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ruined如何用核磁确定混合物中各组分的百分含量

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2021-01-20 20:38
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2021年1月20日发(作者:8185)
如何用核磁确定混合物中各组分的百分含量



1HNMR
确定混合物中各组分的相对百分含量是比较方便的
.
1.
要知道原料
,
产物
,
溶剂
,
杂质的结构和分子 量
.
2.
正确辨认原料
,
产物
,
溶剂
,
杂质的特征
NMR
信号
,
正确积分
.
3.
每个化合物选定一个信号
,
分别求出一个
H
的面积
.
它们 之间的比值就是摩尔比
.
换算成重量
比就更容易了
.
如果原料和产 物中都有甲基
,
那就用二者的
CH3
信号积分值比
,
即二者 的摩尔比
.
4.
残留溶剂比如醋酸利用
CH3

1HNM R
信号
.
5.
可以把三个成分作为
100%(
假定样品中 几乎没有水分和无机成分
),
也可以计算
%.
方法是比较灵活的
.
特殊情况的问题再叙
.
此法比较方便快捷,误差通常在可接受的范围,当然没有色谱法精度高。


1HNMR
不但可以测定混合物中成分的相对含量
,
也可以通过加入合适的内标测定绝 对含量
,
有很多文献
.

有个术语叫
Quantitative NMR(QNMR).

国外有
1HNMR
定量测定天然混合物的论文和综述文章
.

比如
:

Based
on
a
brief
revision
of
what
constitutes
state-of-the-art

experimental
conditions
references and covers the literature since 1982 with emphasis on natural products. It provides an
overview
of
the
background
and
applications
of
qHNMR
in
natural
products
research,
new
methods
such
as
decoupling
and
hyphenation,
and
analytical
potential
and
limitations,
and
compiles information on reference materials used for and studied by qHNMR. The dual status of
natural products, being single chemical entities and valuable biologically active agents that need
to
be
purified
from
complex
matrixes,
results
in
an
increased
analytical
demand
when
testing
their
deviation
from
the
singleton
composition
ideal.
The
outcome
and
versatility
of
reported
applications lead to the conclusion that qHNMR is currently the principal analytical method to
meet this demand. Considering both 1D and 2D 1H NMR experiments, qHNMR has proved to be
highly
suitable
for
the
simultaneous
selective
recognition
and
quantitative
determination
of
metabolites in complex biological matrixes. This is manifested by the prior publication of over 80
reports
on
applications
involving
the
quantitation
of
single
natural
products
in
plant
extracts,
dietary materials, and materials representing different metabolic stages of (micro)organisms. In
summary, qHNMR has great potential as an analytical tool in both the discovery of new bioactive
natural products and the field of metabolome analysis.


我和同事发表的
1HNM R
法定量测定替米考星的含量的论文摘要
(
分析测试学报
)


-----------------------------------------
Historical Background of qNMR. Quantitative NMR (qNMR) is almost as old as NMR itself. Early
reports
regarding
the
achievable
precision
of
quantitation
are
inconsistent,
and
some
of
them
even tended to deny NMR a role as a precision method by estimating the error to be in the 10%
range.
Interestingly,
and
with
notable
exceptions,textbook
literature
often
does
not
emphasize
the
quantitative
aspects
of
NMR
and,
thus,
does
not
motivate
educators
and
researchers
to
consider
qNMR
as
an
analytical
tool.
This
stands
in
contrast
to
the
authors'
recent
personal
discussions
with
experienced
NMR
spectroscopists,
as
well
as
to
the
tenor
of
the
publications
cited
in
this
review,
according
to
which
the
quantitative
power
of
1H
NMR
and
its
broad
applications
are
greatly
underestimated.
Moreover,
recent
developments
in
the
field
have
provided evidence that NMR can be developed as a precise quantitative tool and, in time, can
even be a primary analytical method.

As can be seen from Figure 1, there is
a steadily increasing interest in qNMR over the past 40
years,
as
measured
by
the
number
of
publications
in
the
field
(Chemical
Abstracts).
However,
taking
into
account
the
overall
rapid
increase
of
publications
in
science,
and
especially
when
considering the statistics for natural products related qNMR (solid bars in Figure 1), there seems
to
be
almost
no
gain
in
interest
in
the
past
15
years,
a
period
that
has
been
exceptionally
productive
in
terms
of
NMR
hardware
development.
It
must
be
noted,
however,
that
the
metabolomic
studies
mentioned
below, which
often
involve
(semi-)
quantitative NMR
analysis,
are
not
included
in
this
statistical
picture,
because
the
necessary
qNMR
keywords
cannot
be
searched successfully since they are not included in the database entries of the corresponding
publications.
The
importance
of
the
qNMR
methodology
in
this
recently
emerging
area
of
research,
however,
indicates
the
rising
impact
of
qNMR
methodology
on
natural
products
research in general.


----------- ---------------------------------------------
Literature
Background
of
qNMR.
Because
qNMR
has
been
living
in
the
shadow
of
the
multifaceted
and
multidimensional
qualitative
NMR
used
in
structure
analysis,
neither
has
it
been used as widely and routinely nor is a recent and comprehensive overview of the literature
available.
However,
Szantay
and
Evilia
have
reviewed
systematically
the
general
experimental
factors
known
to
interfere
with
quantitative
determinations
in
NMR.
Their
articles
cover
relaxation, digitization, and instrumental parameters and provide valuable sources of information
independent
from
the
observed
nuclei.
Certainly
noteworthy,
while
exclusively
dealing
with
analyses of drugs and pharmaceuticals, is the extensive qHNMR work by Turczan and co-workers
at
the
FDA,
which
to
our
best
knowledge
has
not
been
summarized
in
a
review
format.
Their
experience shows that typical errors fall in the 0.5-2% range, and their reports serve as a valuable
resource when it comes to the selection of qNMR reference standards (see below). The essential
lack of reports describing the application of qHNMR in natural product research is confirmed in a
1989
1H/13C
NMR
review
by
Pieters
and
Vlietinck,
who
concluded
that,
despite
the
great
potential of qNMR, suitability has to be established for each individual case. The excellent review
series focused on 1H NMR by Rackham that begun in 1975, unfortunately, has been discontinued,
leaving almost all of high-field qHNMR uncovered. The present review seeks to fill this gap and to
provide a comprehensive survey of the qHNMR literature by discussing recent and forthcoming
technological innovations, while concentrating on the applications of qHNMR to complex samples
(mixtures) such as materials that are obtained from natural sources. Because the second most
studied
organic
NMR
nucleus
(13C)
is
considerably
less
sensitive
(1.6%
of 1H
sensitivity
for
an

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