Routine Analysis Research Articles

Optimisation of a Microwave Synthesis of Silver Nanoparticles by a Quality by Design Approach to Improve SERS Analytical Performances

A major limitation preventing the use of surface-enhanced Raman scattering (SERS) in routine analyses is the signal variability due to the heterogeneity of metallic nanoparticles used as SERS substrates. This study aimed to robustly optimise a synthesis process of silver nanoparticles to improve the measured SERS signal repeatability and the protocol synthesis repeatability. The process is inspired by a chemical reduction method associated with microwave irradiation to guarantee better controlled and uniform heating. The innovative Quality by Design strategy was implemented to optimise the different parameters of the process. A preliminary investigation design was firstly carried out to evaluate the influence of four parameters selected by means of an Ishikawa diagram. The critical quality attributes were to maximise the intensity of the SERS response and minimise its variance. The reaction time, temperature and stirring speed are critical process parameters. These were optimised using an I-optimal design. A robust operating zone covering the optimal reaction conditions (3.36 min–130 °C–600 rpm) associated with a probability of success was modelled. Validation of this point confirmed the prediction with intra- and inter-batch variabilities of less than 15%. In conclusion, this study successfully optimised silver nanoparticles by a rapid, low cost and simple technique enhancing the quantitative perspectives of SERS.

Carbonate reservoir characterization and permeability modeling using Machine Learning ـــ a study from Ras Fanar field, Gulf of Suez, Egypt

AbstractPredicting facies and petrophysical properties along and between wells is challenging in carbonate reservoir modeling. In the Nullipore carbonate reservoir, Ras Fanar field, depositional and long-term diagenetic processes result in a high degree of heterogeneity and complex distribution of facies, which in turn affect the reservoir quality. This provides a significant obstacle to building accurate geological models. This study integrates thin sections, routine core analyses, and well logging data to overcome such difficulties and model the Nullipore carbonate facies and permeability. The detailed petrographic analysis revealed the existence of seven microfacies in the reservoir, which are summed up into three facies associations (FAs), each of which represents a specific reservoir rock type (RRT): (1) supratidal FA, (2) intertidal FA, and (3) shallow subtidal FA. The three FAs were correlated with the gamma-ray logs to create facies logs for the studied wells, which were further populated via the Truncated Gaussian Simulation method. Cross-validation was used to evaluate the model's accuracy. The analysis of the available core data infers that the three RRTs are prospective and have a wide permeability distribution. However, RRT3 constitutes the best reservoir quality. The sedimentological analysis revealed that the long-term diagenetic events, involving the dolomitization of limestone and the dissolution of allochems have a major role in improving the pore connectivity and permeability of the reservoir. Fracture characterization discloses that fractures play a significant role in fluid storage and migration. Three Machine Learning (ML) models, including Adaptive boosting (AdaBoost), Gradient Boosting (GB), and Extreme Gradient Boosting (XGB), were developed to integrate the RRTs, porosity, and permeability to improve permeability prediction. Statistical analysis revealed that the XGB model outperforms other models and exhibits the highest prediction performance. The present study provides further insights into the characterization and modeling of facies and permeability of complex carbonate reservoirs. It can be applied in similar geological settings to better interpretation of depositional and diagenetic controls on reservoir quality assessment and aid in the field development plan.

Commentary: Core Descriptor Sets Using Consensus Methods Support 'Table One' Consistency.

Inconsistent reporting of patient characteristics in clinical research hampers reproducibility and limits analysis opportunities. This paper proposes condition-specific ‘Core Descriptor Sets’(CDSs) comprising key factors like demographics, disease severity, comorbidities, and prognosis to standardise Table 1 reporting. Development entails stakeholder involvement, systematic identification of descriptors, value rating, and consensus-building using multiple Delphi rounds. Final agreement comes at an expert meeting. Benefits include easier cross-study comparison for example through individual patient meta-analysis, facilitated by comparison of consistently reported individual data rather than group level analysis. This may also support routine data analyses, subgroup and risk identification, and reduced research waste. CDSs describe cohorts thoroughly while minimising research burden. They are intended to enable improved clinical characterisation, personalisation, reproducibility, data sharing and knowledge building.

