Corona Charged Aerosol Detector Research Articles

Universal response quantification approach using a Corona Charged Aerosol Detector (CAD) – Application on linear and cyclic oligomers extractable from polycondensate plastics polyesters, polyamides and polyarylsulfones

In terms of risk assessment especially for known and unknown substances migrating from food contact materials, quantification without corresponding reference substances currently poses a challenge. In the present study, the opportunity of a universal response quantification approach was evaluated by using a corona charged aerosol detector (CAD) for liquid chromatography combined with inverse gradient compensation. Characteristics of CAD detection in dependence of substance properties were analyzed with 46 randomly chosen reference substances. An almost equal CAD response (±20%) was achieved for non-volatile substances with a molecular weight of minimum 400 g/mol and a vapor pressure of maximum 10−8 Torr. We empirically defined an analytical parameter, Q50/35, the quotient of CAD peak areas at CAD evaporator temperatures of 50 °C and 35 °C, to predict the adequacy of the CAD universal response approach for quantification of known and unknown analyte substances. Exemplarily, we applied the CAD universal quantification approach for the determination of extractable oligomers below 1000 g/mol from a variety of food contact polycondensate plastic materials (e.g. polyesters like polyethylene terephthalate, polybutylene terephthalate, Tritan copolyester, polyamides 6, 6.6 and 6 T/6I and polyarylsulfones polyphenylsulfone and polyethersulfone). Quantitative results for in total 44 oligomers out of 11 materials were compared with established material-specific quantification methods using extracted oligomer mixtures as well as individual oligomers isolated from the mixtures. CAD-based quantification results were generally in accordance to published quantification approaches for polyamide oligomers and oligomers from polyarylsulfones. For oligomers extracted and isolated from polyester materials a slight underestimation was determined by CAD universal response approach. In terms of detection limits and accuracy, the universal CAD approach exhibits no advantages compared to established UV-methods, to date.

Quantitative analysis of underivatized amino acids in the sub- to several-nanomolar range by ion-pair HPLC using a corona-charged aerosol detector (HPLC–CAD)

The separation and quantification of underivatized naturally occurring amino acids (AAs) by high-performance liquid chromatography (HPLC) is advantageous for reducing preparation time, running costs, and analytical errors, and is compatible with the isolation of intact AAs. This study establishes and validates an analytical method for the separation and quantification of underivatized AAs and taurine (Tau) in the sub- to several-nanomolar range (ca. 0.1–1.6 nmol) by optimizing ion-pair HPLC coupled to a corona charged aerosol detector (corona CAD). Chromatographic separation of 19 AAs and Tau was achieved using a porous graphite carbon (PGC) column and nonafluoropentanoic acid (NFPA) as a volatile ion-pair reagent. The response of the corona CAD to the AAs was highly dependent on the eluate composition, whereas these response factors were similar for AAs in eluate with similar compositions. Regression curves and coefficients (r2) >0.998 were obtained for plots of injection amount versus peak area, except for Arg which co-eluted with a background peak. On the other hand, all plots of injection amount versus peak height regressed to curves with r2 > 0.997. Repeat quantification based on peak area showed lower relative standard deviations (RSDs) (typically better than 5%) than those based on peak height. The present method is useful for quantifying AAs from proteins and Tau in the sub- to several-nanomolar range without derivatization, and constant repeatability can be maintained by quantification using peak areas.

Rapid separation and simultaneous quantitative determination of 13 constituents in Psoraleae Fructus by a single marker using high-performance liquid chromatography with diode array detection.

