Dryness internal

Once the internal standard has been added to the unknown matrix and is thoroughly mixed, the solution can be concentrated, if necessary, for GCl MS analysis. Chemical derivatization is also performed if needed. Normally, samples and reference standards are evaporated to dryness and then redissolved in a carefully measured quantity of solvent. For trace samples, se-... 

In addition to meeting the foregoing requirements, a good internal standard will be easy to add uniformly and precisely, and (preferably) no appreciable amount of the element St (free or combined) will be present in the sample before the addition. Cope29 provides an excellent illustration of these points. He found that yttrium nitrate dissolved in ethyl alcohol could be added to a powdered uranium mineral in a mortar, whereupon grinding immediately to dryness dispersed the internal standard (yttrium) so uniformly that uranium could be satisfactorily determined in certain minerals. But the mineral euxenite is an exception, for it contains both yttrium and uranium, and this complicates the uranium determination with yttrium as internal standard. 

Soil samples are extracted with buffered acetonitrile with a mechanical shaker. Alter centrifuging, aliquots of the extracts are amended with isotopically labeled internal standards and evaporated to dryness. The samples are reconstituted and analyzed by LC/MS/MS. This method determines soil residues of flucarbazone-sodium, sulfonic acid, sulfonamide and NODT with an LOQ of 0.001 mg kg for each analyte. 

Heat and reflux a 5-g portion of soil sample with 50 mL of methanol-phosphate buffer (pH 7)-water (15 7 28, v/v/v) solvent mixture in a round-bottom flask for 1 h. After cooling, transfer a 10-mL portion of the supernatant to a test-tube and mix with 11 mL of 0.02M H3PO4 solution. Load this solution on to a silica-based SPE cartridge (Analytichem International Clin-Elut 1020) at a flow rate of 1-2 drops per second. Discard this fraction. Elute the analytes with 30 mL of dichloromethane. Concentrate the eluate to dryness with air in a water-bath at a temperature of 40 °C (do not use vacuum). Dissolve the residues in 5mL of HPLC injection solution [900 mL of water - - 50 mL of phosphate buffer (pH 7) 4-50 mL of ACN 4-4 g of TBABr]. Pinal analysis is performed using liquid chromatography/ultraviolet detection (LC/UV) with a three-column switching system. 

Macerated plant material is homogenized with a mixture of methanol and 1.2N hydrochloric acid (HCl) in water (4 1, v/v) and then with methanol. An internal standard solution is added to the filtrate and the filtrate is adjusted to a constant volume. A portion of the filtrate is rotary evaporated to dryness and hexane is added to the extract before a Florisil cleanup procedure is performed. The extract is dissolved in toluene for analysis by GC/MS in the negative chemical ionization (NCI) mode. 

Theobromine was determined by GC in various foods (bitter chocolate, milk chocolate, chocolate cake, cocoa powder, chocolate milk), and results are given in graphs and tables.27 Homogenized samples were boiled in alkaline aqueous media, then fat was extracted with n-hexane. The aqueous layer was acidified with diluted HC1 and NaCl was added. Theobromine was extracted from this treated aqueous solution with dichloromethane and the extract was evaporated to dryness. The residue was redissolved in dichloromethane containing an internal standard. GC analysis was performed on a column packed with 1% cyclohexane dimethanol succinate on Gaschrom Q, with FID. Average recoveries were 99 to 101%, coefficient of variation was less than 3% and the limit of detection for theobromine in foods was about 0.005%. 

Standard preparation Dissolve an accurately weighed quantity of USP Miconazole Nitrate RS in methanol to obtain a solution having a known concentration of about 500 pg/mL. Transfer 10 mL of this solution to a test tube, and evaporate on a steam bath with the aid of a current of filtered air to dryness. Dissolve the residue in 2 mL of the Internal standard solution. This Standard preparation has a concentration of about 2500 pg/mL. 

