Recovery Relative Standard Deviation Research Articles

A novel reverse migration micellar electrokinetic chromatography method for in-capillary screening and quantifying of antioxidant components in Sanyetangzhiqing using 2,2'-Azinobis-(3-ethylbenzthiazoline-6-sulphonate) as oxidation-free radical.

A novel method of reverse migration micellar electrokinetic chromatography (RM-MEKC) using 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulphonate) as oxidation-free radical was developed to screen the major antioxidants from Sanyetangzhiqing (SYTZQ), which is a new patent drug for diabetes. For simultaneous detection and separation of 2,2'-bis (3-ethylbenzothiazoline-6-sulfonic acid) ammonium salt (ABTS+ ) and chemical components of SYTZQ, the key factors were optimized and the method was validated under the optimal conditions. All the relative standard deviations of recovery, precision, and stability were below 6.6%. Based on these, the RM-MEKC method has been successfully used to screen the main antioxidants from SYTZQ tablets. Five compounds, including rosmarinic acid, salvianolic acid B, lithospermic acid, hyperoside, and isoquercetin, were separated and identified as the major antioxidants. There was a linear relationship with correlation coefficient of 0.923 between the total amount of major antioxidants and total antioxidative activity of SYTZQ. Consequently, these five ingredients could be selected as combinatorial markers for quality control of SYTZQ, and the established method was concluded to be a simple, reliable, and powerful tool to screen and quantify active compounds for quality evaluation of SYTZQ.

Validation of an HPLC Method for Pretreatment of Steviol Glycosides in Fermented Milk.

Steviol glycosides are used in food and beverages worldwide as natural sweeteners, serving as a low-calorie sugar substitute. The acceptable daily intake of steviol is 0–4 mg/kg body weight. The rising demand for dairy products has led to a corresponding increase in the use of steviol glycosides in such products. Therefore, it is important to analyze the levels of steviol glycosides in dairy products. Dairy products have high fat contents and unique emulsion characteristics, conferred by a mixture of fat globules, casein micelles, whey proteins, and numerous other small molecules. These characteristics may interfere with the estimation of steviol glycoside levels; therefore, dairy samples require pretreatment. We aimed to develop an objective test for measuring the levels of steviol glycosides through the development of an efficient pretreatment method. In this study, the steviol glycoside content in dairy products was evaluated by using various methods, and an optimal pretreatment method was determined. We used high-performance liquid chromatography to assess the selectivity, linearity, limit of detection, limit of quantification, accuracy, precision, and recovery rate. Calibration curves were linear in the range of 1–50 mg/kg, with a coefficient of determination of ≥0.999. The limit of detection and limit of quantification were in the ranges of 0.11–0.56 and 0.33–1.69 mg/kg, respectively. The relative standard deviation (%) represents the precision of a measurement. The RSD relative standard deviationof recovery varied between 0.16% and 2.83%, and recovery of the analysis varied between 83.57% and 104.84%. These results demonstrate the reliability of the method for measuring the steviol glycoside content. This method can be used for the simple pretreatment of steviol glycosides and can provide an accurate determination of steviol glycoside content in emulsified food matrices, such as dairy products.

LC-MS-MS Determination of 25 Antipsychotic Drugs and Metabolites in Urine for Medication Compliance Monitoring.

A liquid chromatography-tandem mass spectrometry (LC-MS-MS) method was developed for 25 antipsychotic drugs and their metabolite in urine for monitoring medication compliance of mentally disordered criminals on probation. Target compounds were extracted with a solid-phase extraction technique using a newly developed hydrophilic-lipophilic balanced sorbent to remove interferences and minimize the matrix effect (ME). Extracted sample was injected into the LC-MS-MS with an electrospray ionization source in positive mode and multiple-reaction monitoring mode. The analytes were separated and detected within 10 minutes using a reversed-phase column with a gradient elution method using 0.1% formic acid in water and 0.1% formic acid in methanol as mobile phase. The validation parameters were evaluated as follows: selectivity, limit of detection, lower limit of quantification (LLOQ), linearity, accuracy and precision, stability, dilution integrity, recovery (RE), ME and process efficiency (PE). The LLOQs were 0.1 to 2.0 ng/mL, and determination coefficients of the calibration curve were above 0.9943 over the concentration ranges. The intra-and inter-day accuracy ranged from -10.4% to 9.9% and from -9.6% to 9.4%, while the intra-and inter-day precision were within 10.7% and 9.9%. The bench-top and long-term stability ranged from 92.1% to 109.5% and 88.7% to 111.6%, respectively. The reproducibility of auto-sampler stability was <10% for all analytes. The accuracy and precision of dilution integrity ranged from -11.7% to 10.5% and 0.4% to 9.9%, respectively. The relative standard deviation of RE and ME was from 0.6% to 6.6% and 0.5% to 3.9%, respectively, while that of PE was 1.3% to 4.5%. The developed LC-MS-MS method for medication compliance monitoring was successfully applied to urine samples from mentally disordered probationers and determined to be one of effective ways for preventing the recurrence of mentally disordered crimes.

