Reaction between Zinc and Hydrochloric Acid in Solutions Containing Alkyltrimethylammonium Bromide CnTAB (n = 8, 10, and 12) Cationic Surfactants: Influence of Surfactant Chain Length

The influence of C_nTAB cationic surfactant chain length (n = 8, 10, and 12) on the reaction rate of zinc powder and 0.1 M HCl hydrochloric acid in aqueous solutions was determined at room temperature. Solutions of single surfactants consisting of dodecyl, decyl, and octyl-trimethyl-ammonium bromide surfactants C_nTAB were prepared at room temperature. From the surface tension and conductivity measurements, the critical micelle concentration (CMC) values of the three surfactants were obtained in the presence and absence of the acid. No significant change was observed for CMC values in pure water and in 0.01 M HCl. Adsorption of C_nTAB surfactants onto 1% wt./vol zinc (in powder form), using surface tension measurements, was then investigated. The adsorption tendency of C_nTAB surfactants onto zinc powder followed the order: C₈TAB > C₁₀TAB > C₁₂TAB. The role of surfactants in the reaction rate between zinc powder and 0.1 M M HCl was then investigated using conductivity measurements. A significant difference in the reaction rate was found depending on the surfactant chain length. Reaction times of 3830, 4963, 14,172, and 20,053 s were found for the zinc reaction with (0.1 M HCl), (0.1 M HCl + 40 mM C₈TAB), (0.1 M HCl + 40 mM C₁₀TAB), and (0.1 M HCl + 40 mM C₁₂TAB), respectively, suggesting a significant dependency of the reaction rate on the C_nTAB chain length. Finally, some corrosion parameters such as the corrosion rate, corrosion inhibition efficiency, and their dependency on C_nTAB chain length were presented and discussed.     

高效毛细管电泳分离水样中的硝基苯类化合物

利用高效毛细管电泳（HPCE）同时分离水样和印染废水中的3,5-二硝基苯甲酸、对硝基苯甲酸、对硝基苯酚等硝基苯化合物。通过考察缓冲液类型及浓度（10~50mmol.L-1）、pH值（7.0~9.5）、分离电压（10~30kV）、进样时间（2~10s）等因素对分离效果的影响,建立了水样中硝基苯类化合物的快速分离测定方法。得到的合适的电泳条件为硼砂缓冲液20mmol.L-1、pH值9.2、电泳电压25kV、进样时间4s。将该分离方法应用于实际印染废水中的硝基苯类化合物的分离测定,结果表明该方法快速、准确、重现性好。     

Malonaldehyde determination in tissues and biological fluids by ion-pairing high-performance liquid chromatography

A method for the analysis of malonaldehyde by ion pairing high-performance liquid chromatography is described. The method is direct; no thiobarbiturate chromogen formation is required, and sample preparation is simple. After deproteinization with 50% ethanol and removal of particulate by centrifugation samples were passed through a small silica amino column to remove contaminants. Diluted samples (20 μL) were injected onto an octadecylsilane column (25 cm×4.6 mm ID, 5 μm) which is eluted with 30 mM sodium phosphate buffer, pH 6.5 containing 30% ethanol and 1 mM tetradecyltrimethylammonium bromide. Detection was accomplished by monitoring absorbance at 267 nm. The lower limit for reliable quantification was 5 pmol per injection. The method has been successfully applied to the quantification of malonaldehyde present in plasma, urine and tissues of rats kept under different dietary conditions as well as afterin vivo treatment with CCl₄ and iron-dextran. The method was also applied to the quantification of malonaldehyde during liver microsomal lipid peroxidation and was compared to the thiobarbituric acid test. Bureau of Nutritional Sciences Publication No. 348.     

