Anion Exchange Solid Phase Extraction Research Articles

High-performance liquid chromatography — Ultraviolet method for the determination of total specific migration of nine ultraviolet absorbers in food simulants based on 1,1,3,3-Tetramethylguanidine and organic phase anion exchange solid phase extraction to remove glyceride

The glyceride in oil food simulant usually causes serious interferences to target analytes and leads to failure of the normal function of the RP-HPLC column. In this work, a convenient HPLC-UV method for the determination of the total specific migration of nine ultraviolet (UV) absorbers in food simulants was developed based on 1,1,3,3-tetramethylguanidine (TMG) and organic phase anion exchange (OPAE) SPE to efficiently remove glyceride in olive oil simulant. In contrast to the normal ion exchange carried out in an aqueous solution or aqueous phase environment, the OPAE SPE was performed in the organic phase environments, and the time-consuming and challenging extraction of the nine UV absorbers from vegetable oil with aqueous solution could be readily omitted. The method was proved to have good linearity (r≥0.99992), precision (intra-day RSD≤3.3%), and accuracy(91.0%≤recoveries≤107%); furthermore, the lower limit of quantifications (0.05–0.2mg/kg) in five types of food simulants(10% ethanol, 3% acetic acid, 20% ethanol, 50% ethanol and olive oil) was observed. The method was found to be well suited for quantitative determination of the total specific migration of the nine UV absorbers both in aqueous and vegetable oil simulant according to Commission Regulation (EU) No. 10/2011. Migration levels of the nine UV absorbers were determined in 31 plastic samples, and UV-24, UV-531, HHBP and UV-326 were frequently detected, especially in olive oil simulant for UV-326 in PE samples. In addition, the OPAE SPE procedure was also been applied to efficiently enrich or purify seven antioxidants in olive oil simulant. Results indicate that this procedure will have more extensive applications in the enriching or purification of the extremely weak acidic compounds with phenol hydroxyl group that are relatively stable in TMG n-hexane solution and that can be barely extracted from vegetable oil.

Determination of baicalin in cosmetics and toothpaste by solid-phase extraction and high-performance liquid chromatography

ABSTRACTBaicalin was determined in cosmetics and toothpaste by high-performance liquid chromatography. The samples were extracted with ultrasound in 75% ethanol for 20 min, purified by anion exchange solid-phase extraction cartridge, and the components were separated on a C18 column. The limits of detection and quantification were 3.0 mg kg−1 and 10.0 mg kg−1. The recovery was from 81.3–101.6%. A linear relationship was present from 1.00–100 µg · mL−1 of baicalin. The protocol was simple, sensitive, selective, and used to determine baicalin in personal care products. Baicalin was not present in materials contrary to the labeled contents.

Determination of Acidic Dyes in Pharmaceutical Capsules by Solid-Phase Extraction and High-Performance Liquid Chromatography

ABSTRACTA rapid and simple method was established for the determination of acidic dyes in pharmaceutical capsules using solid-phase extraction and high-performance liquid chromatography with a diode array detector. The capsules were dissolved in water using an ultrasonic bath at 55 ± 5°C, and pH was adjusted to 1 with 0.2 mol/L hydrochloric acid. The resulting solution was purified using a weak anion exchange solid-phase extraction cartridge. Chromatographic separation was performed on a reversed phase C18 column with gradient elution using acetonitrile and 20 mmol/L aqueous ammonium acetate (pH = 4.5) as the mobile phase. The chromatography was monitored at 420, 480, 520, and 600 nm. Under the optimized conditions, the recoveries of the analytes were from 60.5 ± 1.59 to 99.1 ± 0.84%. The intraday and interday relative standard deviations were from 0.29 to 10.6% and from 1.08 to 10.8%, respectively. The limits of quantification were between 0.11 and 0.50 µg/g.