Psoraleae Fructus is one of the most popular traditional Chinese medicines. Coumarins, flavonoids, and meroterpenes are the main contributors to the biological activity of Psoraleae Fructus. In this study, a new method for the quality control of Psoraleae Fructus was developed, through the quantitative analysis of multicomponents by single marker with diode array detector. Thirteen components, including psoralenoside, isopsoralenoside, psoralen, isopsoralen, psoralidin, neobavaisoflavone, bavachin, corylin, isobavachalcone, corylifol A, bavachinin, bavachalcone, and bakuchiol were rapidly separated and identified within 12min by the newly developed method. The feasibility and reliability of this method were corroborated. The method was also compared to the external standard method and detection by corona charged aerosol detector. The results of percent difference (%) and cos (θ) have shown that there were no significant differences observed between the quantitative analysis of multicomponents by single marker and external standard method analyses; psoralen and isopsoralen were undetectable with the corona charged aerosol detector due to their but the sensitivity for all the compounds except bakuchiol detected by corona charged aerosol detector are higher than those obtained by diode array detector. In addition, the newly method developed was applied to the quality evaluation of Chinese patent medicines containing Psoraleae Fructus.

A UHPLC method for the rapid separation and quantification of phytosterols using tandem UV/Charged aerosol detection – A comparison of both detection techniques

The presented work describes the development and validation of a rapid UHPLC-UV/CAD method using a core–shell particle column for the separation and quantitative analysis of seven plant sterols and stanols. The phytosterols (ergosterol, brassicasterol, campesterol, fucosterol, stigmasterol, and β-sitosterol) and the phytostanol stigmastanol were separated and analyzed in 8.5min. The sample pre-treatment procedure was optimized to be less time-consuming than any other published method, especially due to no need of derivatization, evaporation and even reconstitution step. The chromatographic separation was performed on the Kinetex 1.7μ Phenyl-hexyl column (100×2.1mm) with a mobile phase acetonitrile/water according to the gradient program at a flow rate of 0.9mLmin−1 and a temperature of 60°C. A tandem connection of PDA and CAD (Corona Charged Aerosol Detector) was used and both detection techniques were compared. The method was validated using saponification as a first step in sample pre-treatment and an universal CAD as the detector. Recoveries for all analyzed compounds were between 95.4% and 103.4% and relative standard deviation ranged from 1.0% to 5.8% for within-day and from 1.4% to 6.7% for between-day repeatability. The limits of detection were in the range of 0.4–0.6μgmL−1 for standard solutions and 0.3–1.2μgmL−1 for phytosterols in real samples. Although several gradient programs and different stationary phases were tested, two compounds, campesterol and campestanol, were not separated. Their peak was quantified as a sum of both analytes.

Concurrent estimation of metabolite concentrations along with parent drug quantification in post-mortem blood

There is a constant demand for the quantification of drug metabolites within post-mortem toxicology. Especially electrospray ionization–mass spectrometry techniques necessitate that calibration is carried out using primary reference standards due to the non-uniform ionization efficiency between parent drugs and their metabolites. As reference standards for metabolites are not readily available and their costs are high, alternative methods for immediate quantification are required. In this study, ultra-high performance liquid chromatography coupled with photodiode array detection and corona charged aerosol detection was utilized for the concurrent quantification of 23 drug metabolites using the corresponding parent drug for calibration. Based on this secondary calibration, the quantitative results for the N-demethylated metabolites by each detector were similar to those obtained by the ordinary calibration using reference standards. For O-demethylated metabolites, the differences in detector response caused somewhat larger biases using the secondary calibration. Using the validated secondary calibration, the blood sample data gathered from 633 post-mortem cases was retrospectively re-processed to discover the combined metabolite–parent concentrations and metabolite to parent ratios for six toxicologically relevant drugs. These results, representing all causes of death, were compared to published data from therapeutic drug monitoring and post-mortem toxicology.

Estimation of the Intestinal Absorption and Metabolism Behaviors of 2- and 3-Monochloropropanediol Esters.

