Fluorescence Derivatization Reagent Research Articles

Analysis of Urinary Amino Acids by High-Performance Liquid Chromatography with Fluorescence Detection Using 2,3-Naphthalenedicarboxaldehyde as Fluorescence Derivatization Reagent

Amino acids are involved in various chemical reactions in vivo, and changes in several amino acids in urine are related to certain disease states. Therefore, developing an efficient method to analyze the amino acids in urine is useful in the timely diagnosis of diseases. In this study, we developed a high-performance liquid chromatography (HPLC) fluorescence method for the quantitative analysis of urinary amino acids using the fluorescence derivatization reagent 2,3-naphthalenedicarboxaldehyde (NDA). NDA was selected because it does not require heating for the reaction and can react within a short time, rendering its use in clinical settings feasible. The reaction temperature, reaction time, and other derivatization conditions were optimized, and the reaction was found to be completed in 5 min at 25 °C. The separation of NDA–amino acids was investigated on an octadecylsilyl (ODS) column under gradient conditions. The mobile phase was a mixture of water–acetonitrile–trifluoroacetic acid. Eighteen NDA–amino acids (histidine (His), arginine (Arg), asparagine (Asn), glutamine (Gln), citrulline (Cit), serine (Ser), aspartic acid (Asp), threonine (Thr), glutamic acid (Glu), glycine (Gly), tyrosine (Tyr), alanine (Ala), tryptophan (Trp), valine (Val), phenylalanine (Phe), isoleucine (Ile), leucine (Leu), and 5-aminovaleric acid (internal standard)) were separated within 100 min under optimal conditions. The calibration curves showed good linearity in the range of 0.25–25 pmol per injection with correlation coefficients of >0.998. The limits of quantification for NDA–amino acids were 16.7–74.7 fmol. The developed analytical method was applied to a human urine sample and 16 amino acids (His, Arg, Asn, Gln, Cit, Ser, Thr, Glu, Gly, Tyr, Ala, Trp, Val, Phe, Ile, and Leu) were quantified. The urinary amino acid concentrations were 5–960 μM. Urinary amino acid analysis using this method is expected to be clinically applicable as a novel biomarker for diseases affecting the bladder, urinary tract, and kidneys.

Determination of Picolinic Acid by HPLC Coupled With Postcolumn Photo Irradiation Using Zinc Acetate as a Fluorescent Derivatization Reagent.

For the fluorometric determination of picolinic acid in human serum, HPLC-postcolumn UV irradiation using zinc acetate has been developed. Picolinic acid in serum sample was separated on a Capcell Pak C18. The mobile phase consisted of 0.1 mol/L sodium phosphate solution (adjusted to pH 3.0) containing 3.0 mmol/L zinc acetate and 3.5 mmol/L trimethylamine, and delivered at a flow rate of 0.8 mL/minutes. In order to stabilize the retention time (6.5 minutes), a back pressure tube (0.4 m × 0.13 mm i.d.) was attached after the photoreaction tube. Column effluent was irradiated with ultraviolet light to produce fluorescence, excitation wavelength of 336 nm and emission wavelength of 448 nm. The calibration graph for picolinic acid showed linearity when the amount was in the range of 0.89 to 455 pmol, and the detection limit (S/N = 3) was determined to be 0.30 pmol. The pretreatment of serum sample consisted of deproteinized by perchloric acid, potassium hydroxide, and mobile phase. The mean recovery of picolinic acid from serum was 99.0%. Using this procedure, the concentration of picolinic acid in serum of a healthy subject was determined.

Analysis of Methamphetamine in Urine by HPLC with Solid-Phase Dispersive Extraction and Solid-Phase Fluorescence Derivatization.

