Adding the sample

Arrest the balance again and lower the furnace. The calcium oxalate, which is a white powder, may now be added. This may be done with the crucible on the balance using a micro spatula and a steady hand  

A plate over the furnace entrance is essential or, alternatively, the crucible may be removed and the sample added away from the balance. The exact mass used is not usually critical, so guess work may be used, the exact mass being found when the crucible is back on the balance. If the mass reading is critical, then a separate standard laboratory balance may be used in the normal way to weigh out the sample. Replace the crucible on the balance and raise the furnace. Switch the balance to the released position and leave for the gas flow to be established and the sample to stop swaying. 

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The analyte addition method (AAM) involves adding the sample solution to a standard solution of the determinand, whereas in the analyte subtraction method (ASM) the sample is added to a standard solution of an ion that reacts stoichiometrically with the test substance and is sensed by an ISE. These methods are advantageous for determinations on small samples for which microelectrodes would otherwise have to be used. pH adjustment and masking of interferents in the sample is unnecessary because all these operations can be done beforehand on the standard solution. Furthermore, the analyte subtraction method widens... 

Since no chemically pure dyes (greater than 95 purity) were available, recovery studies were done by reducing and analyzing a liquid sample of the dye along with the spiked filter. These liquid samples were prepared by adding a quantity of dye solution (2-200 yL) equivalent to one-half the amount present on the spiked filter to 1 mL of the reduction buffer solution. To this solution 10 mg of sodium hydrosulfite in 1 mL of the reduction buffer was added. The sample was then analyzed in the same manner as the spiked filter sample. The amount of dye contained in the filter and liquid spiked samples was the same, but concentration did vary. However, volume variations became greater than 9 ... 

Nelson et al. [60] published a method for estrone and estradiol measurement using the dansyl derivatives with analysis by APCI. After adding di-estrone and ck-estradiol to 0.5 ml serum, the steroids are extracted with 6 ml methylene chloride. After drying the solvent, 50 pi of sodium bicarbonate and (100 mmol/1, pH 10.5) 50 pi of dansyl chloride (1 g/1) are added. The samples can be injected after heating at 60 C for 1 min. 

A 20-pl aliquot of blood is added to 100 pi of 5% Celite suspension in saline 2 ml ethyl acetate/acetic acid 4 1 is then added. The sample is mixed for 10 s on a vortex, and centrifuged for 30 s. The supernatant is decanted into another test tube, to which 2 ml of 1.5 M HC1 is added, and again agitated on a vortex for 10 s. An aliquot of the lower HC1 phase is measured in a spectrofluorimeter. 

When adding the sample, a sharp interface should be maintained between the sample and the SDS-PAGE tank buffer. Adding the sample too fast or erratically will lead to swirling and a diffuse loading zone. This will cause a loss of band sharpness. 

Edible oils are easily dissolved in benzene, but if a solid food is to be analyzed, the sample should be well ground first. A portion is accurately weighed, to which a known volume of benzene is added. The sample is mixed, centrifuged, and a 5.0-ml aliquot of this extract is used for the analysis. 

In essence, aqueous titration of surface acidity is an ion-exchange process in which hydrated surface protons are replaced by other hydrated cations (e.g., Na+, NIV") during the course of the titration. The procedure is straightforward. It usually consists of the direct titration of an aqueous suspension of the sample of powdered solid with a dilute base (e.g., sodium hydroxide) to a neutral endpoint. Another commonly used procedure consists of noting the pH of an appropriate salt solution (e.g., ammonium acetate), adding the sample, and measuring the amount of di-... 

Lipid extracts treated with neuraminidase were dried under N2 and incubated at 37° with 50 ul (25 units) V.cholerae neuraminidase. After 16 hr, 1 ml C M (2 1) was added, the samples were incubated... 

If the sample is not digested satisfactorily by nitric acid alone, or by nitric acid followed by HC1, further treatment with sulfuric acid can be done. A 2 1 mixture of sulfuric and nitric acids is added. The sample is evaporated to dense white fumes of SO3. More nitric acid may be added if the solution does not clear. The solution is again heated to SO3 fumes. The solution is then cooled, diluted with water, and heated to dissolve any salts. Then it is filtered, if necessary, diluted to volume, and is ready for analysis. 

The reactions were carried out in 300 ml. stainless steel Whitey reaction vessels heated for 30 minutes in a constant temperature oil bath. The come-up time to reach the oil bath temperature was shortened by preheating for 10 minutes in a 70°C water bath. After heating, the vessels and contents were cooled rapidly to about 5°C. A 100 ml aliquot of each reacted sample was adjusted to pH 10 according to Tressl et al. (6) and extracted four times with 100 ml portions of methylene chloride. The extracts were combined and concentrated to approximately 5 ml. at ambient temperature. One ml of 0.30% v/v cyclohexanone in methylene chloride internal standard was added, the samples were brought to 10.0 ml and were then filtered through 0.5 p Teflon cartridge filters. 