Application of untargeted liquid chromatography-mass spectrometry to routine analysis of food using three-dimensional bucketing and machine learning

For the detection of food adulteration, sensitive and reproducible analytical methods are required. Liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS) is a highly sensitive method that can be used to obtain analytical fingerprints consisting of a variety of different components. Since the comparability of measurements carried out with different devices and at different times is not given, specific adulterants are usually detected in targeted analyses instead of analyzing the entire fingerprint. However, this comprehensive analysis is desirable in order to stay ahead in the race against food fraudsters, who are constantly adapting their adulterations to the latest state of the art in analytics. We have developed and optimized an approach that enables the separate processing of untargeted LC‑HRMS data obtained from different devices and at different times. We demonstrate this by the successful determination of the geographical origin of honey samples using a random forest model. We then show that this approach can be applied to develop a continuously learning classification model and our final model, based on data from 835 samples, achieves a classification accuracy of 94% for 126 test samples from 6 different countries.

High throughput LC-MS/MS method for the quantitation of baclofen in human plasma by solid phase extraction using 96 well plate format

Oral baclofen is indicated for the treatment of spasticity resulting from multiple sclerosis and is very useful for the relief of flexor spasms and concomitant pain, muscular rigidity, and clonus. It can also be used to treat patients with spinal cord injuries and other spinal cord diseases. In present work, a sensitive and high throughput LC-MS/MS method was developed and validated to estimate Baclofen in Human plasma. The developed LC-MS/MS method was sensitive enough to detect Baclofen in human plasma with a high degree of accuracy and precision, using Baclofen-d4 as an internal standard. Using BDS Hypersil C8 5µm, 100 X 4.6mm column and a mobile phase consisting of 2mM Ammonium formate with 0.02% v/v formic acid: Acetonitrile (85:15 v/v) was used to achieve best chromatographic separation. A flow rate of 1 mL/min was used to optimize the run time of 3.2 min. Plasma sample extraction was performed by Solid Phase extraction using 96 well plates. The developed bioanalytical method was validated successfully. This high throughput bioanalytical method developed and validated can be applied to routine sample analysis. this method can accommodate 80 study samples in single run excluding the CC and QC samples. Since the method uses 96 well plate formate it gives flexibility in assigning the CC, QC, and study samples in fixed well before the initiation of the process which in turn avoids the risk of sample mix up during processing. The method validation results were found to be within the acceptance range. It can be concluded that the developed high throughput LC-MS/MS method is sensitive enough to measure Baclofen up to an LOOQ 5.023 ng/mL in Human plasma and cater to high throughput analysis using 96 well plates.

Development and Validation of a High-Performance Liquid Chromatography Diode Array Detector Method to Measure Seven Neonicotinoids in Wheat

Neonicotinoids (NEOs), used as insecticides against aphids, whiteflies, lepidopterans, and beetles, have numerous detrimental impacts on human health, including chronic illnesses, cancer, infertility, and birth anomalies. Monitoring the residues in food products is necessary to guarantee public health and ecological balance. The present work validated a new method to measure seven neonicotinoid insecticides (acetamiprid ACT, clothianidin CLT, dinotefuran DNT, imidacloprid IMD, nitenpyram NTP, thiacloprid TCP, and thiamethoxan THT) in wheat. The analytical procedure was based on simple and fast wheat sample cleanup using solid-phase extraction (SPE) to remove interferents and enrich the NEOs, alongside the NEOs’ separation and quantification by reverse-phase chromatography coupled with a diode array detector (DAD). The validation process was validated using the accuracy profile strategy, a straightforward decision tool based on the measure of the total error (bias plus standard deviation) of the method. Our results proved that, in the future, at least 95% of the results obtained with the proposed method would fall within the ±15% acceptance limits. The test’s cost-effectiveness, rapidity, and simplicity suggest its use for determining the levels of acetamiprid, clothianidin, dinotefuran, imidacloprid, nitenpyram, thiacloprid, and thiamethoxam in routine analyses of wheat.

