Investigation of endogenous blood lipids components that contribute to matrix effects in dried blood spot samples by liquid chromatography-tandem mass spectrometry

Supported liquid extraction combined with liquid chromatography tandem mass spectrometry for the quantitative analysis of a TLR7 agonist imiquimod LFX453 in plasma at low picograms per milliliter: Method validation and its application to a pharmacokinetic study in minipig

Sample preparation is essential for low-level compound determination. In the present work, supported liquid extraction (SLE) was used as sample preparation for the low-level determination of a new TLR7 agonist imiquimod compound, LFX453. Samples were extracted on ISOLUTE® SLE 96-well plates using tert-butyl-methyl ether followed by evaporation and dry residue reconstitution with 150 μl of a mixture of 0.1% formic acid in acetonitrile-water (50/50, v/v). Samples were eluted using a flow rate of 0.750 ml/min on a C18 column (50 × 2.1 mm, 2.7 μm) with a mobile phase consisting of 0.1% formic acid in water (A) and 0.1% formic acid in acetonitrile (B). Tandem mass spectrometry was used to analyze the samples in positive mode. The method run time was 6.5 min, and the low limit of quantification was 1.00 pg/ml with 0.100 ml of minipig plasma. Intra-run and inter-run precision and accuracy were within the acceptance criteria at four concentration levels over a concentration ranging from 1.00 to 200 pg/ml. There was no matrix effect and recovery, three freeze-thaw cycles and incurred samples reanalysis were validated. The method was successfully applied for measuring LFX453 in minipig plasma after application on minipig skin.

Dried blood spots in clinical lipidomics: optimization and recent findings

Dried blood spots (DBS) are being considered as an alternative sampling method of blood collection that can be used in combination with lipidomic and other omic analysis. DBS are successfully used in the clinical context to collect samples for newborn screening for the measurement of specific fatty acid derivatives, such as acylcarnitines, and lipids from whole blood for diagnostic purposes. However, DBS are scarcely used for lipidomic analysis and investigations. Lipidomic studies using DBS are starting to emerge as a powerful method for sampling and storage in clinical lipidomic analysis, but the major research work is being done in the pre- and analytical steps and procedures, and few in clinical applications. This review presents a description of the impact factors and variables that can affect DBS lipidomic analysis, such as the type of DBS card, haematocrit, homogeneity of the blood drop, matrix/chromatographic effects, and the chemical and physical properties of the analyte. Additionally, a brief overview of lipidomic studies using DBS to unveil their application in clinical scenarios is also presented, considering the studies of method development and validation and, to a less extent, for clinical diagnosis using clinical lipidomics. DBS combined with lipidomic approaches proved to be as effective as whole blood samples, achieving high levels of sensitivity and specificity during MS and MS/MS analysis, which could be a useful tool for biomarker identification. Lipidomic profiling using MS/MS platforms enables significant insights into physiological changes, which could be useful in precision medicine.

The role of ethanol in fatalities in Jeddah, Saudi Arabia

In Saudi Arabia, alcohol consumption is prohibited by law, but interpreting postmortem ethanol can be complicated by its postmortem production. This study developed and validated a method using headspace gas chromatography with flame ionization detection and liquid chromatography tandem mass spectroscopy to detect ethanol and its polar metabolites (ethyl glucuronide [EtG] and ethyl sulfate [EtS]) in postmortem blood and urine specimens, respectively. All calibration curves were linear with coefficients of determination greater than 0.999. The limits of detection ranged 4.5-5.0mg/dL for ethanol and 0.05-0.06mg/L for EtG and EtS. The limits of quantification were 10.0mg/dL for ethanol and 0.075mg/L for EtG and EtS. Within-run precision was less than 11% for all analytes of interest. Matrix effects for EtG and EtS ranged 3-47%. After excluding matrix effects, analytical recoveries ranged 72-100%. This validated method was then used for routine postmortem forensic toxicology analyses in 592 routine postmortem cases to distinguish between antemortem ethanol consumption and its postmortem microbial formation. Among them, 98 blood samples (17%) were positive for ethanol or its polar metabolites. Thirty-two of these cases (33%) were positive for EtG and EtS and therefore due to antemortem ethanol consumption. The remaining 66 (67%) cases were negative for both EtG and EtS and therefore due to postmortem ethanol synthesis. Because this is the first study to report the problem of alcohol consumption in Saudi Arabia, further studies are essential for validating these findings.