Multivariate optimization of microwave digestion for determining of some elements in baobab (<i>A. digitata </i>L.) fruit pulp by ICP-MS

Abstract

A method of measuring a plurality of chemical elements in a baobab fruit pulp can include crushing and homogenizing baobab fruit pulp; sieving the homogenized baobab fruit pulp to obtain baobab fruit fine powder; adding the baobab fruit fine powder to each of prepared plurality of acid mixtures to obtain a plurality of solutions; heating each of the plurality of solutions to digest the baobab fruit fine powder in each of the plurality of solutions; cooling the plurality of solutions; filtering the digested baobab fruit fine powder from each of the plurality of solutions to obtain a plurality of filtered digested baobab fruit fine powders; diluting each of the plurality of filtered digested baobab fruit fine powders with water to obtain a plurality of mixtures; and measuring the plurality of chemical elements in each of the plurality of mixtures using inductively coupled plasma mass spectrometry (ICP-MS).

Claims

1. A method of measuring a plurality of chemical elements in a baobab fruit pulp, the method comprising: obtaining pulp from a baobab fruit; crushing and homogenizing the baobab fruit pulp to obtain a homogenized baobab fruit pulp; sieving the homogenized baobab fruit pulp to obtain baobab fruit fine powder; preparing a plurality of acid mixtures, wherein the plurality of acid mixtures comprise acid mixtures that consist of only nitric acid and acid mixtures that consist of nitric acid and one or more of water and hydrogen peroxide; adding the baobab fruit fine powder to each of the prepared plurality of acid mixtures to obtain a plurality of solutions; heating each of the plurality of solutions in an oven cavity of a microwave to digest the baobab fruit fine powder in each of the plurality of solutions to obtain a digested baobab fruit fine powder in each of the plurality of solutions; cooling the plurality of solutions; filtering the digested baobab fruit fine powder from each of the plurality of solutions to obtain a plurality of filtered digested baobab fruit fine powders; diluting each of the plurality of filtered digested baobab fruit fine powders with water to obtain a plurality of mixtures; and measuring the plurality of chemical elements in each of the plurality of mixtures to obtain an optimized mixture for digestion of baobab fruit fine powder using inductively coupled plasma mass spectrometry (ICP-MS), wherein the plurality of chemical elements are selected from the group consisting of sodium, magnesium, aluminum, potassium, calcium, vanadium, chromium, manganese, cobalt, copper, selenium, barium, and combinations thereof.

2. The method of claim 1, wherein the homogenized baobab fruit pulp is prepared by crushing and homogenizing the baobab fruit pulp with an agate mortar and pestle.

3. The method of claim 1, wherein the plurality of acid mixtures are comprised of 12 acid mixtures comprising: a) about 3 mL of nitric acid (HNO.sub.3), b) about 5 mL of HNO.sub.3, c) about 7 mL of HNO.sub.3, d) about 7 mL of HNO.sub.3:water (H.sub.2O) (1:3), e) about 7 mL of HNO.sub.3:H.sub.2O (1:1), f) about 7 mL of HNO.sub.3:H.sub.2O (3:1), g) about 7 mL of HNO.sub.3:H.sub.2O (1:1):about 2 mL of hydrogen peroxide (H.sub.2O.sub.2), h) about 7 mL of HNO.sub.3:H.sub.2O (1:1):about 4 mL of H.sub.2O.sub.2, i) about 7 mL of HNO.sub.3:H.sub.2O (1:1):about 6 mL of H.sub.2O.sub.2, j) about 3 mL of HNO.sub.3:about 4 mL of H.sub.2O.sub.2, k) about 5 mL of HNO.sub.3:about 4 mL of H.sub.2O.sub.2, and l) about 7 mL of HNO.sub.3:about 4 mL of H.sub.2O.sub.2.

4. The method of claim 3, wherein the plurality of solutions are prepared by adding about 0.4 g of the baobab fruit fine powder to each of the prepared plurality of acid mixtures within a plurality of vessels.

5. The method of claim 4, wherein the digested baobab fruit fine powder in each of the plurality of solutions within each of the plurality of vessels are prepared by sealing each of the plurality of vessels and heating the plurality of solutions to digest the baobab fruit fine powder in each of the plurality of solutions within each of the sealed plurality of vessels in the oven cavity of the microwave at about 100? C. for about 5 minutes, then at about 130? C. for about 15 minutes, and thereafter cooling each of the plurality of solutions within each of the sealed plurality of vessels.

6. A method of optimizing microwave digestion, the method comprising: normalizing the measured plurality of chemical elements in each of the plurality of mixtures of claim 1 to obtain a plurality of normalized measured chemical elements values; generating a plurality of run data by incorporating the plurality of normalized measured chemical elements values and microwave digestion factor variables into a response surface methodology using a Box-Behnken design to obtain multiple response (MR) values and concentration values for each of the plurality of normalized measured chemical elements; determining which run data generated a highest multiple response value and highest concentration values for each of the plurality of normalized measured chemical elements; and detecting which of the plurality of acid mixtures of claim 1 correspond with the determined run data to obtain optimized microwave digestion, wherein each of the plurality of normalized measured chemical elements values are prepared by dividing concentration values measured for each of the measured plurality of chemical elements in each of the plurality of mixtures by a highest concentration of the same chemical element measured for each of the measured plurality of chemical elements in each of the plurality of mixtures, and wherein the multiple response values and concentration values for each of the plurality of normalized measured chemical elements are prepared by generating a plurality of run data by incorporating the plurality of normalized measured chemical elements values and microwave digestion factor variables into the response surface methodology using the Box-Behnken design comprising about 27 factorial experiments with about 3 center points.

