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1

Metabolomic analysis of biological material using LC-MS in the quest for urinary system cancer biomarkers - review

Szuberla Wiktoria, Wrona Maria

Chemical Technology & Biotechnology

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2024

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Vol. 4

70--75

EN

Renal cell carcinoma (RCC) and bladder cancer (BC) are among the most frequently diagnosed urinary system cancers worldwide. They are characterized by high mortality and recurrence rates. In response to the rising incidence and mortality rates, scientists are exploring innovative diagnostic and therapeutic methods. Metabolomics, which analyzes metabolite levels, may enable early diagnosis and monitoring of therapy progress. Compared to other omics technologies, it focuses on the outcomes of metabolite activity, providing a unique perspective on processes occurring in cancer cells. Metabolomic analyses utilize techniques such as mass spectrometry. These methods allow the identification of biomarkers and precise determination of the chemical composition of biological samples. However, the most commonly used method is liquid chromatography-mass spectrometry (LC-MS), which enables the most comprehensive screening of cancer metabolomes. Recent studies show significant progress in recognizing characteristic metabolites associated with urological cancers, although this area remains partially unexplored. Research on circulating metabolites, especially those present in easily accessible samples like blood or urine, demonstrates promising potential in clinical practice. Study results reveal differences in metabolic profiles between various stages of cancer development, which may have clinical significance. The future of this field involves an increasing number of clinical cohorts, standardization of sample preparation, and further improvements in instrument sensitivity and speed. LC-MS-based metabolomics has the potential to contribute to the improvement of diagnostics, therapy, and the quality of life of patients with some urological cancers. However, challenges, such as the lack of uniform methodologies and understanding of metabolite determinants, require further research and innovation.

2

Niskie stężenia, skomplikowane matryce - oznaczanie neonikotynoidów w próbkach środowiskowych i w żywności

Haliński Łukasz, Łukaszewicz Paulina

Laboratorium - Przegląd Ogólnopolski

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2023

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nr 2

27--34

PL

Neonikotynoidy to insektycydy powszechnie występujące w środowisku oraz w żywności. W artykule opisano podstawowe metody ich ekstrakcji z różnych matryc oraz identyfikacji i analizy ilościowej przy użyciu techniki LC-MS/MS. Omówione zostały także podstawowe problemy w analizie obejmujące niskie stężenia związków, wpływ matrycy na wyniki, a także ograniczenia związane z jonizacją tych substancji.

EN

Neonicotinoids are insecticides commonly detected in the environment and in food samples. The article describes the most common methods of their extraction, identification and quantitative analysis using the LC-MS/MS approach. Difficulties in analytical procedures, including very low concentrations of analytes, matrix effects and limited ionisation in ESI-MS are also briefly discussed.

3

CF–PK–PD analysis of natural hemostatic compounds from Toddalia asiatica (Linn) Lam root bark in rats

Zhang Xiaoyan, Liu Jie, Sun Wenbo, Shen Xiangchun, Gong Xiaojian, Wang Cong, Liang Yan, Zhou Wei

