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Derivatization in Analytical Chemistry-II

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A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Analytical Chemistry".

Deadline for manuscript submissions: closed (28 February 2023) | Viewed by 20339

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Dr. Paraskevas D. Tzanavaras

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Laboratory of Analytical Chemistry, School of Chemistry, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
Interests: automation; sequential injection analysis; separation techniques (HPLC, CE); post-column derivatization; microextraction
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Dr. Apostolia Tsiasioti

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Laboratory of Analytical Chemistry, Department of Chemistry, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece
Interests: post-column derivatization; HPLC; automation

Special Issue Information

Dear Colleagues,

Following the success of our first Special Issue on Analytical Derivatization in the journal Molecules (https://www.mdpi.com/journal/molecules/special_issues/derivatization_analytical_chemistry), we are pleased to announce the launch of a follow-up SI under the title “Derivatization in Analytical Chemistry—II”.

Derivatization is one of the most widely used sample pretreatment techniques in analytical chemistry and chemical analysis. Reagent-based or reagent-less schemes offer improved detectability of target compounds, modification of the chromatographic properties, and/or stabilization of sensitive compounds until analysis. Either coupled to separation techniques or as a “standalone” analytical procedure, derivatization offers endless possibilities in all aspects of analytical applications.

The present Special Issue aims to cover the latest research trends and applications of analytical derivatization. Researchers working on all aspects of basic research and applications of derivatization in food, environmental, and biomedical sciences are cordially invited to contribute a research or review article in this Special Issue.

Dr. Paraskevas D. Tzanavaras
Dr. Apostolia Tsiasioti
Guest Editors

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Keywords

analytical derivatization
automation
pre-column derivatization
post-column derivatization
in-column derivatization
photochemical derivatization
flow-based derivatization
derivatization coupled to mass spectrometry
in-capillary derivatization
high-throughput derivatization (plate format)

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Published Papers (9 papers)

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Research

20 pages, 4537 KiB

Open AccessArticle

Positive Effect of Acetylation on Proteomic Analysis Based on Liquid Chromatography with Atmospheric Pressure Chemical Ionization and Photoionization Mass Spectrometry

by Simona Sedláčková, Martin Hubálek, Vladimír Vrkoslav, Miroslava Blechová, Petr Kozlík and Josef Cvačka

Molecules 2023, 28(9), 3711; https://doi.org/10.3390/molecules28093711 - 25 Apr 2023

Cited by 3 | Viewed by 2050

Abstract

A typical bottom-up proteomic workflow comprises sample digestion with trypsin, separation of the hydrolysate using reversed-phase HPLC, and detection of peptides via electrospray ionization (ESI) tandem mass spectrometry. Despite the advantages and wide usage of protein identification and quantification, the procedure has limitations. Some domains or parts of the proteins may remain inadequately described due to inefficient detection of certain peptides. This study presents an alternative approach based on sample acetylation and mass spectrometry with atmospheric pressure chemical ionization (APCI) and atmospheric pressure photoionization (APPI). These ionizations allowed for improved detection of acetylated peptides obtained via chymotrypsin or glutamyl peptidase I (Glu-C) digestion. APCI and APPI spectra of acetylated peptides often provided sequence information already at the full scan level, while fragmentation spectra of protonated molecules and sodium adducts were easy to interpret. As demonstrated for bovine serum albumin, acetylation improved proteomic analysis. Compared to ESI, gas-phase ionizations APCI and APPI made it possible to detect more peptides and provide better sequence coverages in most cases. Importantly, APCI and APPI detected many peptides which passed unnoticed in the ESI source. Therefore, analytical methods based on chymotrypsin or Glu-C digestion, acetylation, and APPI or APCI provide data complementary to classical bottom-up proteomics. Full article

(This article belongs to the Special Issue Derivatization in Analytical Chemistry-II)

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8 pages, 2289 KiB

Open AccessCommunication

Analyzing Citramalic Acid Enantiomers in Apples and Commercial Fruit Juice by Liquid Chromatography–Tandem Mass Spectrometry with Pre-Column Derivatization

by Maho Umino, Mayu Onozato, Tatsuya Sakamoto, Mikoto Koishi and Takeshi Fukushima

Molecules 2023, 28(4), 1556; https://doi.org/10.3390/molecules28041556 - 6 Feb 2023

