固相微萃取-气相色谱/质谱分析栀子花的头香成分

 分别用固相微萃取和动态顶空法分离栀子鲜花的头香成分,用GC/MS技术分析鉴定,并用GC/MS总离子流色谱峰的峰面积进行归一化定量。在固相微萃取方法中,共鉴定了54种化学成分,占总峰面积的99.98%。主要成分(质量分数)依次为金合欢烯（64.86%）、罗勒烯（29.33%）、芳樟醇（2.74%）、惕各酸顺式叶醇酯（1.34%）和苯甲酸甲酯（0.25%）等。经与动态顶空法的分析结果比较发现,固相微萃取法不仅操作简便,而且具有较高的采样灵敏度,获得的化学成分的信息量多于动态顶空法。     

Determination of metolcarb and diethofencarb in apples and apple juice by solid-phase microextraction-high performance liquid chromatography

A method for the determination of metolcarb and diethofencarb in apples and apple juice is developed using solid-phase microextraction (SPME) coupled with high-performance liquid chromatography (HPLC). The experimental conditions of SPME, such as the kind of extraction fiber, extraction time, stirring rate, pH of the extracting solution, and desorption conditions are optimized. The SPME is performed on a 60 microm polydimethylsiloxane/divinylbenzene fiber for 40 min at room temperature with the solution being stirred at 1100 rpm. The extracted pesticides on the SPME fiber are desorbed in the mobile phase into SPME-HPLC interface for HPLC analysis. Separations are carried out on a Baseline C18 column (4.6 i.d. x 250 mm, 5.0 microm) with acetonitrile-water (55/45, v/v) as the mobile phase at a flow rate of 1.0 mL/min, and photodiode-array detection at 210 nm. For apple samples, the method is linear for both metolcarb and diethofencarb in the range of 0.05-1.0 mg/kg (r > 0.99), with a detection limit (S/N = 3 ) of 15 and 5 microg/kg, respectively. For apple juice, the method is linear for both metholcarb and diethofencarb over the range of 0.05-1.0 mg/L (r > 0.99) with the detection limit (S/N = 3 ) of 15 and 3 microg/L, respectively. Excellent recovery and reproducibility values are achieved. The proposed method is shown to be simple, sensitive, and organic solvent-free, and is suitable for the determination of the two pesticides in apples and apple juice.     

Rapid determination of C6-aldehydes in tomato plant emission by gas chromatography-mass spectrometry and solid-phase microextraction with on-fiber derivatization

A simple, rapid, sensitive, and solvent-free method was developed for determination of plant-signalling compounds, the three C6-aldehydes hexanal, (Z)-3-hexenal, and (E)-2-hexenal, in tomato plant emission by gas chromatography-mass spectrometry (GC-MS) and solid-phase microextraction (SPME) with on-fiber derivatization. In this method, O-2,3,4,5,6-(pentafluorobenzyl)hydroxylamine (PFBHA) in aqueous solution was first headspace adsorbed onto a 65 microm poly(dimethylsiloxane)/divinylbenzene (PDMS/DVB) fiber at 25 degrees C for 5 min, and then the fiber with adsorbed PFBHA was used for headspace extraction of tomato plant emission at 25 degrees C for 6 min. Finally, the resulting oximes adsorbed on the fiber were desorbed and analyzed by GC-MS. Extraction conditions and method validation were studied. The proposed method had low detection limit values for the three aldehydes from 0.1 to 0.5 ng/L and good precision (RSD less than 10%). In this work, the method was applied to investigation of tomato plant defense response to Helicoverpa armigera.     

气相色谱法分离和测定3种植物内源激素

 应用大口径毛细管气相色谱法,以正二十二烷为内标物,对植物组织中的吲哚乙酸(IAA)、脱落酸(ABA)和赤霉素(GA)等3种内源激素进行了测定。结果表明:IAA,ABA和GA的最低检测限依次为0.16,0.08和0.48mgL,相对标准偏差均小于3.0%,平均回收率为88.4%～92.2%。方法简便、灵敏、准确、重现性好。     

Analysis of polar pesticides in water and wine samples by automated in-tube solid-phase microextraction coupled with high-performance liquid chromatography-mass spectrometry