Szathmary and Luhmann [50] described a sensitive and automated gas chromatographic method for the determination of miconazole in plasma samples. Plasma was mixed with internal standard l-[2,4-dichloro-2-(2,3,4-trichlorobenzyloxy) phenethyl]imidazole and 0.1 M sodium hydroxide and extracted with heptane-isoamyl alcohol (197 3) and the drug was back-extracted with 0.05 M sulfuric acid. The aqueous phase was adjusted to pH 10 and extracted with an identical organic phase, which was evaporated to dryness. The residue was dissolved in isopropanol and subjected to gas chromatography on a column (12 m x 0.2 mm) of OV-1 (0.1 pm) at 265 °C, with nitrogen phosphorous detection. Recovery of miconazole was 85% and the calibration graph was rectilinear for 0.25 250 ng/mL. 

Internal standards were flurazepam for clozapine and pericaizine for desmethylclozapine, respectively. Aliquots (0.5 mL) of standards, controls, and patient samples were mixed with 50 /tL of 10mM flurazepam and 50 /tL of 10nM pericaizine, extracted with 4 mL of hexane/n-butanol/ace-tonitrile (93 5 2), shaken for 5 min, and centrifuged at 3000 rpm for 5 min. The organic layer was collected, evaporated to dryness at 40°C under an air stream, reconstituted in 50 /tL of methanol,... 

The sample is extracted with a mixture of hexane, acetone and water. After separation, the hexane phase is reduced in volume and divided into two aliquots, one of which is first shaken with 7% fuming sulphuric acid to remove lipids, and then with cyanide to eliminate interference by elemental sulphur. The other aliquot is evaporated to dryness and heated with ethanolic potassium hydroxide. The two aliquots are injected into a gas chromatograph fitted with a glass capillary column and an electron capture detector. Hexabromobenzene is used as an internal standard. Polychlorinated biphenyls are determined quantitatively by comparing the peaks of the sample with those of Clophen A... 

Addition of internal standard and sodium bicarbonate followed by extraction with diethyl ether evaporation to dryness and redissolution in toluene. 

Determination of Pb(II) and organolead compounds in human urine, after LLE of the complexes with 91 and derivatization Et4Pb as internal standard . The aqueous solution is evaporated to dryness, the sohd residue is derivatized and the alkylated Pb was evaporated into an ETAAS instrument the LOD (SNR 2) was 7 ppb . 

Bai Shao Yao is bitter, sour and slightly cold. It enters the Liver and Spleen meridians. Its sour and cold property can nourish the Yin directly and generate the substantial part of the blood. It is particularly effective for softening the Liver, thereby relieving cramp of the muscles and tendons. It can also effectively moisten the internal organs and the orifices, so it can treat the symptoms of dryness of skin and eyes caused by Liver-blood deficiency. 

All of these substances can nourish the Yin and moisten dryness. They can be selected as chief in formulas to treat internal wind syndrome due to Yin deficiency. 

Ji Zi Huang is salty and cold. It is considered a substance to nourish the Yin and moisten dryness, thereby extinguishing internal wind. It is also an animal product and is more effective in tonifying the body than herbs. 

Dryness has a contracting and holding nature. It is associated with the Lung and predominates in the autumn. Pathogenic dryness can be divided into external dryness and internal dryness. 

Internal dryness is caused directly by the consumption of body fluids. Some diseases, medicines, herbs or food products can injure the body fluids and cause dryness. Long-term stress and emotional disturbance can also cause consumption of the body fluids. As the Lung, Stomach and Large Intestine are mainly involved, the syndrome of dryness can be respectively divided into dryness in the Upper-, Middle- and Lower-Jiao. 

In clinical practice, external dryness and internal dryness can coexist. 

In the syndrome of internal dryness due to Qi and Yin deficiency of the Lung, symptoms such as dry nasal cavity, dry cough, scanty sputum and thirst may exist. 

For treating internal dryness syndrome Nourish the Yin and fluids of the Lung, Kidney,... 

To treat a syndrome of internal dryness of the Lung, sweet, bitter and cold herbs are selected... 

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