CE-ESI-MS

A simple, rapid and sensitive CE-ESI-MS method for the simultaneous analysis of seven stimulants and narcotics (amphetamine, ephedrine, methadone, pethidine, tetracaine, codeine and heroin) was developed. The CE-ESI-MS experimental conditions were optimized as follows: 20 mmol/L ammonium acetate with pH 9.0 as running buffer, the separation voltage of 22 kV and the sheath liquid of isopropanol/water (1:1 v/v) containing 7.5 mmol/L acetic acid with 3.0 μL/min flow rate. Under the optimized conditions, the stimulants and narcotics were well separated within 4.6 min using a 70-cm length fused-silica capillary (50 μm id). The detection limits (S/N=3) of the CE-ESI-MS analysis were in the range of 0.40-1.0 ng/mL. Method repeatability of intra-day and inter-day was satisfactory. The recoveries obtained from the analysis of spiked urine samples were between 84.1 and 108%. The developed method was successfully applied for the simultaneous analysis of methadone, pethidine and codeine and their in vitro metabolites.

CEC-ESI ion trap MS of multiple drugs of abuse

This article describes a method for the separation and determination of nine drugs of abuse in human urine, including amphetamines, cocaine, codeine, heroin and morphine. This method was based on SPE on a strong cation exchange cartridge followed by CEC-MS. The CEC experiments were performed in fused silica capillaries (100 microm x 30 cm) packed with a 3 mum cyano derivatized silica stationary phase. A laboratory-made liquid junction interface was used for CEC-MS coupling. The outlet capillary column was connected with an emitter tip that was positioned in front of the MS orifice. A stable electrospray was produced at nanoliter per minute flow rates applying a hydrostatic pressure (few kPa) to the interface. The coupling of packed CEC columns with mass spectrometer as detector, using a liquid junction interface, provided several advantages such as better sensitivity, low dead volume and independent control of the conditions used for CEC separation and ESI analysis. For this purpose, preliminary experiments were carried out in CEC-UV to optimize the proper mobile phase for CEC analysis. Good separation efficiency was achieved for almost all compounds, using a mixture containing ACN and 25 mM ammonium formate buffer at pH 3 (30:70, v/v), as mobile phase and applying a voltage of 12 kV. ESI ion-trap MS detection was performed in the positive ionization mode. A spray liquid, composed by methanol-water (80:20, v/v) and 1% formic acid, was delivered at a nano-flow rate of approximately 200 nL/min. Under optimized CEC-ESI-MS conditions, separation of the investigated drugs was performed within 13 min. CEC-MS and CEC-MS(2) spectra were obtained by providing the unambiguous confirmation of these drugs in urine samples. Method precision was determined with RSDs values <or=3.3% for retention times and <or=16.3% for peak areas in both intra-day and day-to-day experiments. LODs were established between 0.78 and 3.12 ng/mL for all compounds. Linearity was satisfactory in the concentration range of interest for all compounds (r(2)>or=0.995). The developed CEC-MS method was then applied to the analysis of drugs of abuse in spiked urine samples, obtaining recovery data in the range 80-95%.

[Recent advances in capillary electrochromatography and its coupling techniques]

As a novel micro-separation technique, capillary electrochromatography (CEC) has the merits of high efficiency, high selectivity, high resolution and rapid analysis. However, the small-volume injection manipulated in capillary dimensions poses a great challenge for detectors in achieving high sensitivity. Currently, one of the major researches into CEC involves the development of some sensitive detection modes. The general introduction, which includes the historical perspectives and the principles of CEC, is briefly described. The recent advances about CEC coupled with various detectors and its applications in the separation of complex samples are summarized. A total of 141 references are reviewed.