Chemiluminescent Nitrogen Detector Research Articles

Topiramate: A Review of Analytical Approaches for the Drug Substance, Its Impurities and Pharmaceutical Formulations.

An important step during the development of high-performance liquid chromatography (HPLC) methods for quantitative analysis of drugs is choosing the appropriate detector. High sensitivity, reproducibility, stability, wide linear range, compatibility with gradient elution, non-destructive detection of the analyte and response unaffected by changes in the temperature/flow are some of the ideal characteristics of a universal HPLC detector. Topiramate is an anticonvulsant drug mainly used for the treatment of different types of seizures and prophylactic treatment of migraine. Different analytical approaches to quantify topiramate by HPLC have been described because of the lack of chromophoric moieties on its structure, such as derivatization with fluorescent moieties and UV-absorbing moieties, conductivity detection, evaporative light scattering detection, refractive index detection, chemiluminescent nitrogen detection and MS detection. Some methods for the determination of topiramate by capillary electrophoresis and gas chromatography have also been published. This systematic review provides a description of the main analytical methods presented in the literature to analyze topiramate in the drug substance and in pharmaceutical formulations. Each of these methods is briefly discussed, especially considering the detector used with HPLC. In addition, this article presents a review of the data available regarding topiramate stability, degradation products and impurities.

A charged aerosol detector/chemiluminescent nitrogen detector/liquid chromatography/mass spectrometry system for regular and fragment compound analysis in drug discovery

In this paper, we introduce a high throughput LCMS/UV/CAD/CLND system that improves upon previously reported systems by increasing both the quantitation accuracy and the range of compounds amenable to testing, in particular, low molecular weight “fragment” compounds. This system consists of a charged aerosol detector (CAD) and chemiluminescent nitrogen detector (CLND) added to a LCMS/UV system. Our results show that the addition of CAD and CLND to LCMS/UV is more reliable for concentration determination for a wider range of compounds than either detector alone. Our setup also allows for the parallel analysis of each sample by all four detectors and so does not significantly increase run time per sample.

Direct determination of acrylamide in food by gas chromatography with nitrogen chemiluminescence detection

A method of gas chromatography with nitrogen chemiluminescence detection and using standard addition is described for the determination of acrylamide in heat-processed foods. Using a modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) sample preparation method removes the acrylamide precursors completely, and the risk of overestimating acrylamide concentration due to additional analyte formation in the hot gas chromatograph inlet is also avoided. Sample preparation is rapid and inexpensive. A Deans switch device is utilized to heart-cut acrylamide and to prevent interferences from the solvent and matrix from reaching the detector. The pre-column is backflushed at high temperature to maintain a clean baseline and shorten the cycle time compared to baking out the column. Quantitation using standard addition is employed for compensation of potential variability in the acrylamide extraction efficiency in acetonitrile. The limit of detection and the limit of the quantification obtained for this method are 27 and 81 μg/kg, respectively, in food samples (equivalent to 3.5 and 10.6 μg/L in acetonitrile, respectively), and the linear range is 76-9697 μg/kg in food samples (equivalent to 10-1280 μg/L in acetonitrile) with an R(2) value of 0.9999.

Topiramate: a review of analytical approaches for biological matrices.

Topiramate is an anticonvulsant drug and it has been used worldwide for a wide range of applications. It is mainly indicated for the treatment of partial and generalized seizures, including Lennox Gastant Syndrome and generalized tonic-clonic seizures, and prophylactic treatment of migraine. Different analytical approaches by high-performance liquid chromatography have been described to analyze topiramate because of its lack of chromophore groups, including derivatization with UV-absorbing moieties, derivatization with fluorescent moieties, refractive index detection, conductivity detection, chemiluminescent nitrogen detection, evaporative light scattering detection and MS detection. In addition, some methods for determination of topiramate by capillary electrophoresis have been published as well as by gas chromatography. Thus, it is beneficial to evaluate and compare these papers before selecting the most suitable method/detector to analyze this drug. This systematic review provides a description of the main analytical methods available for the analysis of topiramate in biological matrices. Each of these methods is briefly discussed considering the detector used with HPLC. HPLC coupled with MS is the main technique used for topiramate analysis in biological matrices, mainly in the electrospray ionization-negative mode.

