Methanol calibration curve

Fig. 38 Companson of manual dipping (A) with mechanized dipping (B) on the basis of scans and calibration curves [114] — 1 = cM-diethylstilbestrol, 2 = traw-diethylstilbestrol, 3 = ethinylestradiol Scanning curve 2 ng of each substance per chromatogram zone = 313 nm, /n > 390 nm Dipping solution water — sulfuric acid — methanol (85 + 15 + 1)...

Two linear columns from Showa Denko, Shodex SB-806M and Shodex SB-806MHQ, and two linear columns from TosoHaas, TSK GM-PWxl and TSK GM-PW, were evaluated. Prior to the evaluation, the number of theoretical plates for Shodex SB-806MHQ, SB-806M, PWxl, and PW was determined to be 15,100, 15,700, 11,390, and 4710, respectively, as per manufacturer inspection. The lower plate count of the TSK PW column is due to the larger particle size of this column. Two mobile phases, water with 0.1 M LiNOi and 50 50 methanol/water (v/v) with 0.1 M LiNOi, were used for each of the four columns. These four columns were new and only PEO and PVP were analyzed with these columns in this study. Waters Ultrahydrogel columns have also been used in this laboratory. However, Ultrahydrogel columns are exactly the same as the TSK GM-PWxl columns based on the calibrations curves supplied by the manufacturers and by the pyrolysis GC data discussed later. 

Due to the limitation of space, only the linear calibration curves for TSK, PSS, APSC, and PL PEO standards in water/methanol for the Shodex SB-806M... 

For all four sets of PEO standards the coefficient of determination (R ) for the linear calibration curves for the four linear columns in water and in water/methanol are better than 0.99, except for the PL PEO standards and the TSK GM-PWxl column in water/methanol. The coefficient of determination for the TSK GM-PWxl column in general is not as good as the other three linear columns. The coefficient of determination for the TSK PEO standards showed the least dependency on columns and mobile phases. The TSK GM-PWxl column has a lower exclusion limit in the high molecular weight range than TSK GM-PW, Shodex SB-806, and SB-806MHQ columns. 

Prepare an alkaline solution of the phenol concentrate by placing 4.0 mL of a tri-n-butyl phosphate layer in a 5 mL graduated flask and then adding 1.0 mL of the tetra-n-butylammonium hydroxide do this for each of the four solutions. The reference solution consists of 4 mL of the organic layer (in which the phenol is undissociated) plus 1 mL of methanol. Measure the absorbance of each of the extracts from the four test solutions and plot a calibration curve. 

Figure 5.60 Calibration curves for the diarrhetic shellfish poisons in (i) standard solutions in methanol (O), and (11) standard solutions in poison-free scallop extract solutions ( ) (a) pectenotoxin-6 (b) okadaic acid (c) yessotoxin (d) dinophysistoxin-1. Reprinted from J. Chromatogr., A, 943, Matrix effect and correction by standard addition in quantitative liquid chromatographic-mass spectrometric analysis of diarrhetic shellfish poisoning toxins , Ito, S. and Tsukada, K., 39-46, Copyright (2002), with permission from Elsevier Science.

The calibration curves were prepared by using DSPs standard solutions in methanol. 

Measure the intensity of molar extinction at 302 nm against that of a blank soluhon prepared by diluting 15 mL of methanolic KOH to 25 mL with methanol. Determine the carbon disulhde content from a calibration curve obtained by plothng the carbon disulhde concentrations of different standard solutions on the abscissa versus the absorbance on the ordinate. 

The anhydride derivatives obtained as above are dissolved in an appropriate volume of methanol, and a 10-pL aliquot of each solution is injected into the pre-conditioned HPLC system. The peak heights of the fluorescent derivatives of M.A3 and M.A4 are converted to weight using a calibration curve corresponding to each chemical. 

Quantitation is performed by the calibration technique. A standard solution containing 0.1 mgkg of both M.A3 and M.A4 is prepared and 1, 2.5, 5 and 7.5mL of this solution are pipetted into around-bottom flask separately and evaporated. Each sample is converted into the fluorescent anhydride derivative according to the procedures described above. Each sample is dissolved in lOmL of methanol for injection into the HPLC system. The calibration curves are obtained by plotting the peak heights against the amounts of M.A3 and M.A4. The derivatives for preparing the calibration curve should be freshly prepared on a daily basis prior to quantitation. 

Three methods for quantitative analysis of niclosamide at concentrations of 0.5-2.0 ppm were given. For in situ analysis, safranine dye solution was added to the sample and the extraction solution added which formed the upper phase. The niclosamide content was determined by the color intensity of the upper phase. The colors were compared with blanks of known concentration. When an accurate determination was required, niclosamide was extracted from the water sample with amylacetate, a methanol solution of sodium hydroxide was added to the extraction, and the resulting yellow color was measured at 385 mft in a spectrophotometer. Third method made use of a calibration curve [60],... 