We have developed a fluorescence detection-liquid chromatography (HPLC-FL) method that involves sample pretreatment by solid-phase dispersive extraction (SPDE) and solid-phase fluorescence derivatization for the simple and rapid analysis of methamphetamine (MA) in urine. This method uses a reversed-phase polymeric solid-phase gel to clean up analytes in SPDE, followed by fluorescence derivatization with 9-fluorenylmethyl chloroformate (FMOC) in the solid-phase. The optimal conditions for SPDE and solid-phase fluorescence derivatization were obtained when J-SPEC PEP was used as the solid-phase gel and 0.5 mmol/L FMOC in 50 mmol/L borate buffer solution (pH 10) was used as the fluorescence derivatization reagent. The recovery experiment of MA in urine yielded a clean chromatogram with no interfering peaks, demonstrating the validity of our method; the recoveries were 83.6% when spiked at a low concentration level (100 ng/mL) and 80.7% when spiked at a high concentration level (1000 ng/mL). Compared with the conventional liquid-phase method, the reaction product (FMOC-MA) of solid-phase fluorescence derivatization had higher stability. Reaction rate constants were calculated by changing the temperature conditions, and physicochemical parameters, including activation energy and activation entropy involved in the degradation reaction, were obtained from the Arrhenius plot and analyzed thermodynamically. Taken together, our results suggest that the HPLC-FL method with SPDE and solid-phase fluorescence derivatization for sample pretreatment provides a simple and rapid means of analyzing MA in urine samples.

Development and evaluation of a novel fluorescent chiral derivatization reagent DBD-S-M-Pro: first observation of four chiral amino acids in human hair.

This study reports a novel fluorescent chiral derivatization reagent, 4-(N,N-dmethylaminosulfonyl)-2,1,3-benzoxadiazole-(2-succinimidoxy)-trans-2-methyl-L-proline (DBD-S-M-Pro), with a benzoxadiazole structure containing an N-hydroxysuccinimide activation group. DBD-S-M-Pro targets chiral amino-functional compounds under alkaline conditions without a condensation agent. Gradient elution was performed on a BEH C18 (100 × 2.1 mm, 1.7 μm) column with a mobile phase of 0.05% formic acid (FA) in 10 mM ammonium acetate (CH3COONH4) and 0.1% FA in acetonitrile or methanol. The efficiency of the chiral resolution was evaluated under excitation and emission wavelengths of 450 nm and 560 nm, respectively. The 19 chiral amino acids were separated in the range of 1.45-14.84. The resolutions of almost all DL-amino acids exceeded 1.5; the exceptions were serine (Ser) and lysine (Lys), with resolutions of 1.45 and 1.46, respectively. In addition, a new approach was devised for the simultaneous analysis of four chiral amino acids (DL-Glu, DL-Ala, DL-Val, and DL-Phe) in human hair. These amino acids were analyzed in the range of 12.5-400 pmol, with R2 ≥ 0.9990, limits of detection (S/N = 3) of 4-10 pmol, and intraday and interday precisions of 0.57-6.23%. The average spikes in the hair recoveries were 89.76-111.54%, and the matrix effects were 92.47-102.40%. Next, the contents of free chiral amino acids in the hair samples of 10 healthy volunteers (five males and five females) were analyzed with this method, and the differences were compared. The developed DBD-S-M-Pro provides a novel strategy for the sensitive determination of free chiral amino acids in living organisms.

Coumarin-based derivatization reagent for LC-MS analysis of amino acids

In this paper, we report about the application of a sensitive fluorescent derivatization reagent Coumarin151-N-Hydroxysuccinimidyl Carbamate (Cou151DSC) for amino compounds using high-performance liquid chromatography (HPLC) compatible with ultraviolet (UV), fluorescence detector (FLD) and electrospray ionization - tandem mass spectrometry (ESI-MS/MS)―positive mode. We optimized derivatization procedure and validated an analytical method to determine 24 amino acids in Kvass drink using Norvaline as an internal standard. Compared to 6-Aminoquinolyl-N-Hydroxysuccinimidyl Carbamate (6-AQC), the derivatization with Cou151 DSC is faster and milder, for 5 min at 40°C instead of 15 min at 55°C. The limit of quantitation (LOQ, pmol on column) for 21 amino acids in this work is lower 1.1–30.0 times than values obtained with 6-AQC. The derivatives have excitation wavelength at 355 nm and emission wavelength at 486 nm. Their MS/MS fragmentation behaviors were examined together with 23 other amino compounds. We found three possibilities to lose a neutral group which can be Coumarin 151 isocyanate Cou151NCO (255 Da), amine Coumarin 151 (229 Da) or urea Cou151CONH2 (272 Da). The accuracy of the proposed method was within 83–107% with good relative standard deviations (RSDs) of equal or less than 6%. The recoveries were from 82 to 120% in four spiked concentrations, repeatability was between 0 and 14%. The intra- and inter-day precision are less than 13% and 18%, respectively.

