Interlaboratory verified liquid chromatographic method for analysis of vitamins A and E in soy-based infant formula powder

An interlaboratory verified, liquid chromatographic (LC) method is presented for the analysis of all-rac-alpha-tocopheryl acetate and retinyl palmitate in soy-based infant formula. The extraction procedure uses sample dehydration with magnesium sulfate followed by extraction with isopropanol, hexane-ethyl acetate (85 + 15, v/v). After evaporation and filtration, the sample extract is injected directly onto a normal-phase LC system with fluorescence detection. All-rac-alpha-tocopheryl acetate and retinyl palmitate are quantitated isocratically with a mobile phase of hexane containing 0.50% (v/v) and 0.125% (v/v) isopropanol, respectively. A zero control reference material (ZRM) was spiked at 5 levels, with 5 replicate analyses of 1/2x, x, 2x, 4x, and 16x where "x" is the minimum level of 250 IU/100 kcal (vitamin A) and 0.7 IU/100 kcal (vitamin E) as specified in 21 Code of Federal Regulations 107.100. The following recoveries and RSD values represent an average (n = 25) of the 5 levels for each analyte: all-rac-alpha-tocopheryl acetate, 100% (RSD = 3.5%); retinyl palmitate, 97.2% (RSD = 2.1%). Two additional laboratories analyzed the fortified ZRM samples. Average recoveries (n = 24) of all-rac-alpha-tocopheryl acetate and retinyl palmitate at 4 levels were all-rac-alpha-tocopheryl acetate, 99.0% (RSD = 4.0%), and retinyl palmitate, 96.2% (RSD = 1.4%) at the second laboratory. Average recoveries (n = 24) of all-rac-alpha-tocopheryl acetate and retinyl palmitate at 4 levels were all-rac-alpha-tocopheryl acetate, 102% (RSD = 1.4%) and retinyl palmitate, 95.7% (RSD = 2.0%) at the third laboratory. In addition, 6 replicates of the same commercial soy-based infant formula powder were run by the 3 laboratories.     

Determination of total fat in milk- and soy-based infant formula powder by supercritical fluid extraction

Commercially available simple benchtop systems using CO2 supercritical fluid extraction (SFE) eliminate expensive organic solvent disposal problems and offer potential to meet a demand for rapid, accurate high-volume gravimetric determinations of total fat content of infant formula powders. A Data Quality Objectives (DQOs) approach was used to evaluate the performance characteristics of instrumental SFE extraction for determination of total gravimetric fat in infant formula. The established DQOs included the following: ACCURACY: Correct values were obtained for a suitable reference material, SRM 1846 Infant Formula [National Institute of Standards and Technology (NIST), Gaithersburg, MD]. RUGGEDNESS: Variables were defined as (1) extraction time (35 min optimum); (2) ratio of sample size to diatomaceous earth support material (1 g sample/2 g support); (3) ratio of distilled water to alcohol (50% isopropanol optimum for both milk- and soy-based infant formula samples); (4) extraction flow rate was 3-3.5 mL/min optimum. PRECISION: Relative standard deviations of multiple determinations fell within the Horwitz limits of acceptability of < or = 2.8% at the level of analyte determined (0.34-2.5% obtained). SCOPE OF APPLICABILITY: Includes milk- and soy-based infant formula powders. Research data were obtained by use of a commercially available fat analyzer. Samples of the SRM, 2 commercial milk-based and 3 commercial soy-based infant formula products were distributed to 2 additional collaborating laboratories. Very good agreement was obtained among the submitting and collaborating laboratories for these samples. The use of clearly defined DQOs to establish method performance characteristics, along with the commercially available reference material, provided the mechanism for verification and validation of analytical methodology.     

Determination of niacin in infant formula by solid-phase extraction and anion-exchange liquid chromatography.

