Simple and rapid determination of sulfonamides in milk using Ether-type column liquid chromatography

A simplified and rapid determining/identifying method for residual sulfonamides (SAs) in milk by using Ether-type stationary phase, which made in our lab, was presented. The target analytes were extracted by mixing with ethanol-acetic acid (97:3, v/v) followed by centrifugation. The procedure used a Ether-type C8 column, isocratic elution with acetonitrile-water (5:95, v/v), and a photo-diode array detector. The linear range of determination was 50-10,000 μg/L for sulfanilamide and 100-10,000 μg/L for sulfadiazine, sulfamerazine, sulfamethazine. Average recoveries of four SAs (spiked 0.5, 1.0 and 1.5 μg/mL) ranged from 80.1% to 87.6%, with relative standard deviations between 3.4% and 5.8%. The total time and solvent required for the analysis of one sample were <15 min and <1.0 mL of ethanol and 0.6 mL of acetonitrile, respectively. The developed procedure was nearly harmless to the human and environment.     

In situ continuous derivatization/pre-concentration of carbonyl compounds with 2,4-dinitrophenylhydrazine in aqueous samples by solid-phase extraction: Application to liquid chromatography determination of aldehydes

A rapid and straightforward continuous solid-phase extraction system has been developed for in situ derivatization and pre-concentration of carbonyl compounds in aqueous samples. Initially 2,4-dinitrophenylhydrazine, the derivatizing agent, was adsorbed on a C₁₈ mini-column and then 15-ml of sample were continuously aspirated into the flow system, where the derivatization and pre-concentration of the analytes (low-molecular mass aldehydes) were performed simultaneously. Following elution, 20 μl of the extract were injected into a LC-DAD system, in which hydrazones were successfully separated in 12 min on a RP-C₁₈ column using a linear gradient mobile phase of acetonitrile-water of 60-100% acetonitrile for 8 min, flowing at 0.5 ml/min. The whole analytical process can be accomplished within ca. 35 min. Under optimum conditions, limits of detection were obtained between 0.3 and 1.0 μg/l and RSDs (inter-day precision) from 1.2 to 4.6%. Finally, some applications on water samples are presented with recoveries ranged from 95.8 to 99.4%.     

Determination of 19 sulfonamides residues in pork samples by combining QuEChERS with dispersive liquid–liquid microextraction followed by UHPLC–MS/MS

A new simple and rapid pretreatment method for simultaneous determination of 19 sulfonamides in pork samples was developed through combining the QuEChERS method with dispersive liquid–liquid microextraction followed by ultra‐high performance liquid chromatography with tandem mass spectrometry. The sample preparation involves extraction/partitioning with QuEChERS method followed by dispersive liquid–liquid microextraction using tetrachloroethane as extractive solvent and the acetonitrile extract as dispersive solvent that obtained by QuEChERS. The enriched tetrachloroethane organic phase by dispersive liquid–liquid microextraction was evaporated, reconstituted with 100 μL acetonitrile/water (1:9 v/v) and injected into an ultra‐high performance liquid chromatography with a mobile phase composed of acetonitrile and 0.1% v/v formic acid under gradient elution and separated using a BHE C₁₈ column. Various parameters affecting the extraction efficiency were investigated. Matrix‐matched calibration curves were established. Good linear relationships were obtained for all analytes in a range of 2.0–100 μg/kg and the limits of detection were 0.04–0.49 μg/kg. Average recoveries at three spiking levels were in the range of 78.3–106.1% with relative standard deviations less than 12.7% (n = 6). The developed method was successfully applied to determine sulfonamide residues in pork samples.     

Trace determination of sulfonamides residues in meat with a combination of solid-phase microextraction and liquid chromatography-mass spectrometry

