Determination of volatile carbonyl compounds in clean air

Summary An improved analytical procedure has been developed for the detection of formaldehyde, acetaldehyde, acetone and other volatile carbonyls in clean air. For sampling, 2,4-dinitrophenyl-hydrazine (DNPH) coated silica gel cartridges were used. DNPH reacts with carbonyls and forms carbonyl hydrazones which are extracted with acetonitrile and subsequently separated by reversed phase HPLC. Sampling flow rates up to 3.5 l/min were tested. The quantification limit of the complete sampling and analytical procedure is 60 ng carbonyl which corresponds to a mixing ratio of 1 ppbv HCHO in a 45 l air sample taken during a sampling time of 13 min. Carbonyl mixing ratios down to 0.1 ppbv can be determined. The collection efficiency and the elution recovery range between 96 and 100%; the precision is ±5% for HCHO and ±4% for CH₃CHO at mixing ratios of 1 ppbv. This technique can also be applied for the determination of aldehydes and ketones in the aqueous phase, e.g. cloud and fog water. In this case, carbonyls were converted to hydrazones simply by mixing the aqueous sample with an acidified DNPH solution. After 40 min reaction time, the hydrazones were analysed by HPLC. The detection limit was 0.2 mol HCHO/l. Possible interference caused by ozone and NO₂ was eliminated by using KI filters connected in series with the DNPH-coated cartridges. The analytical procedure was tested at a mountain measuring station and proved to be a suitable method for monitoring carbonyl compounds in clean air.     

A Fractional Factorial Design Applied to the Optimization of Microwave- and Ultrasound-Assisted Acid Leaching Methods for Heavy Metals Determination in Sludges by Flame Atomic Absorption Spectrometry

Abstract

The sampling performance of C₁₈ cartridges coated with DNPH has been studied for twenty four C₁-C₉ carbonyls in experiments involving sampling of parts per billion levels of carbonyls in urban air. indoor air and laboratory experiments. The cartridge background carbonyl content in thirty six batches of cartridges averaged 85, 137 and 155 nanogram/cartridge for formaldehyde, acetaldehyde and acetone, respectively, and was below analytical detection for all other carbonyls. Carbonyl-DNPH derivative recovery from the cartridge was complete in the first elution with 2 mL acetonitrile, and this for twenty four carbonyls at concentrations of 0.02–73 μg carbonyl/cartridge. Studies carried out using two cartridges in series showed no breakthrough, for the sixteen carbonyls tested, at concentrations of 0.10–49 μg carbonyl/cartridge and volumes of air sampled = 6–370 L. Average relative standard deviations (RSD) for replicate analyses were 0.20–13.2% for twenty one carbonyls. Average RSD for co-located samples were 0.9–16.2% for eighteen carbonyls. Comparison of RSD for replicates and RSD for co-located samples for thirteen carbonyls indicated that the overall method precision was limited by sampling precision rather than by analytical precision.     

Immobilized 2-(4-hydrazinocarbonylphenyl)-4,5-diphenylimidazole as solid phase luminophore in peroxyoxalate chemiluminescence

A new luminophore for application in peroxyoxalate chemiluminescence is presented. An analogue of the well-known chemiluminescence compound lophine, i.e. 2-(4-hydrazinocarbonylphenyl)-4,5-diphenylimidazole (HCPI), has been covalently immobilized to controlled pore glass and a porous methacrylate resin. By using this reagent in a solid phase detection reactor, sensitive determinations of hydrogen peroxide have been demonstrated. In homogeneous solution HCPI emits poorly as a result of 1,1-oxalyldiimidazole excitation, but when immobilized its efficiency is almost comparable to highly efficient luminophores such as 3-aminofluoranthene. Linearity extends in the single stream flow system over several orders of magnitude with both materials. The limit of detection was 1 nmol/l (10 fmole injected), when using the porous methacrylate support.     