A peer-verified, solid-phase extraction (SPE)/anion exchange liquid chromatographic method is presented for the determination of niacin in milk-based and soy-based infant formula. Analysis is in 3 steps: test sample digestion, extraction/cleanup, and liquid chromatography (LC). Digestion uses a standard AOAC digestion procedure that involves autoclaving at 121 degrees C for 45 min in (1 + 1) H2SO4 to free endogenous niacin from protein and to convert added niacinamide to niacin. The digest solution is adjusted to pH 6.5 with 7.5M NaOH. Acidification to pH <1.0 with (1 + 1) H2SO4 precipitates the protein. The clarified solution is then filtered, and the filtrate is brought to volume. SPE of niacin is accomplished by passing an aliquot of the digest solution through an aromatic sulfonic acid-SPE (ArSCX-SPE) column. After the column is washed with methanol and water to remove extraneous material, the niacin is eluted with 0.25M sodium acetate/acetic acid buffer at pH 5.6. An anion-exchange polystyrene-divinylbenzene column with 0.1 M sodium acetate/acetic acid buffer at pH 4.0 is used for LC. Niacin is determined by UV detection at 260 nm. A standard curve is prepared by passing known amounts of niacin through the ArSCX-SPE columns used for niacin extraction. The following values for x and relative standard deviation (RSD) were obtained for National Institute of Standards and Technology Standard Reference Material (NIST SRM) 1846 Infant Formula with a certified value for niacin of 63.3 +/- 7.6 microg/g: Submitting laboratory.-- x = 59.7 +/- 4.0 microg/g; RSD = >6.7%; confidence interval (CI) = +/- 1.4 microg/g; n = 27. Peer laboratory.--x = 56.6 +/- 6.6 microg/g; RSD = >11.7%; CI =+/- 4.1 microg/g; n = 8.     

Molecularly imprinted matrix solid-phase dispersion for extraction of chloramphenicol in fish tissues coupled with high-performance liquid chromatography determination

The synthesis and evaluation of a molecularly imprinted polymer (MIP) as a selective matrix solid-phase dispersion (MSPD) sorbent, coupled with high-performance liquid chromatography for the efficient determination of chloramphenicol (CAP) in fish tissues are studied. The polymer was prepared using CAP as the template molecule, vinylpyridine as the functional monomer and ethylene glycol dimethacrylate as the cross-linking monomer, and sodium dodecyl sulfate as the surfactant in the presence of water as a solvent by miniemulsion polymerization. The CAP-imprinted polymers and nonimprinted polymers (NIPs) were characterized by Fourier transform IR spectroscopy, scanning electron microscopy, and static adsorption experiments. The CAP-imprinted material prepared showed high adsorption capacity, significant selectivity, and good site accessibility. The maximum static adsorption capacity of the CAP-imprinted and the NIP material for CAP was 78.4 and 59.9 mg g(-1), respectively. The relative selectivity factors of this CAP-imprinted material were larger than 1.9. Several parameters influencing the MSPD process were optimized. Finally, the CAP-imprinted polymers were used as the sorbent in MSPD to determine CAP in three kinds of fishes and resulted in satisfactory recovery in the range 89.8-101.43%. CAP-imprinted polymer as a sorbent in MSPD is better than C18 and attapulgite in terms of both recovery and percent relative standard deviation. The baseline noise was measured from a chromatogram of a blank fish sample which was treated after the MSPD procedure using CAP-imprinted polymer as a sorbent. Signal values of 3 times the noise (signal-to-noise ratio of 3) and 10 times the noise (signal-to-noise ratio of 10) were used to calculate the limit of detection and the limit of quantitation of the calibration curve. The limit of detection for CAP was 1.2 ng g(-1) and the limit of quantitation was 3.9 ng g(-1).     

An improved method for acetaldehyde determination in blood by high-performance liquid chromatography and solid-phase extraction

This study reports on an improved method for acetaldehyde (ACH) determination in blood by high-performance liquid chromatography (HPLC). In the case of HPLC analysis, ACH is generally converted to derivatives for ultraviolet detection (for example 2,4-dinitrophenylhydrazine [DNPH] derivative). Nevertheless, elevation of the background during protein precipitation, hydrazone synthesis, or both frequently results in a serious loss of accuracy and precision of the analysis. The method in this study is developed to minimize the increase in nonspecific ACH-DNPH with a view to optimize mainly the synthetic condition of ACH-DNPH. The background is decreased dramatically by gentle deproteination, optimization of the DNPH amount and reaction pH, and reversed-phase solid extraction for the elimination of excess DNPH reagent. The standard curves show good linearity between 0 and 100 microM and minimal background is observed, indicating that the method is useful for monitoring the ACH concentration in blood.     