A Review Article on Analytical Method on Vericiguat

Vericiguat is a novel oral soluble guanylate cyclase (sGC) stimulator used in the treatment of chronic heart failure, aimed at reducing hospitalization rates and improving cardiac function by inducing vasodilation. The analysis of Vericiguat in pharmaceutical formulations and biological fluids requires robust and precise analytical methods. High-Performance Liquid Chromatography (HPLC) and UV-Visible Spectrophotometry are the primary techniques employed for this purpose due to their high specificity, sensitivity, and rapid analysis capabilities. This review discusses the development, validation, and application of these analytical methods for Vericiguat. Various HPLC methods have been developed, utilizing different columns, mobile phases, and detection wavelengths to ensure the accurate quantification of Vericiguat in bulk and tablet dosage forms. UV-Visible spectrophotometry has also been employed, offering a simpler and cost-effective alternative for routine analysis. The review consolidates the key parameters and findings of these methods, highlighting their advantages and suitability for the effective analysis of Vericiguat, thereby contributing to quality assurance in pharmaceutical development and therapeutic monitoring

Development and Validation RP-HPLC Method for Estimation of Antidiabetic Drugs in Pharmaceutical Dosage Form

This study details the development and validation of an RP-HPLC method for estimating Canagliflozin and Metformin in pharmaceutical dosage forms. Canagliflozin, an SGLT2 inhibitor, and Metformin, an antihyperglycemic agent, were obtained from Arti Drug Pvt. Ltd. Marketed formulation Invokamet was sourced locally. Chromatographic separation was achieved on a C18 column (250 x 4.6 mm, 5 µm) using a mobile phase of Methanol: Water (80:20) with 0.1% ortho phosphoric acid at a 1.0 ml/min flow rate and detection at 254 nm. The retention times for Canagliflozin and Metformin were 8.183 min and 3.633 min, respectively. Method validation parameters included system suitability, accuracy, precision, and robustness. System suitability tests confirmed adequate resolution and repeatability. Accuracy was evaluated through recovery studies at 80%, 100%, and 120% concentration levels, yielding satisfactory results. Precision was demonstrated with intra-day and inter-day % RSD values below 2. Robustness was assessed by varying mobile phase composition and flow rate, showing consistent retention times and tailing factors. The method proved selective, accurate, precise, and robust, with a short run time, facilitating rapid quantification of samples. It is suitable for routine quality control analysis of Canagliflozin and Metformin in pharmaceutical formulations

Rate of graft retear is higher in over-the-top superior capsular reconstruction for massive posterosuperior rotator cuff tears with subscapularis tear.

To compare side-to-side superior capsular reconstruction (SCR) with over-the-top SCR in terms of functional outcomes, pain relief and allograft survival rates. Patients who had undergone arthroscopic dermal allograft SCR for massive irreparable rotator cuff tears and clinical follow-up for ≥2 years were recruited. All patients underwent postoperative assessment with routine radiographic analysis for acromiohumeral distances, ultrasound imaging 1 and 3 months after SCR and magnetic resonance imaging (MRI) at least 12 months after SCR. The outcome measures were visual analogue scale (VAS), American Shoulder and Elbow Surgeons (ASES), Constant and Single Assessment Numeric Evaluation (SANE) scores. SCR was performed in 56 patients including side-to-side SCR in 32 and over-the-top SCR in 24. Postoperative MRI showed that the grafts were intact in 46 patients (82.1%; 26 who underwent side-to-side SCR and 20 who underwent over-the-top SCR). The proportion of nonhealing grafts in the over-the-top group was significantly higher with concomitant subscapularis tears (60% vs. 5.3%; p = 0.02). VAS scores and functional outcomes improved postoperatively in both groups and postoperative VAS (1.4 vs. 1.7; n.s.), Constant (74.8 vs. 76.0; n.s.), mean ASES (87.4 vs. 89.1; n.s.) and mean SANE (81.7 vs. 84.3; n.s.) scores did not differ significantly. For massive rotator cuff tears, over-the-top and side-to-side SCR achieve similar pain relief and functional improvement, and the rate of healing allografts is high. However, over-the-top SCR is not recommended for massive posterosuperior rotator cuff tears with repairable subscapularis tendon tears due to a higher nonhealing rate. Level III.