Characterization of α- and γ-linolenic acid oils by reversed-phase high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry

Triacylglycerols of oils rich in α- and/or γ-linolenic acids were analyzed by reversed-phase high-performance liquid chromatography (HPLC) coupled with atmospheric pressure chemical ionization mass spectrometry [(APCI)MS]. The (APCI)MS spectra of most triacylglycerols exhibited [M + H]⁺ and [M - RCOO]⁺ ions, which defined the molecular weight and the molecular association of fatty acyl residues, respectively. Reversed-phase HPLC resulted in, at least, partial separation of triacylglycerols containing α- and/or γ-linolenic acid moieties. Molecules containing α-linolenic acid residues exhibited a relatively weaker retention by the stationary phase than the corresponding molecules containing γ-linolenic acid residues. Good separation of triacylglycerols of cloudberry seed oil, evening primrose oil, borage oil, and black-currant seed oil was achieved. The molecular species identification of separated components was based on the (APCI)MS data as well as on the elution properties of triacylglycerols on reversed-phase HPLC. This study demonstrated the efficiency of HPLC-(APCI)MS in determining the molecular species compositions of triacylglycerols in complex natural mixtures. Good quality mass spectra could be extracted even from minor chromatographic peaks representing 0.2% or less of the total triacylglycerols.     

胶束毛细管电泳快速分离八种农药类环境内分泌干扰物

建立了八种农药类环境内分泌干扰物的胶束毛细管电泳快速分离方法。优化出的毛细管电泳分离条件为：缓冲溶液为含50mM十二烷基硫酸钠（SDS）和5％乙腈的15mM硼砂溶液（pH=8．7）,毛细管有效长度31．5cm,分离电压30kv,在各组分的最大吸收波长下采用二极管阵列检测器检测。各组分在5min内获得完全分离,迁移时间的相对标准偏差在1．1～2．1％之间。     

Microscale synthesis of phosphatidyl-[3H]choline from 1,2-diacylglycerol. Assessment of isomerization by reversed-phase high-performance liquid chromatography

The synthesis ofrac-1-palmitoyl-2-oleoylglycero-3-phospho-[³H]choline of high specific activity was carried out on a microscale by making 7 μmol ofrac-1-palmitoyl-2-oleoylglycerol react first with an equimolar amount of POCl₃ and then of [³H]choline. After purification by thin-layer chromatography and normal-phase high-performance liquid chromatography (HPLC), the yield of the synthesis of [³H]phosphatidylcholine (120 μCi/μmol) was 22%.rac-1-Palmitoyl-2-oleoylglycerol was purified before use by reversed-phase HPLC under conditions which were nonisomerizing and allowed the separation of 1,2- and 1,3-isomers of diacylglycerol. Ethanol, but not benzene, was shown to cause isomerization of long-chain diacylglycerol and, therefore, was not used for drying the substrate before reaction. A rapid and complete separation of 1,2- and 1,3-isomers of long-chain phosphatidylcholine was obtained by reversed-phase HPLC using 20 mM choline chloride in methanol/acetonitrile/water (50∶50∶1, by vol) isocratically as the mobile phase. Under these conditions, analysis of the synthetizedrac-1-palmitoyl-2-oleoylglycero-3-phospho-[³H]choline showed a total absence of 1,3-isomer.     

Separation of bile acid methyl esters by high-performance liquid chromatography

Conjugated bile acids, namely glyco- and tauro-3α,6α-dihydroxy-5β-cholanoic acid (hyodeoxycholic acid), 3α,7α-dihydroxy-5β-cholanoic acid (chenodeoxycholic acid), 3α,6α,7α-trihydroxy-5β-cholanoic acid (hyocholic acid) and 3α-hydroxy-6-oxo-5β-cholanoic acid (6-keto-litocholic acid) were isolated from pig bile, and subsequently transformed into the corresponding methyl esters. Separation of the methyl esters of the isolated bile acids by high-performance liquid chromatography (HPLC) was accomplished on a ZORBAX-CN column (Dupont, Boston, MA) withn-hexane/2-propanol/methylene chloride (89∶6∶5, by vol) as the mobile phase containing traces (≈1%) of amyl alcohol and water as moderators. HPLC analysis of the methyl esters also showed the presence of methyl 3α-hydroxy-6-oxo-5α-cholanoate, which was probably produced in the course of alkaline hydrolysis of the conjugated bile acids.     

