Instrumental Limits Of Quantification Research Articles

Ultrasound-Assisted Extraction, Followed by Gas Chromatography-Mass Spectrometry for the Simultaneous Quantification of Ethinyl Estradiol and Drospirenone in Contraceptive Formulations.

Contraceptive tablets typically contain a combination of two synthetic versions of an estrogen and a progestogen, which work together to inhibit the ovulation process. An accurate and precise quantification of these components is essential for contraceptive producers. In this study, we have developed the first gas chromatography-mass spectrometry (GC-MS) method for the simultaneous quantification of 17α-ethinyl estradiol (EE) and drospirenone (DP) in contraceptive formulations. Under the final working conditions, analytes were extracted from the solid by ultrasound-assisted extraction (15 min) in methanol. The resulting suspension was diluted in ethyl acetate, subjected to centrifugation and, finally, the supernatant was directly injected into the GC-MS system. No derivatization reagents were utilized. To correct for instrumental variations, calibration was performed using the internal standard method, with cholesterol as the internal standard. A good linearity was achieved throughout the calibration range for both EE (3-12 µg mL-1) and DP (300-1200 µg mL-1), with R2 values exceeding 0.99. Trueness, assessed in terms of percentages of recovery, was also found to be satisfactory for both analytes, with recovery rates of 106 ± 8% for EE and 93 ± 9% for DP. Furthermore, intra-day and inter-day precision studies yielded relative standard deviation values below 6% for both analytes. In terms of sensitivity, the instrumental limits of detection were 0.25 µg mL-1 for EE and 6.6 µg mL-1 for DP, and the instrumental limits of quantification 0.82 µg mL-1 for EE and 22 µg mL-1 for DP. The method was successfully applied to the analysis of contraceptive tablets from three different pharmaceutical companies. No differences were observed between the measured and the declared amount of active principle per tablet, demonstrating the applicability of the procedure. In addition, a stability study conducted on both the standards and sample extracts demonstrated that they can be stored at room temperature for a minimum period of seven days.

Atrazine and its degradation products in drinking water source and supply: Risk assessment for environmental and human health in Campinas, Brazil

Atrazine is a broad-spectrum herbicide widely used worldwide to control grassy and broadleaf weeds. Atrazine's popularity is attributable to its cost-effectiveness and reliable performance. Relatedly, it is also an important micropollutant with a potential negative impact on biodiversity and human health. Atrazine has long been regularly detected in several environmental compartments, and its widespread use has resulted in ubiquitous and unpreventable contamination. Among pesticides sold in Brazil, atrazine has remained among the top-ranked active ingredients for the last several years. Thus, this study aimed to evaluate the occurrence of atrazine and three degradation products (hydroxyatrazine, desisopropylatrazine, and desethylatrazine) in surface water (Capivari and Atibaia rivers) and treated water, monthly sampling from two drinking water treatment plants in Campinas (São Paulo, Brazil). An analytical method using solid-phase extraction (SPE) and liquid chromatography tandem mass spectrometry (LC-MS/MS) was developed to determine target compounds simultaneously. The method presented instrument quantification limits from 0.5 to 4.0 ng mL−1 and recovery values from 80 to 112%, with a maximum relative standard deviation of 6%. All analytes had a detection frequency of 100% from 2 to 2744 ng L−1. Statistical analysis showed no analyte removal after conventional water treatment. Also, the Capivari River showed greater analyte concentration than the Atibaia River. Performed risk assessments according to current Brazilian standards showed no human and environmental health risks. However, other risk assessment approaches may indicate potential risks, advocating for further research and ongoing surveillance.

Dilute-and-shoot coupled to mixed mode liquid chromatography-tandem mass spectrometry for the analysis of persistent and mobile organic compounds in human urine