A simple and sensitive method for the determination of polar pesticides in water and wine samples was developed by coupling automated in-tube solid-phase microextraction (SPME) to high-performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-ESI-MS). To achieve optimum performance, the conditions for both the in-tube SPME and the ESI-MS detection were investigated. In-tube SPME conditions were optimized by selecting the appropriate extraction parameters, especially the stationary phases used for SPME. For the compounds studied, a custom-made polypyrrole (PPY)-coated capillary showed superior extraction efficiency as compared to several commercial capillaries tested, and therefore, it was selected for in-tube SPME. The influence of the ethanol content on the performance of in-tube SPME was also investigated. It was found that the amount of pesticides extracted decreased with the increase of ethanol content in the solutions. The ESI-MS detection conditions were optimized as follows: nebulizer gas, N2 (30 p.s.i.; 1 p.s.i.=6894.76 Pa); drying gas, N2 (10 l/min, 350 degrees C); capillary voltage, 4500 V; ionization mode, positive; mass scan range, 50-350 amu; fragmentor voltage, variable depending on the ions selected. Due to the high extraction efficiency of the PPY coating and the high sensitive mass detection, the detection limits (S/N = 3) of this method for the compounds studied are in the range of 0.01 to 1.2 ng/ml, which are more than one order of magnitude lower than those of the previous in-tube SPME-HPLC-UV method. A linear relationship was obtained for each analyte in the concentration range of 0.5 to 200 ng/ml with MS detection. This method was applied to the analysis of phenylurea and carbamate pesticides in spiked water and wine samples.     

Determination of acrylamide formed in asparagine/D-glucose maillard model systems by using gas chromatography with headspace solid-phase microextraction

A gas chromatographic method, along with a headspace solid-phase microextraction (HS-SPME), was developed for the determination of acrylamide formed in Maillard reaction model systems. The developed method was validated by liquid chromatography/mass spectrometry. A headspace sample was collected from an aqueous acrylamide solution (100 microg/mL) by SPME and directly injected into a gas chromatograph equipped with a nitrogen-phosphorus detector. The recovery of acrylamide from an aqueous solution was satisfactory, i.e, >93% under the conditions used. Acrylamide formed in an asparagine/D-glucose (molar ratio, 1/2) Maillard reaction model system heated at 150 and 170 degrees C for 20 min was collected and analyzed by the newly developed method using gas chromatography with nitrogen-phosphorus detection and HS-SPME. The amounts of acrylamide were 318 +/- 33 microg/g asparagine from a sample heated at 150 degrees C and 3329 +/- 176 microg/g asparagine from a sample heated at 170 degrees C. Addition of cysteamine or glutathione to the above model system reduced acrylamide formation. Acrylamide formation was not observed when cysteamine or glutathione was added to asparagine in the above model systems to obtain equimolar concentrations of both compounds. This newly developed method is simple and sensitive, and requires no solvent extraction.     

Determination of the acaricide fenbutatin oxide in water samples by automated headspace-SPME-GC/MS

The analysis of the acaricide fenbutatin oxide (FBTO) having a molecular weight of 1052.66 g mol(-1) in water samples by capillary GC/MS after in-situ derivatization with sodium tetraethylborate (NaBEt4) and headspace-SPME enrichment is described. Automated SPME is performed at 80 degrees C for 30 min. Detection is carried out in the ion monitoring mode with deuterated triphenyltin (TPhTd15) as internal standard. Good linearity (R2 = 0.9993) was obtained in the dynamic range 20 to 1000 ng L(-1) with a limit of detection of 16 ng L(1) (LOD at 3 S/N) and a limit of quantitation of 50 ng L(-1) (LOQ at 10 S/N). Intra-day RSD% for n=6 was 8.9 at the LOQ level.     

Enantioselective determination of the organochlorine pesticide bromocyclen in spiked fish tissue using solid-phase microextraction coupled to gas chromatography with ECD and ICP-MS detection

A method for enantioselective determination of bromocyclen enantiomers in fish tissue has been developed. The enantiomers were resolved by capillary gas chromatography (GC) using a commercial chiral column (CP-Chirasil-Dex CB) and a temperature program from 50 degrees C (held for 1 min), raised to 140 degrees C at 40 degrees C min(-1) and then raised at 0.2 degrees C min(-1) to 155 degrees C. This enantioselective gas chromatographic separation was combined with a clean-up/enrichment procedure based on solid-phase microextraction (SPME). Under SPME optimized conditions, precision, linearity range and detection limits of the developed SPME-enantioselective GC procedure were evaluated and compared using two different detection systems: a classical electron-capture detection (ECD) and an element specific detection using inductively coupled plasma mass spectrometry (ICP-MS). The SPME-GC-ECD method exhibited an excellent sensitivity, with detection limits of 0.2 ng L(-1) for each enantiomer of bromocyclen. Although ICP-MS offered poorer detection limits (7 ng L(-1) as Br, equivalent to 36 ng L(-1) of each enantiomer) than conventional ECD detector, it proved to be clearly superior in terms of selectivity. The relative potential and performance of the two compared methods for real-life analysis has been illustrated by the determination of enantiomers of bromocyclen in spiked tissue extracts of trout.     

