Rapid Derivatization of Phenolic and Oxime Hydroxyl with Isonicotinoyl Chloride under Aqueous Conditions and Its Application in LC-MS/MS Profiling Multiclass Steroids

An ultra-fast method for therapeutic drug monitoring of tacrolimus, sirolimus and cyclosporine A

Therapeutic drug monitoring for immunosuppressants is a widely conducted global practice. Traditionally, the pretreatment of whole blood involves the use of metal ions combined with organic solvents. However, this method requires multiple reagent additions, repeated opening, closing, and vortexing of vials, and it also leads to heavy metal pollution. Given the typically large sample volumes, optimizing this process is crucial for increasing throughput, reducing the workload of clinical staff, and lowering costs. We discovered that treating whole blood with a 60 to 75% acetonitrile (ACN) solution effectively releases tacrolimus, sirolimus, and cyclosporine A while simultaneously precipitating protein. This allowed us to significantly simplify the pretreatment process to just adding 65% ACN solution containing internal standards, manually shaking for 20 s, and centrifuging for 2 min. The resulted supernatant can then be directly analyzed by mass spectrometry. Method validation demonstrated that the new approach can accurately quantify tacrolimus in the range of 0.64 to 37.5 ng/ml, cyclosporine A at 12 to 976 ng/ml, and sirolimus at 0.99 to 43.4 ng/ml. A comparison of paired samples showed the new method to be perfectly consistent with the classical method, with 293 out of 300 results deviating by no more than ± 20%. This study has greatly simplified the workflow, increased throughput, and resolved environmental concerns for therapeutic drug monitoring of immunosuppressants, including tacrolimus, sirolimus, and cyclosporine A, in whole blood samples. The proposed method is a viable replacement for existing protocols and deserves to be adopted in all clinical laboratories with relevant practical needs globally.

Quantitative analysis of cannabinoids and metabolites in oral fluid by volumetric absorptive microsampling combined with UHPLC-HRMS

With recent evolution of cannabis legalization around the world and multiplication of cannabis derived products, identifying and qualifying cannabis consumption has a proven interest. Although blood, plasma, and urine are common matrices widely used in toxicology laboratories, oral fluid presents specific advantages. In the context of doping tests, addiction consultation or roadside checks, where other matrices are impractical to collect or can be adulterated, oral fluid is a promising matrix that allows a non-invasive, rapid, and monitored self-sampling. However, available devices required a consequent volume of oral fluid, more than 250 µL, sometimes difficult to collect. We present here a fully optimized quantitative method for seven cannabinoids, including four metabolites, in oral fluid, Δ9-tetrahydrocannabinol, 11-hydroxy-Δ9-tetrahydrocannabinol and 11-nor-9-carboxy-Δ9-tetrahydrocannabinol; cannabidiol, 7-hydroxy and 7-carboxycannabidiol; and cannabinol. After self-collection of 20 µL using an accurate and precise volumetric absorptive microsampling device (VAMS®), cannabinoids were derivatized with 2-fluoro-1-methylpyridinium p-toluenesulfonate to increase sensitivity. The successive steps of the proposed method, including biosampling, 1 h sample preparation with derivatization, and acquisition by ultrahigh-performance liquid chromatography coupled to high-resolution mass spectrometry, were fully optimized. A limit of quantification of 0.5 ng/mL (≈10 pg per sampling) was thus targeted, adapted to the legal threshold required by the authorities and to clinical monitoring. Applied to six cannabis consumers, the proposed method made it possible to quantify in 20 µL oral fluid samples, Δ9-tetrahydrocannabinol ranging from 0.5 to 6236 ng/mL, cannabidiol from 0.6 to 190 ng/mL and cannabinol from 0.5 to 118 ng/mL.

Advancing towards practice: A novel LC-MS/MS method for detecting retinol in dried blood spots

BACKGROUND

To date, clinical laboratories face challenges in quantifying retinol from DBS samples. Disputes arise throughout the whole detection process, encompassing the storage condition, the release strategy as well as the selection of internal standards.