The tips of the test swabs were cut off and placed in labeled plastic vials. One ml of 1M HNO was added, the samples were agitated and allowed to leach for 15 min. A 10 yul aliquot was placed on the tantalum strip and the purge gas flow was started (At alone for Sb and Ar H2 for barium). The atomizer unit was automatically cycled through preset time for drying, ashing and atomization (at 2500°C). Absorbance values were recorded on the chart recorder and results were obtained by comparison with a standard curve prepared for each tantalum strip. 

The NMR experiments were undertaken on 28 mM (in nucleotides) poly(dA-dT) in 10 mM cacodylate buffer, to which 1 M salt solutions were added. The samples contained in addition 1 mM and 10 mM EDTA for the proton and phosphorus NMR studies, respectively. The experimental conditions are indicated in order to emphasize that even in 1 M TMA+ solutions there are Na+ ions associated with poly(dA-dT), the 10 mM buffer and the EDTA solutions. 

The Bragg-Brentano type of diffractometer is composed of an x-ray tube with a metallic anode that supplies x-rays that are scattered from the sample and focused at the slit before hitting the detector. In some cases, a monochromator capable of yielding a monochromatic x-ray beam is added. The sample is rotated, relative to the x-ray at angles from 0° to 90° with the help of a goniometer, where the powdered sample is placed on the sample holder. Electronic equipment is used to amplify and filter signal pulses from the detector. 

Two grams of the product is dissolved in a minimum amount of water at room temperature, and a slight excess ( - 1.75 g.) of ammonium bromide is added. After it has cooled in ice, the bromide salt of the complex is filtered off and recrystallized. To convert to the perchlorate salt, a slight excess (by weight) of silver perchlorate is added to a saturated solution of the bromide salt in ca. 0.3 M perchloric acid at 40°C. (small quantities of perchloric acid only are required). The silver bromide is filtered off, and a third of the volume of ice-cold 72% perchloric acid is added. The sample obtained is recrystallized twice. Anal. Calcd. for [(NHs)sCo(NH2)Co(NH,)6](C104)6-H20 Cl, 21.7 H, 4.15 N, 18.8. Found Cl, 21.2 H, 4.3 N, 18.6. 

The aqueous fraction from the neutral or alkaline liquid-liquid extraction, or another portion of the original sample is prepared for analysis of the sample for lewisite 1 (CAS 541-25-3), lewisite 2 (CAS 40334-69-8), and lewisite oxide (CAS 3088-37-7) (Figure 1, fraction 5). The pH of the sample is adjusted with hydrochloric acid to pH 2, the sample is filtered, and 0.1 ml of a freshly prepared solution containing 3,4-dimercaptotoluene (DMT, CAS 496-74-2) 5 mg ml-1 in acetone is added. The sample vial is shaken vigorously and allowed to stand for 10 min. Then one milliliter of n-hexane is added and the sample is shaken vigorously for 30 s every 10 min for 30 min. The hexane fraction is allowed to separate. The top hexane-water fraction is tiansferred to a new vial and centrifuged. After centrifugation, the hexane fraction is separated, dried, and submitted for analysis. 

Hydrophobicity Measurement. A conventional method (25) of using l-anilinonaphthalene-8-sulfonate (ANS) as a semiquantitative hydrophobic probe was applied. To 8 X 10 5Af ANS in 0.1M Tris-HCl (pH 8.5) was added the sample at a concentration of 0.05% (w/w) and the resulting solution measured for the intensity of its emission spectrum... 

The analytical procedure is as follows. Filter samples (both the glass fiber and the silver membrane) are placed in a screw-cap vial and five ml benzene (or alternative solvent) is added. The sample is extracted ultrasonically for 15 minutes. 

Control of Interferences In the presence of chlorine, add 1 mL of Malonic Acid Reagent to both flasks before adding the samples. Proceed as above, but measure absorbance immediately. 

Ammonium bicarbonate stock (100 mMl was made and stored at 4° C. Stock solutions of all proteins were prepared in 0.1% TFA, 50% acetonitrile solutions and stored at -20°C until use. Aliquots of the stocks, containing 10 to 100 pg of protein, were dried in a centrifugal dryer prior to digestion. To 5 mg of N,N-diethylaminopropyl-bis-(3-hydroxypropyl) phosphine, 1 ml of 50% isopropyl alcohol/50 mM ammonium bicarbonate was added. The samples were then resuspended in 20 pi reagent solution per 10 pg of protein, heated at 80 C for 2 hours, and dried to remove volatile components. 

The resulting solution was diluted with 75 pi of water and endoproteinase Lys-C at 1% by weight was added. The sample was incubated at 37 C for 20 hr before it was quenched with TFA. The peptides generated were separated by chromatography through a Vydac C18 column (0.21 x 5 cm). The solvents and the gradient used were identical to those described above except the flow rate was changed to 0.25 ml per min. 

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