Liquid chromatography coupled to tandem mass spectrometry for the analysis of inositol hexaphosphate after solid-phase extraction

ABSTRACTInositol hexaphosphate, a naturally occurring component in cereals and plants, is the main reserve and principal carrier of phosphate. Inositol hexaphosphate is also found in biological fluids such as urine, plasma, or whole blood. Moreover, inositol hexaphosphate is studied for its pharmaceutical applications. Liquid chromatography coupled to mass spectrometry is now the reference method for small analyte determination. However, the specific quantitation of polyanionic molecules in the biological matrix is still challenging.In this article, a bioanalytical method for the extraction and determination of inositol hexaphosphate in whole blood is described by using solid-phase extraction followed by liquid chromatography–mass spectrometry/mass spectrometry using selected reaction monitoring mode for its specificity.Using pentylamine in excess, an ion pair is created, enhancing sensitivity by avoiding the presence of many Na adducts on the phosphate functions of inositol hexaphosphate. Moreover, hexafluoroisopropanol was added to stabilize the ion pairs that were created. Then, a specific extraction of inositol hexaphosphate by anion-exchange solid-phase extraction was developed, resulting in an extraction recovery of 89%. The linearity of the method was verified between 0.78 and 100 µg/mL, and both accuracy and precision were greater than 85%. Finally, the endogenous rate of inositol hexaphosphate was measured in the whole blood of mice and was estimated at 2 µg/mL.

Simultaneous qualitative and quantitative analysis of fluoroalkyl sulfonates in riverine water by liquid chromatography coupled with Orbitrap high resolution mass spectrometry

In this study, a robust method for quick screening, confirmation and quantification analysis of eight fluoroalkyl sulfonates in surface riverine samples was developed using ultra-high performance liquid chromatography-high resolution mass spectrometer (LC-Orbitrap Tribrid HRMS). Weak anion exchange solid phase extraction was optimized to maximum recover perfluoroalkyl sulfonates (PFSAs), fluorotelomer sulfonates and the emerging 6:2 chlorinated polyfluoroalkyl ether sulfonate at the same time. Both qualitative and quantitative purposes could be achieved by simultaneous acquiring full-scan mass spectrum (MS1) and data-dependent MS2 data. The LC-Orbitrap Tribrid HRMS method showed competent method detection limits for all analytes (7.1–62pg/L) compared with the triple quadrupole mass spectrometry (LC–MS/MS) quantification method (12–54pg/L), and satisfactory method validation results were also obtained in linearity (R2>0.999), trueness (88–118%), precision (2–17%) and recovery (63–103%). A good correlation (R>0.999) was found between the sets of quantified PFSA residue concentrations in thirteen estuary river samples by both the LC-Orbitrap Tribrid HRMS (0.2–440ng/L) and LC–MS/MS (0.1–424ng/L) methods, indicating that Orbitrap Tribrid HRMS could be used for reliable quantitative analysis purpose. Moreover, the LC-Orbitrap Tribrid HRMS method could also benefit from its high mass resolution characteristic to eliminate potential environment interferents (e.g., taurodeoxycholate) and to quantify all PFSA isomers based on full-scan MS1 chromatogram at a narrow MS window (5 part per million).

Trace enrichment and characterization of polyphenols in Bistort Rhizoma using weak anion-exchange solid phase extraction and high performance liquid chromatography-quadrupole time-of-flight mass spectrometry

The analysis of trace constituents in herbal medicines has always been a challenge due to complex matrices and structural diversities. In this work, a pH-sensitive solid phase extraction (SPE) procedure capable of enriching trace polyphenols in Bistort Rhizoma (BR) was proposed and preliminary chemical characterization was accomplished by high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (HPLC-QTOF MS). A weak anion-exchange SPE column packed with divinylbenzene/vinylpyrrolidone bonding quaternary amine group was employed for anionic extraction, and the target fraction was obtained by eluting with acidic methanol (apparent pH 1.9). On the other hand, the MS/MS fragmentation rules of four reference polyphenols in negative ion mode were outlined. Using these rules, a total of 31 polyphenols including 20 benzoyl derivatives and 11 caffeoyl derivatives were screened out from BR extract, of which 26 trace members were found for the first time in this herb. Those findings demonstrated that the anion-exchange SPE could enhance the detection capability and selectivity for plant polyphenols in the LC–MS analysis and the strategy for deducing structures could be applied for analysis of polyphenols in BR and other herbal medicines.

