Development and validation of a liquid chromatography–tandem mass spectrometry method for simultaneous quantification of p-aminohippuric acid and inulin in rat plasma for renal function study

The first liquid chromatography–tandem mass spectrometry method was developed and validated for the simultaneous quantification of p-aminohippuric acid and inulin, both typical biomarkers of kidney function. 5-(Hydroxymethyl)furfural, generated from inulin by acid and heat preparation, was used as an inulin substitute for the quantification. Acetaminophen was used as the internal standard. Solid-phase extraction was carried out with 5% methanol as the washing solution to optimize the retention of the analytes and to avoid obstruction of the orifice plate of the mass spectrometer caused by any unreacted inulin residue remaining from the sample preparation process. Chromatography separation was performed on a Symmetry C₁₈ column and a mobile phase composed of 2 mM ammonium formate and 0.1% formic acid in water (solvent A) and 2 mM ammonium formate and 0.1% formic acid in acetonitrile (solvent B) (30:70, v/v). Detection was performed with a triple-quadrupole tandem mass spectrometer using positive ion mode electrospray ionization in the multiple reaction monitoring mode. The selected transitions were m/z 195.2 → 120.2, 127.1 → 109.1, and 152.1 → 110.0 for p-aminohippuric acid, inulin [measured as 5-(hydroxymethyl)furfural], and acetaminophen, respectively. The linearity ranged from 10 to 140 μg/mL and from 100 to 1,400 μg/mL for p-aminohippurric acid and inulin (r > 0.99), respectively. The precisions and accuracies were all within 12 and 11% for the lower limit of quantification and quality control samples, respectively. This application was proven to be reliable and accurate and was successfully applied to a renal function study.     

TD-DFT Calculation on UV-Vis Spectra of the Complex 8-((Trimethoxysilyl)methylthio)quinoline⋅ZnCl<Subscript>2</Subscript>

The electronic structure and absorption spectra properties of the complex 8-((trimethoxysilyl)methylthio)quinoline⋅ZnCl₂ in the gas phase and in acetonitrile (MeCN) have been investigated by means of DFT/TD-DFT calculations. Calculation results indicate that the broad and weak experimentally observed absorption bands of the complex in MeCN at 335.6 nm originates from spin-forbidden singlet-triplet transitions, but the other experimentally observed absorption bands at 318.5 nm, 310.6 nm and 237.5 nm arise from spin-allowed singlet-singlet transitions. Inclusion of MeCN as solvent leads to dramatic changes in the electronic structures and energy levels of the frontier molecular orbitals of the complex, and hence transition mechanisms of the absorption bands are also changed. For the complex, whether in the gas phase or in MeCN, the metal Zn does not participate in the transitions involved, in the gas phase the calculated lowest-energy absorption band of the complex comes from π→π ^∗ mixed with n→π ^∗ transitions with LLCT (ligand-to-ligand charge transfer) character, while in MeCN, the calculated lowest-energy absorption band is of LLCT/ILCT (intra-ligand charge transfer) character.     

Determination of zearalenone and its metabolites in endometrial cancer by coupled separation techniques

This study presents a selective method of isolation of zearalenone (ZON) and its metabolite, α-zearalenol (α-ZOL), in neoplastically changed human tissue by accelerated solvent and ultrasonic extractions using a mixture of acetonitrile/water (84/16% v/v) as the extraction solvent. Extraction effectiveness was determined through the selection of parameters (composition of the solvent mixture, temperature, pressure, number of cycles) with tissue contamination at the level of nanograms per gram. The produced acetonitrile/water extracts were purified, and analytes were enriched in columns packed with homemade molecularly imprinted polymers. Purified extracts were determined by liquid chromatography (LC) coupled with different detection systems (diode array detection - DAD and mass spectrometry - MS) involving the Ascentis RP-Amide as a stationary phase and gradient elution. The combination of UE-MISPE-LC (ultrasonic extraction - molecularly imprinted solid-phase extraction - liquid chromatography) produced high (R ≈ 95–98%) and repeatable (RSD < 3%) recovery values for ZON and α-ZOL.     

