Evaluation of pesticide residues and heavy metals

Overview

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University of Nigeria, Nsukka, Nigeria lindane and t-Nonachlor. The concentration of HCB ranged between 0.0799 ± 0.06 mg/kg and 0.1596
± 0.00 mg/kg, which was greater than the permitted maximum limit of 0.5 mg/kg established by the US
Energy and Bioproducts Research predetermined maximum allowed limits. Endosulfan concentrations in cocoyam (0.2500 mg/kg) and potato
Birmingham, UK (0.3265 mg/kg) were higher than the limits allowed by the Canadian Department of Industrial Research. The
of cobalt in yam (0.036 mg/kg) and the maximum allowed concentration (0.043 mg/kg). Lead was detected
Similarly, cocoyam was found to have a significant mercury content (0.658 mg/kg), but mercury content was
FuNDING: value and income. These roots/tubers have a crude fat content on the fresh weight of 0.1–0.5% and 1–3% on
None the dry weight, of which 80% is starch. The carbohydrate content of cassava is larger than that of potatoes.8
yam provides energy in the range of 80–120 kcal/100 g.10 Vitamin A is produced from beta-carotene, and it is
and 0.090) and aldrin (0.0000 and 0.0937) mg/kg, respectively.15 The
concentration of isopropylamine in yam was 0.2165 ± 0.00 mg/kg
and in cassava was 0.1649 ± 0.00 mg/kg, while the concentration
of t-Nonachlor in yam was 0.1093 ± 0.00 mg/kg and in cassava was Heavy metal analysis
0.0006 ± 0.00 mg/kg, as reported by Omeje et al.15 Adeyeye and
yam (aldrin = ~5.0 µg/kg; dieldrin = ~24.0 µg/kg and p,p´-DDE = performed using a Varian AA240 Atomic Absorption Spectrophotometer
~13.0 µg/kg) and cassava (aldrin = ~6.0 µg/kg; dieldrin = ~31.0 µg/ (AAS; Varian Inc., Palo Alto, CA, USA) equipped with an acetylene air
kg and p,p´-DDE = ~21.0 µg/kg) in their study. Heavy metals have been flame, adapting the protocol described by Quarcoo and Adotey23, with
amount of cadmium (Cd) found in yam was reported to be 0.11 mg/kg, were equipped with platform instrument settings and furnace programs
kg of Pb, 42 mg/kg of copper (Cu), 24 mg/kg of zinc (Zn), 18 mg/kg of the sample (~2 g) was put into a digestion flask, along with 20 mL of
manganese (Mn) and 12 mg/kg of Ni were reported by Wilberforce and acid mixture (which consisted of 650 mL concentrated HNO3; 80 mL
0.017 mg/kg.15 According to Onianwa et al.19, the range reported for Ni until a clear digest was obtained. The digest was diluted with distilled
concentrations in tubers is 0.93–1.79 mg/kg. Akinyele and Shokunbi20 water to the 100 mL mark. The acid level samples as they came along
detected Mn in yams (~4.42 mg/kg), and Orisakwe et al.21 reported Pb were monitored by a pH meter. The digestate was quantified, assayed for
(~0.33 mg/kg), Cd (~0.10 mg/kg) and Ni (~0.30 mg/kg) in cassava. heavy metals using a Varian AA240 Spectrophotometer, and reported in
The internal standard was aldrin solution (Sigma-Aldrich) in acetone at a the tubers are shown in Table 1.
Samples studied (Table 1). Among the samples, the maximum level of Ni (0.012
In April 2022, fresh tubers weighing 500 g each (cassava, yam, ± 0.00 mg/kg) was found in cassava. The concentration of Ni was 0.009
cocoyam, potato, water yam and carrot) were purchased from Nsukka ± 0.00 mg/kg in cocoyam, 0.006 ± 0.00 in yam, 0.007 ± 0.00 in
stored at 4 °C for further analysis. those evaluated. The maximum Co concentration of 0.036 ± 0.00 mg/kg
was detected in yam. A Co concentration of 0.026 ± 0.00 mg/kg was
Pesticide residue analysis detected in cocoyam, 0.016 ± 0.00 mg/kg in water yam, 0.011 ± 0.00
mg/kg in cassava, 0.010 ± 0.00 mg/kg in carrot and 0.002 ± 0.00 mg/
was carried out with 300 mL of n–hexane for 24 h. The obtained crude ± 0.00 mg/kg and 0.083 ± 0.00 mg/kg were found in cocoyam and
to dryness. The sample residue (1 mL) was measured into 50 mL of 0.073 ± 0.00 mg/kg and 0.078 ± 0.00 mg/kg, respectively. The lowest
chloroform transferred to a 100 mL volumetric flask and diluted. Most of level of Cr was detected in carrots (0.010 ± 0.00 mg/kg). Similarly,
of the solvent mixture (20% benzene and 55% methanol). The mixture (0.036 ± 0.00 mg/kg) found in yam. Co was detected in the potato
sample, although at the lowest concentration (0.00 ± 0.00 mg/kg) when Metallic mercury exposure has been reported to cause lung damage.26
compared to those of the other samples. The concentration of Hg in the cocoyam (0.658 ± 0.00 mg/kg) was
found in cassava, yam and cocoyam were 0.045 mg/kg, 0.010 mg/
kg and 0.049 mg/kg, respectively. Also, 0.056 ± 0.00 mg/kg, 0.037 Table 2 shows the concentrations of pesticide residues present in
± 0.00 mg/kg and 0.019 ± 0.00 mg/kg As were detected in samples the tubers studied. 2,4-dichlorophenoxyacetic acid, dichlorobiphenyl,
concentration (0.010–0.00 mg/kg) (Table 1). The presence of Mn, Cd the different pesticide residues detected in the six tubers studied. Aldrin was