Acta Chromatographica

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2021

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Vol. 33, no. 3

261--269

EN

Natural hemostatic compounds from Toddalia asiatica (Linn) Lam (T. asiatica) root bark had been investigated by a novel strategy, chemical fingerprint–pharmacokinetic–pharmacodynamic (CF–PK–PD) for the first time in this study. The extract sample of T. asiatica root bark was subdivided into petroleum ether (PE), ethyl acetate (EA) and n-butanol (n-B) sample by reagent extraction, EA sample showed significant hemostatic activity using prothrombin time (PT), activated partial thromboplastin time (APTT) and fibrinogen (FIB) as evaluation indexes from rat plasma of PK experiment in hemorrhagic rat model. CF analysis was adopted to assist us to discover six natural compounds from T. asiatica root bark in actual rat plasma after sample treatment by Ultra Performance Liquid Chromatography-Electrospray Ionization (UPLC-ESI) MS, there were only lomatin and 5-methoxy-8-hydroxy psoralen showing significant hemostatic effect (P < 0.05) mainly through endogenous coagulation pathway and fibrinolytic system. In PK–PD study, six compounds in EA sample exhibited relatively rapid absorption and slow elimination characteristics. The mean Tmax and t1/2β of isopimpinellin and pimpinellin were 1.74 and 0.59 h, 5.31 and 6.89 h in rats. On the basis of Sigmoid–Emax model, PK–PD related curves of FIB in hemorrhagic rat model after treatment of T. asiatica root bark were obtained. Predicted Emax, EC50 and ke0 of FIB under isopimpinellin were 4.87 mg/mL, 1.39 μg/mL and 0.81 1/h; predicted Emax, EC50 and ke0 of FIB under pimpinellin were 4.29 mg/mL, 2.47 μg/mL and 0.77 1/h. In conclusion, hemostatic compounds from T. asiatica root bark had been materialized, there were lomatin, isopimpinellin, pimpinellin and 5-methoxy-8-hydroxy psoralen at least as its main active substances through coagulation pathways and fibrinolytic system. CF–PK–PD method as a promising method was worthy of follow-up opening, application in pharmaceutical research.

4

Characterization of lacosamide metabolites by UHPLC–ESI–HRMS method

Gawlik Maciej, Skibiński Robert, Komsta Łukasz

Acta Chromatographica

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2020

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Vol. 32, no. 2

107--116

EN

In this study, the in vitro phase I metabolism of lacosamide was characterized with the use of ultra-high-performance liquid chromatography combined with high-resolution mass spectrometry (quadrupole time-of-flight). The use of two metabolism simulation techniques (photocatalysis and human liver microsomes) allowed the characterization of a polar metabolite of parent compound, not yet described. The experiment with the participation of HLM gave the ability to describe the full liver metabolic pathway of lacosamide. It has been proven that this molecule undergoes deacetylation, demethylation, and during liver tissue metabolism. Photocatalysis with the use of a TiO2 catalyst was proved to be a complementary technique in mimicking in vitro drug metabolism.

5

UPLC, HR-MS, and in-silico tools for simultaneous separation, characterization, and in-silico toxicity prediction of degradation products of atorvastatin and olmesartan

Rakibe U., Tiwari R., Rane V., Wakte P.

Acta Chromatographica

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2019

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Vol. 31, no. 1

33--44

EN

The aim of this work was to simultaneously separate, identify, and characterize all the degradation products (DPs) of atorvastatin (AT) and olmesartan (OM) formed under different stress conditions as per International Conference on Harmonization (ICH) Q1A(R2) guideline. AT showed labile behavior in acidic, basic, neutral, and oxidative stress and led to the formation of two DPs, while OM degraded under acidic, basic, and neutral and resulted in the formation of four DPs. All the stressed samples of AT and OM were resolved on a C-18 column in single run on a gradient liquid chromatographic (LC) mode. A complete mass fragmentation pathway of both the drugs was established with the help of tandem mass spectrometry (MS/MS) studies. The fragmentation was further supported by MSn studies, and for AT, it was carried out up to MS6, while for OM, it was up to MS5. Then, the stressed samples were analyzed by LC–MS/MS to get the fragmentation patterns of DPs. LC–MS/MS data helped to propose chemical structure of all the DPs. Based on this entire information, degradation pathway of both the drugs was established. The developed method has shown excellent linearity over the range of 10 to 150 μg/mL of OM and AT. The correlation coefficient (r2) for OM and AT is 0.999 and 0.998, respectively. The main recovery value of OM and AT ranged from 99.97% to 100.54%, while the limit of detection (LOD) for OM and AT was 0.018 and 0.021 μg/mL, and limit of quantitation (LOQ) was found to be 0.051 and 0.063 μg/mL. Finally, the in-silico carcinogenicity, mutagenicity, and hepatotoxicity predictions of AT, OM, and all the DPs were performed by using toxicity prediction softwares, viz., TOPKAT, LAZAR, and Discovery Studio ADMET, respectively.