Comprehensive compositional analysis of sulfur and nitrogen containing compounds in shale oil using GC × GC – FID/SCD/NCD/TOF-MS

The detailed composition of a shale oil was determined using a novel comprehensive 2D gas chromatographic (GC×GC) method, extending the method of Dijkmans et al. (2014). Four different detectors (flame ionization detector (FID), sulfur chemiluminescence detector (SCD), nitrogen chemiluminescence detector (NCD) and time of flight mass spectrometer (TOF-MS)) mounted on different GC×GC’s were used. The use of two internal standards; 2-chloropyridine and 3-chlorothiophene; allowed quantification of the shale oil’s composition by carbon number and by structural class. 20 different classes were detected in the shale oil: paraffins, isoparaffins, olefins/mononaphthenes, dinaphthenes, monoaromatics, naphthenoaromatics, diaromatics, naphthenodiaromatics, triaromatics, thiols/sulfides, benzothiophenes, naphtenobenzothiophenes, dibenzothiophenes, pyridines, anilines, quinolines, indoles, acridines, carbazoles and phenols. A significant amount of sulfur and nitrogen containing compounds, 2.2wt% and 4.2wt% respectively, were detected.

Detailed compositional characterization of plastic waste pyrolysis oil by comprehensive two-dimensional gas-chromatography coupled to multiple detectors

The detailed compositional characterization of plastic waste pyrolysis oil was performed with comprehensive two-dimensional GC (GC×GC) coupled to four different detectors: a flame ionization detector (FID), a sulfur chemiluminescence detector (SCD), a nitrogen chemiluminescence detector (NCD) and a time of flight mass spectrometer (TOF-MS). The performances of different column combinations were assessed in normal i.e. apolar/mid-polar and reversed configurations for the GC×GC–NCD and GC×GC–SCD analyses. The information obtained from the four detectors and the use of internal standards, i.e. 3-chlorothiophene for the FID and the SCD and 2-chloropyridine for the NCD analysis, enabled the identification and quantification of the pyrolysis oil in terms of both group type and carbon number: hydrocarbon groups (n-paraffins, iso-paraffins, olefins and naphthenes, monoaromatics, naphthenoaromatics, diaromatics, naphthenodiaromatics, triaromatics, naphthenotriaromatics and tetra-aromatics), nitrogen (nitriles, pyridines, quinolines, indole, caprolactam, etc.), sulfur (thiols/sulfides, thiophenes/disulfides, benzothiophenes, dibenzothiophenes, etc.) and oxygen containing compounds (ketones, phenols, aldehydes, ethers, etc.). Quantification of trace impurities is illustrated for indole and caprolactam. The analyzed pyrolysis oil included a significant amount of nitrogen containing compounds (6.4wt%) and to a lesser extent sulfur containing compounds (0.6wt%). These nitrogen and sulfur containing compounds described approximately 80% of the total peak volume for respectively the NCD and SCD analysis. TOF-MS indicated the presence of the oxygen containing compounds. However only a part of the oxygen containing compounds (2.5wt%) was identified because of their low concentrations and possible overlap with the complex hydrocarbon matrix as no selective detector or preparative separation for oxygen compounds was used.

