Unlocking hot trub's potential: a simple method for extracting bitter acids and xanthohumol.

BACKGROUND: Hot trub is a macronutrient- and micronutrient-rich by-product generated in the brewing industry, which is still underrated as a raw material for reprocessing purposes. In this context, this study aimed to investigate the extraction of bitter acids' and xanthohumol from hot trub as well as identify the significance of parameters for the process. The research assessed various extraction parameters, such as pH, ethanol concentration, temperature, and solid-to-liquid ratio, using a Plackett-Burman design. RESULTS: Ethanol concentration and pH were the most significant parameters affecting extraction yield. ß-acids were found to be the principal components of the bitter acids, with a maximum concentration near 16 mg g-1, followed by iso-α-acids and α-acids achieving 6 and 3.6 mg g-1, respectively. The highest yields of bitter acids were observed in the highest ethanol concentration, while pH was relevant to extraction process in treatments with low ethanol ratios. Concerning the xanthohumol extraction, the approach achieved maximum concentration (239 µg g-1) in treatments with ethanol concentration above 30%. Despite their variances, the phytochemicals exhibited comparable extraction patterns, indicating similar interactions with macromolecules. Moreover, the characterization of the solid residues demonstrated that the extraction process did not bring about any alterations to the chemical and total protein profiles. CONCLUSION: Ethanol concentration was found to have the most significant impact on the extraction of bitter acids and xanthohumol, while temperature had no significant effect. The solid remains resulting from the extraction showed potential for use as a protein source. © 2024 Society of Chemical Industry.

Fatal 4-MEC Intoxication: Case Report and Review of Literature.

ABSTRACT: Synthetic cathinones are one of the major pharmacological families of new psychoactive substances and 4-methylethcathinone (4-MEC) has emerged in recent years as a recreational psychostimulant. We report a case of a 35-year-old man found dead and naked at home by his friend. Although no anatomic cause of death was observed at autopsy, toxicological analysis identified 4-MEC and hydroxyzine at therapeutic level (160 ng/mL). 4-Methylethcathinone was quantified in autopsy samples by a validated method consisting in liquid-liquid extraction and gas chromatography coupled to tandem mass spectrometry: peripheral blood, 14.6 µg/mL; cardiac blood, 43.4 µg/mL; urine, 619 µg/mL; vitreous humor, right 2.9 µg/mL and left 4.4 µg/mL; bile, 43.5 µg/mL; and gastric content, 28.2 µg/mL. The cause of death was 4-MEC intoxication and the manner of death could be either accidental or suicidal. The literature concerning 4-MEC was reviewed, focusing on distribution in classical postmortem matrices and 4-MEC metabolism and postmortem redistribution and stability.

Failure Mode Critical Effect Analysis and Design of Experiment-Based Robust Chromatographic Method for Simultaneous Estimation Lornoxicam and Eperisone Hydrochloride.

Failure mode critical effect analysis and design of experiment-based high performance thin layer chromatography (HPTLC) method has been developed for simultaneous estimation of lornoxicam (LOC) and eperisone hydrochloride (EPR). Failure modes were identified on the basis of prior knowledge and experimental data with the help of Ishikawa diagram for the development of method. The criticality of failure mode was assessed by giving risk priority number and criticality rank on the basis of preliminary experimental trials. The identified critical failure modes were analyzed for their effect by design of experiment (DoE)-based Plackett-Burman screening design. From 11 critical factors, the volume of methanol and modifier in mobile phase composition were found as critical failure modes. Critical failure mode was further analyzed by DoE based on central composite design for study of their relationship with resolution of both drugs. Quadratic model suggested by design was further used for failure mode risk control and navigation of design space for a resolution of both drugs more than 1.5. Failure mode risk control strategy was set for robust HPTLC method for simultaneous estimation of both drugs in laboratory mixture. Developed and validated HPTLC method was applied for assay of LOC and EPR in their laboratory mixture and assay values were found in good agreement with a spiked amount of drugs.

The complexities associated with new psychoactive substances in influent wastewater: The case of 4-ethylmethcathinone.