In this work, a comprehensive method for the simultaneous determination of 33 diverse persistent and mobile organic compounds (PMOCs) in human urine was developed by dilute-and-shoot (DS) followed by mixed-mode liquid chromatography coupled with tandem mass spectrometry (MMLC-MS/MS). In the sample preparation step, DS was chosen since it allowed the quantification of all targets in comparison to lyophilization. For the chromatographic separation, Acclaim Trinity P1 and P2 trimodal columns provided greater capacity for retaining PMOCs than reverse phase and hydrophilic interaction liquid chromatography. Therefore, DS was validated at 5 and 50 ng/mL in urine with both mixed mode columns at pH = 3 and 7. Regarding figures of merit, linear calibration curves (r2 > 0.999) built between instrumental quantification limits (mostly below 5 ng/mL) and 500 ng/mL were achieved. Despite only 60% of the targets were recovered at 5 ng/mL because of the dilution, all PMOCs were quantified at 50 ng/mL. Using surrogate correction, apparent recoveries in the 70–130% range were obtained for 91% of the targets. To analyse human urine samples, the Acclaim Trinity P1 column at pH = 3 and 7 was selected as a consensus between analytical coverage (i.e. 94% of the targets) and chromatographic runs. In a pooled urine sample, industrial chemicals (acrylamide and bisphenol S), biocides and their metabolites (2-methyl-4-isothiazolin-3-one, dimethyl phosphate, 6-chloropyridine-3-carboxylic acid, and ammonium glufosinate) and an artificial sweetener (aspartame) were determined at ng/mL levels. The outcomes of this work showed that humans are also exposed to PMOCs due to their persistence and mobility, and therefore, further human risk assessment is needed.

Method development for the LC-MS/MS determination of C60 and C70 fullerenes and their functionalized derivatives in airborne particulate matter, settled dust and soot

Fullerenes are organic contaminants of growing concern due to their increasing use for industrial purposes, in addition to their emission by natural and anthropogenic combustion sources.Their analysis is made tricky by their unique chemical structure and their acute hydrophobicity. Thus, analytical developments are required for further environmental evaluation of their occurrence. This article presents such a development for the analysis of C60 and C70 fullerenes together with three of their functionalized derivatives in airborne particulate matter, settled dust and soot from diesel exhaust.Pressurized Liquid Extraction was performed with toluene and acetonitrile as extraction solvents, and gave mean extraction recoveries from 75% to 95% for the five fullerenes investigated.Liquid Chromatography was optimized in terms of stationary phase and mobile phase to obtain a good separation of the compounds. Optimal separation of the compounds by liquid chromatography were obtained using a C18 stationary phase and a mixture of toluene - acetonitrile as mobile phase in gradient mode.The mass spectrometry detection method was also optimized with a comparison of three ionization sources: Electrospray ionization (ESI), Atmospheric Pressure Chemical Ionization (APCI) and Atmospheric Pressure PhotoIonization (APPI). APPI gave the most sensitive and repeatable detection with instrumental limits of quantification (LOQ) down to 10 pg injected. MS/MS was used in pseudo-MRM mode to enhance signal intensity.The optimized LC-APPI-MS/MS method was then validated and applied to indoor PM10 and household dust samples, and to a Diesel Particulate Matter Reference Material. None of these samples showed concentrations of fullerenes above the method quantification limits.

OCORRÊNCIA DE AGROTÓXICOS EM SOLOS ARGILOSOS E ARENOSOS APÓS APLICAÇÃO EM PASTAGENS E CANA-DE-AÇÚCAR

OCCURRENCE OF PESTICIDES IN CLAY AND SANDY SOILS AFTER APPLICATION IN PASTURE AND SUGARCANE CROPS. Sugarcane is considered one of the greatest alternatives for the biofuels sector due to the high potential in the production of ethanol and its respective by-products. Processes of converting degraded pastures into sugarcane crops have been increasingly common in Brazil, as well as the use of pesticides to control plant diseases and pests in several crops. The objective of this work was to evaluate the occurrence of 2,4-D, ametryn, tebuthiuron, fipronil and its degradation products (fipronil sulfide and fipronil sulfone) in clay and sandy soils when applied to pasture and sugarcane management. Solid-liquid extraction and liquid chromatography coupled to mass spectrometry were used to quantify the compounds. The optimized method was validated with the following parameters: linear range from 0.5 to 300 μg L-1; linearity (r) > 0.99; precision with CV from 1.0 to 15.0%; accuracy of 60 to 117%, instrumental limit of detection (LOD) from 0.1 to 1.0 μg L-1 and instrumental limit of quantification (LOQ) of 0.5 μg L-1 for all pesticides, except 2,4-D (5.0 μg L-1). Pesticides concentrations of the experimental farms ranged from 0.1 to 266 μg kg-1, with the highest concentrations found in the months of pesticide’s application. The results showed the persistence of some pesticides in the soils even after months of use.