The regioisomers of the di- and mono-oleate of monochloropropanediol (MCPD) have been synthesized and subsequently hydrolyzed with pancreatic lipase and pancreatin to estimate the intestinal digestion and absorption of these compounds after their intake. The hydrolysates were analyzed by HPLC using a corona charged aerosol detection system, which allowed for the separation and detection of the different regioisomers of the MCPD esters. The hydrolysates were also analyzed by GC-MS to monitor the free MCPD. The results indicated that the two acyl groups of 2-MCPD-1,3-dioleate were smoothly hydrolyzed by pancreatic lipase and pancreatin to give free 2-MCPD. In contrast, the hydrolysis of 3-MCPD-1,2-dioleate proceeded predominantly at the primary position to produce 3-MCPD-2-oleate. 2-MCPD-1-oleate and 3-MCPD-1-oleate were further hydrolyzed to free 2- and 3-MCPD by pancreatic lipase and pancreatin, although the hydrolysis of 3-MCPD-2-oleate was 80% slower than that of 3-MCPD-1-oleate. The intestinal absorption characteristics of these compounds were evaluated in vitro using a Caco-2 cell monolayer. The results revealed that the MCPD monooleates, but not the MCPD dioleates, were hydrolyzed to produce the free MCPD in the presence of the Caco-2 cells. The resulting free MCPD permeated the Caco-2 monolayer most likely via a diffusion mechanism because their permeation profiles were independent of the dose. Similar permeation profiles were obtained for 2- and 3-MCPDs.

Development and validation of a stability-indicating RP-HPL C-CAD method for gabapentin and its related impurities in presence of degradation products

The objective of the current study was to develop and validate a sensitive and specific LC–MS compatible stability indicating reversed phase liquid chromatographic method for the quantitative determination of Gabapentin and its related substances using Corona charged aerosol detection (CAD). The chromatographic conditions were optimized using a Kinetix Biphenyl column with gradient elution using a mobile phase composed of pH 4.2 ammonium acetate, acetonitrile, and methanol. Forced degradation was observed in basic and peroxide conditions and the major degradants were identified by LC–MS/MS analysis. The developed RP-HPLC CAD method was validated according to ICH guidelines. The LOD and LOQ values for Gabapentin and all its related impurities ranged from 0.075μg/mL to 0.18μg/mL and 0.25μg/mL to 0.60μg/mL, respectively. The recovery for all impurities ranged from 91.0 to 105.6%w/w. Solutions were stable for 7days at room temperature. The validated method produced acceptable precision, linearity, accuracy, robustness and ruggedness.

Simultaneous analysis of silicon and boron dissolved in water by combination of electrodialytic salt removal and ion-exclusion chromatography with corona charged aerosol detection

Selective separation and sensitive detection of dissolved silicon and boron (DSi and DB) in aqueous solution was achieved by combining an electrodialytic ion isolation device (EID) as a salt remover, an ion-exclusion chromatography (IEC) column, and a corona charged aerosol detector (CCAD) in sequence. DSi and DB were separated by IEC on the H+-form of a cation exchange resin column using pure water eluent. DSi and DB were detected after IEC separation by the CCAD with much greater sensitivity than by conductimetric detection. The five-channel EID, which consisted of anion and cation acceptors, cathode and anode isolators, and a sample channel, removed salt from the sample prior to the IEC-CCAD. DSi and DB were scarcely attracted to the anion accepter in the EID and passed almost quantitatively through the sample channel. Thus, the coupled EID–IEC–CCAD device can isolate DSi and DB from artificial seawater and hot spring water by efficiently removing high concentrations of Cl− and SO42− (e.g., 98% and 80% at 0.10molL−1 each, respectively). The detection limits at a signal-to-noise ratio of 3 were 0.52μmolL−1 for DSi and 7.1μmolL−1 for DB. The relative standard deviations (RSD, n=5) of peak areas were 0.12% for DSi and 4.3% for DB.

