Derivatization and liquid chromatography–UV–tandem mass spectrometric analysis of perfluorinated carboxylic acids

Precolumn Derivatization High-Performance Liquid Chromatography for Determination of Perfluorocarboxylic Acids in Catalytic Degradation Solutions

Perfluoroalkyl carboxylic acids (PFCAs), a series of ubiquitous contaminants in the global environment, attracted much attention due to their potential for high bioaccumulation and toxicity to various organisms. There are a lot of measurement requests in currently increasing degradation studies of PFCAs, which usually rely on expensive liquid chromatography-mass spectrometry (LC-MS). The degradation solutions containing high-concentration PFCAs can easily cause the pipeline pollution of the LC/MS instrument, which is usually used for trace analysis of environmental samples. In this study, a simple and reliable precolumn derivatization LC method coupled with an ultraviolet detector (UV) was developed for the determination of the main PFCAs (C_4-9) of environmental concern. These PFCAs in degradation solutions were crosslinked to UV-responsive 3, 4-diphenylamine (DCA) by a carbodiimidization method, followed by a simple solid-phase extraction (SPE) cleanup, and quantitatively measured using a conventional LC-UV instrument. Compared to previously reported precolumn derivatization methods, this new derivatization approach has the advantages such as mild reaction conditions, easy operation, enhanced stability of derivatives, and low cost. The instrumental limits of detection (ILDs) for the targeted PFCAs in organic and aqueous mediums were 0.2–0.5 and 0.6–1.5 mg/L, respectively. The method has been successfully applied to the determination of PFCAs in catalytic degradation solutions and recommended for use in other assays involving relatively high-concentration PFCAs.

Derivatization, an Applicable Asset for Conventional HPLC Systems without MS Detection in Food and Miscellaneous Analysis

One of the most valuable practices for analyzing not-so-analytical-friendly analytes in complex, heterogenous matrices is derivatization. Availability of numerous derivatizing reagents (DRs) makes the modification of analyte more exploitable in terms of an analytical perspective. A wide array of derivatization techniques like pre or post-column, in-situ, enzymatic, ultrasound-assisted, microwave-assisted, photochemical derivatization has added much-needed methodological strength in analyzing intricate analytical matrices (food, water, and soil). In recent years, analytical chemistry has achieved greater heights through the development of new sensitive methods with simple conventional instruments like High-Performance Liquid Chromatography (HPLC) devoid of Mass detectors. The prompt availability of these straightforward instruments also makes it a favorable option for routine analysis in food, environmental, bioanalytical chemistry. Analyzing food, environmental or bioanalytical specimen has some of the most problematic aspects, like the low concentration of the analytes accompanied by not too suitable analytical properties. Even though conventional HPLC lacks the required sensitivity but merger with derivatization can lead to a remarkable increase in sensitivity. In recent years there has been a lot of application of diverse derivatizations to increase the sensitivity and selectivity of the analyte for available instruments, resulting in notable findings. Therefore, this review describes the application of derivatization principles in the analysis of analytes in food and additional matrices using conventional HPLC instruments such as HPLC-UV, HPLC-DAD, and HPLC-FD. In this article, we will briefly review the different modes and multiple types of derivatizing reagents with their mechanisms and importance for encouraging the use of established HPLC instruments.

Chemical labeling strategies for small molecule natural product detection and isolation

Covering: Up to 2020.It is widely accepted that small molecule natural products (NPs) evolved to carry out a particular ecological function and that these finely-tuned molecules can sometimes be appropriated for the treatment of disease in humans. Unfortunately, for the natural products chemist, NPs did not evolve to possess favorable physicochemical properties needed for HPLC-MS analysis. The process known as derivatization, whereby an NP in a complex mixture is decorated with a nonnatural moiety using a derivatizing agent (DA), arose from this sad state of affairs. Here, NPs are freed from the limitations of natural functionality and endowed, usually with some degree of chemoselectivity, with additional structural features that make HPLC-MS analysis more informative. DAs that selectively label amines, carboxylic acids, alcohols, phenols, thiols, ketones, and aldehydes, terminal alkynes, electrophiles, conjugated alkenes, and isocyanides have been developed and will be discussed here in detail. Although usually employed for targeted metabolomics, chemical labeling strategies have been effectively applied to uncharacterized NP extracts and may play an increasing role in the detection and isolation of certain classes of NPs in the future.

Mass spectrometric detection of trace anions: The evolution of paired-ion electrospray ionization (PIESI)

The negative-ion mode of electrospray ionization mass spectrometry (ESI-MS) is intrinsically less sensitive than the positive-ion mode. The detection and quantitation of anions can be performed in positive-ion mode by forming specific ion-pairs during the electrospray process. The paired-ion electrospray ionization (PIESI) method uses specially synthesized multifunctional cations to form positively charged adducts with the anions to be analyzed. The adducts are detected in the positive-ion mode and at higher m/z ratios to produce excellent signal-to-noise ratios and limits of detection that often are orders of magnitude better than those obtained with native anions in the negative-ion mode. This review briefly summarizes the different analytical approaches to detect and separate anions. It focuses on the recently introduced PIESI method to present the most effective dicationic, tricationic, and tetracationic reagents for the detection of singly and multiply charged anions and some zwitterions. The mechanism by which specific structural molecular architectures can have profound effects on signal intensities is also addressed.