RU2510020C1 - Method of determining aluminium (iii) - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention describes a method of determining aluminium (III), which involves preparing a sorbent, an aluminium (III) solution, extracting aluminium (III) from the solution using the sorbent and conversion thereof into a complex on the surface of the sorbent, separating the sorbent from the solution, measuring luminescent intensity of the surface aluminium (III) complex and determining content of aluminium from a calibration curve. The sorbent used is silica gel which is successively modified with polyhexamethylene guanidine and 7-iodo-8-hydroxyquinoline-5-sulphonic acid, and luminescent intensity is measured at 495 nm.

EFFECT: low threshold of detecting aluminium, wider range of determined content, low consumption of the organic complexing agent.

4 ex, 2 tbl

Description

The invention relates to analytical chemistry of elements, in particular to methods for the determination of aluminum (III), and can be used in its determination in natural and industrial waters.

Molecular spectroscopic methods of analysis (spectrophotometry and luminescence) are widely used to determine aluminum in natural and man-made waters, which are characterized by high sensitivity and selectivity, ease of determination and do not require expensive equipment.

One of the widely used techniques to reduce the detection limits of molecular spectroscopic methods is the combination of preliminary sorption of elements by sorbents of various nature and their subsequent determination directly in the sorbent phase.

For sorption-molecular-spectroscopic (sorption-photometric or sorption-luminescent) determination of aluminum, it is necessary that aluminum (III) complexes with sorbent functional groups having their own color or luminescence form on the surface of the sorbent, and the color intensity changes in proportion to the change in zinc concentration by surface of the sorbent.

A known method for the determination of aluminum (III) in the form of a luminescent complex compound on the surface of the sorbent is silica gel modified with C-18 groups [J.F. Garcia Reyes. Development of a solid surface fluorescence-based sensing system for aluminum monitioring in drinking water / J.F. Garcia Reyes, P. Ortega Ban-ales, A. Molina Diaz // Talanta. - 2005. - V.65. - P.1203-1208 (analogue)].

The method involves the following operations:

- silica gel with C-18 groups fixed on its surface is introduced into the flow cell;

- a solution of aluminum (III) with a content of 10-500 μg / l and a solution of chromotropic acid with a content of 10 mg / l are introduced into parallel flows of 0.04 M formate buffer mixture, which are then mixed;

- the total stream containing a complex compound of aluminum (III) with chromotropic acid is passed through a flow cell filled with silica gel with C-18 groups fixed on its surface;

- when passing through a flow cell a solution of a complex compound of aluminum (III) with chromotropic acid, the latter is concentrated on the surface of the sorbent;

- the luminescence intensity of the surface complex compound of aluminum (III) is recorded at 390 nm;

- the content of aluminum (III) is determined by the calibration graph built in similar conditions;

- the detection limit is 2.6 μg / l, the range of detected contents is 10-500 μg / l.

The disadvantages of this method include the complexity of the hardware design, the duration of the procedure for determining the content of aluminum (III), a relatively high detection limit, a narrow range of determined contents.

Closest to the proposed method in technical essence and the achieved results is a method for determining aluminum (III) using a sorbent - silica gel, sequentially modified with polyhexamethylene guanidine and 8-hydroxyquinoline-5-sulfonic acid [US Pat. RF 2374641, IPC G01N 31/22, G01N 21/76. Method for determination of aluminum (III) [Text] / Losev V.N., Yelsufev E.V., Metelitsa S.I., Volkova G.V., Trofimchuk A.K .; Applicant and patent holder of FSAEI HPE Siberian Federal University. - No.2008140257 / 04; declared 10/09/2008; publ. 11/27/2009, Bull. No. 33. - 5 sec. (prototype)].

