Acid Analysis Research Articles

Abstract B53: Extracellular vesicle-based liquid biopsy via lipid-based nanoprobes

Abstract Extracellular vesicles (EVs) can mediate intercellular communication by transferring cargo proteins and nucleic acids between cells. The pathophysiologic roles and clinical value of EVs are under intense investigation, yet most studies are limited by technical challenges in the isolation of nanoscale EVs (nEVs). Here, we report a lipid-nanoprobe system that enables spontaneous labeling of nEVs for subsequent magnetic enrichment in 15 minutes, with isolation efficiency and cargo composition similar to what can be achieved by the much slower and bulkier method of ultracentrifugation. We also show that this approach allows for downstream analyses of nucleic acids and proteins, enabling the identification of EGFR and KRAS mutations following nEV isolation from the blood plasma of non-small cell lung cancer patients. The efficiency and versatility of the lipid-nanoprobe approach open up opportunities in point-of-care cancer diagnostics. Citation Format: Siyang Zheng, Hongzhang He, Faming Wang, Yuan Wan. Extracellular vesicle-based liquid biopsy via lipid-based nanoprobes [abstract]. In: Proceedings of the AACR Special Conference on Advances in Liquid Biopsies; Jan 13-16, 2020; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(11_Suppl):Abstract nr B53.

Biomarker screening for the early detection of prostate cancer using an exosomal-enrichment RNA liquid biopsy test.

e15553 Background: Prostate cancer is one of the most common cancers in men, with approximately 10% of all new cancer cases and ~5% of all cancer deaths in 2019. The standard test for prostate cancer is the Prostate Serum Antigen (PSA) test. The PSA test suffers from low specificity (20-40%) in patients including ‘grey zone’ levels (4-10 ng/mL); moreover, the PSA test fails to identify patients with high-risk cancers. Previously we developed ExoDx Prostate Intelliscore (EPI), a urine-based exosome prostate cancer test optimized to rule out the need for a biopsy (risk stratification for high-grade prostate cancer). This study utilized a next generation exosome-based test that specifically enriches a subtype of prostate cancer exosomes from urine. Early detection of prostate cancer via a non-invasive method is desirable and the identification of patients with high-risk cancer is critical. Here we describe the development of a prostate-specific urinary exosome test for the identification of patients with prostate cancer. Methods: We have developed a prostate-specific enrichment method to isolate exosomes of prostate origin from urine samples. Using an affinity-based method against surface marker proteins found on prostate cells, we were able to selectively enrich for exosomes shed by the prostate gland with demonstrated specificity. Subsequent analysis of exosomal nucleic acids enables a promising panel of gene expression biomarkers capable of distinguishing patients with prostate cancer from healthy individuals. Results: RNA from prostate cancer enriched exosomes was compared to total exosomes from urine. Enrichment of prostate cancer specific exosomes significantly enhanced the RNA signature compared to total urine exosomes. Conclusions: Prostate cancer tests have recently been developed for RNA signatures in urine. Exosomes provide a source of nucleic acids as they are actively shed continuously from living cells as part of their normal life cycle. The urine exosomes can be used for total RNA transcriptome analysis and are therefore a very rich source of biomarkers for prostate cancer that can be tailored to different clinical indications. An affinity-based enrichment for tissue-specific exosomes allow for better resolution of the gene expression profile from the tissue of interest and reduces the RNA targets from non-relevant processes of the bladder and kidneys. The gene signature identified in this ongoing study could potentially provide a non-invasive molecular means for the early diagnosis of prostate cancer.