Quenched peroxyoxalate chemiluminescence detection in aqueous liquid chromatographic separations

Several analytes, such as bromide, iodide, sulphite, nitrite, substituted anilines and organosulphur compounds cause quenching of peroxyoxalate chemiluminescence. This phenomenon, quenched peroxyoxalate chemiluminescence, can be used as a method of detection for liquid chromatography. The potential of quenched chemiluminescence is discussed, with special attention give to its compatibility with aqueous separation systems. An immobilized fluorophore, 3-aminofluoranthene on controlled pore glass, is packed in the detector cell. Liquid-state studies show that the influence of both the nature and concentration of the fluorophore is small, which indicates a more complicated mechanism of the chemiluminescence reaction than previously assumed. It is shown that bis(2-nitrophenyl)oxalat is a more suitable oxalate for quenched chemiluminescence detection than bis(2,4,6-trichlorophenyl) oxalate. This is demostrated for ion-chromatography of bromide and iodide and the aqueous reversed-phase separation of organosulphur compounds. Detection limits in the low nanogram and sub-nanogram region are reported for the above compounds. When an electronic inverter was used, calibration curves were linear over a concentration range of 2–3 decades. The method is quite selective and can be applied to relatively complex matrices without sample pretreatment.     

Sampling of Atmospheric Carbonyls with Small DNPH-Coated C18 Cartridges and Liquid Chromatography Analysis with Diode Array Detection

Abstract

Carbonyls in air are sampled using small DNPH-coated C18 cartridges and analyzed by liquid chromatography with diode array detection. Carbonyl structure confirmation is obtained by comparing diode array spectral scans of samples to the uv-visible spectra (190–600 nm) of some 20 carbonyl hydrazones recorded in the CH₃CN—H₂O eluent used for LC analysis. Analytical detection limits are 0.09–3.4 nanograms carbonyl and correspond to 0.14–1.24ppb in 60 L air samples. Accuracy was ±5% as measured for independently prepared hydrazone standards. The precision was 1–5% for multiple injections of hydrazone standards and 2–10% for replicate analysis of indoor and outdoor air samples. Excellent agreement was obtained in an interlaboratory comparison that included hydrazone standards as well as indoor air samples.

Cartridge collection efficiency has been tested over a range of conditions (sampling flow rate, volume of air sampled, presence of co-pollutants including photochemical oxidants) and is >0.95 for monofunctional carbonyls, unsaturated carbonyls, and alpha dicarbonyls. Carbonyl recovery by cartridge elution is >0.99 for all carbonyls tested. Examples of applications are given in the fields of atmospheric chemistry, indoor air pollution in museums, and outdoor air quality.     

Determination of olefinic aldehydes and other volatile carbonyls in air samples by DNPH-coated cartridges and HPLC

Summary The collection of low-boiling olefinic aldehydes on 2,4-dinitrophenylhydrazine (DNPH)-coated adsorbents (silica cartridges and glass denuders) is examined. Concurrent formation of two different hydrazones by both acrolein and crotonaldehyde is reported and discussed. Identification and quantitation of these compounds do not represent a problem in HPLC analysis, because of their separation from other C₃ and C₄ carbonyl derivatives present in airborne sample extracts.     

Determination of aldehydes in fish by high-performance liquid chromatography

A new analytical method to determine trace volatile aldehydes isolated from the headspace of fish meat at room temperature by high-performance liquid chromatography (HPLC) in the form of 2,4-dinitrophenylhydrazone (DNPHo) derivatives has been developed. Aliquots (50 g) of the fish purée were introduced into a 500-mL glass recipient and were purged with N2 for 40 min through two SEP-PAK C18 cartridges (connected in series) coated with an acid solution of 2,4-dinitrophenylhydrazine. The cartridges were then eluted with acetonitrile (2 mL) and the 2,4-DNPHo formed was quantitated by HPLC-UV analysis using a Zorbax C18 column. The isolated compounds from the dynamic headspace sampling of four kinds of fish species were saturated aldehydes, formaldehyde, acetaldehyde, propanal, butanal, pentanal, and hexanal. Under optimized conditions the detection limits of the HPLC method were in the range of 0.75 nmol/g (formaldehyde) to 2.19 nmol/g (hexanal). The calibration curves were linear in the concentration range from 1.3 nmol/mL to 12.5 nmol/mL. Propanal and acetaldehyde were the major carbonyl compounds identified (ranging from 3.9 nmol/g and 10 nmol/g). This study has revealed the widespread occurrence of formaldehyde, acetaldehyde, propanal, butanal, pentanal, and hexanal in fish meat.     