Cited by 3 | Viewed by 1903

Abstract

Optically active citramalic acid (CMA) is naturally present as an acidic taste component in fruits, such as apples. The absolute configuration of CMA in such fruits was investigated by high-performance liquid chromatography–tandem mass spectrometry (LC–MS/MS) following pre-column derivatization with a chiral reagent, benzyl 5-(2-aminoethyl)-3-methyl-4-oxoimidazolidine-1-carboxylate. The developed LC–MS/MS method successfully separated the enantiomers of CMA using an octadecylsilica column with a resolution and separation factor of 2.19 and 1.09, respectively. Consequently, the R-form of CMA was detected in the peel and fruit of three kinds of apple at concentrations in the 1.24–37.8 and 0.138–1.033 mg/wet 100 g ranges, respectively. In addition, R- CMA was present in commercial apple juice, whereas no quantity was detected in commercial blueberry, perilla, or Japanese apricot juice. Full article

(This article belongs to the Special Issue Derivatization in Analytical Chemistry-II)

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13 pages, 1323 KiB

Open AccessArticle

Pentafluoropropionic Anhydride Derivatization and GC-MS Analysis of Histamine, Agmatine, Putrescine, and Spermidine: Effects of Solvents and Starting Column Temperature

by Dimitrios Tsikas, Bibiana Beckmann, Svetlana Baskal and Gorig Brunner

Molecules 2023, 28(3), 939; https://doi.org/10.3390/molecules28030939 - 17 Jan 2023

Cited by 3 | Viewed by 2343

Abstract

Gas chromatography–mass spectrometry (GC-MS) is useful for the quantitative determination of the polyamines spermidine (SPD) and putrescine (PUT) and of the biogenic amine agmatine (AGM) in biological samples after derivatization. This GC-MS method involves a two-step extraction with n-butanol and hydrochloric acid, derivatization with pentafluoropropionic anhydride (PFPA) in ethyl acetate, and extraction of the pentafluoropropionic (PFP) derivatives by toluene of SPD, PUT, and AGM. We wanted to extend this GC-MS method for the biogenic amine histamine (HA), but we faced serious problems that did not allow reliable quantitative analysis of HA. In the present work, we addressed this issue and investigated the derivatization of HA and the effects of toluene and ethyl acetate, two commonly used water-insoluble organic solvents in GC-MS, and oven temperature program. Derivatization of unlabelled HA (d₀-HA) and deuterium-labelled HA (d₄-HA) with PFPA in ethyl acetate (PFPA-EA, 1:4, v/v; 30 min, 65 °C) resulted in the formation of d₀-HA-(PFP)₂ and d₄-HA-(PFP)₂ derivatives. d₄-HA and ¹³C₄-SPD were used as internal standards for the amines after standardization. Considerable quantitative effects of toluene and ethyl acetate were observed. The starting GC column temperature was also found to influence considerably the GC-MS analysis of HA. Our study shows the simultaneous quantitative analysis of HA as HA-(PFP)₂, AGM as AGM-(PFP)₃, PUT as PUT-(PFP)₂, and SPD as SPD-(PFP)₃ derivatives requires the use of ethyl acetate for their extraction and injection into the GC-MS apparatus and a starting GC column temperature of 40 °C instead of 70 °C. The PFP derivatives of HA, AGM, PUT, and SPD were found to be stable in ethyl acetate for several hours at room temperature. Analytically satisfactory linearity, precision, and accuracy were observed for HA, AGM, PUT, and SPD in biologically relevant ranges (0 to 700 pmol). The limits of detection of AGM, PUT, and SPD were about two times lower in ethyl acetate compared to toluene (range, 1–22 fmol). The limits of detection were 1670 fmol for d₀-HA and 557 fmol for d₄-HA. Despite the improvements achieved in the study for HA, its analysis by GC-MS as a PFP derivative is challenging and less efficient than that of PUT, AGM, and SPD. Full article

(This article belongs to the Special Issue Derivatization in Analytical Chemistry-II)

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8 pages, 1254 KiB

Open AccessCommunication

Determination of Free Histidine in Complex Hair Care Products with Minimum Sample Preparation Using Cation-Exchange Chromatography and Post Column Derivatization

by Apostolia Tsiasioti, Constantinos K. Zacharis and Paraskevas D. Tzanavaras

Molecules 2023, 28(2), 888; https://doi.org/10.3390/molecules28020888 - 16 Jan 2023

Cited by 3 | Viewed by 1903

Abstract

In this communication, we describe the first analytical method for the determination of free histidine in hair care products (shampoos and conditioners). Cation-exchange chromatography combined with postcolumn derivatization and fluorimetric detection enabled the accurate (recovery: 83.5–114.8%) and precise (2.4–5.6% RSD) determination of free histidine without matrix interferences at concentration levels down to 1.5 mg kg⁻¹. Real commercially available samples were found to contain the amino acid at levels ranging between 70 and 535 mg kg⁻¹. Full article