An integrated method of combining solid-phase microextraction (SPME) with liquid chromatography-mass spectrometry (LC-MS) was evaluated for determination trace amount of sulfonamides in meat products. Eight commonly used sulfonamides, sulfadiazine (SDZ), sulfathiazole (STZ), sulfamerazine (SMR), sulfamethazine (SMT), sulfamonomethoxine (SMMX), sulfamethoxazole (SMXZ), sulfaquinoxaline (SQX) and sulfadimethoxine (SDMX), were investigated in this study. Chromatography was performed on a C₁₈ reversed-phase column using an isocratic acetonitrile in water as the mobile phase. Fiber coated with a 65 μm thickness of polydimethylsiloxane/divinylbenzene (PDMS/DVB) was used to extract sulfonamides at optimum conditions. Analytes were desorbed with static desorption in an SPME-HPLC desorbed chamber for 15 min and then determined by LC-MS. The detection limits of these sulfonamides in pork were from 16 μg kg⁻¹ (SMT) to 39 μg kg⁻¹ (SMMX). According to the analysis, the linear range was from 50 to 2000 μg kg⁻¹ with relative standard deviation (R.S.D.s) value below 15% (intra-day) and 19% (inter-day). The proposed method was tested by analyzing meats from a local market for sulfonamides residues. Some sulfonamides in our study were detected in the meat samples. The concentration of these residual sulfonamides ranged from 66 μg kg⁻¹ (SDZ) to 157 μg kg⁻¹ (SQX) in a chicken sample. The results demonstrate that the SPME-LC-MS system is highly effective in analyzing trace sulfonamides in meat products.     

Determination of tetracyclines in surface water and milk by the magnesium hydroxide coprecipitation method

A simple coprecipitation method was developed for the determination of tetracyclines (TCs) in surface water and milk by high-performance liquid chromatography with diode-array detection (HPLC–DAD). Magnesium ion was added into the surface water or the acetonitrile (MeCN) extract of milk. After alkalinization, magnesium hydroxide precipitates which had been formed can be separated from the matrix solution easily by centrifuging and then a dissolution step was performed by adding a small amount of acid. The final solution could be introduced directly into HPLC system for the determination of the analytes. Under optimal conditions, recoveries for the analysis of spiked surface water samples ranged from 83.6% to 95.1% with relative standard deviation of 2.0–5.5%. For milk samples, relative recoveries were 95.9–104.6% with relative standard deviation of 3.4–6.7%. The enrichment factors ranged from 41.5 to 48.1 for 10 mL water samples, and from 3.6 to 4.4 for 1 mL MeCN extracts of milk. Limits of detection ranged from 0.13 to 0.51 ng/mL, and from 3.0 to 8.5 ng/g for four TCs in surface water and milk samples, respectively.     

Hollow fiber supported ionic liquid membrane microextraction for determination of sulfonamides in environmental water samples by high-performance liquid chromatography

By using ionic liquid as membrane liquid and tri-n-octylphosphine oxide (TOPO) as additive, hollow fiber supported liquid phase microextraction (HF-LPME) was developed for the determination of five sulfonamides in environmental water samples by high-performance liquid chromatography with ultraviolet detection The extraction solvent and the parameters affecting the extraction enrichment factor such as the type and amount of carrier, pH and volume ratio of donor phase and acceptor phase, extraction time, salt-out effect and matrix effect were optimized. Under the optimal extraction conditions (organic liquid membrane phase: [C₈MIM][PF₆] with 14% TOPO (w/v); donor phase: 4 mL, pH 4.5 KH₂PO₄ with 2 M Na₂SO₄; acceptor phase: 25 μL, pH 13 NaOH; extraction time: 8 h), low detection limits (0.1–0.4 μg/L, RSD ≤ 5%) and good linear range (1–2000 ng/mL, R² ≥ 0.999) were obtained for all the analytes. The presence of humic acid (0–25 mg/L dissolved organic carbon) and bovine serum albumin (0–100 μg/mL) had no significant effect on the extraction efficiency. Good spike recoveries over the range of 82.2–103.2% were obtained when applying the proposed method on five real environmental water samples. These results indicated that this present method was very sensitive and reliable with good repeatabilities and excellent clean-up in water samples. The proposed method confirmed hollow fiber supported ionic liquid membrane based LPME to be robust to monitoring trace levels of sulfadiazine, sulfamerazine, sulfamethazine, sulfadimethoxine and sulfamethoxazole in aqueous samples.     