Simultaneous measurements of formaldehyde and ozone in air by annular denuder-HPLC techniques

Summary A denuder sampling method combined with HPLC analysis for the simultaneous determination of formaldehyde and ozone in ambient air is described. It is based on the reactions of CH₂O and O₃ with 2,4-dinitrophenylhydrazine (DNPH) and 4-allyl-2-methoxyphenol (eugenol)_respectively, both acting as coatings of two annular denuders connected in series. Formaldehyde released from the ozonolysis of eugenol is quantitatively collected on a third downstream DNPH-coated denuder. The two DNPH denuders are then extracted and analyzed as hydrazone derivative by HPLC with UV absorbance detection.The stoichiometric factor of the eugenol-ozone reaction was found to be 2.0±0.1 moles of O₃ per mole of CH₂O. The limits of detection are 0.8gm^–3 CH₂O and 3gm^–3 O₃ for 100l air sampled, corresponding to 1-h sampling at 1.7l min^–1.     

Sensitive determination of aliphatic amines in water by high-performance liquid chromatography with chemiluminescence detection

A sensitive method has been developed for liquid chromatographic determination of short aliphatic amines in water samples. Analytes are preconcentrated and dansylated on solid sorbents (C18 solid-phase extraction cartridges). The dansyl derivatives are chromatographed and post-column mixed with peroxyoxalate (TCPO) and H2O2 in order to perform chemiluminescence detection. Optimal results have been obtained using a sample volume of 5 ml. The method has been applied to the quantification or screening of several aliphatic amines: methylamine, ethylamine, butylamine, diethylamine, pentylamine and hexylamine. The screening procedure has been developed including also polyamines (putrescine, cadaverine, spermidine and spermine). The results obtained by using chemiluminescence (CL) detection have been compared with other detection systems (fluorescence and UV). The sensitivity can increase from 3 to 75 times respect UV detection and from 2 to 10 times respect fluorescence detection depending on the amine. The detection limits achieved were between 0.15 and 0.9 microg/l.     

Evaluation of solid-phase microextraction with PDMS for air sampling of gaseous organophosphate flame-retardants and plasticizers

As an inexpensive, simple, and low-solvent consuming extraction technique, the suitability of solid-phase microextraction (SPME) with polydimethylsiloxane (PDMS) sorbent was investigated as a quantitative method for sampling gaseous organophosphate triesters in air. These compounds have become ubiquitous in indoor air, because of their widespread use as additive flame retardants/plasticizers in various indoor materials. Results obtained by sampling these compounds at controlled air concentrations using SPME and active sampling on glass fibre filters were compared to evaluate the method. A constant linear airflow of 10 cm s^–1 over the fibres was applied to increase the extraction rate. For extraction of triethyl phosphate with a 100-m PDMS fibre, equilibrium was achieved after 8 h. The limit of detection was determined to be less than 10 pg m^–3. The PDMS–air partition coefficients, K_fs, for the individual organophosphate triesters were determined to be in the range 5–60×10⁶ at room temperature (22–23°C). Air measurements were performed utilising the determined coefficients for quantification. In samples taken from a lecture room four different airborne organophosphate esters were identified, the most abundant of which was tris(chloropropyl) phosphate, at the comparatively high level of 1.1 g m^–3. The results from SPME and active sampling had comparable repeatability (RSD less than 17%), and the determined concentrations were also similar. The results suggest that the investigated compounds were almost entirely associated with the gaseous phase at the time and place sampled.     

High-performance liquid chromatography with chemiluminescence detection of serum levels of pre-column derivatized fluoropyrimidine compounds

7-(Diethylamino)-3-[4-[iodoacetyl)amino)phenyl]-4-methylcoumarin (DCIA) and 4-(bromomethyl)-7-methoxycoumarin have been evaluated as fluoropyrimidine-derivatizing agents to be detected using peroxyoxalate chemiluminescence with high-performance liquid chromatography. The derivatization procedure required only one step. No chemiluminescence was observed from the bromo derivatives, and the detection limits of fluoropyrimidine compounds derivatized with the iodo compound and detected with peroxyoxalate chemiluminescence were in the low femtomole range.     