Development and validation of the method for determination of amitraz in honey using high-performance liquid chromatography with mass spectrometric detection

Method for determination of the insecticide amitraz residual content in honey has been developed and validated. The method is selective, express and easy-to-perform. The technique is based on the extraction of amitraz from alkalized aqueous solutions of honey with n-hexane and quantitative determination by high-performance liquid chromatography with mass spectrometric detection. Validation was performed using three types of honey at three levels of amitraz application 6, 120 and 220 µg/kg. The limit of quantification was 0.9 µg/kg, the calibration curves were linear in the concentration range from 2.5 to 125.0 ng/mL (the corresponding analyte content in honey is from 5.0 to 250.0 µg/kg), relative values of the standard deviations of repeatability and within-laboratory reproducibility did not exceed 3.4 and 5.9 %, respectively, the bias values varied from –8.2 to 5.6 %, the expanded uncertainty estimates of the results ranged from 12 to 16 % (P = 0.95). Instrumental limit of quantification, overall efficiency of the process and robustness were also evaluated during the validation process.

Determination of free amino acids in Eriocheir sinensis by ultra-high performance liquid chromatography-high resolution mass spectrometry

游离氨基酸不仅是一类重要的营养物质,更与中华绒螯蟹独特的滋味和香味密切相关。对游离氨基酸含量进行测定,能为中华绒螯蟹产品的品质评价和风味研究提供有价值的信息。该工作通过优选提取溶剂、优化仪器测定参数,最终使用5%(v/v)高氯酸水溶液提取目标物,采用XDB-C18色谱柱(100 mm×4.6 mm, 1.7 μm),以0.1%(v/v)甲酸水溶液-乙腈为流动相进行梯度洗脱,在电喷雾正离子电离、选择离子扫描模式下进行检测,外标法定量,建立了超高效液相色谱-高分辨质谱(UHPLC-HRMS)测定中华绒螯蟹中17种游离氨基酸含量的方法。结果表明,17种氨基酸在10.0~200.0 mg/L范围内线性关系良好,相关系数(R2)≥0.9990,仪器检出限为0.3 mg/L,仪器定量限为1.0 mg/L。在中华绒螯蟹可食部分中按三水平进行加标回收试验,各目标物的回收率在78.4%~105.3%之间。通过对仪器和方法精密度进行评估,发现17种氨基酸测定仪器重复性的RSD≤4.2%,方法重复性试验的RSD≤5.2%,再现性试验的RSD≤11.4%,精密度数据均在合理范围内。利用该研究建立的检测方法对20个中华绒螯蟹样本进行了实际样品检测,总结了17种游离氨基酸在蟹肉、蟹膏、蟹黄中的分布特点,验证了该方法是一种前处理简便、选择性好、准确度高的检测技术。

Method Validation and Uncertainty Estimation for Total Phosphorus Determination in Animal Feed Using UV-Vis Spectrophotometer

Objective: The study presents the validation protocol for the determination of total phosphorus content at parts per million (ppm) (μg/L) levels in animal feed by a UV-Vis spectrophotometer. Methods: The measured absorbance of solutions against the blank solution was at 400 nm with the spectrophotometer. A combined ammonium heptamolybdate tetrahydrate and ammonium monovanadate blue solution was used as a coloring reagent for detection. This method was validated by evaluation of statistical parameters such as linearity, sensitivity, limits of detection (LOD) and quantification (LOQ), precision, accuracy, and measurement uncertainty using a matrix blank (MB) against the phosphorus standard. Results: The Instrumental Detection Limit was 0.066 ppm and the Instrumental Quantification Limit was 0.22 ppm, respectively, while the phosphorus recovery and repeatability percent were 101.15% and 0.11%, respectively. However, the linearity of this method was 0.1 to 30 ppm. The measurement uncertainty of this method was 2.82%, following Commission Regulation (EC). Conclusion: The estimated parameters in the validation protocol, were found to meet the imposed performance criteria, and the procedure was validated for the intended use.