METHODS

We incubated DBS with ascorbic acid solution. Then, retinol-d4 in acetonitrile was introduced to incorporate isotopic internal standard and promote protein precipitation. Afterward, sodium carbonate solution was added to ionize cytochromes (such as bilirubin), which amplified the difference of their hydrophobicity to retinol. Subsequently, cold-induced phase separation could be facilitated to separate retinol from the impurities. In the end, the upper layer was injected for LC-MS/MS analysis.

RESULTS

By comparing the detected retinol content in whole blood and DBS samples prepared from the same volume, we confirmed the established pretreatment was capable to extract most of retinol from DBS (recovery >90 %). Thereafter, we verified that within DBS, retinol possessed satisfying stability without antioxidation. Indoor-light exposure and storage duration would not cause obvious degradation (<10 %). Following systematic validation, the established method well met the criteria outlined in the relevant guidelines. After comparing with detected DBS results to the paired plasma samples, 54 out of 60 met the acceptance limit for cross-validation of ±20 %.

CONCLUSIONS

We realized precise quantification of retinol from one 3.2 mm DBS disc. By circumventing conventional antioxidation, liquid-liquid/solid-phase extraction and organic solvent evaporation, the pretreatment could be completed within 15 min consuming only minimal amounts of low-toxicity chemicals (ascorbic acid, acetonitrile, and sodium carbonate). We expect this contribution holds the potential to significantly facilitate the evaluation of patients' vitamin A status by using DBS samples in the future.

Online Charge-Generation Derivatization by Electrochemical Radical Cations of Thianthrene: Mass Spectrometry Imaging of Estrogens in Biological Tissues

Estrogens play a significant role in endocrinology and oncology. Although separation methods coupled with mass spectrometry (MS) have emerged as a powerful tool for studying estrogens, imaging the spatial distributions of estrogens is crucial but remains challenging due to its low endogenous concentration and poor ionization efficiency. Charge-generation derivatization, such as N-alkylpyridinium quaternization and S-methyl thioetherification, represents a method wherein neutral molecules involving analytes and derivatization reagents undergo chemical reactions to establish permanent charges directly onto the analytes to improve detection sensitivity. Here, we developed a novel derivatization reagent, thianthrene (TT), which enabled oxidization to radical cations ([TT]•+) using an electrochemical method and completed the online charge-generation derivatization of estrogens on a mass spectrometry imaging platform. In this strategy, [TT]•+ can efficiently and selectively derivatize estrogens via an electrophilic aromatic substitution reaction. Results indicated that derivatization with [TT]•+ can significantly enhance imaging sensitivity (3 orders of magnitude), enabling the visualization of estrogen and its metabolites in ovarian and breast tissues. Furthermore, a higher mass intensity of these estrogens was captured in breast para-cancerous tissues than in cancerous tissues, which might provide estrogens spatial dimension information for further research on the initiation and progression of breast cancer.

Dispel some mist on circulating biopterins: measurement, physiological interval and pathophysiological implication

BACKGROUND AND AIMS

Biopterins, including tetrahydrobiopterin (BH4), dihydrobiopterin (BH2), and biopterin (B), were crucial enzyme cofactors in vivo. Despite their recognized clinical significance, there remain notable research gaps and controversies surrounding experimental outcomes. This study aims to clarify the biopterins-related issues, including analytical art, physiological intervals, and pathophysiological implications.

MATERIALS AND METHODS

A novel LC-MS/MS method was developed to comprehensively profile biopterins in plasma, utilizing chemical derivatization and cold-induced phase separation. Subsequently, apparently healthy individuals were enrolled to investigate the physiological ranges. And the relationships between biopterins and biochemical indicators were analyzed to explore the pathophysiological implications.