Determination of organophosphate diesters in urine samples by a high-sensitivity method based on ultra high pressure liquid chromatography-triple quadrupole-mass spectrometry

Organophosphate (OP) diesters in urine samples have potential use as biomarkers of organism exposure to environmentally relevant OP triester precursors and in particular OP triester flame retardants. This present study developed a quantitatively sensitive ultra high pressure liquid chromatography (UHPLC–MS) based method for urine and the determination of OP diesters (i.e. diphenyl phosphate (DPHP), bis(2-chloroethyl) phosphate (BCEP), bis(2-chloroisopropyl) phosphate (BDCIPP), di-n-butyl phosphate (DNBP), di(2-ethylhexyl) phosphate (DEHP), bis(1-chloro-2-propyl) phosphate (BCIPP), and bis(2-butoxyethyl) phosphate (BBOEP)). Fortified with the 7 OP diesters, 1mL of human urine sample was cleaned up using weak anion exchange solid phase extraction and eluted with high ionic strength ammonium acetate buffer. Subsequently, 4 non-chlorinated OP diesters were directly determined using UHPLC–electrospray(−)-triple quadrupole–MS (UHPLC–ESI(−)–QqQ–MS), and UHPLC–ESI(+)–QqQ–MS was used for determination of 3 chlorinated OP diesters after methylation using diazomethane. Recovery efficiencies of OP diesters ranged from 88 to 160% at three spiking levels (0.4, 2 and 10ng/mL urine). Matrix effects (MEs) and method limits of quantification (MLOQs) were 15-134% and 0.10–0.32ng/mL urine, respectively. Concentrations of OP diesters in n=12 urine samples (from 4 Canadian residents, 2014) varied as follows, nd-<0.28 (DNBP), nd-1.29 (DPHP), nd-<0.28 (DEHP), <0.16–12.33 (BCEP), nd-1.17 (BCDIPP) and nd-0.68ng/mL (BCIPP).

Determination of Methamphetamine and Amphetamine in Hair by Mixed-Mode Anion Exchange Solid Phase Extraction and Liquid Chromatography–Tandem Mass Spectrometry

Methamphetamine is one of the most widely used sympathomimetic amines in Asia. To identify cases of methamphetamine abuse and to estimate its abuse, hair segmental analysis is used extensively. However, existing hair analysis has several limitations due to matrix interferences. In an attempt to resolve these issues, a simple, rapid, and sensitive liquid chromatography–tandem mass spectrometry method is reported for the determination of methamphetamine and amphetamine in human hair with anion exchange solid phase extraction. Hair dissolved in sodium hydroxide was loaded on a mixed-mode anion exchange cartridge and amphetamine and methamphetamine were eluted with methanol in less than ten minutes followed by liquid chromatography–tandem mass spectrometry. The recovery of this method was between 93.9 and 102.0 percent. The limits of detection and quantitation were 0.01 and 0.05 nanograms per milligram for both analytes. The accuracy and precision were satisfactory for quantitative analysis. The suitability of the method for practical analysis was investigated using hair from methamphetamine users.

Determination of avibactam and ceftazidime in human plasma samples by LC-MS.

Avibactam, a novel non-β-lactam β-lactamase inhibitor co-administrated with the β-lactam antibiotic ceftazidime, is in clinical development. The need to evaluate its PK and PD requires accurate and reliable bioanalytical methods. We describe LC-MS/MS methods for the determination of avibactam and ceftazidime in human plasma. Avibactam was extracted using weak anionic exchange solid-phase extraction and analyzed on an amide column. Ceftazidime was extracted using protein precipitation and analyzed on a C18 column. Calibration curves were established over 10-10,000 ng/ml (avibactam) and 43.8-87,000 ng/ml (ceftazidime). Method validation, cross-validation between three laboratories and incurred sample re-analysis demonstrated method robustness. The methods were successfully applied to multiple clinical studies.

Selective removal of phosphate for analysis of organic acids in complex samples

Accurate quantitation of compounds in samples of biological origin is often hampered by matrix interferences one of which occurs in GC-MS analysis from the presence of highly abundant phosphate. Consequently, high concentrations of phosphate need to be removed before sample analysis. Within this context, we screened 17 anion exchange solid-phase extraction (SPE) materials for selective phosphate removal using different protocols to meet the challenge of simultaneous recovery of six common organic acids in aqueous samples prior to derivatization for GC-MS analysis. Up to 75% recovery was achieved for the most organic acids, only the low pKa tartaric and citric acids were badly recovered. Compared to the traditional approach of phosphate removal by precipitation, SPE had a broader compatibility with common detection methods and performed more selectively among the organic acids under investigation. Based on the results of this study, it is recommended that phosphate removal strategies during the analysis of biologically relevant small molecular weight organic acids consider the respective pKa of the anticipated analytes and the detection method of choice.

Overcoming stability challenges in the quantification of tissue nucleotides: determination of 2'-C-methylguanosine triphosphate concentration in mouse liver.