Smart Chemometric‑Assisted Spectrophotometric Approaches for Simultaneous Quantification of Tertiary Combination Recommended for COVID-19 Supportive Treatments with Their Greenness Assessment.

There is an increasing interest of scientific community in developing innovative methodologies for their analysis needs within green analytical chemistry framework. UV spectrophotometry is one of the most promising eco-friendly methods, which is integrated with advanced chemometric tools to enhance the selectivity of the analysis of complex mixtures with severe overlapped signals. Simultaneous determination of a triple-combination of pseudoephedrine hydrochloride (PSE), carbinoxamine maleate (CRX), and paracetamol (PAR) using an artificial intelligence system and multivariate calibration methods. This combination is recently recommended for COVID-19 home-treated patients as part of a symptomatic treatment. Namely, the suggested models are: Artificial Neural Networks, Partial Least Squares, and Principal Component Regression. The proposed algorithms were optimized and developed with the aid of a five-level, three-factor experimental design. The investigated methods were applied over the concentration range of 100-180 μg/mL, 18-16 μg/mL, and 4-12 μg/mL for PSE, CRX, and PAR, respectively. The models validation results demonstrated excellent recoveries (around 98 to 102%), signaling the approaches outstanding resolution capacity for the cited compounds in the presence of common excipients. The outcomes of the studied methods were statistically compared to the official approaches, and no significant difference was found. The suggested models were efficiently employed to determine the selected drugs in their combined tablets without any initial separation steps. The impact of these methods on the environment was evaluated via greenness tools, namely; National Environmental Method Index, Raynie and Driver's green assessment method, analytical Eco-Scale, Green Analytical Procedure Index, and Analytical Greenness Metric. Green chemometric quality assessment of PSE, CRX, and PAR in their pure and pharmaceutical dosage forms. The established approaches are innovative, sustainable, smart, fast, selective, and cost-effective. These models are potential green nominees for routine analysis of the investigated mixture in quality control laboratories.

Automation and standardisation of a quantitative multiplex PCR assay using PCR.Ai.

BackgroundWe previously undertook a prospective clinical study to evaluate PCR.Ai’s (www.pcr.ai) accuracy and impact when automating the manual data-analysis and quality control steps associated with routine clinical pathogen testing using a non-quantitative multiplex quantitative real-time PCR (qPCR). In this study we demonstrated 100% concurrence between our manual routine analysis method and PCR.Ai. This paper expands the evaluation of PCR.Ai’s (www.pcr.ai) accuracy and impact using a multiplex quantitative real-time PCR (qPCR). ObjectivesWe evaluated the impact of PCR.Ai when used as the final interpretation/verification step for routine in-house multiplex quantitative qPCR tests for CMV, EBV and adenovirus from blood samples for a total of 1,350 interpretations. Study DesignWe compared PCR.Ai to our existing manual interpretation, to determine accuracy and hands on time savings. Results and ConclusionsThere was 100% concurrence between validated CMV, EBV and adenovirus detection and quantitation by our manual routine analysis method and PCR.Ai. Furthermore, there were significant routine savings with PCR.Ai of 63minutes/ run. Our conclusion is that for quantitative tests PCR.Ai is a highly accurate time-saving tool that reduces complexity of qPCR analysis and hence the need for specialists and hands-on time. It demonstrated capabilities to enable us to get results out more quickly with lower costs and less risk of errors.

