Advances in sample preparation and HPLC-MS/MS methods for determining amyloid-ß peptide in biological samples: a review.

Alzheimer's disease (AD), a neurological disorder, is a major public health concern and the most common form of dementia. Its typical symptoms include memory loss, confusion, changes in personality, and cognitive impairment, which result in patients gradually losing independence. Over the last decades, some studies have focused on searching for effective biomarkers as early diagnostic indicators of AD. Amyloid-ß (Aß) peptides have been consolidated as reliable AD biomarkers and have been incorporated into modern diagnostic research criteria. However, quantitative analysis of Aß peptides in biological samples remains a challenge because both the sample and the physical-chemical properties of these peptides are complex. During clinical routine, Aß peptides are measured in the cerebrospinal fluid by immunoassays, but the availability of a specific antibody is critical-in some cases, an antibody may not exist, or its specificity may be inadequate, leading to low sensitivity and false results. HPLC-MS/MS has been reported as a sensitive and selective method for determining different fragments of Aß peptides in biological samples simultaneously. Developments in sample preparation techniques (preconcentration platforms) such as immunoprecipitation, 96-well plate SPME, online SPME, and fiber-in-tube SPME have enabled not only effective enrichment of Aß peptides present at trace levels in biological samples, but also efficient exclusion of interferents from the sample matrix (sample cleanup). This high extraction efficiency has provided MS platforms with higher sensitivity. Recently, methods affording LLOQ values as low as 5 pg mL-1 have been reported. Such low LLOQ values are adequate for quantifying Aß peptides in complex matrixes including cerebrospinal fluid (CSF) and plasma samples. This review summarizes the advances in mass spectrometry (MS)-based methods for quantifying Aß peptides and covers the period 1992-2022. Important considerations regarding the development of the HPLC-MS/MS method such as the sample preparation step, optimization of the HPLC-MS/MS parameters, and matrix effects are described. Clinical applications, difficulties related to analysis of plasma samples, and future trends of these MS/MS-based methods are also discussed.

Novel materials as capillary coatings for in-tube solid-phase microextraction for bioanalysis.

In-tube solid-phase microextraction with a capillary column as extraction device can be directly coupled with high-performance liquid chromatography systems (HPLC). The in-tube solid-phase microextraction technique has been continuously developed since it was introduced in 1997. New couplings have also been evaluated on the basis of state-of-the-art HPLC instruments. Different types of capillaries (wall-coated open tubular, porous layer open tubular, sorbent-packed, porous monolithic rods, or fiber-packed) with selective stationary phases (monoliths, magnetic nanoparticles, conducting polymers, restricted access materials, ionic liquids, carbon, deep eutectic solvents, and hybrid materials) have been developed to boost in-tube solid-phase microextraction performance (sorption capacity and selectivity). This technique has been successfully applied to analyze biological samples (serum, plasma, whole blood, hair, urine, milk, skin, and saliva) for therapeutic drug monitoring, to study biomarkers, to detect illicit drugs, to conduct metabolomics studies, and to assess exposure to drugs. This review describes current advances in in-tube solid-phase microextraction extraction devices and their application in bioanalysis.

A column switching ultrahigh-performance liquid chromatography-tandem mass spectrometry method to determine anandamide and 2-arachidonoylglycerol in plasma samples.

This study reports a fast, sensitive, and selective column switching ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method to determine the endocannabinoids (eCBs), anandamide (AEA), and 2-arachidonoylglycerol (2-AG) in plasma samples. This bidimensional system used a restricted access media column (RP-8 ADS, 25 mm × 4 mm × 25 µM) in the first dimension and a core-shell Kinetex C18 (100 mm × 2, 1.7 mm × 1 µM) column in the second dimension, followed by detection in a mass spectrometer triple quadrupole (multiple reactions monitoring mode) operating in the positive mode. RP-8 ADS was used for trace enrichment of eCBs (reverse phase partitioning) and macromolecular matrix size exclusion; the core-shell column was used for the chromatographic separation. The column switching UHPLC-MS/MS method presented a linear range spanning from 0.1 ng mL-1 (LOQ) to 6 ng mL-1 for AEA and from 0.04 ng mL-1 (LOQ) to 10 ng mL-1 for 2-AG. Excluding the LLOQ values, the precision assays provided coefficients of variation lower than 8% and accuracy with relative standard error values lower than 14%. Neither carryover nor matrix effects were detected. This high-throughput column switching method compared to conventional methods is time saving as it involves fewer steps, consumes less solvent, and presents lower LLOQ. The column switching UHPLC-MS/MS method was successfully applied to determine AEA and 2-AG in plasma samples obtained from Alzheimer's disease patients. Graphical abstract A column switching ultra high-performance liquid chromatography-tandem mass spectrometry method using RP-8 ADS column and core shell column to determine endocannabinoids in plasma samples.

Bisphenol A release from orthodontic adhesives measured in vitro and in vivo with gas chromatography.

