Review of the Use of Liquid Chromatography-Tandem Mass Spectrometry in Clinical Laboratories: Part II-Operations

Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is increasingly utilized in clinical laboratories because it has advantages in terms of specificity and sensitivity over other analytical technologies. These advantages come with additional responsibilities and challenges given that many assays and platforms are not provided to laboratories as a single kit or device. The skills, staff, and assays used in LC-MS/MS are internally developed by the laboratory, with relatively few exceptions. Hence, a laboratory that deploys LC-MS/MS assays must be conscientious of the practices and procedures adopted to overcome the challenges associated with the technology. This review discusses the post-development landscape of LC-MS/MS assays, including validation, quality assurance, operations, and troubleshooting. The content knowledge of LC-MS/MS users is quite broad and deep and spans multiple scientific fields, including biology, clinical chemistry, chromatography, engineering, and MS. However, there are no formal academic programs or specific literature to train laboratory staff on the fundamentals of LC-MS/MS beyond the reports on method development. Therefore, depending on their experience level, some readers may be familiar with aspects of the laboratory practices described herein, while others may be not. This review endeavors to assemble aspects of LC-MS/MS operations in the clinical laboratory to provide a framework for the thoughtful development and execution of LC-MS/MS applications.

Review of the Use of Liquid Chromatography-Tandem Mass Spectrometry in Clinical Laboratories: Part I-Development

The process of method development for a diagnostic assay based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) involves several disparate technologies and specialties. Additionally, method development details are typically not disclosed in journal publications. Method developers may need to search widely for pertinent information on their assay(s). This review summarizes the current practices and procedures in method development. Additionally, it probes aspects of method development that are generally not discussed, such as how exactly to calibrate an assay or where to place quality controls, using examples from the literature. This review intends to provide a comprehensive resource and induce critical thinking around the experiments for and execution of developing a clinically meaningful LC-MS/MS assay.

Pharmacokinetic and excretion study of eight active constituents in rat by LC-MS/MS after oral administration of the Toddalia asiatica extract

Toddalia asiatica L.，a significant medicinal plants in the family Rutaceae, has been applied to treat rheumatoid diseases for decades. Its pharmacological activities are mainly contributed to the existence of generous coumarins and alkaloids, however, the pharmacokinetics of Toddalia asiatica L. remains unclear. A high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was established for the simultaneous determination of four coumarin, three alkaloid and one flavonoid (hesperidin, nitidine chloride, chelerythrine, toddalolactone, isopimpinellin, pimpinellin, bergapten and dictamnine) in rat plasma, feces and urine. Chromatographic separation was accomplished on an Agilent ZORBAX SB-C18 column (2.1 × 150 mm, 5 μm) with acetonitrile (containing 0.1% formic acid) and 5 mmol/L ammonium formate aqueous for gradient elution. The correlation coefficient greater than 0.9925 reflected the excellent linearity of the analytical response. The lower limits of quantification were 30.0, 10.0, 10.0, 30.0, 5.0, 10.0, 2.5 and 2.5 ng/mL for hesperidin, nitidine chloride, chelerythrine, toddalolactone, isopimpinellin, pimpinellin, bergapten and dictamnine, separately. The intra- and inter-day precision were less than 12.7%, and the accuracy was between -11.8% and 12.9%. In summary, this study is the first time to study the pharmacokinetics and excretion of T.asiatica extract after oral administration, which may provide a scientific basis for its clinical applications.

