Determination of morpholine in air by derivatisation with 1-naphthylisothiocyanate and HPLC analysis

A method for the determination of morpholine in air was developed. Samples were collected with adsorbent tubes containing XAD-2 resin coated with 1-naphthylisothiocyanate (NIT). The thiourea derivative formed was subsequently desorbed with acetonitrile and analysed by HPLC with UV detection. The recovery after gas phase spiking with morpholine (2.2-1570 micrograms) was 91% (86-100%) with a relative standard deviation of 5.5%. No effect on recovery from relative humidity or amount of morpholine was seen. The lowest level tested corresponded to 7 mg m-3 (1/10 threshold limit value) for a 15 min sampling period with a sampling rate of 20 ml min-1. Exposed NIT-coated XAD-2 tubes were stable at room temperature for at least 2 weeks.     

Correlations between air levels of hexahydrophthalic anhydride (HHPA) and HHPA-adducted albumin tryptic peptides in nasal lavage fluid from experimentally exposed volunteers

Organic acid anhydrides (OAAs) are low molecular weight, reactive compounds extensively used in industry. Exposure to these compounds may lead to allergic symptoms such as rhinitis and asthma. It is important to develop better and more informative methods for assessment of exposure to OAAs. The aim of this study was to develop a method for analysis of specific hexahydrophthalic anhydride (HHPA)-adducted tryptic peptides of human serum albumin (HSA) in nasal lavage (NAL). Furthermore, these peptides were evaluated as biomarkers of exposure. The proteins in the NAL samples were reduced, alkylated and digested with trypsin and the obtained peptides were analyzed using liquid chromatography/tandem mass spectrometry. The total amount of hydrolyzable HHPA in an HHPA-HSA conjugate was used for calibration. A deuterium-labeled HHPA-HSA conjugate was used as internal standard. Five volunteers were exposed to 10, 40 and 80 microg/m3 of HHPA in an exposure chamber and NAL samples were collected before and after exposure. Acceptable precisions of the assay at 13-14% were found for three adducted peptides. The mean levels of these three peptides for the five subjects ranged between 5-22, 15-75 and 33-125 pmol/mL NAL for the exposures at 10, 40 and 80 microg/m3, respectively. High correlations between air levels and the measured peptides were found on an individual basis but there were large inter-individual differences ranging between 63 and 110% for the three peptides. The large differences remained after protein adjustments. It was possible to detect exposures below 10 microg/m3 with the method. Thus, these adducted peptides may be used as biomarkers of exposure, which may better estimate the risk than previous biomarkers developed for OAAs.     

Application of graphene nanoplatelets silica composite,prepared by sol–gel technology,as a novel sorbent in two microextraction techniques

In this study, the application of a novel nanomaterial composite was investigated in two microextraction techniques of solid‐phase microextraction and a needle trap device in a variety of sampling conditions. The optimum sampling temperature and relative humidity were 10°C and 20%, respectively, for both techniques with two sorbents of graphene/silica composite and polydimethyl siloxane. The two microextraction techniques with the proposed sorbent showed recoveries of 95.2 and 94.6% after 7 days. For the needle trap device the optimums desorption time and temperature were 3 min at 290°C and for SPME these measures were 1 and 1.5 min at 240–250°C for the graphene/silica composite and polydimethyl siloxane, respectively. The relative standard division obtained in inter‐ and intra‐day comparative studies were 3.3–14.3 and 5.1–25.4, respectively. For four sample the limit of detection was 0.021–0.25 ng/mL, and the limit of quantitation was 0.08–0.75 ng/mL. The results show that the graphene/silica composite is an appropriate extraction media for both techniques. Combining an appropriate sorbent with microextraction techniques, and using these in conjunction with a sensitive analytical instrument can introduce a strong method for sampling and analysis of occupational and environmental pollutants in air.     

Analysis of amides in the air by sampling with SPME and detection by GC-FID

This paper proposes a solid-phase microextraction (SPME) method for the passive sampling and determination of N,N-dimethylacetamide (DMA) and N,N-dimethylformamide (DMF) in air by capillary GC with flame ionization detection. The optimized conditions for SPME method were grab sampling, polydimethylsiloxane/divinylbenzene fiber, extraction for 90 min at 25 +/- 2 degrees C, desorption for 3 min at 220 degrees C, and relative humidity 45 +/- 2%. Under these conditions, the method presented good linearity (R = 0.996), repeatability (%RSD 2.79 and 9.85 for DMF and DMA, respectively), and detection limit (0.021 and 0.024 mg/m3 for DMF and DMA, respectively).     