(This article belongs to the Special Issue Derivatization in Analytical Chemistry-II)

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11 pages, 1905 KiB

Open AccessArticle

The Use of Polydialkylsiloxanes/Triflic Acid as Derivatization Agents in the Analysis of Sulfur-Containing Aromatics by “Soft”-Ionization Mass Spectrometry

by Zhanna Starkova, Valentina Ilyushenkova, Nikolay Polovkov, Daria Voskressenskaya, Ilya Pikovskoi, Mikhail Tebenikhin, Ella Vtorushina, Anastasiia Kanateva, Roman Borisov and Vladimir Zaikin

Molecules 2022, 27(23), 8600; https://doi.org/10.3390/molecules27238600 - 6 Dec 2022

Cited by 1 | Viewed by 1587

Abstract

Polycyclic aromatic sulfur-containing compounds are widely distributed in oil, especially in its low-volatile and heavy fractions (resins, asphaltenes), and this dictates the need for their determination when reliable methods for sulfur removing, cleaning and processing oil are developed. In these cases, “soft” ionization mass spectrometry methods, based on electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI), are particularly effective. However, aromatic sulfur-containing compounds have low polarity and cannot be readily ionized by these methods. To overcome the problem, their preliminary conversion into sulfonium salts by the action of alkyl iodides and a silver-containing agent is widely used. In the process of developing more economical derivatization methods, we found a rather unexpected possibility of implementing S-alkylation of organic sulfides with commercial polydialkylsiloxanes (alkyl = CH₃ or C₂H₅) in the presence of triflic acid (CF₃SO₃H) as a superacid co-alkylating agent. For homologous dibenzothiophenes as a typical model representative of petroleum sulfur-containing aromatic compounds, ESI and MALDI mass spectra exhibited the signals of corresponding S-alkylsulfonium salts with a high signal-to-noise ratio. A rational mechanism for the described chemical transformation is proposed, including the indispensable activation by triflic acid and the cleavage of the Si-C bond. Specific collision-induced dissociation of corresponding S-alkylated sulfonium cations is considered. The applicability of the derivatization approach to the analysis of petroleum products by high-resolution mass spectrometry is demonstrated. Full article

(This article belongs to the Special Issue Derivatization in Analytical Chemistry-II)

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16 pages, 13727 KiB

Open AccessArticle

GC-MS Studies on the Conversion and Derivatization of γ-Glutamyl Peptides to Pyroglutamate (5-Oxo-Proline) Methyl Ester Pentafluoropropione Amide Derivatives

by Alexander Bollenbach and Dimitrios Tsikas

Molecules 2022, 27(18), 6020; https://doi.org/10.3390/molecules27186020 - 15 Sep 2022

Cited by 3 | Viewed by 2170

Abstract

Glutathione (γ-L-glutamyl-L-cysteinyl-glycine, γ-Glu-Cys-Gly) is the most abundant intra-cellular dicarboxylic tripeptide with multiple physiological roles. In biological samples, glutathione exists in its reduced form GSH and in two stable oxidized forms, i.e., in its symmetric disulfide form GSSG and as S-glutathionyl residue in proteins. S-Glutathionylation is a post-translational modification, which is involved in several pathophysiological processes, including oxidative stress. The GSH-to-GSSG molar ratio is widely used as a measure of oxidative stress. γ-Glutamyl is the most characteristic structural moiety of GSH. We performed gas chromatography-mass spectrometry (GC-MS) studies for the development of a highly specific qualitative and quantitative method for γ-glutamyl peptides. We discovered intra-molecular conversion of GSH, GSSG, γ-Glu-Cys and of ophthalmic acid (OPH; γ-glutamyl-α-amino-n-butyryl-glycine) to pyroglutamate (pGlu; 5-oxo-proline, also known as pidolic acid) during their derivatization with 2 M HCl/CH₃OH (60 min, 80 °C). For GC-MS analysis, the methyl esters (Me) were further derivatized with pentafluoropropionic (PFP) anhydride in ethyl acetate (1:4, v/v; 30 min, 65 °C) to their PFP derivatives. At longer reaction times, pGlu is hydrolyzed to Glu. Internal standards were prepared by derivatizing GSH, GSSG, γ-Glu-Cys and OPH in 2 M HCl/CD₃OD. Quantification of the Me-PFP derivative of pGlu was performed in the electron-capture negative-ion chemical ionization (ECNICI) mode by selected-ion monitoring (SIM) of the mass-to-charge (m/z) ions 269 for unlabeled pGlu (d₀Me-PFP-pGlu) and m/z 272 for the in situ prepared deuterium-labeled pGlu (d₃Me-PFP-pGlu). Although not inherent to the analysis of small peptides, the present GC-MS method is useful to study several biochemical aspects of GSH. Using pentafluorobenzyl bromide (PFB-Br) as the derivatization reagent, we found that synthetic pGlu is converted in aqueous acetone (60 min, 50 °C) into its pentafluorobenzyl (PFB) ester (PFB-pGlu). This derivatization procedure is useful for the GC-MS analysis of free pGlu in the ECNICI mode. Quantitative analysis of PFB-pGlu by GC-MS requires the use of stable-isotope labeled analogs of pGlu as an internal standard. Full article