Determination of trans-fatty acids in food samples based on the precolumn fluorescence derivatization by high performance liquid chromatography.

Trans-fatty acids are unsaturated fatty acids that are considered to have health risks. 1,3,5,7-Tetramethyl-8-butyrethylenediamine-difluoroboradiaza-s-indacene is a highly sensitive fluorescent labeling reagent for carboxylic acids developed by our lab. In this study, using this precolumn fluorescent derivatization reagent, a rapid and accurate high-performance liquid chromatography with fluorescence detection method was developed for the determination of two trans-fatty acids in food samples. Under the optimized derivative conditions, two trans-fatty acids were tagged with the fluorescent labeling reagent in the presence of 1-ethyl-3-(3-dimethyl-aminopropyl) carbodiimide at 25°C for 30min. Then, the baseline separation of trans- and cis-fatty acids and their saturated fatty acid with similar structures was achieved with less interference using a reversed-phased C18 column with isocratic elution in 14min. With fluorescence detection at λex /λem =490 /510nm, the linear range of the TFAs was 1.0-200nM with low detection limits in the range of 0.1-0.2nM (signal-to-noise ratio=3). In addition, the proposed approach was successfully applied for the detection of trans-fatty acids in food samples, and the recoveries using this method ranged from 96.02 to 109.22% with low relative standard deviations of 1.2-4.3% (n=6).

A Highly Selective and Sensitive Chiral Derivatization Method for High- Performance Liquid Chromatographic Determination of the Stereoisomer Composition of Natural Products With Chiral Branched Alkyl Chains.

In the study of chiral biologically active compounds such as pheromones, the analysis of the stereoisomer composition is essential to gain more insight into their stereochemical diversity, which affects the pheromone communication channels and therefore the diversification of species. This mini-review summarizes the development of fluorescence derivatization reagents for high-performance liquid chromatographic (HPLC) determination of the absolute configuration and stereoisomer composition of natural products with a chiral branched alkyl chain. The diastereomeric separation of anteiso fatty acids bearing a branched methyl group up to the C-26 position was achieved by reversed-phase HPLC under very low column temperature conditions using (1S,2S)-2-(2,3-anthracenedicarboximido)cyclohexanol as a derivatization reagent, enabling fluorescent detection of these compounds at femtomole levels. This method was also applicable to chiral alcohols and amines with chiral branched methyl groups using similar reagents containing a carboxyl group. These reagents were successfully applied to determine the absolute configurations and stereoisomer composition of the chiral alkyl chain of natural compounds including some insect pheromones, miyakosyne A, and plakoside A. The combination of these reagents and two-dimensional HPLC constitutes a very powerful tool for the analysis of the stereoisomers of natural crude samples. Furthermore, the analysis of some natural bioactive substances using this method demonstrated that natural substances are not always optically pure, consisting instead of stereoisomer mixtures exhibiting stronger activity than optically pure enantiomers. These results cast doubts on the concept of biological homochirality and demonstrate that natural pheromones do not always show the highest activity among all stereoisomers.