6

Photocatalysis combined with chromatographic methods as a new promising tool in drug metabolism studies – a review

Gawlik M., Skibiński R., Trawiński J., Komsta Ł.

Acta Chromatographica

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2018

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Vol. 30, no. 1

1--8

EN

The number of new drugs launched to the market is constantly increasing; however, the metabolism of many of them is still not fully established. The knowledge of drug metabolism pathways is crucial for the efficacy and safety of therapies and, in classical approach, requires the use of animals as well as human volunteers, but this kind of research is expensive and time-consuming. Therefore, nowadays, more and more biological and chemical in vitro methods are developed for the drug metabolism study. This review is focused on the photocatalytic degradation of chemicals and the application of this process in chromatographic methods of drug metabolism research. A theoretical background of photocatalysis and all its applications in a drug metabolism study were reviewed, and other in vitro methods that are actually used were summarized and discussed. Other analytical methods used in this area were also discussed and compared.

7

Znaczenie jakości wody w analizach HPLC i LC-MS

Riché E., Tarun M., Regnault C., Mabic S.

Laboratorium - Przegląd Ogólnopolski

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2016

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nr 7-8

48--50

8

HPLC, open column chromatography, and LC-ESI-MS separation patterns and a new method of estimation of a phytoconstituent from Heiba (Ficus pomifera Wall.)

Wangkheirakpam S. D., Laitonjam W. S.

Acta Chromatographica

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2016

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Vol. 28, no. 1

5--17

EN

The different separation patterns of petroleum ether extract of leaves of Heiba (Ficus pomifera Wall.) were studied with open column chromatography, highperformance liquid chromatography (HPLC), and liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS). A new method of locating and estimating newly discovered compounds by LC-ESI-MS was developed. Compound 1, a triterpenoid of mass 398, was identified by spectral analysis. It was located in the chromatogram by comparison of mass spectrum of the isolated compound to mass spectra of in mass spectral data of LC-ESI-MS. The concentration of the triterpenoid was found to be 8.64 ppm in 2000 ppm of the extract, assuming that all the components are eluted.

9

Profiles of products generated during betacyanins reduction by 2-methylpyridine borane

Szot D., Starzak K., Skopińska A., Wybraniec S.

Challenges of Modern Technology

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2015

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Vol. 6, no. 4

19--22

EN

Betanin and neobetanin (14,15-dehydrogenated betanin), natural betacyanin pigments were subjected to a gentle reduction by 2-methylpyridine borane. During each reduction reaction, the visible spectra were collected. The results were tentatively confirmed by LC-DAD-ESI-MS. In comparison to a previous study with sodium borohydride, various types of products were obtained. Depending on pH, one or two double bonds are reduced. Interestingly, a preliminary decarboxylation of the pigments is also noticed. Betacyanins are plant red-violet pigments applied as colorants in food and pharmaceutical industry which are proven to have an antioxidant activity. They are confirmed to be beneficial for human health as free radical scavengers. Therefore, betacyanins can prevent from many diseases which would be induced by an excessive accumulation of free radicals in the human body. There are more and more reports of their pro-health properties. However, the mechanism of betacyanins oxidation remains not completely elucidated. It is postulated that the rearrangement in the chromophoric system is a significant part of this mechanism. The products obtained as a result of reduction of betanin and neobetanin can be useful in oxidation investigations. Betacyanins with partially destroyed chromophoric system by reduction of the double bonds would by perfect models for further studies on their oxidation.

10

Chromatographic fractionation of betacyanins from flowers of Gomphrena globosa

Szot D., Starzak K., Skopińska A., Wybraniec S.