Interspecific difference in N:P stoichiometric homeostasis drives nutrient release and soil microbial community composition during decomposition

Tree species can produce litter with large variation in nitrogen to phosphorus (N:P) ratios. Here we examined how litter N:P ratios affected decomposer community composition and nutrient release for two contrasting tree species in the Qinling Mountains, China. Two-year-old Quercus aliena var. acuteserrata and Pinus tabulaeformis seedlings were fertilized using nutrient solutions with varying N:P ratios for four months. The obtained litters with contrasting N:P stoichiometry were left to decompose on nutrient-free quartz sand for 12 weeks with microbial inoculum. Then, the post-decomposition microbial community composition was determined using a phospholipid fatty acid (PLFA) analysis. The Q. aliena litter stoichiometry was more homeostatic than P. tabulaeformis litter. Litter N:P ratio was significantly related to litter nutrient loss and mass loss for P. tabulaeformis but not always for Q. aliena. The soil microbial community compositions showed larger fungal to bacterial (F:B) ratios with increasing litter N:P ratios for Q. aliena but not P. tabulaeformis. Litter N:P ratio, as determined by species-specific homeostasis, showed an interspecific difference to affect the patterns of litter decomposition dynamics, as well as related soil microbial community composition. The less variation in the soil microbial community composition than plant litter stoichiometric characteristics during decomposition is likely an important mechanism that regulates the balance of biogeochemical cycles in the Qinling Mountains.

Application of the “fast” gas chromatography method for regular analysis of fatty acids in milk and dairy products

The paper presents one of the approaches for identifying fatty acids using gas chromatography, which significantly reduces the analysis time, and is equally effective when compared with the traditional method of studying the fatty acid composition. The determination of the composition of fatty acids today is a guarantee of quality in identifying various conformations and modifications of milk fat, the bioactive properties of individual acids of the omega-3 and omega-6 families, etc. Moreover, this method is time-consuming, therefore, the goal of this work is to optimize the parameters of this methodology for quick and regular analysis of fatty acid composition in laboratories and dairy enterprises. The analysis of the fatty acid composition was carried out using two columns with different stationary phases. A comparative evaluation of the analytical characteristics was carried out on two capillary chromatographic columns: SP-2560 100 ? 0.25 mm ID, 0.2 ?m with a stationary phase FFAP (traditional) and a gas chromatographic column BPX-70: stationary phase 70% cyanopropylphenyl dimethylpolysiloxane, 10 m ? 0.1 m ? 0.20 ?m. Detection was carried out using a flame ionization detector. A mixture of Supelco® 37 FAME Mix fatty acid methyl esters and Sigma-Aldrich methyl decanoate analytical standard was used as the standard. For data processing, the NetChrom software was used, the composition of fatty acid methyl esters was calculated by the internal normalization method. The analysis time of the first column was 49.07 minutes, for the second 8.44, respectively. The use of a stationary phase column of cyanopropylphenyl dimethylpolysiloxane significantly reduced the analysis time when eluting a complex composition of fatty acids. The studies were carried out using modern analytical techniques and arbitration methods of analysis in the laboratory of technochemical control of the All-Russian Scientific Research Institute of the Dairy Industry. This adapted analysis method will be of interest to specialists in the field of laboratory research and processing enterprises.

CHARACTERISTICS OF MILK FAT OF GREY UKRAINIAN CATTLE BREED

CHARACTERISTICS OF MILK FAT OF GREY UKRAINIAN CATTLE BREED

Compound-specific stable isotope analyses in Falkland Islands seabirds reveal seasonal changes in trophic positions