Direct determination of anabolic steroids in pig urine by a new SPME-GC-MS method

A new solid phase microextraction (SPME) method coupled with gas chromatography-mass spectrometry (GC-MS) was developed for rapid determination of four anabolic steroids such as 3α-hydroxy-5α-androstane-17-one (HA), dihydrotestosterone (DHT), androstenedione (AD) and methyltestosterone (MT) in pig urine. SPME was used to extract the four anabolic compounds directly without derivatization. The optimum SPME sampling conditions were based on the home-made carbowax-divinylbenzene (CW-DVB) fiber coating during extraction at 40 °C for 50 min with 0.18 g/mL NaCl solution and 750 rpm stirring speed. The linear ranges of the proposed method were in the range of 8-640 pg/mL for HA and DHT and 16-510 pg/mL for AD and MT, respectively. The detection limits (S/N = 3) were from 2 to 8 pg/mL for the four anabolic steroids. This SPME method provided very high enrichment factors for the four anabolic steroids, which were 1063-fold and 965-fold for HA and DHT at the concentration of 8 pg/mL and 207-fold and 451-fold for AD and MT at the concentration of 16 pg/mL, respectively. The recoveries ranged from 71.3 to 121%, and the RSDs were lower than 12.9%. The method was sensitive and reliable for determination of trace anabolic steroids in biological samples.     

Determination of aliphatic amines using N-succinimidyl benzoate as a new derivatization reagent in gas chromatography combined with solid-phase microextraction

A simple, selective and sensitive approach was developed for the quantitation of aliphatic amines in lake water applying a new reagent (N-succinimidyl benzoate, SIBA), synthesized in the laboratory of the authors. Derivatization of the n-C1-C6 aliphatic monoamines and dimethylamine in aqueous solution with SIBA was followed by headspace solid-phase microextraction (SPME). Derivatives were identified by gas chromatography-mass spectrometry and determined by gas chromatography-flame ionization detection. Both derivatization and SPME conditions have been optimized. Derivatizations were performed in borate buffer (pH 8.8), at 60 degrees C for 22 min. SPME was carried out from saturated sodium chloride solution, at 80 degrees C for 60 min, desorption at 250 degrees C for 2 min. Detection limit of derivatized amines proved to be 0.13-7.2 nmol/l, while recovery of amines from lake water samples, in the concentration range of 100-200 microg/l, varied from 94.1 to 102.7%.     

Analysis of dideoxyadenosine triphosphate by CE with fluorescence detection. I. Derivatization through the phosphate group

A CZE method was developed, which separates 2',3'-dideoxyadenosine-5'-triphosphate (ddATP) from other metabolites and endogenous nucleotides at high concentrations (20-200 microg/mL) to allow UV detection. To enhance sensitivity, fluorescence detection which requires prior derivatization of compounds was examined. Precapillary derivatization of ddATP in the presence of N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDAC) with dansyl ethylenediamine (dansyl EDA) was faster and stable compared to that of 4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene-3-propionyl ethylenediamine (BODIPY FL EDA). Reaction conditions, reagent concentrations and detection parameters were optimized and highest derivatization efficiency was achieved in 0.1 M 1-methylimidazole buffer (pH 8.0) with 140 mM EDAC in 1-methylimidazole buffer and 30 mM dansyl EDA in DMF for 90 min at 60 degrees C. Dansyl EDA derivatives of ddATP, 2'-deoxyadenosine-5'-triphosphate (dATP) and ATP were comigrating with the CZE method; therefore, a MEKC method was developed and optimized for repeatable separations. Upon dansylation, sensitivity of ddATP with fluorescence detection (LOQ = 12 ng/mL) was 160 times higher than UV detection (LOQ = 1.9 microg/mL).     