Determination of pyridine, 2-picoline, 4-picoline and quinoline from mainstream cigarette smoke by solid-phase extraction liquid chromatography/electrospray ionization tandem mass spectrometry

The present paper describes the development and validation of a new reversed-phase liquid chromatography–electrospray ionization tandem mass spectrometric method (RP-HPLC–ESI-MS/MS) for simultaneous determination of pyridine, 2-picoline, 4-picoline and quinoline from mainstream cigarette smoke. Liquid–liquid extraction followed by solid-phase extraction was applied to extract the target analytes from cigarette smoke. Baseline chromatographic separation was achieved by utilizing a Zorbax SB-Aq (4.6 × 150 mm, 5 μm) column in gradient chromatographic conditions with acetonitrile and ammonium acetate buffer as mobile phases. Popular commercially available Indian brand filtered and non-filtered cigarettes were analyzed using the same method. The identification of each chemical was established by chromatographic retention times, analyte specific fragmentation patterns and relative peak area ratios of two product/precursor ion pairs. The limit of detection of this method ranged from 1.74 to 14.32 ng/cig using an injection volume of 20 μl. The reproducibility of this method is excellent and better standard deviations were obtained compared to literature reported values for these chemicals. RSD value is less than 9% for all analytes.     

Ultra-high-pressure liquid chromatography–tandem mass spectrometry method for the determination of alkylphenols in soil

A novel method has been developed for the determination of alkylphenols in soil by ultra-high-pressure liquid chromatography employing small particle sizes, combined with tandem mass spectrometry. Soil samples were extracted with pressurized liquid extraction (PLE) and then cleaned with solid-phase extraction (SPE). The extracts were separated on C18 column (1.7 μm, 50 mm × 2.1 mm) with a gradient elution and a mobile phase consisting of water and acetonitrile, and then detected by an electrospray ionization tandem mass spectrometry in negative ion mode with multiple reaction monitoring (MRM). Compared with traditional liquid chromatography, it took ultra-high-pressure liquid chromatography much less time to analyze alkylphenols. Additionally, the ultra-high-pressure liquid chromatography/tandem mass spectrometry method produces satisfactory reliability, sensitivity, and accuracy. The average recoveries of the three target analytes were 74.0–103.4%, with the RSD < 15%. The calibration curves for alkylphenols were linear within the range of 0.01–0.4 μg/ml, with the correlation coefficients greater than 0.99. When 10 g soil sample was used for analysis, the limits of quantification (LOQs) of the three alkylphenols were all 1.0 μg/kg.     

Determination of β-sitosterol and cholesterol in oils after reverse micelles with Triton X-100 coupled with ultrasound-assisted back-extraction by a water/chloroform binary system prior to gas chromatography with flame ionization detection

Ultrasonic back-extraction of Triton X-100 reverse micelles by a water/chloroform binary system and gas chromatography with flame ionization detection (GC-FID) was developed for extraction and determination of β-sitosterol and cholesterol in soybean and sunflower oil samples. After the homogenization of the oil samples with Triton X-100, an aliquot of 200 μL of methanol was added to the samples to form two phases. The clear Triton X-100 extract obtained by centrifugation was treated with a mixture of water (1000 μL) and chloroform (300 μL) for back-extraction of the analytes into the chloroform phase by ultrasonication. After centrifugation, the sedimented chloroform layer was withdrawn easily by a microsyringe and directly injected into the GC-FID system. The influence of several important parameters on the extraction efficiencies of the analytes was evaluated. Under optimized experimental conditions, the calibration graphs were linear in the range of 1.0–30.0 mg L⁻¹ with coefficient of determination more than 0.994 for both analytes. The method detection limit values were in the range of 0.2–0.7 mg L⁻¹. The lower limit of quantification values were in the range of 0.7–2.4 mg L⁻¹. Intra-day relative standard deviations were in the range of 1.0–2.7%. This procedure was successfully applied with satisfactory results to the determination of β-sitosterol and cholesterol in spiked oil samples. The relative mean recoveries of oil samples ranged from 93.6% to 105.0%.     