Consumption of new psychoactive substances (NPS) is an international problem for health, policing, forensic, and analytical laboratories. The transience of these substances in the community, combined with continual slight structural changes to evade legislation makes the elucidation of NPS an analytical challenge. This is amplified in a matrix as complex as wastewater. For that reason, suspect and non-target methodologies, employing high resolution mass spectrometry are the most appropriate current tool to facilitate the identification of new and existing compounds. In the current work, a qualitative screening method of influent wastewater using liquid chromatography-high resolution mass spectrometry showed a strong signal at m/z 192.1382 - identical to that of two NPS standards that were in our method (pentedrone and 4-methylethcathinone), and with identical fragment ions, but the retention times did not match. This work shows the methodology followed to identify this compound, highlighting the challenges of the identifying "new" compounds in influent wastewater.

The Stability of 4-Chloromethcathinone in Blood and Vitreous Humor.

We present results of our study on the stability of 4-chloromethcathinone (4-CMC) in authentic postmortem peripheral blood and vitreous humor samples. The stability of 4-CMC was determined in postmortem blood samples (for a period of 90 days) and vitreous humor (30 days) at three different temperatures: -15°C, +4°C, and + 23°C. The analyses were carried out using ultra-high-performance liquid chromatography coupled with triple-quadrupole tandem mass spectrometry (UHPLC-QqQ-MS/MS). In both materials, the lowest 4-CMC stability was demonstrated at room temperature. The blood samples stored in a freezer (-15°C) showed stability for the entire study period (90 days), while in the case of the vitreous humor sample stored at the same temperature the concentration of the substance decreased by 53% after 30 days. The study carried out in authentic postmortem blood and vitreous humor samples confirms the previous reports of 4-CMC instability in biological material. Authors suggest that the biological material should be stored frozen until analyses are carried out as soon as possible after collection of the material.

Changes in chemical profile of Cascade hop cones according to the growing area.

BACKGROUND: The growing area has a substantial effect on plants, affecting secondary metabolism. For hops, different authors have studied the effect of growing area on the chemical composition of cones with the aim of verifying and understanding the changes in hop characters. Despite the scant literature the subject receives increasing attention by brewers and hop growers. The present study aimed to characterize, using gas chromatography-mass spectrometry (GC-MS), and high-performance liquid chromatography with ultraviolet detection (HPLC-UV), cones of hop (Humulus lupulus L.) cultivar Cascade. Plant material was obtained from nine different areas of Italy and compared with Cascade samples grown in the United States, Germany and Slovenia. RESULTS: Differences in bitter acids and xanthohumol content were observed. Nevertheless, no correlation between bitter acids and xanthohumol production, on the one hand, and rainfall, temperatures and latitude, on the other hand, were observed in our samples. The Slovenia samples were richer in molecules that confer hoppy, woody and flower notes; USA2 samples were more characterized by woody, earthy, grassy and floral aroma, quite different characters if compared to USA1, which had the lowest presence of grassy aromatic compounds. In the Italian samples, TRENTINO was the genotype most characterized by limonene presence. CONCLUSION: The results of this study are indicative of the importance for hop users to know and characterize hops coming from different growing regions. The study pays special attention to the characterization of the differences in chemical characters of Cascade hop in Italy, where hop cultivation has developed only recently, but is in continuous expansion. © 2019 Society of Chemical Industry.

Univariate and multivariate spectrophotometric methods for simultaneous determination of avobenzone and octinoxate in pure form and in cosmetic formulations: A comparative study.

Simple, economic and precise spectrophotometric and chemometric techniques were used to determine UV filters namely; avobenzone (AV) and octinoxate (OCT) simultaneously in pure form and in cosmetic formulations in concentration range (2-10 µg·mL-1) for both drugs. The spectrophotometric technique includes five different methods; Method (A) is first derivative (D1) spectrophotometry at 380.6 nm for AV and 276.2 nm for OCT, Method (B) is first derivative of ratio spectra (DR1) at 352.8 nm for AV and 312.2 nm for OCT, Method (C) is ratio difference spectrophotometry (RD) at 356 nm and nm 347.2 nm for AV and at 311.6 nm and 281 nm for OCT, Method (D) is mean centering spectrophotometry (MCR) at 356 nm for AV and 301.8 nm for OCT and method (E) is modified Vierordt's method which involves absorbance measurement at 358 nm for AV and 309.2 nm for OCT and determination of the concentration of x and y from the two simultaneous equations. The chemometric technique includes multivariate calibration methods; partial least squares (PLS) and principle component regression (PCR) using the absorption spectra. The proposed methods were applied for determination of (AV) and (OCT) simultaneously in pure form and in cosmetic formulations. These methods were validated according to ICH guidelines.