Rapid HPLC/MS/MS analysis of phenolic content and profile for mead quality assessment

The monitoring of phenolic compounds in mead is a useful tool for the evaluation of its quality and potential adulteration because the profile and content of phenolic compounds strongly depend on the amount and type of honey used for mead production and on the technological process. Therefore, the aim of this study was the optimization of rapid reversed-phase high performance liquid chromatography coupled to tandem mass spectrometry for the determination of 23 phenolic compounds in 22 mead samples. The isolation of monitored phenolic compounds was performed using liquid-liquid extraction with a mixture of diethyl ether and ethyl acetate. 3,4-dihydroxybenzoic, 4-hydroxybenzoic, caffeic, p-coumaric, salicylic, chlorogenic, gentisic, gallic and ferulic acids, together with apigenin, quercetin and 3,4-dihydroxybenzaldehyde were the most frequently occurred phenolic compounds in mead extracts. The instrumental limits of detection and quantification were for all compounds below 20 μg/L and 65 μg/L, respectively. Among the samples studied, four meads contained a low total amount of phenolic compounds (below 10 mg/L), and two of them did not even exceed 2 mg/L. Moreover, a very high concentration of vanillin as a flavouring was observed in one of those samples.

Use of selective quenching of a photoluminescent probe based on a Eu(III) β-diketonate complex for determination of methylmercury in produced water after liquid-liquid extraction

An Eu(III) β-diketonate complex was produced and employed as a photoluminescent probe to determine methylmercury (CH3Hg+). To establish its molecular structure, the Eu(III) complex was characterized by elemental (CHNS) and thermogravimetric analyses and infrared spectroscopy. After establishing robust conditions to use the Eu(III) complex as an analytical probe, it was employed for the analysis of produced water (PW) samples with the analytical response based on the luminescence suppression proportional to the concentration of CH3Hg+ (a linear model after normalization of the response within the concentration range from 0.2 μg L−1 up to 2.0 μg L−1). Selectivity was guaranteed by a simple liquid-liquid extraction of the analyte in dichloromethane, which also allowed a 50 times pre-concentration factor. The instrumental limit of quantification of 0.2 μg L−1 is equal to the limit established in Brazilian resolution for total mercury content in waters, but pre-concentration (50 times factor) improved the overall method limit of quantification down to 4 ng L−1. Recovery results agreed with the ones achieved using cold vapor atomic absorption spectrometry.

Analysis of hydrophilic per- and polyfluorinated sulfonates including trifluoromethanesulfonate using solid phase extraction and mixed-mode liquid chromatography-tandem mass spectrometry

Ultra-hydrophilic per- and polyfluorinated sulfonates (PFSA) are increasingly scrutinized in recent years due to their ubiquitous occurrence, persistence, and aqueous mobility in the environment, yet analysis remains a challenge. This study developed methods for the analysis of trifluoromethanesulfonate, perfluorobutanesulfonate, 10-camphorsulfonate, and a di-fluorinated sulfonate utilizing mixed-mode liquid chromatography, where all analytes were adequately retained and separated. Chromatography and electrospray ionization parameters were optimized; instrumental limits of quantification for the anionic target analytes were in the range of 4.3 - 16.1 ng L−1. Solid phase extraction (SPE) methods were developed using Oasis WAX cartridges; SPE recoveries for the analytes ranged from 86% to 125%. Salinity and total organic carbon both impaired the SPE performance to different extents, depending on the respective analyte. Utilizing widely accessible instrumentation and materials, this is a single method to simultaneously analyze conceivably the most hydrophilic PFAS chemical, i.e., trifluoromethanesulfonate, and moderately hydrophobic PFSAs.

Assessment of direct analysis in real time accurate mass spectrometry for the determination of triclosan in complex matrices