A powerful on line ABTS+\u2013CE-DAD method to screen and quantify major antioxidants for quality control of Shuxuening Injection

A novel method of on-line 2,2′-Azinobis-(3-ethylbenzthiazoline-6-sulphonate)-Capillary Electrophoresis-Diode Array Detector (on-line ABTS+-CE-DAD) was developed to screen the major antioxidants from complex herbal medicines. ABTS+, one of well-known oxygen free radicals was firstly integrated into the capillary. For simultaneously detecting and separating ABTS+ and chemical components of herb medicines, some conditions were optimized. The on-line ABTS+-CE-DAD method has successfully been used to screen the main antioxidants from Shuxuening injection (SI), an herbal medicines injection. Under the optimum conditions, nine ingredients of SI including clitorin, rutin, isoquercitrin, Quercetin-3-O-D-glucosyl]-(1-2)-L-rhamnoside, kaempferol-3-O-rutinoside, kaempferol-7-O-β-D-glucopyranoside, apigenin-7-O-Glucoside, quercetin-3-O-[2-O-(6-O-p-hydroxyl-E-coumaroyl)-D-glucosyl]-(1-2)-L-rhamnoside, 3-O-{2-O-[6-O-(p-hydroxyl-E-coumaroyl)-glucosyl]}-(1-2) rhamnosyl kaempfero were separated and identified as the major antioxidants. There is a linear relationship between the total amount of major antioxidants and total antioxidative activity of SI with a linear correlation coefficient of 0.9456. All the Relative standard deviations of recovery, precision and stability were below 7.5%. Based on these results, these nine ingredients could be selected as combinatorial markers to evaluate quality control of SI. It was concluded that on-line ABTS+-CE-DAD method was a simple, reliable and powerful tool to screen and quantify active ingredients for evaluating quality of herbal medicines.

Determination of Five Major 8-Prenylflavones in Leaves of Epimedium by Solid-Phase Extraction Coupled with Capillary Electrophoresis.

A simple, accurate and reproducible method which is based on the capillary electrophoresis, coupled with solid-phase extraction, has been developed for simultaneous determination of multiple 8-prenylflavones from Chinese Herba Epimedii. In this study, the author has mainly illustrated the experimental process and research results of five major components including epimedin C, icariin, diphylloside A, epimedoside A and icarisoside A that have been extracted and identified from Herba Epimedii for the first time. Experimental conditions have been optimized to achieve the best separation efficiency for the following factors: the buffer pH, buffer concentration and applied voltage. The experiment can be conducted through two separable stages: the first stage is to obtain the crude extracts through the solid-phase extraction; and the second stage is to further separate five major components by using the capillary electrophoresis. The separation of the five components and the analysis of the experiment are relatively fast and can be completed within 20 min. The concentration ranges of the construction of standard curves of five major 8-prenylflavones are 32.0-395.0, 23.4-292.0, 42.1-526.0, 18.8-233.5 and 29.7-371.0 µg mL(-1) respectively, which have showed acceptable linearity with a correlation coefficient, r ≥ 0.999. The coefficient varies within 2.0% for both intra- and inter-days tests. The recoveries of five components range from 92.3 to 104.1%. The relative standard deviations of recoveries of five components range from 1.2 and 2.8%. This new method will facilitate the extraction and expedite the determination of medical components from Herba Epimedii.