INTRODUCTION: The objectives of this study were to quantify in vitro the Bisphenol A (BPA) release from 5 orthodontic composites and to assess in vivo the BPA level in patients' saliva and urine after bracket bonding with an orthodontic adhesive system. METHODS: For the in-vitro portion of this study, 5 orthodontic composites were evaluated: Eagle Spectrum (American Orthodontics, Sheboygan, Wis), Enlight (Ormco, Orange, Calif), Light Bond (Reliance Orthodontic Products, Itasca, Ill), Mono Lok II (Rocky Mountain Orthodontics, Denver, Colo), and Transbond XT (3M Unitek, Monrovia, Calif). Simulating intraoral conditions, the specimens were immersed in a water/ethanol solution, and the BPA (ng.g-1) liberation was measured after 30 minutes, 24 hours, 1 day, 1 week, and 1 month by the gas chromatography system coupled with mass spectrometry. Twenty patients indicated for fixed orthodontic treatment participated in the in-vivo study. Saliva samples were collected before bracket bonding and then 30 minutes, 24 hours, 1 day, 1 week, and 1 month after bonding the brackets. Urine samples were collected before bonding and then at 1 day, 1 week, and 1 month after bonding. The results were analyzed statistically using analysis of variance and Tukey posttest, with a significance level of 5%. RESULTS: All composites evaluated in vitro released small amounts of BPA. Enlight composite showed the greatest release, at 1 month. Regarding the in-vivo study, the mean BPA level in saliva increased significantly only at 30 minutes after bonding in comparison with measurements recorded before bonding. CONCLUSIONS: All orthodontic composites released BPA in vitro. Enlight and Light Bond had, respectively, the highest and lowest BPA releases in vitro. The in-vivo experiment showed that bracket bonding with the Transbond XT orthodontic adhesive system resulted in increased BPA levels in saliva and urine. The levels were significant but still lower than the reference dose for daily ingestion.

Recent advances in LC-MS/MS methods to determine endocannabinoids in biological samples: Application in neurodegenerative diseases.

Endocannabinoids (ECs) are endogenous lipid-based retrograde neurotransmitters that bind to cannabinoid receptors [cannabinoid receptor 1 (CB1) and cannabinoid receptor 2 (CB2)]. Many ECs have been characterized; anandamide (AEA) and 2-arachidonoyl glycerol (2-AG) are still considered the primary ECs signaling mediators. Dysregulation of ECs has been implicated in a wide range of pathologies, including neurodegenerative diseases. Understanding how ECs participate in neurological diseases is important to describe the pathology and to establish new treatments. Considering the physicochemical properties of ECs, liquid chromatography coupled to tandem mass spectrometry has become the reference method to determine these endogenous substances, in trace levels, in different biological samples. This review describes the recent advances in LC-MS/MS methods designed to determine ECs in complex biological matrixes. The advantages, limitations, selectivity, matrix effect, and sensitivity associated with each approach are emphasized. This article comprises three sections: (I) sample preparation techniques (conventional, microextraction, and online systems), (II) chromatographic methods (especially LC-MS/MS), and (III) relationship between ECs levels and neurodegenerative diseases.

Pipette tip dummy molecularly imprinted solid-phase extraction of Bisphenol A from urine samples and analysis by gas chromatography coupled to mass spectrometry.

Molecularly imprinted polymers (MIPs) were synthesized and used as sorbent for Bisphenol A (BPA) pipette tip solid-phase microextraction from urine samples and BPA analysis by gas chromatography coupled to mass spectrometry (GC-MS). The MIPs were synthesized by the sol-gel methodology. Aminopropyltriethoxysilane (APTES) and tetraethyl orthosilicate (TEOS) were used as functional monomer and cross-linking reagent, respectively. BPA and tetrabromobisphenol A (TBBPA) were evaluated as template during MIP synthesis. The BPA-based MIP displayed slightly higher extraction efficiency than the TBBPA-based dummy molecularly imprinted polymer (DMIP), but the TBBPA-based DMIP was selected as sorbent to minimize interference from leaked template. Comparison of the TBBPA-based DMIP, BPA-based MIP, and non-imprinted polymer (NIP) extraction efficiencies attested that the TBBPA-based DMIP was selective. The synthesized polymers were characterized by Scanning Electron Microscopy (SEM) and Fourier Transform Infrared spectroscopy (FTIR). The TBBPA-based DMIP was reused for over 100 times, which confirmed its robustness. The developed method was linear from 50 to 500ngmL-1. Precision values had coefficient of variation (CV) ranging from 4 to 14%. The accuracy relative standard deviation values (RSD) varied from -13.6 to 12.3%.

Determination of Drugs in Plasma Samples by High-Performance Liquid Chromatography-Tandem Mass Spectrometry for Therapeutic Drug Monitoring of Schizophrenic Patients.

This work describes the development of a simple, sensitive and selective method based on high-performance liquid chromatography coupled to tandem mass spectrometry (LC-MS-MS) to determine antipsychotics (olanzapine, quetiapine, clozapine, haloperidol and chlorpromazine) along with antidepressants (mirtazapine, paroxetine, citalopram, sertraline, imipramine, clomipramine and fluoxetine), anticonvulsants (carbamazepine and lamotrigine) and anxiolytics (diazepam and clonazepam) in plasma samples obtained from schizophrenic patients. The samples were prepared by protein precipitation. The target drugs were separated on an XSelect SCH C18 column (100 mm × 2.1 mm × 2.5 µm) within 8.0 min by means of gradient elution. The drugs were then detected on a quadrupole tandem mass spectrometer equipped with an electrospray ionization source, operating in the multiple reactions monitoring mode and in the positive ionization mode. The LC-MS-MS method was linear range from subtherapeutic to toxic concentrations with lower limit of quantification values ranged from 0.2 to 5.0 ng mL(-1), precision with coefficient of variation values lower than 12%, and accuracy ranged from 90 to 108%. The developed method enabled successful analysis of the target drugs in plasma samples obtained from 51 schizophrenic patients. Therapeutic drug monitoring revealed that many of the evaluated schizophrenic patients presented altered plasma concentrations of the analyzed drugs. These altered concentrations resulted from pharmacokinetic interactions among the medications prescribed to treat schizophrenia.