In this work, the applicability of direct analysis in real time coupled to accurate mass spectrometry (DART-MS) to the quantitative determination of triclosan (TCS) in samples with increasing complexity, from personal care products to extracts from sewage, is investigated. In the first term, DART-MS spectra of TCS as free phenol and as derivatized species are characterized; thereafter, the effects of several instrumental variables in the detectability of TCS (i.e., temperature, solvent, and compound holder) are discussed. Under final selected conditions, TCS was determined from its [M-H]− ions, without need of derivatization, attaining an instrumental limit of quantification of 5 ng mL−1, with a linear response range up to 1000 ng mL−1. Complex matrices, such as solid-phase extracts obtained from environmental water samples, moderately inhibited the ionization efficiency of TCS, with signal attenuation percentages in the range of 6 to 57%, depending on the sample type and on the concentration factor provided by the SPE procedure. The accuracy of results obtained by DART-MS was evaluated using liquid chromatography (LC) with MS detection; in both cases, a time-of-flight (TOF) MS instrument was employed for the selective determination of the [M−H]− ions of TCS (m/z values 286.9439 and 288.9410) using a mass window of 20 ppm. DART-MS did not only provide enough sensitivity to detect the presence of TCS in environmental samples (raw and treated wastewater as well as freeze-dried sludge), but also measured concentrations matched those determined by LC-ESI-TOF-MS, with only slightly higher standard deviations. During analysis of personal care products, containing much higher concentrations of TCS in a less complex matrix, both techniques were equivalent in terms of accuracy and precision.Graphical abstract

Analysis of Nucleosides (Adenosine and Cordycepin) in the Mushroom Samples by Liquid-Chromatography and Mass Spectrometry; HPLC-MS-MS

Cordyceps, a kind of precious natural crude drugs and edible mushrooms, were used as tonic food in East Asia area and enjoyed an extensive praise for its medicinal functions. Cordycepin exhibits various bio-activities, including anticancer, antibacterial, antiviral and immune regulation activities, and it’s been a significant focus of research. However, the preparation of high‑purity cordycepin remains challenging. Also, the molecular target with which cordycepin interacts to cause an antibacterial effect remains unknown. A simple and rapid isocratic chromatographic method (HPLC), optimum separation for (adenosine and cordycepin) analytes was achieved using the mixture of water and methanol as a mobile phase (85:15, v/v). The Photo-Diode Array Detector (DAD) WR, an auto injector, and a reverse phase column, Agilent Shield RP C18/4.6 × 150 mm, 4-micron and confirmation by LC/MSMS coupled with electrospray ionization (ESI) method for simultaneous separation and determination of adenosine and cordycepin in Cordyceps sinensis (Cs) and its substitutes was developed. Selective ion monitoring (SIM) mode ([M+/H]- at m/z 136, 267 and 252) was used for quantitative analysis of above components. The linearities for the 6 substances were studied in the range between 0.001 to 0.2 mg/L and the coefficients of determination (R2) were always > 0.999. Matrix effects were also assessed by comparing the slopes obtained in solvent and matrix. The recoveries for all the substances at 3 different spike levels (0.05, 0.10 and 0.20 mg/L) were in the range 70.50-108% with RSDs < 5%. The instrumental limits of quantification were in the range 0.013-0.016 mg/L, while the reporting level of the method was 0.004 mg/L for all the aforementioned compounds. The nucleoside contents of types of natural Cs and its substitutes were determined and compared with this developed method.

Exploring 20 eV electron impact ionization in gas chromatography-tandem mass spectrometry for the determination of estrogenic compounds

In electron ionization mass spectrometry (MS), the generation of characteristic fragmentation patterns allows reliable and sensitive identification of compounds. However, loss or a less intense signal of the molecular ion (or more diagnostic ions) can often be observed, which can be detrimental for identification and/or sensitivity, even when MS/MS approaches are applied for quantification. The benefits of applying lower ionization energy (i.e., 20 eV compared to 70 eV) using a gas chromatography (GC) - tandem MS (MS/MS) instrument were investigated in the detection of three estrogenic compounds, namely estrone (E1), 17β-estradiol (E2), and 17α-ethynylestradiol (EE2), emerging aquatic pollutants included in the European Commission Watch List. As expected, the relative intensity of molecular ions (M+.) or high-mass fragments closely related (M+.−CH3) increased significantly at 20 eV compared to 70 eV (from 4.6 % to 35.0 % for EE2, from 22.5 % to 87.3 % for E2, and from 76 % to 100 % for E1). This change in the spectrum profile led to an overall increase in the sensitivity of the compounds when detected using the multiple reaction monitoring mode. These results were compared with the instrumental limit of quantification obtained in liquid chromatography – MS/MS showing a limit of quantification of about 100-folds lower for GC-MS/MS and a completely neglectable matrix effect, thus posing the base for the development of a miniaturized sample preparation method (with an overall lower concentration factor) to achieve the challenging low limits of detection required by the EU regulation for estrogenic compounds.

