Semiquantitative Screening of THC Analogues by Silica Gel TLC with an Ag(I) Retention Zone and Chromogenic Smartphone Detection.

With the ever-evolving cannabis industry, low-cost and high-throughput analytical methods for cannabinoids are urgently needed. Normally, (potentially) psychoactive cannabinoids, typically represented by Δ9-tetrahydrocannabinol (Δ9-THC), and nonpsychoactive cannabinoids with therapeutic benefits, typically represented by cannabidiol (CBD), are the target analytes. Structurally, the former (tetrahydrocannabinolic acid (THCA), cannabinol (CBN), and THC) have one olefinic double bond and the latter (cannabidiolic acid (CBDA), cannabigerol (CBG), and CBD) have two, which results in different affinities toward Ag(I) ions. Thus, a silica gel thin-layer chromatography (TLC) plate with the lower third impregnated with Ag(I) ions enabled within minutes a digital chromatographic separation of strongly retained CBD analogues and poorly retained THC analogues. The resolution (Rs) between the closest two spots from the two groups was 4.7, which is almost 8 times higher than the resolution on unmodified TLC. After applying Fast Blue BB as a chromogenic reagent, smartphone-based color analysis enabled semiquantification of the total percentage of THC analogues (with a limit of detection (LOD) of 11 ng for THC, 54 ng for CBN, and 50 ng for THCA when the loaded volume is 1.0 µL). The method was validated by analyzing mixed cannabis extracts and cannabis extracts. The results correlated with those of high-performance liquid chromatography with ultraviolet detection (HPLC-UV) (R2 = 0.97), but the TLC approach had the advantages of multi-minute analysis time, high throughput, low solvent consumption, portability, and ease of interpretation. In a desiccator, Ag(I)-TLC plates can be stored for at least 3 months. Therefore, this method would allow rapid distinction between high and low THC varieties of cannabis, with the potential for on-site applicability.

Synthesis of a poly(sulfobetaine-co-polyhedral oligomeric silsesquioxane) hybrid monolith via an in-situ ring opening quaternization for use in hydrophilic interaction capillary liquid chromatography.

An in-situ approach is described for synthesis of poly(sulfobetaine-co-polyhedral oligomeric silsesquioxane) [poly(sulfobetaine-co-POSS)] that can be used in a hybrid monolithic column as a hydrophilic liquid chromatography (HILIC) stationary phase. Synthesis involves (a) radical polymerization of octa(propyl methacrylate)-polyhedral oligomeric silsesquioxane (MA-POSS) and organic monomers such as dimethylaminopropyl methacrylate or vinyl imidazole, and (b) in-situ ring-opening quaternization between 1,4-butane sultone and the organic monomers. The sulfobetaine groups are generated in-situ monolith. This obviates the need for synthesis of sulfobetaine monomer previously. The pore size and permeability of the material can be tuned by using a binary porogenic system (polyethyleneglycol 600 and acetonitrile) and via the composition of the polymerization mixture. The optimized hybrid monolith owns its merits to the presence of POSS and sulfobetaine groups with good mechanical stability, the lack of residual silanol groups, and adequate hydrophilicity. The column filled with the monoliths was evaluated as a stationary phase for HILIC. Several kinds of polar compounds (including nucleosides, bases, phenols, aromatic acids and amides) were separated by using mobile phases with high organic solvent fractions in capillary liquid chromatography. Graphical abstractAn in-situ approach is described for synthesis of poly(sulfobetaine-co-polyhedral oligomeric silsesquioxane) hybrid monolithic column for use in hydrophilic liquid chromatography. The optimized monolith owns good mechanical stability, the lack of residual silanol groups and adequate hydrophilicity. Baseline separation of several kinds of polar compounds is achieved on the column. MA-POSS: octa(propyl-methacrylate) polyhedral oligomeric silsesquioxane; DMAEMA: dimethylaminoethyl methacrylate; AIBN: azodiisobutyronitrile. Poly(DMABS-co-POSS): poly(N-(4-sulfobutyl)-N-methacryloxypropyl- N,N-dimethylammonium-betaine-co-polyhedral oligomeric silsesquioxane).

Ionization of glycans from alkali metal salt-impregnated paper.