Standards, controls, and samples (250 fiL each) were treated with 500 fiL acetonitrile-acetic acid (99 1 v/v) containing IS (2.50 jUg/mL), vortexed for 10 sec, incubated for 5 min, and centrifuged at 15,000 g for 5 min. The supernatants (1650 //L) were loaded onto a polypropylene 96-well plate containing 900 fxL HPLC water under low vacuum. The SPE plates were conditioned with 500 fxL methanol followed by 300 jx. acetonitrile-water-acetic acid (30 69.5 0.5 v/v/v) (solvent A), washed with 1000 /xL solvent A, dried under full vacuum for 10 min, wiped dry with paper, eluted with 500 jxL methanol-trifluoroacetic acid (99.9 0.1 v/v) (solvent B) and then with 400 //L solvent B for 2 min, evaporated to dryness at 65°C under a gentle air stream, reconstituted with 200 /xL methanol-hydrochloric acid (0.1 M) (70 30 v/v) and assayed. The injection volume was 50 i L. Figure 11.3 shows chromatograms of blank plasma and spiked plasma with lumefantrine. A calibration curve was constructed in a concentration range of 25 to 20,000 ng/mL. Intra-assay and interassay coefficients of variation were below 5.2 and 4.0%, respectively. The limit of detection was 10 ng/mL. The limit of quantification was 25 ng/mL. 

Prepare standard solutions of 0, 25, 50, 75, and 100% methanol in deionized water. (Note 0% is only deionized water and 100% is only methanol.) Optional Additional standard solutions may be prepared to provide more data for the calibration curve, e.g., 10, 20, 30%, etc. 

Using the calibration curve, find the concentration of the methanol in the unknown. 

The assay was carried out using a Varian gas chromatograph (model 5000 LC) under the following experimental condition. The oven injector and flame ionization detector temperatures were 125°C and 225°C respectively. A Porapak column was used, the eluent was N2 at a flow rate of 30 ml/min and the injected volume 2 pi. Various concentrations of purified methylene chloride in purified methanol were injected (both solvents were distilled to discard any impurity which might interfere with the sensitive assay). Calibration curves were linear in the range 50-500 ppm (the limit of detection was 10 ppm). Methylene chloride detection in the microspheres was performed by dissolving various amounts (20-200 mg) of microspheres in 220 ml of purified methanol prior to the injection. 

Procedure. A primary standard solution of benzidine in methanol was prepared. Standards of lower concentrations were prepared by dilution of the primary standard. Typical liquid chromatograph calibration curves were linear in the region from .38 to 30.6 yg/mL. The standards were stable for several months when stored in the dark. Aqueous solutions of known dye-formulation concentration were prepared. 

The optimised experimental conditions, 5% methanol, 5 pg/ml NBS and AA, incubations 10 min for NBS and AA and 30 min for AChE, were then used to build a calibration curve in the concentration range 25-1000 ng/ml. Each standard was measured in triplicate and the calibration was repeated with three different electrodes. The intra-electrode CV ranged between 1.6 and 15.0 whereas the inter-electrode CV comprised between 4.6 and 16.0. 

A sensitive, simple, and specific liquid chromatographic method coupled with electrospray ionization-mass spectrometry for the determination of donepezil in plasma was developed, and its pharmacokinetics in healthy, male, Chinese was studied [34]. Using loratadine as the IS, after extraction of the alkalized plasma by isopropyl alcohol-n-hexane (3 97, v/v), solutes are separated on a Cig column with a mobile phase of methanol-acetate buffer (pH 4.0) (80 20, v/v). Detection is performed with a TOF mass spectrometer equipped with an electrospray ionization source operated in the positive-ionization mode. Quantitation of donepezil is accomplished by computing the peak area ratio (donepezil [M + H](+) m/z 380-loratadine [M + H](+) mlz 383) and comparing them with the calibration curve (r = 0.9998). The linear calibration curve is obtained in the concentration range 0.1-15 ng/ml. The limit of quantitation is 0.1 ng/ml. The mean recovery of donepezil from human plasma is 99.4 6.3% (range 93.4-102.6%). The inter- and intra-day RSD is less than 15%. After an oral administration of 5 mg donepezil to 20 healthy Chinese volunteers, the main pharmacokinetic parameters of donepezil are as follow T(max), 3.10 0.55 h tV2j 65.7 12.8 h C(max), 10.1 2.02 ng/ml MRT,... 

Sultana et al. [88] developed a reversed-phase HPLC method for the simultaneous determination of omeprazole in Risek capsules. Omeprazole and the internal standard, diazepam, were separated by Shim-pack CLC-ODS (0.4 x 25 cm, 5 m) column. The mobile phase was methanol-water (80 20), pumped isocratically at ambient temperature. Analysis was run at a flow-rate of 1 ml/min at a detection wavelength of 302 nm. The method was specific and sensitive with a detection limit of 3.5 ng/ml at a signal-to-noise ratio of 4 1. The limit of quantification was set at 6.25 ng/ml. The calibration curve was linear over a concentration range of 6.25—1280 ng/ml. Precision and accuracy, demonstrated by within-day, between-day assay, and interoperator assays were lower than 10%. 