Effect of Physical Properties and Emulsification Conditions on the Microsphere Size Prepared Using a Solvent Extraction Process

Microspheres were prepared using a hydrocarbon-perfluorocarbon solvent extraction process. The effect of the physical properties and the emulsification conditions on the mean microsphere size was investigated. The viscosity of the dispersed and the continuous phase greatly affected the microsphere size. Smaller microspheres were produced at the same mixing intensity when the viscosity of the dispersed phase decreased. Increased continuous phase viscosity reduced the coalescenceof the droplets and hence smaller microspheres were produced. The mean microsphere size first decreased as the volume ratio of the dispersed phase to the continuous phase increased but upon further increase the mean microsphere size increased. The effect of the volume ratio on the microsphere size was linked to the surfactant concentration. The stability of the studied hydrocarbon-in-fluorocarbon emulsion is poor. One reason for the poor stability is the high density difference between the phases. The emulsion droplets were solidified by siphoning part of the emulsion in the fresh continuous phase, which extracted the solvent from the dispersed phase. The effect of emulsion transfer time between the emulsification and solidification steps on the particle size was studied but no significant effect was observedduring the controlled time interval.     

Dispersive liquid-liquid microextraction based on the solidification of a floating organic droplet for simultaneous analysis of diethofencarb and pyrimethanil in apple pulp and peel

A method for analysis of diethofencarb and pyrimethanil in apple pulp and peel was developed by using dispersive liquid–liquid microextraction based on solidification of a floating organic droplet (DLLME-SFO) and high-performance liquid chromatography with diode-array detection (HPLC–DAD). Acetonitrile was used as the solvent to extract the two fungicides from apple pulp and peel, assisted by microwave irradiation. When the extraction process was finished, the target analytes in the extraction solvent were rapidly transferred from the acetonitrile extract to another extraction solvent (1-undecanol) by using DLLME-SFO. Because of the lower density of 1-undecanol than that of water, the finely dispersed droplets of 1-undecanol collected on the top of aqueous sample and solidified at low temperature. Meanwhile, the tiny particles of apple cooled and precipitated. Recovery was tested for a concentration of 8 μg kg⁻¹. Recovery of diethofencarb and pyrimethanil from apple pulp and peel was in the range 83.5–101.3%. The repeatability of the method, expressed as relative standard deviation, varied between 4.8 and 8.3% (n = 6). Detection limits of the method for apple pulp and peel varied from 1.2–1.6 μg kg⁻¹ for the two fungicides. Compared with conventional sample preparation, the method has the advantage of rapid speed and simple operation, and has high enrichment factors and low consumption of organic solvent.     

Development of continuous dispersive liquid–liquid microextraction performed in home-made device for extraction and preconcentration of aryloxyphenoxy-propionate herbicides from aqueous samples followed by gas chromatography–flame ionization detection

In this study, a rapid, simple, and efficient sample preparation method based on continuous dispersive liquid–liquid microextraction has been developed for the extraction and preconcentration of aryloxyphenoxy-propionate herbicides from aqueous samples prior to their analysis by gas chromatography–flame ionization detection. In this method, two parallel glass tubes with different diameters are connected with a teflon stopcock and used as an extraction device. A mixture of disperser and extraction solvents is transferred into one side (narrow tube) of the extraction device and an aqueous phase containing the analytes is filled into the other side (wide tube). Then the stopcock is opened and the mixture of disperser and extraction solvents mixes with the aqueous phase. By this action, the extraction solvent is dispersed continuously as fine droplets into the aqueous sample and the target analytes are extracted into the fine droplets of the extraction solvent. The fine droplets move up through the aqueous phase due to its low density compared to aqueous phase and collect on the surface of the aqueous phase as an organic layer. Finally an aliquot of the organic phase is removed and injected into the separation system for analysis. Several parameters that can affect extraction efficiency including type and volume of extraction and disperser solvents, sample pH, and ionic strength were investigated and optimized. Under the optimum extraction conditions, the extraction recoveries and enrichment factors ranged from 49 to 74% and 1633 to 2466, respectively. Relative standard deviations were in the ranges of 3–6% (n = 6, C = 30 μg L⁻¹) for intra-day and 4–7% (n = 4, C = 30 μg L⁻¹) for inter-day precisions. The limits of detection were in the range of 0.20–0.86 μg L⁻¹. Finally the proposed method was successfully applied to determine the target herbicides in fruit juice and vegetable samples.     