Ambient ionization of glycans is simply and efficiently achieved by spraying from an alkali metal salt-impregnated paper surface. Monosaccharides, oligosaccharides and ring glycans easily form abundant alkali metal adduct ions, and give simple and clean high-quality mass spectra. The enhancement is specific for glycans, compared to a wide variety of non-glycan compounds present in a matrix. In addition, molecular weight of unknown glycans can be further identified based on the ion mass difference of various alkali metal adduct ions from a certain compound when using a mixed salt-impregnated paper containing five cation salts. Successful determination of glycans and glycoconjugates in plant extracts, honey, blood and urine demonstrates the practicability of this approach to complicated matrices, especially biological matrices.

Rapid analysis of anionic and cationic surfactants in water by paper spray mass spectrometry.

The discharge of wastewater containing surfactants and other industrial pollutants is contaminating the world's water resources which should be taken seriously. This paper describes a paper spray mass spectrometric (PS-MS) method for rapid and quantitative analysis of anionic and cationic surfactants in water samples. Eight cationic surfactants and four anionic surfactants can be simultaneously determined in positive or negative mode without sample pretreatment and chromatographic separation. The PS-MS analysis time was only 10 s. Under optimized conditions, the method presented a suitable linear range (1-80 µg mL-1, linear regression coefficients (R2) higher than 0.995 for cationic surfactants, R2 higher than 0.990 for anionic surfactants), a low limit of detection (0.05-0.35 µg mL-1 for cationic surfactants and 0.20-0.35 µg mL-1 for anionic surfactants), and satisfactory recovery values (97.3-106.1%). The method validation indicated that the method precision and accuracy were satisfactory. The results demonstrated that PS-MS is especially suitable for the high-throughput analysis of surfactants in water samples.

Electrochemical quartz crystal microbalance study of covalent tethering of carboxylated thiol to polyaniline for electrocatalyzed oxidation of ascorbic acid in neutral aqueous solution.

The electrochemical quartz crystal microbalance (EQCM) was used to study the electrosyntheses and electrochemical properties of two kinds of polyaniline (PANI)-thiol composite films in aqueous solutions, which were prepared by covalent binding of a thiol to the oxidized forms of PANI (PANI(post)-thiol, protocol A), and electropolymerization of aniline in the presence of a thiol (PANI(poly)-thiol, protocol B), respectively. The thiols involved were mercaptosuccinic acid (MSA), thioglycolic acid (TGA) and beta-mercaptoethanol (ME). The PANI(post)-thiol binding processes were monitored in situ with the EQCM, giving molar binding ratios (r, thiol vs. aniline unit of the polymer) of ca. 0.50 at saturation for these thiols. Both PANI(post)-thiol and PANI(poly)-thiol composite films from the carboxylated thiols showed a controllable electroactivity of the PANI moiety in neutral even weakly alkaline phosphate buffer solutions (PBS), with maximum electroactivity roughly at r = 0.11 for PANI(post)-MSA or at r = 0.21 for PANI(post)-TGA. The PANI-thiol interaction was also supported by experiments of scanning electron microscopy, electrochemical surface plasmon resonance, Fourier transform infrared spectroscopy and ultraviolet-visible spectroscopy, and the interaction mechanism is briefly discussed. The PANI(post)-thiol and PANI(poly)-thiol composite films from the carboxylated thiols effectively electrocatalyzed the oxidation of ascorbic acid in pH = 7.3 PBS, and the PANI(post)-thiol exhibited electrocatalytic activity higher than the relevant PANI(poly)-thiol under our experimental conditions. The covalent anchoring of anionic thiol groups on the PANI backbone to prepare electroactive PANI in neutral solutions is conceptually new and may be extended to the development of new functional materials from many other conducting polymers and thiols for wide applications in catalysis, biosensing, molecular electronics, and so on.

Fluoro-functionalized paper-based solid-phase extraction for analysis of perfluorinated compounds by high-performance liquid chromatography coupled with electrospray ionization-tandem mass spectrometry.

Fluoro-functionalized paper was prepared and applied in solid phase extraction (SPE) for the analysis of trace-level perfluorinated compounds (PFCs). The proposed fluoro-functionalized paper-based solid-phase extraction (Fp-SPE) exhibits significant advantages for sample preparation, such as the biodegradability of paper-based adsorbent, simple manipulation and low cost. Owing to the fluorous affinity, the Fp-SPE technique with high sensitivity and high selectivity is more suitable for the selective enrichment of fluorine-containing molecules from the background of non-fluorinated organic compounds in a real water sample. Combined with high-performance liquid chromatography coupled with electrospray ionization-tandem mass spectrometry analysis (HPLC-MS/MS), the linear range of the PFCs, including perfluorobutyric acid (PFBA), perfluorooctanic acid (PFOA), perfluorooctane sulfonic acid (PFOS), and perfluorodecanoic acid (PFDA), was 0.20-5.0 ng/L with the limits of detection (LOD) ranging from 0.04-0.05 ng/L and the limits of quantification (LOQ) ranging from 0.15-0.20 ng/L. The method was then applied to the analysis of tap water, river water and waste water samples. The results of the actual sample analysis are consistent with that by reverse phase SPE (RP-SPE).