Challenges of Modern Technology

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2015

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Vol. 6, no. 2

19--23

EN

In this study, a chromatographic fractionation of betacyanin pigments from extract of purple Gomphrena globosa petals was performed by preparative high performance liquid chromatography (prep-HPLC). The particular betacyanins in each collected fractions were tentatively identified by chromatography with optical amd mass spetrometric detection (LC-DAD-ESI-MS). Betacyanins are natural pigments, which are confirmed to have an antioxidant activity. It was reported that betacyanins can prevent civilization diseases, because of an ability of free radicals scavenging. Betacyanins are present in tissue of plants from Amaranthaceae family, e.g. in petals of Gomphrena globosa. Preparative separation of these particular pigments is difficult, because they are structurally very similar to each other and tend to coelute. However, in this study, fractions, containing a dominant amount of the principal pigments of Gomphrena globosa inflorescences, were obtained successfully. In the first fractions, two isomeric pigments assigned to gomphrenin I and isogomphrenin I were detected. The fractions of significant amounts of gomphrenin III and isogomphrenin III were obtained separately with sufficient purity. The presence of other, minor gomphrenin-type betacyanins were also confirmed as: gomphrenin II, cis-isomer of gomphrenin II and sinapoyl-gomphrenin I as well as their 15S-diastereomers. Moreover, in other fractions, various unknown pigments were detected.

11

Development and validation of rapid LC-MS with electrospray ionization for the quantification of pramipexole in human plasma

Lavudu P., Rani A. P., Sekharan C. B.

International Letters of Chemistry, Physics and Astronomy

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2014

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Vol. 18

1--15

EN

A rapid, accurate and precise LC-MS method is described for the quantitative determination of pramipexole in human plasma matrix using ropinirole as internal standard. Pramipexole and ropinirole were extracted from plasma by liquid-liquid extraction technique. The method was validated over the concentration range of 100-2514 pg/mL. The method was found to have acceptable accuracy, precision, linearity and selectivity. The mean extraction recovery from spiked plasma samples was in the range of 79.415-87.00 %. The intra-day accuracy of the assay ranged from 98.924 to 112.236 % and intra-day precision ranged from 3.489 to 6.756 %. Inter-day accuracy and precision results for quality control samples ranged between 100.340 and 107.443% of nominal and precision is observed to be 3.970-5.714 %. The pramipexole was found to be stable after several stability studies. The proposed method yielded a quick, simple and reliable protocol for estimating pramipexole concentrations in human plasma.

12

Methods for the determination of hexabromocyclododecane in food

Kuc J., Grochowalski A.

Czasopismo Techniczne. Chemia

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2014

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R. 111, z. 1-Ch

45--55

EN

Methods of sample preparation with a particular emphasis on extraction and purification techniques are described. Gas and liquid chromatography techniques applied for the determination of hexabromocyclododecane are presented. Issues relating to the determination of this compound in food samples are discussed.

PL

Omówiono metody przygotowania próbek do analizy ze szczególnym uwzględnieniem technik ekstrakcji i oczyszczania próbek. Zaprezentowano techniki chromatografii gazowej i cieczowej stosowane do oznaczania heksabromocyklododekanu. Przedyskutowano problemy oznaczania tego związku w próbkach żywności.

13

Stress degradation studies on zolpidem tartrate using LC-DAD and LC-MS methods

Malesevic M., Zivanovic L., Protic A., Radisic M., Lausevic M., Jovic Z., Zecevic M.

Acta Chromatographica

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2014

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Vol. 26, no. 1

81--96

EN

The present study was designed to characterize the possible degradation products of zolpidem tartrate under various stress conditions according to International Conference on Harmonization (ICH) guidelines Q1A(R2). After exposure to light, heat, hydrolysis, and oxidation, the drug significantly degraded under photolytic and acid/base hydrolytic conditions. Degradation resulted in the formation of four key degradants. Degradation products were resolved from each other and the drug by employing an isocratic elution method on Luna C18 column with mobile phase consisting of methanol-10 mM ammonium acetate (68.4:31.6, v/v), wherein pH was adjusted to 5.4 with glacial acetic acid. To characterize the degradation products, a method was extended to LC-MS and a mass fragmentation pattern was established using single quadrupole. The degradants were identified as zolpacid, oxozolpidem, zolpaldehyde, and zolpyridine. Finally, the most possible degradation mechanism of zolpidem tartrate in different environments was proposed.

14

Level of hexabromocyclododecane isomers in the tissue of selected commonly consumed fish in Central European countries

Kuc J., Grochowalski A., Mach S., Placha D.