Analytical method for the determination of trace levels of steroid hormones and corticosteroids in soil, based on PLE/SPE/LC-MS/MS

The aim of this study was to develop an efficient, sensitive and reliable analytical method for the determination of traces of steroid hormones (including oestrogen, androgens and progestagens) and corticosteroids in soil. A method of sample preparation involving pressurized liquid extraction (PLE) and solid-phase extraction (SPE) was developed for the determination of six steroids and five corticosteroids in soils, followed by analysis by liquid chromatography-tandem mass spectrometry. The conditions employed for PLE involved acetone/methanol (50:50) as the extracting solvent, a temperature of 80 °C, two cycles and a static time of 5 min. The extraction was followed by a SPE clean-up based on a polymeric phase. With use of protocol, a residual matrix effect was, however, highlighted. The limit of detection in soil was 0.08–0.89 ng/g for steroids and 0.09–2.84 ng/g for corticosteroids.     

Quantitative analysis of eletriptan in human plasma by HPLC-MS/MS and its application to pharmacokinetic study

Authors developed a simple, sensitive, selective, rapid, rugged, and reproducible liquid chromatography–tandem mass spectrometry method for the quantification of eletriptan (EP) in human plasma using naratriptan (NP) as an internal standard (IS). Chromatographic separation was performed on Ascentis Express C18, 50 × 4.6 mm, 2.7 μm column. Mobile phase was composed of 0.1% formic acid: methanol (40:60 v/v), with 0.5 mL/min flow rate. Drug and IS were extracted by liquid–liquid extraction. EP and NP were detected with proton adducts at m/z 383.2→84.3 and 336.2→97.8 in multiple reaction monitoring (MRM) positive mode, respectively. The method was validated with the correlation coefficients of (r ²) ≥ 0.9963 over a linear concentration range of 0.5–250.0 ng/mL. This method demonstrated intra- and inter-day precision within 1.4–9.2% and 4.4–5.5% and accuracy within 96.8–103% and 98.5–99.8% for EP. This method is successfully applied in the bioequivalence study of 24 human volunteers.     

Ultrasound-enhanced surfactant-assisted dispersive liquid–liquid microextraction and high-performance liquid chromatography for determination of ketoconazole and econazole nitrate in human blood

A simple and efficient method, based on ultrasound-enhanced surfactant-assisted dispersive liquid–liquid microextraction (UESA-DLLME) followed by high-performance liquid chromatography (HPLC) has been developed for extraction and determination of ketoconazole and econazole nitrate in human blood samples. In this method, a common cationic surfactant, cetyltrimethylammonium bromide (CTAB), was used as dispersant. Chloroform (40 μL) as extraction solvent was added rapidly to 5 mL blood containing 0.068 mg mL⁻¹ CTAB. The mixture was then sonicated for 2 min to disperse the organic chloroform phase. After the extraction procedure, the mixture was centrifuged to sediment the organic chloroform phase, which was collected for HPLC analysis. Several conditions, including type and volume of extraction solvent, type and concentration of the surfactant, ultrasound time, extraction temperature, pH, and ionic strength were studied and optimized. Under the optimum conditions, linear calibration curves were obtained in the ranges 4–5000 μg L⁻¹ for ketoconazole and 8–5000 μg L⁻¹ for econazole nitrate, with linear correlation coefficients for both >0.99. The limits of detection (LODs, S/N = 3) and enrichment factors (EFs) were 1.1 and 2.3 μg L⁻¹, and 129 and 140 for ketoconazole and econazole nitrate, respectively. Reproducibility and recovery were good. The method was successfully applied to the determination of ketoconazole and econazole nitrate in human blood samples.     