Determination of phytochemical compounds in chicken breast by gas chromatography-tandem mass spectrometry.

A gas chromatography-tandem mass spectrometry (GC-MS/MS) method was developed for the simultaneous detection and quantification of five phytogenic compounds (carvone, menthol, thymol, carvacrol and methyl salicylate) in chicken breast. Chicken breast samples were analyzed using a QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) approach using acetonitrile as extraction solvent, followed by a d-SPE (dispersive-solid phase extraction) clean up step. The linearities for the 5 substances were studied in the range between 2 and 100 μg/L and the coefficients of determination (R2) were always > 0.995. Matrix effects were also assessed by comparing the slopes obtained in solvent and chicken breast matrix. The recoveries for all the substances at 3 different spike levels (5, 10 and 50 μg/kg) were in the range 80–102% with RSDs < 15%. The instrumental limits of quantification were in the range 2.7–4.8 μg/kg, while the reporting level of the method was 5 μg/kg for all the aforementioned compounds. The method was successfully applied to 10 chicken breasts samples from the local market.

A Rapid and Sensitive Method for the Determination of Cannabidiol in Cosmetic Products by Liquid Chromatography–Tandem Mass Spectrometry

Cannabidiol is a phytocannabinoid with proven pharmacological properties that is also used in the cosmetic industry for its sebostatic and antioxidant activities, being considered a new anti-aging ally. An analytical method is proposed for the determination of CBD in cosmetic products by liquid chromatography with tandem mass spectrometry, after leaching the CBD from the cosmetic matrix with ethanol. Low instrumental limits of detection (0.22 ng mL−1) and quantification (0.74 ng mL−1) allow the determination of CBD at trace levels without needing preconcentration, whereas the wide linearity of the method allows the determination of CBD in more concentrated samples without high dilution. The method was successfully applied to the analysis of six cosmetic products and a raw material. The proposed method is suitable for the quality control of cosmetic products containing CBD, being able to quickly and easily determine this compound, ensuring that its concentration in the finished product is the desired one.

Matrix effect challenges to quantify 2,4-D and fipronil in aquatic systems.

Fipronil and 2,4-D are two main pesticides of sugarcane cultivation in Brazil. While pesticides have helped to improve food quality and quantity, the continuous increase in usage has raised concerns over the unintended negative environmental impacts they introduce. Mesocosm systems are used as surrogate ecosystems to evaluate the fate, transport, and transformation of pesticides. Controlled experimental manipulations on mesocosms simulate the effects of stressors on the environment, in which the studies to evaluate effects on the living organisms and assess pesticide dynamics produce more realistic data than those obtained in the laboratory. However, analytical methods that follow mesocosm studies shall be robust enough towards sensitive variations in analyte concentration and matrix-induced effects of suppression or enhancement of analytical response. An analytical method using solid-phase extraction (SPE) along with liquid chromatography tandem mass spectrometry (LC-MS/MS) was developed for simultaneous determination of fipronil, 2,4-D, and their respective transformation products in aquatic systems. The method presented instrument quantification limits from 0.1 to 10.0ngmL-1 and recovery values from 14 to 101%, with a maximum relative standard deviation (RSD) value of 12%. In the matrix effect assessment, the majority of matrix proportions showed a statistically relevant matrix effect for all compounds (p < 0.05). The method was further applied to over 500 different samples from mesocosm systems during controlled pesticide application and conversion of pastureland into sugarcane cropland. 2,4-D and fipronil mesocosm concentrations varied from 5ngL-1 to 1.6mgL-1 and 0.3ngL-1 to 56μgL-1, respectively.

Development of a sensitive method for determining traces of prohibited acrylamide in cosmetic products based on dispersive liquid-liquid microextraction followed by liquid chromatography-ultraviolet detection