Acta Chromatographica

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2014

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Vol. 26, no. 4

575--585

EN

This paper is focused on the determination of three hexabromocyclododecane isomers, α, β, and γ, in the tissue of the most commonly consumed marine and farmed fish in Central Europe. The analytical procedure contains multiple steps: extraction, dialysis using semipermeable membranes, and a clean-up step using a silica gel column. Hexabromocyclododecane (HBCD) isomers were determined by sensitive isotope dilution liquid chromatography-tandem mass spectrometry (LC-MS/MS) method which is characterized by a low limit of detection (1 pg g -1 fresh weight). The recovery values obtained for individual isomers were in the range of 89–124%. The γ-HBCD isomer was detected in all samples. This isomer also had the largest percentage in comparison with the other isomers, except in salmon, in which the α-HBCD isomer was more abundant. The highest level of total HBCD was measured in mackerel (650 ± 195 pg g -1 fresh weight). Cluster analysis allowed the differentiation of groups of objects and the display of objects based on the degree of integration within the same group. Spearman’s rank correlation indicated no statistically significant difference between the levels of HBCD and the fat content in the fish samples.

15

Development and validation of a stability-indicating RP-LC method for the estimation of process-related impurities and degradation products of oxcarbazepine in pharmaceutical formulation

Reddy P. S., Babu K. S., Kumar N.

Acta Chromatographica

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2014

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Vol. 26, no. 2

267--282

EN

A stability-indicating gradient reverse-phase liquid chromatographic method was developed for the quantitative determination of process-related impurities and forced degradation products of oxcarbazepine in pharmaceutical formulation. The method was developed by using Inertsil cyano (250 × 4.6 mm) 5 μm column with mobile phase containing a gradient mixture of solvent A (0.01 M sodium dihydrogen phosphate, pH adjusted to 2.7 with orthophosphoric acid and acetonitrile in the ratio of 80:20 v/v) and B (50:40:10 v/v/v mixture of acetonitrile, water, and methanol). The flow rate of mobile phase was 1.0 mL min−1. Column temperature was maintained at 25°C and detection wavelength at 220 nm. Developed reverse-phase high-performance liquid chromatography (RP-HPLC) method can adequately separate and quantitate five impurities of oxcarbazepine, namely imp-A, imp-B, imp-C, imp-D, and imp-E. Oxcarbazepine was subjected to the stress conditions of oxidative, acid, base, hydrolytic, thermal, and photolytic degradation. Oxcarbazepine was found to degrade significantly in acid, base, and oxidative stress conditions. The degradation products were well resolved from oxcarbazepine and its impurities. The developed method was validated as per International Conference on Harmonization (ICH) guidelines with respect to specificity, linearity, limit of detection and quantification, accuracy, precision, and robustness.

16

Chiral conversion and condensation of l-hydroxyproline in an abiotic liquid system

Maciejowska A., Godziek A., Sajewicz M., Kowalska T.

Acta Chromatographica

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2014

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Vol. 26, no. 2

355--369

EN

This study is devoted to the thin-layer chromatographic demonstration of spontaneous chiral conversion of l-hydroxyproline (l-Hyp) to d-hydroxyproline (d-Hyp), and to its spontaneous peptidization, when dissolved in 70% aqueous methanol and stored at room temperature in a stoppered glass vessel. The adopted enantioseparation conditions were the same ones, as employed earlier for a successful enantioseparation of l- and d-proline. To this effect, we used microcrystalline cellulose as stationary phase and a quaternary mixture composed of 2-butanol:pyridine:glacial acetic acid:water (30:20:4:24, v/v) as mobile phase. Structural difference between proline and hydroxyproline consists in the presence of one hydroxyl group per molecule of the latter amino acid, which makes the respective enantioseparation a more difficult task. Consequently, the obtained separation effect was not a complete (i.e., a baseline) resolution of the two Hyp antimers yet a sufficient enough proof of the appearance of d-Hyp, apparently due to spontaneous chiral conversion taking place in the course of the l-Hyp solution storage and ageing period. The condensation products were discovered both in the fresh and the aged l-Hyp solution, yet in the aged sample, the condensation product yields were considerably higher than in the freshly prepared one (as convincingly demonstrated by mass spectrometry). Demonstration of the condensation products was performed with the aid of thin-layer chromatography (TLC), liquid chromatography-mass spectrometry (LC-MS), and thin-layer chromatography-mass spectrometry (TLC-MS).

