Micro-SPE in pipette tips as a tool for analysis of small-molecule drugs in serum

Homemade Pipette Tip Solid-Phase Extraction for the Simultaneous Determination of 40 Drugs of Abuse in Urine by Liquid Chromatography–Tandem Mass Spectrometry

Pipette tip solid-phase extraction facilitates the handling of low-volume samples and organic solvents in order to achieve more environmentally friendly pre-treatment sample techniques. The use of pipette tip extraction was examined for the quick and simple determination of a heterogeneous group of 40 drugs of abuse and some of their metabolites in urine by liquid chromatography coupled to tandem mass spectrometry. Several parameters were studied and optimized, including those which can affect extraction efficiencies, such as the amount of sorbent and the volumes and number of aspirating/dispensing cycles of the sample and organic solvents. The linear range of this method was between the quantification limit and 75 or 100 ng mL−1. Detection limits between 0.025 and 0.500 ng mL−1 and quantification limits from 0.100 to 1.500 ng mL−1 were achieved, which are adequate to determine the studied compounds in urine from drug users. Finally, in order to prove its suitability in toxicological and forensic analyses, the method was successfully applied to 22 urine specimens from women who were starting a detoxification program. Cocaine was the most frequently detected substance, as its presence or the presence of its main metabolite was found in 86% of the analyzed samples.

Determination of Antiviral Drugs and Their Metabolites Using Micro-Solid Phase Extraction and UHPLC-MS/MS in Reversed-Phase and Hydrophilic Interaction Chromatography Modes

Two new ultra-high performance liquid chromatography (UHPLC) methods for analyzing 21 selected antivirals and their metabolites were optimized, including sample preparation step, LC separation conditions, and tandem mass spectrometry detection. Micro-solid phase extraction in pipette tips was used to extract antivirals from the biological material of Hanks balanced salt medium of pH 7.4 and 6.5. These media were used in experiments to evaluate the membrane transport of antiviral drugs. Challenging diversity of physicochemical properties was overcome using combined sorbent composed of C₁₈ and ion exchange moiety, which finally allowed to cover the whole range of tested antivirals. For separation, reversed-phase (RP) chromatography and hydrophilic interaction liquid chromatography (HILIC), were optimized using extensive screening of stationary and mobile phase combinations. Optimized RP-UHPLC separation was carried out using BEH Shield RP18 stationary phase and gradient elution with 25 mmol/L formic acid in acetonitrile and in water. HILIC separation was accomplished with a Cortecs HILIC column and gradient elution with 25 mmol/L ammonium formate pH 3 and acetonitrile. Tandem mass spectrometry (MS/MS) conditions were optimized in both chromatographic modes, but obtained results revealed only a little difference in parameters of capillary voltage and cone voltage. While RP-UHPLC-MS/MS exhibited superior separation selectivity, HILIC-UHPLC-MS/MS has shown substantially higher sensitivity of two orders of magnitude for many compounds. Method validation results indicated that HILIC mode was more suitable for multianalyte methods. Despite better separation selectivity achieved in RP-UHPLC-MS/MS, the matrix effects were noticed while using both chromatographic modes leading to signal enhancement in RP and signal suppression in HILIC.

Determination of Intraprostatic and Intratesticular Androgens

Androgens represent the main hormones responsible for maintaining hormonal balance and function in the prostate and testis. As they are involved in prostate and testicular carcinogenesis, more detailed information of their active concentration at the site of action is required. Since the introduction of the term intracrinology as the local formation of active steroid hormones from inactive precursors of the adrenal gland, mainly dehydroepiandrosterone (DHEA) and DHEA-S, it is evident that blood circulating levels of sex steroid hormones need not reflect their actual concentrations in the tissue. Here, we review and critically evaluate available methods for the analysis of human intraprostatic and intratesticular steroid concentrations. Since analytical approaches have much in common in both tissues, we discuss them together. Preanalytical steps, including various techniques for separation of the analytes, are compared, followed by the end-point measurement. Advantages and disadvantages of chromatography-mass spectrometry (LC-MS, GC-MS), immunoanalytical methods (IA), and hybrid (LC-IA) are discussed. Finally, the clinical information value of the determined steroid hormones is evaluated concerning differentiating between patients with cancer or benign hyperplasia and between patients with different degrees of infertility. Adrenal-derived 11-oxygenated androgens are mentioned as perspective prognostic markers for these purposes.

Unambiguous determination of farnesol and tyrosol in vaginal fluid using fast and sensitive UHPLC-MS/MS method

The new ultra-high performance liquid chromatography method with tandem mass spectrometry detection (UHPLC-MS/MS) has been optimized to allow fast, selective, and high-throughput analysis of two Candida albicans quorum sensing molecules (QSM), farnesol and tyrosol. The problem of the presence of the interference in the samples and system was successfully solved by careful optimization of chromatographic conditions. Charged hybrid stationary phase modified with pentafluorophenyl group and optimized gradient elution provided adequate separation selectivity and peak shapes. The impurity was identified as dibutyl phthalate and had the same m/z ions as farnesol leading to an important interference on selected reaction monitoring channel. Two different types of biological matrices originating from vaginal fluid, supernatant and sediment, were analysed. Micro-solid phase extraction in pipette tips was optimized for the selective isolation of QSM from the supernatant. The insufficient retention of farnesol on the extraction sorbent was improved when 1% of organic solvent was added prior to extraction, while the retention of tyrosol was only possible when using combined C8 and polymer sorbent type. Strong retention of farnesol had to be solved by increasing elution solvent strength and volume up to 600 μL. However, this approach did not allow the pretreatment of sediment samples due to the sorbent clogging. Therefore, our previously developed protein precipitation method was modified and validated to analyse the sediments. New developed UHPLC-MS/MS method provided suitable accuracy and precision for the determination of QSM in vaginal fluid while using only 50 μL sample volume and two different sample preparation methods.

Fully automated method based on on-line molecularly imprinted polymer solid-phase extraction for determination of lovastatin in dietary supplements containing red yeast rice

A fully automated method for the determination of lovastatin in dietary supplements containing red yeast rice has been developed. It uses a sequential injection analysis system combined with solid-phase extraction applying highly selective molecularly imprinted polymer sorbent. A miniaturized column for on-line extraction was prepared by packing 4.5 mg of the sorbent in a 5.0 × 2.5-mm-i.d. cartridge, which was used in the flow manifold. Sequential injection analysis manifold enabled all steps of lovastatin extraction and continuous spectrophotometric detection at 240 nm. A limit of detection of 60 μg g^-1, a limit of quantitation of 200 μg g^-1, and a linear calibration range of 200-2000 μg g^-1 were achieved. Intra-day and inter-day precision values (RSD) were ≤ 6.7% and ≤ 4.9%, respectively, and method recovery values of spiked red yeast rice extracts at 200, 1000, and 2000 μg g^-1 concentration levels were 82.9, 95.2, and 87.7%. Our method was used for determination of lovastatin lactone in four dietary supplements containing red yeast rice as a natural source of lovastatin, also known as monacolin K. The extracted samples were subsequently analyzed by the reference UHPLC-MS/MS method. Statistical comparison of results (F test, t test, α = 0.05) obtained by both methods did not reveal significant difference. A substantial advantage of the new automated approach is high sample throughput thanks to the analysis time of 7.5 min, miniaturization via down-scaling the extraction column, and smaller sample and solvent consumption, as well as reduced generation of waste. Graphical abstract ᅟ.