Rapid analysis of oxidized cholesterol derivatives by high-performance liquid chromatography combined with diode-array ultraviolet and evaporative laser light-scattering detection

Extensive evidence of the deleterious biological effects of oxidized 5-cholesten-3β-ol (cholesterol) derivatives has led to great interest in their detection. We observed that known oxidized cholesterol derivatives can be rapidly quantitated by combining reversed-phase high-performance liquid chromatography (HPLC) with ultraviolet (UV) absorption and evaporative laser light-scattering (ELSD) detection. Using a 20 × 0.46 cm C18 HPLC column and methanol/acetonitrile (60:40, vol/vol) as the mobile phase at 1.0 mL/min, 10 species of oxidized cholesterol derivative were measured by UV (205, 234, and 280 nm) while 5-cholestan-5α,6α-epoxy-3β-ol (5α-epoxycholesterol), 5-cholestan-5β,6β-epoxy-3β-ol (5β-epoxycholesterol), and 5-cholestan-3β,5α,6β-triol (cholestanetriol) were detected by only ELSD. The minimal limits of detection ranged from 100 to 500 ng depending on sterol and detector. The response was linear in the range 0–1000 or 0–2000 ng depending on detector. These oxidized cholesterol derivatives were also identified by HPLC/mass spectrometry analysis combined with UV detector. Heated tallow contained cholestanetriol, 5-cholesten-3β,7α-diol (7α-hydroxycholesterol), 5-cholesten-3β,7β-diol (7β-hydroxycholesterol), 5-cholesten-3β-ol-7-one (7-ketocholesterol), 5α- and 5β-epoxycholesterols under the developed analysis condition. Photooxidized cholesterol had cholestanetriol, 7α- and 7β-hydroxycholesterols and 3,5-cholestadien-7-one. On the other hand, 7α- and 7β-hydroxycholesterols, 7-ketocholesterol, 5α- and 5β-epoxycholesterols and 3,5-cholestadien-7-one were observed in copper-oxidized low-density lipoprotein. Thus, this developed HPLC analysis method could be applied to identification of oxidized cholesterol derivatives in food and biological specimen.     

The pH-dependence of oxygen reduction on multi-walled carbon nanotube modified glassy carbon electrodes

The pH-dependence of oxygen electroreduction has been investigated on multi-walled carbon nanotube (MWCNT) modified glassy carbon (GC) electrodes. Various surfactants were used in the electrode modification: dihexadecyl hydrogen phosphate, cetyltrimethylammonium bromide, sodium dodecyl sulfate and Triton X-100. Electrochemical experiments were carried out in 0.5 M H₂SO₄ solution, acetate buffer (pH 5), phosphate buffers (pH 6, 7 and 8), borate buffer (pH 10), 0.01 M KOH, 0.1 M KOH and in 1 M KOH solution, using the rotating disk electrode (RDE) method. The oxygen reduction behaviour of MWCNT-modified GC electrodes at different pHs was compared. The RDE results revealed that the half-wave potential (E_1/2) of oxygen reduction was higher in solutions of high pH. At lower pHs (pH < 10) the value of E_1/2 did not essentially depend on the solution pH. A comparison with previous studies on bare GC showed that the pH-dependence of the half-wave potential of oxygen reduction on MWCNT-modified GC electrodes follows a similar trend to that observed for bare GC.     

Antioxidants from a heated histidine-glucose model system. I: Investigation of the antioxidant role of histidine and isolation of antioxidants by high-performance liquid chromatography

The radical-combining activity of Maillard reaction products [MRP_(aq)], produced by heating d-glucose and l-histidine (3:1) in a 0.1 M phosphate buffer for 10 h at 105°C (final pH 6.53), was estimated directly by means of a diphenylpicrylhydrazyl radical (DPPH^·) method. Additionally, the indirect methods of peroxide values changes (oven test), hexanal formation, and protection factors (Rancimat method) were determined on a lipid model system that consisted of sunflower seed oil/water (1:2), emulsified with 3% (w/w) Tween 40. Results from the DPPH^· method showed a potential antioxidant activity of MRP_(aq), which was confirmed by the indirect methods. Surprisingly, histidine in solution alone (heated or not) exhibited an antioxidant activity greater than or similar to the MRP_(aq) activity in the indirect methods with the lipid model system, in contrast to the results from the DPPH^· method. The suitability of various solvents for extraction of potential antioxidant compounds from freeze-dried MRP_(aq) was examined, and ethanol extracts showed the greatest activity by the DPPH^· method. Consequently, the ethanol extract of freeze-dried MRP_(aq) was separated by means of preparative reverse-phase high-performance liquid chromatography (HPLC) with a 0.05 M phosphate buffer (pH 4.4)/water/acetonitrile gradient system. The antioxidant activity of the eluate was measured through the DPPH^· method, and a fraction (Fraction A) with antiradical activity was further purified by preparative HPLC. Fraction B was collected, and its freeze-dried residue exhibited potent antiradical activity, significantly greater than that of the same level of n-propyl gallate.     