Determination of intracellular 2-hydroxyglutarate enantiomers using two-dimensional liquid chromatography

In this study, a heart-cutting two-dimensional liquid chromatography (2D-LC) method for the determination of intracellular 2-hydroxyglutarate (2-HG) enantiomers is proposed. D-2-HG is an oncometabolite produced by tumors harboring isocitrate dehydrogenase (IDH) mutations. Hence, achieving accurate quantification of the 2-HG enantiomers in cancer cells is important. In this study, a fluorescence derivatization reagent, 4-nitro-7-piperazino-2,1,3-benzoxadiazole (NBD-PZ), was used. We found that 2-HG was successfully derivatized with NBD-PZ after lactonization. The enantiomers of 2-HG derivatized with NBD-PZ were quantified using the heart-cutting 2D-LC method. NBD-PZ-2-HG was stable for 1 week and was separated from endogenous compounds using an octadecyl silica column before enantiomeric separation on a chiral column. The developed heat-cutting 2D-LC method was validated and successfully applied to cell samples. The amount of D-2-HG and L-2-HG in U937 cells were 9.8 and 8.3 pmol/5.0 × 105 cells, respectively. Furthermore, high amounts of D-2-HG were measured in U937 cells expressing mutant IDH proteins as expected. This method can therefore be applied to further elucidate the role of 2-HG in cancer cells, particularly those harboring isocitrate dehydrogenase mutations.

A sensitive HPLC-FLD method for the quantitative determination of 3-chloro-1,2-propanediol by pre-column fluorescence derivatization with 9-(2-Hydroxypropyl)adenine

In this paper, a sensitive method for the determination of 3-chloro-1,2-propanediol (3-MCPD) by high performance liquid chromatography-fluorescence detection (HPLC-FLD) was established, in which 9-(2-Hydroxypropyl) adenine (HP-Ade) was selected as the fluorescent derivatization reagent because of its good water solubility and hydrophobicity. The principle of the method lies in the origination of chloroacetaldehyde with the periodate oxidation of 3-MCPD and its' fluorescence derivatization by HP-Ade to produce a strong fluorescent substance, name as 1-N6 -vinylidene-9-(2-hydroxypropyl)adenine (ε-HP-Ade), used for quantitative determination of 3-MCPD by HPLC-FLD. Some mobile phase conditions and incubation parameters related with the method features were studied and optimized. Under the optimal conditions, the method shows high sensitivity, good linearity (r 2 = 0.999) and good repeatability (RSD% between 1.04% and 2.55%), the detection limit (LOD) and quantification limit (LOQ) were 0.02 ng/mL and 0.06 ng/mL respectively. It has been successfully applied for the determination of various edible vegetable oil samples, the chromatogram shows symmetrical peak shape, perfect separation and very “clean” profiles. In comparison with gas chromatography-mass spectrum (GC-MS), the pretreatment process of the proposed method was totally operated in aqueous phase, the instrument requirements and cost are relatively lower, thus it will provide another choice for the routine analysis of 3-MCPD.

Quantification of Intracellular Thiols by HPLC-Fluorescence Detection.

Biothiols, such as cysteine and glutathione, play important roles in various intracellular reactions represented by the redox equilibrium against oxidative stress. In this study, a method for intracellular thiol quantification using HPLC-fluorescence detection was developed. Thiols were derivatized with a thiol-specific fluorescence derivatization reagent, viz. ammonium 7-fluoro-2,1,3-benzoxadiazole-4-sulfonate (SBD-F), followed by reversed-phase separation on an InertSustain AQ-C18 column. Six different SBD-thiols (homocysteine, cysteine, cysteinylglycine, γ-glutamylcysteine, glutathione, and N-acetylcysteine as an internal standard) were separated within 30 min using a citric buffer (pH 3.0)/MeOH mobile phase. The calibration curves of all the SBD-thiols had strong linearity (R2 > 0.999). Using this developed method, the thiol concentrations of human chronic myelogenous leukemia K562 cell samples were found to be 5.5–153 pmol/1 × 106 cells. The time-dependent effect of a thiol scavenger, viz. N-ethyl maleimide, on intracellular thiol concentrations was also quantified. This method is useful for elucidating the role of intracellular sulfur metabolism.

