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A Research Paper On The Analysis Of The Levels Of Nitrate In Homemade Brews, Spirits, In Water And Raw Materials In Nairobi County

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A Research Paper On The Analysis Of The Levels Of Nitrate In Homemade Brews, Spirits, In Water And Raw Materials In Nairobi County

Abstract and Figures

Increased cases of deaths as a result of taking home made brews/spirits have been a major concern in our country. Recently, many lives have been lost due to the ignorance of the brewers and their patrons. This study was carried out to determine the levels of nitrate in home -made brews, home -made spirits, raw materials and water. Four hundred and forty (440) home -made alcoholic beverages, one hundred and ten (110) water and eighteen (18) raw materials samples obtained from various parts of Nairobi slums and its environs were analyzed for nitrate. UV-visible Spectrophotometry was used in the research. Some samples contained analyte values above limits set. The concentrations of nitrate varied from non detectable (ND) to 46.3 ± 1.404 mg/l. The recommended maximum contamination levels set by KEBS/WHO for nitrate in alcohols is nitrate 50 mg/l. Most of the home made brews and spirits analyzed in this study had values slightly lower than the levels recommended by the World Health Organization. Values of nitrate were observed to be generally high in the brews/spirits and the raw materials used. The raw materials may have contributed in elevating the levels of these pollutants in the brews. These findings are therefore useful since they provide a justified cause for the Kenyan Government to fight the selling of local alcoholic beverages.
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A Research Paper On The Analysis Of The Levels
Of Nitrate In Homemade Brews, Spirits, In Water
And Raw Materials In Nairobi County
Masime Jeremiah O, Wanjau Ruth, Murungi Jane, Onindo Charles
Abstract: Increased cases of deaths as a result of taking home made brews/spirits have been a major concern in our country. Recently, many lives
have been lost due to the ignorance of the brewers and their patrons. This study was carried out to determine the levels of nitrate in home - made brews,
home - made spirits, raw materials and water. Four hundred and forty (440) home - made alcoholic beverages, one hundred and ten (110) water and
eighteen (18) raw materials samples obtained from various parts of Nairobi slums and its environs were analyzed for nitrate. UV-visible
Spectrophotometry was used in the research. Some samples contained analyte values above limits set. The concentrations of nitrate varied from non
detectable (ND) to 46.3 ± 1.404 mg/l. The recommended maximum contamination levels set by KEBS/WHO for nitrate in alcohols is nitrate 50 mg/l. Most
of the home made brews and spirits analyzed in this study had values slightly lower than the levels recommended by the World Health Organization.
Values of nitrate were observed to be generally high in the brews/spirits and the raw materials used. The raw materials may have contributed in
elevating the levels of these pollutants in the brews. These findings are therefore useful since they provide a justified cause for the Kenyan Government
to fight the selling of local alcoholic beverages.
Key Words: Nitrate, UV-Visible Spectroscopy, Brews, Spirits, Raw materials
——————————
——————————
1.0 INTRODUCTION
1.1 Nitrate, its sources and health effects
Nitrates may be found naturally in water or enter the
supplies through a number of sources. Sources of nitrate
pollution include; use of fertilizers, animal wastes, municipal
and industrial waste, lightening among other sources.
Nitrates are the products of aerobic stabilization of organic
nitrogen [14]. They may also enter water via fertilizers from
agricultural runoffs. They can also be formed during
thunderstorms and lightening [14]. The concentrations of
nitrates in surface and ground water vary within wide limits
depending on geochemical conditions, human and animal
waste management practices and on industrial discharge of
nitrogen compounds [14]. To protect those at risk, the
maximum contamination level (MCL) for nitrate in water is
50 mg/l as nitrate [7].