Straightforward single-calibrant quantification of seized designer drugs by liquid chromatography–chemiluminescence nitrogen detection

Sixty-one different psychoactive substances were quantified by liquid chromatography–chemiluminescence nitrogen detection (LC–CLND) in 177 samples, using a single secondary standard (caffeine), in a trial concerning the quantitative purity assessment of drug-related material seized by the police in 2011–2012 and customs in 2011–2013 in Finland. The substances found were predominantly substituted phenethylamines, cathinones, tryptamines and synthetic cannabinoids, which were identified by appropriate methods prior to submitting the samples for quantification by LC–CLND. The equimolarity and expanded uncertainty of measurement by LC–CLND were on average 95% and 13%, respectively, based on 16 different substances. The median (mean) purity of stimulant/hallucinogenic drug samples seized at the border was 92.9% (87.6%) and in the street 82.0% (64.5%). The corresponding figures for powdery synthetic cannabinoid samples seized at the border and in the street were 99.0% (96.8%) and 90.0% (92.2%), respectively. There was generally only one active drug to be quantified in each sample. Seized herbal samples contained 0.15–9.2% of between one and three components. LC–CLND was found to be suitable for quantification of the nitrogen-containing drugs encountered in the study, showing sufficient N-equimolarity for both stimulant/hallucinogenic drugs and synthetic cannabinoids. The technique possesses great potential as a standard technique in forensic laboratories.

Chemiluminescent Nitrogen Detection (CLND) to Measure Kinetic Aqueous Solubility

Solubility is the dose-limiting property for in vitro studies, and therefore is a critical physicochemical property to measure in drug discovery. Solubility data can be used to guide lead optimization, troubleshoot erratic bioassay results, and identify potential downstream liabilities such as insufficient solubility for bioassays or oral bioavailability. Typically, early in vitro studies are performed using library compounds prepared as dimethylsulfoxide (DMSO) stock solutions, resulting in in vitro test solutions containing DMSO at low concentration (<5% v/v). Since DMSO can affect the apparent solubility, it is desirable to obtain solubility data under conditions mimicking the in vitro study. Kinetic solubility (from DMSO stock solutions) is often preferred over thermodynamic solubility (from dry powder) in early drug discovery. The protocols in this article describe a general procedure for assessing kinetic aqueous solubility of early drug discovery compounds using a miniaturized shake flask method with chemiluminescent nitrogen detection (CLND).

Molecular Characterization of Organic Nitrogen in Cattle Manure Compost by Size-Exclusion HPLC with Chemiluminescent Nitrogen Detection

To characterize organic nitrogen present in cattle manure compost, a hot-water extract of the compost along with an acid-insoluble (humic acid-like) fraction either treated with alkali or laccase or untreated were separated by size-exclusion high-performance liquid chromatography (SE-HPLC). Nitrogen was then detected by chemiluminescent nitrogen detection (CLND), and humic acid-like substances were detected by measuring the absorbance at 420 nm. The acid-insoluble fraction comprised the higher molecular-weight region in the chromatogram of the whole extract, and its chromatogram pattern of CLND was similar to that of the absorbance at 420 nm. Changes in the molecular-weight distribution of the acid-insoluble fraction detected by CLND due to alkaline degradation and laccase polymerization were in agreement with those observed by measuring the absorbance at 420 nm. These results, together with other data, demonstrate that protein and humic acid-like moieties are present in the same molecule in compost organic matter.

Corona-Charged Aerosol Detection: An Analytical Approach

An alternative to other universal detection methods like refractive index (RI), low wavelength or ultraviolet (UV), and evaporative light scattering detection (ELSD), chemiluminescent nitrogen detection is a relatively new method based upon aerosol charging and involves Corona-charged aerosol detection (Corona-CAD). Some reports show that the sensitivity of this method is lower than that of fluorescence detection. Others confirm approximately five times higher sensitivity than conventional UV absorbance detection for selected analytes. This is the reason that Corona-CAD can be widely used for the determination of nonvolatile or semivolatile compounds, including: lipids, oligosaccharides, carbohydrates, proteins, steroids, surfactants, polymers, peptides, and others. The response of Corona-CAD is independent of chemical properties of the analyte. This article reviews applications of Corona-CAD and principles of the aerosol charging method as well as advantages and disadvantages of the method. The modern solution using an ultra detector, which brings charged aerosol detection to UHPLC, is also discussed.