Simultaneous enantioseparation of methcathinone and two isomeric methylmethcathinones using capillary electrophoresis assisted by 2-hydroxyethyl-ß-cyclodextrin.

Methcathinone (ephedrone), 4-methylmethcathinone (mephedrone), and 3-methylmethcathinone (metaphedrone) are toxicologically-important cathinone derivatives used commonly as designer drugs. In this work we show the first method allowing to separate simultaneously all these molecules in a chiral medium, ensuring good resolution between all enantiomers. Eight cyclodextrins have been tested as potential chiral selectors, the best results were obtained with 2-hydroxyethyl-ß-cyclodextrin, unreported so far for efficient separation of cathinones. After optimization, the method was calibrated and validated with and without the use of internal standard. The addition of standard improved an overall repeatability and precision, the use of electrophoretic mobility ratio was especially favorable (RSD < 1%). It was demonstrated that the method may be easily extended by introducing the additional cathinone-related drugs to the sample, maintaining satisfactory separation efficiency.

Reliable and simple spectrophotometric determination of sun protection factor: A case study using organic UV filter-based sunscreen products.

BACKGROUND: Current in vitro SPF screening method for plant oil body (oleosome)-based SPF products possesses significant inconsistency and low reliability in the SPF rating. OBJECTIVES: The primary objective of this study was to evaluate the reliability and reproducibility of spectrophotometrically determined sun protection factor (SPF) from oleosome-based SPF products. The secondary objective was the data comparison of the spectrophotometric measurements against in vivo SPF testing to establish a reliable in vitro test method as a screening assay. METHODS: Octyl methoxycinnamate (UVB filter) and avobenzone (UVA filter) were loaded into safflower oil bodies and formulated into oil-in-water emulsion-based finished products. To evaluate the reliability between in vivo and spectrophotometric test methods, samples were dispatched to a clinical laboratory, and the reported SPF values were compared with spectrophotometric test results. RESULTS: The observed SPF from the in vivo and spectrophotometric test results demonstrated a high correlation for SPF 30 products. Proportional correlation between the two evaluation methods was observed for SPF 15 and 50 products with slightly lesser accuracy with a smaller number of population tested in the clinical studies. CONCLUSIONS: A reliable spectrophotometric screening method for oil body-based SPF formulas has been developed using two broadly used organic UV sunscreen actives as a case study. The results demonstrated a high level of reproducibility and reliability compared to the US FDA-guided in vivo SPF testing method.

Research Status of New Designer Drug Methcathinone in Forensic Toxicology.

Methcathinone, a new cathinone designer drug, which is structurally similar to amphetamine analogs, is a central nervous stimulant. Recently, there has been a worldwide rise in its popularity and abuse, and a growing number of cases with disability or even death is reported in several countries, resulting in public concern. The typical symptoms include accelerated heartbeat, high temperature, anxiety, depression, etc. Forensic studies on its toxicity mechanism are rare. This article reviews its toxicological effects, poisoning symptoms, poisoning and addiction mechanisms, and detection methods, to provide theoretical reference for future studies and guidance for related forensic identification.

Patterns of use and toxicity of new para-halogenated substituted cathinones: 4-CMC (clephedrone), 4-CEC (4-chloroethcatinone) and 4-BMC (brephedrone).

OBJECTIVE: This paper aims to present results of the analysis of clephedrone (4-CMC), 4-chloroethcathinone (4-CEC), and brephedrone (4-BMC) on recreational drug markets and a systematic review of all the available information concerning these substances. MATERIAL AND METHODS: Samples collected by the drug checking service of the Spanish harm reduction NGO-Energy Control were analyzed and systematic research was conducted. Between June 2014 and October 2016, 1,471 samples with at least one NPS were analyzed, 397 of which contained cathinones. RESULTS: Clephedrone was found in 29 samples, brephedrone in 8, and both were present in 2 samples. 4-Chloroethcathinone was detected in 5 samples. Eleven out of the 47 purchased samples (23.4%) were tested to contain the substance the user expected. Samples received were mainly sold as 3-MMC, MDMA, ketamine, and other cathinones. No literature on the effects or toxicity of these substances was found; the only information available was on internet fora. On many posts, users exhibit concerns about potential toxicity and side effects of using these substances. CONCLUSION: Since the emergence of these substances could prove to be the next step to the cat-and-mouse game existing between drug producers and legislation, further clinical and epidemiological research should be carried out in order to build evidence to support policy for public health issues.