1.2 Alcohol drinking in developing countries
Almost every month, there are horror stories in the African
press about locally produced alcohol, which has poisoned
some unfortunate drinkers [5]. In Kenya, the making and
selling of any kind of alcohol by ordinary people is entirely
illegal, though widely practiced, allegedly because of
widespread corruption and non-enforcement of the law. At
least 137 people died in the Kenyan capital of Nairobi after
drinking an alcoholic brew laced with methanol [3]. A further
500 people were hospitalized across the capital, with some
serious condition, and there are reports that 20 people
became blind [3]. In August 1998, 85 people died after
drinking methanol contaminated liquor and in 1999, 17
people died [3]. Over the last two years 100 people have
been blinded as a result of consuming the drink [3]. It was
therefore disturbing to read similar stories from Kabale in
Uganda where adulterated waragi had blinded 20 people
while claiming the lives of 80 innocent Ugandans in one day
making a total of 114 deaths of Ugandans in different parts
of the country in the last eight months [11]. Alcoholism is a
national disease we must tackle.
1.3 Ultraviolet and visible absorption spectroscopy
(UV-Vis)
Nitrate was analyzed using this method. Ultraviolet and
visible (UV-Vis) absorption spectroscopy was the
measurement of the attenuation of a beam of light after it
passes through a sample or after reflection from a sample
surface. Absorption measurements can be at a single
wavelength or over an extended spectral range. Ultraviolet
and visible light are energetic enough to promote outer
electrons to higher energy levels, and UV-Visible
spectroscopy was usually applied to molecules or in organic
complexes in solution. The UV-Visible spectra have broad
features that are of limited use for sample identification but
are very useful for quantitative measurements [1].
Determination of the nitrite based on the reactions involving
sulfanilic acid with methyl anthranilate as the coupling
agents followed by reduction using Zn/NaCl and
diazotization has been applied successfully to determine
trace amounts of nitrite and nitrate in water and
pharmaceutical preparations [8].
2.0 MATERIALS AND METHODS
2.1 Samples and sampling
Sixteen (16) stations were targeted and ten samples of
each brew and water were selected. A total of one hundred
and thirty two (132) home-made alcoholic beverages, forty
eight (48) water and eighteen (18) raw materials samples
were analyzed for arsenic, nitrate, nitrite and phosphorus.
Six different raw materials were selected. Three samples of
each were obtained from various places in the sixteen
stations. These samples were randomly obtained from
various parts of Nairobi and outskirts taking into account the
requirements for the preparation of the brews. This
information was obtained from the people who sold the
brews. Sample of raw materials were obtained from market
places nearest to the beverage sampling stations. A 100 ml
samples were collected directly into specially cleaned,
pretested, polypropylene bottles using sample handling
techniques specially designed for collection of sample for
the analysis of metals at trace levels. The samples were
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then either laboratory preserved by the addition of 5 ml of
pretested 10 % HNO
3
per litre of sample, depending on the
time between sample collection and arrival at the
laboratory.
2.2 Nitrate and nitrite standards
All chemicals for nitrite and nitrate analysis were analytical
reagent grade. Doubly distilled water was used in the
preparation of all solutions in the experiments. Working
standard solutions were prepared by appropriate dilution.
Sulfanilic acid (0.5 g in 100ml water) and methyl
anthranilate (0.5 ml in 100 ml of alcohol) were used. The
following reagents were prepared by dissolving appropriate
amountsin water 2 M of HCl and 2 M NaOH (Narayana et
al., 2009). Nitrite stock solution (1000 µg/l) was prepared by
dissolving 0.1500g sodium nitrite in water and diluting to
100 ml. Nitrate stock solution (1000 µg/l) was prepared by
dissolving 0.7220 g potassium nitrate in water and diluting
to 100 ml.
2.3 UV-visible spectroscopy instrument
Nitrate was analyzed using, a SHADZU (Model No. UV-
2550) UV-Visible spectrophotometer with 1 cm matching
quartz cell were used for the absorbance measurements. A
WTW pH 330 pH meter was used [8].