RESULTS

The developed method was validated as reliable for detecting biopterins across the entire physiological range. Timely anti-oxidation was found to be essential for accurate assessment of biopterins. The observed overall mean ± SDs levels were 3.51 ± 0.94, 1.54 ± 0.48, 2.45 ± 0.84 and 5.05 ± 1.14 ng/mL for BH4, BH2, BH4/BH2 and total biopterins. The status of biopterins showed interesting correlations with age, gender, hyperuricemia and overweight.

CONCLUSION

In conjunction with proper anti-oxidation, the newly developed method enables accurate determination of biopterins status in plasma. The observed physiological intervals and pathophysiological implications provide fundamental yet inspiring support for further clinical researches.

Accurate Clinical Detection of Vitamin D by Mass Spectrometry: A Review

Vitamin D deficiency is thought to be associated with a wide range of diseases, including diabetes, cancer, depression, neurodegenerative diseases, and cardiovascular and cerebrovascular diseases. This vitamin D deficiency is a global epidemic affecting both developing and developed countries and therefore qualitative and quantitative analysis of vitamin D in a clinical context is essential. Mass spectrometry has played an increasingly important role in the clinical analysis of vitamin D because of its accuracy, sensitivity, specificity, and the ability to detect multiple substances at the same time. Despite their many advantages, mass spectrometry-based methods are not without analytical challenges. Front-end and back-end challenges such as protein precipitation, analyte extraction, derivatization, mass spectrometer functionality, must be carefully considered to provide accurate and robust analysis of vitamin D through a well-designed approach with continuous control by internal and external quality control. Therefore, the aim of this review is to provide a comprehensive overview of the development of mass spectrometry methods for vitamin D accurate analysis, including emphasis on status markers, deleterious effects of biological matrices, derivatization reactions, effects of ionization sources, contribution of epimers, standardization of assays between laboratories.

Differentiation of steroid isomers by steroid analogues adducted trapped ion mobility spectrometry-mass spectrometry

Steroids are one of the important indicators of health and disease. However, due to the high similarity of steroid structures, there are several potential obstacles in the differentiation of steroids, especially for their isomers. Herein, we described a trapped ion mobility spectrometry-mass spectrometry (TIMS-MS) approach based on the steroid analogue adduction for isomer-specific identification of steroids. The application of dexamethasone (DEX) to form heterodimers with steroids enhanced the separation of their isomers in TIMS. Two isomer pairs including 17-hydroxyprogesterone/11-deoxycorticosterone and androsterone/epiandrosterone were successfully separated as the heterodimers with DEX by TIMS. The stability of DEX-adducted heterodimers is comparable with steroid dimers. Owing to the high separation efficiency and stability, the relative quantification of steroid isomers was demonstrated with the proposed method.

Rapid LC-MS/MS detection of 25-hydroxyvitamin D in dried blood spots

BACKGROUND

The detection of 25-hydroxyvitamin D (25OHD) from dried blood spots (DBS) has been widely studied. However, the existing pretreatment methods suffer from limitations in terms of throughput (usually exceeding 2 h), complexity (involving liquid-liquid extraction or solid-phase extraction), and contamination (including multiple steps of organic solvent evaporation).

RESULTS

We first released 25OHD from DBS samples by 50% acetonitrile solution through ultrasonication. Subsequently, the cold-induced phase separation technique was introduced for in-situ concentration and purification. Afterward, the PTAD derivatization of 25OHD was performed directly, profiting from the high acetonitrile content in the concentrated solution. In the end, the resulting solution was submitted to LC-MS/MS for quantification. The established LC-MS/MS methodology possessed favorable analytical performance, possessing lower limit of quantification of 1 ng/mL pointing to plasma, accuracy of 86.8-110.1% and imprecision of 5.4-16.8%. Method comparison with plasma samples demonstrated that over 93% of the detections met the acceptance limit for cross-validation of ±20%.

SIGNIFICANCE AND NOVELTY

The novel sample preparation can be finished within 15 min and eliminated the traditional steps of extraction and organic solvent evaporation. Based on this high-throughput, reliable and applicable LC-MS/MS method, the detection of 25OHD in DBS samples can be better achieved for clinical patients and researchers with relevant demands.