Separation of ortho, meta and para isomers of methylmethcathinone (MMC) and methylethcathinone (MEC) using LC-ESI-MS/MS: Application to forensic serum samples.

Separation and identification of positional isomers is an important issue in forensic toxicology, particularly in the context of new psychoactive substances (NPS). Despite the structural similarity, positional isomers often show different pharmacological properties and thus can exhibit dramatic differences with respect to their toxicity. Additionally, besides these pharmacological and toxicological effects, the legal status is also of great importance. We present a sensitive and selective LC-MS/MS method to separate the ortho, meta and para isomers of methylmethcathinone (MMC) and methylethcathinone (MEC) using a core-shell biphenyl analytical column. Reliability of the method was confirmed under consideration of the validation parameters selectivity, linearity, accuracy and precision, analytical limits, processed sample stability, matrix effects and recovery. Linearity was demonstrated over the entire calibration range from 5 to 250ng/ml with the use of a 1/x2 weighting. Appropriate quantification and detection limits (LLOQ=5ng/ml, LOD<2ng/ml) could be achieved. Application of the method to real serum samples collected between June 2014 and August 2016 revealed the proof of a recent MMC or MEC consumption, respectively, in eight cases. Isomers of MMC could be detected in three of these eight cases, of which two were positive for 3-MMC and one was positive for 2-MMC. The other samples were tested positively for 3-MEC. In none of the samples 4-MMC, 2-MEC or 4-MEC could be detected. Only substances that were not governmentally controlled at that time could be detected, reflecting the rapid response of the recreational drug market to newly enacting drug laws.

Identification of five pyrrolidinyl substituted cathinones and the collision-induced dissociation of electrospray-generated pyrrolidinyl substituted cathinones.

This article reports on the analytical properties of five pyrrolidinyl substituted cathinones: α-pyrrolidinononaphenone (α-PNP, 1), 4-chloro-α-pyrrolidinopropiophenone (4-Cl-α-PPP, 2), 4-chloro-α-pyrrolidinovalerophenone (4-Cl-α-PVP, 3), 5-dihydrobenzofuranpyrovalerone (5-DBFPV, 4), and 2-(pyrrolidin-1-yl)-1-(5,6,7,8-tetrahydronaphthalen-2-yl)hexan-1-one (ß-THNPH, 5). These identifications were based on liquid chromatography-quadrupole time-of-flight-mass spectrometry (LC-QTOF-MS), gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance spectroscopy (NMR). To our knowledge, no analytical data about α-PNP, 4-Cl-α-PPP, 4-Cl-α-PVP, and ß-THNPH have appeared until now, making this the first report on these compounds. Moreover, in order to study the collision-induced dissociation (CID) characteristic fragmentation routes of pyrrolidinyl substituted cathinones, a total number of 13 pyrrolidinyl substituted cathinones were selected and discussed. The major fragmentation pathways under CID mode are produced, leading to the formation of characteristic ions. Product ions of [M-C4 H9 N]+ and Cn H2n N+ indicate the presence of pyrrolidinyl substitution. Characteristic fragments are also produced via the cleavages of the CH-N(CH2 )4 bond and the CO-CHN bond. Copyright © 2016 John Wiley & Sons, Ltd.

Identification and quantification of 4-methylethcathinone (4-MEC) and 3,4-methylenedioxypyrovalerone (MDPV) in hair by LC-MS/MS after chronic administration.

4-Methylethcathinone (4-MEC) and 3,4-methylenedioxypyrovalerone (MDPV) are synthetic cathinones. The objective of this study was to develop a method in order to measure these compounds in hair of a patient. After decontamination, 20mg of hair were grinded and incubated in phosphate buffer pH 5.0 in presence of 100ng of MDMA-d5 used as internal standard. Double basic liquid-liquid extraction was performed. Samples were separated on a 1.9µm Hypersil GOLD PFP column (100×2.1mm) using gradient elution. Compounds were detected by a LCQ TSQ Vantage XP triple-quadrupole mass spectrometer. SRM transitions m/z 192.1→146.1 and 174.2, m/z 276.1→175.0 and 205.1 and m/z 199.1→165.1 were used for 4-MEC, MDPV and IS, respectively. The assay was accurate and precise over the range 0.001 (lower limit of quantification) to 1ng/mg in hair. No matrix effect was observed. The method has been applied to a 30-year-old man who usually consumed cathinones for 6 months administered intravenously and was admitted to a general hospital for delirious and tachycardia after absorption of 10g of a powder sold as 4-MEC and 5g of MDPV. Both 4-MEC (30ng/mg) and MDPV (1ng/mg) were identified in the hair at high concentrations showing a regular consumption of these drugs. Many others compounds were also identified (mephedrone, MDMA, MDA, cocaine and metabolites, tramadol, hydroxyzine, aripiprazole, haloperidol). Few data are available on concentration of these new designer drugs in hair however important in order to determine the acute or chronic consumption of these drugs.