2D LC Separation and Determination of Bradykinin in Rat Muscle Tissue Dialysate with On-Line SPE-HILIC-SPE-RP-MS

A 2D liquid chromatography (LC) system using hydrophilic interaction chromatography (HILIC) and reversed phase columns has been employed for comprehensive (LC × LC) separation of rat muscle tissue micro-dialysate. Incorporation of an on-line reverse-phase solid phase extraction (SPE) enrichment column in front of the first dimension enabled aqueous samples with high salt concentrations to be injected directly without compromising the chromatographic performance of the HILIC column. Since the SPE enrichment column allowed injection of large sample volumes (e.g. 450 μL), a capillary HILIC column (inner diameter 0.3 mm) could be employed instead of a larger column which is often used in the first dimension to load sufficient amounts of sample. The two chromatographic dimensions were connected using a column selector system with 18, 1.0 mm I.D. C₁₈ “transition” SPE columns. A PLRP C₁₈ column was used in the second dimension. The 2D LC system’s performance was evaluated with a tryptic digest mixture of three model proteins. Good trapping accuracy (HILIC→transition SPE→RP recovery >95%) and repeatability (within-and between day retention time RSDs of first and second dimension chromatography >1%) was achieved. A dialysis sample of rat muscle tissue was separated with the 2D system, revealing complexity and large differences in concentrations of the various compounds present, factors which could potentially interfere with the quantification and monitoring of two target analytes, arg-bradykinin and bradykinin. Subsequently, “Heart-cut” 2D LC-electrospray–mass spectrometry (ESI–MS) with post-column on-line standard injection was employed to monitor arg-bradykinin and bradykinin levels as a function of various muscle conditions. The method’s quantification precision was RSD = 3.4% for bradykinin.     

Trace determination of triclosan and triclocarban in environmental water samples with ionic liquid dispersive liquid-phase microextraction prior to HPLC–ESI-MS–MS

A novel and environmentally friendly microextraction method, termed ionic liquid dispersive liquid-phase microextraction (IL-DLPME), has been developed for rapid enrichment of triclosan and triclocarban before analysis by high-performance liquid phase chromatography–electrospray tandem mass spectrometry (HPLC–ESI-MS–MS). Instead of using toxic organic solvents, an ionic liquid was used as a green extraction solvent. This also avoided the instability of the suspending drop in single-drop liquid-phase microextraction, and the heating and cooling step in temperature-controlled ionic liquid dispersive liquid phase microextraction. Factors that may affect the enrichment efficiency, for example volume of ionic liquid, type and volume of dispersive solvent, pH, extraction time, and NaCl content were investigated in detail and optimized. Under optimum conditions, linearity of the method was observed over the range 0.2–12 μg L⁻¹ for triclocarban and 1–60 μg L⁻¹ for triclosan with correlation coefficients ranging from 0.9980 to 0.9990, respectively. The sensitivity of the proposed method was found to be excellent, with limits of detection in the range 0.040–0.58 μg L⁻¹ and precision in the range 7.0–8.8% (RSD, n = 5). This method has been successfully used to analyze real environmental water samples and satisfactory results were achieved. Average recoveries of spiked compounds were in the range 70.0–103.5%. All these results indicated that the developed method would be a green method for rapid determination of triclosan and triclocarban at trace levels in environmental water samples.     