Determination of chlorophenols by solid-phase microextraction and liquid chromatography with electrochemical detection

A solid-phase microextraction method has been developed for the determination of 19 chlorophenols (CPs) in environmental samples. The analytical procedure involves direct sampling of CPs from water using solid-phase microextraction (SPME) and determination by liquid chromatography with electrochemical detection (LC-ED). Three kinds of fibre [50 microm carbowax-templated resin (CW-TPR), 60 microm polydimethylsiloxane-divinylbenzene (PDMS-DVB) and 85 microm polyacrylate (PA)] were evaluated for the analysis of CPs. Of these fibres, CW-TPR is the most suitable for the determination of CPs in water. Optimal conditions for both desorption and absorption SPME processes, such as composition of the desorption solvent (water-acetonitrile-methanol, 20:30:50) and desorption time (5 min), extraction time (50 min) and temperature (40 degrees C) as well as pH (3.5) and ionic strength (6 g NaCl) were established. The precision of the SPME-LC-ED method gave relative standard deviations (RSDs) of between 4 and 11%. The method was linear over three to four orders of magnitude and the detection limits, from 3 to 8 ng l(-1), were lower than the European Community legislation limits for drinking water. The method was applied to the analysis of CPs in drinking water and wood samples.     

Determination of dichlorvos by on-line microwave-assisted extraction coupled to headspace solid-phase microextraction and gas chromatography-electron-capture detection

The pretreatment technique of microwave-assisted extraction on-line headspace solid-phase microextraction (MAE-HS-SPME) was designed and studied for one-step in-situ sample preparation prior to the chromatographic analysis of a pesticide on vegetables. The pesticide on chopped vegetables was extracted into an aqueous solution with the aid of microwave irradiation and then directly onto the SPME fiber in headspace. After being collected on to the SPME fiber and desorbed in the GC injection port, the pesticide (dichlorvos) was analyzed with a GC-electron-capture detection system. The optimum conditions for obtaining extraction efficiency, such as the pH, the polarity modifier, and the salt added in sample solution, the microwave irradiation, as well as the desorption parameters were investigated. Experimental results indicated that the proposed MAE-HS-SPME technique attained the best extraction efficiency of 106% recovery under the optimized conditions, i.e. irradiation of extraction solution (10% aqueous ethylene glycol) at pH 5.0 with medium microwave power for 10 min. Desorption at 220 degrees C for 3 min offered the best detection result. The detection was linear at 5-75 microg/l with correlation coefficient of 0.9985. Detection limit was obtained at approximately 1.0 microg/l level based on S/N=3. The proposed method provided a very simple, fast, and solvent-less procedure to collect pesticides directly from vegetables for GC determination. Its application was illustrated by the analysis of trace dichlorvos in vegetables.     

Application of graphene nanoplatelets silica composite,prepared by sol–gel technology,as a novel sorbent in two microextraction techniques

In this study, the application of a novel nanomaterial composite was investigated in two microextraction techniques of solid‐phase microextraction and a needle trap device in a variety of sampling conditions. The optimum sampling temperature and relative humidity were 10°C and 20%, respectively, for both techniques with two sorbents of graphene/silica composite and polydimethyl siloxane. The two microextraction techniques with the proposed sorbent showed recoveries of 95.2 and 94.6% after 7 days. For the needle trap device the optimums desorption time and temperature were 3 min at 290°C and for SPME these measures were 1 and 1.5 min at 240–250°C for the graphene/silica composite and polydimethyl siloxane, respectively. The relative standard division obtained in inter‐ and intra‐day comparative studies were 3.3–14.3 and 5.1–25.4, respectively. For four sample the limit of detection was 0.021–0.25 ng/mL, and the limit of quantitation was 0.08–0.75 ng/mL. The results show that the graphene/silica composite is an appropriate extraction media for both techniques. Combining an appropriate sorbent with microextraction techniques, and using these in conjunction with a sensitive analytical instrument can introduce a strong method for sampling and analysis of occupational and environmental pollutants in air.     