7. The method of claim 6, wherein the microwave digestion factor variables comprise a microwave temperature of about 125? C., an acid mixture volume of about 10 mL, a sample weight of about 0.1 g, and a radiation time of about 15 minutes.

8. A method of performing microwave digestion, the method comprising: normalizing the measured plurality of chemical elements in each of the plurality of mixtures of claim 1 to obtain a plurality of normalized measured chemical elements values; generating a plurality of run data by incorporating the plurality of normalized measured chemical elements values and microwave digestion factor variables into a response surface methodology using a to obtain multiple response (MR) values and concentration values for the plurality of normalized measured chemical elements; determining which run data generated a highest multiple response value and highest concentration values for each of the plurality of normalized measured chemical elements; and detecting which of the plurality of acid mixtures of claim 1 correspond with the determined run data to obtain optimized microwave digestion; wherein the multiple response values and concentration values for the plurality of normalized measured chemical elements are prepared by generating a plurality of run data by incorporating the plurality of normalized measured chemical elements values and microwave digestion factor variables into the response surface methodology using the Box-Behnken design comprising about 27 factorial experiments with about 3 center points, and wherein the microwave digestion factor variables comprise a microwave temperature of about 125? C., an acid mixture volume of about 10 ml, a sample weight of about 0.1 g, and a radiation time of about 15 minutes; the method further comprising: obtaining pulp from a baobab fruit; crushing and homogenizing the baobab fruit pulp to obtain a homogenized baobab fruit pulp; sieving the homogenized baobab fruit pulp to obtain baobab fruit fine powder; preparing the detected acid mixture; adding the baobab fruit fine powder to the detected acid mixture to obtain a solution; heating the solution to digest the baobab fruit fine powder in the solution to obtain a digested baobab fruit fine powder in the solution; cooling the solution; filtering the digested baobab fruit fine powder from the solution to obtain a filtered digested baobab fruit fine powder; diluting the filtered digested baobab fruit fine powder with water to obtain a mixture; and measuring the mixture using inductively coupled plasma mass spectrometry (ICP-MS).

9. The method of claim 8, wherein the detected acid mixture comprises about 7 mL of HNO.sub.3:H.sub.2O (1:1):about 2 mL of hydrogen peroxide (H.sub.2O.sub.2).

10. The method of claim 9, wherein the solution is prepared by adding about 0.1 g of the baobab fruit fine powder to the prepared detected acid mixture within a vessel.

11. The method of claim 10, wherein the digested baobab fruit fine powder in the solution within the vessel is prepared by sealing the vessel and heating the solution to digest the baobab fruit fine powder in the solution within the sealed vessel in an oven cavity of a microwave at about 100? C. for about 5 minutes then at about 130? C. for about 15 minutes and thereafter cooling the solution within the sealed vessel.

12. The method of claim 8, wherein the plurality of chemical elements are selected from the group consisting of sodium, magnesium, aluminum, potassium, calcium, vanadium, chromium, manganese, cobalt, copper, selenium, barium, and combinations thereof.

13. The method of claim 8, wherein the water comprises deionized water.

14. The method of claim 8, wherein the plurality of normalized measured chemical elements values are prepared by dividing a chemical element concentration measured for each of the measured plurality of chemical elements in each of the plurality of mixtures by a highest concentration of the same chemical element measured for each of the measured plurality of chemical elements in each of the plurality of mixtures.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 depicts the processes for measuring a plurality of chemical elements in a baobab fruit pulp, optimizing microwave digestion, and performing microwave digestion.

DETAILED DESCRIPTION

(2) The following definitions are provided for the purpose of understanding the present subject matter and for construing the appended patent claims. The definitions are not meant to be limiting to the subject matter described herein.

Definitions

(3) Throughout the application, where systems are described as having, including, or comprising specific components, or where processes are described as having, including, or comprising specific process steps, it is contemplated that compositions of the present teachings can also consist essentially of, or consist of, the recited components, and that the processes of the present teachings can also consist essentially of, or consist of, the recited process steps.

(4) It is noted that, as used in this specification and the appended claims, the singular forms a, an, and the include plural references unless the context clearly dictates otherwise.

(5) In the application, where an element or component is said to be included in and/or selected from a list of recited elements or components, it should be understood that the element or component can be any one of the recited elements or components, or the element or component can be selected from a group consisting of two or more of the recited elements or components. Further, it should be understood that elements and/or features of a system or a method described herein can be combined in a variety of ways without departing from the spirit and scope of the present teachings, whether explicit or implicit herein.

(6) The use of the terms include, includes, including, have, has, or having should be generally understood as open-ended and non-limiting unless specifically stated otherwise.

(7) The use of the singular herein includes the plural (and vice versa) unless specifically stated otherwise. In addition, where the use of the term about is before a quantitative value, the present teachings also include the specific quantitative value itself, unless specifically stated otherwise. As used herein, the term about refers to a ?10% variation from the nominal value unless otherwise indicated or inferred.

(8) The term optional or optionally means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances in which it does not.

(9) Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which the presently described subject matter pertains.

(10) Where a range of values is provided, for example, concentration ranges, percentage ranges, or ratio ranges, it is understood that each intervening value, to the tenth of the unit of the lower limit, unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is encompassed within the described subject matter. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges, and such embodiments are also encompassed within the described subject matter, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the described subject matter.

(11) Throughout the application, descriptions of various embodiments use comprising language. However, it will be understood by one of skill in the art, that in some specific instances, an embodiment can alternatively be described using the language consisting essentially of or consisting of.