Impurity profiling of ibandronate sodium by HPLC–CAD

The modern bisphosphonate drug ibandronate sodium, a challenging candidate for impurity profiling, was analyzed using high performance liquid chromatography (HPLC) combined with corona charged aerosol detection (CAD). Separation was achieved on a mixed mode column combining hydrophobic C18 and strong anion exchange retention mechanisms using a mass spectrometer compatible volatile mobile phase consisting of trifluoroacetic acid and acetonitrile while gradient elution was applied. The method was validated following the ICH guideline Q2(R1) and found suitable for the assessment of ibandronate’s related substances. The observed CAD-response for all identified impurities was linear (R2>0.995) over a small concentration range (0.05–0.25) and a quantification limit of at least 0.03% was found. Four batches of two different manufacturers were tested by means of the method. None of the batches contained a single impurity above 0.05%. The major impurities of all batches were the synthesis by-products N-desmethyl- and N-despentyl ibandronate as well as N,N-dimethyl pamidronate.

Acetone as a greener alternative to acetonitrile in liquid chromatographic fingerprinting.

A considerable amount of chemical waste from liquid chromatography analysis is generated worldwide. Acetonitrile is the most employed solvent in liquid chromatography analyses since it exhibits favorable physicochemical properties for separation and detection, but it is an unwelcome solvent from an environmental point of view. Acetone might be a much greener alternative to replace acetonitrile in reversed-phase liquid chromatography, since both share similar physicochemical properties, but its applicability with ultraviolet absorbance-based detectors is limited. In this work, a reference method using acetonitrile and high-performance liquid chromatography coupled to an ultraviolet photodiode array detector coupled to a corona charged aerosol detector system was developed to fingerprint a complex sample. The possibility of effectively substituting acetonitrile with acetone was investigated. Design of experiments was adopted to maximize the number of peaks acquired in both fingerprint developments. The methods with acetonitrile or acetone were successfully optimized and proved to be statistically similar when only the number of peaks or peak capacity was taken into consideration. However, the superiority of the latter was evidenced when parameters of separation and those related to greenness were heuristically combined. A green, comprehensive, time- and resource-saving approach is presented here, which is generic and applicable to other complex matrices. Furthermore, it is in line with environmental legislation and analytical trends.

Effects of densities of brominated flame retardants on the detection response for HPLC analysis with a corona-charged aerosol detector.

Dependence of the response of a corona-charged aerosol detector (corona CAD) on the concentration and densities of brominated flame retardants and some related substrates was studied. The calibration curves of the substrates did not show linearity and the substrate with a lower density exhibited the stronger response. Regardless of the solvents (chloroform or toluene), and the injected volume of the substrate solution, the signal intensity of the substrate observed by a corona CAD was substantially proportional to 2/3 power law of concentration and proportional to (-2/3) power law of the density of the substrates. These results suggest that the responses should be proportional to the surface area of the particles generated through the drying process in corona CAD. Contrary to the former reports that the detector response of a corona CAD was independent of chemical species, it was proved that the response varies with the density of a substrate.

Determination of perfluorinated carboxylic acids in water using liquid chromatography coupled to a corona-charged aerosol detector

Perfluorocarboxylic acids (PFCAs) are persistent pollutants being widely detected in the environment. In order to quantitatively determine PFCAs, a simple and rapid method for the simultaneous determination of five PFCAs was developed by coupling high performance liquid chromatographic (HPLC) separation and corona-charged aerosol detector (CAD). The PFCAs were separated on a Symmerry® C8 analytical column (150mm×3.9mm) under isocratic conditions with a mobile phase consisting of 5mM ammonium acetate (pH4.9±0.2) and methanol (30:70 (v/v)) at the flow rate 1mLmin−1. Ammonium acetate as ion pairing agent was added to the mobile phase for better separation and peak shapes. The elaborated method was validated for linearity, precision and accuracy. The detection limits ranged from 1.5 to 4.4μgL−1 for PFCAs with C atoms of C4 to C8, which were decreased further to 75 to 220ngL−1 after 20-fold preconcentration. The method was confirmed to have good precision with relative standard deviation of 0.9%-4.2% for intraday measurements and 0.9%-4.1% for interday measurements. The optimized method was applied to analyze practical wastewater samples with satisfactory results.