BackgroundWhile nitrogen and carbon stable isotope values can reflect ecological segregation, prey choice and spatial distribution in seabirds, the interpretation of bulk stable isotope values is frequently hampered by a lack of isotopic baseline data. In this study, we used compound-specific isotope analyses of amino acids (CSIA-AA) to overcome this constraint and to study interspecific differences, seasonal and historical changes in trophic positions of five seabird species, three penguins and two petrels, from a sub-Antarctic seabird community.ResultsCSIA-AA allowed comparing trophic positions of seabirds with temperate and polar distributions. Gentoo and Magellanic penguins had the highest trophic positions during the breeding season (3.7 and 3.9), but decreased these (2.9 and 3.3) during the feed-up for moult. Intra-specific differences were also detected in Thin-billed prions, where carbon isotope values clearly separated individuals with polar and temperate distributions, both in the breeding and interbreeding periods. Thin-billed prions that foraged in polar waters had lower trophic positions (3.2) than conspecifics foraging in temperate waters (3.8). We further investigated historical changes by comparing museum samples with samples collected recently. Our pilot study suggests that Rockhopper penguins, Magellanic penguins and Thin-billed prions with temperate non-breeding distributions had retained their trophic levels over a 90–100 year period, while Gentoo penguins and Thin-billed prions with polar non-breeding distributions had decreased trophic levels compared to historical samples. In contrast, Wilson’s storm-petrels had slightly increased trophic levels compared to samples taken in 1924–1930.ConclusionsWe applied compound-specific stable isotope analyses across a range of contexts, from intra-specific comparisons between stages of the breeding cycle to inter-specific seabird community analysis that would not have been possible using bulk stable isotope analyses alone due to differences in isotopic baselines.

Application of MAP and ethylene\u2013vinyl alcohol copolymer (EVOH) to extend the shelf-life of green and white asparagus (Asparagus officinalis L.) spears

In this study, ethylene vinyl alcohol copolymer (EVOH) and polypropylene/polyethylene (PP/PE) films combined with MAP packaging were developed to enhance the shelf-life of green and white asparagus spears. The scope of the research included measurements of weight loss, pH, acidity, color, texture, and sensory analysis as indicators of green and white asparagus spear quality for up to 17 days of storage at 2 and 10 °C. The application of modified atmosphere packaging combined with EVOH-based packaging material and refrigeration at 2 °C promoted a reduction in asparagus weight loss, preventing changes in color and texture as well as sensory quality, thereby extending the shelf-life of the asparagus. According to the obtained results, it was possible to maintain good quality of green and white asparagus for up to 17 and 10 days, respectively, when packed in MAP using EVOH-based packaging stored at 2 °C. Asparagus stored in packaging with PP/PE film showed lower quality during storage at 2 and 10 °C. These results suggest that EVOH films are potential candidates for advanced packaging materials for the asparagus packaging application.

Elevated maternal linoleic acid alters placental fatty acids, nutrient transporters and inflammatory proteins

Linoleic acid (LA) is the major omega‐6 fatty acid which is obtained from our diet. During pregnancy, LA is required for adequate fetal growth and development. For the growing fetus LA can only be obtained from the maternal diet, and is transferred from the maternal to fetal circulations by the placenta. At this time, in Western societies, we are overconsuming LA during pregnancy. Omega‐6 is metabolised by FADS1 and FADS2, which also metabiolise omega‐3. The ratio of omega‐6 to omega‐3 is important for human health, as they are proinflammatory and anti‐inflammatory, respectively. Therefore, the aim of this study is to determine if elevated maternal LA during pregnancy is alters placental fatty acids, nutrient transporter gene expression and inflammatory proteins.Female Wistar Kyoto rats were fed a diet low in LA (LLA‐1.44% of energy) or diet high in LA (HLA‐6.21% of energy) for 10 weeks before and during gestation. Following mating with a male consuming normal chow, offspring and maternal rats were sacrificed at embryonic day (E)20, and placenta were collected for analysis of placental fatty acids, nutrient transporters and inflammatory markers.In isolated placenta from pregnancies where mothers consumed an elevated LA diet, the concentration of LA was increased and the concentration of the omega‐3 fatty acid a‐linoleinic acid was decreased. Of interest, the downstream metabolite of LA, arachidonic acid was not altered in placenta from mothers consuming an elevated LA diet. mRNA expression of slc27a1 (fatty acid trasnport protein 1) was significantly downregulated in the male placenta from the dams fed with HLA, but not females. The mRNA expression of slc2a1 (glucose trasnporter 1) was significantly decreased in both male and female placenta from mothers fed the HLA diet. Further, the protein concentration of interleukin‐7 (IL‐7) was significantly decreased in both male and female placenta (labyrinth) from the dams fed with HLA, however there were no changes in protein expression of IL‐6 and TNF‐α in the labyrinth.In conclusion, a maternal diet high in LA alters fatty acid concentrations, nutrient transporters and inflammatory cytokines in the placenta. The consequences of this on offspring development, and therefore long term health require further investigation.Support or Funding InformationAllen Foundation (USA)