Assisted solvent extraction and ion-trap tandem mass spectrometry for the determination of polychlorinated biphenyls in mussels. Comparison with other extraction techniques

A selective and sensitive analytical method for determination of ten congeners of polychlorinated biphenyls (PCBs 31, 28, 52, 101, 118, 153, 105, 138, 156, and 180) in mussel samples (Mytilus galloprovincialis) based on accelerated solvent extraction (ASE) and gas chromatography–tandem mass spectrometry (GC–MS–MS) is presented in this work. Extraction conditions were optimised using a Plackett–Burman factorial design. The final extracts were analysed after cleanup on alumina columns. The optimised extraction parameters were solvent percentage, sample amount, extraction temperature, pressure, static extraction time, flush percentage, and purge time. The results suggest that PCBs 118, 105, and 180 extractions appeared affected by only one statistically significant factor, pressure, solvent percentage and static extraction time, respectively. Extraction of PCBs 138 and 156 was affected by amount of sample. PCB 138 extraction was also statistically affected by static extraction time and purge time. Quantitative recoveries (64.8–120.3%) were achieved for all PCBs and method precision (RSD < 19%) was satisfactory.     

Determination of 11 priority pollutant phenols in wastewater using dispersive liquid—liquid microextraction followed by high-performance liquid chromatography—diode-array detection

Dispersive liquid—liquid microextraction coupled with high-performance liquid chromatography—diode-array detection was applied for the extraction and determination of 11 priority pollutant phenols in wastewater samples. The analytes were extracted from a 5-mL sample solution using a mixture of carbon disulfide as the extraction solvent and acetone as the dispersive solvent. After extraction, solvent exchange was carried out by evaporating the solvent and then reconstituting the residue in a mixture of methanol–water (30:70). The influences of different experimental dispersive liquid—liquid microextraction parameters such as extraction solvent type, dispersive solvent type, extraction and dispersive solvent volume, salt addition, and pH were studied. Under optimal conditions, namely pH 2, 165-μL extraction solvent volume, 2.50-mL dispersive solvent volume, and no salt addition, enrichment factors and limits of detection ranged over 30–373 and 0.01–1.3 μg/L, respectively. The relative standard deviation for spiked wastewater samples at 10 μg/L of each phenol ranged between 4.3 and 19.3% (n = 5). The relative recovery for wastewater samples at a spiked level of 10 μg/L varied from 65.5 to 108.3%.     

Validated hydrophilic interaction LC-MS/MS method for determination of 2-pyrrolidinone residue: applied to a depletion study of 2-pyrrolidinone in swine liver

A hydrophilic interaction high-performance liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) method for determination of 2-pyrrolidinone in swine liver was developed and validated. After the fortification of 2-pyrrolidinone-d₆ as the internal standard, 2-pyrrolidinone in swine liver was extracted by acetonitrile, and the supernatant was led through a C18 + WAX mixed-mode solid phase extraction (SPE) cartridge. Furthermore, the eluate was adjusted to pH 5.0 and then led through a strong cationic exchange SPE cartridge. 2-Pyrrolidinone and 2-pyrrolidinone-d₆ were concentrated and eluted by acetonitrile containing 2% ammonium hydroxide. The final eluate was acidified and then injected for hydrophilic interaction LC-MS/MS analysis. Mass spectrometry detection was carried using positive turbo-ion spray ionization mode. The multiple reaction monitoring transitions were 86 → 69 for 2-pyrrolidinone and 92 → 75 for 2-pyrrolidinone-d₆. The C18 + WAX mixed-mode SPE cleanup greatly prevented the rapid contamination of mass spectrometer. The further SCX SPE cleanup thoroughly eliminated the absolute matrix effect. Solvent calibration standards could be readily used for quantitative analysis of 2-pyrrolidinone with excellent precision and accuracy. Endogenous levels of 2-pyrrolidinone in some blank matrices was readily determined. Full recoveries were readily achieved by the optimize extraction protocol, and thus the role of 2-pyrrolidinone-d₆ was to just compensate the variation of the injections. The detection limit was 5 ng g⁻¹ swine liver. The validated method was applied to a depletion study of 2-pyrrolidinone in swine liver following intramuscular administration of a drug 2-pyrrolidinone formulation. The matrix effect from tissue samples usually represented a technical challenge for LC-MS/MS analysis, and a very small molecule such as 2-pyrrolidinone also represented a technical barrier for LC-MS/MS analysis. However, the extraction protocol developed in the present study reached the best outcome: zero matrix effect and full recovery.     