Micro method for stereospecific analysis of triacyl-sn-glycerols by chiral-phase high-performance liquid chromatography

A procedure for micro stereospecific analysis of triacyl-sn-glycerols (TGs) by high-performance liquid chromatography (HPLC) on a chiral column is presented. TGs were partially hydrolyzed with ethyl magnesium bromide, and total products were immediately converted to 3,5-dinitro-phenylurethane derivatives. Each of the 1- and 2-monoacylglycerol (MG) derivatives was isolated by HPLC on a silica column. The 1-MGs were resolved intosn-1 andsn-3 MG fractions by HPLC on a Sumichiral OA-4100 column (Sumitomo Chemical, Osaka, Japan). Fatty acid methyl esters obtained from thesn-1,sn-2 andsn-3 MG fractions were analyzed by gas-liquid chromatography on a capillary column. Analyses of standard TGs showed that, even with 1 mg of sample, accuracy was comparable to that obtained with 100-mg samples. Applying this procedure to the stereospecific analysis of 5 mg of jujube pulp, TGs revealed the positional distribution of the (n-5) series of monounsaturated fatty acids they contained. Honored Student Award Address presented at the 83rd AOCS Annual Meeting held in Toronto, Canada, May 10–14, 1992.     

Determination of surfactant mixtures in shampoos and detergents by HPLC

A technique for separating 4 nonionic, 7 anionic and 4 amphoteric surfactants with n-dodecyl groups was studied by high performance liquid chromatography (HPLC) and applied to the determination of these surfactants in commercial shampoos and household detergents. Conditions used for the separation were: column packing and size, TSK-LS 410 (5μ) and 6 mm i.d. × 500 mm (2 connected, 250 mm columns); mobile phase, water/methanol (25/75, v/v) containing 0.25 M sodium perchlorate adjusted to pH 2.5 with phosphoric acid; column temp., 50 C; detector, RI. Surfactants in shampoos and detergents were clearly distinguished from each other and determined without column chromatographic pretreatment, e.g., ion-exchange chromatography.     

Analysis of triacylglycerols by silver-ion high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry

Triacylglycerols of the seed oils rich in α- and/or γ-linolenic acid moieties were separated by silver-ion high-performance liquid chromatography (HPLC) followed by on-line atmospheric pressure chemical ionization-mass spectrometric (APCI-MS) detection. Mass spectra of most triacylglycerols exhibited abundant [M + H]⁺ and [M − RCO₂]⁺ ions, which defined the molecular weight and the molecular association of fatty acyl residues of a triacylglycerol, respectively. Silver ions formed weaker complexes with triacylglycerols containing γ-linolenic acid than with those containing α-linolenic acid, i.e., the elution order of molecules wasXYT _γ>XYT _α’,XT _γ T _α>XT _α T _α>, andT _γ T _γ T _γ>T _γ T _γ T _α>T _γ T _α T _α>T _α T _α T _α, whereT _α=α-linolenic acid,T _γ=γ-linolenic acid, andX, Y=fatty acids different from linolenic acid. Furthermore, silver-ion HPLC resulted in partial separation within equally unsaturated triacylglycerols according to differences in the combined number of acyl carbons. Regioisomeric forms of triacylglycerols were not determined from the seed oil samples, although differences were measured with reference compounds in the relative abundances of [M − RCO₂]⁺ ions formed by a loss of a fatty acyl residue from thesn-2 position and thesn-1/3 positions. Silverion HPLC/APCI-MS provided valuable information for structure elucidation of seed oil triacylglycerols: 43 molecular species were identified from cloudberry seed oil, 39 from evening primrose oil, 79 from borage oil, 44 from alpine currant, and 56 from black currant seed oils. The quantitation requires to be studied further, especially in those cases where several molecular weight species of triacylglycerols eluted in a single chromatographic peak.     