(12) For purposes of better understanding the present teachings and in no way limiting the scope of the teachings, unless otherwise indicated, all numbers expressing quantities, percentages or proportions, and other numerical values used in the specification and claims, are to be understood as being modified in all instances by the term about. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained. At the very least, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

(13) The present subject matter relates to a method of measuring a plurality of chemical elements in a baobab fruit pulp. The present subject matter further relates to a method of optimizing microwave digestion, a method of using the optimized microwaved digestion to perform microwave digestion, and a method of determining accuracy of response surface methodology (Box-Behnken design).

(14) FIG. 1 depicts, in one embodiment, a method of measuring a plurality of chemical elements in a baobab fruit pulp which includes obtaining pulp from a baobab fruit in step (100); crushing and homogenizing the baobab fruit pulp to obtain a homogenized baobab fruit pulp in step (105); sieving the homogenized baobab fruit pulp to obtain baobab fruit fine powder (not shown); preparing a plurality of acid mixtures (not shown); adding the baobab fruit fine powder to each of the prepared plurality of acid mixtures to obtain a plurality of solutions (not shown); heating each of the plurality of solutions to digest the baobab fruit fine powder in each of the plurality of solutions to obtain a digested baobab fruit fine powder in each of the plurality of solutions in step (110); cooling the plurality of solutions in step (110); filtering the digested baobab fruit fine powder from each of the plurality of solutions to obtain a plurality of filtered digested baobab fruit fine powders in step (115); diluting each of the plurality of filtered digested baobab fruit fine powders with water to obtain a plurality of mixtures in step (120); and measuring the plurality of chemical elements in each of the plurality of mixtures using inductively coupled plasma mass spectrometry (ICP-MS) in step (125).

(15) In an embodiment, the method can include manually separating pulp from the seed of the baobab fruit. Afterward, the baobab fruit pulp can be crushed and homogenized using an agate mortar and pestle to obtain a homogenized baobab fruit pulp. Then, the homogenized baobab fruit pulp can be placed in a plastic sieve with 1 mm pores to obtain baobab fruit fine powder.

(16) In an embodiment, a plurality of acid mixtures can be prepared. The plurality of acid mixtures can have 12 acid mixtures each respectively can have:a) about 3 mL of nitric acid (HNO.sub.3), b) about 5 mL of HNO.sub.3, c) about 7 mL of HNO.sub.3, d) about 7 mL of HNO.sub.3:water (H.sub.2O) (1:3), e) about 7 mL of HNO.sub.3:H.sub.2O (1:1), f) about 7 mL of HNO.sub.3:H.sub.2O (3:1), g) about 7 mL of HNO.sub.3:H.sub.2O (1:1):about 2 mL of hydrogen peroxide (H.sub.2O.sub.2), h) about 7 mL of HNO.sub.3:H.sub.2O (1:1):about 4 mL of H.sub.2O.sub.2, i) about 7 mL of HNO.sub.3:H.sub.2O (1:1):about 6 mL of H.sub.2O.sub.2, j) about 3 mL of HNO.sub.3:about 4 mL of H.sub.2O.sub.2, k) about 5 mL of HNO.sub.3:about 4 mL of H.sub.2O.sub.2, and 1) about 7 mL of HNO.sub.3:about 4 mL of H.sub.2O.sub.2.

(17) In an embodiment, about 0.4 g of the baobab fruit fine powder can be added to each of the prepared plurality of acid mixtures within a plurality of vessels to obtain a plurality of solutions with the plurality of vessels.

(18) In an embodiment, each of the plurality of vessels can be sealed and the plurality of solutions can be heated to digest the baobab fruit fine powder in each of the plurality of solutions within each of the sealed plurality of vessels in an oven cavity of a microwave digestion at about 100? C. for about 5 minutes, then at about 130? C. for about 15 minutes, and thereafter cooling each of the plurality of solutions within each of the sealed plurality of vessels to obtain a digested baobab fruit fine powder in each of the plurality of solutions within each of the sealed plurality of vessels.

(19) In an embodiment, the digested baobab fruit fine powder can be filtered from each of the plurality of solutions to obtain a plurality of filtered digested baobab fruit fine powders. Afterward, each of the plurality of filtered digested baobab fruit fine powders can be diluted with about 100 mL of deionized water to obtain a plurality of mixtures.

(20) In an embodiment, the plurality of chemical elements in each of the plurality of mixtures can be measured using inductively coupled plasma mass spectrometry (ICP-MS). The plurality of chemical elements can be selected from the group consisting of sodium, magnesium, aluminum, potassium, calcium, vanadium, chromium, manganese, cobalt, copper, selenium, barium, other chemical elements, and combinations thereof.

(21) In a further embodiment, the present subject matter relates to a method of optimizing microwave digestion in step (130) as shown in FIG. 1, the method includes normalizing the measured plurality of chemical elements in each of the plurality of mixtures obtained by the method above to obtain a plurality of normalized measured chemical elements values; generating a plurality of run data by incorporating the plurality of normalized measured chemical elements values and microwave digestion factor variables into a response surface methodology (Box-Behnken design) to obtain multiple response (MR) values and concentration values for each of the plurality of normalized measured chemical elements; determining which run data generated a highest multiple response value and highest concentration values for each of the plurality of normalized measured chemical elements; and detecting which of the plurality of acid mixtures obtained by the method above correspond with the determined run data to obtain optimized microwave digestion.

(22) In one embodiment, the method of optimizing microwave digestion can include normalizing the measured plurality of chemical elements in each of the plurality of mixtures obtained by the method above to obtain a plurality of normalized measured chemical elements values. Each of the plurality of normalized measured chemical elements values can be prepared by dividing the chemical element concentration measured for each of the measured plurality of chemical elements in each of the plurality of mixtures by a highest concentration of the same chemical element measured for each of the measured plurality of chemical elements in each of the plurality of mixtures.

