Solvent blanks

A double-beam atomic absorption spectrophotometer should be used. Set up a vanadium hollow cathode lamp selecting the resonance line of wavelength 318.5 nm, and adjust the gas controls to give a fuel-rich acetylene-nitrous oxide flame in accordance with the instruction manual. Aspirate successively into the flame the solvent blank, the standard solutions, and finally the test solution, in each case recording the absorbance reading. Plot the calibration curve and ascertain the vanadium content of the oil. 

Following the same procedures described in the above-mentioned study, additional extractive data were obtained for the epoxy phenolic enamel that was irradiated at 4.7-7.1 Mrad at 25 and — 30 °C in the presence of distilled water, 3% acetic acid, and n-heptane. The changes in the amount of extractives resulting from the irradiation treatment are shown in Table IX. In the case of the water and acetic acid extractives, there was no change in either the chloroform-soluble fractions or the chloroform-insoluble fractions. In the case of the n-heptane extractives, the amount of extractives decreased when the irradiation temperature was reduced from +25 to — 30°C. Infrared spectra of the chloroform-soluble residues from the water and acetic acid extractives of the unirradiated and irradiated enamel were identical to the chloroform-soluble residues from the solvent blanks. In other words, the epoxy phenolic... 

Low-level interferences are present in ground- and surface water samples. The water-methanol (4 1, v/v) wash in the SPE phase of the sample workup is intended to minimize these interferences while maintaining quantitative recovery of the analytes. A solvent blank may be injected with the samples as part of an analytical set to confirm the cleanliness of a solvent used. 

Initially, this method utilized 5-mL conical centrifuge tubes as the collection device for final elution of the extract from the Cig tubes. In practice, these tubes were found to be very difficult to clean and in few instances were the cause of cross-contamination when low-concentration samples were extracted following samples with very high concentrations. Since no commercial graduated tubes were available, disposable culture tubes are used as the receiver. These tubes are individually calibrated before use. A solvent blank sample may be processed through the method from extraction to quantification to determine if contamination from glassware occurs. 

A solvent blank may be injected with the samples as part of an analytical set to confirm the cleanliness of a solvent used. 

Chatterjee et al. [20] quantitatively separated primaquine from amodiquine by a selective precipitation method. A powdered sample containing primaquine and amodiaquine was dissolved in 0.01 N hydrochloric acid 4 N ammonia was added to precipitate amodiaquine. The mixture was filtered and the combined filtrate and washings containing primaquine was diluted with water and 0.1 N hydrochloric acid. The absorbance of this solution was measured at 282 nm versus a solvent blank. 

Solubility of Neomycin Salts(mg/ml, corrected for solvent blank) ... 

The best way to accomplish this is to prepare standards in the usual way—add increasing volumes of a standard analyte solution to a series of volumetric flasks (include zero added)—but also add a volume of the sample solution to each before diluting to the mark with solvent. Thus you would have a series of standards in which the concentration of analyte added would be known, the smallest concentration added being zero. Exactly how much sample solution is used and what concentration added values would be prepared would be dictated by what concentration levels, with additions, would produce a linear standard curve. In any case, a diluted sample matrix is present in each standard and the matrices are matched. A disadvantage is that it is impossible to prepare a blank with a matched matrix. Thus, a pure solvent blank, or other approximation, must be used. 

Inject mobile phase or solvent blank while infusing anaivte into the column eluant at a Row rate of 5 - 10 p.L/miii ami follow path A,... 

Quality Assurance/Quality Control. QA/QC measures included field blanks, solvent blanks, method blanks, matrix spikes, and surrogates. Percent recovery was determined using three surrogate compounds (nitrobenzene-d5, 2-fluorobiphenyl, d-terphenyl-diQ and matrix spikes (naphthalene, pyrene, benzo[ghi]perylene) the recoveries ranged from 80 to 102%. Separate calibration models were built for each of the 16 PAHs using internal standards (naphthalene-dg, phenanthrene-dio, perylene-di2). Validation was performed using a contaminated river sediment (SRM 1944) obtained from NIST (Gaithersburg, MD) accuracy was <20% for each of the 16 analytes. 

Sastry and Aruna described the use of 3-methyl-2-benzothiazolinone hydrazone hydrochloride as a new technique for the spectrophotometric determination of diloxanide furoate and other anthelmentic and antiamoebic agents [29]. Aliquots of sample solutions containing 10-100 pg of drug substance were transferred into a series of 10 mL graduated test tubes, and the volume adjusted to 3 mL with the respective solvent blank. 3-Methyl-2-benzothiazolinone hydrazone hydrochloride and 1 mL of Cr(VI) were added, and the mixture diluted with methanol. The absorbance at 500 nm was measured against a reagent blank. 

Reconstitution solvent blank, which is caused by the residual analyte (or internal standard) from injection of the previous sample. 

Even if a reconstitution solvent blank is normally used to evaluate carryover during validation and sample analysis, it is suggested to use all three types of blank as mentioned earlier for carryover evaluation during the method development. As considered previously (see Section 8.3.2) in the quantitative evaluation of carryover, linearity of detection together with sufficient accuracy and precision below LLOQ should be assumed. This assumption is questionable, and for this reason some bioanalytical laboratories have chosen different criteria to evaluate the carryover. 