Simultaneous Determination of Free DL-Amino Acids in Natto with Novel Fluorescent Derivatization by UPLC-FL

A new simple and sensitive method for the simultaneous detection of free DL-amino acids (DL-AA) in natto was established by UPLC-fluorescence (FL) using the newly developed fluorescence derivatization reagent DBD-trans-2-methyl-L-proline (DBD-M-Pro) by precolumn derivatization. DBD-M-Pro reacts with DL-amino acids at 60 °C for 60 min. Using BEH C18 (2.1 mm × 100 mm, 1.7 μm) column gradient analysis for 20 min, the resolution of diastereomers after the derivatization of four DL-amino acids was 1.65–3.50. The detection limit for amino acids was 0.25–2.5 pmol. The average recovery (%) of DL-amino acids was 86.65–118.70%. The method was applied to the detection of chiral amino acids in natto beans and mucus, and four chiral amino acids, DL-Gln, DL-Asp, DL-Glu, and DL-Ala, were simultaneously detected. At the same time, the DL-amino acid content and D/L ratio of three different manufacturers of natto were compared quantitatively.

Synthesis and evaluation of dihydro-[1,2,4]triazolo[4,3-a]pyridin-2-ium carboxylates as fixed charge fluorescent derivatization reagents for MEKC and MS proteomic analyses

Proteinogenic amino acids were derivatized via coupling reactions with N-hydroxysuccinimide esters of Safirinium dyes. The obtained compounds were fully characterized by 1H and 13C NMR, IR, and ESI-MS spectral techniques. Elemental analysis, as well as the crystal structure analysis of exemplary compounds, were performed. The absorption and fluorescent properties of the obtained derivatives have been systematically investigated. The optical properties and very good water solubility allowed for the development of a simple method for the determination of exemplary amino acids by means of micellar electrokinetic chromatography. Moreover, a new class of fluorescent peptide building blocks comprising a spiro-conjugated Safirinium-proline system was obtained. Due to the presence of a permanent positive charge, Safirinium-amino acid dervatives are potential candidates for signal enhancers in MS proteomic analysis. The applicability of the examined ionization tags in signal enhancement and peptide sequencing was proved. The obtained results provide an experimental basis for the development of a new approach for trace amino acids, peptides, and proteins detection by means of absorption, fluorescence, and mass spectrometry.

Sensitive determination of malondialdehyde in rat prostate by high performance liquid chromatography with fluorescence detection

An excellent pre-column fluorescent derivatization reagent N-acetylhydrazine acridone for the quantitative determination of malondialdehyde was synthesized. Malondialdehyde was derivatized at 80 °C for 30 min in the presence of trichloroacetic acid. The separation of the derivative was performed on an Agilent ZORBAX SB-C18 column in conjunction with gradient elution. The excitation and emission wavelengths were 370 nm and 420 nm, respectively. The developed method demonstrated good linear relationship in the range of 0.02 pmol to 2.5 pmol (r = 0.9998). The calculated limit of detection and limit of quantification were 2.5 fmol and 8.3 fmol, respectively. The analytical precisions of the method were in the range of 1.36–2.27% (intra-day) and 2.36–3.92% (inter-day) respectively. The method was sensitive, specific and simple. It was successfully implemented to analysis the malondialdehyde in rat prostate.

Fluorescence detection of Trace Dimethylamine and Diethylamine in Natural Water by HPLC with O-phthalaldehyde and 7-chlore-4nitrobenzo-2-oax-1, 3-diazole

A method of detecting dimethylamine (DMA) and diethylamine (DEA) was developed by HPLC with pre-column derivatization and fluorescence detection in this paper. Two fluorescent derivatization reagents were chosed to used in the method including o-phthalaldehyde (OPA) and 7-chlore-4-nitrobenzo-2-oax-1,3-diazole (NBD-Cl). Aliphatic amines in the natural water were labeled in two steps, the water samples were firstly reacted with OPA to eliminate aliphatic primary amines interferences, and then NBD-Cl could be used to selective detection of secondary amines, including dimethylamine and diethylamine. The detection limits of the method were 0.1 nmol/L and 10 nmol/L for DMA and DEA. Both of the linear ranges were 0.0005-0.1mol/mL with correlation coefficients above 0.9978 and 0.9988. This method is repeatable, sensitive and accurate for the detection of DMA and DEA in natural water samples.