(23) In an embodiment, the plurality of normalized measured chemical elements values and microwave digestion factor variables can be incorporated into a response surface methodology (Box-Behnken design) to generate a plurality of run data to obtain multiple response (MR) values and concentration values for each of the plurality of normalized measured chemical elements. The response surface methodology (Box-Behnken design) can have about 27 factorial experiments with about 3 center points using a Minitab software. The microwave digestion factor variables can have a microwave temperature of about 125? C., an acid mixture volume of about 10 mL, a sample weight of about 0.1 g, and a radiation time of about 15 minutes.

(24) In a further embodiment, the present subject matter relates to a method of performing microwave digestion as shown in FIG. 1, the method includes obtaining pulp from a baobab fruit in step (100); crushing and homogenizing the baobab fruit pulp to obtain a homogenized baobab fruit pulp in step (105); sieving the homogenized baobab fruit pulp to obtain baobab fruit fine powder (not shown); preparing the detected acid mixture obtained by the method above (not shown); adding the baobab fruit fine powder to the detected acid mixture to obtain a solution (not shown); heating the solution to digest the baobab fruit fine powder in the solution to obtain a digested baobab fruit fine powder in the solution in step (110); cooling the solution in step (110); filtering the digested baobab fruit fine powder from the solution to obtain a filtered digested baobab fruit fine powder in step (115); diluting the filtered digested baobab fruit fine powder with water to obtain a mixture in step (120); and measuring the mixture using inductively coupled plasma mass spectrometry (ICP-MS) in step (125).

(25) In one embodiment, the method of performing microwave digestion can include manually separating pulp from the seed of the baobab fruit. Afterward, the baobab fruit pulp can be crushed and homogenized using an agate mortar and pestle to obtain a homogenized baobab fruit pulp. Then, the homogenized baobab fruit pulp can be placed in a plastic sieve with 1 mm pores to obtain baobab fruit fine powder.

(26) In an embodiment, the detected acid mixture obtained by the method above can be prepared. The detected acid mixture can have about 7 mL of HNO.sub.3:H.sub.2O (1:1):about 2 mL of hydrogen peroxide (H.sub.2O.sub.2).

(27) In an embodiment, about 0.1 g of the baobab fruit fine powder can be added to the prepared detected acid mixture within a vessel to obtain a solution with the vessel.

(28) In an embodiment, the vessel can be sealed and the solution can be heated to digest the baobab fruit fine powder in the solution within the sealed vessel in an oven cavity of a microwave digestion at about 100? C. for about 5 minutes, then at about 130? C. for about 15 minutes, and thereafter cooling the solution within the sealed vessel to obtain a digested baobab fruit fine powder in the solution within the sealed vessel.

(29) In an embodiment, the digested baobab fruit fine powder can be filtered from the solution to obtain a filtered digested baobab fruit fine powder. Afterward, the filtered digested baobab fruit fine powder can be diluted with about 100 mL of deionized water to obtain a mixture.

(30) In an embodiment, the plurality of chemical elements in the mixture can be measured using inductively coupled plasma mass spectrometry (ICP-MS). The plurality of chemical elements can be selected from the group consisting of sodium, magnesium, aluminum, potassium, calcium, vanadium, chromium, manganese, cobalt, copper, selenium, barium, other chemical elements, and combinations thereof.

(31) In a further embodiment, the present subject matter relates to a method of determining accuracy of response surface methodology (Box-Behnken design), the method includes obtaining a baobab fruit; preparing an analyte solution; adding the analyte solution at various concentrations to the baobab fruit; and determining recovery rates (R) for each chemical elements in the baobab fruit.

(32) In one embodiment, the method of determining accuracy of response surface methodology (Box-Behnken design) can include obtaining a baobab fruit which can be purchased from a local market and can be used as a home control sample.

(33) In an embodiment, the analyte solution can be selected from the group consisting of barium, sodium, magnesium, aluminum, potassium, calcium, vanadium, chromium, manganese, cobalt, copper, zinc, iron, and selenium, other chemical elements, and combinations thereof.

(34) In an embodiment, the analyte solution can be added at concentrations of about 25 ug/L, about 50 ug/L, and about 100 ug/L to the baobab fruit.

(35) FIG. 1 shows the process for optimizing microwave digestion as described herein.

(36) The following examples illustrate the present teachings.

EXAMPLES

Example 1

(37) Measuring a Plurality of Chemical Elements in a Baobab Fruit Pulp

(38) The process of measuring a plurality of chemical elements in a baobab fruit pulp was conducted using the following steps.

(39) Preparation of pulp: Pulp from a baobab fruit was manually separated from the seed of the baobab fruit.

(40) Homogenization: The baobab fruit pulp was crushed and homogenized using an agate mortar and pestle to obtain a homogenized baobab fruit pulp.

(41) Sieving: The homogenized baobab fruit pulp was placed in a plastic sieve with 1 mm pores to obtain baobab fruit fine powder.