Quantitation method of N ,N ′-disalicylidene-1,2-propanediamine by comprehensive two-dimensional gas chromatography coupled to a nitrogen chemiluminescence detector

Metal deactivator additives (MDAs) have been used for over 60 years to prevent metal catalyzed reactions in petroleum products; a commonly used metal deactivator is N,N'-disalicylidene-1,2-propanediamine. The quantitation of low MDA concentrations in fuels is challenging due to the complexity of the sample matrix. In this work, this difficulty was overcome using GC × GC hyphenated with a nitrogen chemiluminescence detector. The high resolution power of GC × GC avoided co-elution between the MDA and other sample matrix compounds; while the enhanced sensitivity of GC × GC and the use of a nitrogen chemiluminescence detector supplied a high sensitivity and specificity for nitrogen compounds. For the analysis, the MDA additive was derivatized with the silylation agent N,O-bis (trimethylsilyl)trifluoroacetamide at room temperature and its quantitation was based on an external calibration curve; good linear response was obtained in the 1.4-8.6 ppm range.

Analysis of &amp;lt;i&amp;gt;N&amp;lt;/i&amp;gt;-Nitrosamine Migration from Rubber Teats and Soothers

A testing method for N-nitrosamines and N-nitrosatable substances in rubber teats and soothers was modified. N-Nitrosamines are generally analyzed using either a nitrogen chemiluminescence detector (NCD) or a thermal energy analyzer (TEA). However, because few testing laboratories are equipped with these devices, it is difficult to conduct these tests. Therefore, an analysis method for N-nitrosamines using the more widespread gas chromatography-mass spectrometry (GC-MS) method was improved. In addition, EN 12868 was used to prepare the test solutions because of its worldwide use and compliance with EU regulations. Using GC-MS, EN 12868 method targeting ten kinds of N-nitrosamines was modified. The determination limits of the method were 1.0 -1.5 μg/kg for N-nitrosamines and 4 -6 μg/kg for N-nitrosatable substances. Quantification was possible at 1/5 or less and 1/15 or less, respectively, of the regulation values listed in EU Directive 93/11/EEC. In terms of application, there were no problems with the selectivity of the detector. The recoveries were 58% -109% for N-nitrosamines and 59% -102% for N-nitrosatable substances. Screening and verification were possible by measuring the amount of secondary amines in the boiled solution and migration solution.

Characterization of sulfur compounds in whisky by full evaporation dynamic headspace and selectable one-dimensional/two-dimensional retention time locked gas chromatography–mass spectrometry with simultaneous element-specific detection

A method is described for characterization of sulfur compounds in unaged and aged whisky. The method is based on full evaporation dynamic headspace (FEDHS) of 100μL of whisky samples followed by selectable one-dimensional (1D) or two-dimensional (2D) retention-time-locked (RTL) gas chromatography (GC)–mass spectrometry (MS) with simultaneous element-specific detection using a sulfur chemiluminescence detector (SCD) and a nitrogen chemiluminescence detector (NCD). Sequential heart-cuts of the 16 sulfur fractions were used to identify each individual sulfur compound in the unaged whisky. Twenty sulfur compounds were positively identified by a MS library search, linear retention indices (LRI), and formula identification using MS calibration software. Additionally eight formulas were also identified for unknown sulfur compounds. Simultaneous heart-cuts of the 16 sulfur fractions were used to produce the 2D RTL GC-SCD chromatograms for principal component analysis. PCA of the 2D RTL GC-SCD data clearly demonstrated the difference between unaged and aged whisky, as well as two different whisky samples. Fourteen sulfur compounds could be characterized as key sulfur compounds responsible for the changes in the aging step and/or the difference between two kinds of whisky samples. The determined values of the key sulfur compounds were in the range of 0.3–210ngmL−1 (RSD: 0.37–12%, n=3).