Phytochemical investigations of Polygonum aviculare, Agrimonia eupatoria and Lythrum salicaria by HPLC-DAD-MS3-CAD method – application of corona charged aerosol detection (CAD) for analysis of plant phenolics

The examination and standardization of traditionally used plant materials is often based on old-fashion methods that seem to be not fully reliable. The HPLC coupled with DAD and mass spectrometer method is a powerful tool for the proper identification of plant phenolics. Charged aerosol detection (CAD) in liquid chromatography is a relatively new technic introduced in 2002 [1]. It has been shown that the response of CAD does not depend on the structure or molecular mass of analyzed substances so it can be utilized as universal response device for HPLC. There are a few reports on possible applications of CAD for the analysis of plant extracts. The aim of the study was to investigate the chemical composition of chosen plant materials using HPLC-DAD-MS3 method and to quantify their major constituents using CAD. The application of CAD as a universal response detector for plant phenolics was also evaluated. The chemical investigation of Polygoni avicularis herba, Agrimoniae eupatoriae herba and Lythri herba has shown that all three plant materials are a rich source of plant phenolics including flavonoids, tannins and phenolic acids [2 – 3]. Most of detected compounds were fully identified showing that examined plant materials contain constituents that have not been previously detected and some of them have been isolated as new natural products. The quantification of major compounds of A. eupatoria and L. salicaria with CAD showed that the in the case of plant phenolics the response of CAD may vary significantly depending on the compound analyzed [3 – 4]. The proper investigation of CAD response for chemical standards and analysed compounds should be carried out and must not be omitted.

Photodiode array to charged aerosol detector response ratio enables comprehensive quantitative monitoring of basic drugs in blood by ultra-high performance liquid chromatography

Quantitative screening for a broad range of drugs in blood is regularly required to assess drug abuse and poisoning within analytical toxicology. Mass spectrometry-based procedures suffer from the large amount of work required to maintain quantitative calibration in extensive multi-compound methods. In this study, a quantitative drug screening method for blood samples was developed based on ultra-high performance liquid chromatography with two consecutive detectors: a photodiode array detector and a corona charged aerosol detector (UHPLC–DAD–CAD). The 2.1mm×150mm UHPLC column contained a high-strength silica C18 bonded phase material with a particle size of 1.8μm, and the mobile phase consisted of methanol/0.1% trifluoroacetic acid in gradient mode. Identification was based on retention time, UV spectrum and the response ratio from the two detectors. Using historic calibration over a one-month period, the median precision (RSD) of retention times was 0.04% and the median accuracy (bias) of quantification 6.75%. The median precision of the detector response ratio over two orders of magnitude was 12%. The applicable linear ranges were generally 0.05–5mgL−1. The method was validated for 161 compounds, including antipsychotics, antidepressants, antihistamines, opioid analgesics, and adrenergic beta blocking drugs, among others. The main novelty of the method was the proven utility of the response ratio of DAD to CAD, which provided the additional identification efficiency required. Unlike with mass spectrometry, the high stability of identification and quantification allowed the use of facile historic calibration.

Construction of a wireless communication contact closure system for liquid chromatography with multiple parallel mass spectrometers and other detectors.

A contact closure system was constructed that uses two contact closure sender boards that communicate wirelessly to four contact closure receiver boards to distribute start signals from two or three liquid chromatographs to 14 instruments, pumps, detectors, or other components. Default high, closed low, TTL logic (5-volt) start signals from two autosamplers are converted to simple contacts by powered relay boards that are then connected to two 16-channel wireless contact closure sender boards. The contact closure signals from the two sender boards are transmitted wirelessly to two pairs of eight-channel receiver boards (total of 32 contact signals) that distribute the start signal to 14 switches that allow selection of which start signal is sent to which instrument, pump, or detector. The contact closure system is used for quadruple parallel mass spectrometry experiments in which four mass spectrometers, using three different atmospheric pressure ionization modes, plus a UV detector, an evaporative light-scattering detector, a corona charged aerosol detector, and two syringe pumps supplying electrolyte, are all synchronized to start simultaneously. A wide variety of liquid chromatography-mass spectrometry experiments using multiple liquid chromatographs and mass spectrometers simultaneously, LCx/MSy, including column-switching experiments, can be reconfigured simply by toggling switches.