(42) Preparation of acid mixtures: A plurality of acid mixtures were prepared. The plurality of acid mixtures were comprised of 12 acid mixtures each respectively comprising: a) about 3 mL of nitric acid (HNO.sub.3), b) about 5 mL of HNO.sub.3, c) about 7 mL of HNO.sub.3, d) about 7 mL of HNO.sub.3:water (H.sub.2O) (1:3), e) about 7 mL of HNO.sub.3:H.sub.2O (1:1), f) about 7 mL of HNO.sub.3:H.sub.2O (3:1), g) about 7 mL of HNO.sub.3:H.sub.2O (1:1):about 2 mL of hydrogen peroxide (H.sub.2O.sub.2), h) about 7 mL of HNO.sub.3:H.sub.2O (1:1):about 4 mL of H.sub.2O.sub.2, i) about 7 mL of HNO.sub.3:H.sub.2O (1:1):about 6 mL of H.sub.2O.sub.2, j) about 3 mL of HNO.sub.3:about 4 mL of H.sub.2O.sub.2, k) about 5 mL of HNO.sub.3:about 4 mL of H.sub.2O.sub.2, and 1) about 7 mL of HNO.sub.3:about 4 mL of H.sub.2O.sub.2 as shown in Table 1.

(43) Preparation of solutions: About 0.4 g of the baobab fruit fine powder was added to each of the prepared plurality of acid mixtures within a plurality of vessels to obtain a plurality of solutions with the plurality of vessels.

(44) Heating: Each of the plurality of vessels were sealed and the plurality of solutions were heated to digest the baobab fruit fine powder in each of the plurality of solutions within each of the sealed plurality of vessels in an oven cavity of a microwave digestion at about 100? C. for about 5 minutes, then at about 130? C. for about 15 minutes, and thereafter cooling each of the plurality of solutions within each of the sealed plurality of vessels to obtain a digested baobab fruit fine powder in each of the plurality of solutions within each of the sealed plurality of vessels.

(45) Filtering: The digested baobab fruit fine powder was filtered from each of the plurality of solutions to obtain a plurality of filtered digested baobab fruit fine powders.

(46) Preparation of a mixture: Each of the plurality of filtered digested baobab fruit fine powders were diluted with about 100 mL of deionized water to obtain a plurality of mixtures.

(47) ICP-MS: The plurality of chemical elements in each of the plurality of mixtures were measured using inductively coupled plasma mass spectrometry (ICP-MS). The plurality of chemical elements are selected from the group consisting of sodium, magnesium, aluminum, potassium, calcium, vanadium, chromium, manganese, cobalt, copper, selenium, barium, other chemical elements, and combinations thereof.

(48) TABLE-US-00001 TABLE 1 The volume and concentration of the combination of nitric acid and hydrogen peroxide were used. Acid mixture No. HNO.sub.3 ml H.sub.2O.sub.2 ml 1 3 ml conc. 0 ml 2 5 ml conc. 0 ml 3 7 ml conc. 0 ml 4 7 ml HNO.sub.3:H.sub.2O (1:3) 0 ml 5 7 ml HNO.sub.3:H.sub.2O (1:1) 0 ml 6 7 ml HNO.sub.3:H.sub.2O (3:1) 0 ml 7 7 ml HNO.sub.3:H.sub.2O (1:1) 2 ml 8 7 ml HNO.sub.3:H.sub.2O (1:1) 4 ml 9 7 ml HNO.sub.3:H.sub.2O (1:1) 6 ml 10 3 ml conc. 4 ml 11 5 ml conc. 4 ml 12 7 ml conc. 4 ml

Example 2

(49) Optimizing Microwave Digestion

(50) The process of optimizing microwave digestion was conducted using the following steps.

(51) Normalization: The measured plurality of chemical elements in each of the plurality of mixtures as mentioned in Example 1 were normalized to obtain a plurality of normalized measured chemical elements values as shown in Table 2. Normalization was conducted by dividing the chemical element concentration measured for each of the measured plurality of chemical elements in each of the plurality of mixtures by a highest concentration of the same chemical element measured for each of the measured plurality of chemical elements in each of the plurality of mixtures. As shown in Table 2, run No. 7, which corresponds to acid mixture No. 7 as shown in Table 1, generated chemical elements normalization values ranging from about 0.03 to about 1. This indicate that the acid mixture No. 7 has the greatest ability to extract all the chemical elements from the plurality of filtered digested baobab fruit pulp fine powders in comparison to all other acid mixtures shown in Table 1.

(52) Response surface method methodology (Box-Behnken design): The plurality of normalized measured chemical elements values and microwave digestion factor variables were incorporated into a response surface methodology (Box-Behnken design) to generate a plurality of run data to obtain multiple response (MR) values and concentration values for each of the plurality of normalized measured chemical elements as shown in Table 3. The response surface methodology (Box-Behnken design) comprises about 27 factorial experiments with about 3 center points using a Minitab software. The microwave digestion factor variables comprise a microwave temperature of about 125? C., an acid mixture volume of about 10 mL, a sample weight of about 0.1 g, and a radiation time of about 15 minutes.

(53) Determination and detection: Using the run data generated as shown in Table 3, it was determined which run data generated a highest multiple response value and highest concentration values for each of the plurality of normalized measured chemical elements. Afterward, a detection of which of the plurality of acid mixtures of as mentioned in Example 1 correspond with the determined run data was conducted to obtain optimized microwave digestion.

(54) As shown in Table 3, run No. 7 produced the highest multiple response (MR) value with the highest element concentration values for aluminum (Al), manganese (Mn), copper (Cu), and selenium (Se), indicating conditions allowing for the determination of all chemical elements simultaneously. This run No. 7 corresponds to the acid mixture No. 7 (detected acid mixture) (about 7 mL of HNO.sub.3:H.sub.2O (1:1):about 2 mL of hydrogen peroxide (H.sub.2O.sub.2)) as shown in Table 1.