2.4 Brews
The brew sample bottle (acid-washed, 125 ml polyethene
bottle) were rinsed 3 times before sampling. Filled to
approximately 2/3 full, tighten cap and freeze cruise, cast
Niskin bottle number were recorded on the bottle and data
sheet. All the brew sample bottles were first rinsed with the
alcohol for alcohol samples before the brew samples were
collected. The samples were then filtered, the residue
discarded and the filtrates from home made brews were
decolorized using activated charcoal and re-filtered until the
colour disappeared.
2.5 Raw materials
In the sample pretreatment, modified procedures for
washing and drying proposed by Santos et al. [13] and
Kawashima & Soares [6], respectively, were used. First,
each raw material samples were rinsed with distilled water
to remove dirt and other debris. Then the raw material
samples were brushed with polypropylene bristles and
washed with deionized water. The raw materials were then
grated with a polypropylene grater into porcelain containers.
Then the containers with the raw material samples were
dried in a laboratory oven at 65 ± 5 ºC for 24 h or until
reaching constant weight. Immediately afterwards, the
samples were stocked in polypropylene beakers and
covered with a PVC film. Finally, they were stored in a
desiccators awaiting digestion [12].
2.6 Digestion of brews
No digestion is performed on unfiltered samples prior to
analytical determinations. Portions of 20 ml of the
neutralized filtered brew samples were evaporated to
dryness in separate beakers. The residues were each
cooled and extracted with 1 ml phenol disulphonic acid
{prepared from 25 g of phenol crystals (BDH Chemicals Ltd,
Poole, UK), 150 ml of concentrated H
2
SO
4
(Fischer
Chemicals, UK), 75ml of fuming H
2
SO
4
(Fischer Chemicals,
UK)} and each mixture heated for 2 hours on water bath. All
samples (homemade brews, water, raw materials) and
blanks (n=3) were digested and diluted using the same
procedure.
2.7 Sample analysis
Samples were analyzed using UV-Visible spectroscopy.
The maximum holding time for NO
3
-N was 48 hours. The
concentration of the nutrients in solution was determined by
measuring the absorbance. Nitrate was analyzed at 493
nm, then applying the Beer-Lambert law the concentrations
of the solutions were obtained.
2.8 Sample analysis for nitrate in UV-visible
spectroscopy
In the analysis of nitrate 10 ml sample was pippeted out of
the stock solution into a beaker, followed by 5 ml of HCl and
2 ml of Zn/NaCl granular mixture added. This was allowed
to stand for 30 minutes with occassional stirring to form a
nitrite. The final mixture was filtered into a 100 ml standard
flask using what man No. 41 filter pap and diluted up to the
mark. Aliquots of stock solution containing 0.26-10.7 µg/l of
reduced nitrate were transferred in to series of 10 ml
standard flask. 1 ml of 0.5 % sulfanilic acid and 1 ml of 2
mol/l HCl solutions were added, shaken thoroughly for 5
minutes for the diazotization reaction to go to completion.
Followed by, 1 ml of 0.5 % methyl anthranilate and 2 ml of 2
M NaOH solution were added to form an azo dye and the
contents were diluted to 10 ml with water. After dilution to
10 ml with water, the absorbance of the red colored dye
was measured at 493 nm against the corresponding
reagent blank [8].
2.9 Data analysis
The quantitative relationship between absorbance and
concentration was first done by using a standard curve
(calibration curve). The concentration of each solution was
calculated based on the regression equation for data
analysis. P-values, t tests and ANOVA were used in data
analysis.
3.0 RESULTS AND DISCUSSION
3.1 Method validation
The parameters for method validation are specificity,
selectivity, precision, repeatability, intermediate precision,
reproducibility, accuracy, trueness, bias, linearity range,
limit of detection, limit of quantization, robustness and
ruggedness [2]. In this study the following were considered;
research apparatus and standard analytical reagents as
recommended by Association of Official Analytical
Chemists (AOAC) were used, standard solutions were
prepared using the standard methods, standard analytical
methods were applied, significant values were considered
using the (ANOVA test, t-test and p-values), instrumental
calibration was done before use, blanks, external
calibration graphs were prepared and international MCL
standards were also considered.
