A Friendly Complexing Agent for Spectrophotometric Determination of Total Iron

Iron, one of the most common metals in the environment, plays a fundamental role in many biological as well as biogeochemical processes, which determine its availability in different oxidation states. Its relevance in environmental and industrial chemistry, human physiology, and many other fields has made it necessary to develop and optimize analysis techniques for accurate determination. Spectrophotometric methods are the most frequently applied in the analytical determination of iron in real samples. Taking advantage of the fact that desferrioxamine B, a trihydroxamic acid used since the 1970s in chelation therapy for iron overload treatment, forms a single stable 1:1 complex with iron in whichever oxidation state it can be found, a smart spectrophotometric method for the analytical determination of iron concentration was developed. In particular, the full compliance with the Lambert-Beer law, the range of iron concentration, the influence of pH, and the interference of other metal ions have been taken into account. The proposed method was validated in terms of LoD, LoQ, linearity, precision, and trueness, and has been applied for total iron determination in natural water certified material and in biological reference materials such as control human urine and control serum.     

Method validation for determination of arsenic, cadmium, chromium and lead in milk by means of dynamic reaction cell inductively coupled plasma mass spectrometry

With Regulation No. 1881/2006 the European Union fixed a maximum level for lead in milk. Consequently, there is the need to determine very low concentration of elements that may be present in milk in trace and ultratrace levels.Quadrupole inductively coupled plasma mass spectrometry (Q-ICP-MS) combined with dynamic reaction cell (DRC) has been widely employed in order to reach very low concentration, requested for this product. Furthermore, the DRC technology can help in removing polyatomic and argon-based interferences.In the present study, a method for the determination of arsenic, cadmium, chromium and lead in bovine milk was validated according to the EU common standards by means of DRC-ICP-MS. The main parameters evaluated in the validation were: recovery, repeatability and within-laboratory reproducibility, detection and quantification limits, linearity range and measurement uncertainty. Additionally, stability studies of the analyte in solution and ruggedness studies were carried out.The results obtained for limit of detection (LoD) and limit of quantification (LoQ) in μg kg⁻¹ were respectively: As, 3.1 and 9.5; Cd, 0.08 and 0.24; Cr, 0.229 and 0.693; Pb, 0.5 and 1.5. While for the recovery: As, 91%; Cd 96%; Cr 99%; Pb, 95%. As for the repeatability: As, 7%; Cd, 3%; Cr, 6%; Pb, 4%.     

Uncertainty evaluation in the analysis of biological samples by sector field inductively coupled plasma mass spectrometry. Part A: measurements of Be,Cd, Hg,Ir, Pb,Pd, Pt,Rh, Sb,U, Tl and W in human serum

A protocol that utilises data (trueness/recovery, precision and robustness) from validation tests to calculate measurement uncertainty was described and applied to a sector field inductively coupled plasma mass spectrometry (SF‐ICP‐MS)‐based method for the determination of Be, Cd, Hg, Ir, Pb, Pd, Pt, Rh, Sb, U, Tl and W in human serum. The method was validated according to criteria issued by international bodies such as AOAC, Eurachem and ISO and the uncertainty in the analytical measurements was estimated following the Eurachem/Citac guide. The methodology was based on dilution of human serum with water and analysis by serum‐matched standard calibration. The method quantification limits ranged 0.02 µg/L (Tl, Ir) to 0.26 µg/L (Hg). The coefficients of regression were greater than 0.9991 over a range of two orders of magnitude of concentration. The mean trueness was 101% and the mean recovery on three levels of fortification (1‐, 1.5‐, and 2‐times the baseline serum level) ranged between 93.3% and 106%. The maximum relative standard deviation values for repeatability and within‐laboratory reproducibility were 12.8% and 13.5%. The method was robust to slight variations of some critical factors relevant to the sample preparation and SF‐ICP‐MS instrumentation. The relative expanded uncertainty over three levels of concentration ranged from 11.6% (Hg) to 27.6% (Pt), and the uncertainty on the within‐laboratory reproducibility, which included factors such as time, analyst and calibration, represented the main contribution to the overall uncertainty. Copyright © 2010 John Wiley & Sons, Ltd.     