Determination of niacin in infant formula by solid-phase extraction/liquid chromatography: peer-verified method performance-interlaboratory validation

This paper reports the results of the interlaboratory peer validation study of AOAC Peer-Verified Method (PVM) 1:2,000 for the determination of niacin in infant formula by solid-phase extraction/liquid chromatography. We have used a Data Quality Objectives (DQO) approach to address not only method variability and robustness but also accuracy of data through the use of an appropriate reference material in conjunction with the interlaboratory validation study. Our DQO included the following: (1) statistical agreement of analytical results and quantitative recovery between 2 collaborating laboratories; (2) the repeatability relative standard deviation (RSDr) values and the HORRAT (Horwitz ratio) obtained (1.07), which satisfied the criteria of the Horwitz "limits of acceptability" at the analyte level present; (3) validation of lack of interference; and (4) accuracy agreement within assigned values for a certified reference material. National Institute of Standards and Technology Standard Reference Material (NIST SRM) 1846 Infant Formula, with a certified value of 63.3 +/- 7.6 microg/g for niacin content, was used as a test material for collaborative study and accuracy assessment. Niacin values obtained by the originating laboratory were 59.7 +/- 4.0 microg/g (95% confidence interval [CI] = 1.4 microg/g with a relative standard deviation [RSD] of 6.7%) and by the peer laboratory were 56.6 +/- 6.6 microg/g (95% CI = 4.1 microg/g, with an RSD of 11.7%). Statistical evaluation using the means equivalence test showed that nicotinic acid values obtained by the peer laboratory were equivalent to those values obtained by the originating laboratory. Linear calibration curves and quantitative recovery were obtained. Integration of the PVM process with a readily available certified reference material gives the user confidence in the accuracy of the data generated by the method through traceability to the reference material used.     

在线二维液相色谱法同时测定婴幼儿和成人配方营养品中的维生素A、D3和E

建立了在线二维液相色谱同时快速测定婴幼儿配方乳品和成人强化乳品中维生素A、D₃和E含量的方法。首先,依据疏水减法模型,选择C8柱和极性嵌合的反相C18柱分别作为一维和二维分离柱,构成正交分离体系,并均以甲醇、乙腈和水作为流动相,检测波长设为263 nm(维生素D₃)、296 nm(维生素E)和325 nm(维生素A)。采用双三元液相色谱的左泵作为一维分析泵,完成维生素A、E的定量和维生素D₃的净化;根据维生素D₃在一维色谱柱上的保留时间,确定切割时间窗口,并以500 μL定量环收集含有维生素D₃的馏分,由双三元液相色谱的右泵将馏分带到二维色谱柱中,以维生素D₂作为内标物,采用内标法完成维生素D₃的定量分析,整个过程在密闭系统中自动化完成。在上述优化条件下测定了婴幼儿和成人奶粉、奶酪及酸奶等强化乳品中3种维生素的含量。经过1.25 kg/L KOH溶液的热皂化和石油醚的萃取,样品萃取液直接进样分析,得到维生素D₃的加标回收率为75.50%~85.00%,并通过配对t检验法与标准方法测定结果进行比较分析,结果差异无统计学意义,表明本方法可同时快速、准确测定婴幼儿及其他配方营养品中维生素A、D₃、E的含量,提高了样品分析效率。     

Determination of niacin in infant formula and wheat flour by anion-exchange liquid chromatography with solid-phase extraction cleanup