Simultaneous separation of chlorinated/brominated dioxins, polychlorinated biphenyls, polybrominated diphenyl ethers and their methoxylated derivatives from hydroxylated analogues on molecularly imprinted polymers prior to gas/liquid chromatography and mass spectrometry

Polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs), polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) are important contaminants in the environment. In recent years also polybrominated dibenzo-p-dioxins/dibenzofurans (PBDD/Fs) have been reported as emerging environmental stressors. It has been suggested that hydroxylated polybrominated biphenyl ethers (OH-BDEs) are important – may be even the most important – precursors of brominated dioxins/furans. The aim of this study was to develop a robust, time-saving analytical procedure to collectively separate in animal tissues such compounds prior to determination of individual substances with a gas/liquid chromatograph coupled to an ion trap/time-of-flight mass spectrometer (GC/IT-MS or UPLC/TOF-MS). Two OH-CB/BDE separation methods including alkaline extraction and molecularly imprinted polymers (MIP) were compared. Performance of both methods was validated: absolute recovery values were in the 47–90% range depending on the compound, while recovery relative standard deviation was below 20% in most cases. Levels of the studied compounds have been assessed in some real life samples.

An ultra high performance liquid chromatography with tandem mass spectrometry method for plasma and cerebrospinal fluid pharmacokinetics of rhein in patients with traumatic brain injury after administration of rhubarb decoction.

Damage of blood-brain barrier is a common result of traumatic brain injury. This damage can open the blood-brain barrier and allow drug passage. An ultraperformance liquid chromatography with tandem mass spectrometry method was established to determine the concentration of rhein in the biofluids (plasma and cerebrospinal fluid) of patients with a compromised blood-brain barrier following traumatic brain injury after rhubarb administration. Furthermore, the pharmacokinetic profiles were analyzed. A triple-quadruple tandem mass spectrometer with electrospray ionization was used for rhein detection. The mass transition followed was m/z 283.06→239.0. The calibration curve was linear in the concentration range of 10-8000 ng/mL for the biofluids. The intra- and interday precisions were less than 10%. The relative standard deviation of recovery was less than 15% in biological matrices. The pharmacokinetic data showed that rhein was rapidly transported into biofluids, and exhibited a peak concentration 1 h after rhubarb administration. The elimination rate of rhein was slow. The AUCcerebrospinal fluid /AUCplasma (AUC is area under curve) of rhein was approximately 17%, indicating that portions of rhein could pass the impaired blood-brain barrier. The method was successfully applied to quantify rhein in the biofluids of all patients. The data presented can help to guide clinical applications of rhubarb for treating traumatic brain injury.

Determination of Explosives in Water Using Disposable Pipette Extraction and High Performance Liquid Chromatography

The use of disposable pipette extraction was examined for the simple and rapid determination of seven high explosives (cyclotrimethyl-enetrinitramine, cyclotetramethyl-enetetranitramine, 2,4,6-trinitrophenyl-methylnitramine, 2,4,6-trinitrotoluene, 2,4-dinitrotoluene, nitroglycerin, and pentaerythritol tetranitrate) in water. The current study involved the determination of slightly polar and nonpolar explosives in water with a reversed phase sorbent followed by high performance liquid chromatography. The method was based on a styrene divinylbenzene sorbent loosely placed inside a 5-mL pipette tip. Water samples were drawn into the tip and mixed with the sorbent. Air bubbles were also drawn through the tip following sample solution to enhance mixing. Because disposable pipette extraction uses small amounts of sorbent, minimal solvent is required to elute analytes and solvent evaporation is not necessary. The method provided rapid sample preparation, and required less than five minutes to extract 1.0 mL of water sample in the current study. Matrix-matched calibration was performed, and the limits of detection (LOD) were determined to be below 0.1 µg mL−1 for all targeted explosives in water with an enrichment factor of two. Coefficients of determination (r2) were greater than 0.9990 for all studied explosives, and the recoveries ranged from 69.76% to 87.51%, 83.77% to 91.25%, and 83.62% to 98.99% for samples spiked at 0.25 µg mL−1, 1.0 µg mL−1, and 5.0 µg mL−1, respectively. The relative standard deviations of recoveries at all spiked levels were below 8.97%. These results indicate that the disposable pipette extraction method provided good accuracy and precision for the determination of explosives in water.