气体中合成辣椒素的检测方法研究

研究了气体中合成辣椒素(OC)的固体吸附-气相色谱检测方法,建立了气体样品经XAD-2吸附后于CH_2Cl_2溶液中解析,采用毛细管色谱柱分离,FTD检测器进行检测的技术途径.色谱柱:HP-5;载气:高纯氮气(1.2 mL/min);进样口温度:250℃;检测器温度:280℃;程序升温:初始温度180℃,保持0.5 min后以30℃/min的速率升至250℃保持5 min;对影响样品采集和检测的条件进行了选择研究,方法平均回收率为91.5%;平均相对标准偏差为3.2%(n=6);对气态OC的最低检出浓度为10 μg/m~3;在5.0～1000.0 μg/mL范围内有良好的线形关系(r=0.9996).     

Synthesis and application of imprinted polyvinylimidazole-silica hybrid copolymer for Pb2+ determination by flow-injection thermospray flame furnace atomic absorption spectrometry

A novel ion imprinted polyvinylimidazole-silica hybrid copolymer (IIHC) was synthesized and used as a selective solid sorbent for Pb(2+) ions preconcentration using an on-line solid phase extraction (SPE) system coupled to TS-FF-AAS. The ionic hybrid sorbent was prepared using 1-vinylimidazole and 3-(trimethoxysilyl)propylmethacrylate as monomers, Pb(2+) ions as template, tetraethoxysilane as reticulating agent and 2,2'-azobis-isobutyronitrile as initiator. The best on-line SPE conditions concerning sorption behavior, including sample pH (6.46), buffer concentration (9.0 mmol L(-1)), eluent (HNO(3)) concentration (0.5 mol L(-1)) and preconcentration flow rate (4.0 mL min(-1)), were optimized by means of full factorial design and Doehlert matrix. The analytical curve ranged from 2.5 to 65.0 μg L(-1) (r=0.999) with limit of detection of 0.75 μg L(-1); the precision (repeatability) calculated as relative standard deviation (n=10) was 5.0 and 3.6% for Pb(2+) concentration of 10.0 and 60.0 μg L(-1), respectively. From on-line breakthrough curve, column capacity was 3.5 mg g(-1). Preconcentration factor (PF), consumptive index (CI) and concentration efficiency (CE) were 128.0, 0.16 mL and 25.6 min(-1), respectively. The selective performance of the sorbent, based on relative selectivity coefficient, was compared to NIC (non imprinted copolymer) for the binary mixture Pb(2+)/Cd(2+), Pb(2+)/Cu(2+) and Pb(2+)/Zn(2+). The results showed that ion imprinted polyvinylimidazole-silica hybrid polymer had higher selectivity for Pb(2+) than NIC at 64.9, 16.0 and 8.8 folds. The developed method was successfully applied for highly sensitive and selective Pb(2+) determination in different kinds of water samples, parenteral solutions and urine. Accuracy was also assessed by analyzing certified reference fish protein (DORM-3) and marine sediment (MESS-3 and PACS-2) with satisfactory results.     

Evaluation of an immunoaffinity extraction column for enrichment of adducts between human serum albumin and hexahydrophthalic anhydride in plasma

An immunoaffinity extraction (IAE) column was prepared for extraction of adducts between human serum albumin (HSA) and hexahydrophthalic anhydride (HHPA). HHPA is a strong sensitizer inducing immunoglobulin E antibodies in vivo. Polyclonal antibodies from a rabbit immunized with keyhole limpet hemocyananin-HHPA conjugate were purified using a Protein A Sepharose gel. To obtain antibodies with optimal affinity towards HHPA-protein adducts, HHPA-specific antibodies were selected using an N-hydroxysuccinimide-Sepharose column coupled with albumin-HHPA conjugate. Antibodies eluted from this column at pH 2.2 were selected to prepare the IAE column. The column was evaluated using 2 mL plasma spiked with HSA-HHPA conjugate. The column was eluted with glycine buffer at pH 2.0. The conjugates in the eluate were hydrolyzed to the corresponding HHP acid and quantified by mass spectrometry. The average recovery of HHPA adducts in 11 experiments was 68% with a coefficient of variation (CV) of 7%. The column's capacity to bind protein-HHPA adducts was found to be linear in the range of 0.15-1.2 nmol conjugate. The evaluation showed that the IAE column had adequate affinity towards the HHPA adducts and that the adducts could be extracted with good recovery and precision from a large volume of plasma.     