In vitro assays in natural products research - a matter of concentration and relevance to in vivo administration using resveratrol, α-mangostin/γ-mangostin and xanthohumol as examples.

Herbal or botanical dietary supplements are an ever increasingly popular category of products in the United States and around the world. In vitro data can provide meaningful insight into the potential target and mechanism of action for a proposed active compound but may also be misused to promote a supplement to consumers with unverified health claims. In vitro data need to be considered alongside pharmacokinetic and pharmacodynamic data in preclinical animal and clinical human trials. While considerable activity of compounds and extracts in vitro may lead to further testing in vivo, in many instances, concentrations tested in cell lines or isolated targets are not achievable at the target site in vivo. Thus, whether the in vitro data are relevant to humans after oral administration is questionable. This review will discuss this discrepancy using in vitro and in vivo data of resveratrol, xanthones (α-mangostin and γ-mangostin) and xanthohumol.

Fast Sampling, Analyses and Chemometrics for Plant Breeding: Bitter Acids, Xanthohumol and Terpenes in Lupulin Glands of Hops (Humulus lupulus).

INTRODUCTION: The valuable secondary metabolites in hops (bitter acids, xanthohumol, volatile monoterpenes and sesquiterpenes) are sequestered in lupulin glands (extracellular trichomes) which can be collected and analysed with little or no sample preparation. OBJECTIVES: To determine whether high throughput screening of lupulin glands composition, by fast analyses and chemometrics, could be used for breeder selection of hops with key flavour attributes. METHODS: Lupulin glands from 139 plants (39 cultivars/advanced selections) were analysed by Raman and 1 H NMR spectroscopy, and head-space solid-phase microextraction (HS-SPME) GC-FID. The digital X,Y-data were subjected to principal component analysis (PCA) and the results compared with conventional analyses of extracts of whole hops from the same plants. Quantitative 1 H NMR analyses were also done for the bitter acids. RESULTS: Raman spectroscopy rapidly identified hops cultivars with high xanthohumol concentrations and high α:ß bitter acid ratios. 1 H NMR spectroscopy was slower, requiring a solvent extraction, but distinguished cultivars by cohumulone content as well as α:ß acid ratios. HS-SPME-GC rapidly distinguished aroma hops with high myrcene and farnesene contents, and pinpointed a novel selection with unusual sesquiterpenes. The quantitative NMR analyses showed correlations between bitter acid concentrations related to biosynthetic pathways. CONCLUSIONS: Analysis of lupulin glands gave reliable results for the main quality indicators used by hops breeders, potentially avoiding harvesting, drying and solvent extracting whole hops. PCA of digital X,Y-data rapidly discriminated different hops chemotypes, and highlighted plants with potential for new flavourcultivars. Copyright © 2016 John Wiley & Sons, Ltd.

Optimization and Validation of a Fast UPLC Method for Simultaneous Determination of Hydroquinone, Kojic Acid, Octinoxate, Avobenzone, BHA, and BHT.

A previously published HPLC method for the simultaneous determination of six major components (hydroquinone, kojic acid, octinoxate, avobenzone, butylated hydroxyanisole, and butylated hydroxytoluene) in a skin-whitening cream was transferred and optimized to an ultra-performance LC system. Separation was achieved in a ZORBAX SB-Phenyl Rapid-Resolution High Throughput column (2.1 × 100 mm, 1.8 µm), using a mobile phase consisting of water with 0.1% acetic acid and acetonitrile at a flow rate of 0.7 mL/min. The column was maintained at 40°C, and detection was carried out at 230 nm using a diode-array detector. These chromatographic conditions allow the separation of the six compounds in 3 min instead of 14 min. The extraction procedure was optimized, reducing the time and demonstrating its suitability. The method was validated according to International Conference on Harmonization guidelines, with respect to specificity, precision, accuracy, and linearity. Selectivity was found to be satisfactory. Linear regression analysis data for all compounds showed a good linear relationship, with r2 > 0.999 in the concentration range of 50-120% of the label claim for each compound. The RSD for precision and accuracy of the method was found to be less than 2% for all compounds. Comparison of system performance with the previously published HPLC method was made with respect to analysis time, efficacy, and resolution. The proposed method is faster and consumes less solvent and was applied in the determination of six major compounds in batches of skin-whitening cream manufactured during the validation process.