Solid-phase microextraction coupled with gas chromatography-ion trap mass spectrometry for the analysis of haloacetic acids in water

Headspace solid-phase microextraction (SPME) was studied as a possible alternative to liquid-liquid extraction for the analysis of haloacetic acids (HAAs) in water. The method involves derivatization of the acids to their ethyl esters using sulphuric acid and ethanol after evaporation, followed by headspace SPME with a polydimethylsiloxane fibre and gas chromatography-ion trap mass spectrometry (GC-IT-MS). The derivatization procedure was optimized: maximum sensitivity was obtained with esterification for 10 min at 50 degrees C in 30 microl of sulphuric acid and 40 microl of ethanol. The headspace SPME conditions were also optimized and good sensitivity was obtained at a sampling temperature of 25 degrees C, an absorption time of 10 min, the addition of 0.1 g of anhydrous sodium sulfate and a desorption time of 2 min. Good precision (RSD lower than 10%) and detection limits in the ng l(-1) range (from 10 to 200 ng l(-1)) were obtained for all the compounds. The optimized procedure was applied to the analysis of HAAs in tap water and the results obtained by standard addition agreed with those of EPA method 552.2, whereas discrepancies due to matrix interferences were observed using external calibration. Consequently, headspace SPME-GC-IT-MS with standard addition is recommended for the analysis of these compounds in drinking water.     

Solid-phase microextraction gas chromatography-mass spectrometry determination of monoterpenes in honey

Solid-phase microextraction (SPME) using a 100 microm poly(dimethylsiloxane) (PDMS) fiber, followed by gas chromatography (GC-MS) determination, has been applied to the analysis of some monoterpenoids in honey. The extraction was performed by direct immersion of the fiber using a sampling period of 15 min with constant magnetic stirring (1100 rpm) and an extraction temperature of 20 degrees C. A 7 mL sample volume of an aqueous solution of honey with 25% of NaCl was placed in 15 mL glass vial fitted with screw cap and PTFE/silicone septum. Desorption was performed directly in the gas chromatograph injector port during 5 min at 250 degrees C using the splitless mode. The method is sensitive with detection limits between 11 and 25 microg L(-1), precise with coefficients of variation in the range 1.28 and 3.71%, and linear over more than one order of magnitude. The related conditions were used for honey sample analyses with recoveries between 71.8 and 90.9%. SPME remains an attractive alternative technique due to its rapidity and because it is a solvent free extraction method.     

Determination of 1-(2-methoxyphenyl)piperazine derivatives of isocyanates at low concentrations by temperature-programmed miniaturized liquid chromatography

A temperature-programmed packed capillary LC method with large-volume injection on-column focusing has been developed for screening and determination of 1-(2-methoxyphenyl)piperazine derivatives of airborne toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, hexamethylenediisocyanate and methylenebisphenyl-4,4-diisocyanate, based on sampling methods described in MDHS 25/3. Injection volumes up to 100 microl were successfully loaded onto the 250x0.32 mm I.D. capillary column packed with 3 microm Hypersil ODS particles. The isocyanate derivatives were loaded at 10 degrees C and eluted by a three-step temperature program starting at 10 degrees C for 10 min, followed by a temperature ramp of 2.5 degrees C min(-1) to 45 degrees C and then 9.9 degrees C min(-1) to 90 degrees C. The mobile phase consisted of acetonitrile-acetate buffer (3% triethylamine, pH 4.5) (45:55, v/v). The isocyanate derivatives were dissolved in acetonitrile-acetate buffer (3% triethylamine, pH 4.5) (30:70, v/v) to achieve sufficient focusing. The concentration limit of detection of the individual derivatives utilizing an "U" shaped flow cell with a 8.0 mm light path and an injection volume of 100 microl was 44, 87, 43 and 210 pg ml(-1) for toluene-2,6-diisocyanate, hexamethylenediisocyanate, toluene-2,4-diisocyanate and methylenebisphenyl-4,4-diisocyanate, respectively. Within the investigated concentration range, 10-500 ng ml(-1), the linear calibration curves gave correlation coefficients ranging from 0.994 to 0.998. The repeatability of the method with regard to retention time and peak height ranged from 0.3 to 1.1% and 1.1 to 2.3% (n=9) relative standard deviation, respectively. The average recovery of the method, with regard to toluene-2,4-diisocyanate, was 97.7+/-1.6% (n=9).     