Determination of hydroxysafflor yellow A in biological fluids of patients with traumatic brain injury by UPLC‐ESI‐MS/MS after injection of Xuebijing

A simple, novel, specific, rapid and reproducible ultra-performance liquid chromatography electrospray ionization tandem mass spectrometry method has been developed and validated for the determination of hydroxysafflor yellow A (HSYA) in biological fluids (plasma, urine and cerebrospinal fluid) of patients with traumatic brain injury after intravenous injection of Xuebijing (XBJ). Liquid-liquid extraction was performed, and separation was carried out on an Acquity UPLC™ BEH C18 column, with gradient elution using a mobile phase composed of methanol and 0.1% formic acid at a flow rate of 0.3 mL/min. A triple quadrupole tandem mass spectrometer with electrospray ionization was used for the detection of HSYA. The mass transition followed was m/z 611.0 → 491. The retention time was less than 3.0 min. The calibration curve was linear in the concentration range from 2 to 6125 ng/mL for cerebrospinal fluid, plasma and urine. The intra- and inter-day precisions were <10%, and the relative standard deviation of recovery was <15% for HSYA in biological matrices. The method was successfully applied for the first time to quantify HSYA in the biological fluids (especially in cerebrospinal fluid) of patients with traumatic brain injury following intravenous administration of XBJ.

Separation and adsorption properties of poly styrene‐graft‐ethyl methacrylate copolymer for zinc, copper, and cobalt ions in water samples

In this article, separation and adsorption properties of poly styrene‐graft‐ethyl methacrylate copolymer for zinc, copper, and cobalt ions in water samples were investigated. For this aim, some experimental and analytical parameters such as solution pH, sample flow rate, type of eluting agent, and sample solution volume were optimized. The adsorbed metal ions on polymeric resin were eluted with 5 ml of 2 mol l−1 HNO3 and they were determined by flame atomic absorption spectrometry. In optimized conditions, the adsorption capacities for Zn, Cu, and Co were obtained as 6.8, 5.2, and 7.5 mg g−1, respectively. The detection limits were calculated as 0.82 μg l−1 for Zn, 1.24 μg l−1 for Cu, and 0.68 μg l−1 for Co from standard deviation of the blank (50 ml, pH 5.8) measurements 10 replicates. The relative standard deviation of recoveries for seven replicate analyses of Zn, Cu, and Co ions (50 ml of 0.10 mg l−1) were found as 2.4, 2.8, and 1.5%, respectively. The accuracy of method was checked with certified reference material (NIST SRM 1643e, trace elements in water) and the developed method was successfully applied to tap water, commercial drinking water, and mineral water samples. POLYM. ENG. SCI., 54:1555–1559, 2014. © 2013 Society of Plastics Engineers

Silica chemically bonded N-propyl kriptofix 21 and 22 with immobilized palladium nanoparticles for solid phase extraction and preconcentration of some metal ions

Silica gel chemically bonded N-propyl kriptofix 21 (SBNPK 21) and N-propyl kriptofix 22 (SBNPK 22) and subsequently immobilized with palladium nanoparticles (PNP-SBNPK 21 and PNP-SBNPK 22) to produce two new complexing lipophilic materials. Then these novel sorbents were applied for the enrichment of some metal ions and their subsequent determination by flame atomic absorption spectroscopy (FAAS). The influences of the variables including pH, amount of solid phase, sample flow rate, eluent conditions and sample volume on the metal ion recoveries were investigated. The detection limit of proposed method was in the interval 2.1–2.3 and 1.7–2.8ngmL−1 for PNP-SBNPK 21 and PNP-SBNPK 22 respectively, while the preconcentration factor was 80 for two sorbents. The relative standard deviations of recoveries were between 1.23–1.31 and 1.28–1.49 for PNP-SBNPK 21 and PNP-SBNPK 22 respectively. The method has high sorption-preconcentration efficiency even in the presence of various interfering ions. Due to the reasonable selectivity of proposed method, the relative standard deviation of recoveries of all understudied metal ions in some complicated matrices was less than 3.0%.