Dispersive liquid–liquid microextraction method based on solidification of floating organic drop for extraction of organochlorine pesticides in water samples

A new simple and rapid dispersive liquid–liquid microextraction method has been developed for the extraction and analysis of organochlorine pesticides (OCPs) in water samples. The method is based on the solidification of a floating organic drop (DLLME-SFO) and is combined with gas chromatography/electron capture detection (GC/ECD). Very little solvent is required in this method. The disperser solvent (200 μL acetonitrile) containing 10 μL hexadecane (HEX) is rapidly injected by a syringe into the 5.0 mL water sample. After centrifugation, the fine HEX droplets (6 ± 0.5 μL) float at the top of the screw-cap test tube. The test tube is then cooled in an ice bath. After 5 min, the HEX solvent solidifies and is then transferred into a conical vial, where it melts quickly at room temperature, and 1 μL of it is injected into a gas chromatograph for analysis. Under optimum conditions, the enrichment factors and extraction recoveries are high and range between 37–872 and 82.9–102.5%, respectively. The linear range is wide (0.025–20 μg L⁻¹), and the limits of detection are between 0.011 and 0.11 μg L⁻¹ for most of the analytes. The relative standard deviation (RSD) for 1 μg L⁻¹ of OCPs in water was in the range of 5.8–8.8%. The performance of the method was gauged by analyzing samples of lake and tap water.     

Determination of andrographolide and dehydroandrographolide in rabbit plasma by on-line solid phase extraction of high-performance liquid chromatography

The high-performance liquid chromatography (HPLC) coupled with on-line solid phase extraction (SPE) and ultraviolet (UV) detection was developed for determining andrographolide and dehydroandrographolide in rabbit plasma. Plasma samples (100 μL) were injected directly into a C18 SPE column and the biological matrix was washed out for 6 min using 15% aqueous methanol. By rotation of the switching valve, andrographolide and dehydroandrographolide were eluted in the back-flush mode and transferred to the analytical column by the chromatographic mobile phase consisted of methanol:acetonitrile (ACN):water (50:10:40; v/v). The UV detection was performed at 225 nm. The calibration curves showed excellent linear relationship (R ≥ 0.9993) over the concentration range of 0.05-5.0 μg mL⁻¹. The within- and between-day precisions (R.S.D.) of two analytes were in the range of 1.2-6.5% and the accuracies were between 92.0% and 102.1%. Their recoveries were all greater than 94%. The limits of detection were 0.019 μg mL⁻¹ for andrographolide and 0.022 μg mL⁻¹ for dehydroandrographolide. This method was successfully applied to the plasma concentration-time curve study after oral administration of Andrographis paniculata Nees extract in rabbit.     

Determination of environmental estrogens in human urine by high performance liquid chromatography after fluorescent derivatization with p-nitrobenzoyl chloride

A high performance liquid chromatographic method (HPLC) for the simultaneous determination of 4-nonylphenol, bisphenol A, 17α-ethinylestradiol and three endogenic estrogens including 17α-estradiol, 17β-estradiol, estriol in urine sample, based on precolumn derivatization with p-nitrobenzoyl chloride, is presented in this paper. The estrogens mentioned above in urine were firstly hydrolyzed with 0.6 mol/l HCl, and then enriched and cleaned-up by ENV-18 C18 solid phase extraction (SPE) column. The estrogens on column were eluted with dichloromethane, and the eluent was evaporated to dryness under gentle nitrogen flow. The residue was allowed to react with p-nitrobenzoyl chloride at 25 °C for 30 min. Separation was performed on a C18 column with gradient elution using acetonitrile and water as mobile phase. A fluorescence detection system was used to detect the fluorescent derivatization products. The detection limit of the method was 2.7 μg/l for bisphenol A and 17β-estradiol, 2.9 μg/l for 4-nonylphenol, 4.6 μg/l for 17α-estradiol and 17α-ethinylestradiol and 8.3 μg/l for estriol, respectively. The relative standard deviations (R.S.D.) ranged from 1.29 to 4.52% and the recoveries ranged from 85.5 to 99.9%. The method was applied to the determination of those six estrogens mentioned above in human urine samples collected from 20 healthy volunteers (aged 21-29). Bisphenol A (BPA) and 4-nonylphenol (NP) were detected with average contents of 1.22 ± 1.38 mg/l and 0.38 ± 0.77 mg/l in 10 male urine samples and 1.29 ± 1.22 mg/l and 0.05 ± 0.05 mg/l in 10 female urine samples, respectively. 17α-ethinylestradiol (α-EE2) was also detected with average contents of 0.13 ± 0.41 mg/l and 0.06 ± 0.15 mg/l in male and female urine samples, respectively.     