Supplementation of vitamin E as an addition to a commercial renal diet does not prolong survival of cats with chronic kidney disease

BackgroundThe aim of this double-blind, placebo-controlled study was to investigate the effect of vitamin E supplementation as an addition to a commercial renal diet on survival time of cats with different stages of chronic kidney disease (CKD). In addition, we were interested whether vitamin E supplementation affects selected oxidative stress and clinical parameters. Thirty-four cats with CKD and 38 healthy cats were included in the study. Cats with CKD were classified according to the IRIS Guidelines; seven in IRIS stage 1, 15 in IRIS stage 2, five in IRIS stage 3 and seven in IRIS stage 4. Cats with CKD were treated according to IRIS Guidelines. Cats with CKD were randomly assigned to receive vitamin E (100 IU/cat/day) or placebo (mineral oil) for 24 weeks in addition to standard therapy. Plasma malondialdehyde (MDA) and protein carbonyl (PC) concentrations, DNA damage of peripheral lymphocytes and plasma vitamin E concentrations were measured at baseline and four, eight, 16 and 24 weeks thereafter. Routine laboratory analyses and assessment of clinical signs were performed at each visit.ResultsVitamin E supplementation had no effect on the survival time and did not reduce the severity of clinical signs. Before vitamin E supplementation, no significant differences in vitamin E, MDA and PC concentrations were found between healthy and CKD cats. However, plasma MDA concentration was statistically significantly higher (p = 0.043) in cats with early CKD (IRIS stages 1 and 2) than in cats with advanced CKD (IRIS stages 3 and 4). Additionally, DNA damage was statistically significantly higher in healthy cats (p ≤ 0.001) than in CKD cats. Plasma vitamin E concentrations increased statistically significantly in the vitamin E group compared to the placebo group four (p = 0.013) and eight (p = 0.017) weeks after the start of vitamin E supplementation. During the study and after 24 weeks of vitamin E supplementation, plasma MDA and PC concentrations and DNA damage remained similar to pre-supplementation levels in both the placebo and vitamin E groups.ConclusionsVitamin E supplementation as an addition to standard therapy does not prolong survival in feline CKD.

Development of RP-HPLC Method of Tizanidine HCL with Some Validation Parameter.

This study compiles the information for the development of analytical methods for estimation of the Tizanidine HCl that will be helpful for further research work on this drug and its impurity. The present Literature survey provides information about the Analytical methods like UV,TLC,RP-HPLC,HPTLC,UHPLC and other methods have been reported for Tizanidine HCl drug individually and along with other drugs. The analysis of published data revealed that, there was only UV spectroscopic method (calibration curve metod) is reported for estimation of Tizanidine HCl fixed dose combination. Estimation of Tizanidine HCl by superlative RP-HPLC method i.e. Mobile phase- Acetonitrile: phosphate buffer (pH: 7.5) (50:50%v/v), Column C18 (250mm*4mm*5µm), Flow rate- 1.0 ml/min, Wavelength: 318 nm. Optimized HPLC condition was validated by assessing validation parameters and it meet the acceptance criteria set by ICH. It was showed method was linear and precise. The validated RP-HPLC-PDA method can be used for routine analysis of Tizanidine HCl in tablet.

The detection of ACTH and insulin in equine plasma by solid-phase extraction and micro-flow LC/MSMS.