Comparison of different sample treatments for the analysis of ochratoxin A in wine by capillary HPLC with laser-induced fluorescence detection

Ochratoxin A (OTA) is a mycotoxin naturally found in various foods, including wine. As OTA is considered as a possible human carcinogen, the maximum concentration for this compound has been established at 2 μg kg⁻¹ in wine by the EU (Directive (CE) No 1881/2006). Typically, immunoaffinity columns have been used for its extraction. However, simpler, more efficient and less contaminant extraction systems are demanding. In this work, dispersive liquid–liquid microextraction using ionic liquid as extractant solvent (IL-DLLME) and the QuEChERS procedure, have been evaluated and compared for extraction of OTA in wine samples. Laser-induced fluorescence (LIF, He–Cd Laser excitation at 325 nm) coupled with capillary HPLC has been used for the determination of OTA, using a sodium dodecyl sulfate micellar solution in the mobile phase to increase the fluorescence intensity. Matrix-matched calibration curves were established for both methods, obtaining LODs (3× S/N) of 5.2 ng·L⁻¹ and 85.7 ng·L⁻¹ for IL-DLLME and QuEChERS, respectively. Clean extracts were obtained for white, rose and red wines with both methods, with recoveries between 88.7–94.2% for IL-DLLME and between 82.6–86.2% for QuEChERS. The precision was evaluated in terms of repeatability (n = 9) and intermediate precision (n = 15), being ≤ 8.5% for IL-DLLME and ≤ 5.4% for QuEChERS.     

β Phase transformations in the Cu–11mass%Al alloy with Ag additions

In the Cu–Al system, due to the sluggishness of the β ↔ (α + γ₁) eutectoid reaction, the β phase can be retained metastably. During quenching, metastable β alloys undergo a martensitic transformation to a β′ phase at Al low content. The ordering reaction β ↔ β₁ precedes the martensitic transformation. The influence of Ag additions on the reactions containing the β phase in the Cu–11mass%Al alloy was studied using differential scanning calorimetry and in situ X-ray diffractometry. The results indicated that, on cooling, two reactions are occurring in the same temperature range, the β → (α + γ₁) decomposition reaction and the β → β₁ reaction, with different reaction mechanisms (diffusive for the former and ordering for the latter) and, consequently, with different reaction rates. For lower cooling rates, the dominant is the decomposition reaction and for higher cooling rates the ordering reaction prevails. On heating, the (α + γ₁) → β reverse eutectoid reaction occurs with a resulting β phase saturated with α. The increase of Ag concentration retards the β → (α + γ₁) decomposition reaction and the β → β₁ ordering reaction, which occurs in the same temperature range, becomes the predominant process.     

Determination of organic micro-pollutants such as personal care products, plasticizers and flame retardants in sludge

In this study, a method for the determination of organic micro-pollutants, i.e. personal care products such as synthetic musk fragrances, household bactericides, organophosphate flame retardants and plasticizers, as well as phthalates in sludge, has been developed. This method is based on lyophilisation and accelerated solvent extraction followed by clean-up steps, i.e. solid phase extraction and size exclusion chromatography. The determination is performed by gas chromatography coupled to mass spectrometry. Stable isotope-labelled compounds such as musk xylene (MX D₁₅), tri-n-butylphosphate (TnBP D₂₇) and triphenylphosphate (TPP D₁₅) were used as internal standards. Recovery rates were determined to be 36–114% (with typical relative standard deviation of 5% to 23%) for the target compounds. The limit of detection was 3–30 ng g⁻¹, and the limit of quantification was 10–100 ng g⁻¹ dry matter.     