Thermophilic phospholipase A2 in the cytosolic fraction from the archaeon Pyrococcus horikoshii

Hyperthermophilic archaeon Pyrococcus horikoshii produced phospholipase A² in a cytosolic fraction. The enzyme displayed optimal activity at 90°C and pH 7 and preferentially hydrolyzed sn-2 fatty acids in the following order: linoleoyl> oleoyl>arachidoyl phosphatidylcholine. Phospholipase A₂ had similar activities toward l-α-1-palmitoyl-2-arachidoyl derivatives of phosphatidylcholine and phosphatidylethanolamine. Phospholipase A₂ activity was unaffected by the addition of 0.0001–1 mM calcium, but was inhibited slightly by the addition of 2–10 mM calcium. The activity was enhanced more than 5–18-fold in the presence of 3–20% (vol/vol) glycerol. The activity was unaffected by the addition of 1–5 mM EDTA or 0.01–20 mM dithiothreitol. A caldarchaetidic acid derivative having a molecular weight of 1544 disappeared upon incubation of the cytosolic fraction with total lipid. The phospholipase A₂ was difficult to purify by general chromatography because it existed as an aggregate. Electrophoresis was carried out using 10–15% polyacrylamide gels containing sodium dodecyl sulfate (SDS-PAGE). No activity of phospholipase A₂ activity was observed in the absence of proteins less than 19 kD in size, as fractionated by SDS-PAGE. Portions of this article were presented at the Biocatalysis Symposium at the 91st Annual Meeting and Expo of the American Oil Chemists’ Society in San Diego, CA, April, 2000.     

Effect of pH on Separation Performances in High-Performance Liquid Chromatography of Antibacterial Peptides from the Spleen of Japanese eel,Anguilla japonica

The present study was made to determine the optimum pH for isolating antibacterial peptides from the spleen of Japanese eel, Anguilla japonica, by high-performance liquid chromatography (HPLC). The recovery rates of the peptides were investigated by using buffers with three pH values (pH 3, pH 4, and pH 5) in ion-exchange chromatography (IEC) of the spleen protein sample with the molecular weight (MW) < 10 kDa. Following this, for the fractions obtained from IEC, we continued to study the effect of four pH values (pH 2, pH 7, pH 9, and pH 12) on the separation efficiency in reverse-phase high-performance liquid chromatography (RP-HPLC). The results showed using the buffer with pH 4 in IEC could achieve the highest rate of recovery, which was 5.4 fold to that of pH 3 and 1.36 fold to that of pH 5. The treatment at high pH value (pH 9) did significantly affect the chromatographic separation behaviors, which produced more than twice the peak numbers than those in other three pH values. The optimized pH would be helpful for isolating antibacterial peptides from the spleen of eel.     

Effects of octylglucoside and triton X-100 on the kinetics and specificity of carnitine palmitoyltransferase

The effects of octylglucoside on the substrate specificity, kinetics and aggregation state of purified carnitine palmitoyltrasferase (CPT) from beef heart mitochondria were investigated and compared to the effects of Triton X-100. Conditions in which CPT can be assayed in the absence of micelles and albumin, thereby eliminating miceller effects on the kinetic parameters, are described. When octylglucoside is substituted for Triton X-100, the specificity of CPT in the forward direction shifts towards the long-chain acyl-CoAs, and large changes in the kinetic constants are observed. The K_0.5 for L-carnitine varied as much as 50-fold, depending on the acyl-CoA and detergent used. At pH 8.0 and 200 μM palmitoyl-CoA, the K_0.5 for L-carnitine is 4.9 mM in 12 mM octylglucoside and 0.2 mM in 0.1% Triton X-100. Octylglucoside enhances the activity of CPT with long-chain acyl-CoA and lowers the K_0.5 for these substrates. At pH 6.0, the K_0.5 for palmitoyl-CoA is 24.2 μM in 0.1% Triton X-100, in contrast to 3.1 μM in 12 mM octylglucoside. Octylglucoside is a competitive inhibitor of CPT with octanoyl-CoA as substrate with a K_i of 15 mM. Nonlinear kinetics for both acyl-CoAs and L-carnitine are observed when the concentration of octylglucoside is reduced to less than half of its critical micellar concentration (cmc). Gel filtration of CPT in octylglucoside below its cmc gives a single protein peak with a molecular mass of ca. 660,000 daltons. These data indicate that the catalytically active form of purified CPT is an aggregate that has quaternary structure and must have a very flexible catalytic site whose affinity for substrate and catalytic efficiency can be altered greatly by changes in environment and experimental conditions.     