Niacin content must be included on food labels of infant formula products and bakery products containing enriched flour. Liquid chromatographic (LC) determination of niacin in complex food matrixes is complicated by the presence of endogenous compounds that absorb at the commonly used wave-length of 260 nm. Also, the presence of particulate matter in the standard sulfuric acid extraction procedure results in reduced life of LC columns and precolumns. A simple, rapid, solid-phase extraction (SPE) procedure for separation and cleanup of niacin from a complex food matrix digest has been developed. By using a vacuum manifold with the SPE column system, multiple samples can be processed quickly and efficiently for LC analysis, compared with gravimetric column cleanup. Sulfuric acid sample digest is passed over an aromatic sulfonic acid cation-exchange (ArSCX-SPE) or a sulfonated Florisil SPE column. Niacin is eluted with 0.25M sodium acetate-acetic acid, pH 5.6 buffer in vacuo. LC chromatograms of the resulting eluate are free of interference from other components absorbing at 260 nm at the retention time of niacin. Validation of the method was obtained from agreement of analytical results on available reference materials. For both SPE methods, values for niacin in SRM 1846 Infant Formula (milk-based powder) were within uncertainty ranges of the certified value. Use of several calibration procedures (the LC computer program, a peak area response graphic standard curve, or the method of standard additions) with both SPE procedures resulted in niacin values for 3 RM-Wheat Flours (not certified for niacin) in agreement (90-105%) with their respective values reported in the literature. Several commercial wheat flours showed a broad 260 nm interference, resulting in high niacin values. Niacin recoveries from spiked soy-based liquid infant formulas ranged from 95-107% with the ArSCX-SPE column. Calibration curves of niacin were linear up to 400 micrograms/mL, with a detection limit of 0.2 microgram/mL.     

The rapid determination of artemisinin by post-column derivatization high-performance liquid chromatography using matrix solid-phase dispersion method

Artemisinin (an antimalaric compound) is isolated as the active compound of the medicinal plant Artemisia annua L. A simple, rapid, and high-efficient method of extraction is developed, in which it is extracted by matrix solid-phase dispersion (MSPD) and directly analyzed by post-column derivatization high-performance liquid chromatography (HPLC). The quantitation results from the MSPD method are compared with two conventional liquid solvent extraction processes, Soxhlet and ultrasonic wave by F-test, and the result indicates no significant difference. The production rate of Artemisinin during wild plant growth (tested over two years, acquired from Yunnan, provincial Yuan Yan country) is determined. The recovery range of determination is 88.1-91.2%. The relative standard deviation (RSD) is 4.55-6.43%. The limits of detection are 0.1 microg/mL, and the limits of quantitation are 0.5 microg/mL.     

Simultaneous determination of five fat-soluble vitamins in feed by high-performance liquid chromatography following solid-phase extraction

A high-performance liquid chromatography method is developed for the simultaneous determination of menadione, retinyl acetate, cholecalciferol, alpha-tocopherol, and alpha-tocopherol acetate in feed. The present study uses an enzyme to destroy the coating film, ethanol to extract free vitamins, and Oasis HLB cartridges to purify. Vitamins are separated using an Atlantis dC18 column. The mobile phase is methanol-water (98:2 v/v). Detection is performed with a UV-vis detector at 230 and 265 nm. The linearity, accuracy, and repeatability of this method are all satisfactory. Application of the method is suitable for the determination of the fat-soluble vitamins in general feed.     

Determination of sulfonamides in livers using matrix solid-phase dispersion extraction high-performance liquid chromatography

The matrix solid-phase dispersion (MSPD) was applied for extracting seven sulfonamides (SAs) in liver samples. The separation and determination were carried out by high-performance liquid chromatography. The analytes were derivated with fluorescamine and detected with fluorescence detector. The types of dispersion adsorbents for MSPD were examined and the highest recovery was obtained when the diatomaceous earth was used as the dispersion adsorbent and the mass ratio of dispersion adsorbent to sample was 3:1. The acetone was used as the elution solvent. Under the optimal conditions, the linear range for determining the SAs in liver samples was 5.0-1000.0 ng/g. The porcine, chicken and cattle liver samples were analyzed and the average recoveries of seven SAs were higher than 84.6%.     