Screening of a highly effective fluorescent derivatization reagent for carbonyl compounds and its application in HPLC with fluorescence detection

Carbonyl compounds are widely distributed in organisms, and the commonly used methods for determination of them like UV/fluorescence/mass spectrometry always require derivatization reagents. However, the reported derivatization reagents have significant difference in reactivity, which is very unfavorable for developing highly reactive reagent. In this study, we theoretically investigated the factors affecting the reactivity of hydrazine-based derivatization reagents, and proposed a strategy for filtering highly reactive reagents by quantum chemical calculation. With this strategy, N-propyl-4-hydrazino-1,8-naphthalimide (NPHNA) was filtered out as a fluorescent derivatization reagent. Taking aliphatic aldehydes as representatives, we evaluated the reactivity of NPHNA for carbonyl compounds. The derivatization of NPHNA with aliphatic aldehydes could be finished at room temperature within 60 min or 35 °C within 35 min, which showed higher reactivity than the most popular UV/MS reagent, 2,4-dinitrophenylhydrazine (DNPH). We believe that the strategy we proposed in this work is of great potential to design highly reactive UV/fluorescent/MS labeling reagents for carbonyl compounds and even other analytes.

Enantioselective and simultaneous determination of lactate and 3-hydroxybutyrate in human plasma and urine using a narrow-bore online two-dimensional high-performance liquid chromatography system.

For the enantioselective and simultaneous analysis of lactate and 3-hydroxybutyrate, a validated online two-dimensional high-performance liquid chromatography system using 4-nitro-7-piperazino-2,1,3-benzoxadiazole as a fluorescent derivatization reagent has been developed. For the reversed-phase separation in the first dimension, a Capcell Pak C18 ACR column (1.5×250mm, particle size 3μm) was used, and the target fractions were isolated by their hydrophobicity. In the second dimension, a polysaccharide-coated enantioselective column, Chiralpak AD-H (2.0×250mm, 5μm), was used. The system was validated by the calibration curve, intraday precision, interday precision, and accuracy using standards and real human samples, and satisfactory results were obtained. The present method was applied to human plasma and urine, and in the plasma, trace amounts of d-lactate (8.4μM) and l-3-hydroxybutyrate (1.0μM), besides high levels of l-lactate (860.9μM) and d-3-hydroxybutyrate (59.4μM), were successfully determined. In urine, trace levels of d-lactate (3.7μM), d-3-hydroxybutyrate (2.3μM), and l-3-hydroxybutyrate (3.3μM) in addition to a relatively large amount of l-lactate (15.4μM) were observed. The present online two-dimensional high-performance liquid chromatography system is useful for the simultaneous determination of all the lactate and 3-hydroxybutyrate enantiomers in human physiological fluids, and further clinical applications are ongoing.

Development of a Fluorescent Labeling Reagent for Determination of Proline and Hydroxyproline in Myeloma Patient Plasma by HPLC-FLD.

A fluorescent derivatization reagent, 3,6-dimethoxy-9-phenyl-9H-carbazole-1-sulfonyl chloride (DPCS-Cl), previously designed, synthesized and developed for amino acids labeling, is here employed. It was used as a pre-column derivatization reagent for the determination of proline (Pro) and hydroxyproline (Hyp) with high-performance liquid chromatography. Both of the analytes were labeled with DPCS-Cl at 60°C for 30 min. The optimized concentration of DPCS-Cl was 25 µg mL-1 and the molar ratio of analytes to DPCS-Cl was 1:6. Excitation wavelength of 318 nm and emission wavelength of 440 nm were selected for the fluorescence detection. For Pro and Hyp, the linear correlation coefficients were all >0.999; the linear ranges of calibration curve were all 5.0 nmol L-1 to 5.0 μmol L-1; the detection limits were 20.0 and 10.0 fmol, respectively; the intra-day and inter-day relative standard deviations were 2.6-3.3% and 3.5-4.6%, respectively. This reagent was applied to the determination of Pro and Hyp in plasma of myeloma patients with its merits of high efficiency of derivatization, stability of the derivatives and high sensitivity.