Determination of perfluorinated compounds in environmental water samples by high-performance liquid chromatography-electrospray tandem mass spectrometry using surfactant-coated Fe 3O 4 magnetic nanoparticles as adsorbents

A novel method was developed for solid-phase extraction (SPE) of perfluorinated compounds (PFCs) from environmental water samples using cetyltrimethylammonium bromide (CTAB) coated Fe 3O 4 nanoparticles (Fe 3O 4 NPs) as an adsorbent. The magnetic nanosized adsorbent has a large surface area and superparamagnetic properties. This gives it a high extraction capacity and allows for convenient isolation by a magnetic field. Compared with other SPE methods and our previous work on PFCs, this method exhibited a fairly good analytical performance and required a small amount of sorbent (50 mg) and short pretreatment times (30 min) for 800 mL environmental water samples. Seven PFCs, including perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluoroundecanoic acid (PFUnDA), perfluorododecanoic acid (PFDoDA), and perfluorotetradecanoic acid (PFTA), extracted by the optimized method were determined by high-performance liquid chromatography-electrospray tandem mass spectrometry (HPLC/ESI-MS/MS). A concentration factor of 1600 was achieved when extracting 800 mL of several environmental water samples. Detection limits obtained for PFOA, PFOS, PFNA, PFDA, PFUnDA, PFDoDA and PFTA were 0.14, 0.022, 0.31, 0.23, 0.11, 0.16, 0.091 ng/L, respectively. The relative standard deviations of recoveries ranged from 1 to 8%, indicating good method precision.

Non-dioxin-like and dioxin-like polychlorinated biphenyls in butter sampled from the Polish retail market

The aim was to investigate levels of polychlorinated biphenyls (PCBs) in butter available on the Polish retail market. A gas chromatography-based method was developed for the purpose of this study. An ion-trap mass spectrometer was used as a detection system with high-resolution chromatography. Recoveries of individual PCBs from spiked samples varied from 58% to 105% with a recovery relative standard deviation in the range 3–16%. Levels of eight non-dioxin-like and twelve dioxin-like congeners were determined. Toxic equivalent factors (TEQs) were calculated using World Health Organization (WHO) TEQs. The average concentration of the sum of six PCBs (28, 52, 101, 138, 153, and 180) was found to be 1561 ± 728 pg g−1 (fat) and the upper-bound concentrations of dioxin-like congeners were (1 standard deviation uncertainty) 0.441 ± 0.384 pg PCB-TEQ g−1 (fat).

High Performance Liquid Chromatography Assay for p-Nitroanisole o-Demethylation by Cytochrome P450 Enzymes in Musca domestica L.

Abstract A novel sensitive method was developed for measuring p -nitroanisole o -demethylation (PNOD) catalyzed by cytochrome P450 enzymes in crude homogenates of housefly, Musca domestica L., using high performance liquid chromatography (HPLC) with diode array detector. This method is based on the use of liquid-liquid extraction and HPLC with reversed-phase C 18 column and gradient ultraviolet detection at 316 nm. The detection limit ( S/N of 3/1) of p -nitrophenol ( p NP) was 0.1 ng. The relative standard deviation (RSD) of peak area response of the HPLC analysis system was 1.0%. The average recoveries of 0.351, 1.755 and 8.755 μg of p NP added to incubation mixtures ranged from 92.3% to 87.6%, and the RSD of recoveries of three added levels ranged 2.64%–5.90%. The relationships between peak areas and concentration were linear in the range of 9.72–486 ng with good coefficient of determination ( r 2 = 0.9995). This method is sensitive, precise, and reproducible and is also applicable to the assay of p -nitroanisole o -demethylases, which have low catalytic activities, present in other insects or organisms. With this method, the comparison of P450 o -demethylation activity of an imidacloprid-resistant strain with a susceptible strain of M. domestica (L.) was conducted to identify the roles of P450 enzymes involved in housefly resistance to imidacloprid. The results indicated that the resistance mechanism of housefly to imidacloprid was intensely assisted with elevated P450 activities.