(This article belongs to the Special Issue Derivatization in Analytical Chemistry-II)

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10 pages, 1064 KiB

Open AccessArticle

Unusual Derivatization of Methylmalonic Acid with Pentafluorobenzyl Bromide to a Tripentafluorobenzyl Derivative and Its Stable-Isotope Dilution GC-MS Measurement in Human Urine

by Alexander Bollenbach, Svetlana Baskal, Catharina Mels, Ruan Kruger and Dimitrios Tsikas

Molecules 2022, 27(16), 5202; https://doi.org/10.3390/molecules27165202 - 15 Aug 2022

Cited by 3 | Viewed by 2131

Abstract

Methylmalonic acid (MMA) is a very short dicarboxylic acid (methylpropanedioic acid; CH₃CH(COOH)₂; pK_a1, 3.07; pK_a2, 5.76) associated with vitamin B₁₂ deficiency and many other patho-physiological conditions. In this work, we investigated several carboxylic groups-specific derivatization reactions and tested their utility for the quantitative analysis of MMA in human urine and plasma by gas chromatography-mass spectrometry (GC-MS). The most useful derivatization procedure was the reaction of unlabeled MMA (d₀-MMA) and trideutero-methyl malonic acid (d₃-MMA) with 2,3,4,5,6-pentafluorobenzyl bromide (PFB-Br) in acetone. By heating at 80 °C for 60 min, we observed the formation of the dipentafluorobenzyl (PFB) ester of MMA (CH₃CH(COOPFB)₂). In the presence of N,N-diisopropylamine, heating at 80 °C for 60 min resulted in the formation of a tripentafluorobenzyl derivative of MMA, i.e., CH₃CPFB(COOPFB)₂). The retention time was 5.6 min for CH₃CH(COOPFB)₂ and 7.3 min for CH₃CPFB(COOPFB)₂). The most intense ions in the negative-ion chemical ionization (NICI) GC-MS spectra of CH₃CH(COOPFB)₂ were mass-to-charge (m/z) 233 for d₀-MMA and m/z 236 for d₃-MMA. The most intense ions in the NICI GC-MS spectra of CH₃CPFB(COOPFB)₂ were mass-to-charge (m/z) 349 for d₀-MMA and m/z 352 for d₃-MMA. These results indicate that the H at C atom at position 2 is C-H acidic and is alkylated by PFB-Br only in the presence of the base N,N-diisopropylamine. Method validation and quantitative analyses in human urine and plasma were performed by selected ion monitoring (SIM) of m/z 349 for d₀-MMA and m/z 352 for the internal standard d₃-MMA in the NICI mode. We used the method to measure the urinary excretion rates of MMA in healthy black (n = 39) and white (n = 41) boys of the Arterial Stiffness in Offspring Study (ASOS). The creatinine-corrected excretion rates of MMA were 1.50 [0.85–2.52] µmol/mmol in the black boys and 1.34 [1.02–2.18] µmol/mmol in the white boys (P = 0.85; Mann–Whitney). The derivatization procedure is highly specific and sensitive for MMA and allows its accurate and precise measurement in 10-µl of human urine by GC-MS. Full article

(This article belongs to the Special Issue Derivatization in Analytical Chemistry-II)

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15 pages, 1417 KiB

Open AccessArticle

Stable-Isotope Dilution GC–MS Measurement of Metformin in Human Serum and Urine after Derivatization with Pentafluoropropionic Anhydride and Its Application in Becker Muscular Dystrophy Patients Administered with Metformin, l-Citrulline, or Their Combination

by Svetlana Baskal, Alexander Bollenbach, Bettina Henzi, Patricia Hafner, Dirk Fischer and Dimitrios Tsikas

