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.

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 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.