17

A validated stability indicating RP-HPLC method for valganciclovir, identification and characterization of forced degradation products of valganciclovir using LC-MS/MS

Sawant S., Barge V.

Acta Chromatographica

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2014

|

Vol. 26, no. 1

29--42

EN

The objective of the present study was to report the stability of novel antiviral drug, valganciclovir based on the information obtained from forced degradation studies. Valganciclovir was subjected to forced hydrolytic (acidic, alkaline and neutral), oxidative, photolytic and thermal stress in accordance with the ICH guideline Q1A (R2). The drug showed labiality under only acidic and photoacidic conditions while it was stable to other stress conditions. Resolution of the drug and degradation products was achieved on a Hypersil Gold C-18 column (4.6 × 250 mm, 5 μm) utilizing acetonitrile (A) and potassium dihydrogen ortho phosphate buffer (pH 5.0; 0.01M) in the ratio of 5:95 (v/v) at a flow rate of 0.6 ml/min and at the detection wavelength 252 nm. The major acidic stress degradation product was characterized by LC-MS/MS and its fragmentation pathway was proposed. Validation of the LC-DAD method was carried out in accordance with ICH guideline. The method met all required criteria and was applied for analysis of commercially available tablets.

18

Spektrometria mas - ocena zafałszowań żywności

Targoński Z., Stój A.

Laboratorium - Przegląd Ogólnopolski

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2013

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nr 5-6

47--49

PL

Proceder fałszowania dotyczy większości produktów żywnościowych: napojów bezalkoholowych i alkoholowych, olejów, miodów, czekolady, mleka i produktów mlecznych, mięsa i produktów mięsnych, jaj oraz owoców morza. Do wykrywania zafałszowań żywności wykorzystuje się metody fizykochemiczne, biologii molekularnej, immunologiczne i enzymatyczne. Wśród metod fizykochemicznych istotną rolę odgrywa spektrometria mas. W pracy przedstawiono zastosowanie spektrometrii mas w połączeniu z chromatografią gazową (GC-MS) i cieczową (LC-MS) oraz spektrometrii mas (MS) do wykrywania zafałszowań żywności.

EN

The counterfeiting affects most food products: soft drinks and alcohol, oil, honey, chocolate, milk and milk products, meat and meat products, eggs and seafood. For the detection of food adulteration physico-chemical, molecular biology, immunological and enzymatic methods are used. Among the physicochemical methods mass spectrometry plays an important role. The paper presents the use of mass spectrometry in combination with gas chromatography (GC-MS) and liquid chromatography (LC-MS) and mass spectrometry (MS) to detect adulteration of food.

19

Addition of bisulfite ions to methyl vinyl ketone and methacrolein relevant to atmospheric processes

Szmigielski R., Rudziński K. J.