Dynamic supported liquid membrane tip extraction of glyphosate and aminomethylphosphonic acid followed by capillary electrophoresis with contactless conductivity detection

A dynamic supported liquid membrane tip extraction (SLMTE) procedure for the effective extraction and preconcentration of glyphosate (GLYP) and its metabolite aminomethylphosphonic acid (AMPA) in water has been investigated. The SLMTE procedure was performed in a semi-automated dynamic mode and demonstrated a greater performance against a static extraction. Several important extraction parameters such as donor phase pH, cationic carrier concentration, type of membrane solvent, type of acceptor stripping phase, agitation and extraction time were comprehensively optimized. A solution of Aliquat-336, a cationic carrier, in dihexyl ether was selected as the supported liquid incorporated into the membrane phase. Quantification of GLYP and AMPA was carried out using capillary electrophoresis with contactless conductivity detection. An electrolyte solution consisting of 12 mM histidine (His), 8 mM 2-(N-morpholino)ethanesulfonic acid (MES), 75 μM cetyltrimethylammonium bromide (CTAB), 3% methanol, pH 6.3, was used as running buffer. Under the optimum extraction conditions, the method showed good linearity in the range of 0.01–200 μg/L (GLYP) and 0.1–400 μg/L (AMPA), acceptable reproducibility (RSD 5–7%, n = 5), low limits of detection of 0.005 μg/L for GLYP and 0.06 μg/L for AMPA, and satisfactory relative recoveries (90–94%). Due to the low cost, the SLMTE device was disposed after each run which additionally eliminated the possibility of carry-over between runs. The validated method was tested for the analysis of both analytes in spiked tap water and river water with good success.     

Dispersive solid-phase microextraction method for sample extraction in the analysis of four tetracyclines in water and milk samples by high-performance liquid chromatography with diode-array detection

A dispersive solid-phase microextraction (dispersive-SPME) method for the determination of tetracycline, oxytetracycline, chlortetracycline and doxycycline is proposed. Different silica-based and polymeric sorbents were evaluated for their capacity to simultaneously preconcentrate tetracyclines (TCs) in the dispersive format from aqueous or organic solutions. Silica-based sorbents especially functionalized with primary amine, secondary amine, or carbonyl groups have showed higher capacity than polymeric sorbents under organic environment. In the proposed dispersive solid-phase microextraction method, after extraction with acetonitrile and salt-promoted partitioning, TCs were adsorbed to a small amount of dispersive silica-based primary and secondary amine sorbents, desorbed with a small volume of desorption solution, and determined by high-performance liquid chromatography with diode-array detection. Under the optimal conditions, recoveries were determined for surface water and milk samples spiked at 10 ng/mL and 50–150 ng/g, respectively, and quantification was achieved by matrix-matched calibration. The calibration curves of four TCs in both samples showed linearity with a correlation coefficient value above 0.997. Average recoveries ranged from 97.1 to 104.1% and the precision was from 2.0 to 5.6%. Limits of detection ranged from 0.7 to 3.5 ng/mL and from 7.9 to 35.3 ng/g for four TCs surface in surface water and milk samples, respectively.     

Determination of four heterocyclic insecticides by ionic liquid dispersive liquid–liquid microextraction in water samples

A novel microextraction method termed ionic liquid dispersive liquid–liquid microextraction (IL-DLLME) combining high-performance liquid chromatography with diode array detection (HPLC-DAD) was developed for the determination of insecticides in water samples. Four heterocyclic insecticides (fipronil, chlorfenapyr, buprofezin, and hexythiazox) were selected as the model compounds for validating this new method. This technique combines extraction and concentration of the analytes into one step, and the ionic liquid was used instead of a volatile organic solvent as the extraction solvent. Several important parameters influencing the IL-DLLME extraction efficiency such as the volume of extraction solvent, the type and volume of disperser solvent, extraction time, centrifugation time, salt effect as well as acid addition were investigated. Under the optimized conditions, good enrichment factors (209–276) and accepted recoveries (79–110%) were obtained for the extraction of the target analytes in water samples. The calibration curves were linear with correlation coefficient ranged from 0.9947 to 0.9973 in the concentration level of 2–100 μg/L, and the relative standard deviations (RSDs, n = 5) were 4.5–10.7%. The limits of detection for the four insecticides were 0.53–1.28 μg/L at a signal-to-noise ratio (S/N) of 3.     