Novel simple method for quantitation of nitrogen compounds in middle distillates using solid phase extraction and comprehensive two-dimensional gas chromatography

Nitrogen speciation in crude oil and its fractions has become an important issue due to the undesirable effects of nitrogen compounds during important petroleum refining processes. In this work, a comprehensive two-dimensional gas chromatography method with a nitrogen chemiluminescence detector (GC×GC-NCD) was used for the speciation and quantification of nitrogen compounds in middle distillates. The developed method is based on an extraction of nitrogen compounds from the hydrocarbon matrix followed by their fractionation using solid phase extraction (SPE). Two fractions were collected thus minimizing misidentifications; the first one contained anilines, indoles and carbazoles and the second one contained pyridines, quinolines and acridines. An excellent agreement for total nitrogen content was found between the results obtained with the present method and those from the American Society for Testing Materials (ASTM) method. Good recoveries, repeatability and low detection limits (LOD), in a range from 10 to 20μgL−1, were also achieved.

Determination of volatile nitrosamines in grilled lamb and vegetables using comprehensive gas chromatography – Nitrogen chemiluminescence detection

The grilling of meat may generate dangerous levels of mutagenic and carcinogenic nitrosamines (NAs). Meat and vegetable samples underwent a two-step solid-phase extraction before analysis by comprehensive gas chromatography with a nitrogen chemiluminescence detection system (GCxGC-NCD). The GCxGC-NCD method showed high selectivity, sensitivity and equimolarity in its response to six specific NAs. NA contamination of charcoal-grilled lamb at various stages of cooking and with various fat contents and also charcoal-grilled vegetables were investigated. The grilling of lamb on unready charcoal resulted in the formation of considerable quantities of NAs. Grilling lamb on properly prepared, ready charcoal resulted in an increase in total concentrations of six NAs from 0 to 4.51μgkg−1 over a period of 16min. Increasing the fat content of the grilled lamb from 5% to 20% caused a modest increase in total concentrations of the six investigated NAs from 4.51 to 5.30μgkg−1.

Characterization of Protein-like Fluorophores Released from Lake Phytoplankton on the Basis of Fractionation and Electrophoresis

Three kinds of lake plankton were cultivated, and the properties of protein-like fluorophores released from the plankton were characterized using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The results were compared with those by gel chromatography with a fluorescence detector and three-dimensional excitation-emission matrix (3-DEEM). The concentrated protein-like fluorophores of algal dissolved organic matter (DOM) were successfully separated from the fulvic-like fluorophores, and analyzed using SDS-PAGE. SDS-PAGE analysis revealed that the protein-like fluorescence DOM released from Microcystis aeruginosa consisted of proteins with molecular weights of 17, 37, 50, 75, 150 kDa, and greater than 250 kDa. The results of SDS-PAGE were consistent with those of gel chromatography. Those substances with molecular weights greater than 250 kDa may be a polysaccharide-peptide complex, called peptidoglycan, which is a component of bacterial cell walls. The molecular weights of protein-like fluorescence DOM from Staurastrum dorsidentiferum were determined to be 37 and 50 kDa. For Cryptomonas ovata, its DOM was found to be composed of substances with molecular weights of between 10 and 150 kDa. The results by high-performance size exclusion chromatography with chemiluminescent nitrogen detection (HPSEC/CLND) analysis suggest that the protein-like fluorophores from the plankton might be composed of substances containing organic nitrogen.

Cyclic oligomers in polyamide for food contact material: quantification by HPLC‐CLND and single‐substance calibration

Cyclic oligomers are the major substances migrating from polyamide (PA) food contact materials. However, no commercial standards are available for the quantification of these substances. For the first time the quantification of cyclic oligomers was carried out by HPLC coupled with a chemiluminescence nitrogen detector (CLND) and single‐substance calibration. Cyclic monomer (MW = 226 Da) and dimer (MW = 452 Da) of PA66 were synthesised and equimolar N detection of CLND to synthesised oligomers, caprolactam, 6‐aminohexanoic acid (monomers of PA6) and caffeine (a typical nitrogen calibrant) was proven. Relative response factors (UVD at 210 nm) referring to caprolactam were determined for cyclic PA6 oligomers from dimer to nonamer, using HPLC‐CLND in combination with a UVD. A method for quantification of cyclic oligomer content in PA materials was introduced using HPLC‐CLND analysis and caffeine as a single nitrogen calibrant. The method was applied to the quantification of cyclic PA oligomers in several PA granulates. For two PA6 granulates from different manufacturers markedly different oligomer contents were analysed (19.5 versus 13.4 g kg−1). The elution pattern of cyclic oligomers offers the possibility of identifying the PA type and differentiating between PA copolymers and blends.

