Qualitative Analysis

qualitative analysis

[′kwäl·ə‚tād·iv ə‚nal·ə·səs] (analytical chemistry) The analysis of a gas, liquid, or solid sample or mixture to identify the elements, radicals, or compounds composing the sample.

Qualitative Analysis

the set of chemical, physicochemical, and physical methods used to discover and identify the elements, radicals, ions, and compounds in a substance or mixture of substances under analysis.

Qualitative analysis forms one of the basic divisions of analytical chemistry. The most important features of qualitative analysis techniques are (1) specificity (selectivity), that is, the possibility of discovering an unknown element in the presence of another, and (2) sensitivity, determined by the smallest quantity of an element that can be found in a drop of solution (0.01–0.03 milliliter) by the given method; a sensitivity of 1 μg has been attained by modern techniques.

Classical qualitative analysis of inorganic substances is carried out by either the “dry” method or by the “wet” method. The dry method involves testing for flame coloration with a gas burner and the formation of colored beads (vitreous fusions) when heating the powder from the substance tested (usually a salt or metal oxide) with a small quantity of sodium tetraborate or phosphoric salt (NaNH₄HPO₄·4H₂O). Wet analysis (in solutions) is effected by macro-, semimicro-, micro-, and ultra-microtechniques. In macroanalysis the quantity of analyzed substance is greater than 100 mg and the volume of solution is greater than 5 ml; in ultramicroanalysis the measurements are less than 0.1 mg and less than 0.05 ml, respectively.

Since the qualitative analysis of inorganic compounds in aqueous solutions is based on ionic reactions, it is divided into the analysis of cations and the analysis of anions. Cations are generally separated into five groups according to the solubility of their sulfur salts. Anions are most often grouped according to the different solubilities of their barium or silver salts. If the analyzed substance is found to contain ions that can be determined by selective reagents, then analysis is carried out using the fractional method.

Along with the classical chemical methods, physical and physicochemical (that is, instrumental) techniques are widely used in qualitative analysis that are based on the study of the optical, electric, magnetic, thermal, catalytic, adsorptive, and other properties of the analyzed substances. These methods have a number of advantages over the chemical techniques, since in many cases they make it possible both to eliminate the preliminary chemical separation of the analyzed sample into its component parts and to record the results of the analysis continuously and automatically. Furthermore, a considerably smaller quantity of analyzed sample is required when using physical and physicochemical methods to determine small amounts of admixtures. These methods include spectral analysis, luminescent analysis, mass spectroscopy, polarography, chromatography, activation analysis, and kinetic analysis. The qualitative analysis of organic compounds is conducted by element analysis and functional analysis and by determining the basic physicochemical properties of the analyzed substances.

V. V. KRASNOSHCHEKOV

qualitative analysis

analysis

[ah-nal´ĭ-sis] (pl. anal´yses) separation into component parts.psychoanalysis. adj., adj analyt´ic.activity analysis the breaking down of an activity into its smallest components for the purpose of assessment.bivariate analysis statistical procedures that involve the comparison of summary values from two groups on the same variable or of two variables within a group.blood gas analysis see blood gas analysis.chromosome analysis see chromosome.concept analysis examination of the attributes of a concept as it occurs in ordinary usage in order to identify the meanings attached to the concept.content analysis a systematic procedure for the quantification and objective examination of qualitative data, such as written or oral messages, by the classification and evaluation of terms, themes, or ideas; for example, the measurement of frequency, order, or intensity of occurrence of the words, phrases, or sentences in a communication in order to determine their meaning or effect.correlational analysis a statistical procedure to determine the direction of a relationship (positive or negative correlation) between two variables and the strength of the relationship (ranging from perfect correlation through no correlation to perfect inverse correlation and expressed by the absolute value of the correlation coefficient).analysis of covariance (ANCOVA) a variation of analysis of variance that adjusts for confounding by continuous variables.data analysis the reduction and organization of a body of data to produce results that can be interpreted by the researcher; a variety of quantitative and qualitative methods may be used, depending upon the nature of the data to be analyzed and the design of the study.ego analysis in psychoanalytic treatment, the analysis of the strengths and weaknesses of the ego, especially its defense mechanisms against unacceptable unconscious impulses.gait analysis see gait analysis.gastric analysis see gastric analysis.multiple-locus variable number of tandem repeat analysis (MLVA) a laboratory tool designed to recognize repeats" >tandem repeats and other qualities in the genome of an individual to provide a high resolution fingerprint" >DNA fingerprint for the purpose of identification.multivariate analysis statistical techniques used to examine more than two variables at the same time.power analysis a statistical procedure that is used to determine the number of required subjects in a study in order to show a significant difference at a predetermined level of significance and size of effect; it is also used to determine the power of a test from the sample size, size of effect, and level of significance in order to determine the risk of error" >Type II error when the hypothesis" >null hypothesis is accepted.qualitative analysis the determination of the nature of the constituents of a compound or a mixture of compounds.quantitative analysis determination of the proportionate quantities of the constituents of a compound or mixture.SNP analysis analysis of polymorphisms" >single nucleotide polymorphisms to assess artificially produced genetic modifications or identify different strains of an organism.transactional analysis a type of psychotherapy based on an understanding of the interactions (transactions) between patient and therapist and between patient and others in the environment; see also transactional analysis.analysis of variance ANOVA; a statistical test used to examine differences among two or more groups by comparing the variability between the groups with the variability within the groups.variance analysis the identification of patient or family needs that are not anticipated and the actions related to these needs in a system of care" >managed care. There are four kinds of origin for the variance: patient-family origin, system-institutional origin, community origin, and clinician origin.vector analysis analysis of a moving force to determine both its magnitude and its direction, e.g., analysis of the scalar electrocardiogram to determine the magnitude and direction of the electromotive force for one complete cycle of the heart.