A conventional, rapid and high throughput method for tissue extraction and accurate and selective LC-MS/MS quantification of 2'-C-methylguanosine triphosphate (2'-MeGTP) in mouse liver was developed and qualified. Trichloroacetic acid (TCA) was used as the tissue homogenization reagent that overcomes instability challenges of liver tissue nucleotide triphosphates due to instant ischemic degradation to mono- and diphosphate nucleotides. Degradation of 2'-MeGTP was also minimized by harvesting livers using in situ clamp-freezing or snap-freezing techniques. The assay also included a sample clean-up procedure using weak anion exchange solid phase extraction followed by ion exchange chromatography and tandem mass spectrometry detection. The linear assay range was from 50 to 10000 pmol/mL concentration in liver homogenate (250-50000 pmol/g in liver tissue). The method was qualified over three intraday batches for accuracy, precision, selectivity and specificity. The assay was successfully applied to pharmacokinetic studies of 2'-MeGTP in liver tissue samples after single oral doses of IDX184, a nucleotide prodrug inhibitor of the viral polymerase for the treatment of hepatitis C, to mice. The study results suggested that the clamp-freezing liver collection method was marginally more effective in preventing 2'-MeGTP degradation during liver tissue collection compared to the snap-freezing method.

Measurement of intracellular ribavirin mono-, di- and triphosphate using solid phase extraction and LC-MS/MS quantification.

Ribavirin (RBV) is a nucleoside analog used to treat a variety of DNA and RNA viruses. RBV undergoes intracellular phosphorylation to a mono- (MP), di- (DP), and triphosphate (TP). The phosphorylated forms have been associated with the mechanisms of antiviral effect observed in vitro, but the intracellular pharmacology of the drug has not been well characterized in vivo. A highly sensitive LC-MS/MS method was developed and validated for the determination of intracellular RBV MP, DP, and TP in multiple cell matrix types. For this method, the individual MP, DP, and TP fractions were isolated from lysed intracellular matrix using strong anion exchange solid phase extraction, dephosphorylated to parent RBV, desalted and concentrated and quantified using LC-MS/MS. The method utilized a stable labeled internal standard (RBV-(13)C5) which facilitated accuracy (% deviation within ±15%) and precision (coefficient of variation of ≤15%). The quantifiable linear range for the assay was 0.50 to 200 pmol/sample. The method was applied to the measurement of RBV MP, DP, and TP in human peripheral blood mononuclear cells (PBMC), red blood cells (RBC), and dried blood spot (DBS) samples obtained from patients taking RBV for the treatment of chronic Hepatitis C virus infection.

Liquid chromatography-electrospray–tandem mass spectrometry method for determination of organophosphate diesters in biotic samples including Great Lakes herring gull plasma

Environmentally relevant organophosphate (OP) triester flame retardants are known to degrade to OP diester phosphoric acids. In this study, a quantitatively sensitive method was developed for OP diesters in biological samples of varying complexity, bovine serum, chicken egg homogenate and pork liver. Fortified with 1ng or 10ng each of the six OP diester and six OP triester standards, samples were extracted by accelerated solvent extraction that completely separated OP diesters and triesters. OP diester fractions were cleaned up using weak anion exchange solid phase extraction and eluted with high ionic strength ammonium acetate buffer. Optimal analysis of chlorinated OP diesters was via decamethonium hydroxide dicationic reagent derivatization and by LC-ESI(+)–MS/MS, and for all non-chlorinated OP diesters by non-derivatized LC-ESI(−)–MS/MS. Except for derivatization LC-ESI(+)–MS/MS analysis of liver, at the 10ng spiking level for the three matrices, recovery efficiencies, matrix effects and method limits of quantification (MLOQs) of OP diesters ranged from 55–116%, 92–119%, and 0.02–0.31ng/g wet weight (ww) respectively. Plasma samples of n=6 herring gulls (2010, Chantry Is., Laurentian Great Lakes) contained triphenyl phosphate and tris(1-3-dichloro-2-propyl) phosphate ranging from 1.3 to 4.0ng/g ww and <MLOQ to 0.41ng/g ww respectively. The OP diesters bis(1,3-dichloro-2-propyl) phosphate, bis-(2-butoxyethyl) phosphate and di(2-ethylhexyl) phosphate ranged from 0.7 to 3.5ng/g ww, 0.08 to 29.4ng/g ww and <MLOQ to 0.18ng/g ww respectively, and thus OP triester to diester metabolism occurs in exposed wild herring gulls.

