2.3.2. Determination of Maize Grain Physical Quality

Cone and quartering method were used to sub-divide the mixed sample several times to get a representative amount of 100 g. Grains were sorted according to stated parameters or defects (diseased, discolored, broken/chipped, insect damaged, stained, germinated, shriveled, other grains, total defective, inorganic matter, organic matter). After thorough sorting, the percentage defects were then calculated using Equation (1):

$$\text{Percentage defective grains} = \frac{\text{Weight of defective grains (g)}}{\text{Weight of sample (g)}} \times 100\tag{1}$$

The analysis was conducted in triplicate and the resulting average percentages for the various defects were then recorded and compared with the Ghana Standards Authority's grading specification.

2.3.3. Aflatoxin Analysis

• Source of Reagents

ENVIROLOGIX QUIKSCAN® DB5 Buffer solution and Sodium Lauryl Sulphate were obtained from Portland-USA, and 50% *v/v* ethanol solution was prepared using absolute ethanol and distilled water.

• Cleaning of Glassware

Preceding the analysis, glassware was cleaned using Ecolab® Food grade detergent and washed with deionized water. They were further cleaned with acetone, dehydrated and stored in dust free cabinets until required.

• Extraction and Purification

The sample was mixed thoroughly to achieve a homogenous mixture. About 500 g of the sample was milled (SUS304, China) to attain a granulation of 841 microns. Then, 25 g of the milled sample was weighed into a beaker. One packet of extraction powder was added to the flour as well as 50 mL of 50% ethanol. It was then shaken vigorously for 2 min by hand and allowed to settle for 2 min for a clear separation into lipid and aqueous phases. Finally, 100 μL was pipetted from different portions of the lipid phase into a centrifuge tube and centrifuged for 1 min in a LabniqueTM centrifuge (Spinplus-6, China).

• Analysis

First, 200 μL of buffer solution was pipetted into a reaction vial, and 100 μL of the clarified extract containing the analyte was pipetted, added and mixed thoroughly. A test strip was then added to the vial and allowed to run for 5 min. Test strips were immediately cut at the top of the arrow tape and inserted into a QuickScan® reader

with barcode facing down. A corn high sensitivity Matrix Group was selected and the result was read.

#### 2.3.4. Pesticide Residue Analysis

Pesticide residue analysis was done using the QuCHERS method of analysis, which involved extraction, purification and quantification of the extract via the chromatographic method as described below.

1. Extraction

Five grams of comminuted sample was weighed into a 50 mL centrifuge tube and 1 mL of deionized water was added, and then it was vortexed for 30 s. About 10 mL of acetonitrile was added, and it was vortexed again for 60 s. A mixture containing 4 g of 0.2 g magnesium sulphate anhydrous, 1 g of 0.05 g sodium chloride, 1 g of 0.05 g trisodium citrate dihydrate and 0.5 g of 0.03 g disodium hydrogen citrate sesquihydrate was added before being immediately vortexed for 1 min and centrifuged (Spinplus-6, China) for 5 min at 3000 U/min.

2. Dispersive Solid Phase Extraction

A 6 mL aliquot of the extract was pipetted into a polypropylene centrifugation tube containing 150 mg primary and secondary amine and 900 mg magnesium sulphate. The tube was closed and shaken strongly for 30 s and centrifuged for 300 s at 3000 U/min. For matrixes containing low amounts of fat, freezing out and addition of 150 mg of carbon-18 was done.

About 4 mL of the cleaned extract was pipetted into a round bottom flask and the pH adjusted quickly to 5 by adding 40 μL of 5% formic acid solution in acetonitrile (*v/v*), and the filtrate concentrated below 40 ◦C on a rotary evaporator and 1 mL of ethyl acetate was added for re-dissolution. About 20 μL of 1% polyethylene glycol solution in ethyl acetate (*v/v*) was added and the extract transferred into a 2 mL standard opening vial for quantitation via GC-ECD and GC-PFPD. Qualitative confirmation for positive detection was done via GC/MS.