Assessment of the complementarity of temperature and flow-rate for response normalisation of aerosol-based detectors

The solvent dependency of the detection response is a major limitation of corona-charged aerosol detection (C-CAD). The present study empirically investigates the utility of temperature and flow-rate gradients to overcome solvent gradient limitations of C-CAD. In preliminary flow-injection investigations, it is demonstrated that the response of C-CAD remains relatively unaltered with variations in flow-rate when used with water-rich eluents. Based on these findings two separation approaches were developed and their utility for C-CAD response normalisation was demonstrated using a mixture of eight analytes. In the first approach the use of a solvent gradient is replaced with a temperature gradient performed under isocratic mobile phase conditions. Detection response is further enhanced by mixing a secondary stream of pure acetonitrile with the column effluent, yielding a 3-fold increase in detection response. In the second approach, flow-rate programming is used to improve speed of isocratic-temperature gradient separation. The use of simultaneous variation in flow-rate and column temperature reduced the separation time by 30%, with relatively uniform analyte response. Lastly, an inverse-gradient solvent compensation approach was used to evaluate the response homogeneity and the applicability of the above approaches for quantitative analysis. Good peak area reproducibility (RSD%<15%) and linearity (R2>0.994, on a log-scale) over the sample mass range of 0.1–10μg was achieved. The response deviation across the mixture of eight compounds at seven concentration levels was 6–13% compared to 21–39% when a conventional solvent gradient was applied and this response deviation was comparable to that obtained in the inverse gradient solvent compensation approach. Finally, applicability of these approaches for typical pharmaceutical impurity profiling was demonstrated at a concentration of 5μg/mL (0.1% of the principal compound).

Simultaneous separation and determination of erythritol, xylitol, sorbitol, mannitol, maltitol, fructose, glucose, sucrose and maltose in food products by high performance liquid chromatography coupled to charged aerosol detector

A simple, sensitive and accurate method for simultaneous determination of glucose, fructose, sucrose, maltose, erythritol, mannitol, maltitol, sorbitol and xylitol by high pressure liquid chromatography coupled to Corona charged aerosol detector (CAD) is reported for the first time. The method was elaborated using a Shodex Asahipak, NH2P-50 4E, column packed with 5μm shell particles (4.6 × 250 mm) and acetonitrile–water gradient mobile phase at 25°C. The method was validated for linearity, precision and accuracy. It was characterized by wide concentration range (1–100μgml−1) and good accuracy (95.6–105%). LOD and LOQ for nine analytes were in the range of 0.12–0.44μgml−1 and 0.40–1.47μgml−1, respectively. The method offers excellent linearity with regression coefficient r>0.999 and good repeatability (RSD < 5%). The results obtained for real samples illustrate the ability of the proposed method to quantify a range of sugars and sugar alcohols in a single analysis, making it appropriate for food analysis.

O31: Comprehensive non-MS drug screening by UPLC-PDA-CAD with durable quantitative calibration