Determination of malachite green and leucomalachite green residues in water using liquid chromatography with visible and fluorescence detection and confirmation by tandem mass spectrometry

A liquid chromatography with visible and fluorescence detection (LC–vis/FLD) method for screening and a liquid chromatography with mass spectrometry (LC–MS/MS) method for the confirmation of malachite green (MG) and its major metabolite, leucomalachite green (LMG) residues in water have been described. Water samples were preconcentrated on diol solid-phase extraction columns. Chromatographic separation was achieved by using phenyl–hexyl column with an isocratic mobile phase consisting of acetonitrile and acetate buffer (0.05 M, pH 4.5) (70:30, v/v). In screening method liquid chromatography with absorbance detector was used for the detection of MG while LMG was detected by fluorescence detector. Detectors were connected on-line that allowed direct analysis of a sample extract for MG and LMG without the need of any post-column procedure. For the confirmation of MG and LMG in water positive electrospray ionization mass spectrometry in the multiple reaction monitoring mode was used. The developed methods have been validated according to the European Union requirements (Commission Decision 2002/657/EC). For LC–vis/FLD the mean recoveries at three fortification levels (0.4, 1, and 2 μg l −1) were in the range 95.4–104.7% for MG and 62.2–81.9% for LMG, whereas for LC–MS/MS, recoveries of MG and LMG were in the range 96.9–101.3% and 97.5–104.0%, respectively. Relative standard deviations of recoveries for both methods were less than 3.8 and 8.1% for MG and LMG, respectively. The stability of MG and LMG at 4 °C in darkness was observed for at least 10 months. Moreover, photo-oxidative decomposition products of analytes in water samples, observed in stability tests carried out at 20 °C, were identified by mass spectrometry as N-demethylated products of MG and LMG. These findings prove that N-demethylated products of MG and LMG, reported as potential carcinogens, may be formed in living fish organisms not only during enzymatic action but also during photo-oxidative degradation in water.

Determination of perfluorinated compounds in wastewater and river water samples by mixed hemimicelle-based solid-phase extraction before liquid chromatography–electrospray tandem mass spectrometry detection

A comparative study on the use of cetyltrimethylammonium bromide (CTAB)-coated silica and sodium dodecyl sulphate (SDS)-coated alumina mixed hemimicelles-based solid-phase extraction (SPE) for the pre-concentration of six perfluorinated compounds (PFCs) in environmental water samples was presented. The six analytes heptafluorobutyric acid (HFBA), perfluoroheptanic acid (PFHeA), perfluorooctanic acid (PFOA), perfluorooctanic sulfonic (PFOS), perfluorononanic acid (PFNA) and perfluorodecanic acid (PFDeA) were quantitatively retained on both sorbent materials. The cationic surfactant (CTAB adsorbed onto silica) was more appropriate for SPE of PFCs. The main factors affecting adsolubilization of PFCs including the amount of surfactant, pH of solution, sample loading volume and desorption were investigated and optimized. Concentration factor of 500 were achieved by SPE of 500 mL of several environmental water samples. The method detection limits obtained for HFBA, PFHeA, PFOA, PFOS, PFNA and PFDeA were 0.10, 0.28, 0.07, 0.20, 0.10 and 0.05 ng/L, respectively. The relative standard deviation of recoveries ranged from 2 to 8%, which indicated good method precision.

HPLC-UV Method for Nicotine, Strychnine, and Aconitine in Dairy Products

The toxic nitrogen alkaloids nicotine, strychnine, and aconitine were quantitated in whole milk, skim milk, and cream using solid-phase extraction cleanup and HPLC-UV with dual wavelength detection. Samples were extracted in McIlvaine's buffer with EDTA and then partitioned with aqueous acetonitrile and hexane. The aqueous phase was concentrated and passed through an OASIS HLB column. The column was eluted with methylene chloride/ammonium hydroxide, 1 mL/1 microL, v/v. The eluent was acidified with hydrochloric acid and evaporated. The sample was diluted for HPLC with acetonitrile/phosphate buffer pH 7.4. Chromatography was performed on an Xterra RP-18 column using a gradient of acetonitrile and ammonium bicarbonate buffer at pH 9.8. Nicotine and strychnine were monitored at 260 nm; aconitine was monitored at 232 nm. Calibration curves were generated from external standards in the range 0.2-10 microg/mL using 1/x weighting. Mean recoveries in whole milk spiked between 0.1 and 10 ppm were the following: nicotine 89.2%, strychnine 75.7%, and aconitine 85.1%. Mean recoveries in skim milk spiked between 0.1 and 10 ppm were the following: nicotine 72.1%, strychnine 78.2%, and aconitine 82.9%. Mean recoveries in cream spiked between 0.2 and 20 ppm were the following: nicotine 87.9%, strychnine 76.9%, and aconitine 82.0%. Relative standard deviations of recovery were less than 20% in each case.