Previous liquid chromatography/mass spectrometry (LC/MS) methods for the detection of insulin and other similar peptide hormones in equine plasma relied on the use of antibody affinity extraction. As a result, these methods were not suitable for routine high-throughput analysis. A solid-phase extraction (SPE) method incorporating size exclusion as well as reversed-phase interactions allows the selective extraction of peptide hormones such as adrenocorticotropic hormone (ACTH), insulin and their synthetic analogues from equine plasma with approximately 80% extraction efficiencies. This extraction was combined with on-column derivatisation with acetic anhydride, followed by tryptic digestion and analysis by micro-LC/MSMS for high-sensitivity peptide hormone detection. The analysis of tryptic peptides provides greater sensitivity and more robust chromatography compared with the analysis of intact insulin and ACTH. For quantitative analysis, isotopically labelled internal standards of target peptides can be prepared in the laboratory through the use of deuterated acetic anhydride. The utility of the method was assessed for the analysis of ACTH and insulin in samples from horses suffering from pituitary pars intermedia dysfunction (PPID).

High‐Performance Liquid Chromatography–Based Standardization of Stigmasterol in Moringa oleifera: Method Development and Validation Through Design of Experiment Approach

ABSTRACTThe primary objective of this investigation was to develop and validate a robust reversed‐phase high‐performance liquid chromatography (RP‐HPLC) method for quantifying stigmasterol in both Moringa oleifera powder and tablets. The analysis was conducted using a Box–Behnken design. Stigmasterol separation was achieved with a Phenomenex Luna C‐18 column (4.6 × 150 mm2, 5 µm) and a mobile phase consisting of methanol and 0.1% formic acid in an 80:20% v/v ratio. The separation was performed at a flow rate of 1 mL/min, and stigmasterol was detected at a wavelength of 210 nm using a photodiode array detector. Method validation followed the guidelines set forth by the International Council for Harmonisation (ICH) Q2 (R1). This rigorous validation process evaluated critical parameters, including linearity, accuracy, system suitability, precision, and robustness. The results for each parameter were well within the acceptable range, confirming the reliability and efficacy of the established RP‐HPLC method. The findings of this study highlight the potential of the RP‐HPLC method as a dependable tool for the routine analysis of stigmasterol in herbal formulations.

High‐Performance Liquid Chromatography–Based Standardization of Stigmasterol in Moringa oleifera: Method Development and Validation Through Design of Experiment Approach

ABSTRACTThe primary objective of this investigation was to develop and validate a robust reversed‐phase high‐performance liquid chromatography (RP‐HPLC) method for quantifying stigmasterol in both Moringa oleifera powder and tablets. The analysis was conducted using a Box–Behnken design. Stigmasterol separation was achieved with a Phenomenex Luna C‐18 column (4.6 × 150 mm2, 5 µm) and a mobile phase consisting of methanol and 0.1% formic acid in an 80:20% v/v ratio. The separation was performed at a flow rate of 1 mL/min, and stigmasterol was detected at a wavelength of 210 nm using a photodiode array detector. Method validation followed the guidelines set forth by the International Council for Harmonisation (ICH) Q2 (R1). This rigorous validation process evaluated critical parameters, including linearity, accuracy, system suitability, precision, and robustness. The results for each parameter were well within the acceptable range, confirming the reliability and efficacy of the established RP‐HPLC method. The findings of this study highlight the potential of the RP‐HPLC method as a dependable tool for the routine analysis of stigmasterol in herbal formulations.

Assessing the diagnostic value of left ventricular synchrony indices derived from phase analysis by D-SPECT in identifying obstructive coronary artery disease.