PHYSICOCHEMICAL AND MICROBIOLOGICAL EVALUATION OF HONEYS CONSUMED BY THE ELDERLY

Objective: to analyze physicochemical, microbiological and dirt parameters in marketed honeys, consumed by the elderly cared for at Integrated Health Center in Teresina, Piauí, Brazil. Method: the following analyses were performed: color, water activity, humidity, ash, pH, acidity, reducing sugars, total sugars, apparent sucrose and insoluble solids. Contamination indicator bacteria, mesophilic microorganisms, filamentous fungi and yeasts, as well as dirt and foreign matter, performed in the period from April to June 2016. Results: analyses of ash, pH, acidity and insoluble solids were outside current standards. Microbiological analyses did not present significant contamination. Also, analyses of dirt showed insect fragments, foreign matter in almost all the samples. Conclusion: parameters of ash, pH, acidity and insoluble solids, as well as dirt and foreign matter, indicated that the samples were not in accordance with current legislation.

Изучение влияния жирнокислотного состава свинины на процесс ферментации

Introduction. Dry fermented meat products are considered to be fine foods. Their quality depends on a combination of various processes. The composition and properties of raw materials, e.g. fat, play a key role in quality formation. The research objective was to study the fermentation process in fourth-category pork obtained from sows, which contains a lot of highly unsaturated fatty acids. The considerable resources that this raw material can provide require improved technologies.
 Study objects and methods. The research featured two types of pork. The first group included samples made from fourth-category carcasses, i.e. hip muscle tissue and spine fat, in the ratio of 85:15. The second group included control samples made from secondcategory pork that was obtained from young animals. This type of meat is traditionally used for fermented products. The fermentation process was performed using starter cultures for rapid fermentation of StLb 37.03 M (0.1% by weight of raw materials). The samples were fermented at the activation temperatures of the starter cultures for 48 h. After that, the samples were dried at 50°C with shortterm smoke supply for 1 h. The total time of the production cycle was 14 days. The samples were monitored for water activity, pH, weight loss, chemical composition, amount of free fatty acids, secondary and primary oxidation products, color characteristics, and sensory properties during all stages of the process.
 Results and discussion. The content of unsaturated fatty acids was 65.39% of the total amount of fatty acids in the fourth-category pork obtained from sows. In the second-category pork obtained from young animals, it was 59.1%. Water activity, pH, and moistureprotein ratio were within the control criteria for shelf stable products. The analysis of thiobarbituric values and free fatty acids indicated a deeper degradation of the fat part, but their values were comparable to those of the control group. The sensory properties of fourth-category fermented pork were highly evaluated by experts.
 Conclusion. The obtained data proved the possibility of using fourth-category raw materials in the technology of fermented delicatessen products.

OPTIMIZATION AND VALIDATION OF AN ANALYTICAL METHOD FOR TRANEXAMIC ACID IN WHITENING CREAMS BY RP-HPLC WITH PRECOLUMN DERIVATIZATION