(55) TABLE-US-00002 TABLE 2 The normalization of each element and multiple responses (MR). Normalization Run Cr Order Na Mg Al K Ca V ?g/g Mn Fe Co Cu Zn Se Ba MR 1 0.07 0.76 0.55 0.85 0.85 0.02 0.48 0.91 0.50 0.30 0.55 0.79 0.05 0.38 7.07 2 0.02 0.66 0.56 0.73 0.72 0.02 0.09 0.76 0.25 0.28 0.47 0.81 0.02 0.32 5.72 3 0.05 0.69 0.44 0.77 0.77 0.02 0.59 0.81 0.28 0.21 0.07 0.84 0.06 0.30 5.91 4 0.05 0.74 0.66 0.80 0.79 0.02 0.27 0.83 0.32 0.57 0.11 1.00 0.22 0.51 6.90 5 0.54 0.84 0.48 0.88 0.95 0.03 0.96 0.96 0.57 0.53 0.94 0.85 0.04 1.00 9.58 6 0.21 0.81 0.51 0.85 0.87 0.05 0.45 0.89 0.35 0.29 0.57 0.80 0.08 0.40 7.13 7 0.47 0.87 1.00 0.90 0.98 0.03 1.00 1.00 0.74 0.23 1.00 0.95 1.00 0.47 10.64 8 0.12 0.87 0.61 0.88 0.88 0.03 0.19 0.91 0.35 0.40 0.64 0.85 0.18 0.41 7.32 9 0.22 0.85 0.45 0.90 0.92 0.03 0.64 0.93 0.40 0.25 0.55 0.77 0.25 0.46 7.61 10 0.30 0.88 0.72 0.95 0.97 0.03 0.29 0.99 0.48 0.31 0.57 0.84 0.48 0.37 8.17 11 0.26 0.89 0.49 0.88 0.91 0.02 0.57 0.92 0.39 0.20 0.16 0.75 0.08 0.36 6.89 12 0.28 0.90 0.50 0.85 0.88 0.02 0.95 0.89 0.46 0.23 0.62 0.76 0.50 0.43 8.26 13 0.85 0.96 0.74 0.91 0.95 0.01 0.59 0.91 0.86 0.26 0.78 0.70 0.74 0.42 9.69 14 0.56 1.00 0.73 1.00 1.00 0.01 0.63 0.97 0.79 0.01 0.56 0.65 0.58 0.43 8.94 15 0.05 0.95 0.77 0.84 0.83 0.08 0.17 0.86 0.36 0.22 0.58 0.71 0.08 0.50 7.01 16 0.08 0.92 0.76 0.80 0.79 0.02 0.09 0.82 0.40 0.19 0.29 0.67 0.18 0.41 6.44 17 1.00 0.96 0.34 0.87 0.94 0.02 1.00 0.89 1.00 0.27 0.71 0.70 0.43 0.39 9.52 18 0.28 0.86 0.75 0.74 0.78 0.02 0.60 0.78 0.92 0.32 0.73 0.74 0.38 0.36 8.27 19 0.08 0.95 0.59 0.75 0.76 0.02 0.28 0.79 0.36 0.25 0.59 0.66 0.31 0.37 6.75 20 0.07 0.85 0.77 0.67 0.66 0.03 0.09 0.68 0.35 0.21 0.52 0.58 0.26 0.38 6.13 21 0.14 0.94 0.78 0.78 0.78 0.02 0.29 0.82 0.48 0.29 0.67 0.70 0.09 0.38 7.14 22 0.07 0.88 0.65 0.73 0.71 0.01 0.28 0.74 0.40 0.09 0.13 0.55 0.30 0.36 5.91 23 0.25 0.93 0.79 0.79 0.78 1.00 0.23 0.83 0.52 0.23 0.85 0.74 0.09 0.40 8.42 24 0.15 0.94 0.78 0.75 0.72 0.03 0.06 0.78 0.42 1.00 0.28 0.64 0.41 0.39 7.35 25 0.20 0.94 0.92 0.72 0.71 0.02 0.10 0.76 0.47 0.20 0.58 0.59 0.32 0.37 6.90 26 0.18 0.89 0.63 0.69 0.68 0.02 0.13 0.72 0.44 0.17 0.57 0.54 0.31 0.45 6.42 27 0.19 0.62 1.00 0.48 0.50 0.03 0.33 0.57 0.92 0.86 0.71 0.51 0.36 0.31 7.37