Molecules 2022, 27(12), 3850; https://doi.org/10.3390/molecules27123850 - 15 Jun 2022

Cited by 9 | Viewed by 2430

Abstract

Metformin (N,N-dimethylguanylguanidine) is one of the most prescribed drugs with pleiotropic, exerted in part by not fully elucidated mechanisms of action. We developed and validated a gas chromatography–mass spectrometry (GC–MS) method for the quantitative analysis of metformin (metformin-d₀) in 10-µL aliquots of human serum and urine using N,N-[dimethylo-²H₆]guanylguanidine (metformin-d₆) as the internal standard. The method involves evaporation of the samples to dryness, derivatization with pentafluoropropionic (PFP) anhydride in ethyl acetate (30 min, 65 °C), and extraction into toluene. The negative-ion chemical ionization GC–MS spectra of the PFP derivatives contain a single intense ion with mass-to-charge (m/z) ratios of m/z 383 for metformin-d₀ and m/z 389 for metformin-d₆. Our results suggest that all amine/imine groups of metformin-d₀ and metformin-d₆ are converted to their N,N,N-tripentafluoropropionyl derivatives, which cyclize to form a symmetric triazine derivative, of which the non-ring amine group is amidated. Quantification was performed by selected-ion monitoring (SIM) of m/z 383 and m/z 389. Upon validation, the method was applied to determine serum and urine metformin concentrations in 19 patients with Becker muscular dystrophy (BMD). Serum and urine samples were collected at baseline (Visit I), after six weeks of supplementation (Visit II) with metformin (3 × 500 mg/d; metformin group; n = 10) or l-citrulline (3 × 1500 mg/d; citrulline group; n = 9) followed by a six-week supplementation with 3 × 500 mg/d of metformin plus 3 × 1500 mg/d l-citrulline. At Visit I, the metformin concentration in the serum and urine was very low in both groups. The metformin concentrations in the serum and urine of the patients who first took metformin (MET group) were higher at Visit II and Visit III. The metformin concentration in the serum and urine samples of the patients who first took l-citrulline (CITR group) were higher at Visit III. The serum and urine concentrations of metformin were insignificantly lower in the CITR group at Visit III. The mean fractional excretion (FE) rate of metformin was 307% (Visit II) and 322% (Visit III) in the MET group, and 290% in the CITR group (Visit III). This observation suggests the accumulation of metformin in the kidney and its secretion in the urine. The GC–MS is suitable to measure reliably circulating and excretory metformin in clinical settings. Full article

(This article belongs to the Special Issue Derivatization in Analytical Chemistry-II)

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14 pages, 2914 KiB

Open AccessArticle

HPLC Determination of Colistin in Human Urine Using Alkaline Mobile Phase Combined with Post-Column Derivatization: Validation Using Accuracy Profiles

by Kalliopi Papavasileiou, Apostolia Tsiasioti, Paraskevas D. Tzanavaras and Constantinos K. Zacharis

Molecules 2022, 27(11), 3489; https://doi.org/10.3390/molecules27113489 - 28 May 2022

Cited by 7 | Viewed by 2821

Abstract

In this study, the development, validation, and application of a new liquid chromatography post-column derivatization method for the determination of Colistin in human urine samples is demonstrated. Separation of Colistin was performed using a core–shell C₁₈ analytical column in an alkaline medium in order (i) to be compatible with the o-phthalaldehyde-based post-column derivatization reaction and (ii) to obtain better retention of the analyte. The Colistin derivative was detected spectrofluorometrically (λ_ext/λ_em = 340/460 nm) after post-column derivatization with o-phthalaldehyde and N-acetyl cysteine. The post-column derivatization parameters were optimized using the Box–Behnken experimental design, and the method was validated using the total error concept. The β-expectation tolerance intervals did not exceed the acceptance criteria of ±15%, meaning that 95% of future results would be included in the defined bias limits. The limit of detection of the method was adequate corresponding to 100 nmol·L⁻¹. The mean analytical bias (expressed as relative error) in the spiking levels was suitable, being in the range of −2.8 to +2.5% for both compounds with the percentage relative standard deviation lower than 3.4% in all cases. The proposed analytical method was satisfactorily applied to the analysis of the drug in human urine samples. Full article

(This article belongs to the Special Issue Derivatization in Analytical Chemistry-II)

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