Influence of Substituents on Kinetics of the Reaction of Carbonyl Oxides with Ethanol

The reactivity toward EtOH of nine carbonyl oxides (ROO) obtained by the thermolysis of the corresponding diazo compounds (RN₂) is studied by the chemiluminescence method. The reactivity is characterized by the ratio of constants k ^EtOH ₃₃/k ₃₁, where k ^EtOH ₃₃and k ₃₁are the rate constants of the reactions of ROO with EtOH and RN₂, respectively. The negative slope of the Taft correlations ( < 0) indicates the electrophilic character of the reaction of ROO with EtOH. The substituents, electron density acceptors, increase the relative reactivity of the carbonyl oxides.     

Fe-Mediated S–S Bond Cleavage and Its Application in the Synthesis of α-Arylthio Carbonyl Compounds

In the presence of iron dust, diaryl disulfides react with α-bromo carbonyl compounds to obtain α-arylthio carbonyl compounds in good yield at 90 °C under an N₂ atmosphere, using commercial dimethylformamide (DMF) as solvent. The possible reaction mechanism is that the disulfide is reduced by iron dust to give ArSFeSAr and then reacted with α-bromo carbonyl compounds to give product α-arylthio carbonyl compounds and FeBr₂.     

Determination of hydroxy-s-triazines in water using HPLC or GC-MS

Two methods are described for the routine determination of triazine degradation products in water. After solid phase extraction by means of RP-C₁₈ cartridges, the separation and detection were carried out using either HPLC (for hydroxy-atrazine [OHA], hydroxy-simazine [OHS], hydroxy-propazine [OHP], hydroxy-terbutylazine [OHT] and hydroxy-desethylatrazine [OHDEA]) or GC-MS (only for OHA, OHS, OHP and OHT after methylation with diazomethane). The HPLC set-up is described for detecting the hydroxy-triazines, including hydroxy-desisopropylatrazine (OHDIA), hydroxy-desethyldesisopropylatrazine (OHDEDIA) and cyanuric acid (CA). The average recoveries at concentration levels between 50 ng/L and 1 g/L ranged from 35% to 43% for GC-MS (n=5) and from 53% to 75% for HPLC (n=5) with the exception of hydroxy-desethylatrazine which has been recovered with only 21%. Hydroxy-desisopropylatrazine, hydroxy-desethyldesisopropylatrazine and cyanuric acid could not be enriched on RPC₁₈. The determination limit of the investigated compounds has to be set between 90 and 100 ng/L for both methods for OHS, OHA, OHP and OHT.     

A Photochemical Ligation System Enabling Solid-Phase Chemiluminescence Read-Out

The peroxyoxalate chemiluminescence (PO-CL) reaction is among the most powerful and versatile techniques for the detection of hydrogen peroxide (H₂O₂) and has been employed in various biological and chemical applications over the past 50 years. However, its two-component nature (peroxyoxalate and fluorophore) limits its use. This contribution introduces an innovative and versatile photochemical platform technology for the synthesis of inherently fluorescent PO probes by exploiting the nitrile imine-mediated tetrazole-ene cycloaddition (NITEC) reaction. In the presence of hydrogen peroxide, the pioneered “2-in-1” molecule emits either yellow or blue light, depending on tetrazole (Tz) structure. Even in the absence of base, the emitted light remains visible and H₂O₂ could be detected in the nanomolar range. Critically, the PO-Tz can be readily incorporated into polymeric materials. As a first application of this promising material, a tailor-made PO-Tz is grafted on poly(divinylbenzene) (PDVB) particles to enable solid-phase chemiluminescence on microspheres.     

