Five (5) g of each flour were introduced into 50 mL falcon tube, then 10 mL of distilled water were added and the whole was briefly vortexed. The solution obtained was left to stand for a few minutes. Ten (10) mL of acetonitrile containing 2% acetic acid were added to the previous mixture, and the whole was vortexed for 5 minutes. Then, 4 g of magnesium sulphate (MgSO₄) and 1g of sodium chloride (NaCl) were added and the mixture was vortexed for one minute. The mixture previously obtained was centrifuged for 5 minutes at 4000 rpm.

After centrifugation, 6 mL of the supernatant was taken for each sample, then introduced into falcon tubes containing each, 1200 mg of magnesium sulphate (MgSO₄) and 400 mg of PSA (Primary and Secondary Amine, used to improve

S: sample; M: market; H: Household; S: Supermarket; W: White; Y: Yellow.

purification by removing sugars, fatty acids and organic acids). The mixture obtained was stirred for 1 min and then centrifuged for 5 min at 4000 rpm. Then, the supernatant was extracted using a hydrophobic filter and a syringe. The solutions obtained were introduced into vials.

HPLC/MS/MS method described by Oplatowska-Stachowiak [17] was used to determine and quantify aflatoxins in homogenized maize flours samples. Standards obtained in powder form were prepared at the concentration 1 mg/mL in the appropriate amount of solvent (MeCN or MeOH) according to the manufacturer’s instructions. Different solutions of standards were prepared as calibrants for the instrument to determine the limit of detection of each aflatoxin. The concentrated standard sets were also used for preparing calibrants in matrix. The aflatoxin quantitation was achieved by preparing matrix-matched calibration curves with blank maize flour. The purified products were separated using a C18 column. The mass spectrometry was conducted by using positive electrospray ionization (ESI+) and multiple reaction monitoring (MRM) models. Data acquisition and quantification were performed using Mass Hunter Workstation B.04.01 software (Agilent Technologies).

The results obtained for the samples taken from the markets are presented in Table 2. The results obtained show that aflatoxins B1, B2 and G1 are present in most of the samples of white maize flours with average levels of 7.27 µg/kg, 5.59 µg/kg and 22.62 µg/kg respectively. For yellow maize flour, the levels were 6.14 µg/kg, 12.13 µg/kg and 10.36 µg/kg respectively for AFB1, AFB2 and AFG1. Total aflatoxin levels in white maize flours were higher than those in yellow maize flours with average levels of 26.61 µg/kg and 18.20 µg/kg respectively.

The results obtained for the samples taken from households are presented in Table 3. They show that in general, aflatoxins are more present in yellow maize than in white maize. Similarly, the total aflatoxin contents of yellow maize are higher than those of white maize with respective average contents of 29.34 µg/kg and 17.04 µg/kg respectively. For yellow maize flour, the average levels were 6.46 µg/kg, 7.29 µg/kg and 24.73 µg/kg respectively for AFB1, AFB2 and AFG1. For this type of flour, aflatoxin G2 was only recorded in one sample of white maize

Lod: Limit of detection.

Lod: Limit of detection.

flour with a content of 35.68 µg/kg.

The results obtained for the samples taken in Supermarket are presented in Table 4. These results show that aflatoxins are less present in the supermarket samples than in other two cases. Only one yellow maize flour sample contains AFB2 with a level of 4.08 μg/kg. For white maize flours, the average levels were 11.68 μg/kg, 7.02 μg/kg, 32.22 μg/kg and 26.45 μg/kg respectively for AFB1, AFB2, AFG1, and AFT.

For all 28 samples, the aflatoxin levels are highly variable. They ranged from

Lod: Limit of detection.

undetected to 36.69 µg/kg and from undetected to 64.25 µg/kg respectively for AFB1 and AFT. These aflatoxins levels are similar to that of Bamba et al. [4] with average AFB1 contents of 0.79 ± 0.04 µg/kg to 20.92 ± 4.63 µg/kg in maize samples from 5 regions of Côte d’Ivoire. The AFB1 contents obtained during this study are higher than those revealed during a study carried out in Côte d’Ivoire on samples of maize flour with levels ranging from 0.12 µg/kg to 3.18 µg/kg [9] . They are also superior to that of Maskito et al. [6] who obtained a maximum AFB1 level of 15.62 µg/kg in maize flours in Kenya.

Contrariwise, higher average levels of AFB1 (108 µg/kg) with ranges of 5.7 to 309 µg/kg were found in maize flour samples from markets in Abidjan [18] . Similarly, AFB1 levels up to 1081 µg/kg were reported in maize samples [19] .

For AFT, the levels recorded during this this study were similar to those of Bamba et al. [4] recorder in samples, ranging from 2.63 ± 2.35 µg/kg to 60.78 ± 30.24 µg/kg from five regions in Côte d’Ivoire. In contrast, high level of AFT were revealed by Kouadio et al. [18] which obtained a mean of 129 µg/kg with ranges of 4.5 to 330 in samples from Côte d’Ivoire. However, Manizan et al. [7] detected AFB2, and AFG1 at lower levels in maize flour samples (8 µg/kg for both AFB2 and AFG1) compared to the rates recorded during this study. The same authors detected 6 µg/kg for AFG2 in the same samples.

This study shows that in general, aflatoxin levels are lower in samples from supermarkets than in samples from markets and households. However, the statistical analysis shows that there is no significant difference between the AFB1 and AFT contents of flours from the three origins (p = 0.726 and p = 0.966 respectively). The low level of aflatoxins in supermarket samples can be explained by the fact that supermarkets source their supplies from particular producers who better respect GHP and GMP (Good Manufacturing Practices).

For the household samples, the aflatoxin level of yellow maize flours is higher than those of white maize flours. however, the analysis of variance shows that there is no significant difference between the aflatoxin contents of the two types of maize flours in the case of household samples (p = 0.168). According to some producers, yellow maize flour is often produced without ridding the grain of the bran. This could explain the higher levels of aflatoxins in this type of flour. Moreover, according to Diarra et al. [20] , yellow maize is most often intended for animal nutrition, so, its conservation is not always done according to the same requirements as that of white maize. This could also justify the high levels of aflatoxins in yellow maize flours.