The method involves the following operations:

- 10 ml of silica gel is added with 100 ml of a 1% solution of polyhexamethylene guanidine, stirred for 5 minutes, the silica gel is separated from the solution by decantation, washed with distilled water and treated with a 0.02% solution of a complexing reagent - 8-hydroxyquinoline-5-sulfonic acid;

- in the analyzed solution with a pH of 4-5, containing aluminum (III), add 0.1 g of sorbent, intensively mixed for 10 minutes;

- the sorbent is separated from the solution by decantation, transferred to a cuvette and the luminescence intensity is measured at 480 nm;

- the content of aluminum (III) is determined by the calibration graph built in similar conditions;

- the detection limit of aluminum (III) when using a weighed portion of the sorbent of 0.1 g is 0.02 μg, the relative detection limit when using 10 ml of solution is 0.002 μg / ml, the range of the determined contents is 0.08-2 μg of aluminum (III) per 0.1 g of sorbent.

The disadvantages of this method include a relatively high detection limit, a narrow range of detectable contents, increased consumption of complexing reagent upon receipt of the sorbent.

The technical result of the invention is to reduce the detection limit (2 times), expand the range of the calibration graph (4 times), reduce the consumption of complexing reagent upon receipt of the sorbent.

The specified technical result is achieved by the fact that in the method for determining aluminum (III), which includes preparing the sorbent by sequentially modifying silica gel with aqueous solutions of polyhexamethylene guanidine and an 8-hydroxyquinoline derivative, obtaining a luminescent surface complex compound of aluminum (III) with an organic reagent, measuring the intensity of the obtained surface complex compound aluminum (III) and determination of the aluminum (III) content according to the calibration graph, new is that as the complexing reagent is organic derivative of 8-hydroxyquinoline - 7-iodo-8-hydroxyquinoline-5-sulfonic acid.

The essence of the proposed method lies in the fact that the aluminum (III) in solution at a pH of 4-6 is quantitatively (the degree of extraction is more than 99%) is extracted with silica gel, sequentially modified with polyhexamethylene guanidine and 7-iodine-8-hydroxyquinoline-5-sulfonic acid, over time establishing sorption equilibrium, not exceeding 10 minutes.

During sorption, aluminum (III) complex compounds with 7-iodine-8-hydroxyquinoline-5-sulfonic acid are formed on the surface of the sorbent, which exhibit intense luminescence at room temperature when they are irradiated with ultraviolet light.

The method is implemented as follows.

To 10 g of silica gel add 100 ml of a 1% solution of polyhexamethylene guanidine, mix for 5 minutes, the silica gel is separated from the solution by decantation, washed with distilled water and treated with a 0.001-0.0001% solution of a complexing reagent - 7-iodine-8-hydroxyquinoline -5-sulfonic acid;

- in the analyzed solution with a pH of 4-6, containing aluminum (III), add 0.1 g of sorbent, mix intensively for 10 minutes;

- the sorbent is separated from the solution by decantation, transferred to a cuvette and the luminescence intensity is measured at 495 nm;

- the content of aluminum (III) is determined by the calibration graph built in similar conditions;

- the detection limit of aluminum (III) when using a sorbent sample of 0.1 g is 0.01 μg, the relative detection limit when using 10 ml of solution is 0.001 μg / ml, the range of the determined contents is 0.05-5 μg of aluminum (III) per 0.1 g of sorbent.

The detection limit of aluminum (III) with a weighed sorbent of 0.1 g is 0.01 μg. This amount of aluminum (III) per 0.1 g of sorbent is the minimum concentration that can be fixed on existing devices relative to the background signal. The calibration graph is linear in the range of 0.05-5 μg of aluminum (III) per 0.1 g of sorbent. The relative detection limit of aluminum (III) depends on the volume from which sorption was performed. When using 10 ml of the solution, the relative detection limit is 0.001 μg / ml, and at 100 ml, 0.0001 μg / ml.

Increasing or decreasing the pH of the solution relative to the optimal values leads to a decrease in the degree of extraction of zinc (II) and to an increase in the detection limit (table 1). The use of solutions of the organic reagent 7-iodine-8-hydroxyquinoline-5-sulfonic acid with a concentration of more than 0.001% and less than 0.0001% also leads to an increase in the detection limit of aluminum (III) (table 2).