Validation of a HPLC method for quantification of midazolam in rat plasma: Application during a Maytenus ilicifolia-drug interaction study

Midazolam (MDZ) is routinely employed as a marker compound of cytochrome P450 3A (CYP3A) activity. Despite the many HPLC-UV methods described to quantify MDZ in plasma, all of them use acetonitrile (ACN) or a mixture of methanol-isopropanol as organic solvent of the mobile phase. Since the ACN shortage in 2008, efforts have been made to replace this solvent during HPLC analysis. A simple, sensitive, accurate and repeatable HPLC-UV method (220 nm) was developed and validated to quantify MDZ in rat plasma using methanol instead. The method was applied during a herb-drug interaction study involving Maytenus ilicifolia, a Brazilian folk medicine used to treat gastric disorders. Plasma samples were alkalinized and MDZ plus alprazolam (internal standard) were extracted with diethyl ether. After solvent removal, the residue was reconstituted with methanol-water (1:1). The analyte was eluted throughout a C₁₈ column using sodium acetate buffer (10 mm, pH 7.4)-methanol (40:60, v/v). The precision at the lower limit of quantification never exceeded 19.40%, and 13.86% at the higher levels of quality control standards, whereas the accuracy ranged from -19.81 to 14.33%. The analytical curve was linear from 50 to 2,000 ng/ml. The activity of the hepatic CYP3A enzymes was not affected by the extract.

New LC-MS/MS method with single-step pretreatment analyzes fat-soluble vitamins in plasma and amniotic fluid

Fat-soluble vitamins (FSVs), A, D, and E, are components of prenatal vitamin care. Previously, limited evidence existed to explain on a molecular level how maternal FSV supplementation affects the fetus during pregnancy. We developed a simplified LC-MS/MS method to simultaneously detect FSVs in maternal plasma (MP) and amniotic fluid (AF); we used this approach to investigate the correlation between FSV levels in these two matrices. With this method, we circumvented frequently used liquid-liquid extraction or solid-phase extraction methods and, instead, used simple protein precipitation with acetonitrile for sample preparation. This method displayed satisfactory linearity, intra- and inter-day imprecision, and accuracy. We validated the consistency with standard reference material 972a and 968f certification. In analysis of MP and AF samples from 50 pregnant women in the second trimester, concentrations of retinol, 25-hydroxyvitamin D3 [25(OH)D3], and α-tocopherol (reflecting vitamins A, D, and E, respectively) were lower in AF than in MP. Significant positive correlations existed between MP and AF for 25(OH)D3 (r = 0.667; P < 0.001) and retinol (r = 0.393; P = 0.005), but not for α-tocopherol (r = 0.145, P > 0.05). This novel LC-MS/MS method shows prominent applicability for FSV detection and the observed correlations contribute to research on fetal development.

A rapid UPLC-MS/MS assay for the simultaneous measurement of fluconazole, voriconazole, posaconazole, itraconazole, and hydroxyitraconazole concentrations in serum

BACKGROUND

Triazole antifungals are essential to the treatment and prophylaxis of fungal infections. Significant pharmacokinetic variability combined with a clinical need for faster turnaround times has increased demand for in-house therapeutic drug monitoring of these drugs, which is best performed using mass spectrometry-based platforms. However, technical and logistical obstacles to implementing these platforms in hospital laboratories have limited their widespread utilization. Here, we present the development and validation of a fast and simple ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method to measure fluconazole, voriconazole, posaconazole, itraconazole, and hydroxyitraconazole in human serum suitable for incorporation into a hospital clinical laboratory.

METHODS

Serum samples (20 µL) were prepared using protein precipitation in the presence of deuterated internal standards. Chromatographic separation was accomplished using reversed phase UPLC and analysis was performed using positive-mode electrospray ionization and collision-induced dissociation MS.

RESULTS

Total analytical run time was 3 min. All analytes demonstrated linearity (r2>0.998) from 0.1 to 10 µg/mL (1-100 µg/mL for fluconazole), acceptable accuracy and precision (%DEV<15% and %CV<15% at all levels tested), suitable stability under relevant storage conditions, and correlated well with reference laboratory results.

CONCLUSIONS

A simple and rapid UPLC-MS/MS method for monitoring multiple triazole antifungals was developed with a focus on the needs of hospital laboratories. The assay is suitable for clinical utilization and management of patients on these medications.