Uncertainty evaluation in the analysis of biological samples by sector field inductively coupled plasma mass spectrometry. Part B: measurements of As, Co, Cr, Mn, Mo, Ni, Sn and V in human serum

This protocol was developed to estimate the uncertainty of measurements in the sector field inductively coupled plasma mass spectrometry analysis of As, Co, Cr, Mn, Mo, Ni, Sn and V in human serum by utilizing in-house validation data. The approach is outlined in the Eurachem/Citac Guide and other relevant publications. The results generated were the followings: (i) coefficients of regression >0.9995 over two orders of magnitude of metal concentration; (ii) method quantification limits between 0.05 μg/L (Cr, Mn) and 0.49 μg/L (As); (iii) mean trueness checked against a certified reference material between 95.4% (As) and 107.7% (Ni); (iv) repeatability better than 10.2% over the range 0.1-2.0 μg/L; (v) reproducibility better than 12.0% over the range 0.1-2.0 μg/L; and (vi) expanded uncertainty budget comprised between 14.7% (Mn) and 27.9% (Cr) over the range 0.1-2.0 μg/L.     

Metabolism of levamisole and kinetics of levamisole and aminorex in urine by means of LC-QTOF-HRMS and LC-QqQ-MS

The antihelminthic drug Levamisole can enhance cocaine effects by conversion into the amphetamine-like drug aminorex. We describe an LC-MS method for the determination of levamisole and its metabolite aminorex in human urine. Selectivity is given, calibration curves were linear within the calibration range 2.5–250 ng/mL; limits of the method were LoD 0.51 ng/mL, LoQ 1.02 ng/mL for levamisole and LoD 0.65 ng/mL, LoQ 0.76 ng/mL for aminorex. Precision data was in accordance with the guidelines (intraday precision for aminorex ranged between 5.75 and 11.0 % for levamisole between 8.36 and 10.9 %; interday precision for levamisole 10.9–16.9 % and for aminorex 7.64–12.7 %; accuracy data for levamisole ?1.96 to –14.3 % and for aminorex?11.9 to–18.5 %). The validated method was successfully applied to study the urinary excretion of levamisole after the administration of 100 mg of levamisole orally. Levamisole and aminorex could be detected in post-administration urine samples. Levamisole could be detected up to 39 h after ingestion, while aminorex was detectable up to 54 h. Maximum aminorex concentrations were 45 ng/mL urine. Further metabolites of levamisole after oral ingestion by means of liquid chromatography hybrid quadrupole time-of-flight high-resolution mass spectrometry (LC-QTOF-HRMS) were identified. Only 0.5 % of the ingested drug was quantified as unchanged levamisole in urine. Besides aminorex, five isomers of aminorex and 4 hydroxy-metabolites of aminorex or its isomers were found. Furthermore, levamisole is also hydroxylated and eliminated free or conjugated with sulfate or glucuronide into urine.     

Measurement uncertainty evaluation and in-house method validation of the herbicide iodosulfuron-methyl-sodium in water samples by using HPLC analysis

A method for separation and quantitative determination of the iodosulfuron-methyl-sodium in water samples by high-performance liquid chromatography (HPLC) was developed and in-house validated in order to demonstrate its performance for monitoring of heterogeneous photocatalytic elimination of the herbicide iodosulfuron-methyl-sodium from water. Surface and ground water samples were used to demonstrate its selectivity, detection and quantification limits, linearity, trueness and precision. In addition, stability of iodosulfuron-methyl-sodium was studied in function of temperature and time. Method accuracy was quantified through measurement uncertainty estimate based on method validation data. The paper gives practical and easy to follow guidance on how uncertainty estimates can be obtained from method validation experiments. It shows that, if properly planned and executed, key precision and trueness studies undertaken for validation purposes can also provide much of the data needed to produce an estimate of measurement uncertainty. Our analytical protocol allowed us to quantify iodosulfuron-methyl-sodium in ground water and surface water in concentration level between 2.50–50.0 μmol L⁻¹ with satisfactory recoveries (99–104%) and repeatability lower or equal than 0.3% for all the matrices. We also estimated within-laboratory reproducibility over 3-month period, which was 0.7%. We proved that the method was selective for determination of iodosulfuron-methyl-sodium in the relevant matrices. Measurement uncertainty of results was evaluated to be 4.0% with 95% confidence level. After validation and measurement uncertainty evaluation steps, results obtained showed that the method can be applied to efficiently monitor heterogenous photocatalytic degradation of the herbicide iodosulfuron-methyl-sodium.     