Objective: An efficient and selective analytical method with precolumn derivatization using reverse-phase high-performance liquid chromatography(RP-HPLC) was developed for the analysis of tranexamic acid in whitening creams.Methods: Derivatization was performed using 1% ninhydrin solution in methanol as a derivation agent to form a colored Ruhemann’s purple product.The analytical conditions included the use of a C18 column as the stationary phase and a methanol: acetate (20 mM) buffer at pH 4 (75:25) as themobile phase, with a flow rate of 0.8 mL/min and UV–visible detection at a wavelength of 570 nm.Results: The average retention time of the tranexamic acid derivative was 5.413 min. The results of the calibration curves were linear, with acorrelation coefficient (r) of 0.9993 at a concentration ranging from 8 to 48 μg/mL. The recovery was between 99.26% and 101.77%. The limits ofdetection and quantification were 1.87 μg/mL and 6.25 μg/mL, respectively.Conclusion: The analytical method developed in this study met the validation requirements and included a simple and efficient derivatization methodapplicable for the selective analysis of tranexamic acid in whitening creams.

Evaluation of phytotherapeutic activities and phytochemical content of Phormidium autumnale Gomont from natural freshwater sources.

The information available on microalgae-sourced compounds, especially antibiotics and other bioactive compounds, and their potential commercial applications is still insufficient. In this study, antibacterial activity, metabolites, and molecular characterization of Phormidium autumnale, which was isolated from samples collected from different natural freshwater sources in Ankara, Turkey, were investigated. Sequencing results of 16s rDNA confirmed the molecular identification of P. autumnale by 99%. It was determined that the peak values of some phenolic compounds and cyclic peptides were consistent with the 1653-1389cm-1 band regions in the FTIR spectra of the species. The antibacterial activities of P. autumnale cyanobacteria (CBA) extracts that were obtained by using different solvents were tested on Escherichia coli, Staphylococcus epidermidis, methicillin-resistant (MR) Staphylococcus aureus, Streptococcus agalactiae, and Enterococcus faecalis by using a disc diffusion method. Also, the minimum inhibition concentration (MIC) and antimicrobial indexes of all extracts were determined. It was found that P. autumnale methanol extracts showed antibacterial activity on all test bacteria, whereas acetone extracts showed effects only on E. coli. For the inhibition of MR S. aureus, the control methanol extract was found to give very similar results to those exhibited by the control antibiotics, and the antimicrobial index results were determined to be 58.7-67.5%. According to the results of the analysis of methanol extract, gentisic acid, vanillic acid, 4-hydroxybenzoic acid, p-coumaric acid, and catechin (especially phenolic compounds) were determined to be the active compounds. It can be concluded that P. autumnale is an alternative to current commercial applications as an antibacterial agent in phytotherapy.

PHYTOCHEMICAL EVALUATION OF ARTOCARPUS HIRSUTUS LAM. FRUIT EXTRACT: A POTENTIAL WILD ENDEMIC PLANT

Objective: The present study includes the qualitative and quantitative estimation of phytochemical constituents and HPTLC (High-performance thin layer chromatography) analysis of phenolic acids in the fruit extract of Artocarpus hirsutus.
 Methods: Qualitative and quantitative analysis of Artocarpus hirsutus methanol fruit extract using standard methods. HPTLC analysis was performed by the CAMAG HPTLC system (Switzerland) for gallic acid, caffeic acid and ferulic acid determination.
 Results: The Preliminary phytochemical analysis revealed the presence of phytoconstituents such as flavonoids, phenols, tannins, steroids, glycosides, alkaloids, carbohydrate and protein. The methanol fruit extract has high carbohydrate content (267±0.02 mg/g FW). And good amount of protein, phenol, flavanoid were also found. The results of mineral studies shows that elements such as potassium (1.601%) and nitrogen (1.4%) were present in higher quantity. The result showed the presence of caffeic acid within peak 7 with an Rf (Retension factor) value 0.49, ferulic acid within peak 8 with an Rf value 0.60, and gallic acid within peak 5 with an Rf value 0.25.
 Conclusion: The results indicated that the Artocarpus hirsutus fruit contains an appreciable amount of bioactive compounds.