(56) TABLE-US-00003 TABLE 3 Multiple responses (MR) and chemical element concentrations during Box-Behnken design digesting experiments. 23 24 27 39 7 51 52 55 56 59 63 66 78 137 Run Na Mg Al K Ca V Cr Ma Fe Co Cu Za Se Ba Order ?g/g mg/g ?g/g mg/g mg/g ?g/g ?g/g ?g/g ?g/g ?g/g ?g/g ?g/g ?g/g ?g/g MR 1 13.270 1.515 19.457 14.829 1.862 0.036 0.352 7.119 36.347 0.1 9.154 0.909 0.0301 16.909 7.070 2 3.513 1.311 19.941 12.757 1.573 0.04 0.069 5.945 18.224 0.092 7.784 0.938 0.0137 14.158 5.721 3 9.824 1.381 15.359 13.448 1.681 0.036 0.434 6.319 20.554 0.069 1.122 0.974 0.0383 13.204 5.907 4 9.636 1.472 23.256 13.873 1.722 0.039 0.199 6.447 23.467 0.19 1.892 1.155 0.134 22.730 6.895 5 96.978 1.667 17.079 15.254 2.091 0.055 0.703 7.468 41.520 0.178 15.512 0.986 0.0242 44.619 9.578 6 38.217 1.622 18.043 14.796 1.896 0.087 0.328 6.936 25.341 0.097 9.394 0.926 0.0475 17.905 7.130 7 83.953 1.728 35.300 15.662 2.155 0.059 0.728 7.799 54.186 0.077 16.524 1.098 0.5956 20.788 10.637 8 22.173 1.742 21.505 15.267 1.932 0.047 0.137 7.094 25.895 0.132 10.61 0.984 0.1067 18.136 7.319 9 38.554 1.693 15.837 15.717 2.008 0.044 0.468 7.287 29.036 0.083 9.024 0.892 0.148 20.665 7.608 10 53.261 1.756 25.256 16.554 2.115 0.049 0.213 7.693 35.264 0.102 9.476 0.965 0.2877 16.725 8.171 11 46.161 1.785 17.437 15.387 1.988 0.036 0.414 7.163 28.627 0.067 2.718 0.864 0.0493 16.187 6.894 12 51.030 1.788 17.554 14.713 1.925 0.037 0.696 6.923 33.665 0.077 10.176 0.876 0.2982 19.206 8.260 13 152.853 1.92 26.223 15.846 2.078 0.023 0.431 7.12 62.766 0.088 12.956 0.804 0.4397 18.752 9.694 14 101.035 1.996 25.827 17.403 2.19 0.023 0.462 7.561 58.078 0.004 9.242 0.755 0.3447 19.219 8.939 15 8.091 1.902 27.343 14.636 1.816 0.133 0.127 6.703 26.131 0.074 9.574 0.816 0.0493 22.502 7.005 16 15.198 1.842 26.990 13.996 1.737 0.04 0.069 6.37 28.923 0.063 4.792 0.770 0.1101 18.418 6.443 17 179.261 1.916 12.094 15.213 2.051 0.03 0.731 6.931 73.074 0.091 11.676 0.804 0.2542 17.552 9.515 18 50.777 1.724 26.491 12.956 1.707 0.032 0.442 6.095 66.935 0.108 12.018 0.858 0.2269 15.943 8.275 19 13.743 1.892 20.778 13.135 1.667 0.033 0.203 6.172 26.073 0.082 9.774 0.763 0.1851 16.530 6.754 20 12.914 1.699 27.208 11.647 1.449 0.046 0.069 5.316 25.620 0.071 8.606 0.671 0.1558 16.763 6.130 21 24.429 1.871 27.433 13.588 1.711 0.034 0.211 6.362 35.055 0.097 11.082 0.803 0.0516 17.04 7.142 22 13.285 1.757 22.853 12.734 1.557 0.018 0.204 5.753 29.573 0.03 2.178 0.639 0.1804 15.873 5.910 23 44.270 1.854 27.731 13.703 1.716 1.744 0.17 6.451 37.800 0.075 14.002 0.858 0.0546 18.028 8.421 24 26.262 1.883 27.451 12.984 1.576 0.045 0.046 6.071 31.050 0.333 4.702 0.738 0.2436 17.462 7.349 15 35.761 1.872 32.556 12.536 1.565 0.03 0.073 5.934 34.154 0.068 9.578 0.684 0.1884 16.531 6.903 26 32.937 1.77 22.315 11.954 1.493 0.028 0.092 5.634 32.469 0.058 9.338 0.629 0.1832 20.020 6.420 27 33.950 1.242 35.264 8.389 1.09 0.047 0.239 4.424 66.863 0.285 11.744 0.589 0.2131 13.955 7.374

Example 3

(57) Microwave Digestion

(58) The process of performing microwave digestion was conducted using the following steps.

(59) Preparation of pulp: Pulp from a baobab fruit was manually separated from the seed of the baobab fruit.

(60) Homogenization: The baobab fruit pulp was crushed and homogenized using an agate mortar and pestle to obtain a homogenized baobab fruit pulp.

(61) Sieving: The homogenized baobab fruit pulp was placed in a plastic sieve with 1 mm pores to obtain baobab fruit fine powder.

(62) Preparation of acid mixture: The detected acid mixture as mentioned in Example 2 was prepared. The detected acid mixture comprises about 7 mL of HNO.sub.3:H.sub.2O (1:1):about 2 mL of hydrogen peroxide (H.sub.2O.sub.2) as shown in Table 1.

(63) Preparation of solution: About 0.1 g of the baobab fruit fine powder was added to the prepared detected acid mixture within a vessel to obtain a solution within the vessel.

(64) Heating: The vessel was sealed and the solution was heated to digest the baobab fruit fine powder in the solution within the sealed vessel in an oven cavity of a microwave digestion at about 100? C. for about 5 minutes, then at about 130? C. for about 15 minutes, and thereafter cooling the solution within the sealed vessel to obtain a digested baobab fruit fine powder in the solution within the sealed vessel.

(65) Filtering: The digested baobab fruit fine powder was filtered from the solution to obtain a filtered digested baobab fruit fine powder.

(66) Preparation of a mixture: The filtered digested baobab fruit fine powder was diluted with about 100 mL of deionized water to obtain a mixture.

(67) ICP-MS: The plurality of chemical elements in the mixture were measured using inductively coupled plasma mass spectrometry (ICP-MS). The plurality of chemical elements is selected from the group consisting of sodium, magnesium, aluminum, potassium, calcium, vanadium, chromium, manganese, cobalt, copper, selenium, barium, other chemical elements, and combinations thereof.

Example 4

(68) Determining the Accuracy of the Response Surface Methodology (Box-Behnken Design)

(69) The process of determining accuracy of the response surface methodology (Box-Behnken design) was conducted using the following steps.

(70) Baobab fruit: A baobab fruit was obtained. The baobab fruit was purchased from a local market and used as a home control (CS) sample.

(71) Preparation of an analyte solution: An analyte solution was prepared. The analyte solution is selected from the group consisting of barium, sodium, magnesium, aluminum, potassium, calcium, vanadium, chromium, manganese, cobalt, copper, zinc, iron, and selenium, other chemical elements, and combinations thereof.