Quantitation of perfluoroalkyl acids,parabens and cotinine from single low volume serum sample by validated analytical method

ABSTRACT

In this paper, we present the results of an analytical method that has been recently developed, validated and successfully applied in a biomonitoring approach. In the environmental pollutant studies it is desirable that the analytical method can determine multiple classes of compounds from a single, small volume sample. The presented analytical method with a simple sample pre-treatment allows the quantitation of 13 perfluoroalkyl acids (PFAAs), 6 parabens and cotinine (used as nicotine biomarker) from a single, small volume of 100 µL serum sample by liquid chromatography-triple quadrupole mass spectrometer (LC-MS/MS). The limits of quantitation (LOQ) for PFAAs, parabens and cotinine were 0.10–0.50, 0.20–0.80 and 0.10 ng/mL, respectively. Besides sensitivity the method has excellent trueness/accuracy and repeatability. The trueness of the method for the determination of PFAAs ranged from 95% to 106% and the repeatability (as RSD %) from 0.6% to 5.6%. The accuracy and RSD for parabens were 73–120% and 1.3–9.7%, respectively, and 100–106% and 1.3–3.5 % for cotinine. Biomonitoring data reveals the presence of several PFAAs and parabens in serum samples of Finnish population. The total concentrations for PFAAs and parabens were from 2.0 to 33 ng/mL and from <LOQ to 1100 ng/mL, respectively. Nearly all non-smokers had the serum cotinine concentration below 1.0 ng/mL, which can be suggested as the cut point for cotinine concentration to identify smoking.     

Efficient electrochemical detection of dopamine with carbon nanocoils and copper tetra(p-methoxyphenyl)porphyrin nanocomposite

Dopamine (DA), a critical catecholamine neurotransmitter, is responsible for normal functioning of body. Its dysregulation causes cognitive disturbances. Thus, an efficient real time monitoring of DA in clinical samples is required. Herein we report a novel nanocomposite comprising of carbon nanocoils (CNC) and copper tetra(p-methoxyphenyl)porphyrin (CuTMePP) for efficient electrochemical detection of dopamine that was characterized by FTIR, UV/vis., Raman, XRD, SEM, TEM and energy dispersive X-ray techniques. The electrochemical studies were performed using cyclic voltammetry (CV), electrochemical impedance spectroscopy and differential pulse voltammetry (DPV). CNC/CuTMePP/glassy carbon (GC) has demonstrated two linear trends between current and concentration i.e. 0.1 to 100.0 µM and 100.0 to 800.0 µM. Limit of detection (LoD), limit of quantification (LoQ) and sensitivity of the electrode in the concentration range of 0.1 to 100.0 µM was 50.0 nM, 167.0 nM and 1.76 µAµM^-1cm^?2, respectively using CV. With DPV, the LoD, LoQ and sensitivity were found to be 64.0 nM, 211.0 nM and 0.75 µAµM^-1cm^?2, respectively obtained in a concentration range of 0.1 to 100.0 µM. The as prepared sensor exhibited good intra/inter-day stabilities, reproducibility, excellent recovery in the human serum samples, presented significant clinical dopamine detection and showed comparable results with other work in literature.     

Validation of an inductively coupled plasma-optical emission spectrometry method for the determination of major elements in farmed rainbow trout (<Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis>)

An inductively coupled plasma?optical emission spectrometry method was optimized and validated for the determination of major elements (Ca, K, Mg, Na and P) in cultivated freshwater fish (rainbow trout Oncorhynchus mykiss). The method was validated by analysis of a Certified Reference Material, consisting in a frozen tissue homogenate from lake trout (Salvelinus namaycush namaycush). The linearity of this method was very good, as evidenced by the coefficients of correlation (r) for calibration graphs that were higher than 0.9999 in all cases and by linearity test (response factor <5% and relative calibration graph slope <2%). Accuracy, expressed as relative recovery (%) in comparison with certified concentration ranged from 100 to 109%, and precision, expressed as residual standard deviation (%) ranged from 1.2 to 6.5% (repeatability) and from 1.0 to 9.6% (reproducibility). The limit of quantification ranged from 4 ng/mL (Ca and Mg) to 203 ng/mL (P). The optimized method was applied to major element determination in skin and muscle samples from rainbow trout fillets.     