This study aimed to assess the diagnostic efficacy of left ventricular synchrony (LVS) for detecting coronary artery disease (CAD). We explored whether the LVS index derived from phase analysis of D-SPECT provides superior diagnostic value compared to conventional perfusion analysis in identifying obstructive CAD. Patients with suspected or confirmed CAD underwent drug-stress/rest gated D-SPECT myocardial perfusion imaging (MPI) and coronary angiography (CAG). A 50% stenosis was set as the threshold for obstructive CAD. 110 participants were enrolled in this analysis. There were significant differences in phase standard deviation (PSD), phase histogram bandwidth (PHB) and entropy among the four groups. Patients without cardiac disease and those with mild-moderate stenosis exhibited no noticeable contraction asynchrony. However, LVS indices demonstrated a gradual increase with the progression of coronary stenosis when compared to NC (P < 0.001). Obstructive CAD was identified in 43 out of 110 participants (39%). Optimal cutoff values for diagnosing obstructive CAD during stress were determined as 7.6° for PSD, 24° for PHB, and 37% for entropy, respectively. Notably, PSD, PHB, and entropy indices exhibited higher sensitivity compared to MPI. The integration of the stress-induced LVS indices into routine MPI analysis resulted in a significantly greater area under the curve (AUC), leading to improved diagnostic performance and enhanced differential capacity. Stress-induced LVS indices increase with the severity of coronary artery stenosis by D-SPECT phase analysis. Further, the indices-derived phase analysis exhibits superior sensitivity and discriminatory ability compared to MPI in detecting obstructive CAD.

Routine oxygen heterocyclic compounds analysis of fragrances using an eco-friendly liquid chromatography coupled to tandem mass spectrometry method

ABSTRACT Coumarin and furocoumarins characterization in cosmetics plays an important role in protecting consumer health. The analytical technique mostly employed for the analysis of these molecules is certainly liquid chromatography coupled to photodiode array or mass spectrometer detectors. The aim of this article was to investigate on the oxygen heterocyclic compounds content in fifty hydro alcoholic fragrances using a fast, sensitive and eco-friendly liquid chromatography coupled to a triple quadrupole mass spectrometer detector analytical method without any sample pre-treatment. To the best of the author’s knowledge, this is the first research article on the quantification of thirty-six oxygen heterocyclic compounds in hydro alcoholic fragrances in less than 4 min and with the use of water/ethanol as mobile phase. Thanks to the good performance of the analytical method used, this can be proposed among the routine methods for the quality control of cosmetics and finished products.

Development of a new magnetic solid-phase extraction method prior to HPLC determination of naproxen in pharmaceutical products and water samples

In this study, a new magnetic solid phase extraction based on magnetic composite modified with biochar obtained from pumpkin peel was developed for the enrichment and extraction of Naproxen in lake water, tablet and urine samples. The effects of main parameters such as pH, extraction time, amount of adsorbent and sample volume, which affect magnetic solid phase extraction, were investigated. Under optimal conditions, intraday and interday precision values for naproxen were below 5.9, with accuracy (relative error) better than 7.0 %. The detection limit and preliminary concentration factor were 12 ng/mL and 10, respectively. The method proposed here can be used for routine analysis of naproxen in lake water, urine and tablets.

Skin Surface Sebum Analysis by ESI-MS

The skin surface is an important sample source that the metabolomics community has only just begun to explore. Alterations in sebum, the lipid-rich mixture coating the skin surface, correlate with age, sex, ethnicity, diet, exercise, and disease state, making the skin surface an ideal sample source for future noninvasive biomarker exploration, disease diagnosis, and forensic investigation. The potential of sebum sampling has been realized primarily via electrospray ionization mass spectrometry (ESI-MS), an ideal approach to assess the skin surface lipidome. However, a better understanding of sebum collection and subsequent ESI-MS analysis is required before skin surface sampling can be implemented in routine analyses. Challenges include ambiguity in definitive lipid identification, inherent biological variability in sebum production, and methodological, technical variability in analyses. To overcome these obstacles, avoid common pitfalls, and achieve reproducible, robust outcomes, every portion of the workflow—from sample collection to data analysis—should be carefully considered with the specific application in mind. This review details current practices in sebum sampling, sample preparation, ESI-MS data acquisition, and data analysis, and it provides important considerations in acquiring meaningful lipidomic datasets from the skin surface. Forensic researchers investigating sebum as a means for suspect elimination in lieu of adequate fingerprint ridge detail or database matches, as well as clinical researchers interested in noninvasive biomarker exploration, disease diagnosis, and treatment monitoring, can use this review as a guide for developing methods of best-practice.