According to the European Regulation on cosmetic products, the presence of acrylamide in these consumer products is not allowed due to its mutagenic and potentially carcinogenic effects. Despite this ban, acrylamide might be present in those cosmetic products containing acrylamide-based polymers. However, there is no analytical method for its determination in this type of matrices. Based on this, the development of analytical methods for the determination of acrylamide in cosmetic products is required to guarantee consumer safety. In this work, an analytical method for determining traces of prohibited acrylamide in cosmetic products is presented for the first time. The method is based on dispersive liquid-liquid microextraction (DLLME), followed by liquid chromatography–ultraviolet (LC-UV) detection. A previous derivatization of acrylamide with 2-naphthalenethiol was performed to obtain a more lipophilic compound, and therefore, more extractable in the DLLME step, in addition to the bathochromic displacement of the measurement wavelength. The main variables involved in both derivatization and DLLME step were studied to provide the best enrichment factors. Under the optimized conditions, 6.5 mL of aqueous sample solution was cleaned-up from lipophilic matrix components by liquid-liquid extraction (LLE) using 3.5 mL of hexane. Then, 5 mL were taken and subjected to microwave derivatization with a mixture of 250 μL of 2-naphthalenethiol (0.5 mg mL−1) and 250 μL of di-sodium tetraborate (4 mg mL−1). Afterwards, it was subjected to DLLME by injecting a mixture of 250 µL of acetone (as disperser solvent) and 80 µL of chloroform (as extraction solvent). The extracts were evaporated to dryness, reconstituted in mobile phase and injected into the LC-UV system. The method was successfully validated showing good linearity (from 10 ng mL−1 to 20 µg mL−1), an enrichment factor of 103 ± 2, instrumental limits of detection and quantification of 3.0 and 9.8 ng mL−1, which, according to sample treatment, correspond to 0.7 and 2.4 µg kg−1 in the sample, respectively, and a good repeatability (RSD < 14%). Finally, the proposed analytical method was applied to the determination of acrylamide in commercial cosmetic samples of different nature with good relative recovery values (85 – 112%), which shows that the matrix effect is negligible. This method could help the cosmetic industry to control the cosmetic products containing potential acrylamide-releasing ingredients.

Optimization of a Digestion Method to Determine Total Mercury in Fish Tissue by Cold Vapor Atomic Fluorescence Spectrophotometry.

Several microwave-assisted digestion methods were tested at the Centro de Estudios Aplicados en Química laboratory in Quito, Ecuador, to determine the accuracy and performance efficiency of the mineralization process for the determination of total mercury in fish tissue by cold vapor atomic fluorescence spectrophotometry. The use of MARSEasyPrep high-pressure vessels, low amounts of reagents (1 cm3 HNO3, 1 cm3 H2O2, and 1 cm3 HClO4), an irradiation temperature of 210 °C, and 35 min of mineralization time resulted in accurate performance, with recoveries of certified reference material DORM-4 between 90.1% and 105.8%. This is better than the Association of Official Analytical Chemists 2015.01 method, which has a reported accuracy of 81%. The repeatability precision and intermediate precision were established at three concentration levels (0.167, 0.500, and 0.833 mg·kg−1) and expressed as the percentage of the relative standard deviation ranging from 1.5% to 3.0% and 1.7% to 4.2%, respectively. Further, the method was satisfactorily applied to analyze fortified samples of tilapia (Oreochromis niloticus), with recoveries ranging from 98.3% to 104.3%. The instrumental limits of detection and quantification were 0.118 µg·dm−3 and 0.394 µg·dm−3, respectively.

Occurrence of PAHs in water samples of the Diep River, South Africa

Occurrence of polycyclic aromatic hydrocarbons (PAHs) in freshwater may aggravate the water crisis currently being experienced in the Western Cape Province of South Africa. However, there is dearth of data on the levels of PAHs, which is necessary for effective assessment of water quality as well as remediation strategies. This study therefore assessed levels of PAHs in the Diep River freshwater system of Western Cape Province, South Africa. A liquid-liquid extraction solid-phase extraction gas chromatography flame ionisation detection (LLE-SPE-GC-FID) method was developed to simultaneously determine the 16 United States Environmental Protection Agency (USEPA) listed priority PAHs in water samples. The SPE-GC-FID method allowed an acceptable linearity (R2 &gt; 0.999) within the calibration range of 1 to 50 µg/mL. Instrument detection limits ranged between 0.02 and 0.04 µg/mL and instrument quantification limits between 0.06 and 0.13 µg/mL. Recovery study results were also acceptable (83.69–96.44%) except for naphthalene, which had recovery of 60.05% in spiked water matrix. The seasonal averages of individual PAH detected at the studied sites ranged between not detected (nd) and 72.38 ± 9.58 µg/L in water samples.