Determination of anethole in serum samples by headspace solid-phase microextraction-gas chromatography-mass spectrometry for congener analysis

A rapid headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) method has been developed for the determination of anethole in serum samples. Anethole is a characteristic marker for the consumption of aniseed spirits. This method enabled the detection of anethole with a limit of detection (LoD) of 3.6 ng/ml and a limit of quantification (LoQ) of 5.3 ng/ml in serum samples with a good degree of precision intraday (2.8%) and interday (4.5%). Experiments were conducted with one volunteer, in which the subject consumed the alcoholic drink ouzo on 3 different days under controlled conditions. At defined intervals, blood samples were taken from the subject. Using these blood samples, the concentration-time profiles for anethole were determined. In blood samples taken from 50 drivers who claimed to have consumed drinks containing anethole (ouzo, raki and the German aniseed liqueur "Küstennebel") before the taking of the blood sample, anethole was detected in the serum in concentrations of between 5.4 and 17.6 ng/ml in 10 cases. This is the first report describing the qualitative and quantitative determination of a beverage-characteristic aroma compound - in this case anethole - in serum samples after consumption of alcoholic beverages.     

Analysis of advanced glycation endproducts in dairy products by isotope dilution liquid chromatography–electrospray tandem mass spectrometry. The particular case of carboxymethyllysine

A fully validated multiple-transition recording isotope dilution liquid chromatography–electrospray tandem mass spectrometry (LC–MS/MS) method for the simultaneous quantitative determination of N^?-carboxymethyllysine (CML) and lysine in dairy products is described. Internal standards were [N-1′,2′-¹³C₂]CML and [1,2,3,4,5,6-¹³C₆-2,6-¹⁵N₂]lysine, and the method was validated by evaluating the selectivity, linearity, precision (repeatability and reproducibility) and trueness, using both powder and liquid products. For liquid dairy products, the repeatability and reproducibility was 2.79% and 11.0%, while 4.85% and 4.92% were determined for powder dairy products, respectively. The trueness of the method ranged from −9.6% to −3.6% for powder and from −0.99% to 6.8% for liquid dairy products. The limit of detection for CML was estimated to be 8 ng CML per mg protein while the limit of quantification was 27 ng CML per mg protein. The method encompasses a proteolytic cleavage mediated by enzymatic digestion to reach a complete release of the amino acids prior to a sample cleanup based on solid phase extraction, and followed by LC–MS/MS analysis of CML and lysine residues. To ensure a suitable performance of the enzymatic digestion, CML measurements were compared to values obtained with an acid hydrolysis-mediated proteolysis. Finally, the method was employed for the analysis of CML in various dairy products. The values compare well to the data available in the literature when similar methods were used, even if some discrepancies were observed upon comparison with the results obtained by other techniques such as enzyme-linked immunosorbent assay and GC–MS.     

Mixed liquids for single-drop microextraction of organochlorine pesticides in vegetables

