A simple, specific, and economical LC–MS/MS method was investigated for the screening of 43 prescribed antihy-pertensive and related drugs in human urine. The urine samples were simply prepared by diluting and mixing with internal stan-dard before directly introduced to the LC-MS/MS system, which is fast, straightforward, and cost-effective. Fractional factorial, Box-Behnken, and I-optimal design were applied to screen and optimize the mass spectrometric and chromatographic factors. The analysis was carried out on a triple quadrupole mass spectrometer system utilizing multiple reaction monitoring with posi-tive and negative electrospray ionization method. Chromatographic separation was performed on a Thermo Scientific Accucore RP-MS column (50 × 3.0 mm ID., 2.6 µm) using two separate gradient elution programs established with the same mobile phases. Chromatographic separation was performed within 12 min. The optimal method was validated based on FDA guideline. The results indicated that the assay was specific, reproducible, and sensitive with the limit of detection from 0.1 to 50.0 µg/L. The method was linear for all analytes with coefficient of determination ranging from 0.9870 to 0.9981. The intra-assay preci-sion was from 1.44 to 19.87% and the inter-assay precision was between 2.69 and 18.54% with the recovery rate ranges from 84.54 to 119.78% for all drugs measured. All analytes in urine samples were stable for 24 h at 25 o C, and for 2 weeks at -60 o C. The developed method improves on currently existing methods by including larger number of cardiovascular medications and better sensitivity of 12 analytes.
Meldonium is a drug for treating ischemia by expanding the arteries but it can also enhance the performance of sports players. The World Anti-Doping Agency (WADA) has included it in the list of prohibited substances since 2016. Meldonium is one of the challenging substances for anti-doping testing because it is difficult to recover by general liquid-liquid or solid phase extraction due to its permanent charge and high polarity. Therefore, high-performance liquid chromatography (HPLC) is currently used by injecting a diluted urine sample (known as the “dilute-and-shoot” strategy). There is no loss of target compounds in the extraction/cleanup procedure but its high matrix effect could interfere in their separation or detection from the endogenous urinary compounds. We report a single method using high-resolution mass spectrometry that can be used for both screening and confirmation, which follows the “dilute-and-shoot” strategy. In this method, the endogenous compounds’ interfering peaks in the mass spectrum are separated at a high resolution of FWHM 140,000, and the results are suitable for substance detection following the WADA guidelines. The interferences in the obtained mass spectrum of the urine matrix are identified as acetylcholine, lysine, and glutamine by further analysis and database searching. Validation of the method is performed in routine anti-doping testing, and the limit of detection is 50 ng/mL. This method uses simple sample preparation and a general reverse phase HPLC column, and it can be easily applied to other substances.
Amphetamine-type stimulants (ATS) are a group of β-phenethylamine derivatives that produce central nervous sys-tem stimulants effects. The representative ATS are methamphetamine and 3, 4-methylenedioxymethamphetamine (MDMA), and abuse of ATS has become a global problem. Methamphetamine is abused in North America and Asia, while amphetamine and 3, 4-methyl e nedioxy m ethamphetamine (Ecstasy) are abused in Europe and Australia. Methamphetamine is also the most abused drug in Korea. In addition to the conventional ATS, new psychoactive substances (NPS) including phenethylamines and synthetic cathinones, which have similar effects and chemical structure to ATS, continue to spread to the global market since 2009, and more than 739 NPS have been identified. For the analysis of ATS, two tests that have different theoretical principles have to be conducted, and screening tests by immunoassay and confirmatory tests using GC/MS or LC/MS are the global stan-dard methods. As most ATS have a chiral center, enantiomer separation is an important point in forensic analysis, and it can be conducted using chiral derivatization reagents or chiral columns. In order to respond to the growing drug crime, it is necessary to develop a fast and efficient analytical method.
Low-temperature plasma (LTP) ionization is one of the ambient ionization methods typically used in mass spectrom- etry (MS) for fast screening of chemicals with minimal or no sample preparation. In spite of various advantages of LTP ioniza- tion method, including simple instrumentation and in-situ analysis, more general applications of the method are limited due to poor desorption of analytes with low volatilities and low ionization efficiencies in the negative ion mode. In order to overcome these limitations, an ultrasonic vibrator of a commercial hand-held humidifier was interfaced with an LTP ionization source, which generated microdroplets from sample solutions and assisted with LTP ionization. Ionization behaviors of various chemi- cals in microdroplet-assisted LTP (MA LTP) were tested and compared with typical LTP ionization from dried samples applied on a surface. MA LTP efficiently ionized small organic, amino, and fatty acids with low volatilities and high polarities, which were hardly ionized using the standard LTP method. Facile interaction of LTP with ultrafine droplets generated by ultrasonic res- onator allows efficient ionization of relatively non-volatile and polar analytes both in the positive and negative ion modes.
A metabolomics study was conducted to identify urinary biomarkers for breast cancer, using gas chromatographymassspectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS), analyzed by principal components analysis(PCA) as well as a partial least squares-discriminant analysis (PLS-DA) for a metabolic pattern analysis. To find potentialbiomarkers, urine samples were collected from before- and after-mastectomy of breast cancer patients and healthy controls. Androgens, corticoids, estrogens, nucleosides, and polyols were quantitatively measured and urinary metabolic profiles wereconstructed through PCA and PLS-DA. The possible biomarkers were discriminated from quantified targeted metabolites with ametabolic pattern analysis and subsequent screening. We identified two biomarkers for breast cancer in urine, β-cortol and 5-methyl-2-deoxycytidine, which were categorized at significant levels in a student t-test (p-value < 0.05). The concentrations ofthese metabolites in breast cancer patients significantly increased relative to those of controls and patients after mastectomy. Biomarkers identified in this study were highly related to metabolites causing oxidative DNA damage in the endogenous metabolism. These biomarkers are not only useful for diagnostics and patient stratification but can be mapped on a biochemical chartto identify the corresponding enzyme for target identification via metabolomics.
Defective synthesis of the steroid hormones by the adrenal cortex has profound effects on human development andhomeostasis. Due to the time-consuming chromatography procedure combined with mass spectrometry, the matrix-assisted laserdesorption ionization method coupled to the linear ion-trap tandem mass spectrometry (MALDI-LTQ-MS/MS) was developedfor quantitative analysis of 10 adrenal steroids in human serum. Although MALDI-MS can be introduced for its applicability asa high-throughput screening method, it has a limitation on reproducibility within and between samples, which renders poorreproducibility for quantification. For quantitative MALDI-MS/MS analysis, the stable-isotope labeled internal standards wereused and the conditions of crystallization were tested. The precision and accuracy were 3.1~35.5% and 83.8~138.5%, respectively,when a mixture of 10 mg/mL α-cyano-4-hydroxycinnamic acid in 0.2% TFA of 70% acetonitrile was used as the MALDImatrix. The limit of quantification ranged from 5 to 340 ng/mL, and the linearity as a correlation coefficient was higher than0.988 for all analytes in the calibration range. Clinical applications include quantitative analyses of patients with congenital adrenalhyperplasia. The devised MALDI-MS/MS technique could be successfully applied to diagnosis of clinical samples.