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3.2 Concentration of analytes in various homemade
brews, spirits, tap water and the raw materials used
3.2.1 Concentration of nitrate in various home -
made brews, spirits and tap water
The levels of nitrate-N in home - made brews/spirits and
water was determined using UV-visible spectroscopy and
the result obtained for various stations are presented in
Table 3.2.2 and Figure 3.2.2. From the Table 3.2.2, the
average levels of nitrates were generally high in homemade
brews/spirits. The highest levels of nitrate were obtained in
Muratina from Gikomba which had the concentration of
46.50 ± 5.42 mg/l. The lowest nitrate levels were obtained
in Muratina from Githurai with a concentration of 13.10 ±
1.06 mg/l. Busaa from Kibera, Kariobangi, Kawangware,
Gikomba, Githurai, Uthiru, Mathare and Kangemi had high
levels of nitrate ranging from 32.70 ± 0.46 mg/l from
Githurai to 44.10 ± 0.87 mg/l from Mathare. Busaa could
not be obtained in areas like Kiambu, Kilimani, Embu,
Siakago, Baricho, Runda, Sagana and Kibwezi were not
analyzed. The nitrate levels in the brews/spirits were
generally lower than the recommended levels of 50 mg/l for
water [7], Kenya Bureau Of Standards does not have
standards foe nitrates in alcoholic beverages. These levels
were also found to be lower than the maximum limit of 500
mg/l set by Alcohol Measures for Public Health Research
Alliance (AMPHORA) for alcohol [4]. The mean
concentration of nitrates in the home made brews and
spirits was calculated and the results were used to plot a
graph of concentration against home - made brew/spirit as
shown in the Figure 1. Kangara had the highest mean
concentration of NO
3
-N at 40.90 ± 1.05 mg/l, followed by
Busaa at 39.6 ±1.27 mg/l, Chang’aa had 37.70 ±1.79 mg/l.
Water showed no detectable levels of these ions. All the
brews indicated concentrations below the maximum
allowable limit set by Kenya Bureau of Standards [7] of 50
mg/. The levels are also higher than what is found in
uncontaminated water, but higher than the USEPA value of
10 mg/l. This could be due to the use of nitrogenous
fertilizers in growing raw materials, river waters in some
cases and also use of additives in the brewing process.
From Table 3.2.2 and Figure 3.2.2, the levels of nitrate in
the home made brews and spirits varied from 13.10 ±1.06
mg/l to 46.30 ± 1.40 mg/l, water did not contain any
detectable amounts of nitrates.