Method for the biological monitoring of hexahydrophthalic anhydride by the determination of hexahydrophthalic acid in urine using gas chromatography and selected-ion monitoring.

A method for the determination of hexahydrophthalic acid, a metabolite of hexahydrophthalic anhydride, in human urine has been developed. The urine was worked-up by liquid-solid extraction, esterified with boron trifluoride-methanol, and analysed by capillary gas chromatography and selected-ion monitoring. Hexadeuterium-labelled hexahydrophthalic acid was used as the internal standard. The precision was 4% at 0.7 microgram/ml and 5% at 0.07 microgram/ml. The recovery of the acid for the overall method was 101% at 0.07 micrograms/ml of urine (with a coefficient of variation of 4%) and 95% at 0.7 microgram/ml (coefficient of variation 2%). The limit of detection was 20 ng/ml urine.     

Determination of amoxicillin in trout by liquid chromatography with UV detection after derivatization

A liquid chromatographic (LC) method based on solid-phase extraction was developed for determination of amoxicillin in muscle tissue of rainbow trout. The compound was extracted in an aqueous solution by precipitation of organic material with a mixture of sulfuric acid and sodium tungstate. The extract was processed by solid-phase extraction on an end-capped phenyl sorbent, and concentrated on a divinylbenzene-co-N-vinylpyrrolidone polymeric sorbent. The extract was derivatized and analyzed by reversed-phase gradient LC on a C18 column with UV detection at 323 nm. The method detection limit was 2.9 micrograms/kg. Mean recovery in muscle was 80.5% (range 10-200 micrograms/kg). The method was applied to fillets from trout offered feed containing amoxicillin in an aquaculture pilot plant. Amoxicillin was detected in muscle tissue shortly after administration but not 3 weeks later. The relative repeatability standard deviation for incurred residues in muscle tissue was 6.4% (range 11-143 micrograms/kg).     

Solid phase extraction and simultaneous high performance liquid chromatographic determination of antipyrine and its major metabolites in urine.

A reversed phase gradient high performance liquid chromatographic method utilizing solid phase extraction has been described for the simultaneous determination of antipyrine (AP), 4-hydroxyantipyrine (4-OHAP), norantipyrine (NorAP) and 3-hydroxymethylantipyrine (3-OHMAP) in human urine after hydrolysis with beta-glucuronidase. The C-18 sorbent cartridges were conditioned and urine samples were applied, washed with 1 x 4 mL of phosphate buffer and eluted with 3 x 100 microL of 20% v/v of acetonitrile in methylene chloride. The eluent was evaporated to dryness, reconstituted in 100 microL phosphate buffer and injected. The calibration ranges were 2.0-250 micrograms/mL (AP), 2.5-250 micrograms/mL (NorAP), 2.0-250 micrograms/mL (3-OHMAP) and 5.0-500 micrograms/mL (4-OHAP) with regression coefficients of 0.998 or greater. Specificity was indicated by the absence of interferences in chromatogram of blank urine from normal as well as cirrhotic patients. The average recovery was 86.7% for AP, 90.5% for NorAP, 85.2% for 4-OHAP and 74.2% for 3-OHMAP. The within-assay precision as indicated by the reproducibility of the assayed spiked urine was less than 9% in all cases and the between-assay precision was less than 12%. The method was applied to studies on antipyrine metabolism in stable cirrhotic patients. Following administration of a single oral dose of about 1000 mg to nine stable cirrhotic patients and eight age-matched healthy volunteers, the cumulative account excreted in the urine up to 48 h for AP and the three metabolites was comparable to other literature reports.     