Exposure assessment to ochratoxin A in Chinese wine.

A rapid, sensitive, reproducible, and inexpensive method of high-performance liquid chromatography with fluorescence detection after an anion-exchange solid-phase extraction cleanup step for the analysis of ochratoxin A (OTA) in Chinese wine was developed. The average recovery rate and the average RSD of recovery were 97.47% and about 4%. The relative standard deviations of both the interday and intraday precision were 6.7 and 12.6%, respectively. The limits of detection and quantitation were determined to be 0.01 and 0.03 μg/L, respectively. A total of 223 samples from the major wine-producing areas of China were analyzed for OTA. OTA was detected at levels of 0.01-0.98 μg/L. The mean was 0.15 μg/L. Then, participants as representative inhabitants were invited to answer the designed questionnaire about the quantity and frequency of wine consumption. All data were simulated by the point evaluation for the risk assessment of OTA contamination from wine. Those results indicated that daily intake (DI) of OTA for the average adult consumer varies between 0.86 and 1.08 ng/kg bw per week, which was lower than all the reference standards. However, the DI value (4.38-5.54 ng/kg bw per week) in the high percentile (97.5) was slightly above 5% PTWI (100 ng kg(-1) week(-1)) of the JECFA. In conclusion, OTA exposure from Chinese wine has no risk of harm. This research will provide the scientific basis for determining the maximum limit of OTA content in Chinese wine.

Determination of nine phthalate ester metabolites in human urine using ultra high performance liquid chromatography-tandem triple quadrupole mass spectrometry

A method was developed to determine trace concentrations of phthalate ester (PAE) metabolites in human urine by using ultra high performance liquid chromatography-triple quadrupole mass spectrometry. Aliquots (2 mL) of human urine samples were purified using strong anion-exchange solid-phase extraction after enzymatic deconjugation by glucuronidase for 2 h. The separation was performed on a Waters ACQUITY UPLC BEH Phenyl column (100 mm×2.1 mm, 1.7 μ m) with gradient elution by 0.1% (v/v) acetic acid in acetonitrile and 0.1% (v/v) acetic acid aqueous solution. The concentrations of nine PAE metabolites were determined under a multiple reaction monitoring mode by negative electrospray ionization. Eight of the determined metabolites showed good linearities in the range of 0.39-200 μ g/L, and the ninth metabolite showed linearity in the range of 1.17-600 μ g/L with correlation coefficients > 0.995. The limits of detection ranged from 0.06 to 0.85 μ g/L, and the limits of quantification ranged from 0.20 to 2.80 μ g/L. The recovery rates at all three spiked levels ranged from 84.1% to 122% with relative standard deviations between 4.5% and 14.3%. The intra-and inter-day precisions were not more than 10.1% and 9.3%, respectively. The matrix effect and stability were found to be favorable for analysis. This method was utilized for the determination of 50 human urine samples. The detection rates of monocyclohexyl phthalate (MCHP) and monobenzyl phthalate (MBZP) were 0 and 44.0%, and the detection rates of the other seven PAE metabolites was 100%. This method has the advantage of convenient operation and good accuracy and stability, and is suitable for the quantitative determination of the nine PAE metabolites in human urine.

On-line hyphenation of solid-phase extraction to chromatographic separation of sulfonamides with fused-core columns in sequential injection chromatography

On-line sample pretreatment (clean-up and analyte preconcentration) is for the first time coupled to sequential injection chromatography. The approach combines anion-exchange solid-phase extraction and the highly effective pentafluorophenylpropyl (F5) fused-core particle column for separation of eight sulfonamide antibiotics with similar structures (sulfathiazole, sulfanilamide, sulfacetamide, sulfadiazine, sulfamerazine, sulfadimidine, sulfamethoxazole and sulfadimethoxine). The stationary phase was selected after a critical comparison of the performance achieved by three fused-core reversed phase columns (Ascentis® Express RP-Amide, Phenyl-Hexyl, and F5) and two monolithic columns (Chromolith® High Resolution RP-18 and CN). Acetonitrile and acetate buffer pH 5.0 at 0.60mLmin−1 were used as mobile phase to perform the separations before spectrophotometric detection. The first mobile phase was successfully used as eluent from SPE column ensuring transfer of a narrow zone to the chromatographic column. Enrichment factors up to 39.2 were achieved with a 500µL sample volume. The developed procedure showed analysis time <10.5min, resolutions >1.83 with peak symmetry ≤1.52, LODs between 4.9 and 27µgL−1, linear response ranges from 30.0 to 1000.0µgL−1 (r2>0.996) and RSDs of peak heights <2.9% (n=6) at a 100µgL−1 level and enabled the screening control of freshwater samples contaminated at the 100µgL−1 level. The proposed approach expanded the analytical potentiality of SIC and avoided the time-consuming batch sample pretreatment step, thus minimizing risks of sample contamination and analyte losses.