Table 3.2.2: Average concentrations (mg/l) of nitrate in
various homemade brews and tap water [Mean ± SD]
BREW
PLACE
BUSAA
[n = 24]
CHAN
G’
AA
[n = 33]
MITI
[n = 24]
MURATI
NA
[n = 33]
KIBERA
41.10
±1.07
37.30
± 1.67
40.00
± 0.16
42.70
±2. 58
KARIOBA
NGI
38.90
±0.25
35.90
± 1.65
37.10
± 5.10
37.60
± 1.42
KAWANG
WARE
40.00
± 1.07
38.30
± 2.01
38.40
±3.74
46.30
± 2.26
GIKOMBA
39.70
± 1.31
39.3
± 0.424
36.7
± 6.72
46.5
± 5.42
GITHURAI
32.70
± 0.464
33.40
± 3.37
40.30
± 1.95
13.10
± 1.06
UTHIRU
38.60
± 2.57
38.9
± 1.37
37.4
± 4.85
24.2
± 6.09
KANGEMI
41.20
±2.57
32.50
± 1.34
34.20
± 4.55
31.90
± 6.04
MATHARE
44.10
± 0.87
46.30
± 1.40
32.70
± 5.80
27.40±
1.25
KIAMBU
NA
35.40
± 2.17
NA
NA
KILIMANI
NA
38.50±
2.17
NA
NA
EMBU
NA
NA
NA
NA
SIAKAGO
NA
NA
NA
NA
BARICHO
NA
NA
NA
30.60
±0. 49
RUNDA
NA
NA
NA
NA
SAGANA
NA
38.30
± 2.08
NA
31.90±6.0
4
KIBWEZI
NA
NA
NA
31.2
±1.08
MEAN
39.55
± 1.27
37.66
± 1.79
37.12
± 4.11
33.03
± 4.09
P- values
0.05
0.06
0.05
0.048
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BREW
PLACE
WATER
[n = 0]
KANGA
RA
[n = 3]
KARUBU
[n = 12]
KIBERA
ND
NA
NA
KARIOBA
NGI
ND
NA
NA
KAWANG
WARE
ND
NA
NA
GIKOMBA
ND
NA
NA
GITHURAI
ND
NA
NA
UTHIRU
ND
NA
NA
KANGEMI
ND
NA
NA
MATHARE
ND
NA
NA
KIAMBU
ND
NA
NA
KILIMANI
ND
NA
NA
EMBU
ND
NA
31.80
± 3.19
SIAKAGO
ND
NA
25.60
± 1.30
BARICHO
ND
NA
NA
RUNDA
ND
40.9
± 1.06
NA
SAGANA
ND
NA
31.30
± 1.18
KIBWEZI
ND
NA
31.40
± 1.08
MEAN
ND
40.90
± 1.06
30.03
± 1.66
P- values
ND
0.00
0.045
NA = Not analyzed ND = Not detected
This trend was also observed in Chang’aa, Miti and
Muratina. The nitrate levels in Chang’aa ranged from 32.50
± 1.34 mg/l for Chang’aa from Kangemi to 46.30 ± 1.40
mg/l in the brew from Mathare, while for Miti the nitrate
levels ranged from 32.70 ± 5.80 mg/l in the brew from
Githurai to 40.30 ± 1.95 mg/l for the brew from Mathare.
The nitrate levels in Muratina ranged from 24.20 ± 6.09 mg/l
for the brew from Uthiru to 46.50 ± 5.42 mg/l for Muratina
from Kawangware. Kumi kumi and Kangara had only
station value analyzed hence they were not significant. Only
one value of these samples could be obtained since
handling these brews is illegal and one had to use a go
between to buy samples. Analyzed water had nitrate at non
detectable levels.
0
5
10
15
20
25
30
35
40
45
Busaa
Chang'aa
Miti
Muratina
Kumikumi
Water
Kangara
Karubu
Brews/spirits
Concentrations in mg/l
Figure 3.2.2: Mean concentrations (mg/l) of nitrate in
various analytes
The source of the nitrate ions in brews may not have been
water but could be from the use of untreated river water.
Karubu had the lowest overall average levels of nitrate at
30.0 ± 1.66 mg/l. Though Kangara registered the highest
average it is not significant since only one sample was
obtained. This also applies to Kumi kumi since samples
from only one station was considered in both cases. Some
brews such as Chang’aa, Busaa, Kumi kumi, Miti and
Muratina are prepared by the river bank to facilitate cooling.