A new approach for the extraction of nine kinds of organochlorine pesticides (OCPs) from vegetable samples coupling single-drop microextraction with gas chromatography-mass spectrometry was presented. Experimental parameters, such as organic solvent, exposure time, agitation and organic drop volume were controlled and optimized. An effective extraction was achieved by suspending a 1.00microL mixed drop of p-xylene and acetone (8:2, v/v) to the tip of a microsyringe immersed in a 2mL donor aqueous solution and stirred at 400rpm. The approach was applied to the determination of OCPs in vegetable samples with a linearity range of 0.05-20ng mL(-1) for alpha-, beta-, gamma-, delta-hexachlorobenzene (BHC) and dicofol, 0.5-20ng mL(-1) for dieldrin and 2,2-bis(4-chlorophenyl)-1,1-dichloroethane (DDD) or 0.5-50ng mL(-1) for 2,2-bis(4-chlorophenyl)-1,1-dichloroethylene (DDE) and 2-(2-chlorophenyl)-2 (4-chlorophenyl)-1,1,1-trichloroethane (p,p'-DDT). Correspondingly, the determination limit at an S/N of 3 ranged from 0.05ng mL(-1) for alpha-, beta-, gamma-, delta-BHC to 0.2ng mL(-1) for dicofol, dieldrin or p,p'-DDT. The relative recoveries were from 63.3 to 100%, with repeatability ranging from 8.74 to 18.9% (relative standard deviation, R.S.D.). The single-drop microextraction was proved to be a fast and simple approach for the pre-concentration of organochlorine pesticides in vegetable samples.     

Comparative validation of amisulpride determination in pharmaceuticals by several chromatographic, electrophoretic and spectrophotometric methods

Depleted uranium (DU) is a by-product of the uranium enrichment process for nuclear fuel. According to the Commission Decision 2002/657/EC, a confirmatory method for the quantification of DU in freeze-dried fish was developed by isotope ratio dynamic reaction cell inductively coupled plasma-mass spectrometry (IR-DRC-ICP-MS). A preliminary study was performed to determine the following parameters: instrumental detection limit (IDL), isotopic ratio measurement limit (IRML), percentage of DU (P(DU)) in presence of natural uranium (NU) and limit of quantification (LoQ(DU)). The analyses were carried out by means of IR-DRC-ICP-MS. Ammonia was the reaction gas used for the dynamic reaction cell. In addition, a sector field inductively coupled plasma mass spectrometer (SF-ICP-MS) was employed to calculate the within-laboratory reproducibility. For the confirmatory method the following parameters were determined: (a) trueness; (b) precision; (c) critical concentrations alpha and beta (CC(alpha), CC(beta)); (d) specificity; (e) stability. Trueness was assessed by using the recovery tests. The recovery and within-laboratory reproducibility were determined by fortifying the blank digested solution of dogfish tissue: six aliquots were fortified at 1, 1.5 and 2 times the LOQ(DU) with 25.0, 37.5 and 50.0 ng L(-1) or 4.16, 6.24, 8.32 microg kg(-1) with a recovery of -8.2, +9.5 and +9.6%, respectively and a within-laboratory reproducibility (three analytical run) of 15.5, 8.0 and 11.0%, respectively. The results for the decision limit and the detection capability were: CC(alpha) = 11.69 ng L(-1) and CC(beta) = 19.8 ng L(-1). The digested solutions resulted to be stable during testing time (60 days) and the method can be considered highly specific as well.     

Preparation of PDMS-coated microspheres by sol-gel method for sorptive extraction of PAHs

In this paper, a novel SPME mode, PDMS-coated solid glass microspheres （SGMs）, were prepared by sol-gel method. Using homemade thermal desorption unit coupled with CGC-FID, six PAHs as model analytes, the performance of the new mode was characterized. The new extractive phase exhibited high thermal stability and satisfactory extraction capability. The detection limits were 0.01-0.045 ng/mL, and the linearity was from 0.5 ng/mL to 96 ng/mL. The R.S.D.s of repeatability for retention time and peak area were all within 0.074% and 6.7%, respectively. The recoveries of the PAHs were 78-127% from the samples taken from river water.     

Qualification and quantification of seventeen natural steroids in plasma by GC-Q-MS and GC-IT-MS/MS

Studying the plasma steroid profile offers information about the possible existence of endocrinological alterations. This study describes the development and validation of gas chromatographic-mass spectrometric and gas tandem mass spectrometric methods for the simultaneous identification of 17 steroid hormones in human plasma using five different solvents. The n-hexane/ethyl acetate solvent mixture, in a proportion of 70/30 (v/v) provided the best results. The extracts were derivatized with N-methyl-N-trimethylsilyl-trifluoroacetamide. The obtained limits of detection were below 1 ng/mL in the majority of the studied steroids and the limits of quantification were below 5 ng/mL; the method obtained good linearity, reproducibility, repeatability, accuracy and recoveries above 95% in most cases.     