A sensitive and rapid chromatographic procedure using a selective analytical detection method (electrospray ionization-mass spectrometry in SIM mode) in combination with a simple and efficient sample preparation step was presented for the determination of zaleplon in human plasma. The separation of the analyte, IS, and possible endogenous compounds are accomplished on a Phenomenex Lima 5-/rm C8(2) column (250 mm x 4.6 mm i.d.) with methanol-water (75 25, v/v) as the mobile phase. To optimize the mass detection of zaleplon, several parameters such as ionization mode, fragmentor voltage, m/z ratios of ions monitored, type of organic modifier, and eluent additive in the mobile phase are discussed. Each analysis takes less than 6 min. The calibration curve of zaleplon in the range of 0.1-60.0 ng/ml in plasma is linear with a correlation coefficient of >0.9992, and the detection limit (S/N = 3) is 0.1 ng/ml. The within- and between-day variations (RSD) in the zaleplon plasma analysis are less than 2.4% (n = 15) and 4.7% (n = 15), respectively. The application of this method is demonstrated for the analysis of zeleplon plasma samples [14]. 

The independent measurements of surface tension were obtained by the tedious Wilhelmy plate method. Figure 3 illustrates such a calibration curve for one set of orifices and for five types of test fluids (methanol-water, ethanol-water, acetone-water, sodium lauryl sulfate in water saturated with methyl methacrylate, and polymethylmethacrylate latices). This is a "universal" calibration curve independent of the fluid being monitored. For the 63 data points shown in Figure 3, the least squares regression line is given by... 

The decarboxylated product of moxalactam (see Section 4) is determined by an HPLC technique. A reverse phase HPLC system consisting of 80 parts of 0.1M ammonium acetate and 20 parts of methanol is used with a Dupont Zorbax C8 or other suitably similar column to determine the decarboxylated product. In this system, the decarboxylated moxalactam should elute with a k of about 6.5. The decarboxylated moxalactam is quantitatively determined by comparing the peak response for the sample with a peak response calibration curve of the authentic decarboxylated moxalactam reference standard material. 

First-derivative spectroscopy was applied to the analysis of mixture of spironolactone and frusemide in combined dosage forms [19], Calibration curves were linear up to 20 pg/mL. The same mixture has been analyzed by extraction with methanol, and subsequent measurement in either 0.1 N HC1 or in 0.1 N NaOH [20], The relative standard deviation was in the... 

De Ruiter et al. [4] observed that photochemical decomposition by ultraviolet irradiation of dansyl derivatives of chlorinated phenolic compounds in methanol-water mixtures led to the formation of highly fluorescent dansyl-OH and dansyl-OH3 species. The optimal irradiation time was 5.5s. This reaction was utilised in a post-column photochemical reactor in the high performance liquid chromatography determination of highly chlorinated phenols in river water. The method calibration curve (for dansylated pentachlorophenol) was linear over three orders of magnitude. 

Water analysis can be routinely carried out by a Karl-Fischer analysis in which the ionic liquid is diluted in methanol before analysis. A spiking approach can be used to produce a calibration curve that allows for background effects. At very low levels of water (<10ppm) quite substantial sample sizes can be needed for this method to be meaningful. 

Physical and chemical effects can be combined for identification as sample matrix effects. Matrix effects alter the slope of calibration curves, while spectral interferences cause parallel shifts in the calibration curve. The water-methanol data set contains matrix effects stemming from chemical interferences. As already noted in Section 5.2, using the univariate calibration defined in Equation 5.4 requires an interference-free wavelength. Going to multivariate models can correct for spectral interferences and some matrix effects. The standard addition method described in Section 5.7 can be used in some cases to correct for matrix effects. Severe matrix effects can cause nonlinear responses requiring a nonlinear modeling method. 

Ash is a measure of residual sodium acetate. A simple method consists of dissolving the PVA in water, diluting to a known concentration of about 0.5 wt %, and measuring the electrical conductivity of the solution at 30°C. The amount of sodium acetate is established by comparing the result to a calibration curve. A more lengthy method involves the extraction of the PVA with methanol using a Soxhlet extractor. The methanol is evaporated and water is added. The solution is titrated using hydrochloric acid in order to determine the amount of sodium acetate. 

It was used Sparteine, from Sigma, as an internal standard, and the final concentration of Sparteine in the samples was 0.102 g/1. The lupanine used to make the calibration curves of the chromatograph was extracted from the lupine flour using methanol and separated by using the thin-layer chromatography, according the method described by Cho and Martin (1971). 

Standardization The molar absorption coefficient of hydroxyalkenals in water and ethanol or methanol is 13 750 at 223 nm and 13 100 at 221 nm, respectively (Esterbauer, 1982). Calibration curves of peak height versus concentration are linear in the range 0.1-500 /iM. 

---