A novel magnetic ionic liquid modified carbon nanotube for the simultaneous determination of aryloxyphenoxy-propionate herbicides and their metabolites in water

A reliable, sensitive, rapid and environmentally friendly analysis procedure for the simultaneous determination of the analytes with a wide range of polarity in the environmental water was developed by coupling dispersive magnetic solid-phase extraction (d-MSPE) with high-performance liquid chromatography (HPLC)–diode array detector (DAD) and ultra-high pressure liquid chromatography (UHPLC)-triple quadrupole mass spectrometer (MS/MS), in this work. Magnetic ionic liquid modified multi-walled carbon nanotubes (m-IL-MWCNTs) were prepared by spontaneous assembly of magnetic nanoparticles and imidazolium-modified carbon nanotubes, and used as the sorbent of d-MSPE to simultaneously extract aryloxyphenoxy-propionate herbicides (AOPPs) and their polar acid metabolites due to the excellent π–π electron donor–acceptor interactions and anion exchange ability. The factors, including the amount of sorbent, pH of the sample solution, extraction time and the volume of elution solvent were investigated. Under the optimized conditions, the proposed d-MSPE coupling to HPLC–DAD system had a satisfactory performance, the limits of detection (LODs, defined as the signal to noise ratio of 3) and the limits of quantification (LOQs, defined as the signal to noise ratio of 10) for analytes in Milli-Q water were in the range of 2.8–14.3 and 9.8–43.2 μg L⁻¹ respectively. Calibration curves were linear (r² > 0.998) over the concentration range from 0.02 to 1 mg L⁻¹. The recoveries of the eight analytes ranged from 66.1 to 89.6% with the RSDs less than 8.6%. In order to extend the method in extremely low concentration analysis, d-MSPE-UHPLC–MS/MS was investigated, which showed better performance in terms of limit of detection and analysis time.     

Streamlining sample preparation and gas chromatography–tandem mass spectrometry analysis of multiple pesticide residues in tea

In this work, a new rapid method for the determination of 135 pesticide residues in green and black dry tea leaves and stalks employing gas chromatography coupled to tandem mass spectrometry (GC–MS/MS) with a triple quadrupole was developed and validated. A substantial simplification of sample processing prior to the quantification step was achieved: after addition of water to a homogenised sample, transfer of analytes into an acetonitrile layer was aided by the addition of inorganic salts. Bulk co-extracts, contained in the crude organic extract obtained by partition, were subsequently removed by liquid–liquid extraction using hexane with the assistance of added 20% (w/w) aqueous NaCl solution. The importance of matrix hydration prior to the extraction for achieving good recoveries was demonstrated on tea samples with incurred pesticide residues. For most of the analytes, recoveries in the acceptable range of 70–120% and repeatabilities (relative standard deviations, RSDs) ≤20% were achieved for both matrices at spiking levels of 0.01, 0.1 and 1 mg kg⁻¹. Under optimised GC–MS/MS conditions, most of the analytes gave lowest calibration level ≤0.01 mg kg⁻¹, permitting the control at the maximum residue levels (MRLs) laid down in Regulation (EC) No 396/2005. The developed method was successfully applied to the determination of pesticide residues in real tea samples.     

Development of an ultra-high-pressure liquid chromatography–tandem mass spectrometry multi-residue sulfonamide method and its application to water,manure slurry,and soils from swine rearing facilities