Isotope applications to soil science at the University of Alberta — an historical perspective

For the past 70 yr, researchers in the Soil Science/Renewable Resources Department at the University of Alberta have used isotopes to study topics of ecological importance. This review highlights the soil isotope research conducted within our department over this time, including an historical overview of studies of interest. Analytical techniques and advances in instrumentation are discussed, focusing on the measurement of light stable isotope ratios (i.e., for C, H, N, S, and O) using isotope ratio mass spectrometry (IRMS). Early soil isotope work (1950–2000s) focused on agricultural soils and soil fertility issues. These studies included the use of radioactive isotopes such as 14C and 35S, and (or) artificially enriched stable isotopes including 15N-labelled fertilizers. More recently (2000–present), the scope of research widened to include natural-abundance stable isotope ratio studies as higher-sensitivity IRMS systems became more prevalent. Current isotope research topics include N biogeochemistry in natural and managed ecosystems, land management effects on greenhouse gas emissions, carbon cycling in northern landscapes, paleo-reconstruction in peatlands, carbon sequestration in boreal forests, and biodegradation of petroleum hydrocarbons. Further technological progress also enabled new techniques such as compound-specific IRMS analysis, including δ13C and δ2H measurements of soil n-alkanes and phospholipid fatty acids. In conclusion, current IRMS instrumentation presents unparalleled opportunities for multidisciplinary research to track carbon, plant nutrients, and pollutants as they move through soils.

SEARCH FOR A SOURCE OF TRITERPENE ACIDS IN RUSSIAN BIRCHES

The composition of triterpene acids and triterpene alcohols of the outer bark of a damaged silver birch tree (Betula pendula Roth.) the outer bark of silver birch branches, the outer bark of Betula davurica Pall., B. mandshurica (Regel) Nakai, B. platyphylla Sucacz. and B. costata Trautv. is considered. Silver birch bark was harvested in the Leningrad region. The bark of other species of birches was harvested in the Khabarovsk region. The qualitative composition of triterpene compounds was determined by chromatography-mass spectrometry. The quantitative composition was determined by gas-liquid chromatography and absolute calibration. Butyl esters of acids were preliminarily prepared for GLC analysis of triterpene acids. The outer bark of the eastern species of birches contains significantly more betulinic and oleanolic acid than silver birch. The relative content of triterpene acids is greater in the outer bark of branches and in the bark of damaged silver birches. The increase in acid content is apparently associated with the desire to heal a wound. The main component among the triterpenoids of the investigated raw materials is betulin. For the separation of acids from other triterpenoids, various solubilities of the compounds in solvents and the ability of acids to form poorly soluble salts were used.

Computational analysis of amino acids\u2019 adhesion to the graphene surface

The mechanisms of cellular growth have attracted scientists’ attention for a long time, leading to recent efforts in establishing cellular growth on specific functionalized substrates. In order to fully understand the supported cellular growth mechanisms, one needs first to comprehend how individual amino acids interact with the substrate material as cells are known to attach to surfaces through specific proteins designed to improve adhesion. In this study, we have considered graphene as a candidate material for support-assisted cellular growth and simulated the interaction of all 20 naturally occurring amino acids deposited on graphene. Investigations utilized classical molecular dynamics (MD) for amino acids in aqueous solution and in vacuo, in tandem with quantum chemical calculations. The MD simulations were carried out for classical and polarizable CHARMM force fields. The simulations performed with the polarizable force field confirmed that adhesion of amino acids to the graphene surface may be significantly enhanced due to the polarization forces, which was further supported by quantum chemical calculations. The performed analysis thus revealed the role of polarization on amino acids’ adhesion to the graphene surface.Graphical abstract

Sensitive determination of urinary muconic acid using magnetic dispersive-solid-phase extraction by magnetic amino-functionalised UiO-66