Determination of Macrolide Antibiotics Using Dispersive Liquid–Liquid Microextraction Followed by Surface-Assisted Laser Desorption/Ionization Mass Spectrometry

A novel method for the determination of macrolide antibiotics using dispersive liquid–liquid microextraction coupled to surface-assisted laser desorption/ionization mass spectrometric detection was developed. Acetone and dichloromethane were used as the disperser solvent and extraction solvent, respectively. A mixture of extraction solvent and disperser solvent were rapidly injected into a 1.0 mL aqueous sample to form a cloudy solution. After the extraction, macrolide antibiotics were detected using surface-assisted laser desorption/ionization mass spectrometry (SALDI/MS) with colloidal silver as the matrix. Under optimum conditions, the limits of detection (LODs) at a signal-to-noise ratio of 3 were 2, 3, 3, and 2 nM for erythromycin (ERY), spiramycin (SPI), tilmicosin (TILM), and tylosin (TYL), respectively. This developed method was successfully applied to the determination of macrolide antibiotics in human urine samples.     

Comparison of dispersive liquid–liquid microextraction and hollow fiber liquid–liquid–liquid microextraction for the determination of fentanyl,alfentanil, and sufentanil in water and biological fluids by high-performance liquid chromatography

Dispersive liquid–liquid microextraction (DLLME) and hollow fiber liquid–liquid–liquid microextraction (HF-LLLME) combined with HPLC–DAD have been applied for the determination of three narcotic drugs (alfentanil, fentanyl, and sufentanil) in biological samples (human plasma and urine). Different DLLME parameters influencing the extraction efficiency such as type and volume of the extraction solvent and the disperser solvent, concentration of NaOH, and salt addition were investigated. In the HF-LLLME, the effects of important parameters including organic solvent type, concentration of NaOH as donor solution, concentration of H₂SO₄ as acceptor phase, salt addition, stirring rate, temperature, and extraction time were investigated and optimized. The results showed that both extraction methods exhibited good linearity, precision, enrichment factor, and detection limit. Under optimal condition, the limits of detection ranged from 0.4 to 1.9 μg/L and from 1.1 to 2.3 μg/L for DLLME and HF-LLLME, respectively. For DLLME, the intra- and inter-day precisions were 1.7–6.4% and 14.2–15.9%, respectively; and for HF-LLLME were 0.7–5.2% and 3.3–10.1%, respectively. The enrichment factors were from 275 to 325 and 190 to 237 for DLLME and HF-LLLME, respectively. The applicability of the proposed methods was investigated by analyzing biological samples. For analysis of human plasma and urine samples, HF-LLLME showed higher precision, more effective sample clean-up, higher extraction efficiency, lower organic solvent consumption than DLLME.     

Certified reference material for quantification of polycyclic aromatic hydrocarbons and toxic elements in tunnel dust (NMIJ CRM 7308-a) from the National Metrology Institute of Japan

The National Metrology Institute of Japan has issued a certified reference material of tunnel dust for polycyclic aromatic hydrocarbons (PAHs) and toxic element analyses. PAH certification was performed using isotope dilution mass spectrometry with deuterium-labeled PAHs as internal standards. Three extraction techniques (microwave-assisted extraction with toluene/methanol, Soxhlet extraction with toluene, and pressurized liquid extraction with toluene) were used, and the extracts were measured by gas chromatography/mass spectrometry with two different columns. For values of PAHs, 11 PAHs are provided as certified values between 0.294 and 20.3 mg/kg, and five PAHs are provided as information values. Certified values of five toxic elements (Cr, Ni, Pb, Mn, and Cd) obtained from microwave-assisted digestions and a combination of measurement techniques are also provided between 43.4 and 10.71 × 10³ mg/kg.