Ecological Chemistry and Engineering. A

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2013

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Vol. 20, nr 9

935--949

PL

Metakroleina oraz keton metylowo-winylowy są bardzo reaktywnymi zawiązkami karbonylowymi, które odgrywają istotną rolę w procesach atmosferycznych, w tym – w tworzeniu pyłów zwieszonych w powietrzu. Obydwa związki są produktami utleniania izoprenu – węglowodoru emitowanego do atmosfery w ogromnych ilościach. W pracy przedyskutowano mechanizmy chemiczne zaniku metakroleiny oraz ketonu metylowo-winylowego w wyniku addycji anionu wodorosiarczanowego w rozcieńczonych roztworach wodnych, odzwierciedlające procesy zachodzące w kroplach wód atmosferycznych w rejonach o znaczącym stężeniu ditlenku siarki. W pracy pokazano, że reakcje addycji anionu wodorosiarczynowego do badanych związków karbonylowych prowadzą do tworzenia pierwotnych i wtórnych hydroksysulfonianów, które mogą uczestniczyć w tworzeniu aerozoli atmosferycznych. Wyznaczono stałe szybkości wszystkich reakcji w mechanizmie addycji. Pierwotna addycja anionów wodorosiarczynowych do metakroleiny okazała się znacznie szybsza niż do ketonu metylowo-winylowego (stałe szybkości kMAC1f = 8 i kMVK1f = 0.18 mol–1 dm3 s–1 w temperaturach pokojowych). Stała szybkości addycji do cząsteczki metakroleiny była dziesięciokrotnie większa od stałej opublikowanej w literaturze. Analiza kinetyczna i badania produktów reakcji za pomocą spektrometrii mas wykazały, że w przypadku każdego z badanych związków karbonylowych dominującym produktem reakcji był C4 alfa-hydroksysulfonian (addukt pierwotny), natomiast C4 hydroksydwusulfonian (addukt wtórny, diaddukt) powstawał w ilościach śladowych. Pierwotna addycja anionów wodorosiarczynowych do metakroleiny i ketonu metylowo-winylowego może mieć znaczenie w konwersji reaktywnych związków karbonylowych w atmosferze i powinna być uwzględniana w badaniach dotyczących rejonów o znaczącej obecności ditlenku siarki, gwarantującej wysokie stężenia anionów wodorosiarczynowych w wodach atmosferycznych.

EN

Methacrolein and methyl vinyl ketone are highly reactive carbonyls that play a pivotal role in the formation of secondary organic aerosols in the Earth’s atmosphere. Both carbonyls are the major products of isoprene oxidation. We show that among the atmospheric sinks of methacrolein and methyl vinyl ketone, the aqueous-phase addition of bisulfite anions to their molecules can be relevant under polluted conditions with the increased presence of sulfur dioxide. We demonstrate that aqueous-phase reactions of methyl vinyl ketone and methacrolein with bisulfite anions lead to the formation of primary and secondary organic hydroxysulfonates which currently are not included in the atmospheric chemistry modelling, but can be relevant in mechanisms explaining the formation and growth of the secondary organic aerosols from atmospheric carbonyls. The rate constants for all aqueous-phase reactions involved were determined. The primary addition of bisulfite anions to methacrolein was found significantly faster than that to methyl vinyl ketone, with rate constants kMAC1f = 8 and kMVK1f = 0.18 mol–1 dm3 s–1 at room temperatures, respectively. The rate constant for the bisulfite addition to methacrolein was ten times faster than reported in the literature. The kinetic and mass spectrometric analyses revealed that in both cases, the dominating product was the C4 alpha-hydroxysulfonate (a primary adduct), while the C4 alpha-hydroxy disulfonate (a secondary adduct or diadduct) was produced only in trace quantities. The primary addition of bisufite anions to methacrolein and methyl vinyl ketone should be considered in atmospheric studies relevant to areas with enhanced presence of sulfur dioxide providing sufficiently high concentrations of bisulfite ions in atmospheric waters.

20

Unsupervised adaptive filter for baseline thresholding and elimination in liquid chromatography-mass spectrometry via approximation of the standard deviation of baseline distribution in retention time domain

Urban J., Vaněk J., Štys D.

Acta Chromatographica

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2013

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Vol. 25, no. 2

257--273

EN

The omitting presence of a baseline (background, systemic noise, mobile phase) in liquid chromatography-mass spectrometry (LC-MS) measurements impedes objective analysis. Therefore, there is a demand to remove its contribution from the signal response. Elimination of baseline contribution is justified by increasing the data mining output, both qualitatively and quantitatively. Behavior of the baseline content is not perfectly constant on the time axis, and it is often necessary to experiment with gradient changes. However, the behavior could be parametrized using a technique derived from statistical moments. In this article, we propose adaptive thresholding as an unsupervised method for baseline removal from the measurement data. Results of a real analyte measurement are discussed to illustrate its efficiency.