A GC-MS Method for Detection and Quantification of Cathine, Cathinone, Methcathinone and Ephedrine in Oral Fluid.

The stimulating herbal drug khat (cathine, cathinone) and its analog methcathinone are common substances of abuse in most countries. A GC-MS method was developed and validated for the detection and quantification of cathine, cathinone, methcathinone and ephedrine in oral fluid specimens. The analytes and internal standard (amphetamine-d5) were extracted from 0.5 mL oral fluids by ethyl acetate, and then the dried extracts were derivatized with heptafluorobutyric anhydride at 70°C for 30 min. The MS was used in selected ion monitoring mode. Ions monitored were m/z 117, 240 and 330 for cathine, m/z 77, 105 and 240 for cathinone, m/z 105, 210 and 254 for methcathinone, m/z 210, 254 and 344 for ephedrine and m/z 244 and 336 for amphetamine-d5 The calibration curves were linear (r(2)> 0.98) in the concentration range 20-2,000 ng/mL for all analytes. The intra- and inter-assay imprecisions were within (1.6-12.5%) and (1.5-9.5%), respectively, for all analytes. Intra-assay accuracies were between -5.9 and 6.7% for all analytes. The method was successfully applied to detect and quantify the target analytes from oral fluid specimens collected from Khat and methcathinone users.

Sorption and degradation of selected organic UV filters (BM-DBM, 4-MBC, and OD-PABA) in laboratory water-sediment systems.

Organic UV filters that have been widely used in sunscreens and other personal care products have drawn much public concern because of their widespread contamination in the environment and their potential ecological risks to ecosystems. We selected three UV filters with high frequency of detection in the environment, namely butyl methoxy dibenzoylmethane (BM-DBM), ethylhexyl dimethyl p-aminobenzoate (OD-PABA), and 4-methylbenzylidene camphor (4-MBC), to investigate the sorption and degradation behaviors of these compounds in lab-scale water-sediment systems set up with natural water and sediment samples collected from different rivers and lakes (i.e., Yangtze River, Qinhuai River, Xuanwu Lake, and Mochou Lake) in Nanjing, East China. The sorption isotherms of these UV filters were well described by the Freundlich equation (C s = K f × C w (n) ). The sorption of three UV filters in four sediments was all linear or close to it, with n values between 0.92 and 1.13. A moderate to strong sorption affinity was observed for these compounds, and the sorption appears to be irreversible. For the combined sorption and degradation studies, sorption was found to be a primary mechanism for the disappearance of these UV filters from the water phase, and biotransformation appears to be the predominant factor for the degradation of the target compounds in the water-sediment systems. All three UV filters were found to be slightly resistant to the microbes in these systems, with DT50total and DT90total values-the disappearance time (DT) describes the time in which the initial total mass of the UV filters in the whole system is reduced by 50 and 90 %-ranging between 18 and 31 days and 68 and 101 days, respectively.

A sensitive LC-ESI-MS/MS method for the quantification of avobenzone in rat plasma and skin layers: Application to a topical administration study.

This study describes the development of a sensitive high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) method for the quantification of avobenzone in rat plasma and skin layers. Separations were performed on a Zorbax SB C8 column using a binary gradient mobile phase composed of acetonitrile and 0.1% formic acid in water. The assay achieved LLOQ of 0.5ng/ml for plasma, 5ng/ml for stratum corneum, and 10ng/ml for epidermis and dermis. This method was applied to a percutaneous absorption study of avobenzone in rats. At 12h following topical application of emulsion and lotion (applied amount of avobenzone 11.7mg/kg), avobenzone was found primarily in the stratum corneum (16.3-17.8%) followed by epidermis (2.0-3.4%) and dermis (0.11-0.15%). Avobenzone was not quantifiable in the plasma samples collected over a 12h sampling period. Given the excellent plasma assay sensitivity, this study provides evidence that the systemic absorption of avobenzone is insignificant, if any, after topical application.