Application of matrix solid-phase dispersion and high-performance liquid chromatography for determination of sulfonamides in honey

A novel method for simultaneous determination of 8 sulfonamide residues (sulfathiazole, sulfapyridine, sulfadiazine, sulfamerazine, sulfamonome-thoxine, sulfachloropyridazine, sulfamethoxazole, and sulfadimethoxine) in honey samples by high-performance liquid chromatography (HPLC) has been developed on the basis of precolumn derivatization with 9-fluorenylmethyl-chloroformate (FMOC-Cl). Sulfonamide residues in honey samples were extracted and purified by matrix solid-phase dispersion with C18 as the solid support. The residues were derivatized by FMOC-CI, and the FMOC-sulfonamide derivatives were further purified by solid-phase extraction with silica gel as the solid support prior to HPLC analysis. The average recoveries for most sulfonamide compounds at different spiking levels (from 10 to 250 microg/kg) were > 70% with relative standard deviations < 16%, and their limits of detection were 4.0 microg/kg. The established analytical method has high sensitivity and repeatability and can be applicable for determining the sulfonamide residues in various honey matrixes.     

Rapid method for the determination of vitamins A and E in foods using ultra-high-performance liquid chromatography

A rapid and novel ultra-HPLC (u-HPLC) method for the determination of vitamins A (retinol) and E (alpha-, gamma-, and delta-tocopherol) in foods was validated in terms of its precision, accuracy, and linearity. The u-HPLC separation was performed on an RP C18 column (particle size 2 microm, id 2 mm, and length 75 mm), followed by fluorescence detection. The recovery of retinol was more than 84.58%; the LOD and LOQ of the u-HPLC analysis were 0.015 and 0.045 mg/kg, respectively. The intraday and interday precision was less than 9.12%. The recoveries of alpha-, gamma-, and delta-tocopherol were more than 81.37%; the LOD and the LOQ were 0.014, 0.002, and 0.001 mg/kg and 0.042, 0.005, and 0.004 mg/kg, respectively. All calibration curves had good linearity (r2 = 0.99) within the test ranges. The novel, rapid method coupled to u-HPLC can provide significant improvements in the speed, sensitivity, and resolution compared with a conventional HPLC method.     

Validation of a method for the determination of multiclass pesticide residues in fruit juices by liquid chromatography/tandem mass spectrometry after extraction by matrix solid-phase dispersion

A multiresidue method was developed and validated for the determination of pesticide residues (omethoate, dimethoate, carbendazim, propoxur, thiabendazole, carbaryl, pirimicarb, azinphos-methyl, methidathion, and iprodione) in fruit juices. The samples were extracted by matrix solid-phase dispersion with diatomaceous earth and analyzed by liquid chromatography/tandem mass spectrometry. The method detection limits were <0.2 ppb for all pesticides; the relative standard deviations for analyses of samples fortified over the range of 2-50 ng/g were <9%, and the recoveries for each pesticide were all between 77 and 102%. The proposed method was used to analyze 21 commercial fruit juices; pesticide residues were found in 71% of the samples.     

Fast and precise determination of phenthoate and its enantiomeric ratio in soil by the matrix solid-phase dispersion method and liquid chromatography

A fast and precise method was developed for the determination of phenthoate and its enantiomeric ratio (ER) in three soil samples. A recently developed sample pretreatment technology--matrix solid-phase dispersion (MSPD) was used to extract phenthoate simply and effectively. MSPD conditions, i.e. solid-phase Florisil amount, water content of Florisil-soil mixture, the constituent and volume of the eluting solvent, were optimized stepwise. The MSPD extract was directly used for quantitative determination of phenthoate by silica-based high-performance liquid chromatography (HPLC) with UV detection. The recoveries of phenthoate from three different types of soils fortified at three levels of 0.1, 1, 10 microg/g ranged from 75 to 94% with RSDs of 1.5-6.5%. On this basis, phenthoate was further isolated from the remainder of MSPD extract by silica-based HPLC and then ER determined on HPLC with cellulose tris-3, 5-dimethylphenylcarbamate as chiral stationary phase. The ERs determined in the soils spiked with racemic or enantiomer-enriched phenthoate agreed sufficiently well with those in the corresponding standard solutions. Finally, the proposed method was successfully applied to the study of enantioselective degradation of phenthoate in the three soils under laboratory conditions. High enantioselectivity was observed in the two alkaline soils with (+)-enantiomer degrading faster than the (-)-enantiomer, while there was little to no enantioselectivity in the acidic soil. The methodology can be used to study the enantioselective environmental behavior of chiral pollutants.     