An easy-to-use excimer fluorescence derivatization reagent, 2-chloro-4-methoxy-6-(4-(pyren-4-yl)butoxy)-1,3,5-triazine, for use in the highly sensitive and selective liquid chromatography analysis of histamine in Japanese soy sauces

In this study, a novel pre-column excimer fluorescence derivatization reagent, 2-chloro-4-methoxy-6-(4-(pyren-4-yl)butoxy)-1,3,5-triazine (CMPT), was developed for polyamines, specifically histamine. By CMPT derivatization, the polyamines, histamine and tyramine were converted to polypyrene derivatives, and emitted intra-molecular excimer fluorescence at 475nm. This could clearly be distinguished from the normal fluorescence emitted from reagent blanks at 375nm. Unlike conventional excimer fluorescence derivatization reagents, CMPT is chemically stable and its reactivity sustained over at least 36 days even in solution state. We successfully applied this reagent to the sensitive and selective analysis of histamine in different kinds of Japanese commercial soy sauces. The detection and quantification limits of histamine were 15 and 50μgL−1, respectively, equating to 1.35pmol and 4.5pmol for a 6μL injection. This sensitivity helped the direct analysis of soy sauce samples only treated by one-step liquid–liquid extraction without concentration. The histamine levels of commercial soy sauce samples (koikuchi, usukuchi and saishikomi) investigated were 1.24–768.5mgL−1.

Determination of Fatty Acids in Saliva of Smokers and Nonsmokers by HPLC with Fluorescence Detection Using a Hydrazine-Based Difluoro-boraindacene Reagent

1,3,5,7-Tetramethyl-8-daminozide-difluoroboradiaza-s-indacence (TMBODIPY-H), a pre-column fluorescent derivatization reagent, was applied to the analysis of fatty acid by high-performance liquid chromatography with fluorescence detection. Using this reagent, 12 fatty acids from propionic acid (C3) to stearic acid (C18) can be derivatized at room temperature in the presence of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide within 2 h. The baseline separation of these derivatives can be achieved within 46 min by gradient elution. The detection limits of these fatty acids are in the range of 0.1–1 nM and the linear ranges of most of them are 0.5–100 nM. This was the first application of hydrazine-based difluoro-boraindacene reagent for the analysis of fatty acids, and the proposed method has been successfully used for the determination of saliva samples of smokers and nonsmokers with recoveries of 88–110 %.

An integrated microfluidic chip for formaldehyde analysis in Chinese herbs

Abstract A novel integrated microfluidic chip with a three-layer polymethyl methacrylate (PMMA) structure is proposed for formaldehyde concentration detection applications. In the proposed device, the sample and a fluorescence derivatization reagent (Fluoral-P) are mixed in a circular mixing chamber and then flow through a serpentine reaction channel heated to a temperature of 30 °C by an integrated hotplate. Following a reaction time of 4 min, the microchip is removed from the hotplate and placed in the microscope stage of a laser-induced fluorescence (LIF) detection system. The formaldehyde concentration of the sample is then inversely derived from the measured value of the fluorescence intensity. The validity of the proposed device is confirmed by comparing the detection results obtained for standard samples with known formaldehyde concentrations ranging from 1 to 50 ppm with those obtained using a traditional UV/VIS absorption spectrometry. The real-world applicability of the proposed device is then demonstrated by measuring the formaldehyde concentration in ten commercial Chinese herbs. It is shown that the measurement results deviate by no more than 3.7% from those results obtained using colorimetric method by CAAPIC. Overall, the results presented in this study show that the proposed microchip provides a rapid and reliable tool for formaldehyde concentration measurement purposes.