Determination of eight tobacco alkaloids in flue-cured tobacco samples by gas chromatography with nitrogen chemiluminescence detection (NCD)

A reliable, sensitive and rapid method for determination of eight alkaloids in flue-cured tobacco by dual-column-dual-detector gas chromatography with nitrogen chemiluminescence detection (GC-NCD) has been established. At first, the extraction effects of several factors such as solid to liquid ratio, extraction time, sodium hydroxide solution volume and sodium hydroxide solution mass fraction on the extraction efficiency were simultaneously investigated using an orthogonal array design (OAD). Then, the NCD was compared to other detectors and showed some unique advantages. The analytical method met the strict quantitative requirement by optimizing chromatographic conditions and using dual-column confirmation. Finally, the performance of the proposed method was tested for the extraction and determination of the eight alkaloids in flue-cured tobacco and satisfactory results were achieved.

Determination of Volatile Nitrosamines in Latex Products by HS-SPME–GC–MS

Nitrosamines which have been detected in various latex products are carcinogens. The method for determination of volatile nitrosamines in latex products was developed using a combination of headspace solid phase micro-extraction (HS-SPME) and gas chromatography–mass spectrometry (GC–MS). A carboxen/polydimethylsiloxane (CAR/PDMS) fiber was used for HS-SPME involving the following variables: (1) agitation conditions, (2) extraction temperature (3) extraction time, and (4) salt concentration. The instrument performances of three detection systems including GC combined thermal energy analyzer, nitrogen chemiluminescence detector and MS were evaluated. The agitation conditions including magnetic stirring and ultrasonication were investigated by the comparison of extraction efficiency of HS-SPME for nitrosamines. Obtained optimal detection conditions of nitrosamines were HS-SPME at 45 °C for 60 min assisted with magnetic stirring and saturated NaCl followed by GC–MS. To evaluate this method performance, the commercial products including eleven latex products (gloves, balloons and condoms) and four liquid silicone nipples were analyzed with the method. The results revealed that the method is suitable for simple and effective determination of nitrosamines in latex products. The advantage of this HS-SPME–GC–MS method is simple treatment, fast analysis, adequate sensitivity and without organic solvent.

Direct separation and detection of biogenic amines by ion-pair liquid chromatography with chemiluminescent nitrogen detector

Analysis of biogenic amines is critical to pharmaceutical and food industry due to their biological importance. For many years, the determination of biogenic amines has relied on high performance liquid chromatography (HPLC) coupling with pre-, on-, or post-column derivatization procedures to enable UV or fluorescent detections. In this study, 14 biogenic amines were separated on a Phenomenex Luna ® Phenyl-Hexyl column by an ion-pair liquid chromatography method using perfluorocarboxylic acids as ion-pair reagents and detected by a chemiluminescent nitrogen detector (CLND). This direct separation and detection HPLC method eliminated the time consuming and cumbersome derivatization procedures. Compared with HPLC–UV (post-column derivatization with ninhydrin) and HPLC-charged aerosol detector (CAD) methods, this HPLC–CLND technique provided narrower peaks, better baselines, and improved separations and detections. Excellent linearity was acquired by CLND for each of the 14 biogenic amines ranging from less than 1 ng to about 1000 ng (on-column weights). The relative response factors determined by this LC–CLND method were proportional to the numbers of nitrogen atoms in each compound, which has been the characteristic of the equimolar determinations by CLND. In addition, a number of samples including beer, dairy beverage, herb tea, and vinegar were analyzed by the LC–CLND method with satisfactory precision and accuracy.