New method for determination of ochratoxin A in beer using zinc acetate and solid-phase extraction silica cartridges

A new method for the determination of ochratoxin A (OTA) in beer has been developed. The new method has been compared with a reference method currently accepted as AOAC official first action. The limits of detection and quantification of the proposed method were 0.0008 and 0.0025 ng/ml, respectively, while they were 0.0025 and 0.0075 ng/ml, respectively, in the AOAC method used as reference. The recovery levels in the 0.025–0.40 ng OTA/ml spiking range for the proposed and the reference methods were 80.6–87.6% and 78.2–83.8%, respectively. The relative standard deviations of recoveries were 2.6–7.5% for the proposed method and 0.7–6.1% for the reference method. Passing and Bablok regression analysis of recovery data obtained by the proposed method versus data obtained by the reference method on an OTA-spiked beer sample showed good correlation ( r 2 = 0.9993), while the slope and intercept were 1.049 and −0.0013, respectively. The advantage of the proposed method is the low cost of the materials used in sample preparation because expensive immunoaffinity columns are not needed to clean-up samples while it maintains or even increases the good performance of the reference method. The proposed method was applied to 69 beer samples from different geographic origins (national and imported) but purchased in the Spanish market. They were found to be contaminated with OTA in the range from 0.008 to 0.498 ng/ml (average: 0.070 ng/ml). Five samples surpassed the limit recommended by the European Union (0.2 ng OTA/g).

Gas Chromatographic–Mass Spectrometric Method for Quantitation of Trimethylsilyl Derivatives of Nerve Agent Degradation Products in Human Plasma, Using Strong Anion–Exchange Solid-Phase Extraction

For unequivocal proof of the use of nerve agents such as sarin, soman, cyclohexylsarin, VX, and Russian VX, a simple and accurate method, gas chromatography–mass spectrometry (GC–MS) after trimethylsilyl derivatization, was explored for simultaneous determination of the corresponding alkyl methylphosphonic acids (AMPAs) and of methylphosphonic acid (MPA) in human plasma. GC–MS analysis was performed after solid-phase extraction, with a strong anion-exchange cartridge, from plasma samples previously deproteinized with mercuric acetate, and then derivatization with bis(trimethylsilyl)trifluoroacetamide containing 5% trimethylchlorosilane. All five AMPA derivatives and the MPA derivative were separated to baseline within 11 minutes without interference. Linear calibration plots were obtained over concentrations ranging from 50 ng mL−1 to 5 µg mL−1. The relative standard deviation of recoveries ranged from 1.9 to 9.7% and detection limits were 22 ng mL−1 or below.

Determination of Trace Cadmium in Waters by Flame Atomic Absorption Spectrophotometry After Preconcentration with 1‐Nitroso‐2‐Naphthol‐3, 6‐Disulfonic Acid on Ambersorb 572

A procedure for the determination of trace amount of cadmium after adsorption of its 1-nitroso-2-naphthol-3,6-disulfonic acid chelate on Ambersorb 572 has been proposed. This chelate is adsorbed on the adsorbent in the pH range 3-8 from large volumes of aqueous solution of water samples with a preconcentration factor of 200. After being sorbed, cadmium was eluted by 5 mL of 2.0 mol L(-1) nitric acid solution and determined directly by flame atomic absorption spectrophotometery (FAAS). The detection limit (3sigma) of cadmium was 0.32 microg L(-1). The precision of the proposed procedure, calculated as the relative standard deviation of recovery in sample solution (100 mL) containing 5 microg of cadmium was satisfactory (1.9%). The adsorption of cadmium onto adsorbent can formally be described by a Langmuir equation with a maximum adsorption capacity of 19.6 mg g(-1) and a binding constant of 6.5 x 10(-3) L mg(-1). Various parameters, such as the effect of pH and the interference of a number of metal ions on the determination of cadmium, have been studied in detail to optimize the conditions for the preconcentration and determination of cadmium in water samples. This procedure was applied to the determination of cadmium in tap and river water samples.