Waters from these rivers are also sometimes used in
brewing process. Since they are generally polluted with
industrial and domestic wastes, the nutrients end up in the
brews. The other source of nitrate ions in the home made
brews may have been due to the use of untreated waters
from the slum areas. The mean levels of nitrates in various
brews were used to determine whether there was any
significant difference between the levels of nitrates in the
various brews using the t-test. The results were, for busaa
and chang’aa (t
cal
= 2.124, df = 55, t
cal
> t
tab
); for miti and
muratina (t
cal
= 7.668, df = 55, t
cal
> t
tab
); in the case of
muratina and karubu (t
cal
= 1.074, df = 43, t
cal
< t
tab
) and for
busaa and muratina (t
cal
= 1.209, df = 55, t
cal
< t
tab
) all at 95
% confidence interval. From this we can deduce that there
were significant differences in the nitrate levels between
busaa and chang’aa as well as in miti and muratina. But
there were no significant differences between the levels of
nitrate in muratina and karubu, as well as in busaa and
muratina. Cases where p > 0.05, meant there were
significant differences in the levels of nitrate in most of the
brews excepet tap water and kangara. The levels of nitrates
in the brews were generally high depending on the type of
brew and its source. From these values we can conclude
that the levels were also lower than the maximum
contamination levels of 50 mg/l [7]. This means that the
values seen in waters were in order and that water was not
the source of the high concentration of the nitrate registered
in the brews.
3.2.3 Concentrations of nitrate in various raw
materials
The levels of nitrates in the raw materials used to make the
brews were determined using UV-Visible spectroscopy and
the results are represented in Table 3.3.4. The mean levels
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of nitrate in raw materials used in the home made brews
and spirits are calculated and results represented in the
Figure below.
Table 3.2.4: Mean concentration of nitrate in various raw
materials [Mean ± SD]
Raw
materials
Nitrate (mg/kg)
[n = 18]
Maize
215.50 ± 18.31
Millet
326.20 ± 14.93
Sorghum
298.50 ± 10.44
Honey
263.50 ± 23.34
Jaggery
281.30 ± 14.99
Muratina fruit
272.40 ± 16.38
0
50
100
150
200
250
300
350
Maize Millet Sorghum Honey Jaggery Muratina
Raw materials used
Concentrations in mg/kg
Figure 3.2.4: Mean concentrations (mg/kg) of nitrate in raw
materials used in brewing the home made brews using UV-
Visible spectroscopy
Presented here in Table 3.2.4 and Figure 3.2.4, the nitrate
concentrations were generally high in the raw materials,
ranging from 215.50 ± 33.00 to 326.20 ± 75.00 mg/kg millet
had the highest concentration at 326.20 ± 75.00 mg/kg
followed by sorghum at 298.50 ± 27.50 mg/kg, and jaggery
at 281.30 ± 10.44 mg/kg, Maize had the lowest at 215.50 ±
33.00 mg/kg. The levels of nitrate in all materials were
found to be well above the maximum allowable limits of 5
mg/kg of nitrate set by the World Health Organization [15].
Hence the raw materials could have been a source for the
nutrient. This could be as a result of the soil levels where
the raw materials were grown. Figure 4.2 illustrates the
results obtained for; NO
3
-N in the raw materials which may
have contributed to the high concentration of this nutrient in
the home made brews and spirits. Nguyo (2006) [9]
explained that the high concentration of nitrate in river water
may have been due to the use of fertilizers in agriculture.
Honey used in the preparation of miti and muratina had a
mean level of 263.5 ± 23.34 mg/kg. All these levels were
higher than those observed in the home made brews. The
high concentrations of nitrates in the raw materials can be
attributed to the use of fertilizers, environmental pollution
and to some extent, the fermentation process in the
breaking down of raw materials where amino acids are
broken down and converted to nitrates. Raw materials may
not have been from the same region, where the brews were
being made. Hence the level of nitrates in the home made
brews and spirits may have been elevated by the high
levels of the nitrate ions in the raw materials. The mean
levels of nitrate-N in the study were much higher in all the
raw materials than the WHO recommended maximum
levels of 5 mg/kg of Nitrate-N [14]. The mean levels of
nitrates in various raw materials used were used to
determine whether there was any significant difference
between the levels of nitrates in the various raw materials
using the t-test. The results were; maize and millet (t
cal
=
13.92, t
cal
> t
tab
), for sorghum and honey (t
cal =
3.06, t
cal
> t
tab
)
and for jaggery and muratina (t
cal =
1.164, t
cal
> t
tab
) all at the
same degree of freedom (18) and confidence interval (95
%). From this we can deduce that there were significant
differences between the nitrates levels in maize, millet,
sorghum and honey. But the levels between jaggery and
muratina plant were not significant. Nitrate was detected in
all food groups except beverages and sugars and
preserves at mean concentrations above the Limit of
Detection (LOD) of 8 mg/kg.