Single-drop microextraction and gas chromatography/mass spectrometric determination of anisaldehyde isomers in human urine and blood serum

The application of single-drop microextraction (SDME) followed by gas chromatography/chemical ionization mass spectrometry (GC/CI-MS) was investigated for the determination of anisaldehyde isomers in human urine and blood serum. The effects of extraction solvent, sample agitation rate, salt addition, sampling time and temperature on the extraction efficiency were examined and optimized. Analytical parameters such as linearity, reproducibility, detection limit and relative recovery were evaluated under the optimized experimental conditions. Good reproducibilities of replicate extractions (n = 5) were obtained, with relative standard deviation (RSD) values below 6%. The limits of detection (LOD) using an extraction time of 5 min were found to be in the range 2-5 ng/mL under the selected ion monitoring (SIM) mode of GC/MS. Recoveries of 82-98% were achieved after 5 min extraction.     

Non-protected fluid room-temperature phosphorimetric procedure for the direct determination of naftopidil in biological fluids

Non-protected fluid room temperature phosphorescence, NPRTP, has been applied to the determination of naftopidil in biological fluids. The proposed method is based on obtaining a phosphorescence signal from naftopidil using potassium iodide as heavy atom perturber and sodium sulfite as a deoxygenating reagent without a protected medium. Optimized conditions for the determination were 1.4 mol L= KI, 5.0 x l0(-3) mol L(-1) sodium sulfite, pH 6.5 (adjusted with sodium hydrogen phosphate-dihydrogen phosphate buffer solution, 5.0 x 10(-2) mol L(-1). The delay time, gate time, and time between flashes were 70 micros, 400 micros, and 5 ms, respectively. The maximum phosphorescence signal appeared instantly and the intensity was measured at lambda(ex)=287 nm and lambda(em)=525 nm. The response obtained was linearly dependent on concentration in the range 50 to 600 ng mL(-1). The detection limit, according to error-propagation theory, was 7.93 ng mL(-1) and the detection limit as proposed by Clayton was 11.12 ng mL(-1). The repeatability was studied by using ten solutions of 400 ng mL(-1) naftopidil; if the theory of error propagation is assumed the relative error is 0.88%. The standard deviation of replicates was found to be 3.5 ng mL(-1). This method was successfully applied to the analysis of naftopidil in human serum and urine with recoveries of 104.0 +/- 0.6% for serum and 106.0 +/- 1.0% for urine.     

Determination of selected trace elements in marine biota samples with the application of fast temperature programs and solid sampling continuous source high resolution atomic absorption spectroscopy: method validation

Analytical procedure for the determination of As, Cd, Cu, Ni, Co and Cr in marine biota samples using solid sampling high-resolution continuum source atomic absorption spectrometry (HR CS AAS) and accelerated fast temperature programmes has been developed. Calibration technique based on the use of solid certified reference materials similar to the nature of the analysed sample and statistics of regression analysis were applied. A validation approach in line with the requirements of ISO 17025 standard and Eurachem guidelines was followed. Accordingly, blanks, selectivity, calibration, linearity, working range, trueness, repeatability and reproducibility, limits of detection and quantification and expanded uncertainty for all investigated elements were assessed. The major contributors to the combined uncertainty of the analyte mass fractions were found to be the homogeneity of the samples and the microbalance precision. Traceability to the SI system of units of the obtained with the proposed analytical procedure results was also demonstrated. The potential of the proposed analytical procedure based on solid sampling HR CS AAS technique was demonstrated by direct analysis of marine reference biota samples. Overall, the use of solid sampling HR CS AAS permits obtaining significant advantages for the determination of selected trace elements in marine biota samples, such as straightforward calibration, a high sample throughput, sufficient precision, a suitable limit of detection and reduced risk of analyte loss and contamination.     

冷原子荧光测汞仪检定结果的不确定度

依据JJG548-2004对冷原子荧光测汞仪进行检定时,检定结果的不确定度主要来源于仪器的线性误差、检测限、重复性和标准物质浓度。对各不确定分量进行了评定和计算,求得合成标准不确定度和扩展不确定度分别为0.033ng/mL和0.066ng/mL(k=2)。