An analytical method was developed using ultra-high-pressure liquid chromatography–triple quadrupole-tandem mass spectrometry (UHPLC–TQ-MS/MS) to simultaneously analyze 14 sulfonamides (SA) in 6 min. Despite the rapidity of the assay the system was properly re-equilibrated in this time. No carryover was observed even after high analyte concentrations. The instrumental detection limit based on signal-to-noise ratio (S/N) > 3, was below 1 pg/μL (5 pg on column) for all SAs except sulfachloropyridazine. Surface water, ground water, soil, and slurry manure contained in storage ponds in and around swine [Sus scrofa domesticus] rearing facilities were analyzed. Sample cleanup for ground water and surface water included using solid phase extraction (SPE) using Oasis^® hydrophilic–lipophilic balance (HLB) cartridges. The soil and slurry manure required tandem strong anion exchange (SAX) and HLB solid phase extraction cartridges for sample cleanup. With few exceptions, the recoveries ranged from 60 to 100% for all matrices. The minimum detectable levels were below 2.0 ng/L for water, 30 ng/L for slurry manure, and 45 ng/kg for soil except for sulfachloropyridazine. The coefficient of variation (CV) was within 20% for most of the compounds analyzed. Using this method, sulfamethazine concentrations of 2250–5060 ng/L, sulfamethoxazole concentrations of 108–1.47 × 10⁶ ng/L, and sulfathiazole concentrations of 785–1700 ng/L were found in the slurry manure. Sulfadimethoxine (2.0–32 ng/L), sulfamethazine (2.0–5.1 ng/L), and sulfamethoxazole (20.5–43.0 ng/L) were found in surface water and ground water. In top soil (0–15 cm), sulfamethazine ranged 34.5–663 ng/kg dry weight in those locations that received slurry manure as a nutrient; no SAs were found in the soil depths between 46 and 61 cm. The speed makes the method practical for medium to high throughput applications. The sensitivity and positive analyte identification make the method suitable for the demanding requirements for real world applications.     

At-line microextraction by packed sorbent-gas chromatography–mass spectrometry for the determination of UV filter and polycyclic musk compounds in water samples

An at-line analysis protocol is presented that allows the determination of four UV filters, two polycyclic musk compounds and caffeine in water at concentration level of ng L⁻¹. The fully automated method includes analytes enrichment by Microextraction by packed sorbent (MEPS) coupled directly to large volume injection-gas chromatography–mass spectrometry. Two common SPE phases, C8 and C18, were examined for their suitability to extract the target substances by MEPS. The analytes were extracted from small sample volumes of 800 μL with recoveries ranging from 46 to 114% for the C8-sorbent and 65–109% for the C18-sorbent. Limits of detection between 34 and 96 ng L⁻¹ enable the determination of the analytes at common environmental concentration levels. Both sorbents showed linear calibration curves for most of the analytes up to a concentration level of 20 ng mL⁻¹. Carryover was minimized by washing the sorbents 10 times with 100 μL methanol. After this thorough cleaning, the MEPS are re-used and up to 70 analyses can be performed with the same sorbent. The fully automated microextraction GC–MS protocol was evaluated for the influence of matrix substances typical for wastewater. Dilution of samples prior to MEPS is recommended when the polar caffeine is present at high concentration. Real water samples were analyzed by the MEPS-GC–MS method and compared to standard SPE.     

Simple assay for monitoring seven quinolone antibacterials in eggs: Extraction with hot water and liquid chromatography coupled to tandem mass spectrometry: Laboratory validation in line with the European Union Commission Decision 657/2002/EC

A simple and rapid method able to determine residues of seven quinolone antibacterials in whole eggs is presented here. This method is based on the matrix solid-phase dispersion technique with hot water as extractant followed by liquid chromatography–tandem mass spectrometry. After depositing 1.5 g of an egg sample containing the analytes and the analyte surrogate (norfloxacin) on sand (crystobalite), this material was packed into an extraction cell. Quinolones were extracted by flowing 6 mL of water acidified with 50 mmol/L formic acid through the cell heated at 100 °C. After pH adjustment and filtration of the extract, 100 μL of it was injected into the LC column. MS data acquisition was performed in the multiple reaction monitoring mode, selecting two precursor ion to product ion transitions for each target compound. Hot water appeared an efficient extracting medium, since absolute recoveries of the analyte in egg at the level of 20 ng/g were 89–103%. Estimated limits of quantification (S/N = 10) were 0.2–0.6 ng/g. Based on the EU Commission Decision 2002/657/EC, the method was validated in terms of ruggedness, specificity, linearity, within-laboratory reproducibility, decision limit (CCα and detection capability (CCβ). Depending on the particular analyte, CCαs ranged between 0.41 and 2.6 ng/g, while CCβs were 0.64–3.7 ng/g. The method was linear in the 3–30 ng/g range, with typical R² values higher than 0.97. The within-laboratory reproducibility (n = 21) at 6 ng/g level was in the 9.0–12% range. After validation, a depletion study of enrofloxacin and one of its metabolites, i.e. ciprofloxacin, in eggs was conducted.