3.3.5 Summary and Conclusion
The nitrate-N levels were generally low in the home made
brews/spirits and were found to be below the maximum
contamination levels of 50 mg/l set by the WHO, but higher
than the USEPA level of 10 mg/l for all homemade alcoholic
beverages analyzed. In the raw materials the levels were
also high. Water contained non detectable levels of nitrates.
This meant that the source of contamination for the
brews/spirits may not have been water, but either the use of
contaminated water, or any other additives placed in the
brew/spirit during the brewing process. The results also
verified that the levels of nitrate ions in the raw materials
used were generally higher than the MCL of 5 mg/kg and
the LOD of 8 mg/kg. These levels exceeded the maximum
levels recommended by the World Health Organization [15].
Many developed countries routinely monitor drinking water
quality [10], but this is not the case in developing countries.
Contaminant levels measured in the home made alcoholic
beverages more likely reflected the levels of nutrients in
water and the raw materials used in the brewing processes.
Acknowledgements
The author wishes to express his sincere gratitude to the
Chief chemist, Government chemist and the chief engineer,
engineer Maina, ministry of public works, and materials
branch for support during the entire research period when
there was inadequate funding. The good co-operation of
the deputy government chemist, Mrs. Okado and the Head
of Departments in both foods and water and the whole
government chemist staff is highly acknowledged. Special
thanks go to Professor Jane Murungi and Dr. Charles
Onindo of Kenyatta University for their supervision of the
thesis and helpful critical comments that resulted in the
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presentation of the data obtained. Thank you also for your
gifted editing, your hard work and your patience. I greatly
appreciate the typing assistance of my loving wife Mrs.
Rosalia Masime. Lastly, I thank the Teachers Service
Commission for granting me study leave with pay, my
lecturers, Dr. Ruth Wanjau, Professor Gerald Muthakia,
Dean (SPAS), Dr. Richard Musau, (Chairman, Chemistry
Department), Prof.Hudson Nyambaka and Dr. Koga
(Academic registrar) all of Kenyatta University, for their
support.
References
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House,
htt:www.checnet.org/healthhouse/chemicals,
September, 2007, Pgs 1-4.
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... [4] Nitrate levels in some beers have been found to be below the maximum residue level (MRL) limit for Europe [5] of 50 mg/L but above the recommended EPA drinking water standard of 10 mg/L. [4,17] A study in Germany found several batches of beer that had been dry-hopped with pellets or powder to be above 50 mg/L of nitrate [4] and Mitter and Cocuzza [5] and Kaltner et al. [16] both state that as hopping rate increases so does the nitrate level in beer. Some literature indicates that there is a nearly 100% transfer rate of nitrate from hop material to wort and beer. ...
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The process of analytical method validation should demonstrate that the method is fit for its purpose. The validation should follow a plan that includes the scope of the method, the method performance characteristics and acceptance limits.Parameters usually examined in the validation process are limits of detection and quantitation, accuracy, precision, selectivity/specificity, linearity, range and ruggedness. A validation report should be generated with all experimental conditions and the complete statistics. If standard methods are used, it should be verified that the scope of the method and validation data, for example, sample matrix, linearity, range and detection limits comply with the laboratory’s analyses requirements, otherwise the validation of the standard method should be repeated using the laboratory’s own criteria. The present article gives a brief review on analytical method validation.
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―Nitrite, Nitrate‖ CHEC's Health House
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