Diffusive sampling of methylene chloride with solid phase microextraction

This study examined the characteristics of a solid phase microextraction (SPME) assembly as a passive sampler to determine the short-term exposure level (STEL) of methylene chloride. Two types of SPME fibers and six sampling-related factors were chosen and nested in an L(18) Taguchi's orthogonal array. Samples were thermally desorpted and analyzed by gas chromatograph equipped with an electron capture detector (GC/ECD). The use of 85-mum Carboxen/polydimethylsiloxane (Car/PDMS) fibers resulted in greater adsorbed mass, which was highly correlated with the product of concentration and sampling time (r>0.99, p<0.0001), than 85-microm polyacrylate fibers. The sampling rate (SR) of the 85-microm Carboxen/polydimethylsiloxane fibers was not significantly affected by variations in relative humidity (0-80%) and coexistent toluene (none to 100 ppm). Variance of sampling rate was predominantly attributed to the diffusive path length (86.4%) and sampling time (5.7%). With diffusive paths of 3, 10 and 15 mm, the sampling rates of 85-microm Carboxen/polydimethylsiloxane fibers for methylene chloride were 1.4 x 10(-2), 7.7 x 10(-3) and 5.1 x1 0(-3)mL min(-1), respectively. The measured sampling rates were greater than the theoretical values, and decreased with increment of sampling time until they came to constant.     

Determination of glycerol in alcoholic beverages using packed bed reactors with immobilized glycerol dehydrogenase and an amperometric FIA system

A flow injection analysis system incorporating amperometric detection and enzyme reactor for glycerol determination in alcoholic beverages is described. The reactor is based on the glycerol dehydrogenase system, and the enzyme was immobilized through chemical modification on several supporting materials such as aminopropyl and isothiocyanate controlled pore glass, aminopolystyrene resin and m-aminobenzyloxymethyl cellulose. NADH, the product of the enzymatic reaction, was monitored amperometrically with a three-electrode wall-jet type flow through cell, at + 0.5 V vs. Ag/AgCl. The method was evaluated in the presence or absence of potassium and the following linear dynamic ranges were found: 2 x 10(-5) -2 x 10(-4) mol l(-1) and 4 x 10(-5) -4 x 10(-4) mol l(-1), respectively. The interference effects of various compounds were also studied. The relative standard deviation was found to be better than 1.0% (n = 6). The reactors are stable for over a period of 3 months and after about 2500 injections. Under optimum working conditions the sampling frequency was 30 samples h(-1). The successive application of the method was confirmed by comparison with a reference method. The mean relative error is 2.2% and the recovery 95-102%.     

Preconcentration of lead complexed with O,O-diethyl-dithiophosphate by column solid-phase extraction using different sorbents in a flow injection system coupled to a flame atomic absorption spectrometer

A comparative study of C(18) immobilized on silica, activated carbon and a polyurethane foam, as sorbents for Pb complexed with O,O-diethyl-dithiophosphate in a flow injection preconcentration system is reported. The complex was formed in 1.0 M HCl medium and processed in a simple system using a peristaltic pump, a manual injector-commutator and a mini-column filled with the sorbent. Using ethanol as eluent, the richest 150-mul fraction was collected and measured (after discarding 150, 200 and 0 mul for the activated carbon, foam and C(18), respectively) by flame atomic absorption spectrometry. The optimum concentration of the complexing agent was 0.05% m/v for C(18) and 0.2% m/v for the activated carbon and the polyurethane foam. The best sample loading flow rate was 4.0 ml min(-1) for the activated carbon and 2.0 ml min(-1) for C(18) and the polyurethane foam, while the best elution flow rate was 1.0 ml min(-1) (activated carbon) and 0.6 ml min(-1) (C(18) and foam). It was found that beyond a certain loading sample volume, for a constant analyte mass, the signal decreased. The maximum loading sample volume, for a constant analyte mass, before the signal started to decrease, was 50 ml for the activated carbon and 150 ml for the other materials. By processing 25 ml, the enrichment factors were 23, 55 and 166 for the activated carbon, foam and C(18), respectively. The best limit of detection (3sigma) was 0.3 mug l(-1) for the C(18) (1.2 mug l(-1) for the foam and 3 mug l(-1) for the activated carbon). As shown, the C(18) has a much superior retention performance in comparison to the other two materials.     