Methods (brief)

Department of Biochemistry, evaluated by gas chromatography–mass spectrometry and atomic absorption spectroscopy. The detected
University of Nigeria, Nsukka, Nigeria pesticide residues in the samples were 2,4-dichlorophenoxyacetic acid, glyphosate, hexachlorobenzene
heavy metals detected in these samples include cobalt, nickel, lead, manganese, chromium, arsenic and
Benjamin Ezema mercury in at least one of the samples evaluated. There was not much difference between the concentration
chromatography–mass spectrometry, regions.8 The production of these products and their conversion into goods derived from food is expanding, and
atomic absorption spectroscopy, farmers profit significantly from their market.8 Their high post-harvest losses, due to contamination by external
the tubers that are commonly consumed, such as cassava, yam and heating, the organic sample was extracted with n–hexane and water
yam (aldrin = ~5.0 µg/kg; dieldrin = ~24.0 µg/kg and p,p´-DDE = performed using a Varian AA240 Atomic Absorption Spectrophotometer
~13.0 µg/kg) and cassava (aldrin = ~6.0 µg/kg; dieldrin = ~31.0 µg/ (AAS; Varian Inc., Palo Alto, CA, USA) equipped with an acetylene air
found in tubers like potatoes, yams and cassava in previous studies. The slight modifications. The pyrolytic-coated graphite tubes of the AAS
kg of Pb, 42 mg/kg of copper (Cu), 24 mg/kg of zinc (Zn), 18 mg/kg of the sample (~2 g) was put into a digestion flask, along with 20 mL of
concentrations in tubers is 0.93–1.79 mg/kg. Akinyele and Shokunbi20 water to the 100 mL mark. The acid level samples as they came along
and concentration of common food pesticide residues and heavy were digested using conditions consistent with those of the samples.
cultivated in Nigeria using gas chromatography–mass spectrometry Statistical analysis
(GC–MS) and atomic absorption spectroscopy. The emergent heavy metal and pesticide residue data were obtained
from triplicate determinations of different samples from a given food
The chemicals and reagents used were of analytical quality and included studied food crop samples. Data are expressed as mean ± standard
concentration of 50 ng/L. All the heavy metals evaluated were present in the samples, except for

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Update history

The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git. When DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.

Commit	Date	Change	Description
b01ec52c	2026-08-04	major	2 sections added
d49e450f	2026-08-03	major	5 sections added; narrative text revised