LC of high to moderately polar basic drugs in urine with water and detergent, and direct injection

BACKGROUND

Micellar LC was first proposed as a 'green' mode using mobile phases of water and surfactant. However, in most procedures a small amount of organic solvent is required to decrease the retention to convenient values. Results & methodology: Mixed micellar mobile phases prepared with both cationic (sodium dodecyl sulphate) and nonionic surfactant (Brij-35) modulate the retention of high to moderately polar basic drugs to practical times, eliminating the need of organic solvent. While the mobile phase is continuously recycled through the system, the stationary phase performance is maintained after repetitive injection of the samples.

DISCUSSION & CONCLUSION

Through an extensive validation, the approach is shown to be appropriate to determine these drugs in urine samples without previous pretreatment.

Simultaneous determination of three phenylethanoid glycosides from Callicarpae Caulis et Folium in rat plasma by LC–MS/MS and its application to PK study

Background:Callicarpae Caulis et Folium (CCF) is a traditional Chinese medicine usually used for hemostasis in clinics. In this study, a novel LC–MS/MS method was developed and validated for the simultaneous quantification of three phenylethanoid glycosides in rat plasma (verbascoside, forsythoside B and poliumoside), which are the major bioactive compounds of CCF; MS was operated in negative mode. Results: This method was linear between 5.2 and 1010 ng/ml for poliumoside, 7.0 and 420 ng/ml for forsythoside B and 2.60 and 260.0 ng/ml for verbascoside. The MS/MS ion transitions monitored were m/z 769.4→160.5, m/z 755.3→593.3, m/z 623.1→160.5 and m/z 179.0→133.6 for poliumoside, forsythoside B, verbascoside and caffeic acid (IS), respectively. Linearity, accuracy, precision and extraction recovery of three analytes were all satisfactory. Conclusion: The method developed was sensitive, specific and rapid. It has been successfully applied in a PK study of three phenylethanoid glycosides after a single oral administration of CCF extract to rats.

Minimizing matrix effects while preserving throughput in LC–MS/MS bioanalysis

Background: Phospholipids are known to cause matrix effects in LC–MS analysis and are not effectively removed by one of the most common method of sample preparation: organic solvent protein precipitation. The objective of this research is to minimize phospholipid interferences chromatographically. Results: In this article we examine several chromatographic approaches and highlight the method we developed that allows for the rapid gradient separation of model drug molecules from phospholipids. Conclusion: The new approach (which utilizes a mixture of methanol and acetonitrile as the organic mobile phase on a 2.1 × 20 mm C18 column) minimized phospholipids-related matrix effects in the analysis of plasma samples prepared by protein precipitation and is suitable for high-throughput bioanalysis in drug discovery.

Development and validation of a quantitative assay based on tandem mass spectrometry

Many routine hospital and clinical research assays have relied upon immunoassay procedures to achieve sensitive measurements of a range of important analytes. Some of the methods have been developed in-house but increasingly commercial kits and automated analysers have become commonplace. The accuracies of these methods are under question in health care. Mass spectrometry (MS) is potentially a more accurate technique with the ability to demonstrate specificity. An introduction of the basic analytical aspects of liquid chromatography (LC)–MS/MS leads on to the validation of the method before general use. LC coupled with MS and tandem mass spectrometry (MSn) is being adopted in a number of hospital laboratories for the quantitative analysis of a number of analytes from physiological matrices, but standards for development and validation of such assays are not easily available. Most assays can be regarded as in-house methods and herein may lay the failure so far for mass spectrometric methods to improve quality of results between laboratories for an analyte using the same technology. Manufacturers are taking on board the experience of clinical laboratories with kits containing all or most of the disposable items and reagents. A number of documents and guidelines have been consulted. These documents are expensive to purchase, are often very long and not easy to read. This review highlights the specific requirements for introduction of a tandem mass spectrometric test for small molecules into a routine hospital laboratory. A number of experiments need to be planned and executed in order to describe a new quantitative method in terms of selectivity, accuracy, imprecision, sensitivity and stability. The introduction of a quantitative method based on tandem MS requires careful validation. This review has distilled out important points from a number of key documents in order to provide a working validation guideline for clinical laboratories. In a supplementary file a working document for assembling the assay validation is proposed.