底物固相分散法测定土壤中甲氰菊酯残留量

以甲氰菊酯为分析对象，将一种新型的样品预处理技术-底物固相分散法(MSPD)应用于测定土壤中农药残留。确定了MSPD法的实验条件：土壤量为4g，水的加入量为1mL，固相吸附剂弗罗里硅土的用量为10．0g，淋洗剂为15mL石油醚-乙酸乙酯(1 9)。土壤样品在此条件下处理后无需进一步净化即可用气相色谱／电子捕获检定器测定。三种土壤的三种加标水平的回收率均在90％以上，相对标准偏差小于5％(n＝5)，最小检出质量比为0．002mg/kg。     

Determination of aflatoxins in peanuts by matrix solid-phase dispersion and liquid chromatography

A new method based on matrix solid-phase dispersion (MSPD) extraction was studied to determine aflatoxin B1, B2, G1 and G2 from peanuts. Optimization of different parameters, such as type of solid supports for matrix dispersion and elution solvents were carried out. The method used 2 g of peanut sample, 2 g of C18 bonded silica as MSPD sorbent and acetonitrile as eluting solvent. Recoveries of each aflatoxin spiked to peanut samples at 2.5 ng/g (5 ng/g for aflatoxin G2) level were between 78 and 86% with relative standard deviations ranging from 4 to 7%. The limits of quantification ranged from 0.125 to 2.5 ng/g for the four studied aflatoxins using liquid chromatography (LC) with fluorescence detection. In addition, LC coupled to mass spectrometry with an electrospray interface was used for confirmation of aflatoxins present in real samples. Eleven peanut samples from different countries were analyzed by the proposed method and by using an enzyme-linked immunosorbent assay (ELISA). ELISA test is a good screening method for investigation of these mycotoxins in peanut samples.     

Ultrasound-assisted matrix solid-phase dispersive liquid extraction for the determination of intermediates in hair dyes with ion chromatography

A novel one-step sample preparation technique called ultrasound-assisted matrix solid-phase dispersive liquid extraction was developed. After sample matrices being dispersed, target analytes were extracted into acid solutions and fat and lipin were dissolved in n-hexane while the interfering components were retained by dispersing sorbent. The extraction process could be rapidly accomplished within 9 min with high sample throughput under the synergistic effects of vibration, ultrasound action and heating. The extraction efficiency of approach was demonstrated for the determination of intermediates in commercial hair dyes with ion chromatography. Linearity ranges of 0.2–100 mg L⁻¹ and detection limits varying from 0.019 to 0.048 mg L⁻¹ were achieved. The recoveries ranged from 85.7 to 107.0% with the relative standard deviations (RSDs) of 0.31–3.7%. These results showed that the method was simple, time-saving, reliable and suitable for the routine analysis of intermediates in large numbers of hair dyes.     

Automated solid-phase extraction method for the determination of piperaquine in plasma by peak compression liquid chromatography

A validated bioanalytical method for the determination of piperaquine (PQ) in plasma by solid-phase extraction (SPE) and liquid chromatography (LC) using peak compression is presented. Protein is precipitated from plasma with acetonitrile-1% aqueous acetic acid (85:15, v/v). An internal standard (IS) is added to the samples before they are loaded onto a strong cation exchanger (Isolute PRS) SPE column. PQ and the IS are analyzed by LC on a Zorbax SB-CN column (250 x 4.0 mm) with the mobile phase acetonitrile-phosphate buffer [I = 0.1, pH 2.5 (12:88, v/v)] and UV detection at 345 nm. Trichloroacetic acid (TCA) is added to the samples prior to injection into the chromatography system. PQ elutes in a gradient of TCA, which enables peak compression of PQ and significantly higher peak efficiency as a result. The intraassay precision for plasma is determined to be 5.4% at 3.00 microM and 5.8% at 0.050 microM. The interassay precision for plasma is 1.3% at 3.00 microM and 10.0% at 0.050 microM. The lower limit of quantitation and the limit of detection are 0.025 and 0.005 microM, respectively.