ABSTRACT In this study, a magnetic-dispersive solid-phase extraction (DSPE) was developed for the extraction and desorption of muconic acid from real urine sample. For this purpose, Fe3O4-SiO2-NH2@ UiO-66 was used as a Metal-Organic Framework (MOF) in the DSPE for extraction of the analyte of interest followed by High-Performance Liquid Chromatography (HPLC) analysis. The synthesised magnetic-MOF was characterised by XRD, VSM, FT-IR, and FE-SEM techniques. The experimental parameters influencing the magnetic-DSPE procedure, such as solution pH, initial sample volume, extraction and desorption time, type and volume of elution solution, and sorbent amount were examined. Under the optimal conditions, the UiO-magnetic DSPE-HPLC procedure provided a good limit of detection (0.001 µg mL−1), the limit of quantification (0.003 µg mL−1), wide linear dynamic range (0.003–25 µg mL−1) and high correlation coefficient (r2: 0.997). Also, the Fe3O4- SiO2- NH2@ UiO-66 exhibited an acceptable accuracy (2.0–4.0%), reproducibility (3.7–6.1%), and per cent recovery (96–98%) for the extraction and desorption of the desired analyte. It can be concluded that the proposed method was efficient for the extraction and analysis of muconic acid from real urine samples. Therefore, the Fe3O4- SiO2- NH2@ UiO-66 – DSPE-HPLC method can be used as a simple, fast, sensitive, reusable, and user-friendly extraction technique to determine trace levels of urinary muconic acid.

Optimizaziya metodiki analiza svobodnych zhirnych kislot s pomosch'yu kombinazii MALDI-mass-spektrometrii i technologii polucheniya monosloev Lengmyura

Optimizaziya metodiki analiza svobodnych zhirnych kislot s pomosch'yu kombinazii MALDI-mass-spektrometrii i technologii polucheniya monosloev Lengmyura

ANALISIS KANDUNGAN ASAM ASKORBAT PADA TANAMAN KANGKUNG (Ipomoea reptana Poir), BAYAM (Amaranthus spinosus), dan KETIMUN (Cucumis sativus L)

Plants have a defense mechanism against increasing oxidative compounds formed due to drought stress. One of the compounds forming these compounds is ascorbic acid. Ascorbate is the main metabolite compound in plants that has an antioxidant function, which protects plants from oxidative damage resulting from aerobic metabolism. The aim of the study was to standardize and analyze the content of Ascorbate (ASA) on the leaves of kale (Ipomoea reptana Poir), spinach (Amaranthus spinosus) and cucumber (Cucumis sativus, L). The method used was 0.5 g leaf samples were crushed with 5% metaphosphoric acid. The solution obtained was titrated with dichlorophenol-indophenol (DCIP) 0.8 g / l. Treatment analysis of ascorbic acid (ASA) content in this plant tissue which has the largest ascorbic acid content in cucumber plants (Cucumis sativus L) of 69855.85; then followed by spinach plants (Ipomoea reptana Poir) at 66517.24 and finally in spinach (Amaranthus spinosus) at 38859.13. And the ASA mg standard 308.

Determination of perfluoroalkyl carboxylic acids in environmental water samples by dispersive liquid–liquid microextraction with GC-MS analysis

The present study focused on developing a rapid, efficient, and eco-friendly method for the analysis of perfluoroalkyl carboxylic acids (PFCAs) in aqueous matrices. The proposed method was based on esterification of PFCAs by isobutyl chloroformate followed by dispersive liquid–liquid microextraction (DLLME) of the derivatives. Quantitation of the isobutyl esters of PFCAs was carried out by gas chromatography-mass spectrometry with electron ionization. Under the optimal conditions, PFCAs could be determined in linear ranges of 1–1000 ng mL−1 with good correlation coefficients (r > 0.991). The limits of detection and limits of quantification ranged from 0.9 − 3.0 ng mL−1 and 2.7 − 9.0 ng mL−1, respectively. The method showed satisfactory reproducibility with intra-day and inter-day relative standard deviations (RSDs) in the range of 3.4 − 14.6% and 3.5 − 17.2%, respectively. It was successfully applied to determine PFCAs in several river and lake waters, ranging from 8.47 to 150.14 ng mL−1.