Evaluation of pyrimido[5,4-d]pyrimidine derivatives as peroxyoxalate chemiluminescence reagents using a flow injection system

Eighteen kinds of pyrimido[5,4-d]pyrimidines together with several commercially available fluorescent compounds such as perylene, Rhodamine B, etc., were evaluated as the reagents for a peroxyoxalate chemiluminescence (CL) detection system by using a flow injection method. The peroxyoxalate CL reaction employed consists of bis(2,4,6-trichlorophenyl)oxalate, hydrogen peroxide, triethylamine, and a fluorophore. Under the conditions used, 2,6-bis[di-(2-hydroxyethyl)amino]-4,8- dipiperidinopyrimido[5,4-d]pyrimidine (Dipyridamole) and 2,4,6,8-tetrathiomorpholinopyrimido[5,4-d]pyrimidine (1i) gave very intense chemiluminescence intensities which were larger than those of any other commercially available fluorescent compounds tested (e.g., 10 times larger than that of perylene).     

An improved method for the analysis of volatile polyfluorinated alkyl substances in environmental air samples

This article describes the optimisation and validation of an analytical method for the determination of volatile polyfluorinated alkyl substances (PFAS) in environmental air samples. Airborne fluorinated telomer alcohols (FTOHs) as well as fluorinated sulfonamides and sulfonamidoethanols (FOSAs/FOSEs) were enriched on glass-fibre filters (GFFs), polyurethane foams (PUFs) and XAD-2 resin by means of high-volume air samplers. Sensitive and selective determination was performed using gas chromatography/chemical ionisation–mass spectrometry (GC/CI–MS). Five mass-labelled internal standard (IS) compounds were applied to ensure the accuracy of the analytical results. No major blank problems were encountered. Recovery experiments were performed, showing losses of the most volatile compounds during extraction and extract concentration as well as strong signal enhancement for FOSEs due to matrix effects. Breakthrough experiments revealed losses of the most volatile FTOHs during sampling, while FOSAs/FOSEs were quantitatively retained. Both analyte losses and matrix effects could be remediated by application of adequate mass-labelled IS. Method quantification limits (MQLs) of the optimised method ranged from 0.2 to 2.5 pg/m³ for individual target compounds. As part of the method validation, an interlaboratory comparison of instrumental quantification methods was conducted. The applicability of the method was demonstrated by means of environmental air samples from an urban and a rural location in Northern Germany. Figure High-volume air sampling of volatile polyfluorinated alkyl substances using glass fibre filters and PUF/XAD-2 cartridges at a background monitoring site (Waldhof, Germany)     

High performance liquid chromatography post-column chemiluminescence determination of sulfonamide residues in milk at low concentration levels using bis[4-nitro-2-(3,6,9-trioxadecyloxycarbonyl)phenyl] oxalate as chemiluminescent reagent

The determination of seven sulfonamides by means of HPLC with chemiluminescence detection is proposed for the first time. The analytes are derivatized with fluorescamine, separated and subsequently they participate in the post-column chemiluminescence (CL) peroxyoxalate system using imidazole as a catalyst. Among the different peroxyoxalates tested, bis[4-nitro-2-(3,6,9-trioxadecyloxycarbonyl)phenyl] oxalate provides higher sensitivities and stabilities, avoiding precipitation problems. A rigorous optimization of the significant variables by means of experimental designs has been developed in order to reconcile the chromatographic conditions with the CL reaction. The method provides detection limits in the low microgl(-1) range and has been satisfactorily applied to the analysis of spiked raw milk samples.     

Determination of formaldehyde and acetaldehyde in air by HPLC with fluorescence detection

Summary Sensitive detection of atmospheric formaldehyde and acetaldehyde can be achieved by use of silica-gel cartridges impregnated with 2-diphenylacetyl-1,3-indandione-1-hydrazone (DAIH) to form fluorescent DAI hydrazones. The hydrazones are extracted with acetonitrile and separated by reversed-phase HPLC with fluorimetric detection. The low detection limits achieved (0.25 ppb CH₂O or CH₃CHO for sampling periods of 1 h) means that the sensitivity of the method is better than that of the classical dinitrophenylhydrazine (DNPH) method. Several experimental conditions, such as collection and reaction efficiency, interference by ozone and storage stability of blank and sampled cartridges have been investigated. There were no significant differences between ambient concentrations of CH₂O and CH₃CHO measured concurrently with the DAIH and DNPH techniques (10–20% in the 0–5 ppb range).