Liquid solutions also scatter light by a similar mechanism. In the case of a solution, the scattering may be traced to two sources fluctuations in solvent density and fluctuations in solute concentration. The former are most easily handled empirically by subtracting a solvent blank correction from measurements of the intensity of light scattered from solutions. What we are concerned with in this section, then, is the remaining scattering, which is due to fluctuations in the solute concentration in the solution. 

A volume of solvent V is put into the flask (e.g. methanol). Volume V2 is the volume of reagent necessary to reach the equivalence point of the titration (the solvent blank). 

SAFETY. Only a small amount of solvent is needed. The adsorbed solutes are eluted under gentle column flow conditions. In solvent extraction, larger volumes of solvent are needed and violent agitation is usually necessary. Thus, the fire and toxic hazards are much less for polymer accumulation. This safety feature compliments the decreased analytical costs and the lower solvent blanks associated with the use of smaller amounts of solvent. 

Figure 2. Capillary GC profiles of resin cleanup blanks and after Soxhlet extraction and sample elution quality control blanks. Y-axis 1 E-2 to 1 E2 = 0.6 to 600 ng/L. Resin blanks solvent blank (bottle blank) XAD-2 cleanup 900 mL of etherZ700 mL of resin XAD-8 cleanup 900 mL of ether/700 mL of resin fourth elution solvent 100-mL elutions after 150 mL, 2 X 100-mL elution with...

Because washing, drying, and filling the cell takes time, it is advisable to work with two cells alternately (both with solvent blanks properly determined) when processing a number of samples. 

A good test for the absence of artifacts that can arise at higher absorbances is to run a blank with a non-optically active molecule, such as 3-methylindole or a DL-amino acid, at the same absorbance as the test samples. The scan should be indistinguishable from the solvent blank. 

Zero spectrophotometer with a solvent blank (i.e., 2,2,4-trimethylpentane) using a quartz cuvette. 

Transfer an aliquot of the clear leaf extract (supernatant) with a pipet to a 1-cm-path-length cuvette and take absorbance readings against a solvent blank in a UV-VIS spectrophotometer at five wavelengths ... 

Figure 6.23 The arrangement of standards, samples, and solvent blanks for a CARRS assay using one 96-well plate for a batch of six compounds. (Reprinted with permission from Korfmacher et al., 2001. Copyright 2001 John Wiley Sons.)...

Solvent/Reagent Blank. A solvent blank checks solvents and reagents that are used during sample preparation and analysis. Sometimes, a blank correction or zero setting is done based on the reagent measurement. For example, in atomic or molecular spectroscopy, the solvents and reagents used in sample preparation are used to provide the zero setting. 

Absorption spectra of 2-nitroanisole in supercritical C02, N20, Freon-13, ammonia and C02-methanol mixtures were obtained on a Cary model 1605 spectrophotometer operated in the dual beam mode. The gases used as supercritical solvents were of the highest purity available from the supplier (Matheson) and were further filtered prior to use. The mixed solvent system of C02-methanol was obtained from Scott Speciality Gases (15.4 wt% methanol), and other mixtures were made in the laboratory. Spectra of 2-nitroanisole in n-pentane, methanol, tetrahydrofuran and acetonitrile (Burdick A Jackson) were obtained using quartz cells with a 1-cm light path and with a pure solvent blank in the reference beam. Vapor phase and supercritical fluid spectra were obtained using an air reference. 

Figure 4. Data acquisition with the Video Fluorometer. (A) Single frame EEM for 1 X 10" M perylene using 64 X 64 format (B) EEM for same sample after summation of 512 frames to memory (C) As in B hut with subtraction of 512 dark frames (D) As in C but with subtraction of solvent blank.

According to the recommended operating procedure for the analysis of CWC-related chemicals by GC (24), the solvent blank, sensitivity, and column performance tests should be carried out to check... 

A solvent blank is used to eliminate the possibility of contamination arising from outside the sample, for example, from the syringe or from the instrument. It is recommended to use the sample solvent as solvent blank and run this test at the beginning and at the end of each sample series and whenever contamination is suspected. The memory effect is possible, for example, in the analysis of alkyl phosphonic acids. If the derivatization of these chemicals has not been complete, the nonderivatized acids are adsorbed on the injector liner. A silylation reagent may in such case react in situ with the adsorbed acids in the liner yielding false positive results. 

Ah the solvents used must be checked before the analysis, and during the analyses relevant solvent blanks must be used to test the cleanness of the system. When analyzing derivatized samples, it is not enough to use just the solvent, but the deriva-tizing chemicals should also be added to the solvent to ensure that there are no derivatizable chemicals in the system before the actual analysis. 

Adjust the instrumental parameters of wavelength, spectral band pass and lamp current in accordance with the manufacturer s recommended conditions. The flame conditions should be established while aspirating a solvent blank. It is recommended that a fuel lean nitrous oxide—acetylene flame be... 

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