Automated,continuous, and dynamic speciation of urinary arsenic in the bladder of living organisms using microdialysis sampling coupled on-line with high performance liquid chromatography and hydride generation atomic absorption spectrometry

An on-line and fully automated method was developed for the continuous and dynamic in vivo monitoring of four arsenic species [arsenite (AsIII), arsenate (AsV), monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA)] in urine of living organisms. In this method a microdialysis sampling technique was employed to couple on-line with high performance liquid chromatography (HPLC) and hydride generation atomic absorption spectrometry (HGAAS). Dialysates perfused through implanted microdialysis probes were collected with a sample loop of an on-line injector for direct and automated injection into HPLC system hyphenated with HGAAS. The saline (0.9% NaCl) solution was perfused at the rate of 1 microl min(-1) through the microdialysis probe and the dialysate was loaded into 50 microl of sample loop. The separation conditions were optimally selected to be in phosphate buffer solution at a pH 5.2 with a flow rate of 1.2 ml min(-1). The effluent from the HPLC was first mixed on-line at the exit of the column with HCl (1 M) solution and then mixed with a NaBH4 (0.2% m/v) solution. Based on the optimal conditions obtained, linear ranges of 2.5-50 ng ml(-1) for AsIII and 6.75-100 ng ml(-1) for the other three arsenic species were obtained. Detection limits of 1.00, 2.18, 1.03 and 2.17 ng ml(-1) were obtained for AsIII, DMA, MMA and AsV, respectively. Typical precision values of 3.4% (AsIII), 5.4% (DMA), 3.6% (MMA) and 7.5% (AsV) were obtained, respectively, at a 25 ng ml(-1) level. Recoveries close to 100%, relative to an aqueous standard, were observed for each species. The average in vivo recoveries of AsIII, DMA, MMA and AsV in rat bladder urine were 56+/-5%, 60+/-9%, 49+/-3% and 55+/-7%, respectively. The use of an on-line microdialysis-HPLC-HGAAS system permitted the determination of four urinary arsenic species in the bladder of an anesthetized rat with a temporal resolution of 50 min sampling.     

Development of an SPME-GC-MS/MS procedure for the monitoring of 2-phenoxyethanol in anaesthetised fish

2-Phenoxyethanol (ethylene glycol monophenyl ether, C(8)H(10)O(2)) is a promising anaesthetic agent used in fisheries and aquaculture. The aim of this study was to develop a fast and easy method to determine 2-phenoxyethanol residue levels in fish tissue and blood plasma, and, subsequently, to use the method to monitor the dynamics of 2-phenoxyethanol residues in fish treated with anaesthetic. We developed a new procedure that employs solid phase microextraction (SPME) of the target analyte from the sample headspace followed by gas chromatography-mass spectrometry (GC-MS). Both sample handling, aimed at maximum transfer of 2-phenoxyethanol into the headspace, and SPME-GC-MS conditions were carefully optimised. Using a divinylbenzene/Carboxen/polydimethylsiloxane (PDMS/CAR/DVB) fiber for 60 min sampling at 30 degrees C and an ion trap detector operated in MS/MS mode, we obtained detection (LOD) and quantification (LOQ) limits of 0.03 and 0.1 mg kg(-1) of sample, respectively. The method was linear in a range of 0.1-250 mg kg(-1) and, depending on the sample matrix and spiking level, a repeatability (expressed as relative standard deviation, R.S.D.) of between 3% and 11% was obtained.     

Determination of vitamin E acid succinate in biodegradable microspheres by reversed-phase high-performance liquid chromatography

A simple, rapid, and reproducible reversed-phase high-performance liquid chromatographic (HPLC) method is applied to the routine assay of vitamin E acid succinate in biodegradable microspheres. Vitamin E acid-succinate-containing poly-(D,L-lactic-co-glycolic acid) microspheres are prepared by the solvent evaporation method. The starting drug-polymer ratio is 1:10 (w/w) and the total amount of drug and polymer processed is always 440 mg. The content of vitamin E acid succinate in the microspheres is evaluated by HPLC. Chromatography is carried out isocratically at 25 degrees C +/- 0.5 degrees C on an Extrasil ODS-2 column with a mobile phase composed of methanol-water (97:3, v/v) (pH 5.6) at a flow rate of 2 mL/min and UV detection at 284 nm. Parameters such as linearity, limits of quantitation (LOQ) and detection (LOD), precision, accuracy, recovery, specificity, and ruggedness are studied as reported in the International Conference on Harmonization guidelines. The stability of vitamin E acid succinate is also studied with satisfactory results after 48 h at 25 degrees C. The method is selective and linear for drug concentrations in the range 15-210 micro g/mL. The LOQ and LOD are 15 and 3 micro g/mL, respectively. The results for accuracy studies are good. Values for coefficient of variation for intra- and interassay are 2.08% and 2.32%, respectively. The mean percentage of vitamin E acid succinate in the recovery studies is 99.52% +/- 0.81%. The mean loading efficiency for microspheres is 96.53% +/- 1.31%.