To improve the perception of the advantages of the proposed method for determining aluminum (III), examples of the implementation of the prototype and the proposed method are given.

Example 1 (prototype). To 10 ml of a solution with pH 4 containing 1 μg of aluminum (III), add 0.1 g of a sorbent - silica gel, sequentially modified with polyhexamethylene guanide and 8-hydroxyquinoline-5-sulfonic acid, intensively stirred for 10 minutes, the sorbent is separated from the solution by decantation, transferred to a cuvette and measure the luminescence intensity at 480 nm. The amount of aluminum (III) is found by the calibration curve. Found 9.8 ± 0.3 mcg.

Example 2 (the proposed method). To 10 ml of a solution with pH 4.5 containing 0.05 μg aluminum (III), add 0.1 g of a sorbent - silica gel, sequentially modified with polyhexamethylene guanide and 7-iodine-8-hydroxyquinoline-5-sulfonic acid, intensively mixed for 10 minutes, the sorbent is separated from the solution by decantation, transferred to a cuvette and the luminescence intensity is measured at 495 nm. The amount of aluminum (III) is found by the calibration curve. Found 0.051 ± 0.003 μg.

Example 3 (the proposed method). To 10 ml of a solution with a pH of 4.5 containing 2 μg of aluminum (III), add 0.1 g of a sorbent - silica gel, sequentially modified with polyhexamethylene guanide and 7-iodine-8-hydroxyquinoline-5-sulfonic acid, intensively stirred for 10 minutes, the sorbent is separated from the solution by decantation, transferred to a cuvette and the luminescence intensity is measured at 495 nm. The amount of aluminum (III) is found by the calibration curve. Found 1.9 ± 0.1 mcg.

Example 4 (the proposed method). 100 ml of a solution with pH 4.5 containing 5 μg of aluminum (III) is passed through a chromatographic column filled with 0.1 g of a sorbent - silica gel, sequentially modified with polyhexamethylene guanide and 7-iodine-8-hydroxyquinoline-5-sulfonic acid, at a rate of 5 ml / min; the sorbent is removed from the column, transferred to a cuvette and the luminescence intensity is measured at 495 nm. The amount of aluminum (III) is found by the calibration curve. Found 4.9 ± 0.3 mcg.

The method is characterized by high sensitivity, ease of operation, does not require the use of substances harmful to human health. The use of silica gel, sequentially modified with polyhexamethylene guanide and 7-iodine-8-hydroxyquinoline-5-sulfonic acid, allows to reduce the detection limit by 2 times and to expand the range of detectable contents by 4 times compared to the prototype, and the use of organic reagent solutions is smaller (in comparison with the prototype ) concentrations - reduce the cost of the analysis.

Table 1 The influence of the pH of the solution on the detection limit of aluminum (III) Terms of Definition pH 3 four 5 6 8 The detection limit of aluminum (III), μg / 0.1 g of sorbent 0,03 0.01 0.01 0.02 0,03

table 2 The effect of the concentration of a solution of 7-iodine-8-hydroxyquinolin-5-sulfonic acid (R) on the detection limit of aluminum (III) Terms of Definition C _R , 10 ^-3 wt.% 0.01 0.1 0.5 one 5 10 The detection limit of aluminum (III), μg / 0.1 g of sorbent 0.02 0.01 0.01 0.01 0.02 0.05

Claims (1)

A method for determining aluminum (III), including the preparation of a sorbent based on silica gel, sequentially modified with polyhexamethylene guanidine and a complexing organic reagent - a derivative of 8-hydroxyquinoline, preparing a solution of aluminum (III) with a pH of 4-5, extracting aluminum (III) from the solution with a sorbent and transferring it into a complex compound luminescent at room temperature on the surface of the sorbent, separating the sorbent from the solution, measuring the luminescence intensity of the aluminum (III) surface complex and determining the aluminum content according to the calibration schedule, characterized in that 7-iodo-8-hydroxyquinoline-5-sulfonic acid is used as the complexing derivative of 8-hydroxyquinoline, and the luminescence intensity is measured at a wavelength of λ = 495 nm.