A solid molecular basket sorbent for CO2 capture from gas streams with low CO2 concentration under ambient conditions

In this paper, a solid molecular basket sorbent, 50 wt% PEI/SBA-15, was studied for CO(2) capture from gas streams with low CO(2) concentration under ambient conditions. The sorbent was able to effectively and selectively capture CO(2) from a gas stream containing 1% CO(2) at 75 °C, with a breakthrough and saturation capacity of 63.1 and 66.7 mg g(-1), respectively, and a selectivity of 14 for CO(2)/CO and 185 for CO(2)/Ar. The sorption performance of the sorbent was influenced greatly by the operating temperature. The CO(2)-TPD study showed that the sorbent could be regenerated under mild conditions (50-110 °C) and was stable in the cyclic operations for at least 20 cycles. Furthermore, the possibility for CO(2) capture from air using the PEI/SBA-15 sorbent was studied by FTIR and proved by TPD. A capacity of 22.5 mg g(-1) was attained at 75 °C via a TPD method using a simulated air with 400 ppmv CO(2) in N(2).     

Determination of 2-naphthylamine in urine by a novel reversed-phase high-performance liquid chromatography method.

A high-performance liquid chromatographic method for the determination of 2-naphthylamine in urine using fluorescence detection was developed. The method validation analysis showed the method to be in analytical control, i.e. the distribution of the difference between the observed and true values of the method evaluation samples did not deviate significantly from the normal distribution. The recovery of the method was 85%. The entire run time of chromatography was 10 min using isocratic elution (acetonitrile-water, 35:65), and the retention time for 2-naphthylamine was 5.8 min. The relative short time of analysis in combination with the low limit of detection (0.272 nmol/l) makes the method potentially applicable for surveillance of occupational and environmental exposure to 2-nitronaphthalene. The developed method is presently used for measurement of 2-naphthylamine in urine samples from workers employed at factories, characterized by a low airborne exposure level of polycyclic aromatic hydrocarbons, i.e. in general less than 25 micrograms/m3. The urine samples of exposed workers (n = 95) showed a 2-naphthylamine range of up to 9.4 nmol/l, whereas unexposed control individuals (n = 114) showed a range of up to 0.87 nmol/l.     

Determination of trace amounts of Pd(II) ions in water and road dust samples by flame atomic absorption spectrometry after preconcentration on modified organo nanoclay

This paper describes the application of organo nanoclay, an easily prepared and stable solid sorbent, to the preconcentration of trace amounts of palladium ions in aqueous solution. The organo nanoclay was prepared by adding tetradecyldimethylbenzylamonium chloride onto montmorillonite, which was then modified with 1-(2-pyridylazo)-2-naphthol. The modified nanoclay was used as a solid sorbent for separation and preconcentration of trace amounts of Pd(II) ions, and a simple, sensitive, and economical method was developed for determination of trace amounts of palladium by flame atomic absorption spectrometry. The sorption of Pd(II) ions was quantitative in the pH range of 1.5-5.0, whereas quantitative desorption occurred with 5.0 mL of a mixture containing 1.0 M thiourea and 1.0 M HCl. The RSD of the method was +/- 2.1% (n = 10; concn = 0.5 microg/mL), and the LOD (3sigma(bl); sigma = SD and bl = blank) was 0.1 ng/mL. The calibration curve was linear for concentrations of 0.5-8.0 microg/mL in the initial solution, and the preconcentration factor was 140. The maximum capacity of the sorbent was 2.4 mg Pd(II)/g modified organo nanoclay. The influences of the experimental parameters, including sample pH, eluant volume, eluant type, sample volume, and interfering ions, on the recoveries of the palladium ion were investigated. The proposed method was applied to the preconcentration and determination of palladium in different samples.     

Matrix solid-phase dispersion extraction of carbadox and olaquindox in feed followed by hydrophilic interaction ultra-high-pressure liquid chromatographic analysis

A new method involving matrix solid-phase dispersion (MSPD) extraction and hydrophilic interaction ultra-high-pressure liquid chromatography (HILIC-UHPLC) with photodiode array detection was developed for the determination of carbadox and olaquindox in feed. Separation of carbadox and olaquindox was achieved within 1 min on the 1.7 microm Acquity UPLC BEH HILIC column by using isocratic elution with a mobile phase consisting of 10 mmol L(-1) ammonium acetate in acetonitrile-water (95:5, v/v) at a flow rate of 0.5 mL min(-1). Optimization of MSPD extraction parameters, such as type of solid sorbent and elution solvent were carried out. Optimal conditions selected for MSPD extraction were: 0.25 g of feed sample, 0.5 g of octadecylsilica as solid sorbent and 10 mL of acetonitrile-methanol (8:2, v/v) as eluting solvent. Both analytes provided average recoveries from spiked feed samples ranging from 89.1 to 98.4% with relative standard deviations less than 10%. Obtained performance characteristics are comparable to those achieved by liquid-liquid extraction-HPLC with the advantages of being simpler and significantly faster.     