고체상 추출과 친화 크로마토 그라피-유도결합 플라즈마 질량분석법을 이용한 한국인 혈청에서의 셀레노 단백질 정량

Interferences were removed using anion exchange solid phase extraction (AE SPE) in quantification of seleno proteins in korean human blood serum with affinity high performance liquid chromatography (AF HPLC)-inductively coupled plasma/mass spectrometry (ICP/MS). The average selenium level obtained for healthy koreans was 94.3 ± 2.3 ng g �1 using isotope dilution method. AE SPE was coupled to AF column to separate 3 selenoproteins, glutathione peroxidase (GPx), selenoprotein (SelP), and selenoalbumin (SeAlb). Post column isotope dilution was employed to quantify the proteins. The certified reference material of human blood serum, BCR-637, was analyzed to give total selenoprotein concentration of 85.4 ± 3.4 ng g �1 , which agreed well with the reference value of 81 ± 7 ng g �1 . The pooled concentration of GPx, SelP, and SeAlb from healthy koreans (n=20) was 12.1 ± 1.4 ng g �1 , 57.2 ± 2.0 ng g �1 , and 20.0 ± 1.9 ng g �1 , respectively. The sum of selenoproteins is 89.3 ng g �1 , which is about the same as the total selenium concentration of 94.3 ng g �1 . The fact suggests that selenium in blood serum is mostly consisted of selenoproteins. After the removal of interference, GPx showed a significant decrease (more than 50%) from 25.0 ng g �1 to 12.1 ng g �1 . It was identified that the interference in blood serum was mostly from GPx and the use of AE SPE was proven to be efficient in eliminating Cland Brthat cause interference to GPx. 요약 : 본 연구에서는 음이온 고체상 추출법 (AE SPE; anion exchange solid phase extraction)을 사용하 여 간섭요인을 제거한 후, 친화 크로마토그래피 AF HPLC; affinity high performance liquid chromatography) 와 유도결합 플라스마 질량분석법 (ICP/MS; inductively coupled plasma/mass spectrometry)을 사용하여 한

Optimization of solid phase extraction clean up and validation of quantitative determination of carbazochrome sodium sulfonate in human plasma by liquid chromatography-electrospray ionization tandem mass spectrometry

A mixed-mode anion exchange solid phase extraction (SPE) method for extraction and clean up of carbazochrome sodium sulfonate (CSS) and (1S)-(+)-10-camphorsulfonic acid (IS) was optimized for quantification by high-performance liquid chromatography/negative electrospray ionization mass spectrometry. The analytes were extracted from 1mL of human plasma via SPE on Oasis(®) WAX cartridge. Chromatographic separation was achieved on a Zorbax SB-Aq (4.6×250mm, 5μm) column under an isocratic condition. Detection was performed using electrospray ionization in negative ion multiple reaction monitoring (MRM) mode. The deprotonated precursor to product ion transitions monitored for CSS and IS was at m/z 299.0→256.0 and m/z 230.9→79.8, respectively. The method was fully validated for its selectivity, sensitivity, precision, accuracy, recovery, matrix effect and stability. Linear range was 0.189-37.8ng/mL with a high square regression coefficient (r=0.9995). The intra-and inter-day precision (RSD, %) ranged from 0.95% to 4.17%, and the intra-and inter-day accuracy was between 95.03% and 105.9%. This method was successfully applied to a bioequivalence study of 90mg CSS formulation in 18 healthy Chinese male subjects under fasting condition.

Determination of sesamol in sesame oil by anion exchange solid phase extraction coupled with HPLC

A novel, sensitive and reliable anion exchange SPE procedure method for cleanup and extraction of sesamol in sesame oil was developed.

Anion Exchange Solid-Phase Extraction Combined with High Performance Liquid Chromatography to Determine Bensulfuron Methyl in Wheat and Soil

Anion Exchange Solid-Phase Extraction Combined with High Performance Liquid Chromatography to Determine Bensulfuron Methyl in Wheat and Soil