Introduction Mass spectrometric (MS) methods are today widely used in analytical toxicology, but in comprehensive quantitative drug screening it is laborious to maintain quantitative calibration and use of historic calibration is not feasible. In non-MS gas chromatographic (GC) and liquid chromatographic (LC) methods, historic calibration is widely used. However, GC is not amenable to analysis of current polar drugs and traditional LC-UV methods do not have high enough identification power to meet the requirements of screening. Ultra-performance LC (UPLC) with two consecutive detectors appears to possess high potential for simultaneous multi-component screening and quantification. In this study, a comprehensive quantitative screening method for 170 basic drugs in blood samples was developed and validated using UPLC coupled with photodiode array (PDA) and corona charged aerosol detector (CAD). Methods Blood samples were extracted with organic solvent (ethyl acetate: butyl acetate, 25:75) in basic conditions. After extraction, the organic solvent was evaporated to dryness and samples were reconstituted with the UPLC mobile phase. Dibenzepine was used as an internal standard. Chromatographic separation was performed at 60 °C using a HSS C18 column (150 mm × 2,1 mm, particle size 1,8 μm), and the mobile phase consisted of 0.1% trifluoroacetic acid and methanol. After a three minute isocratic phase, a linear gradient from 5% to 95% methanol in 15 minutes followed. The flow rate was 0.4 mL/min. UV spectra were collected in the range of 210–400 nm, and wavelength of 230 nm was used for quantification. Substance identification was based on the UV spectrum, retention times on both detectors, and the response ratio of CAD and PDA at wavelength 230 nm. Calibration was carried out using a single calibration point at the vicinity of the upper limit of therapeutic range of each drug. Individual calibration curves were created for both detectors and the average result was used for quantification. Results The retention times were found be very stable, the relative standard deviation of retention times being Conclusion The developed method allows the detection and quantification of 170 basic drugs in therapeutic and toxic concentrations in a single run. Due to the stability of calibration and good linearity, historic one-point calibration can be utilized. Adding the CAD detector with universal response after the PDA detector increases the reliability of both identification and quantification. In addition, drugs with poor UV absorption can be detected and quantitated. This method provides a tool for comprehensive quantitative screening for ordinary basic drugs in blood and leaves LC-MS target analysis to be applied to low-dose compounds.

Impurity profiling of carbocisteine by HPLC-CAD, qNMR and UV/vis spectroscopy

For the impurity profiling of the mucolytic and anti-inflammatory drug carbocisteine a high performance liquid chromatographic (HPLC) method using corona charged aerosol detection (CAD) was developed and fully validated following the ICH guideline Q2(R1). The response was linear (R2>0.995) over a small concentration range (0.05–0.25 or 0.10–0.60% respectively) and a detection limit of at least 0.03% was registered. The separation was achieved on a mixed mode column combining hydrophobic C18 and strong cation exchange retention mechanisms using a mass spectrometer compatible volatile mobile phase consisting of trifluoroacetic acid 10mM and acetonitrile 12% (V/V). Impurities, not assessable by HPLC-CAD such as the volatile chloroacetic acid and the unstable cysteine, were determined by quantitative NMR (qNMR) with maleic acid as internal standard and UV/vis spectroscopy after reaction with Ellman's reagent, respectively. Six batches of three different manufacturers were tested by means of those methods. The purity varied from below 99.0 to higher than 99.8 per cent. The major impurities of all batches were the starting material cystine and N,S-dicarboxymethylcysteine being a synthesis by-product.

Fumonisin Measurement from Maize Samples by High-Performance Liquid Chromatography Coupled with Corona Charged Aerosol Detector

Fumonisins are a class of mycotoxins produced mainly by Fusarium species, which is primary fungal contaminant of the maize and maize-derived products around the world. The B-series fumonisins (FB1, FB2 and FB3) are the most abundant and toxic constituent; thus, their levels are regulated generally worldwide. In this study, we developed a reliable method for the measurement of fumonisin FB1, FB2 and FB3 mycotoxins from maize samples without the time-consuming derivatization step using a high-performance liquid chromatograph coupled with corona charged aerosol detector. The detection and quantitation limit of the whole method were 0.02 and 0.04 mg/kg for each fumonisins, respectively. The detection linearity was tested in the calibration range of 2 orders of magnitude and the recoveries from the spiked samples were determined. The developed method proved to be sufficient to measure the maximum residue levels of fumonisins, which are specified in European Union and United States in maize and maize-based products.