Determination of (+)-, (−)-, and total gossypol in cottonseed by high-performance liquid chromatography

Gossypol, a pigment in cottonseed, is a polyphenolic, binaphthyl dialdehyde. Due to steric hindrance between the functional groups of the molecule at the bond connecting the two naphthyl rings, gossypol exists as (+)- and (−)-isomers. Gossypol is physiologically active with the (−)-isomer appearing to be more active and causing temporary infertility in males. It is thus important to know the amounts of isomers in livestock feeds. A quantitative high-performance liquid chromatography (HPLC) procedure was developed for the separation of (+)- and (−)-gossypol contained in cottonseed. This method involves derivatization of gossypol with (R)-(−)-2-amino-1-propanol followed by HPLC separation employing either a Phenomenex Prodigy (5 μ, ODS-3, 100 × 3.2 mm) or a MetaChem Inertsil (5 μ, ODS-3, 100 × 3.0 mm) reversed-phase column eluted with 80% acetonitrile and 20% 10 mM KH₂PO₄ adjusted to pH 3.0 with H₃PO₄ at 1.0 mL/min. The (+)- and (−)-gossypol-2- amino-1-propanol complexes eluted at roughly 1.4 and 2.6 min, respectively. It was found that gossypol from Upland (Gossypium hirsutum) seed was rich in the (+)-enantiomer, with the (+)- and (−)-enantiomers in a ratio of about 65:35, respectively, while gossypol from the seed of a Pima (G. barbadense) cultivar (S-6) was slightly richer in the (−)-enantiomer (46.8:53.2). Deceased.     

黄芩药材的毛细管电泳指纹图谱研究

采用毛细管电泳方法建立黄芩不同产地药材的指纹图谱。考查多种提取方法提取黄芩药材中黄芩苷的提取率;研究运行缓冲液的浓度和酸度、检测波长及分离电压对黄芩药材指纹图谱的影响,得到了优化的测定条件(50mmol/L硼砂缓冲液,pH值7.94,分离电压为20kV,柱上254nm紫外检测)。进行精密度和重现性实验,各共有峰相对峰面积和相对保留时间的RSD均小于5%。最后利用相似度和聚类分析两种方法对10批黄芩药材的毛细管电泳指纹图谱进行分析,结果与实际样品分类相符合。     

New amphoteric surfactants containing a 2-hydroxyalkyl group VIII. Synthesis and surface activities for amphoteric oligomeric or polymeric surfactants of β-alanine type

A series of amphoteric oligomeric and polymeric surfactants of poly(iminoethylene) (PIE) containing both a 2-hydroxyalkyl group (C₁₂-HA or C₁₄-HA) and a 2-carboxyethyl (CE) group as N-substituents was studied as follows: PIE having 1,000 or 20,000 molecular weight was treated with 1,2-epoxydodecane or 1,2-epoxytetradecane and subsequently methyl acrylate. The adducts were saponified to obtain amphoteric oligomeric surfactants (AO) or amphoteric polymeric surfactants (AP), poly{[N-(2-carboxyethyl)-N′-(2-hydroxyalkyl)]iminoethylene}. Various adducts of which the ratios of CE/HA for one unit of iminoethylene group are 2, 3.5, 8, 17 and 89 were synthesized. Surface activities such as surface tension, solubilization of orange OT, and foaming power, and physicochemical properties such as turbidity, isoelectric point, and the dissociation constant, were studied. Particular attention was paid to the dependence of solubilization, viscosity and turbidity on pH value.     

Separation of tripalmitin from its hydrolysis products by simple isocratic reversed-phase high-performance liquid chromatography

An isocratic reversed-phase high-performance liquid-chromatographic method was developed for monitoring the lipase-catalyzed hydrolysis of solid triglycerides in supercritical carbon dioxide. The reaction products obtained consist of free fatty acids, monoglycerides, diglycerides, and unreacted triglycerides. For the method, developed with tripalmitin, a mobile phase of acetonitrile/chloroform/acetic acid (50:50:1, vol/vol/vol), a C₁₈ column, and refractive index detection were used. Analysis time is 7 min. Response factors were determined for each neutral lipid class, which permitted quantitation of the hydrolysis product mixture.