(72) Adding the analyte solution to the baobab fruit: The analyte solution was added at concentrations of about 25 ug/L, about 50 ug/L, and about 100 ug/L to the baobab fruit as shown in Table 4.

(73) Recovery rates: Recovery rates (R) for each chemical elements in the baobab fruit were determined.

(74) In order to determine the recovery rates (R) for each of the chemical elements, the following formula was used:

(75) $R=\frac{C_{obs}-C_{\mathrm{native}}}{C_{\mathrm{spiked}}}?100$

(76) Where C.sub.obs is the analyte solution concentration of a chemical element in the spiked sample. C.sub.native is the analyte solution concentration in an unspiked control sample. C.sub.spiked is the analyte solution concentration in the analyte solution added to the sample.

(77) As shown in Table 4, the accuracy was established by calculating chemical element recoveries in control samples spiked with three known quantities (about 25 ug/L, about 50 ug/L, and about 100 ug/L) and 3 replicates for each level. Results varied from about 71.40?about 1.425 to about 108.95?about 0.459. The results confirmed the method's sensitivity for the simultaneous measurement of sodium (Na), magnesium (Mg), aluminum (Al), potassium (K), calcium (Ca), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), copper (Cu), zinc (Zn), selenium (Se), and barium (Ba) in the pulp of baobab fruit.

(78) TABLE-US-00004 TABLE 4 The chemical elements recoveries of spiked samples occurred at three different concentrations (25 ug/L, 50 ug/L, and 100 ug/L). Spike 1 Spike 2 Spike 3 (25 ?g/L) ? (50 ?g/L) ? (100 ?g/L) ? Element RSD RSD RSD Na 90.79 ? 1.308 94.90 ? 0.090 98.52 ? 0.602 Mg 93.20 ? 1.299 101.67 ? 0.712 101.16 ? 0.262 Al 90.62 ? 1.309 92.21 ? 1.387 97.16 ? 3.960 K 103.03 ? 1.299 99.42 ? 0.060 98.67 ? 0.098 Ca 71.40 ? 1.425 108.95 ? 0.459 101.04 ? 0.225 V 86.65 ? 1.366 86.46 ? 0.002 86.93 ? 0.001 Cr 86.14 ? 0.323 85.82 ? 0.004 86.81 ? 0.014 Mn 84.05 ? 1.419 84.35 ? 0.018 84.42 ? 0.010 Fe 99.51 ? 1.319 84.30 ? 0.023 81.76 ? 0.013 Co 84.91 ? 1.407 84.80 ? 0.011 86.15 ? 0.019 Cu 99.39 ? 1.299 90.86 ? 0.014 86.62 ? 0.017 Zn 84.57 ? 1.442 87.77 ? 0.003 86.32 ? 0.018 Se 98.06 ? 1.333 77.09 ? 0.027 81.37 ? 0.006 Ba 90.60 ? 1.299 90.59 ? 0.046 91.47 ? 0.153

Example 5

(79) ICH Principles

(80) Using ICH principles (International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use), a calibration linearity, accuracy, precision, limits of detection (LOD), and limits of quantification (LOQ) validation features of each chemical element's analytical method were evaluated. The chemical element calibration curves were drawn over the concentration ranges of about 0.01 ug/L to about 150 ug/L, and the linearity of the calibration curves were demonstrated by the correlation coefficients (R.sup.2). The correlation coefficients (R.sup.2) ranged between about 0.9947 and about 1.00 as shown in Table 5. Also, repeatability values were calculated as relative standard deviation (RSD) from the examination of three sample analyte solutions digested on the same day using the same procedure. The relative standard deviation (RSD) values were about ?7.1587 as shown in Table 5.

(81) The LOD and LOQ of each chemical elements were found to be about 3 and about 10 standard deviations, respectively, above the slope of the calibration curve. The LOD and LOQ values as shown in Table 5 ranged from about 0.0003 ng/L to about 0.7920 ng/L and from about 0.0011 ng/L to about 2.6400 ng/L, respectively.

(82) TABLE-US-00005 TABLE 5 Mass, correlation coefficients (R2), limits of detection (LOD), limits of quantification (LOQ), and repeatability (RSD) for determining chemical elements in the pulp of baobab fruit. LOD LOQ Repeatability Name Mass R.sup.2 ng/L ng/L (RSD) Na 23 0.9970 0.0037 0.0123 5.5008 Mg 24 0.9991 0.0030 0.0098 6.6120 Al 27 0.9991 0.0080 0.0268 3.2212 K 39 0.9978 0.0413 0.1375 1.8535 Ca 44 0.9985 0.5007 1.6689 3.1306 V 51 0.9993 0.0010 0.0033 2.6660 Cr 52 0.9993 0.0168 0.0560 2.0996 Mn 55 0.9994 0.0067 0.0225 0.8059 Fe 56 0.9947 0.0405 0.1350 3.7684 Co 59 0.9993 0.0003 0.0011 2.8272 Cu 63 1.0000 0.7920 2.6400 7.1587 Zn 66 0.9997 0.4061 1.3537 4.7788 Se 78 0.9988 0.4461 1.4871 2.1687 Ba 137 0.9999 0.0064 0.0213 2.7410

(83) It is to be understood that the method of measuring a plurality of chemical elements in a baobab fruit pulp, the method of optimizing microwave digestion, and the method of performing microwave digestion are not limited to the specific embodiments described above, but encompasses any and all embodiments within the scope of the generic language of the following claims enabled by the embodiments described herein, or otherwise shown in the drawings or described above in terms sufficient to enable one of ordinary skill in the art to make and use the claimed subject matter.