Validation of a diffusive sampling method for airborne low-molecular isocyanates using 4-nitro-7-piperazinobenzo-2-oxa-1,3-diazole-impregnated filters and liquid chromatography-tandem mass spectrometry

A diffusive sampling method for the determination of low-molecular isocyanates as their 4-nitro-7-piperazinobenzo-2-oxa-1,3-diazole (NBDPZ) derivatives using tandem mass spectrometry (MS/MS) after atmospheric pressure chemical ionisation (APCI) is presented. Isocyanic acid (ICA), methyl isocyanate (MIC), ethyl isocyanate (EIC) and phenyl isocyanate (PhIC) are collected on NBDPZ-impregnated polystyrene divinyl benzene (SDB) filter tapes. The method was validated for MIC, EIC and PhIC for concentrations between 0.5 and 50 ppb at relative humidity (RH) conditions from 10 up to 90%. Validation was carried out by active sampling using 1-(2-methoxyphenyl)piperazine (2-MP) as derivatising agent. Sampling periods applied were between 15 min and more than 8 h. The sampling rates were determined to be 21.0 mL/min for MIC with a relative standard deviation (RSD) of 9.0% for 184 samplers, 15.6 mL/min for EIC (RSD 11.6%; N = 154) and 11.5 mL/min for PhIC (RSD 8.4%; N = 87). The limits of quantification were 1.4 ppb for MIC and 1.3 ppb for EIC and PhIC applying 15 min sampling periods. Owing to high background signals, isocyanic acid could only be determined when it was present in concentrations in the high ppb range.     

Kinetics of carbon dioxide absorption from air in a flow reactor with a fixed bed of K<Subscript>2</Subscript>CO<Subscript>3</Subscript>-based sorbent

Sorption of carbon dioxide from air in a flow reactor with a bulky fixed bed of the K₂CO₃/Al₂O₃ composite sorbent was studied. The dynamic sorption capacity of the material was shown to depend on the relative humidity of the inlet air. A numerical model was constructed for evaluating the profile of СО₂ concentration in the layer and kinetic curves of CO₂ breakthrough at the outlet of the reactor. The results of simulation allowed us to adequately describe the experimental kinetic curves at 20–40% humidity.     

Determination of airborne methyl isocyanate as dibutylamine or 1-(2-methoxyphenyl)piperazine derivatives by liquid and gas chromatography

The usefulness of a glass fibre filter method to collect airborne methyl isocyanate (MIC) was studied in laboratory experiments and in a workplace during manufacture of mineral wool insulation material. Filter collection was based on derivatisation in situ with 1-(2-methoxyphenyl)piperazine (2MP). 2MP impinger sampling was also evaluated in the workplace. Impinger sampling with dibutylamine (DBA) was used as an independent method. The samples were analysed by liquid and gas chromatography using various detection techniques: mass spectrometry, ultraviolet and electrochemical detection (LC-MS, LC-UV, LC-EchD and GC-MS). The sampling efficiency of 2MP filters for MIC varied with the origin of the glass fibre filter. Two Whatman filters (diameter 25 mm) with altogether 21 mumol of 2MP collected 100% of 9.8 micrograms of MIC during 30 min at an airflow rate of 1 l min-1. The workplace measurements were performed at two concentration levels, 0.003 and 0.09 mg m-3. The theoretical amounts of derivatisation reagent were 42 mumol (2MP filter), 52 mumol (2MP impinger) and 100 mumol (DBA). MIC concentrations were 20% lower by the 2MP methods compared with the DBA method (statistically significant difference). Breakthrough was 6% for the DBA method and 9% for the 2MP impinger method. To trap both MIC and isocyanic acid, which was also present in the workplace samples, a tenfold molar amount of 2MP reagent was used. The precision of sample preparation, expressed as relative standard deviation, was 3.5% (0.17 microgram ml-1, n = 6). The precision of sampling in the workplace was 15% (0.002 mg m-3, n = 6). The limit of quantification was 0.0006 mg m-3 for 30 l of air by the 2MP impinger method and 0.03-0.05 mg m-3 by the 2MP filter method. Hence, airborne MIC can be determined using 2MP as derivatisation reagent. Impinger sampling is preferable when low concentration levels are expected.