Rapid quantitative analysis of ginkgo flavonoids using paper spray mass spectrometry.

In this work, a method for the rapid and reliable analysis of ginkgo flavonoids was developed by using paper spray mass spectrometry (PS-MS) assisted by microwave-assisted hydrolysis (MAH). Kaempferol-D4, quercetin-D5, and isorhamnetin-D3 were used as internal standards (IS). Samples analyses were completed by simply treating with extraction, MAH, dilution, and quantitative analysis by PS-MS. Because of the absence of HPLC separation, the PS-MS analysis time was less than 20 s. The linear ranges of kaempferol, quercetin and isorhamnetin were 1.7-86, 1.7-86, and 1.3-68 mg/L, respectively, with linear coefficients (R2) of 0.9993-0.9998. The detection limits (LODs) were 0.1, 0.1, and 0.2 mg/L. Limits of quantifications (LOQs) were all less than 0.6 mg/L. Compared with HPLC results, there are no obvious differences. It can be concluded that the PS-MS method with isotope IS is accurate for the rapid analysis of ginkgo flavonoids in extracts and related products.

Rapid analysis of benzoic acid and vitamin C in beverages by paper spray mass spectrometry.

A paper spray mass spectrometry (PS-MS) method has been developed for the rapid quantification of benzoic acid (BA) and vitamin C (VC) in beverages. Using BA-d5 as an internal standard (IS) to analyze BA and VC, the calibration curves ranged from 0.3 to 100 µg/mL for BA and 1 to 100 µg/mL for VC, the linearity was 0.9996 for BA and 0.9973 for VC. The limits of detection (LODs) and limits of quantitation (LOQs) were 0.1 µg/mL and 0.3 µg/mL for BA, 0.3 µg/mL and 1 µg/mL for VC, respectively. The recovery ranged from 91.1 to 106.7% for BA, 92.6 to 108.2% for VC. Compared with HPLC, there is no substantial difference in the quantification of BA and VC in samples, the accuracy was 95.7-102.2%, and the run time is far less than that of the HPLC method. The results indicated that PS-MS is a rapid, environmentally friendly and high-throughput method for the quantification of BA and VC.

Immobilization of enzymes at high load/activity by aqueous electrodeposition of enzyme-tethered chitosan for highly sensitive amperometric biosensing.

Electrodeposition has been so widely used to immobilize biomacromolecules, and it is always an important topic to increase the load and activity of the immobilized biomacromolecules. We report here on a new, simple and rather universal method for the highly efficient immobilization of enzymes by aqueous electrodeposition of enzyme-tethered chitosan (CS) for sensitive amperometric biosensing. Glucose oxidase (GOx) is chosen here to examine the proposed protocol in detail. GOx was crosslinked to CS with low-concentration glutaraldehyde (GA, 0.080 wt%), and the electroreduction of added H(2)O(2) increased the electrode-surface pH and triggered the electrodeposition of a GOx-GA-CS composite film. The GOx-GA-CS electrodeposition was monitored by an electrochemical quartz crystal microbalance and is theoretically discussed based on an electrogenerated base-to-acid titration model. The prepared first-generation enzyme electrode (CS-GA-GOx/Pt(nano)/Au) exhibits a current sensitivity as high as 102 microA mM(-1) cm(-2) at 0.70 V vs SCE, being 13 times that of the CS-GOx/Pt(nano)/Au prepared similarly but without the GOx-CS precrosslinking. UV-vis spectrophotometric determination of the GOx remains in the supernatant liquids after pH-induced CS precipitation suggested a high enzyme load in the GOx-GA-CS film, and amperometric measurements suggested a negligible decrease in the enzymatic activity of GOx after its reaction with the low-concentration GA. Also, the proposed protocol works well for the precrosslinking manner of 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide/N-hydroxysulfosuccinimide activation, the water-electroreduction-triggered CS electrodeposition, the second-generation biosensing mode, a 5.0-microm-radius Pt ultramicroelectrode, and immobilization of alkaline phosphatase for phenyl phosphate biosensing. The proposed protocol of pretethering the target biomacromolecules to the electrodeposition precusor for immobilization of the biomacromolecule at high load/activity is recommended for wide applications.